Note: Descriptions are shown in the official language in which they were submitted.
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1
A P01NER LINE COMMUNICATION SYSTEM AND
AN INTELLIGENT METER
Technical Field
This invention relates to communication methodologies and systems utilising
power lines, such methodologies and systems often also referred to as mains
communication methods and systems. In particular, but not exclusively, the
present
invention relates to the establishment of a power line communication network
and a
to method of communicating over the network.
Background
Communication over power lines has been proposed and used for remote
metering. In typical systems for remote metering, a central controller
communicates with
a meter using a superimposed signal on the mains network. A meter sends an
acknowledgement signal back to the central controller and may perform some
function
dependent on the message received.
2o Two well known problems that need to be overcome by power line
communication
systems are the noisy environment and potentially large signal attenuation.
Various
reading techniques and communication protocols have been developed to address
these
problems, for example using meters as digital relays to enable communication
from the
central controller to each of the meters. Examples of power line communication
systems
using signal repeaters are described in European patent publication No. 0 201
253 B1 and
international patent publication no. WO 95/01030.
Advances in meter technology have provided improved functionality. For
example,
meters may communicate by a wireless link with other meters and with network
controllers
3o to perform various functions. An example of such a system is described in
international
patent publication no. WO 97/29466. A problem with such meters is the
additional costing
complexity resulting from the wireless communication. Also, as radio spectrum
becomes
increasingly in demand, the use of wireless communication from potentially
millions of
sources may not be commercially viable in many cases.
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A mains network provides an extensive existing infra-structure. Furfiher
exploitation of the existing mains infra-structure would be advantageous. For
example,
increased functionality, both in terms of control and monitoring of the power
network may
be achieved, including improved metering and providing additional services to
customers.
As a consequence of deregulation in the power supply industry in many
countries,
achieving reconciliation of power supplied and determining the power used and
network
losses has become a significant problem. The problem arises principally on the
low
voltage distribution network, where more than one retailer exists as well as a
separate
1o lines company. There is a need for improved measurement of network losses
so that
accuracy in power reconciliation can be improved.
It is thus an objecfi of the present invention to provide a power line
communication
system and method that provides additional functionality for one or both of
power network
15 management and the provision of network services, or at least to provide
the public with a
useful alternative.
Definitions
2o Computer controller- computerised apparatus for managing communications
within a mains communication network. The computer controller typically
includes one or
more suitable computer processors, a suitable operating system and suitable
application(s). For example and without limitation the computer controller may
be a
computer or network of computers operating Windows NT~ or Linux.
2$
Intelligent device- a device that includes a computer processor and associated
memory and a communication interface allowing the device to perform at least
some
communication functions. Intelligent devices include, without limitation, a
relay or meter
including a computer processor, memory and communication interface.
Power usage profiling - identification of patterns of use of power at a
specific site
or by a specific device that is connected to the mains communication network.
Utility - a retail supplier of power to customers.
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Summary of the Invention
According to a first aspect of the present invention, there is provided an
intelligent
device for a power line communication system that has stored in memory
information
uniquely specifying the intelligent device's identity, includes an interface
for data
communication with a power line and is operable to perform a configuration
process
including the steps of using said interface to:
a) detect data of a first data type through the interface and in response
thereto extract
from the data of a first data type and record in memory identity information
for the source
to of the data of a first data type and generate on said interface data of a
second data type
that have as a destination address the source of the data of a first data type
and includes
the information specifying the intelligent device's identity;
b) detect data of a second data type that have the intelligent device as a
destination
address and in response thereto extract from the data of a second data type
and record in
15 memory the identity of the source of the data of a second data type and
generate on said
interface data of a third data type that includes information identifying the
source of the
data of a second data type and the information specifying the intelligent
device's identity;
c) detect data of a third data type and in response extract there from and
record in
memory information identifying the source of the data of a third data type
associated with
2o the information identifying the source of the data of a second data type
included in the
data of a third data type and generate data on said interface containing the
information
identifying the source of the data of a third data type, the information
identifying the source
of the data of a second data type included in the data of a third data type
and the
information specifying the intelligent device's identity.
Preferably, the data generated in step c) is addressed to at least one source
of
data detected in step a).
Preferably, the steps of extracting and recording in step c) are only
performed for
3o data of a third data type that are addressed to the intelligent device.
Preferably, the address of the intelligent device is the same as the
information
specifying the intelligent device's identity.
Preferably, the intelligent device is further operable to determine an
indicator of the
quality of communication between itself and the source of detected data and
rank identity
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4
information recorded in memory dependent on said indicator.
Preferably, the intelligent device is operable to in response to defection of
data of a
second data type generate data of a fourth data type including as a
destination address
the source of the data of a second data type and the configuration process may
further
include the steps of using said interface to detect data of a fourth data type
that have the
device as a destination address and in response thereto generate on said
interface data
of a first data type.
1o Preferably, the intelligent device is operable to ignore detected data of a
second
data type that were generated by a source that was recorded in memory as a
source of
data of a first data type in in step a).
Preferably, the intelligent device is operable to use said interface to
generate data
15 of a first data type and wherein the data of a first data type include a
counter, wherein step
a) further includes identifying the value of the counter of any data of a
first data type
detected, associate the value of the counter with the recorded identity
information for the
source of the data of a first data type, increment the value of the counter
and allocate the
incremented value to a counter in any data of the first data type generated by
the
2o intelligent device as a result of data received from the source of the data
of a first data
type.
Preferably, the intelligent device is operable to ignore detected data of a
first data
type that has a counter value more than a threshold value. Preferably, the
threshold value
2s is a value related to the value of the counter from the last items) of data
of the first data
type received. More preferably, the threshold value is one more than the value
of the
counter from the last data of a first data type received.
Preferably, the data of a third data type include a counter and the data
generated
3o in step c) is in the form of data of a third data type and the intelligent
device associates the
value of the counter with the information recorded in step c) that identifies
the source of
the data of a third data type and the intelligent device increments the
counter when
generating data of a third data type in response to detection of data of a
third data type in
step c).
Preferably, the intelligent device is operable to also generate data onto said
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interface otherwise than in accordance with the configuration process.
Preferably, the intelligent device is operable to generate text messages onto
said
interface.
Preferably, the intelligent device is operable to receive control messages
through
said interface and communicate control messages to a power distribution board
to
facilitate load shed dependent on said control messages.
to According to a second aspect of the present invention, there is provided a
power
line communication system including a plurality of power lines in
communication with a
controller through a power line modem, each power line having a plurality of
intelligent
devices as described in the preceding paragraphs in communication with it,
wherein the
controller is operable as one of said plurality of intelligent devices and is
also in
15 communication with a computer controller that is operable to receive data
from the
intelligent devices via the controller and to send data to the intelligent
devices via the
controller.
Preferably, data other than configuration data, which is generated onto a
power
20 line by an intelligent device or the controller, includes a destination
address and an
intermediate address, wherein each intelligent device monitors communications
on the
power line and if the destination address of communications matches
information
identifying the source of the data of a second data type included in the data
of a third data
type that was recorded by an intelligent device in accordance with step c),
then that
25 intelligent device regenerates the data, but with the intermediate address
field comprising
the information identifying the source of the data of a third data type
recorded in step c)
that is associated with the information identifying the source of the data of
a second data
type included in the data of a third data type that matches the destination
address.
3o According to a third aspect of the present invention, there is provided a
power line
communication system including a plurality of intelligent devices in
communication with a
power line operable to monitor energy usage at a site and communicate usage
data onto
the power line and a controller also in communication with the power line,
wherein each
intelligent device maintains a routing table identifying a first set of other
intelligent devices
35 downstream of it relative to the controller that it can communicate with
directly and
identifying a second set of other intelligent devices downstream of it
relative to the
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controller that it can communicate with through one or more of the first set
of other
intelligent devices.
Preferably, the routing table further identifies a third set of other
intelligent devices
upstream of it relative to the controller that it can communicate with
directly.
Preferably, the routing tables are formed by an interrogation process
initiated by
the controller that requests the intelligent devices that can receive data
directly from the
controller over the power line to respond with information identifying what
other intelligent
to devices the intelligent devices that can receive data directly from the
controller over the
power line can communicate with either directly or through further intelligent
devices,
wherein the intelligent devices that can be communicated with through said
further
intelligent devices are identified through an interrogation process conducted
by said
further intelligent devices.
i5
Further aspects of the present invention may become apparent from the
following
description, given by way of example of preferred embodiments only and with
reference to
the accompanying drawings.
2o Brief Description of the Drawings
Figure 1: shows a diagrammatic representation of a power line communication
system in accordance with an aspect of the present invention.
25 Fi__gure 2: shows a block diagram of a meter in accordance with the present
invention.
Figure 3: shows a block diagram of a controller in accordance with the present
invention.
30 Fi ure 4: shows a representation of the information and functions performed
by the
database in the communication system of Figure 1.
Figures 5a. b: show diagrammatically an example of configuration packet
communications in the communication system of Figure 1.
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Detailed Description of the Drawincts
Figure 1 shows a schematic representation of a mains communication and control
network 100 in accordance with the present invention. The mains communication
and
control network 100 includes a mains communication network 1. This forms the
lower
levels of a hierarchal communications network topology that supplies power to
customer
sites 8a-i that are connected to the mains communication network 1 and also
forms a low
voltage sub-network of a larger mains network 101, which typically includes a
high voltage
network that supplies high voltage three phase power to the mains
communication
network 1.
to
A computer controller 2 provides the upper levels of the communications
network
topology. The computer controller 2 includes, in this example of a preferred
embodiment,
a central control unit 2A, which communicates with the mains communications
network 1
through a communications controller 2B. A database 2G is provided for the
central control
unit 2A, containing the necessary control information for the mains
communication
network 1 and also containing power use information from the mains
communication
network 1. Customer billing may be managed by a billing system 2D.
The mains communication network 1 shown in Figure 1 may be one low voltage
2o sub-network of many in the wider mains network 101. The communications
controller 2B
may communicate with a large number of such sub-networks.
The mains communication network 1 includes a controller 3, which is suitably
located at a transformer 4. The transformer 4 may receive high voltage power
from the
mains network 101 and output low voltage power to the rest of the mains
communication
network 1. The computer controller 2, particularly the communications
controller 2B may
communicate with the controller 3, through for example a wireless
communication channel
5. Other communication channels may be used.
3o The controller 3 includes three power line modems 6, one modem per phase 7a-
c
of the mains communication network 1 on the low voltage or demand side of the
transformer 4. The power line modems 6 may, for example use a power-line
carrier
employing FSK modulation with a carrier frequency in the range of 67kHz to
87kHz. Each
phase 7a-c feeds into a number of the customer sites 8a-i. Each of the
customer sites
8a-i includes a meter 9, with each meter 9 being an intelligent meter. Some
further
customer sites connected to the phases 7a-c may not have intelligent meters,
but these
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s
are unimportant to the operation of the present invention and therefore are
not shown in
the accompanying drawings or described herein.
The mains communication network 1 may include one or more micro-generation or
energy storage facilities 14. In Figure 1, two micro-generation/energy storage
facilities 14
are shown. The micro-generation/energy storage facilities 14 may represent for
example,
small hydro-generators, solar-generators, wind-generators or fuel cells and
may be
located at any one or more of the customer sites 8a-i or be separate from the
customer
sites 8a-i. The micro-generation/energy storage facilities 14 each include a
meter 9A.
The communication functions of the mains communication and control network
100 are now described with reference to the example function of meter data
collection.
The controller 3, through the appropriate power line modem 6, polls a meter 9
for the
power consumed at a site 8a-i since the last time the associated meter 9 at
the site was
polled. The meter 9, which includes its own transmitter, then sends
information indicating
the power consumed to the controller 3, where it is buffered until requested
by the
computer controller 2. The central control unit 2A then initiates a
communication session
with the controller 3 through the communications controller 2B, which receives
the
buffered information through the communication channel 5. The central control
unit 2A
2o then updates the database 2C with the newly received information. The
billing system 2D
may then generate a bill at a required time, based on the information stored
in the
database 2C. In addition, the updated billing information may be sent by the
central
control unit 2A to the meter 9 for display on the customer display unit 10.
Each meter 9 used in the mains communication network 1 is an intelligent power
meter. Typically, the meter 9 will replace any existing electro-mechanical
meter at each
customer site 8a-i. A block diagram representation of a meter 9 is shown in
Figure 2. The
meter 9 includes a computer processor 900, which may for example be a Dallas
5002FP,
8051 compatible processor. External memory 901, which may be SRAM, is provided
in
communication with the processor 900 and the operations of the processor 900
are timed
by a clock 902. The meter 9 also includes EEPROM 903. The meter 9 may
communicate
with optional external devices, through a serial communications interface 904.
The meter
9 may also include its own display 905 for communication of information to
users. A
power line modem 906 allows the meter 9 to communicate with the controller 3
through a
phase of the mains communication network 1.
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9
The meter 9 records the power usage using an energy measurement module 907.
For example, the energy measurement module may be a SAMES SA9102C energy-
metering integrated circuit, available from South African Micro-Electronic
Systems,
Pretoria, South Africa. The resulting data is stored in memory 901 using an
encryption
algorithm. Bidirectional energy measurement modules are also available from
South
African Micro-Electronic Systems for use in a bidirectional meter.
The EEPROM 903 contains the starting meter count, the number of pulses for
each kilowatt hour, the number and type of connections to the meter, type of
devices
to attached to the serial communications interface 904, and the functions of
any additional
outputs. Identification information for the meter 9 that identifies the meter
from other
meters, referred to herein as an electronic serial number, is also stored in a
protected part
of the EEPROM 903.
The computer processor 900 has precedence over communications while the
meter reading is accumulated in hardware. A hardware register (not shown)
provided for
the meter reading is read by the computer processor 900, then reset when the
communications channel is not in use.
2o When the central control unit 2A sends a poll to a meter 9, the poll
includes a
specification of the current time. Upon receipt of a time packet from the
central control
unit 2A, the communications controller 2B sets its clock if it differs from
that in the time
packet. The time packet will be queued together with all the other packets for
sending to
the controller 3 when the connection is established. During the time the
packet is queued
?5 for transmission, the current system time will continue advancing.
Therefore, when the
connection is established, and the time is forwarded to the controller 3, the
time fields of
the packet will be updated to the current system time.
Data is requested from each meter 9 by the controller 3 periodically, for
example
30 once every several hours. Contained in the request for data packet
(initiated by the
controller) is the correct time. The meter 9 will therefore be refreshed with
the correct time
periodically. The variable transmission delay to the meters 9 should also be
accounted
for. Since each message is acknowledged, the round trip time divided by two
can be
calculated, and may be referred to as the latency. The controller 3 sends each
individual
35 meter 9 a time signal corrected by the latency applicable to that meter 9.
The latency
used for a current transmission may be based on historical information or a
further
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communication from the controller 3 may cause the meter 9 to advance its time.
One of the optional external devices that may be connected to the meter 9
through
the serial interFace 904 is a customer display unit 10. The customer display
unit 10 may
have increased display capabilities and display information to the customer,
such as the
amount due since last payment, recent consumption information and the total
meter
reading. In addition, messages sent from the central control unit 2A or from
elsewhere to
the meter 9 may be displayed on the customer display unit 10.
to Figure 3 shows a block diagram of a controller 3. The controller 3 includes
a
processor 300 for controlling the three power line modems 6a-c through serial
communication buses and manages the receipt, transmission and storage of
information
from the various meters 9 and from the communications controller 2B. A memory
301 is
provided to store a routing table (see herein below) and a communications
interface 302,
suitably a wireless communications interface, is provided to allow
communication with the
communications controller 2B.
The communications controller 2B is a real time processing system that links
the
central control unit 2A and database 2C with each controller 3 and
subsepuently each
2o meter 9. The communications controller 2B may communicate with the central
control unit
2A via a serial communications link or Ethernet using TCP/IP. Where the meters
9 in the
mains communication network 1 can generate alarms, the communications
controller 2B
preferably receives the alarm signals and forwards these on to the central
controller 2A.
The communications controller 2B includes an interface to communicate with the
controller 3, which in Figure 1 is a wireless interface, although a leased
line modem,
standard dial up modem, or fibre-optic modem may be used instead. As stated
herein
above, the communications controller 2B preferably communicates with a
plurality of
controllers 3.
3o The central control unit 2A stores an operating system such as Windows NT~.
It
also includes appropriate software to manage the database 2C. The central
control unit
2A performs essentially two main functions, the first being to manage the
database 2C
and the second to control the functions of the mains communication network 1.
Figure 4 shows a representation of the functions of the database 2C. Power
usage data from each meter 9, which has been received through the controller 3
and
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11
communications controller 2B, is stored in memory. The database 2C may include
an
analysis function to analyse the raw power usage data and provide specific
output results.
A query functionality may be provided to allow the billing system 2D to
retrieve either or
both of the raw power usage data or results of the analysis function. In
addition, the
database 2C may store the routing tables that dictate the path that data
communications
take through the mains communication network 1. The formation and use of the
routing
tables are described in more detail herein below. The central control unit
uses the routing
tables when sending out information to the meters 9. Database 2C may also
include the
location and technical specification of each controller 3 and each meter 9.
The controllers
l0 3 and meters 9 may be identified in the database 2C by their electronic
serial number,
which is used by the central control unit 2A to distinguish between the
various controllers
3 and meters 9 and also to allow each controller 3 and each meter 9 to
identify the
information communicated within the mains communication network 1 that is
destined for
it. The location information may be used for the purposes of billing, repair
of faults and for
15 intelligent relaying.
The computer controller 2 may perform statistical analysis of the usage data,
which may be periodically updated, to provide power usage profiling. The power
usage
profiling may assist a power utility in the estimation of demand, for
instance, by profiling
2o supply from particular distribution transformers 4 to their respective
mains communication
network 1. The power usage profile for the customers of a utility supplied
from a particular
grid exit point provides a current inventory of energy usage. The utility may
therefore
determine in an almost real-time manner what its bill for supply from that
grid point should
be.
Power usage profiling may also benefit a utility in terms of asset management.
Specifically, the power usage profile obtained from the controller 3 provides
information on
the load profile for its associated transformer 4 and phases 7a-c. Changes in
usage
pattern can be used to detect certain events, such as loss of supply to an
area caused by
3o a distribution fault, accidental disconnection of individual premises
and/or to indicate
tampering/fraud. It also provides the utility with accurate, monitored,
quality of supply (i.e.
outages) information. Such information is of use for scheduling asset
maintenance,
upgrades and replacement. Preventative maintenance may be assisted by
monitoring the
quality of network assets. This may be achieved by measuring changes in power
line
communication quality through the network. Information about communication
quality is
retrieved periodically. Specifically, bit error rate tests may be performed
routinely during
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12
auto-configuration of the network and packet error rate tests can also be
performed on
request. By identifying trends of increasing error rates over time, ageing
network assets
can be identified.
The above described functionality, together with many other functions that may
be
provided, for example by other external devices connected to the meter 9,
require bi-
directional communication between the mains communication network 1 and
computer
controller 2 and within the mains communication network 1. An important aspect
of the
present invention is the method of communication between these two networks
and within
1o the mains communication network 1. To establish the communication channels,
a number
of routing tables are formed and stored in the computer controller 2 and mains
communication network 1. The routing tables identify the various paths that
communications may take between the computer controller 2 and mains
communication
network 1, in particular between the central control unit 2A and each meter 9.
Formation of Routing Tables
The central control unit 2A and the controllers 3 are the primary controllers
in
respect of the formation of routing tables. The central controller 2A uses a
priori
2o knowledge of the network topology to separate the various meters 9 into
several sets,
each set defined by all the meters 9 and their attached optional devices
connected to a
single phase of a particular transformer 4. The controller 3 is responsible
for forming the
routing table for the phases in which it is in communication with. This
subdivision may
reduce the time to create the routing tables and facilitate the recreation of
sections of the
logical network defined by the routing tables to overcome local communication
problems.
Recreation of the logical network may be achieved by a controller sending out
WCHM
packets (see herein below) and waiting for responses in the same way that the
logical
network is first created.
3o Referring now to Figure 5, a diagrammatic representation of the packet
flows for
establishing the routing tables is shown. Upon initialisation, or upon
prompting by the
central control unit 2A, the controller 3 generates and transmits to each of
its serial
communication buses a packet of a first type, referred to herein as the
WHO CAN HEAR ME (WCHM) packet. The power line modems 6, which are intelligent
modems, each receive the WCHM packet and in response thereto send back to the
controller 3 a packet of a second type referred to herein as an I HEAR YOU
(IHY)
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packet. The iHY packet indicates to the controller 3 that a modem is present
on that serial
communication bus and includes a field containing the electronic serial number
of the
modem. The controller 3 records how many power line modems 6 it is in
communication
with, their electronic serial number, and on which serial bus they are
located. The
controller 3 may then collate the IHY packets and send a packet to the central
control unit
2A of a third type referred to herein as an I HEARD THESE (IHT) packet that
specifies
the electronic serial number of each modem.
The controller 3 may then send a packet of a fourth type, referred to herein
as the
to WHO CAN YOU HEAR (WCYH) packet. The WCYH packet prompts each power line
modem 6 to generate a WCHM packet on its output, which represents one of the
phases
7a-c of the mains communication network 1. The WCHM packet includes the
electronic
serial number of the power line modem 6 that sent the packet. The power line
modem 6
may optionally have the same electronic serial number as the controller 3 to
which it is
15 connected. Optionally, the power line modems 6 (and meters 9) may
automatically
generate, after a predetermined delay, a WCHM packet after receipt of a WCYH
packet.
Each meter 9 at each customer site 8a-8i monitors the phase to which they are
connected and upon receipt of a WCHM packet by a meter 9, the meter 9 enters
the
20 electronic serial number in the WCHM packet into its routing table as a
primary parent i.e.
a device from which it can receive communications directly. The meter 9
responds to the
WCHM packet with an IHY packet addressed to the source of the WCHM, which in
this
case is a power line modem 6. The IHY packet includes a field containing the
electronic
serial number of the meter 9 that received the WCHM packet. The power line
modems 6
25 receive the IHY packets from the various meters 9, collate these and send
notification to
the controller 3 identifying each meter 9 that responded to their respective
WCHM packet
in an I HEARD THESE (IHT) packet, which includes the electronic serial numbers
contained in all the IHY packets received. The controller 3 then enters in its
routing table
the electronic serial numbers from the IHT packet as a primary child i.e.
devices to which
3o it can send information directly using it associated power line modems 6.
Referring now to Figure 5b, the controller 3 then sends out a WCYH packet to
each primary child meter through the appropriate power line modem 6. Each
primary
child meter 9 acknowledges receipt of the WCYH packet and also generates a
WCHM
35 packet on its output, which is a phase from the transformer 4. In an
alternative
embodiment, each meter 9 may automatically generate a WCHM packet after
receiving
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14
such a packet. Each meter 9 that receives this WCHM packet returns an IHY
packet.
Each primary child meter 9 records in its routing table as primary children
the electronic
serial number of all meters that returned an IHY packet to it and each meter 9
that
received a WCHM packet adds the primary child meter as a direct parent in
their
individual routing table. Each primary child meter 9 also sends through its
power line
modem 906 an IHT packet to the controller 3 through the power line modem 6
indicating
the electronic serial number contained in IHY packets that it received. The
controller 3
then adds the electronic serial number as secondary children in its routing
table (i.e.
meters that can be communicated with via another meter logger). The controller
3 also
to associates each secondary child with each of the primary children that sent
an IHT packet
containing the electronic serial number of that secondary child. This enables
the
controller 3 to identify to which primary child information should be sent in
order to reach a
particular secondary child.
Each meter 9 identifies two or more paths back to the controller 3. To achieve
this, each meter 9 records the electronic serial number of any meter from
which it received
a WCHM packet. The source of the first WCHM packet received could be
identified as
Parent 1. The source of the second WCHM packet received could be identified as
Parent
2. Similarly, the sources of any subsequent WGHM packets could be recorded as
2o Guardians. The Parent and Guardian meters thus identified represent
alternative paths
back to the controller 3.
The above configuration process continues, with the controller 3 sending WCYH
packets to each secondary child through the appropriate primary child in order
for it to
identify its tertiary children. The controller 3 then sends WCYH packets to
the tertiary
children through the primary and secondary child meter loggers and so on until
all meters
9 have been entered into the routing table of the controller 3. Each meter 9
maintains its
own routing table, extracting the electronic serial numbers from IHT packets
received from
its direct children and associating the serial numbers with its direct
children. Thus, each
3o meter knows all the other meters with which it can communicate directly
(its parents and
primary children) and also knows all the meters it can communicate with
indirectly through
each of its primary children.
The IHT packets may be addressed to the parents of a meter or simply
transmitted
onto the power line. If the IHT packets are addressed, recipient parent meters
may simply
record the identity information of the secondary children associated with the
identity
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information of the sender of the IHT. The recipient meters then forward the
IHT packets to
their parents, who will forward the packet to their parents, associating the
identity
information contained in the packet with their relevant primary child and so
on until the
controller 3 receives the packet. If the IHT packets are not addressed, then
each recipient
5 meter compares the source of the IHT packet to all of its children and adds
the identity
information in the IHT packet only if there is a match. The recipient meter
associates the
identity information in the IHT packet with the child that matched the source
of the IHT
packet and then addresses the IHT packet to its parents.
1o To avoid continuous loops in the configuration process, each meter 9
ignores IHY
packets that it receives containing the electronic serial number of any meter
that is listed
as a parent. Also, should the identity information in any IHT packet match a
parent of the
recipient meter or itself, the IHT packet is ignored.
15 In one embodiment, when the controller 3 transmits a WCHM packet, it
immediately follows this with a bit error rate test. Each meter 9 will receive
the WCHM
packet and bit error rate test and respond with an IHY packet and a quality
indicator
based on the bit error rate test. Each meter 9 also sends a bit error rate
test when it
sends a WCHM. Thus, the controller 3 and each meter 9 can record for each
meter that it
2o is in communication with, the quality of the communication path to that
meter. This
process allows each meter to rank the various communication paths to both its
parents
and its children, using the highest quality communication path first. If the
communication
path of highest quality should fail, for example by failure to receive an
acknowledgement
of receipt packet, the controller 3 or meter 9 uses the next highest quality
communication
path, if one exists.
The network configuration packets WCHM, IHY, WCYH and IHT are used to
create a logical power-line network structure. At least selected of these
configuration
packets contain the electronic serial number of the controller 3 and this
electronic serial
3o number is relayed by each meter 9. For example, each WCHM packet contains
the
electronic serial number of the controller 3. Where a meter sends the WCHM
packet, it
determines the electronic serial number from the WCYH packet that it received.
Every
meter 9 stores the electronic serial number of its controller 3 in EEPROM 903.
This logical network, the structure of which is determined by the parent and
child links in
the routing tables, will be updated periodically to ensure that the logical
network remains
current.
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16
The system may also recreate the logical network on the occurrence of one or
more particular events. Any device within the mains communication network 1
may
transmit onto its associated phase a packet referred to herein as a
NETWORK CHANGED (NC) packet. Typically, it will be the meters 9 at any of the
customer sites 8a-i that will transmit a NC packet. During the lifetime of a
logical network
between periodic updates, the network may change, for example due to routine
maintenance (e.g. a street may be switched to another phase of a transformer)
or by
adding or removing meters 9. If this happens the new meter, or one that was
previously
to connected to a different controller, will detect the traffic on the network
and notice a
different controller electronic serial number in the packets communicated over
the phase
to which it is connected. When this happens, that meter will send a NC packet
onto the
phase and meters 9 that detect the NG packet, relay the packet to the
controller 3, which
initiates a recreation of that part of the network.
The variable noise and attenuation on the mains network has significant
consequences for meter communications. Specifically, meters that could be
contacted at
the time the logical network was last configured (either at a pre-programmed
time or as a
result of a NETWORK_GHANGED packet) may not necessarily be contactable at some
later instant. Maintaining communications between the central control unit 2A
and each
meter 9 may be particularly important for real time control of the mains
communication
network 1, for example to provide for load shed.
The central control unit 2A maintains a list of all contactable meters 9. To
achieve
35 this, the controller 3 sends out PING packets to individual meters 9 in its
routing table, at
times when there is no other network traffic, and monitors the responses to
build a list of
the currently contactable meters 9. Meters 9 that were in the logical network
when it was
created but can't now be contacted are therefore identified. Should they
remain out of
contact using the current routing table for a certain predetermined period, a
local network
3o recreation is initiated by the controller 3. In addition, if a meter 9 is
unable to contact
another meter 9 (determined by failure to receive an acknowledgement or other
return
information) after a predetermined number of tries, for example three attempts
using all
available paths, an error is generated by the transmitting meter and sent to
the controller
3. Should the meter remain out of contact for too long a period, a local
network recreation
35 is initiated by the controller. .
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17
A manual over-ride may be provided to allow for the recreation of the logical
network on demand and to specify fixed communication channels within the
logical
network. For example, the central control unit 2A may send packets referred to
herein as
YOU HEARD_THESE (YHT) and YOUR_PARENT IS (YPI). These packets respectively
identify the meter's children and its parent or parents and guardians.
The quality of communications between meters can be determined by use of a
packet error rate test. The central control unit 2A can request a controller
to initiate a
packet error rate test between any desired meters. A known signal is
transmitted,
to including a signature identifying it as a packet error rate test. The
recipient meter 9
records the error rate and forwards this to the controller 3. The controller 3
in turn
forwards the result to the central control unit 2A. Should the packet error
rate test results
be unacceptably low, the options available to the central control unit 2A
include initiating a
local network recreation or manually reconfiguring the meters routing tables
using the
15 YHT and the YPI packets. Gommunication quality indicators other than a
packet error
rate test may be used if required.
When the logical network is recreated, the previous logical network is saved
as a
backup network. This allows reconstruction of a previous working logical
network should
2o the new network be inoperable for some reason.
In the foregoing example of formation of routing tables, only a two level
table in the
child direction is formed in each meter - its direct children and all the
meters that the
direct children can communicate with. The meter does not know whether any
child is a
25 secondary, tertiary or higher level child. Similarly, the controller 3 and
central control unit
2A do not know where each meter is in the hierarchy apart from the primary
children of
the controller 3. Also, only the direct parents are recorded. This embodiment
is
preferable as reducing the memory requirements for the routing tables and
reducing
network communications for establishing the logical network.
In an alternative embodiment, a counter may be added to the IHT packets, which
is incremented each time the IHT packet is relayed to a parent. Therefore,
each meter
knows how far away each meter is in terms of transfers through other meters.
The IHT
meters may also include a quality indicator that provides an accumulated
indication of the
quality of communication between meters, taking into account the
retransmissions that
take effect. This information can be associated with each child and used by
the mefiers
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18
and the controller that receives the IHT packet to choose a path to a
particular meter.
Each meter may then, either know how many steps away each meter is or
alternatively
know the meters that are one, two, three, four and five steps away, with those
that are
more than five steps away being grouped together.
Also, a counter may also be associated with each WCHM packet, which is
incremented each time a meter sends out a new WCHM packet. A meter may ignore
a
WCHM packet if the counter in it is too much higher than the counter in the
last WCHM
packet they received. For example, to achieve an efficient routing table, if
the counter in a
to WCHM packet is two or more values higher than the counter in the last WCHM
packet, it
may be ignored.
The WCYH packets may further accumulate in order the electronic serial numbers
of all the meters through which it 'travelled' so that each meter can record
fully the path
15 back to the controller 3, or at least more than one step back to the
controller 3.
Data Communication
During operation, each meter 9 listens to all communications on the phase 7a-c
to
2o which it is connected. Each packet transmitted onto the network by a device
contains the
electronic serial number of the source of the packet, the electronic serial
number of the
device that is the final destination for the packet, and an intermediate meter
electronic
serial number if a relay is required. The packet is received by a meter 9
designated as the
intermediate one (if one is designated), and that meter will change the
intermediate meter
2s electronic serial number to the next meter in the path to the device having
the destination
electronic serial number (using information stored in its routing table) and
transmits the
modified packet.
The meter identifies the appropriate route over which to transfer a packet by
a
3o software routine that examines its routing table upon receipt of a message
destined for
another meter or for the controller. The destination of any message is
dictated by an
electronic serial number field. If the message destination is the controller
3, then the
meter 9 forwards the message to its parent. The parent repeats the process and
forwards
the message to its parent and so on until the message is delivered to the
controller. If the
3s message destination is another meter, the meter that received the message
examines its
routing table to see if the destination meter is a child. If so, the routing
table is further
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19
examined using a software routine that identifies the appropriate intermediate
destination
of the packet. This routine works backwards from the destination electronic
serial number
to identify its parent, and then the parent of that parent and so on until it
is one level below
the meter that has received the message. This may only ever be a two stage
process if
the meter does not know how far away other meters in its routing table are.
The packet is
then despatched to this intermediate destination meter and the process
repeated.
Each packet is sent by a particular device in the network to an intermediate
meter
up to three times before flagging an error and giving up on that
communications path. If
l0 the communications fail on an upstream path (i.e. the message is being
relayed to the
controller) then the meter will try to relay the message through its second
parent. Should
this route also fail, then the message will be relayed through one of the
guardian meters.
If this also fails and the communications don't get through to a meter one
level upstream
(i.e. closer to the controller) the meter is designed to attempt to jump over
the meter just
15 upstream and attempt to communicate with one further upstream. This is done
by
examining the routing table and identifying the parent's parent (if this
information is
available) and relaying the message through fihis meter. Should communications
fail on
the downstream path (i.e. the message is being relayed from the controller)
the meter is
designed to attempt to jump over the meter just downstream and attempt to
communicate
20 with one (two levels) further downstream. This is done by examining the
routing table and
identifying the intermediate electronic serial number that would have been
used by the
meter that wasn't responding, and relaying the signal directly to this
intermediate
electronic serial number.
2s If all else fails (on either upstream or downstream paths), a meter 9 may
request
help, using a packet referred to herein as a HELP TRANSPORT packet, from any
meter
that can provide an alternate path to the destination meter or controller.
Responses to
this HELP TRANSPORT packet are examined and a choice is made as to which of
these
to use as the next intermediate meter. The packet will be forwarded to this
meter, by
3o updating the intermediate meter electronic serial number to match that in
the selected
response and that meter will take over the responsibility of getting the
packet to the next
intermediate or final destination meter. The sending meter may optionally
update its
routing table to include as a child the new intermediate meter in the path to
the destination
meter to which it was originally trying to send.
3s
The data section of the packets should be encrypted, but the data section
control
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word should not be encrypted. The data section control word must be
immediately
recognisable to allow alarm traffic to take precedence over other types of
information, and
to allow the time data to be updated as it is being transferred from meter to
meter.
5 Some mains communication networks may not have a controller 3, perhaps due
to
being of such a small size that a controller can not be justified. In Figure
1, a
diagrammatic representation of such a network is referenced 1A. The mains
communication network 1 may be used to relay data to the mains communication
network
1A. One or more specific meters 9, for example the meter 9 at customer site 8i
acts as a
10 relay to the mains communication network 1A, in particular to one or more
meters 9B that
can communicate with the meter at site 8i. The link between networks may be
provided
via a radio or dial-up telephone connection, in which case the meters
designated as the
link between networks are provided with the appropriate radio or telephone
modem 11.
The routing tables of the link meters and of the meters in the subsidiary
network are
15 manually configured using the network configuration packets described
herein above
YOU HEARD THESE (YHT) and YOUR PARENT IS (YPI).
To increase communication reliability, the packets are broken up into small
pieces
and reassembled by the destination meter or by the controller modem. The size
of the
2o packets is an important design variable for any mains communication network
and size
selection typically represents a trade-off between reliability and efficiency
of
communication.
To determine the maximum permissible packet size, an experimental method may
be used. Over a period of time sufficiently long to represent a normal range
of conditions
over the network, which may be as long as several months and at various times
of the day
and under a variety of weather conditions, the mains communication network is
sounded
using meters equipped with bit error rate software. One meter continuously
transmits
while the other meters operate in receive mode. A known pattern is sent and
time-
3o stamped errors are stored by the receivers. These error files are then
analysed to
determine that the noise on the channel is bursty in nature and this may be
used to
determine the optimum packet size.
Differing length packets are used to convey information, with very short
packets
reserved for high priority messaging and longer packets up to the maximum
length used
for low priority messaging. For example alarm messages and load shed control
signals
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21
(see herein below) may take the highest and second highest priority and have
the lowest
packet length.
Uaqradinq_of Software
A potential disadvantage of intelligent meters is the difficulty of upgrading
software
to enhance functionality. Typically in prior art systems this can only be
achieved by
physically visiting each site, temporarily taking the meter out of service and
downloading
new software into the meter. The meters 9 of the present invention are
provided with a
to computer processor 900 capable of In-Application-Programming (IAP) to
enable remote
software updates. The STMicroelectronics uPSD3234A microcontroller, available
from
STMicroelectronics of Geneva, Switzerland, supports IAP and includes dual
banks of flash
memory and a control register to allow its 8032 controller to run from one
flash bank while
erasing and updating the other bank. More than one version of the meter
software can be
stored in each meter 9, so that it is possible to drop back to an earlier
version of the
software if problems arise. The capability of remote software updates also
permits the
change of modem carrier frequencies and baud rate to enhance message transfer.
Network Loss Measurement
As a consequence of deregulation in the power supply industry, reconciliation
of
power supplied, power used and network losses has become a significant
problem. The
problem arises principally on the low voltage sub-network, where more than one
retailer
exists as well as a separate lines company. An additional meter, a low voltage
master
meter 12 may be provided to solve this problem. Specifically, the low voltage
master
meter 12 is a device placed between the distribution transformer 4 and the
controller 3
that measures the total power supplied from the transformer 4 over all three
phases. This
power supply figure may be metered, for example, on a half-hourly basis and
accumulated
results forwarded to the controller 3 on a periodic basis. When all use data
from the
3o meters 9 and the power supply figure from the low voltage master meter 12
has been
returned to the central control unit 2A, the database 2C can be used to
determine line loss
as the difference between power supplied and power used.
In addition, the efficiency of the transformer 4 may be measured. The low
voltage
master meter 12 and a high voltage meter 13 with pulse output remotely monitor
distribution transformer efficiency. Specifically, the high voltage meter 13
is placed on the
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22
primary of the distribution transformer 4. It reads input 3-phase power on a
half-hourly
basis. The low voltage master meter 12 records total power output from the
transformer
on a half-hourly basis. At fixed intervals the controller 3 requests the half-
hourly readings
from both the high voltage meter 13 and the low voltage master meter 12 and
stores these
readings for subsequent forwarding to the central control unit 2A and database
2C. The
database 2C is then able to use these readings to determine transformer
efficiency.
Private-Side Applications of Mains Communication Network
1o The mains communication network described herein provides increased
flexibility
in the control of the power network and in the provision of additional
services to
customers. Examples of new applications for customers are provided below.
The mains communication network 1 may monitor the status of various devices
is and machines. This is achieved by connecting a serial interface 904 of a
meter 9 to the
device or machine. For domestic premises, an intelligent PLC relay can be used
to
automate a device or monitor an essential device such as a dialysis machine in
the home.
For hospital or rest-home applications, an intelligent PLG relay can be used
to remotely
monitor (for example from a nurse's station) the status of an essential piece
of mains-
2o powered equipment at a patient's bedside.
For residential "community" developments, the meters 9 may be used to automate
the front gate and other limited or restricted access points such as a pool
complex and for
control of external lighting without the need for individual wiring to each
dwelling. In one
2s embodiment, a body-corporate residential development may have "always-on"
web
access in which all key control points (e.g. front gate and pool gates) have a
web-cam in
communication with a phase 7a-c, which finks back to the residential
development's
central office, which is also on a phase 7a-c. Residents could then access the
central
office through the web to view the web-cam picture and grant or decline
access. The
30 caretaker or manager of the complex would have the ability to over-ride
access or time-of
day controlled features by accessing the central office via the web. An
advantage of this
system is that individual wiring to each premises is not required.
The meters 9A in Figure 1 may be dual meters. The meters 9A facilitate the
3s monitoring and control of energy storage devices and of embedded generators
so that
their energy is made available to the grid at appropriate times. This control,
when used in
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23
combination with power usage profiling, allows improved management of the
energy
supply within the entire mains communication network 100. A benefit of this
may be a
reduction in the need for spinning reserve. Specifically, the current power
usage profile
can be used (in combination with "historical" records) to determine when
embedded
generators should be turned on. Such generators could be switched on either by
their
owners or remotely by the utility by instructing the central control unit 2A
to send an
appropriate packet.
Furthermore, improved network management may be achieved using load
to shedding. The meters 9, together with an appropriate distribution board 15
(see Figure 1)
connected to the serial interface 904, permit remote load shedding.
Specifically, a
customer may offer up appliances for remote load shedding. The utility
monitors
customer power usage over a short period, say 2 months. On the basis of the
power
usage profile so determined, the utility offers the customer a special billing
rate in return
for permitting the utility to remotely shed load at the customer's premises.
In addition, the
customer can view their usage profile, via the web, and use this information
to alter their
usage pattern if appropriate. Load shedding is achieved by the central control
unit 2A
sending a LOAD SHED PACKET to a meter 9, the LOAD SHED PACKET designating the
device that should be disconnected by a distribution board 15. The meter 9
then instructs
2o the distribution board 15 to make the appropriate switching.
In one embodiment of the invention, power usage profiling may be used to
indicate
illness, for example by a significant increase or decrease in power usage or
lack of
change in power usage over an extended period. Specific customer sites 8a-8i
may
request a follow up call or visit should their power usage change (or not
change)
significantly to check that they are not immobilised or seriously unwell.
Specifically,
consumers with serious medical problems, who wish to remain living alone, can
identify
themselves to the utility and request monitoring of their power usage profile
on a near
3o real-time basis. Should their power usage profile depart significantly from
the norm,
notification of a potential problem is raised by the central control unit 2A
to an
administrator.
Using the infrastructure of the present invention, customers may be provided
the
option to have a dual-tariff agreement. At present, two meters are required to
log power
usage for customers on a dual tariff agreement. One meter is used for one
particular tariff
period and switched off at the time when the second tariff applies. Usage
during the
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24
second tariff period is recorded on the second meter. Within the tariff
periods no
information is normally available on time-of-use, with the meter simply
recording total
usage. By using a meter 9 with the infrastructure of the present invention,
including the
database 2C, there is no need for a second meter. Reconciliation with the dual
tariff
structure can be achieved using records stored in the database 2C.
In some cases, customers may prepay their power account. Previously, if the
account became in deficit or became in deficit for a certain period and/or by
a certain
amount, the supply of power would be discontinued. When the database 2C
detects an
to account in deficit beyond some defined "grace period", the load shedding
functionality is
used to disconnect the bulk of the supply to the premises. The system could
provide such
customers only with an emergency supply, for example supply sufficient for
lighting and a
small amount of heating.
Text messages may be distributed via power line carrier. Specifically, via
their
meter 9 or customer display unit 10, a customer can arrange to receive text
messages
from and send text messages to, for example the meters 9 of other individuals,
a structure
(e.g. a body corporate), or to a wide area network 16 via the central control
unit 2A.
Advertising for a local community may be provided using the text message
functionality.
2o Specifically, individual consumers with a meter 9 can authorise their
utility to add their
electronic serial number to an address list for local advertisers or community
groups.
Local businesses and community groups can then arrange to have advertising
messages
or community notices forwarded to these consumers via the central control unit
2A.
For applications where an alarm is generated, in addition to the usual alarm
notification procedures, a text message may be sent to the neighbouring
properties should
an alarm be triggered. Should an intruder be on the premises, it is likely a
neighbour
could notify the Police in advance of the arrival of a security guard. Also,
nominated
contacts (such as nearest neighbours) may be sent a text message when a
medical alarm
is tripped or when the "at risk" power usage profile threshold is crossed.
Such notification
would be additional to any telephone contact specified in the event of an
alarm. The
telephone contact may be initiated directly by the meter 9 through a telephone
modem
connected to its serial interface 904 or alternatively by the central control
unit 2A in
respect to the alarm notification.
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Where in the foregoing description reference has been made to specific
components or integers having known equivalents, then those equivalents are
hereby
incorporated herein as if individually set forth.
5 Although the foregoing description of the invention has been given by way of
example with reference to the accompanying drawings, those skilled in the
relevant arts
will appreciated that modifications or improvements may be made thereto
without
departing from the scope of the invention as defined in the appended claims.
