Note: Descriptions are shown in the official language in which they were submitted.
~ . . -21 70624
DISTRIBUTION AUTOMATION SYSTEM USING MEDIUM AND LOW
VOLTAGE DISTRIBUTION POWER LINES AS TWO-WAY DATA
TRANSMISSION MEDIA
D~CRIPTION
S The present invention refers to a system for the
remote control of the electricity distribution network
and the telereading of the electricity, gas, water and
other services meters of the customers connected to the
same network.
More specifically the present invention refers to a
system which uses centralised and distributed
intelligence to manage the information and carrier
currents at relatively high frequencies over the wires of
the electricity networks to transmit the information.
From document US 3,942,170 Ian A. White, assigned to
Westinghouse Electric Corporation, entitled Distribution
Network Powerline Carrier Communication System, a system
is known making use of high frequency carrier currents to
transmit messages over medium voltage and low voltage
electricity distribution networks, in particular messages
relating to the telereading of electricity meters
connected to said low voltage network at customers'
premises. A station is connected to the medium voltage
network to send interrogation messages thereon and
receive response messages transmitted thereon and coming
from said electricity meters. Repeaters receive said
interrogation messages on the medium voltage network and
retransmit them on the low voltage network. The
electricity meters receive the interrogation messages
transmitted on the low voltage network and send response
messages thereon to said station. The repeaters include
a capacitive coupling for injecting the messages on the
medium voltage network.
From the document "Le système de téleconduite du
reseau MT d'ENEL/' by R. Gargiuli, R. Tonon, D. Vannucci
and L. Menozzi, published in "Revue Général de
l'Electricité/' of September 1993, a system is also known
AMENDED SHEET
2~ 70624
for the remote control of the Medium Voltage networks
that also allows the telecontrol of end users of
electricity. This system also allows a centralised
control in a modular way. The architecture of the system
is disclosed in a general way mentioning the use of
computers and peripherals for the handling of data
concerning the arrangement and operation of the power
distribution network.
The carrier currents system is implemented according
to a method, which, unlike the traditional one, does not-
utilise high frequency traps and by passes, at the
network nodes. This method allows the use of the power
distribution network without the expensive changes
required by the traditional solution.
This result is obtained by forecasting the messages
over the Medium Voltage (MV) and the Low Voltage (LV)
radial networks as they are configured for the
distribution of the electricity and by properly
addressing the various substations and the customer
meters.
Because the MV and LV electricity network
configuration is subject to change as a consequence of
intentionally made switching operations or as a
consequence of automatic tripping of switchgears
following a fault, the method of properly addressing and
routing the messages to their final destinations requires
that the state of the network is very frequently updated.
This function is performed by the system subject of
this invention and the updating of the state of the
network, a very important` information in itself, has to
be seen as an added value for the system.
According to the present invention, the .system
mentioned above, can provide, one by one or in an
integrated way, the following functions:
- Supervision of the High Voltage Network and remote
control of the Primary Substations;
AMENDE~ SHEET
21 70624
-2A-
- Supervision of the Medium Voltage Network and
remote control of the secondary substations;
- Remote reading of the meters and automation of
other commercial functions for the MV and LV customers;
These, and other characteristics, aims and.advantages of
the present invention will be more clearly seen from the
following detailed description, to be considered in
conjunction with the enclosed drawings. The actual scope
of the invention is stated in the characterising clause
of the attached claims.
As regards the drawings:
Figure 1 shows the architecture of the system
according to the present invention;
figure 2 is a table giving the meaning of the
symbols used in figure 1 and in the subsequent figures;
figure 3 shows a diagram for routing the messages;
figure 4 shows a diagram of the high frequency
coupling device for the injection/pickup of carrier-
current signals on the MV network;
figure 5 shows a the architecture of the ACP
apparatus;
figure 6 shows the architecture of the ACS
apparatus;
figure 7 shows the architecture of the Remote
Terminal Unit (UPT);
figure 8 shows the architecture of the Peripheral
Electronic Unit (UEP) which is installed inside the
metering apparatus for domestic LV users;
figure 9 shows the Multifunction Portable Terminal
(TEM);
figure 10 shows the block diagram of the
Al~ENDED SHE~T
~ wog5/os473 : ,~ 2 1 70 624 PCT~194/00158
Multifunction Portable Terminal (TEM);
figure 11 shows a LV network diagram as it appears
on screen in an STM graphic workstation;
figure 12 shows the structure of the message on
the MV network according to the used protocol;
figure 13 shows an example of the "store and
forward" procedure on a LV line;
figure 14 shows a map of the remote controlled
HV/MV substations within a certain distribution zone;
figure 15 shows the topological diagram of a MV
distribution network;
figure 16 shows the diagram of a MV feeder;
figure 17 shows the sub-diagram of a MV feeder
section;
figure 18 shows a typical HV/MV Substation
Diagram;
figure 19 shows a diagram of a secondary
substation with one bus-bar;
figure 20 shows a diagram of a secondary
substation with three bus-bars;
figures 21 and 21bis show an example of the
automatic sectionalizing procedure on an overhead
MV feeder;
figure 22 shows an example of the automatic
sectionalizing procedure on a MV underground ~eeder;
figure 23 shows a diagram of the pulse generator
device installed inside the metering apparatus;
figure 24 shows the metering apparatus and the
electronic units required by the system for the various
categories of users defined as a function of their
subscribed power demand;
figure 25 and figure 26 show two types of electric
metering apparatus;
figures 27a and 27b show the insertion of the
electronic unit into the metering apparatus in the case
of an individual installation and in the case of the
installation over a centralized board;
;~ ~
WO 95/09473 ~;~p, ~r ~ 2 1 7 0~2 4 PCTnlg4/00158 ~
~ 4
figure 28 shows the structure of centralized
board for residential low voltage customers;
figures 29, 30, 31 show different types of
metering apparatus;
figure 32 shows the connection of a metering
apparatus through current transformers for an LV
customer;
figure 33 shows an SF6 insulated apparatus
installed at the MV customer connection and containing
current and voltage transformers, an earthing device
and equipped with the carrier current coupling device;
1. GENERAL SYSTEM ARCHITECTURE
System architecture as shown in fig. 1 is divided
into the following subsystems: .
STU-x for management of the HV (high voltage)
network and the Primary Substations in a certain
territorial unit (District).
STM for management of: MV (Medium Voltage)
network, secondary substations and users in each
territorial sub-unit (Zone) into which the territory
controlled by STU-x is divided;
STU-x is at the highest level in the hierarchy and
is capable of managing up to 200 Primary Substations
(HV/MV transformation substations): therefore it can
supervise and control an HV network of notable
proportions.
It can interface on the one hand with other STU-x
systems and/or with remote Host Computers, by means of
packet switching geographical networks, and on the
other hand with one or more STM systems from the
component territorial sub-units, by dedicated Point-to-
point channels.
If one or more zones are not provided with STM it
is possible for them to be provided with a Peripheral
Work Station (SOP) allowing the operator, in the local
control center, to work on the network he is in charge
of.
~ W095/09473 '~. i`. 21 70624 PCTAT~4/00158
~4'`''
- 5 -
STM, as well as giving remote control of the MV
network, also provides for all functions connected with
customer service automation in the Zone, and it is
available in three sizes, according to the dimensions
of the network to be managed:
- A-type STM for small MV networks;
- B-type STM for medium sized MV networks;
- C-type STM for large MV networks;
Both the STU-x and STM subsystems are organized on
Ethernet type Local Area Networks; the vital components
of each system, including the computer, are doubled,
and there are special procedures to switch from the
faulty component to the healthy one.
The FRONT-END Computers (FEC) use the same
Hardware base, but can adopt different types of
protocol and manage communication with the field
autonomously.
If the territorial sub-unit (Zone) is provided
with STM, the information relating to the Zonal Primary
Substations is acquired directly by the FECs of STU-x
(Fig.l).
The information from the Secondary Substations is
acquired by the FECs of STM. This information comes
from the Primary Substation Apparatus (ACP), and can be
divided into two main categories:
a) Information relating to the subsystem for the
automation of the MV network, coming from the Remote
Terminal Units (UPT) in the secondary substations;
b) Information relating to the subsystem for
Customer Service Automation, coming directly from the
metering devices for MV users, or from the Secondary
Substation apparatus (ACS) for LV users.
The work stations (Fig. 1) installed at District
(SOD) and Zone (SOP) level are practically identical to
each other, and are high definition graphic stations.
From figure 1 it is evident that the single sub-
systems can be used separately, according to the
WO95/09473 ~ 2 1 7 0 62 4 PCT~194/00158 ~
-- 6
territorial organization of the electric company and
according to the applications required; the following
is therefore possible:
* remote control of the HV network over a vast
territory using the STU-x alone;
* remote control of the Primary substations and
the MV network over a more restricted territory using
the STM alone;
* customer service automation using STM alone and
the software strictly necessary for this operation;
* implementation of all the functions given in the
above points, by integration of a STU-x with a series
of STMs.
The telecommunications sub-svstem
15Communication between the Primary Substations and
the Control Center is carried out through st~n~rd
vectors, and so it is possible to use radio links,
dedicated telephone lines, carrier-current signalling
on HV lines, etc.; in this wav each Zone. is connected
20to its own Primary substation.
Connection of each Primary Substation to its own
secondary substations and connection between the LV
meters and the secondary substation by which they are
fed, is carried out by a line carrier transmission
25system, on the same MV and LV distribution networks.
Application of the line carrier transmission
system to the MV and LV networks requires some
technical solutions that make it differ strongly from
the classical method used on HV lines.
30In effect, due to the extremely high number of
nodes in the MV and LV networks, make practically
impossible the adoption of high frequencies traps and
by-passes, but the HF signal is injected into each MV
bus-bar in a Primary Substation and onto every LV bus-
35bar in each secondary substation, so that the signal
spreads through the whole of the electrical network fed
by these bars.
~ W095/09473 ~ i f =., 21 7 ~ 62~ PCT~T94/OOlS8
~ 7 -
This solutions means that the impedance of the
transmission circuit cannot be ~atched easily to the
continually varying impedance of the communication
support. The decay in performance that results from
this lack of matching is prevented by the ability of
the intermediate stations to re-transmit the messages,
using a "Store and Forward" procedure.
The non-existence of High Frequency by-pass on the
switching elements means that the interruption of a
feeder caused by a fault produces a break in the
communication link at that point in the system. The
solution to this problem, which is briefly described in
the following paragraphs, consists in providing the
Remote Terminal Units (UPT) with a certain amount of
autonomy, so that they implementing on them a logic
that allows automatic re-closure of the switches in the
substations to be reenergized, as soon as the faulty
section has been isolated.
For the same reasons, any variation in network
connection produces a change in the configuration of
the Telecommunications System which, in order to route
messages, has to refer to a real time updated Data
Base, containing the status of electrical connections
in the network.
It must be noted that the above does not form what
could be defined a "negative characteristic". It is,
in fact, a novel and innovative form of use of what was
considered a negative aspect, that is to say a fault in
carrier-current signalling systems when considered in
general.
As a matter of fact, up to now the line carrier
systems, which are well known from a conceptual and
operative point of view and also on a commercial
hardware level, were designed to operate by "imitating"
the "on-the-air" radio communication systems.
As will be seen from the following, one of the
main aspects of the present invention makes
W095/09473 ~ L 2 1 70624 PCTnTg4/00158 ~
advantageous use of what was up to now considered a
limitation in line carrier transmission systems.
With reference to figure 3, routing of the various
messages starting from the STM su~system, according to
the present invention, will now be described in greater
detail.
The subsystem (STM) for distri~ution automation in
one of the territorial sub-units mentioned above is
managed by a control center (100). This center, by
means of the FRONT-END computers (101) communicates
using dedicated multi-point lines with the HV/MV
substations in the territory covered.
Once one of these installations is reached, the
message is delivered to the ACP apparatus (102), from
which the line carrier system, according to the present
invention, departs.
The ACP (102) has a series of independent output
channels which, by suitable coupling devices (103),
allow injection/pick-up of the carrier-current signal
on each medium voltage bus-bar (104) in the substation.
A series of lines departs from each Primary
Substation MV bus-bar, with the interposition of MV
circuit-breaker (105), and each of these lines feeds a
series of MV/LV substations (106) connected in cascade.
Once one of these substations has been reached,
the signal is picked up by a coupler (107) and sent to
the ACS apparatus (108) or sent directly to a medium
voltage customer metering apparatus (109) if the
substation supplies a user of this kind.
The ACS (108) connects with the low voltage (LV)
supply bus-bar by a capacitative coupler that allows
the messages to reach the low voltage meters (111)
installed in the user premises. In certain cases
(remote controlled MV/LV substations) the ACS is
connected to the UPT apparatus (110), which allows
remote signals to be sent and remote commands destined
for the switches in that secondary substation, to be
WO95/09473 ~ 0 6 2 4 PCTAT94/00158
performed.
Naturally, as underlined above, in order to route
the signals correctly it is necessary to know instant
by instant the electrical connection status of the
network, that is to say the open or closed state of all
the switching devices situated in the various
substations, both Primary and secondary.
The type of modulation used is narrow-band (FSK),
and the transmission frequencies are the following:
approx. 72 kHz for the MV network
approx. 82 kHz for the LV network
both within the range of 9-95 kHz, assigned by
CENELEC to electric utilities.
The modem used, which is of the single-chip type,
is the same for both the MV and the LV network.
The frequencies indicated above do not pass beyond
the distribution transformers (both HV/MV and MV/LV)
and, generally speaking, do not pass the open switches.
As a consequence of this, and of the fact that the
EMEL MV and LV networks are radially operated, the
signals are injected onto the secondary winding of each
HV/MV and MV/LV transformer. There are, therefore, the
same number of independent transmission routes as there
are HV/MV transformers on the MV network, and as there
are MV/LV transformers on the LV network.
The chosen frequencies do not penetrate into the
power factor correction capacitor banks present in the
plants, and these therefore have no effect on signal
attenuation.
Signal coupling is capacitive, as this is more
effective than the corresponding inductive solution.
With regard to the propagation mode, the phase-
phase mode is used in the MV network, and the phase-
neutral mode is used in the LV network.
The following are therefore used:
- a capacitive phase-phase coupling device on the
MV network (figure 4)
Wo95/Os473 - 2 1 7 0 ~24 PCT~1~4/00158 ~
-- 10 --
- a capacitive phase-neutral coupling device on
the LV network.
The solution chosen for the MV network does not
influence operation of the directional earth
protections in the HV/MV substations, and m;nim; zes
crosstalk at open switches.
From the construction point of view, the MV
coupling device is confined inside a small metal oil
filled box, and is connected to the line by means of
10 air or gas insulated bushings, for installation on an
air or gas insulated cell, respectively.
Transmission power is rather low (~lW) both on the
MV and on the LV network.
As signal attenuation, noise level and coupling
15 impedance may vary greatly over a period of time due to
variations in the electrical loads and configuration of
the network, the "store and forward" function has been
provided in the peripheral units to re-transmit the
signals and reach the most distant points even under
20 the hardest conditions.
Furthermore, with reference to the LV networks,
which are the ones most frequently influenced by
electrical loads, the used procedures are tolerant with
delays of several hours in the transmission of signals;
25 this, for customer ser~ice automation, makes it
possible to avoid transmission during the least
favourable hours of the day (hours of m~; mllr load).
The transmission rates are the following:
1200 bit/sec. on the MV network
600 bit/sec. on the LV network.
These rates, even when taking into account the
"store and forward" procedure and the re-transmission
of incorrect messages, can ensure the following
performance:
- acquisition of signals from 100 remote
controlled MV/LV substations, in less than one minute;
- acquisition of consumption data from 10,000
WO95/09473 ~ ` 2 1 7 0 6 2 4 PCTA1~4/00158
meters, in less than four hours.
These values correspond to the average number of
M~/LV transformer stations and MV and LV users,
supplied by a Primary Substation, so the performance
indicated above ensures good performances.
In addition to the processing resources at the
control center, the system, according to the present
i~vention, also uses the peripheral apparatus described
below.
ACP
The ACP, or Primary Substation Apparatus (figure
5), situated in each HV/MV substation, is the
communication interface between the FEC installed in
the control center and the peripheral apparatus
connected to the Medium Voltage network (ACS, UEPM,
UPT).
The hardware architecture of the apparatus is
modular and uses a System bus to interconnect cards,
thus allowing sizing that is aimed at the specific
needs of each site.
The fundamental blocks of ACP are:
a) Processing unit (CPU, memory and accessory
circuits):
b) Telegraphic modem to FECS;
c) Interface to the Portable terminal;
d) MV network RX/TX modules;
e) Synchronization unit with MV zero crossing.
The ACP can connect with:
- FEC Apparatus through a bi-directional full-
duplex communications channel with st~n~Ard HDLC-NRM
protocol in multipoint slave mode;
- ACS apparatus by means of a certain number of
channels, each one of which is coupled to a Primary
Substation MV bus-bar by means of capacitive coupler.
Each channel is bi-directional half-duplex and can
manage the traffic in parallel with the others on the
various substation bus-bars. The protocol is
W095/09473 ~ 2 1 7 0 62 4 PCT ~ ~/00158
- 12 -
specialized multipoint HDLC-MT type, with the ACP
acting as Master. All the messages sent on the MV bus-
bars are synchronized with the zero crossing of the
alternate current at 50 Hz, that is to say there is a
positive zero-crossing indicator supplying the start
of the message.
- Portable terminal, by means of an asynchronous
serial interface with optical connection.
The ACP node is only assigned tasks connected with
communication, and in particular the following
functions:
- Management of HDLC-NRM slave connection protocol
to and from FECS;
- Management of HDLC-MT master connection protocol
to and from the peripheral apparatus in the secondary
substations (MV network);
- Management of synchronism for transmission of
messages at zero-crossing;
- Management of standard IS0/IEC connection
protocol to and from the non-resident portable
terminal;
- Management of routing for messages from FECS
towards a specific section of MV bus-bar according to
the peripheral to which it is destined;
- Management of priority levels both for
centrifugal and centripetal messages;
- Determination of the relay stations for each end
node;
- Determination of the level of signal received by
MV nodes and communication of the latter to the control
center;
- Diagnosis of inconsistencies and incongruences
in the peripheral devices;
- Remote loading of routing tables by the central
system;
- Management of data structures for diagnostics
and communication statistics;
2 1 7 0 6 2 ~
~ W095/09473 -- ~ PCTAT94/00158
-
- 13 -
ACS
The ACS, or Secondary Substation Apparatus (fig.
6), installed in the MV/LV substations, is a slave node
of the communications network on the medium voltage
lines and the Master node for the Low Voltage
communications network.
The Hardware is characterized by a high level of
integration with sharing of functions between the
various units, which takes into consideration not only
functional aspects but also industrialization aspects.
The functional blocks making up the ACS are the
following (fig. 6):
a) CPU and Power-fail management circuits;
b) Static RAM memory;
c) FLASH_EPROM memory for the application programs
code;
d) EPROM memory for Bootstrap programs and those
for management of portable terminal loading;
e) EEPROM memory for semi-permanent ACS data
(address, routing tables, etc.);
f) A/D converter for measurement of network
voltage;
g) Real Time Clock for management of time/date
with Back-up capacitor to guarantee operation of the
clock for 48 hours in the absence of power supply;
h) MV Multiplex to share the MV transceiver with
the UPT;
i) LV Multiplex to share the single serial channel
with the three LV transceivers, each one connected to
one phase and neutral;
j) MV transceiver;
k) LV transceiver;
l) LV couplers;
m) Dual-input power supply (220 V AC - T phase,
24V DC);
n) Block for processing of the zero crossing on
the three phases of the LV network, starting from the
W095/09473 ~ 2 1 7 0 6`24 PCTnT~4/OOlS8
- 14 -
signal for the T phase of the power supply.
The ACS can connect with:
- The ACP by means of the MV network, to which
both are connected by a capacitative coupler;
communication can be direct or through a number of ACS
repeater units.
- The Electronic units in the LV metering
groups (UE-BT) through the LV network - the LV
transceivers, one for each phase, can only ~e used
separately according to the phase involved;
- The Portable Terminal by means of an
asynchronous serial interface with optical coupling of
the same kind as that used by the ACP.
- The UPT or Remote Terminal Unit by a
lS standard RS232 interface; this connection has the sole
aim of allowing the UPT to use the MV transceiver for
communication with the ACP.
The ACS node is assigned tasks connected with
communication, and in particular the following
functions:
- Management of HDLC-MT slave connection protocol
to and from the ACP;
- Management of synchronism for transmission of
messages at zero-crossing;
- Management of communications protocols on the LV
network, in order to guarantee communication with the
UE-BT in all the types of dialogue foreseen;
- Management of standard ISO/IEC connection
protocol to and from the non-resident portable
terminal;
- Management of dialogue, on RS232 interface, with
the UPT apparatus;
- Determination of the relay stations for each end
node;
- Cyclic verification of the connection status of
the LV network, with notification of any anomalies to
the center;
~ W095/09473 =~ 21 70624 PCTAT~4/00158
- 15 -
- Acquisition of newly installed UE-BT;
- Remote loading of routing tables processed by
the central system;
- Management of data structures for LV diagnostics
,~ and communïcation statistics;
- Direction of User Terminal updates in the basic
cycle;
- Direction of User Terminal updates in the daily
cycle;
- Daily control of the dependent UEs and
collection of consumption;
- Management of non-periodic remote management
operations re~uested by the center;
UPT
The UPT or Remote Terminal Unit (fig. 7) is only
present in remote controlled secondary substations,
where, in addition to its normal functions of actuating
commands and transmitting remote signals, it is also
used to apply a series of automatic rules that allow a
faulty section of MV line to be identified and
sectionalized.
The Hardware is characterized by a high level of
integration, the functions being shared between the
various units like for the ACS apparatus.
The architecture can be divided into two main
sections, each one managed by a separate bus: the
processing section and the section for interface with
the field.
In greater detail, the functional blocks forming
the UPT are the following (fig. 8):
a) CPU and support circuits;
b) Static RAM memory;
c) FLASH_EPROM memory for the application programs;
d) EPROM memory for Bootstrap programs and those
for management of portable terminal loading;
e) EEPROM memory for semi-permanent ACS data
(address, routing tables, etc.);
WO9~/09473 ~ 2 1 7 0 6 2 4 PCT ~ 4/OOlS8
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f) Real Time Clock for management of timing;
g) System Watch Dog (WD);
h) Controller for 2 serial channels (connection
with ACS and with the portable terminal);
i) RS232 interface for connection with ACS;
j) RS232 interface and opto-electrical converter
for connection with the Portable Terminal;
k) Connection interface between the bus of the
processing unit and the bus for dialogue with the
field;
l) Signals interface;
m) Commands interface;
n) Power supply (24V DC);
The UPT can connect with:
- The ACP by means of the MV network to which
both are connected by a capacitative coupler;
communication can be direct or through a number of ACS
repeater units.
- The ACS by means of a standard RS232
interface; this connection has the sole aim of allowing
the UPT to use the MV transceiver for communication
with the ACP.
- Another UPT by means of the MV network
during identification of the faulty section of
underground lines (with RG).
- The Portable Terminal by means of an
asynchronous serial interface with optical coupling
like that used by the ACP and by the ACS.
The main functions carried out by the UPT are the
following:
- Remote control of the installation
(actuation of commands on switches, production of
status information, pre-processing and tr~n~ sion of
elementary signals from the field, etc.);
- Identification of Faulty Section (group of
rules and procedures which are applied automatically by
the apparatus to allow identification of the faulty
~ W095/09473 ~ 21 70624 PCTAT94/00158
- 17 -
sections of MV line);
- dialogue with the center by means of the ACS
in HDLC-MT protocol;
- HW/SW diagnosis of the apparatus and service
functions through the portable terminal.
UEP
The UEP or Peripheral Electronic Unit associated
to the meter for each MV and/or LV user, performs a
series of communication and data processing functions.
The functions and different types of electronic
unit will be illustrated in the following; the
block diagram of a UEP for single-phase LV user is
given as an illustration (fig. 8).
The Hardware architecture shows the following
basic bloc~s:
a) Processing Unit (CPU, memory and accessory
circuits);
b) Opto-electronic transducer connected to the
impulse emitting device housed inside the new power
meterS;
c) Tripping device for the thermo-magnetic switch;
d) Transceiver coupled to the LV line upstream of
the meter;
e) Liquid Crystal display for user;
f) Power supply connected to the LV line upstream
of the meter.
The UEP can connect with the following:
- The ACS by means of the LV network and HDLC-
BT protocol;
- Another UEP, again by means of the LV
network and HDLC-BT protocol;
- A user terminal associated to the UEP by
means of the user's own LV power supply plant;
- - A Portable Terminal by means of the LV
networ~ and HDLC-BT protocol.
Within the architecture described above, the UEP
performs the following functions:
W095/09473 ~ I ~ 2 1 7 0 624 PCTAT~4/00158
- 18 -
- Basic timing management with clock/calendar
functions;
- Management of tariff programs capable of
allowing different rates according to the time of day,
the season, the power used and of mobile peak load;
- Count of the l'quanta" of energy measured by
the Ferraris meter;
- Processing of data for the quality of the
service and any attempts at fraud;
- Management of procedures for initialization
of the operating parameters;
- Management of procedures for bi-directional
dialogue with other UEPs, with the ACS, with the
Multiple function Porta~le Terminal;
- Management of procedures for dialogue with
its own user terminal;
- Management of commands for tripping the
thermo-magnetic circuit-breaker;
- Management of procedures for data
displaying;
- Management of procedures for self-diagnosis
and safeguard of processed data;
User Terminal
The communications function also comprises any
dialogue with an optional electronic device that the
- user may install in his home, and which has the
function of displaying information, sent directly by
the Electrical Company, relating to energy consumption
and, in the more sophisticated version, of performing
load optimization activities.
The procedures for dialogue between each UEP and
its user terminal will be ~ined later in the present
text.
The System also provides a Multi-function Portable
Terminal (TEM), using which it is possible to connect
to all the peripheral apparatus mentioned above.
The TEM (figures 9 and 10) is made up of a metal
~ W095/09473 ~ 2 1 7 0 6 2 4 pCT~1~4/00158
- 19 -
case containing on its inside:
- Personal Computer of a Note-book type;
- l transceiver for the MV network;
- 3 transceivers for the LV network;
- l asynchronous serial interface with optical
coupler;
- l X.28 interface for telephone lines;
- l set of connection cables.
The personal computer is provided with suitable
software packages for management of all types of
protocol used by the System according to the present
invention. Interactive procedures developed ad hoc
allow the TEM to perform the following activities:
l) Programming and testing of the following
apparatus: ACP, ACS, UPT and electronic units
associated to the Medium Voltage power meters (UEPM) by
means of asynchronous serial connection with optical
coupler;
2) Progr~mm;ng and testing of the electronic units
of Low Voltage meters by means of the modems for the LV
network;
3) Dialogue according to the protocol on the MV
network with the apparatus indicated in point l, by
means of MV modem;
4) Dialogue according to the protocol on the LV
networ~ with the apparatus indicated in point 2, by
means of LV modems;
5) Dialogue with ACP and with all the nodes in the
network (both MV and LV) that are hierarchic dependent
on it, in a manner similar to that used between the
FECS apparatus and the Control Center;
6) Dialogue on X.28 network with the Central
System by means of a suitable interface.
PROTOCOL
The communications protocol adopted is derived
from the standard HDLC ~NRM), to which the
modifications necessary for the following have been
w095/og473 2 1 7 d 6 24 PCT~194/00158
- 20 -
introduced:
- addressing an extremely high number of "End-
nodes";
- managing the "Store and Forward" process.
The dialogue is managed autonomously by the ACPs
on the MV network and by the ACSs on the LV network,
and takes place in parallel on each independent
communication island. More specifically, it is
possible to identify:
- independent communication islands on the MV
network, made up of all the lines connected to the same
LV bus-bar in the Primary Substation. On each of these
islands the ACP manages dialogue with the ACSs and with
the UEPs of MV users in parallel; in particular the
ACSs in each island are interrogated cyclically to
check their connection status.
- independent communication islands on the LV
network made up of all the "Sections" connected to the
same LV bus-bar in the secondary substation. On each
of these, in parallel, the ACS interrogates the UEPs
cyclically to check their connection status.
The addressing methods will now be illustrated.
Above all, as regards remote management of users,
it is well to explain the method of addressing the LV
metering devices.
While the MV network is represented in a classical
manner using nodes and branches, the LV network is
represented in "Sections" (figure 11); as the section
is a part of the LV network that cannot be further sub-
divided by switches. Basically speaking, the section
can be defined as a part of the LV network which is
divided from the rest of the network by a certain
number of switches, and which does not contain any
other switch inside.
As a number of LV metering devices are connected
to each Section, the address for one of these is made
up of two sub-fields:
~ W095/09473 ~ 2 1 7 Q ~ 24 PCTATg4/00158
- the section number, ~calied the "main address"
- the number of the meter within the section,
known as the "sub-address".
This address is stored within the meter's
electronic unit when it is activated.
The addressing method given above offers the
following advantages.
a) As the network is radially operated, each
section is fed at all times by a specific transformer,
and therefore all the metering devices within the
section are connected to the same transformer.
Consequently, it is not necessary to interrogate all
the electronic units to ensure that the section is
actually connected, but it is sufficient to interrogate
just one. If this responds, the section, and therefore
all the meters in that section, are connected; if it
does not respond, they are not connected. In this way,
updating of the network connection status is very
quick.
b) By reserving, within the section, the number 1
~numbers 2 and 3 are used as a reserve) to address a
meter in a particularly advantageous position for
transmission, that is to say near the main conductor,
if possible at the center of the section, it is
possible to use this meter (known as the "Section
Master") as a relay for re-transmission of messages to
the other metering devices in the same section or to
the Master of another section.
Bearing in mind the usual length of sections in
the LV network, it can therefore be stated that:
- all the meters in one section can be reached by
a message transmitted by the Master of that section;
- the Master of a specific section can be reached
by messages transmitted from the Masters of adjacent
sections.
c) In order to manage all the activities required
for customer service automation, the ACS memory does
WO~5/~9J73 `? : ~~ 2 1 7 0 6 24 PCT ITg4/~0158 ~
not contain any information relating to the meters, but
only a small amount of information relating to the LV
network, which can be fed from the substation in which
the ACS is installed, more specifically:
- the list of sections that can be fed from that
substation;
- the number of meters that are connected to each
of these sections;
- a table expressing the possible connections
between the above mentioned sections (that is to say
the way in which these sections can be connected to
each other and to the adjacent MV/LV substations).
In this way it is possible to avoid the problems
relating to storage and updating of the large amount of
data that would result from providing the ACS with the
data for meters, as is normally the case in prior art
solutions.
d) Another important advantage obtained using this
addressing system is the management, by the Section
Master, of data transmission from each meter to the
respective electronic device with which the user may be
provided.
The routing method will now be illustrated.
Every message transmitted by the center must
contain, as well as the address corresponding with its
final destination, an indication of the route it has to
follow.
Bearing in mind the fact that the MV and LV
networks are radially operated, this route is unique
and is defined by the HV/MV substation and by the MV/LV
substation (in the case of LV users) feeding the user
under consideration (or the substation under
consideration, in the case of messages for remote
control of the network) at the time of data
transmission.
Routing also includes the address of certain
intermediate MV nodes and the masters of certain
~ WO~S/09473 ~ - 2 1 7 0 6 2~ PCT~T94/00l58
. .
- 23 -
intermediate LV sections, to be used as transmission
relays in the "Store and Forward" procedure.
An example of relay procedure performed on a LV
feeder is the following.
The format of the LV message has the structure
shown in figure 12; attention should be focussed bear
on the following fields:
- IND (address): address of the station to
which the message is destined;
_ CTL (control): provides information on the
type of message and is made up of the sub-fields:
NORM = No Repetition
T= SR = Message to repeat
RCP = Message for repetition control
N = Number of repeters
D = Communication rules
- REP (repeat): contains a variable number of
addresses relating to the relay stations and the final
destination;
- INF (information field): contains the
application message destined for the final destination.
With reference to figure 13, which shows the
hypothetical dispatch of a message by the ACS to UE
using two relay stations Rl and R2, let us analyze the
sequence of outgoing and returning messages on the LV
line.
A) The ACS receives a request for communication
with the UE node; from the routing table the relay
procedure manager sees that direct communication is not
possible, and that it is necessary to use relay
stations Rl and R2. It therefore prepares a
centrifugal message with a final address equal to the
UE node, sends it to Rl and reverts to reception mode
with the address R1 (the ACS has no address within the
WO95/09473 -f J ~ ~ 2 1 70624 PCT~194/00158 ~
- 24 -
LV network for which it is MASTER), setting a suitable
Time-out.
B) Rl receives the message and recognizes it as
being destined for the UE via R2; at this point it
re-formats the message, transmits it towards R2 and
reverts to reception mode with the address R2, setting
a shorter time-out to that set by the master node.
C) R2 receives the message from Rl, recognizes the
final destination, re-formats the message and sends it
to the UE node. It then listens in with a suitable
time-out (lower that set by the master), with the
address of UE.
D) The UE recongizes the message as personal to
itself and sends the response to the Master with its
own address (UE) as destination.
E) R2, which was awaiting a centripetal message
with the address UE, receives the message, cancels the
reception timer, re-transmits the message with its own
address (R2) as destination, and then reverts to
standby with its own normal network address (R2).
F) Rl, which was awaiting a centripetal message
with the address R2, receives the message, cancels the
reception timer, re-transmits the message with its own
address (Rl) as destination, and then reverts to
standby with its own normal network address (Rl).
G) ACS, which was awaiting a centripetal message
with the address Rl, receives the message, cancels the
reception timer, picks up the contents of the field INF
and passes it to the application program as if it would
have been originated from the node interrogated (UE).
It should be noted that, thanks to a status
information present on the intermediate relay stations,
and that is to say:
that each relay station is in reception mode with
the address of the relay station downstream, thus
knowing that it awaits a reply from a slave node and
that once reply has been received it can relay it using
W095/09473 ~ '' ; 21 70624 PCTAT94/00158
- 25 -
its own station address;
the messages travelling in a centripetal direction
can have a normal message format with the REP field
empty, resulting in an improvement of overall
performance.
The various time-outs in reception are calculated
by the intermediate nodes according to the
communications rules contained in the sub-field D of
CTL.
Any relay errors are managed by generation of an
RCP message. This message, generated by the relay
station for which the reception time-out triggers, has
the address of the generator node in the field REP and
is transmitted in a centripetal direction in the same
way described above.
From the above, it can be seen that routing of the
message is strictly dependent on an up-to-date
knowledge of the connection status of the two MV and LV
networks; this information is found in the STM sub-
system and is obtained by the following main steps.
- Storage of the structural configuration in the STM
data base, by means of information from another data
base resident in a Host computer and containing
information relating to network structure, information
which is stored at the time of construction and updated
at the time of any alteration works.
- Updating of the status of MV line switches by the
activity carried out by the STM itself to manage the MV
network, also bearing in mind the cyclic interrogation
activity performed by the ACP in the Primary Substation
on the MV nodes fed by the latter.
- Updating of the status of LV line switches by
- means of the cyclic interrogation activities performed
~ by the ACS in each MV/LV substation, on the masters in
the sections fed by the latter.
The background activity performed by the ACS
devices will now be illustrated.
WO95/09473 i~ / 2170624 ~CT ~ 4/00158 ~
Each ACS device, during the day, performs a cyclic
interrogation directed exclusively to the Masters of
the sections fed by the MV/LV transformer within the
same substation (section of the supplied LV network),
or connected to the preceding sections by a switch that
is normally open (section outside the periphery of
supplied network).
When an interrogation message is sent by the ACS
to the master of a known section, during the above
background activity, there are two possibilities:
Al) The "master" responds to the ACS, thus
confirming that the section is still connected to that
transformer. In this case the ACS sends a new message
to the "Master" of the section to start a data
updating procedure towards electronic device within the
user's home.
This procedure assigns a clearly defined amount of
time to each meter in the section to send certain data
from its UEP to the respective electronic device that
may be installed with the user.
At the end of this procedure (the duration of
which is known to the ACS on the basis of the number of
users connected to the section), the ACS proceeds to
interrogate the master of another section.
A2) The "Master" does not respond, thus permitting
the ACS to note that the section is no longer connected
to that transformer. In this case the ACS records this
information and reverts to "Alarm State" to allow the
ACP to record this information and pass it on to the
STM in order to update the network connection status.
When an interrogation is sent by the ACS to the
master of a known section, by the above background
activity, as a section situated at the external
periphery of the supplied network, there are two
possibilities:
Bl) the master does not respond to the ACS, thus
confirming that the section is not connected to the
~ W095/09473 2 1 7 0 6 2 4 PCTAI~4/00158
- 27 -
transformer.
B2) The master does respond, thus allowing the ACS
to note that the section, which was previously
disconnected, is now connected to the substation in
which the ACS is installed.
Whereas in the former case (Bl) the ACS proceeds
to interrogate the "Master" of another section, in the
latter case (B2) the ACS performs the same operations
described in the point A1 to allow transfer of
information from each UEP to the respective user device
and performs the operations described in point A2 to
update the working configuration of the STM.
Furthermore, the ACS performs the synchronization of
the clocks in the meters within the section, which, for
cost reasons, are not provided with a back-up power
supply and which therefore loses synchronization when
the LV section is transferred from the network supplied
by one transformer to the network supplied by another
one (this transfer operation, in order to avoid
parallel working of the two transformers, requires the
section to be deenergized for a short period).
The sub-system for Automation and Remote Control
of the MV network will now be illustrated, allowing the
following functions:
- Management of network diagrams,
- Network supervision and control,
- Automatic procedures to identify faulty feeder
sections and re-supply the healthy ones.
The a~ove functions are carried out using
technologically advanced instruments, such as graphic
workstations, plotters, colour printers.
The man-machine interaction procedures make use of
entirely graphic environment procedures and real-time
- windows systems to guide the operator through the
operations possible at each specific time, and to give
instant visualization of changements in progress on the
network.
W095/09473 ~ 2 1 7~ 624 PCT~194/00158 ~
- 28 -
All operations are performed by the operator
exclusively using the Mouse, which enables the choice
of objects and commands in the on-screen Menus.
The network diagram is managed entirely on-screen
by several levels of visualization and the use of
"Panning" commands for the positioning on the screen of
the desired portion of the diagram.
The symbols used to represent the electrical
elements are not the usual ones, but an "ad hoc" series
of symbols is used in order to give greater information
and to use better the space available on screen.
These symbols are illustrated in figure 2.
More specifically, the MV network is managed by
means of the following diagrams:
General network diagram (figure 14). This
schematic diagram, which is contained in a single video
page, gives a compact illustration of the whole network
to be remote controlled, with a simple representation
of all the Primary Substations in the Zone. Starting
from this page, the operator can select one Primary
Substation and request visualization of the topological
diagram for the MV network around the substation
selected.
Topological network diagram (figure lS). This
schematic diagram shows all the secondary substations
that are remote controlled, with their respective
connections. It is generally an extremely large
diagram, which cannot be shown in a single video page,
but thanks to the "panning" it is possible to move
through it in a continuous manner, visualizing any part
of the chart. The topological diagram is the main
working base for operation of the network. From this
diagram it is possible to operate on the network
requesting visualization of line and substation
diagrams on overlying windows and so on.
MV feeder diagram (figure 16). This diagram,
which is obtained from the preceding one by
~ WO95/09473 ~ 21 70~4 PCTAI94/00158
- 29 -
highlighting the portion of network electrically
connected to a specific MV circuit-breaker, is
fundamental for feeder boundary changements, network
adjustment, manual recovery of service following a
fault or an unavailability period. At each point at
which it is possible to reenergize a feeder power the
directrix, all the information necessary for resupply
actions is given. Furthermore, by a suitable
compacting algorithm, it is always possible to obtain
un-deformed visualization of the whole feeder line,
even when the latter is greater than the screen size on
the topological diagram.
Feeder section diagram (figure 17): As only remote
controlled substations are shown on the topological
diagram, it is necessary to have a further level of
detail, which can be selected from the topological
level. From this schematic diagram it is possible to
update information on all the non-remote controlled
secondary substations within a section.
The aim of this diagram is to allow manual
updating of the information relating to the status of
switches that are not remote controlled.
If ACS devices are installed in the substations
within a section for remote management of users, thanks
to the interrogation of these ACSs by the ACP it is
possible to highlight any incongruities between the
status of switches deriving by manual updating of the
diagram and the connection status of the network
deriving from the communication subsystem.
Primary Substation diagram (figure 18): a window
containing the typical schematic diagram of a primary
substation with the HV/MV transformers, the bus-bars
fed by them, and the connected MV feeders.
Secondary substation diagram (figures 19 and 20):
by selecting the proper symbol on one of the prP~P~;ng
diagrams, a detailed schematic diagram of that
substation can be obtained. This schematic diagram
WO9S/09473 ~ ~ 2 1 7 0 6 24 PCTAT94/00158 ~
- 30 -
shows all the information relating to the substation
itself, and it is possible to send remote commands or
perform manual settings of the status of switches or
breakers that are not remote controlled.
As well as wiring diagrams, alphanumeric pages are
also available, underlining alarm situations and
variations in status (as compared with the status
considered normal). From these pages it is possible to
obtain the diagram of the corresponding electrical
element directly, merely by selecting an alarm.
The graphic configuration of any element within
the network at any hierarchic level, as well as being
simple and quick for the operator to create, involves
the creation and automatic updating of the relative
structure in the data base in a manner that is totally
transparent for the operator, thus making subsequent
analytical description of the element itself much
easier.
Because of the great frequency of interventions on
and changements of the medium voltage network,
particular care has been taken to improve the
simplicity of procedure, the ease of access to
information and the speed with which alterations are
carried out.
Changements of network diagram are thus performed
"on line", that is to say without interrupting the
operation of the System. This is possible as the
operations for configuration and modification of the
network Data Base are normally carried out on a
temporary copy of the data base and then, once
congruency tests have been performed, the changements
are propagated within the System.
The supervision and control procedures for the
distribution network will now be illustrated.
To enable network management from a work station,
the latter must be in a "network operation" mode; in
this condition there is a reciprocal exclusion
~ W095/09473 - - - 2 1 7 0 ~ 2 4 PCTAI94/00158
- 31 -
mechanism that prevents two stations from operating
simultaneously on the same electrical element. This
mechanism is activated in two ways:
- The dynamic block: automatically assigning the
exclusive ability to operate on an electrical element
to the first workstation selecting the command; the
block operates from the moment in which the command is
selected until it is completed or cancelled.
- Working attribution: assigning the exclusive
ability to operate on the whole feeder to a specific
workstation. Attribution of a feeder may be determined
statically during configuration, or it may be
established during normal operation.
The alarms and variations in status that relate to
both the MV network and the Primary Substations, are
routed to the various workstations, by which they are
acquired automatically or manually according to the
working attribution; they are then printed on the
"Service Protocol" and filed in the mass storage.
By selecting a specific alarm from the alarm
pages, the operator can access the diagram for the
corresponding electrical element, and then perform
whatever adjustment he desires.
In addition to the remote control of circuit-
breakers in the Primary Substations and of load
breaking switches in the secondary substations, theoperator can perform the following:
- request print-outs (in graphic or table form),
- search the data base,
- search the back-up files containing past operating
data.
The automatic procedures will now be illustrated
for identification of faulty feeder sections line and
re-energizing of healthy ones.
In order to guarantee rapid service restoration
following any faulty that may occur, including those
occurring at times in which the Zone control Center is
W095/09473 ~ 3s i ' ~ ~ ~ 2 1 7 0 6 24 PCT~194/00158
- 32 -
not manned, STM provides a series of automatic
procedures aimed at identification and isolation of the
faulty section of line between two remote controlled
substations, the re-energizing of the section of the
network upstream of the faulty section, and the
possible re-energizing of the network downstream of the
latter.
As the telecommunications system does not allow
exchange of information with the MT circuit-breaker
open, the remote terminal unit devices (UPT) have been
designed with a high degree of autonomy (automatic
rules for opening and closing the switches), giving
them the ability to identify and isolate a faulty
section of line autonomously.
As the rules for opening the switch are activated
on the basis of a lack of voltage on the line and on
the bus-bar in a secondary substation, any failure in
power supply to a Primary Substation MV bus-bar, should
it continue for longer than the time limit set for
activation of the above rules, causes the unnecessary
opening of all the switches in the remote controlled
substations powered by that MV bus-bar.
In order to overcome this problem, the STM is
provided with an automatic procedure which, ~ollowing a
loss of voltage on a Primary Substation MV bus-bar,
sends a message disabling the automatic rules to all
the UPTs involved within the necessary time limit.
When the voltage returns to normal, the STM
automatically restores the initial status.
In order to perform functions relating to
identification of the faulty section correctly, the
remote controlled secondary substations must be
suitably equipped with voltage detectors (RV) and, in
urban underground networks, with devices to sense the
passage of fault current (RG).
The RGs to be installed on each cable terminal are
made up of a toroidal probe, to be installed around the
~ W095/09473 ~l ~ 2 1 7 ~ 624 PCT~T94/00158
cable itself, capable of picking up the passage of
homopolar currents (caused by phase to earth faults) of
an intensity exceeding a certain predetermined level
(typically 60 Amp.), and three "maximum current"
probes, one for each phase, capable of picking up the
passage of short-circuit currents exc~;ng a certain
predetermined level (typically 600 Amp.); this
information is passed through small cables and optical
fibers to the electronic circuits which, in case of
malfunction, cause an optical and an electrical signal
(closing of a contact) to be emitted.
For this reason, two different MV fault management
procedures have been implemented: one being employed
mainly for overhead networks and using RV only, the
other employed mainly for underground cable networks
and using RG as well as RV.
Procedure for sectionalizinq faulty feeder sections
Method of operation of the UPT.
The UPT essentially gives a series of rules fbr
opening and a series of rules for closing the switches.
The opening rules have the aim of isolating the
malfunction, whereas the closing rules serve to re-
energizing the bus-bar in the secondary substation,
thus restoring communication.
Each switch is associated to a specific group of
rules, which are univocally identified by the type of
switch (incoming, outgoing, boundary) and by the type
of network, overhead (without RG) or cable (with RG).
The following table illustrates the structure of
the various groups according also to the type of switch
with which they are associated.
W095/09473 ~ .~ r ~ 2 1 7 0 6 2 4 PCT~1~4/00158
.
- 34 -
RULE ¦ l I
¦ GROUP ¦ l l IMS ¦ NETWORK ¦
l l OPENING¦ CLOSING ¦ ¦ TYPE
¦ A I RaVO, RaV1 ¦ Rcvo ¦ Generic ¦ OVERHEAD
¦ C I RavO' Ravl ¦ Rcv1 ¦ Border ¦ (no RG)
¦ D ¦ Rago~Ragl~Rag2l RcgO ¦ Generic ¦ CABLE
10 ¦ E I RagO I Rcgl ¦ Border ¦ (with RG) ¦
Given that the following terms have the following
meanings:
- IMSi, generic motorized load breaking MV line switch
- RVLi, voltage detector associated with the MV
line originating at IMSi
(RVLi=voltage present on i-th line; RVLi=current
voltage absent on i-th line)
- RVS, voltage detector associated with the MV
bus-bar to which IMSi relates
(RVS=voltage present in bus-bar; RVS=voltage absent in
bus-bar)
- RGi, fault current detector associated with the
MV line from IMSi
(RGi = fault current recorded; RGi = fault current not
recorded)
- Tavn, Tcvn Tagn, Tcgn, times indicating
perduration of a condition
- *, AND logic operator.
The following is a description of the rules that
the UPT must apply to single switch, to enable them to
move autonomously.
Rules for UPT without RG
The opening rules that apply for UPT without RG
are the following:
RavO = RVLi * RVS * TavO > open IMSi
Ravl = RVLi * RVS * beta >
~ W095/09473 21 7~624 PCTAIg4100158
- 35 -
- if the IMS in question was closed with an
autonomous command, it is opened first and then all the
other IMSs on the bus-bar are opened. A group of rules
Z (blockage of all IMS) is associated to all IMSs;
- if the IMS in question was closed with a remote
command, it is opened and the group of rules Z
(blockage of that IMS) is associated to it.
The condition beta occurs when the IMSi passes
from the open state to the closed state in the presence
of line or bar voltage, and the condition of lack of
line or bar voltage occurs within Tavl seconds.
The condition beta resets after a local or remote
comand closing the IMSi.
The closing rules that apply for UPT without RG
are the following:
RcvO = RVLi * RVS * TcvO * delta ,,,,> close IMSi
Rcvl = RVLi * RVS * Tcvl * delta ,,,,> close IMSi
The condition delta occurs when all the IMS on the
bus-bar are open.
One of the following groups of rules can be
associated to each IMS in an UPT without RG:
- group "A", made up of rules RavO, Ravl and
RcvO
- group "C", made up of rules RavO, Ravl and
Rcvl
- group "Z", made up no rules (IMS block).
Rules valid for UPTs with RG
The opening rule~ that apply for UPTs with RG are
the following:
RagO = RVLi * RVS * TagO ,,,,> open IMSi
Ragl = RVLi * RVS * RGi * alpha ,,,,>
- opening of the IMSi and association of the group
of rules "Z" to it.
The condition alpha implies that one of the
following conditions has been met:
- the UPT receives no reply to the fault
interrogation message sent to another UPT;
W095/09473 . ~ 2 1 7 0 6 2 4 pcTnTg~lool58
.
- 36 -
- the IMS whose RG has sensed the fault has no
UPT associated with it.
Rag2 = RVLi * RVS * RGi * gamma ,,,,>
- opening of all the IMS on the bus-bar starting
from the one associated to the RG that sensed the
fault current, and association of group "Z" to them.
The condition gamma occurs when:
- the RG of all the IMSs, with the exception of the
i-th IMS, have sensed the fault current;
- the UPT has transmmitted the message responding
to the interrogation received from the preceding UPT.
The closing rules that apply for UPT with RG are
the following:
RcgO = RVLi * RVS * TcgO * delta ,,,,> close IMSi
Rcgl = RVLi * RVS * Tcgl * delta ,,,,> close IMSi
The condition delta occurs when all the IMS on the
bus-bar are open.
one of the following groups of rules can be
associated to each IMS in an UPT with RG:
- group "D", made up of rules RagO, Ragl, Rag2
and RcgO
- group "E", made up of rules RagO and Rcgl
- group "Z", made up of no rules.
For each line IMS in a secondary substation, the
configuration message must be sent to the respective
UPT. This configuration message contains: the group of
automatic rules to be applied, the address of the UPT
downstream. Furthermore, the values of the opening and
closing time constants must be configured for each UPT.
Startu~ of the procedure
When final tripping of the MV line circuit-breaker
takes place, due to the intervention of one or more
protections, STM starts a timer T1, following which it
comm~n~ the MV circuit-breaker to close. If this
operation, which simulates slow re-closing, causes
further tripping, then the procedure for sectionalizing
faulty section starts.
-
~ W095/09473 2 1 7 0 6 2 4 PCTATg4/00158
- 37 -
Sectionalizing faultY feeder section Procedure
overhead lines fwithout RG)
After the time interval T2 from the last trip,
during which the UPT opens all the IMSs (application of
opening rule Ravl), STM commands closure of the MV
circuit-breaker in the Primary Substation.
At this point it is better to differentiate
between 4 types of faults, according to their location:
First section fault. The closure of the MV
circuit-breaker causes instantaneous tripping of the
latter; the System emits the diagnostic "Fault on first
section" and terminates the procedure (if possible the
automatic re-supply procedure is started).
Fault on the bus-bar of the first substation on
the feeder. Closing of the MV circuit-breaker, in this
case, gives positive results; STM positions itself to
await automatic closure of the IMS entering the first
substation (RcvO).
When this takes place, the consequent tripping of
the circuit-breaker will allow the STM to diagnose a
"Fault on first substation and, after having waited for
Tl seconds, during which time the IMS opens and blocks,
to reenergize first section.
Fault on an intermediate section. Closure of the
MV circuit-breaker, in this case, has positive results;
STM positions itself to await automatic closure of the
IMS entering the first substation. When this takes
place, connection between the system and the UPT
resident within it is restored and the STM starts to
re-close the first of the IMS on output from the
s~bstation; if no other remote controlled substation is
connected to it, the procedure continues to re-close
the other IMS adjacent to it on the bus-bar, until
another remote controlled secondary substation is re-
3S energized.
At this point the central System once more revertsto standby to await automatic closure of the IMS
W095/09473 ~-ii f 't ~ ~ 2 1 7 0 6 2 4 PCTAl94/00158
1
- 38 -
inputting to the substation. When closure has taken
place and after the subse~uent recovery of
communications between the system and its respective
UPT, STM starts a new substation IMS closure cycle
using remote commands. At the moment in which a
faulty section is fed anew, the MV circuit-breaker
trips, and the IMS performing the closing on fault
opens and blocks. After T1 seconds STM re-closes the
circuit-breaker and renergizes the feeder up to the
section immediately upstream of the faulty one. At this
point the System, by interrogating the UPT in the
substation on which it was operating before the trip
and by picking up the open and blocked status of the
last IMS handled, emits the diagnostic relating to the
faulty section. Then the automatic procedure goes on to
re-energize any branches upstream of the fault that may
still be without power. (If possible the automatic
resupplying procedure is started).
Secondary substation bus-bar fault. The return of
voltage on the line supplying a substation causes
automatic closure (rule RcvO) of the IMS inputting to
the faulty bus-bar, causing the main circuit-breaker to
trip. The IMS in question opens automatically and
reverts to block status. After T1 seconds from the
trip, STM corm~n~ closure of the MV circuit-breaker,
reenergizing the feeder and restoring connection
between the system and the UPT immediately upstream of
the substation in which the fault has occurred.
By interrogating the latter (the UPT upstream of
the fault), STM recognizes that the IMS connecting the
substation to the one downstream is closed as usual, so
that it is not a section fault, which would have cause
opening and block of the IMS, but a fault in the
downstream substation bus-bar. STM emits the
diagnostic relating to the faulty secondary substation
bus-bar and the procedure goes on to re-energize any
branches that may have been left without power. (If
W095/09473 ' ~ ~1 7 ~ 6 24 PCTAI94/00158
- 39 -
possible the automatic re-supply procedure is started).
For the above, with the exclusion of "The first
section fault" and "First substation fault", when the
main circuit-breaker trips for closing on fault, STM
does not immediately discriminate between a section
fault and a substation fault; this will, only be
possible after having interrogated the last UPT with
which dialogue took place (the UPT upstream of the
fault).
In general, an IMS opens and blocks only if the
fault is detected within Tavl seconds from its closure.
This characteristic allows the exact location of the
fault to be identified (line or bar).
Furthermore, the command to re-close, which is
emitted by STM subsequent to the last trip, prevents a
transitory or semi-permanent fault that may occur on
the feeder during the identification phase, from being
mistaken for the permanent fault that has started the
procedure.
In fact if, when service is resumed, the STM finds
no IMS in block mode, that is to say if no fault has
been identified, the procedure continues by feeding the
other sections. Naturally the above error would occur
in the case of a transitory malfunction occurring
within the time Tavl, which, however, is fairly short.
It will now be illustrated an example of procedure for
a permanent fault on section "c" of figure 21.
Figure 2la shows a schematic diagram of the
overhead network under consideration, energized under
normal working conditions by substation CPl through a
MV circuit-breaker Il.
*- The group o~ rules associated to each IMS is
indicated beside the graphic symbol, and causes them to
behave as illustrated above.
l) When a fault occurs on section "c", the
circuit-breaker Il opens then performs a rapid re-
closure; the fault remains and the trip becomes final.
W095/09473 ~ 2 1 7 0 6 2 4 PCT~lg4/00158
,
- 40 -
2) After T1 seconds, STM commands another re-
closure, and when this results negative starts the
procedure for sectionalizing the faulty section.
3) After a period of time T2 to ensure
5 opening of all the IMS on the feeder (fig.21b), STM
sends a command to close I1 and awaits the result of
it.
4) As the first section of line is healthy, the
remote closing command is performed correctly and the
System waits for the IMS entering CABl to close
automatically (applying rule RcvO).
5) After the required time has passed, the IMS
results closed and transmission connection restored;
STM starts to talk to UPTl and thus acquires the actual
closed status of the switch moved (Fig.21c).
6) STM commands closure of the first IMS in output
(IMS2) and awaits performance of the remote command.
7) The System interrogates the UPT again to check
that the manoeuvre has been performed successfully.
8) Having checked that IMS2 moves correctly, STM
sends the command closing the next switch IMS3 and
awaits execution of the remote command.
9) The System interrogates the UPT again to check
that the manoeuvre has been performed successfully,
then, as IMS3 covers a remote controlled substation,
the system starts a timer to await closure of the
ingoing switch in CAB2.
10) Afterwards, STM interrogates the UPT in CAB2
to check that the incomming IMS has been closed and to
command closure of the outgoing one.
11) Having checked that IMSl moves correctly, the
command closing IMS2 (in CAB2) is emitted, and STM
begins to await the result of the remote command
(Fig.21d).
12) Consequent closure on the faulty section
causes: tripping of circuit-breaker Il and opening and
blocking of IMS2 in CAB2. Folling this event a timer
~ WO95/09473 ~ ' 2 1 7 0 624 PCTAI~4/00158
Tl starts (Fig.21e).
13) When timer Tl runs out, because of IMS2 in
CAB2 is open and blocked, STM can re-close Il.
14) Following positive closure of Il, STM
interrogates the UPT of CAB2 again on the present
status of the switches. Having picked up the open and
block of IMS2, the STM emits the diagnostic "Fault on
line C" and returns to CABl to close IMS4 which is
still open.
15) Having emitted the command closing IMS4 of
CABl, the process awaits closure of the IMS entering
CAB5 (Fig.2lf).
16) Once correct closure of IMS1 in CAB5 has been
checked, STM emits the command closing IMS2.
17) Once closure of IMS2 in CAB5 has been checked,
STM awaits closure of IMSl of CAB6, and when this has
occurred also closes IMS2 using a remote command.
18) The process terminates, or the process for
re-energizing CAB3 is started if the required
conditions have been met.
Sectionalizinq faultv feeder section ~rocedure -
under~round cable (with RG)
On start-up of the procedure, with no voltage on
the line, a waiting time is set up, during which the
UPTs interrogate each other in cascade to identify the
fault and open the IMS isolating it.
At the end of this time, the STM commands closure
of the main switch and re-energizes the working
sections of the feeder (unless the malfunction is in
section I of the line).
Generally speaking, three types of fault can be
distinguished:
Fault on first section. Closure of the MV
circuit-breaker causes instantaneous tripping of the
latter; the System emits the diagnostic "Fault on first
section" and terminates the procedure (if possible the
automatic re-supply procedure is started).
-
W095/09473 ~ 2 1 7 0 6 2 4 PCT~T~4/001~8 l
- 42 -
Fault on an intermediate section. Closure of the
MV main switch, in this case, has a positive effect,
and allows the STM to communicate with the UPTs and
therefore to emit the signal indicating the section in
which the malfunction has occurred. In fact, the
interrogation sequence sent to the UPTs regarding the
status of the various IMSs will underline a situation
in which one switch is found to be open, whereas the
same switch was not open just before the fault
occurred. STM therefore emits a diagnostic identifying
the fault on the section downstream of the above
switch.
SecondarY substation bus-bar fault. On service
restoration, STM starts to dialogue in cascade with the
feeder UPTs. One UPT does not respond, in spite of the
fact that the IMS feeding it in the preceding remote
controlled substation is closed. The system signals
the presence of the fault on the bus-bars of the
substation corresponding to the un-reachable UPT.
As an example, the procedure will be illustrated
for a permanent fault on line "c" of figure 22.
Figure 22a shows the network under consideration,
supplied under normal conditions by substation CPl
through the MV circuit-breaker Il.
The group of rultes associated with each IMS is
indicated beside the graphic symbol, and causes them to
behave as illustrated above.
l) When the malfunction occurs on line "c", the
fault detectors RGl and RG2 of CABl, RGl and RG2 of
CAB2 switch to "On", then the line protections cause
the circuit-breaker Il to trip, opening the line.
2) STM starts a timer with a duration Tl,
following which the circuit-breaker will be re-closed
(Fig. 22b).
3) After a time Tin from loss of voltage, UPTl,
which knows itself to be the first on the feeder, sends
an interrogation message GI to the UPT downstream of
~ W095/09473 `~`~ ~ 21 7~624 PCT~1~4/00158
- 43 -
the outgoing line on which the RG is in "on" state
(~PT2).
4) UPT2, having received the interrogation
message, responds with RGR, thus confirming the "On"
status of one of its RGs. After sending the message
RGR to UPT1, UPT2 in turn sends an RGI to UPT3.
5) UPT3, which has no RG in "On", does not respond
(or else the fault prevents transit of messages on the
section).
6) UPT2, upon failing to receive a response,
understands that the fault is on the section downstream
of its own IMS2, opens it and sets it to blocked mode
(Fig. 22c).
7) After timer T1 has passed, STM re-closes Il and
the line is re-energized up to CAB2. Return of
voltage for a sufficiently long period of time produces
"Reset" of the RGs in the re-energized substations
(~ig. 22d). By interrogating UPT2, STM picks up the
open and blocked status of IMS2 and diagnostics a fault
in section "c".
Automatic re-supPlY Procedure
If the structure of the electrical network and the
current capacity of the conductors allows it, once the
section or substation that is faulty has been isolated,
a procedure for re-supply of the healthy sections
downstream of the fault can be started.
This is possible because the IMS (normally open),
which is the boundary between the feeder containing the
fault and that adjacent to it, is provided with an
automatic rule that causes it to close if there is a
loss of voltage lasting for a determined period of
time.
When this interval of time (which is calculated in
such a way as to ensure completion of the procedure for
sectionalizing of the faulty section described above)
has passed, closure of this IMS re-establishes data
connection with the boundary substation and the
W095/09473 ~ 7~ 2 1 7 0 6 24 PCT~T~4/00l58
- 44 -
consequent ability of the STM to re-energize all the
working section of line downstream of the fault by an
iterative process.
In effect, the remaining IMS on the bus-bar of the
boundary substation are re-closed by means of remote
commands. Those in input into the next substation,
which close again thanks to one of the automatic rules,
in turn restore connection to the respective UPT and
allow the procedure to be repeated up to the section or
substation immediately preceding the malfunction.
The subsystem for remote management of Medium
Voltage and Low Voltage users will now be illustrated.
The subsystem in question allows remote management
of both LV and MV users, thus making it possible to
carry out a series of operations that would normally
be carried out on site by specialized staff.
With this aim, new metering units provided with
the electronics required to support this application,
have to be installed for all MV and LV users.
These metering units, at least for the present,
use conventional electro-mechanical technology
(Ferraris meter) for measurement of energy and only use
electronic digital technology for the additional
functions, which are therefore performed by an
electronic device, closely connected to the meter.
This hybrid solution has the advantage, with respect to
a fully electronic solution, of preserving measurement
of overall energy consumption in case of failure of the
electronic device.
On the other hand the solution chosen is open to
the future introduction of electronic meters, once
these have reached a level of reliability and cost
comparable with those of the Ferraris meters.
The solution used in our "Integrated Metering
Apparatus" integrates all the necessary components in a
single case, which is completely closed and sealed and
made of plastic reinforced with fiberglass.
~ W09~/09473 ~ 2 1 7 0 6 2 4 PCT~194/00158
- 45 -
With reference to the two main categories into
which users are divided, these components are the
A following:
* For mass users, that is to say domestic and
residential LV users:
- a meter for measurement of active energy
- a thermomagnetic circuit breaker to protect the
upstream circuit (and to limit the m~ m demand
below the contractual value when the electronic unit is
not installed in the meter)
- an electronic unit for data processing and
communication.
* For large LV users and for all MV users:
- two meters, to measure active and reactive
energy
- one electronic unit for data processing and
communlcatlon.
The electronic units.
For transmission of the consumption data indicated
on the Ferraris meter to the electronic unit inside,
each meter is provided with the following (~igure 16):
- one sector wheel to generate the count pulses;
- two optical fibers to transport light from one
end of an optical connector to the sector wheel, and
from the latter to the other end of the optical
connector;
- an optical connector, installed on the surface
of the case, towards the corresponding connector on the
electronic unit.
The sector wheel is mechanically connected to the
shaft of the meter and its perimeter is divided into a
certain number of sectors, alternately filled in or
empty, so that they are either completely transparent
or completely opaque under incident light.
One end of each optical fiber is fixed in
correspondence with the edge of the wheel, in a face-
- to-face configuration, whereas the other end is
-
WO9~/09473 ~X~ 2 1 7 0 6 2 4 PCT~lg4/00158
.
- 46 -
connected to the connector.
The light beam, generated by a photo-electric
emitter installed in the electronic unit, is carried to
the edge of the sector wheel through one of the two
optical fibers, either passing through or not passing
through the wheel, according to the position of the
sectors.
When the light beam crosses the wheel, it is
picked up by the other optical fiber, which carries it
to the other end of the connector and from there to a
photo-receiver, likewise installed in the electronic
unit next to the photo-emitter.
In this way light pulses are produced, each one of
which corresponds to a clearly defined amount of energy
made independent by the constant of the meter in an
appropriate design of the activating mech~n; ~m and of
the sector wheel.
Thanks to the system described above, only
passive, highly reliable elements are installed within
the casing of the meter, while active elements are
positioned inside the electronic unit.
The categories of user in an electric utility, the
various types of Integrated Metering Apparatus and the
corresponding electronic units are illustrated in
figure 17 according to the subscribed demand.
The main categories into which users of a generic
electric utility can be divided are the following:
- domestic and residential LV users with a
subscribed demand not exceeding 15 kW: this category
makes up the majority of the utility's users.
- large LV users with a subscribed demand over 15
kW and MV users.
Domestic and commercial LV users.
The following types of Integrated Meters have been
developed:
- single-phase users: GMY (figure 18)
- three-phase users: GTY (figure 19)
~ W095/09473 ~ 21 70624 PCTA194/00158
- 47 -
The thermo-magnetic circuit-breakers installed
inside the GMY and GTY are original products, designed
to satisfy the following needs:
- limitation of the power available to the user by
means of the thermal relay of the circuit-breaker when
the apparatus operates without an electronic unit (in
this case the apparatus must be chosen according to the
power subscribed;
- elimination of intervention by the thermal
relay once the electronic unit has been installed, and
activation of the trip pulse emitted by the electronic
unit when the power level exceeds the set value (in
this case the apparatus no longer refers to the power
level subscribed by the user).
- As stated ~bove, this value can be changed from
a remote center following variation of the contract,
emergency in the supply, etc.;
- activation of a continuous trip signal emitted
by the unit, which prevents the user from closing the
circuit-breaker, should supply cease or should there be
a~ excessive delay in payment.
With reference to the latter two functions, the
circuit-breaker has been provided with a tripping coil
which allows it to be controlled by the electronic
unit. The electronic unit is the same both for the GMY
and for the GTY, but it has been made in two different
versions called UEP and UEPR (reduced UEP).
The UEP is used in an Integrated Metering
Apparatus when the latter is installed inside the
user's premises, whereas the UEPR is used in an
Integrated Metering Apparatus when the latter is
installed on a central board (on the same panel, which
is usually situated on the ground floor of the
building, it is possible to install up to 24 meters).
In case of installation in a central board, the
functions of the electronic unit are grouped in a
single unit (UEPC) which performs these functions for
W095/09473 ~ r 2 1 7 0 6 2 4 PCT~1~4/~01~8
1
- 48 -
all the apparatus on the board. The photo-emitter and
the photo-receiver for generation and pick-up of the
optical signals and the final relay to trip the
circuit-breaker are the only components inside the
UEPR, which is thus an extremely low-cost unit.
Consequently, the overall cost of application of the
automatic system, when the apparatus are installed on a
central board, is much lower than in case of single
installations. Figures 20A and 20B show how an UEP or
an UEPR can be inserted from the back of a GMY, and how
the GMY itself can be installed on the central board.
Figure 21 shows a central board with an UEPC serving
all the metering apparatus on the board.
As regards large "Low and Medium Voltage" users,
the following Integrated Metering Apparatus have also
been developed:
- GTWD for LV users with a subscribed demand
between 15 and 30 kW (direct connection)
- GTWS for LV users with a subscribed demand
between 30 and 250 kW (in this case current
transformers are necessary for connection);
- GTWM for MV users (in this case current
transformers and voltage transformers are necessary for
connection).
These apparatus are illustrated in figures 22, 23
and 24, respectively; although their cases differ in
certain points, they are obtained from the same mold.
The current transformers required for the GTWS
apparatus are the same for the whole range of use, from
30 to 250 kW; they are housed in the case illustrated
in figure 25, on which the apparatus is installed by
means of plug connectors.
The above case houses four current transformers
(TA) instead of the three that are strictly necessary
(one TA is also inserted on the neutral conductor) in
order to detect any fault that can be detected from the
imbalance of the four secondary currents.
WO95/09473 - 21 7 062 PCTAT94/00158
The voltage and current transformers required for
the GTWM apparatus use a single voltage ratio and four
current ratios, and can be used to cover the whole
field of use of the apparatus on ENEL's MV networks,
with nominal voltages between 10 and 20 kV.
The current and voltage transformers can be
installed in two different types of housing: the first
is an air-insulated compartment, the second is an SF6-
insulated box (figure 26).
The air-insulated compartment comprises the
coupling device for transmission of high-frequency
signals from the electronic unit to the MV network,
whereas in the SF6-insulated box this device is
inserted externally by a plug connection, to allow easy
replacement in case of malfunction.
For the MV users, three current transformers are
used instead of the two that are strictly necessary, in
order to detect malfunctions using a device that is
sensitive to imbalance in the three secondary currents;
malfunctions of voltage transformers, on the other
hand, are detected by comparing the peak values of the
two voltages measured.
In case of fault in a measuring transformer, an
alarm is immediately sent to the center by means of the
2S electronic unit.
The electronic units used in these apparatus are
the following:
- UEPB both for GTWD and GTWS;
- UEPM for GTWM.
As in neither of these cases does ENEL own a
switch in the supply board, the electronic units are
able, in an emergency, to send a trip signal to the
user's switch.
The available functions will now be illustrated as
an example.
By means of the sub-system for customer service
automation it is possible to perform the following
W095/09473 ~ ~ ~ 2 1 7 0 6 2 4 PCTAT94/001~8 ~
- 50 -
operations from a remote location:
Remote reading of metering apparatus. Once a day,
starting for example at 00.00, each ACS interrupts its
background activity described above, and starts a new
polling procedure consisting in the reading of data
recorded by all the meters fed by a transformer, in
order to ac~uire the following:
- diagnostic information on the meters themselves;
- data consumption from meters for which the
invoicing period has terminated at midnight of the
previous day;
The messages from the LV meters are temporarily
stored in the ACS, from which they are then picked up
by means of another procedure, parallel to the first
one, carried out by the ACP on the ACS under it; the
ACP in turn sends the data to the Central system. The
latter retains the data with which it is concerned and,
by means of the packet switching network, sends those
relating to consumption to the Host Computer in the
commercial department for invoicing.
Application of time of day tariffs: by means of
the new meters it is possible to apply time of day
tariffs to all users, both LV and MV, and to carry out
remote modification of the structure and parameters of
these tariffs.
Modulation of the power level available to the
user: by means of a suitable parameter K, which can
vary between O and 1, it is possible to modify the
power level available to the user, reducing it to a
vital minimum level in emergency power supply
situations, or even to zero if payments are in arrears
or upon termination of contract.
Remote modification of contractual parameters: all
contractual parameters, and in particular the set value
of power can be modified from a distance.
The above procedures are performed by the System
in the following manners.
~ woss/09473 ; 2 1 7 ~ 6 2 4 PCT~T~4/00158
When the Host Computer dedicated to commercial
procedures receives a request from a user that involves
modification of certain pre-set values within the meter
(variation of power supply level, termination of
contract, etc.), it sends this request to the
Distribution Automation System, where the changements
are performed.
The latter converts the user identification code
used by the Host Computer into the actual address used
by the Distribution Automation System, then it adds the
routing data on the basis of information continually
updated by the STM.
The message is sent to the meter, which confirms
correct acquisition of the request; in exceptional
cases on the LV network, the message might require a
number of attempts before reaching destination, or it
might even be delayed by several hours in order to
await better conditions for transmission.
Thus, immediate acquisition of the command cannot
always be guaranteed; for this reason the procedure
allows an execution time to be associated to each
command. This time normally is chosen sufficiently far
from the time of transmission.
Communication between the LV meters and the MV/LV
substation causes a flow of signals which propagates on
tlle wires and can be received inside the user's home
through a special "User Terminal" (TU).
The communication protocol, together with the
cyclic sequential polling, allows the channel to be
shared by all the transmitters, that is by all the LV
meters supplied by the same substation.
In this way the information relating to one user
can be refreshed at an acceptable rate for practical
use.
An adequate choice of data creates a powerful
interface that can have an important role in load
control and in energy saving in a program for
W095/09473 ~ 2 1 7 0 6 2 4 PcTAT94/ools8 ~
- 52 -
automation of the home or building.
The flow of information from the electric
utilities is shown in a manner that is easily
comprehensible to the user, and can be used for fairly
sophisticated control of the load performed by the home
Automation system. Furthermore, as the connection is
potentially bidirectional, these services can be
further extended.
It must be noted that construction details
relating to the metering groups and the necessary
structures are described in detail in the Italian
patent application No. 47576A/90, filed on 26 January
1990 in the name ENEL - Ente Nazionale per l'Energia
Elettrica.
