Note: Descriptions are shown in the official language in which they were submitted.
CA 02339195 2001-02-O1
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ELECTRONIC ELECTRICITY METER INCLUDING
FLASH MEMORY
CROSS REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of U.S. Provisional Application No.
60/141,779, filed June 30, 1999, entitled "Electronic electricity meter
including flash
memory," and which is hereby incorporated by reference in its entirety.
BACKGROUND OF THE INVENTION
This invention relates generally to electricity metering, and more
particularly, to a microcomputer based electricity meter.
Electronic electricity meters for metering mufti-phase services typically
include a digital signal processor (DSP) and a microcomputer. Certain
functions and
operations are separately performed in the DSP and microcomputer. By dividing
the
functionality between the DSP and microcomputer, communications of data and
commands must be provided between the DSP and microcomputer. Such an
architecture is complex.
In addition, such meters typically are programmed to perform certain
functions. Although the meters are upgradeable, the types of upgrades that can
be
performed are limited to the tables and functions prestored in the meter. In
addition,
and in the past, increased functionality typically was a trade-off to cost.
That is,
adding functionality to the meter typically resulted in adding significant
costs to the
meter.
It would therefore be desirable to provide methods and apparatus for
metering electricity usage that allows upgradability, and that retains memory
in the
event of power failure. It would also be desirable to provide methods and
apparatus
for metering that are not limited to providing functions that are prestored in
the meter.
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BRIEF SUMMARY OF THE INVENTION
There is therefore provided, in one embodiment of the present
invention, a method for operating an electronic electricity meter having
current and
voltage sensors conf gured to generate measurements of current and voltage,
respectively; a microcomputer coupled to the current and voltage sensors and
configured to control operation of said meter; a flash memory coupled to said
microcomputer and configured to store configuration and metering data. The
method
includes steps of: mapping requests for data to a physical location of the
flash
memory; organizing the flash memory into logical blocks treated as atomic data
units
(ADU); and separately managing the ADUs.
The above-described embodiment provides a method for metering
electricity usage that allows upgradability of the meter, and that retains
memory in the
event of a power failure. In addition, the method is not limited to providing
functions
that are prestored in the meter.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a block diagram of an electricity meter.
Figure 2 is a data flow diagram for the electricity meter shown in
Figure 1.
Figure 3 is a functional block diagram of the meter shown in Figure 1.
Figure 4 is a table illustrating the 1/O board addressing mode.
Figure 5 is a mode diagram for a simple 1/O board.
Figure 6 is a mode diagram for a complex I/O board.
DETAILED DESCRIPTION OF THE INVENTION
Figure 1 is a block diagram of an electricity meter 100. Meter 100 is
coupled to a three phase, alternating current (AC) power source 102.
Particularly,
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current sensors 104 and voltage sensors 106 are coupled to power source 102
and
generate measures of current and voltage, respectively. Current and voltage
sensors
104 and 106 are well known in the art. In addition, a power supply 108 and a
revenue
guard option board 110 also are coupled to power source 102.
S Current and voltage measurements output by sensors 104 and 106 are
supplied to an analog-to-digital (A/D) converter 112. Converter 112, in the
exemplary
embodiment, is an 8 channel delta-sigma type converter. Converter 112 is
coupled to
a microcomputer 114. In the illustrated embodiment, microcomputer 114 is a 32
bit
microcomputer with 2Mbit ROM, 64 Kbit RAM. A 32 kHz crystal 116 provides a
timekeeping signal for microcomputer 114. Microcomputer 114 is coupled to a
flash
memory 118 and a electronically erasable programmable (i.e., reprogrammable)
read
only memory 120.
Meter 100 also includes an optical port 122 coupled to, and controlled
by, microcomputer 114. Optical port 122, as is well known in the art, is used
for
communicating data and commands to and from an external reader to
microcomputer
114. Communications via port 122 are performed in accordance with ANSI C 12.18
(optical port) and ANSI C12.19 (standard tables). A liquid crystal display 124
also is
coupled to microcomputer 114 via an LCD controller 126. In addition, an option
connector 128, coupled to microcomputer 114, is provided to enable coupling
option
boards 130 (e.g., a telephone modem board 132 or an RS-232 line 134, or a
simple
input/output (I/O) board 136 or a complex I/O board 138) to microcomputer 114.
Option connector 128 also includes a sample output 140. When configured to
operate
in a time-of use mode, a battery 142 is coupled to power source 102 to serve
as a
back-up to maintain date and time in the event of a power outage.
Figure 2 is a data flow diagram 200 for the electricity meter 100. As
illustrated by Figure 2, quantities such as watt hours per phase (WhA, WhB,
WhC) as
well as other quantities are determined by microcomputer 114. These quantities
are
sometimes referred to herein as internal quantities 202. Microcomputer 114
then uses
the pre-defined or user-selected functions F(n) to calculate a set of
quantities (referred
to as calculated quantities 228). Microcomputer 114 then uses the measurement
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profile 204 to select up to 20 quantities to store as user-selected
quantities. In
addition, external inputs 206 can be specified to be accumulated by
measurement
profile 204. In the embodiment shown in Figure 2, up to four external inputs
(E1, E2,
E3, E4) are collected. These may also be scaled by programmed multipliers and
divisors.
User-selected quantities 230 specified by measurement profile 204 can
be used to perform totalization. For example, a value from a register location
in user-
selected quantities 230 (e.g., register 7) can be added to a value stored in a
register
location (e.g., register 17) to provide a totalized value, and the totalized
value is stored
in a register location (e.g., register 17). In the embodiment illustrated in
Figure 2, up
to 8 totalizations can be performed.
Also in the embodiment shown in Figure 2, five demand values
(locations 0-4) 210 can be calculated from the quantities in user-selected
quantities
230. The values to use for the demand calculations are specified by the demand
select. Each demand value may have up to two coincident demands 212, 214 per
demand 210. The coincident demands are specified by the coincident select. A
coincident demand value may be another one of the selected demands, or the
quotient
of two selected demands. An average power factor 222 is stored in numerator
and
denominator form. Time-of use summaries (A-D) 216 for the selected demands are
also available in a time-of use meter. Up to 20 quantities can be recorded in
load
profile data 218. The quantities to be recorded are specified by the load
profile select.
Up to five summations 226 can be calculated. The quantities to be calculated
are
specified by the summations select. Time of use summaries (A-D) 216 for the
selected summations are also available in a time-of use meter. Data
accumulations
224, summations 226, demands 210 coincident demands 212, 214, and time-of use
summaries 216 may be selected for display 210 on the meter's LCD.
Meter 100 can be programmed by an operator, e.g., a utility, so that
meter 100 determines desired quantities, regardless of whether that quantity
is a
common, IEEE-defined value such as apparent volt-ampere-hours, or a quantity
used
only by a particular utility. Generally, a momentary interval is defined as 60
cycles
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(for 60 Hz installations) or 50 cycles (for 50 Hz installations) of the
fundamental
voltage frequency. Known meters calculate a pre-defined set of quantities from
the
basic quantities every momentary interval. These quantities include total watt-
hours
(fundamental plus harmonics), apparent volt-ampere-hours, and arithmetic
apparent
volt-ampere hours. These quantities are summed by the minute. One-minute
accumulations of data are stored in a structure called the minute first-in,
first-out
(FIFO) register. An example of the structure of a minute FIFO is illustrated
below.
1-minute accumulation of watt-hours
1-minute accumulation of var-hours
1-minute accumulation of apparent volt-ampere-hours
1 minute accumulation of watt hours
1 minute accumulation of var-hours
1 minute accumulation of apparent volt-ampere-hours
1-minute accumulation of watt-hours
1-minute accumulation of var-hours
1-minute accumulation of apparent volt-ampere-hours
Data is retrieved from the minute FIFO and added to other
accumulators, from which summations (e.g. total kilowatt-hours), demand
calculations (e.g. maximum kilowatt demand), and load profile recording
operations
are performed.
Typically there is very little flexibility provided by electricity meters in
how the momentary interval basic quantities are processed to generate the
revenue
quantities that are of interest to utilities. A user may, for example, select
from several
pre-defined quantities that are computed every momentary interval, and the
user may
select the length of the demand interval or subinterval and the length of the
load
profile interval.
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In contrast, meter 100 enables a user to define methods of data
calculations at all points in the data processing sequence, e.g, at the end of
a
momentary interval, at the end of a minute, at the end of a demand
(sub)interval, and
at the end of a load profile interval.
In another embodiment, code is downloaded into an external flash
memory, and then a measurement profile is programmed to use the calculation
specified by the code. Vectors are used to update and perform a list of tasks
in ROM,
or are replaced by versions in flash memory for other function blocks.
Figure 3 is a functional block diagram 300 of meter 100. The f( )
blocks in Figure3 illustrate the points during data processing at which user-
defined
functions can be applied to data. For example, if a user wants to compute
apparent
volt-ampere-hours (defined as the vector sum of watt-hours, var-hours, and
distortion
volt-ampere hours), the user defines a function that would be executed at the
end of
each momentary interval. This quantity could then be accumulated for
summations,
demands, or load profile data. Accumulations of apparent volt-ampere-hours
could
also be used to compute some other quantity at a different point (e.g. a
demand
interval accumulation of apparent volt-ampere-hours could be used to compute
an
average power factor for that demand interval). Examples of some of the
mathematical operators that would be available are set forth in the table
below. These
functions are programmed into the meter non-volatile memory.
Meter 100 can also accumulate data provided by external devices such
as other electricity meters, gas meters, and water meters. Typically this is
done
through hardware that provides pulses to the electricity meter, which counts
the pulses
(each pulse represents some pre-defined value, e.g. 1 watt-hour). Meter 100
allows
mathematical operations to be defined that operate on accumulations of these
pulses.
For example, a utility might have an installation where three electricity
meters are
required. By having two of the meters provide pulse data to the third meter
representing watt-hour usage, and defining in the third meter a calculation to
add the
pulse data from the other two meters to its own watt-hour data, the utility
can read the
total watt-hour usage of the installation from one meter
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Because a user can specify mathematical operations to be performed on
data at a number of steps in the processing of metering data, meter 100
provides that a
wide variety of quantities can be determined. Meter 100 also prevents the
meter
manufacturer from having to anticipate at the product development stage what
quantities a utility might require. Since there are constraints that a user
must be aware
of when programming a meter to compute a given quantity, it is likely that the
meter
manufacturer would implement for the utility the program that defines the
calculations. The utility would then install the program into its programming
software
package, which would ultimately download the program into meter 100.
Table 1 Momentary interval basic quantities
watt-hours, element A, fundamental + harmonics
watt-hours; element B, fundamental + harmonics
watt-hours; element C, fundamental + harmonics
I S var-hours, element A, fundamental + harmonics
var-hours, element B, fundamental + harmonics
var-hours, element C, fundamental + harmonics
watt-hours; element A, fundamental only
watt-hours; element B, fundamental only
watt-hours; element C, fundamental only
var-hours, element A, fundamental only
var-hours, element B, fundamental only
var-hours, element C, fundamental only
volt-squared-hours, element A, fundamental + harmonics
volt-squared-hours, element B, fundamental + harmonics
volt-squared-hours, element C, fundamental + harmonics
ampere-squared-hours, element A, fundamental + harmonics
ampere-squared-hours, element B, fundamental + harmonics
ampere-squared-hours, element C, fundamental + harmonics
ampere-squared-hours, element A, fundamental only
ampere-squared-hours, element B, fundamental only
ampere-squared-hours, element C, fundamental only
volt-squared hours, element A, fundamental only
volt-squared hours, element B, fundamental only
volt-squared hours, element C, fundamental only
sample count
imputed neutral ampere-squared-hours
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Table 2 Other data definitions
Functions of momentar interval basic quantities user defin
momentary interval calculation 1
momentary interval calculation 2
momentary interval calculation K
Functions of momentar interva_1 basic quantities (meter aennea
momentary interval total wh all harmonic
momentary interval total varh all harmonic
momentary interval total Wh fundamental
momentary interval total varh fundamental
Distortion Vah A
Distortion Vah B
Distortion Vah c
Total Distortion VAh
Meter-defined minute quantities
one minute accumulation of pulses from channel 1
one minute accumulation of pulses from channel 2
One minute accumulation of pulses from channel L
delivered Wh
lagging varh during delivered Wh
leading varh during delivered Wh
received Wh
lagging varh during received Wh
leading varh during received Wh
User-defined minute quantities
one minute sum 1 of momentary interval basic quantities
one minute sum 2 of momentary interval basic quantities
one minute sum M of momentary interval basic quantities
one minute sum 1 of moment. Int. qtys (user-defined)
one minute sum 2 of moment. Int. qtys (user-defined)
one minute sum N of moment. Int. qtys (user-defined)
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one minute sum 1 of moment. Int. qtys (meter-defined)
one minute sum 2 of moment. Int. qtys (meter-defined)
one minute sum P of moment. Int. qtys (meter-defined)
Functions of one minute user-defined sums use
function 1 of other one minute user-defined sums
function 2 of other one minute user-defined sums
function Q of other one minute user-defined sums
Functions of one minute meter-defined sums (use
function 1 of other one minute meter-defined sums
function 2 of other one minute meter-defined sums
function R of other one minute meter-defined sums
Functions of minute fifo sums (user-defined
function 1 of minute fifo sums
~~ function 2 of minute fifo sums
function S of minute fifo sums
Demand interval sums (stored in subinterva~ queue)
demand interval sum 1 of one minute user-defined qtys
demand interval sum 2 of one minute user-defined qtys
demand interval sum T of one minute user-defined qtys
demand interval sum 1 of one minute meter-defined qtys
demand interval sum 2 of one minute meter-defined qtys
demand interval sum U of one minute meter-defined qtys
Functions of demand interval sums {user-defin
function 1 of other demand interval sums
function 2 of other demand interval sums
function V of other demand interval sums
minimum value 1 during demand interval
minimum value 2 during demand interval
minimum value W during demand interval
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maximum value 1 during demand interval
maximum value 2 during demand interval
maximum value X during demand interval
Load profile interval sums (stored in load prolue accum~
load profile interval sum 1 of one minute user-defined qtys
load profile interval sum 2 of one minute user-defined qtys
load profile interval sum Y of one minute user-defined qtys
load profile interval sum 1 of one minute meter-defined qtys
load profile interval sum 2 of one minute meter-defined qtys
load profile interval sum Z of one minute meter-defined qtys
F_ unctions of load profile interval sums (use
function 1 of other load profile interval sums
function 2 of other load profile interval sums
function A of other load profile interval sums
minimum value 1 during load profile interval
minimum value 2 during load profile interval
minimum value B during load profile interval
maximum value 1 during load profile interval
maximum value 2 during load profile interval
maximum value C during load profile interval
min and max values may be voltage, frequency, current, etc.
Table 3 Example mathematical operations
WORD square WORD_SQUARE_ ROOT pointer to results:
root pointer to operand (DWORD*)-final answer
pointer to result (WORD*)-working space
location 1
-working space
location 2
WORD 2-D WORD_2D_VECTOR_SUM ...
vector sum pointer to operand 1 -working space
(INT*)
pointer to operand 2 location N
(1NT*)
pointer to result (WORD*)
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DWORD 2-D DWORD_2D VECTOR_SUM data types
vector sum pointer to operand 1 BYTE: unsigned
(LONG*)
pointer to operand 2 1-byte qty
(LONG*)
pointer to result (DWORD*)1NT: signed 2-byte
qtY
WORD: unsigned
2-byte qty
LONG: signed
4-
byte qty
DWORD: unsigned
4-byte qty
WORD 3-D WORD_3D VECTOR_SUM
vector sum pointer to operand 1
(INT*)
pointer to operand 2
(INT*)
pointer to operand 3
(INT*)
pointer to result (WORD*)
DWORD 3-D DWORD_3D VECTOR_SUM
vector sum pointer to operand 1
(LONG*)
pointer to operand 2
(LONG*)
pointer to operand 3
(LONG*)
pointer to result (DWORD*)
WORD 3-D WORD_3D VECTOR_DIEF
vector differencepointer to operand 1
(INT*)
pointer to operand 2
(INT*)
pointer to operand 3
(INT*)
pointer to result (WORD*)
DWORD 3-D DWORD 3D VECTOR_DIFF
vector differencepointer to operand 1
(LONG*)
pointer to operand 2
(LONG*)
pointer to operand 3
(LONG*)
pointer to result (DWORD*)
INT multiply INT_MULT
pointer to operand 1
(INT*)
pointer to operand 2
(INT*)
pointer to result (LONG*)
general multiplyMULT_MB (written in
C)
size of operand 1 (BYTE)
pointer to operand 1
(BYTE*)
size of operand 2 (BYTE)
pointer to operand 2
(BYTE*)
pointer to result (BYTE*)
INT divide INT_DIVmE
pointer to operand 1
(LONG*)
pointer to operand 2
(INT*)
pointer to result (INT*)
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general divide D1V MB
(not available size of operand 1 (BYTE)
at
momentary pointer to operand 1
(BYTE*)
interval boundary)size of operand 2 (BYTE)
pointer to operand 2
(BYTE*)
pointer to result (BYTE*)
INT add 1NT_ADD
pointer to operand 1
(INT*)
pointer to operand 2
(INT*)
pointer to result (INT*)
INT to LONG INT_TO LONG_ADD
add pointer to operand 1
(LONG*)
pointer to operand 2
(1NT*)
pointer to result (LONG*)
LONG add LONG ADD
pointer to operand 1
(LONG*)
pointer to operand 2
(LONG*)
pointer to result (LONG*)
general add ADD MB
(not available size of operand 1 (BYTE)
at
momentary pointer to operand 1
(BYTE*)
interval boundary)size of operand 2 {BYTE)
pointer to operand 2
(BYTE*)
pointer to result (BYTE*)
LONG subtract LONG SUB
pointer to operand 1
(IN'T*)
pointer to operand 2
(INT*)
pointer to result (INT*)
general subtractSUB_MB
size of operand 1 (BYTE)
pointer to operand 1
(BYTE*)
size of operand 2 (BYTE)
pointer to operand 2
(BYTE*)
pointer to result (BYTE*)
assignment ASSIGN
data type ( 1, 2, or
4 byte qty)
constant
pointer to destination
fill FILL
number of bytes to fill
(BYTE)
fill value (BYTE)
pointer to destination
(BYTE*)
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if then-else IF
pointer to operand 1
comparison
pointer to operand 2
comparison TRUE operation
1
comparison TRUE operation
2
comparison TRUE operation
N
ENDIF or ELSE
else operation 1
else operation 2
else operation P
ENDIF
no operation NOP
Flash Memory
In one embodiment, a nonvolatile, alterable flash memory 118 is
utilized to store configuration, diagnostic, metering and other data. Flash
memory 118
provides the advantage that a tremendous amount of data can be stored, which
eliminates a need for a daughter board to add additional memory. Also, a data
manager maps requests for data to the physical location of the data. By
utilizing the
data manager, data can move from one storage medium to another without
affecting
the metering application.
Flash memory 118 is typically organized into multiple large sectors (64
KB) which can be erased in their entirety. When flash memory is erased, all
bits in a
sector are set to 1. When data is written, 1 bits are changed to 0 bits. Once
a bit has
been changed to a 0, it cannot be changed back to a 1 without erasing the
entire sector.
For practical purposes, a given location in flash memory can be written
to once after it has been erased. To update even a single byte in a record, a
new copy
of the entire record is written to an unused location. There are many known
methods
for tracking used, unused and obsolete memory in each sector including file
allocation
tables (FAT) and linked lists. When a sector becomes full, it is necessary to
transfer
all "active" records to an unused sector and then erase the "dirty" sector.
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Data within meter 100 is organized into logical blocks (e.g. Current
Season rate A data, Previous Reset data, Previous Season Data) that are
treated as
atomic data units (ADU) by the data manager. Each ADU is managed separately.
The data manager is responsible for maintaining a pointer to the physical
location of
the current copy of each ADU. For the metering application to update an ADU
stored
in flash memory 118, a new copy of the ADU is written to an unused portion of
flash
memory 118. Since the physical location of the ADU has changed, the pointer to
the
current ADU is updated. Keeping a pointer to the current ADU eliminates the
need to
traverse a linked list through flash memory 118 to find the current ADU at the
end of
the chain.
The list of pointers to current ADUs maintained by the data manager
may be kept in RAM or non-volatile memory. The list, however, is saved in non-
volatile at power failure. If stored in flash memory 118, each change to a
single ADU
requires rewriting the entire list of pointers. Another approach is to
maintain the list
1 S of pointers in EEPROM 120. With EEPROM 120, only the pointers to affected
ADUs must be updated.
ADUs can be combined into logical groupings that are stored in a
common set of flash sectors. These logical groupings can be based on, for
example,
the frequency with which the ADUs are updated and, the size of the ADUs. Each
logical grouping of ADUs has at least two sectors dedicated to data storage.
One or
more sectors are "active", and the remaining sector is erased and available
when the
last "active" sector fills up. Possible groupings of ADU's include power fail
data and
communications snap shots, configuration and revenue data, self reads and
event logs,
and load profile data.
The data manager also performs a garbage collection task that monitors
each group of sectors. When the active sector{s) in a group is full, the
garbage
collection task initiates the copying of all active ADUs in the oldest sector
to a new
sector. The copying is done atomicly, one ADU at a time. When an ADU is copied
to
the new sector, the pointer to the current ADU is updated to match its
physical
location in the new sector.
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Meter 100 can service a power failure in the middle of garbage
collection and pick up where it left off without losing any data, and
minimizes the
amount of time the power fail interrupt is disabled to permit the meter
sufficient time
to close down in an orderly fashion.
Determining when a sector is full can be done in one of many ways. A
"high water" mark can be set for a sector. When the sector crosses that high
water
mark, garbage collection is initiated. The high water mark could be determined
by the
size of the largest ADU for a group. Alternatively, the data manager could
wait to
consider a sector full until it is unable to satisfy a request to allocate
storage. If too
much space is wasted at the end of the sector, the erase time will increase.
If a second set of pointers are used for data that affects the
configuration of meter 100, this second set of pointers can be used to allow
the
"commitment" and "roll-back" of configuration information. At the beginning of
a
session to change the configuration, the pointers to the current configuration
information are copied. When the configuration information is updated, the
updated
copy is written to flash and the "copy" pointer is updated. After all
configuration
information has been written, a command to indicate that the configuration is
complete is issued. At that point, the current pointers are updated with
copies of the
updated pointers. If the configuration process is interrupted before it
completes, meter
100 maintains the current configuration. The old configuration information is
still
available in flash since the original pointers and data were not changed.
Nonvolatile, alterable flash memory and vectors also can be utilized to
update the firmware of microcomputer 114 while meter 100 is in service. As
explained above, meter 100 uses vectors to functions and/or tasks to provide a
level of
indirection that can be used to upgrade or patch the code. Meter 100 includes
two
forms of program memory, specifically, on-chip masked ROM or flash and off
chip
flash 118. The on-chip masked ROM typically has a speed advantage over off
chip
memory. Time critical functions are stored in the on-chip masked ROM. Other,
non-
time critical features are stored in either on-chip masked ROM or off chip
flash 118.
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For the initial release of the firmware, the on-chip masked ROM could be
filled with
as much firmware as is practical.
The off chip flash 118 can be used to store vectors to functions, tasks
and/or tables of tasks to be executed and non-time critical functions and
tasks. The
vectors in the table point to functions or tasks stored in on-chip masked ROM
or off
chip flash 118. At power up, these vectors and tables are read into memory.
Rather
than call a function and/or task directly, the firmware uses the vectors to
call functions
and/or tasks.
The firmware can be upgraded in multiple ways. For example, a
function or task stored in off chip flash can be directly over written,
replacing the old
code with new code, or a new function or task can be written to off chip flash
and the
corresponding vector updated to point to the new function or task.
A built-in "bootloader" allows new code to be downloaded into the off
chip flash. Meter 100 ceases metering when the bootloader is initiated. The
1 S bootloader accepts blocks of new code and writes them to the off chip
flash 118.
When the download is complete, meter 100 "reboots" and begins executing with
the
new code.
Commercially available off chip flash memories permit programming
without any special voltages. In addition, such off chip flash memories
combine two
"banks" of memory that act like separate chips. One bank of the chip can be
used for
code storage. The other bank can be used for data storage. Each bank operates
independent of the other. One can be programmed while the other is being read.
One
such chip can be used to store off chip code and data.
In other embodiments, a large electrically erasable programmable (i.e.,
reprogrammable) read only memory (EEPROM) is used for part of the nonvolatile,
alterable memory. In this embodiment, some of the data that is described above
as
being stored in flash memory is stored, instead, in the EEPROM. However, the
load
profile is still stored in flash memory 118.
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It should be recognized that in still other embodiments, other types of
nonvolatile, alterable memory can be substituted for EEPROM and flash memory
118.
The memory or memories used should retain their contents during periods when
power is not applied, and it should be possible to update their contents as
needed,
although not necessarily in the manner required by a flash memory. One skilled
in the
art would be able to select appropriate memories and make the necessary
circuit
modifications to use the selected memory or memories.
I/O Board Addressing
As described above with reference to Figure l, meter 100 includes an
option connector 128 which connects to both simple and complex input/output
board
(I/O) boards 136 and 138. Flash memory 118 enables functional expansion of
meter
100, and such expansion is fixrther facilitated by enabling use of multiple
types of I/O
boards 130. To facilitate such board interchangeability, microcomputer 114 is
programmed to determine the type of I/O board 130 which is being utilized.
Figure 4
illustrates the status of microcomputer pins utilized in connection with
communication with UO board 130. The pin positions relate to the identified
signals.
Microcomputer 114 is operable in a normal mode, and ID mode, and address mode,
a
read mode, and a write mode with respect to such I/O board 130.
As explained above, multiple types of boards can be provided, and
each board type has an identifier. In one specific embodiment, a 3-bit address
specifies the board type. For example, an input/output board is specified as a
type
001. A logic 0 on all response lines means no option board of the specified
type is
present. A simple I/O board 136 has an identifier of O1. A complex I/O board
138
has an identifier of 10.
Figure 5 is an exemplary mode diagram for signals of a simple I/O
board 136. The signal supplied to I/O board 136 controls the mode of operation
of the
board, e.g., >D mode, address mode, read mode, and write mode. "X" means
"don't
care", and "N/A" means "not available". In the write mode, for KYZ outputs, a
logic
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1 closes the K-Z contact and opens the K-Y contact. For a 2-wire output, a
logic 1
closes the output contact.
Figure 6 illustrates an exemplary mode diagram for signals at a
complex I/O board 138. Again, the signal supplied to I/O board 138 controls
the
mode of operation of the board, e.g., ID mode, address mode, read mode (nib
0), read
mode (nib 1 ), write mode (nib 0), and write mode (nib 1 ). In the read mode,
logic 1
indicates the corresponding input is activated. For 2-wire inputs, only the Z
inputs are
used. In the write mode, for KYZ outputs, a logic 1 closes the K-Z contact and
opens
the K-Y contact. For 2-wire outputs, a logic 1 closes the output contact.
Fast Optocom
As shown in Figure 1, meter 100 includes an optical port 122 for
communications with external hand held units and other devices. To enable such
communications, both the external unit and optical port 122 include
phototransistors.
Meter 100 can store significant volume of data (e.g., 2 months of load profile
data for
20 channels), and it is desirable to quickly transmit such data to a hand held
unit
during a communication session. A phototransistor, however, requires that the
voltage across the transistor must change in order to switch from a first
state to a
second state.
To facilitate faster communications, op-amps are connected to the
phototransistors. Each op-amp is configured as a current to voltage converter.
The
op-amp therefore maintains a constant voltage across the phototransistor. As a
result,
the output can change between a first state and a second state with minimal
impact on
phototransistor voltage.
Waveform Capture
Microcomputer 114 is programmed to capture waveform data (gain and
phase corrected samples) upon the occurrence of a predetermined event. An
event
may, for example, be that the voltage in one of the phases falls below a
predetermined
percentage of a reference voltage, the voltage in one of the phases rises
above a
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predetermined percentage of a reference voltage, or a power fail transient is
detected.
Waveform capture is activated by setting a waveform capture flag, and if the
flag is
set, a waveform counter is set to a predetermined count, e.g., 70. Upon the
occurrence
of the event, and if the waveform capture flag is set and if the counter has a
value
greater than 0, then voltage samples and current samples for each phase are
stored in
RAM. These samples are stored after DAP 112 interrupts the main process
running in
microcomputer 114 and the DSP interrupt service routine is invoked. The
counter is
decremented, and if the counter still has a value greater than 0, then the
voltage
samples and can ent samples for each phase at that time are stored. These
samples are
also stored after the DAP 112 interrupts the main process and the DSP
interrupt
routine is serviced. Operations continue in this manner so that upon the
occurrence of
an event, the desired waveform data is collected.
In one embodiment, microcomputer 114 can be programmed to collect
more or less than 70 samples per waveform from a set of six wavefonns (three
current
waveforms and three voltage waveforms). For example, the amount of data
collected
can be programmed based on the type of triggering event.
Revenue Guard Plus
Microcomputer 114 is programmable to determine energy consumption
and other metering quantities for many different form types. In addition, and
if one
phase voltage is lost during metering operations and the other two phase
voltages are
still available, microcomputer 114 automatically converts from a three voltage
source
metering operation to a two voltage source metering operation. For example,
and if
metering is being performed with three input voltage sources Va, Vb, and V~,
and if
one of the phase voltages, e.g., Va, is lost, microcomputer 114 automatically
changes
to metering to the appropriate form type, i.e., generating metering quantities
using Vb
and V~.
More specifically, an in an exemplary embodiment, microcomputer
114 is operable to perform metering in accordance with multiple form types. A
case
number is assigned to each form type depending, for example, upon the number
of
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elements and the number of wires. For example, form type 6 corresponds to a
WYE
configuration when all voltages Va, Vb, and V~ are present. Form types 7, 2,
and 8
correspond to metering operations performed when Va, Vb, and V~, respectively,
are
absent. If microcomputer 114 is operating in accordance with type 6 and
voltage Va is
lost (Va = -[Vb + V~J), then microcomputer automatically converts to metering
in
accordance with form type 7. Similarly, if voltages Vb or V~ are lost, then
microcomputer 114 automatically converts to metering in accordance with form
type 2
or form type 8, respectively. Therefore, rather than discontinuing metering
and
possibly losing metering data, meter 100 automatically converts to another
form type
in the event that one of the phase voltages is lost. In one embodiment, meter
100
converts to a 2 1/2 element meter. After a programmable interval, voltage is
checked
again and an appropriate type (6, 2, 7 or 8) is then invoked.
In one embodiment, determining whether voltage Ve is lost comprises
checking three consecutive times at a 15 second interval after switching back
to DSP
1 S form type 6. Also, in one embodiment, Va is considered "lost" when it
drops to one-
half of the normal voltage. In yet another embodiment, at least one of the
number of
consecutive checks made before Va is deemed lost, the interval between the
checks,
and the voltage at which Va is deemed lost is programmable.
Long Communication Session
When an external reader attempts to obtain data from meter 100, and
since a large volume of data can be stored in the meter memory, it is desired
to
provide the reader with a snap shot of data at a particular point in time,
rather than
accessing the different metering data at duterent points m nine aunng one
communication session. If different data is accessed at different points in
time, then it
is possible that the metering data will not be consistent, especially if the
communication session is long, e.g., 1 hour. For example, a load 142 continues
to
consume energy during a read operation, and if the communication session
requires
more than a few minutes to complete, the metering data collected at the
beginning of
the session will not necessarily correspond to the metering data collected at
the end of
the session.
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Accordingly, in one embodiment, upon receipt of a request for a
communication session, e.g., reading a revenue table or a communication
requiring a
billing read command, microcomputer 114 generates a static copy of selected
revenue-
related data. For example, the current load profile data is written to EEPROM
120, or
a static copy is made in RAM. This snapshot of data is then read out by the
reader/host via port 122.
In one embodiment, microcomputer 114 generates the static copy of
selected revenue-related data in response to a PSEM command.
By storing the snapshot of data and providing such snapshot of data to
the external device, the read data all corresponds to a particular point in
time and is
consistent, i.e., the data read at minute 1 of the session is obtained under
the same
circumstance as the data read at minute 60 of the session.
Rollback
In the event that meter 100 is to be updated or reprogrammed during
1 S operation, the following procedure is performed to ensure that the update,
or new
program, is executed as quickly as possible upon initiation of the change.
Specifically, EEPROM 120 includes storage locations for active and inactive
metering
programs, i.e., an active program segment and an inactive program segment. The
program currently being utilized by meter 100 is stored in the active program
segment
of EEPROM 120. The active program controls include, for example, display
scroll
parameters, time-of use data, a calendar, season change, and holidays. Billing
data is
generated in accordance with the active program.
In the event that an update to the active program is required, or in the
event that an entirely new program is to be utilized, then a host writes the
updated/new program to the inactive segment in EEPROM 120. Upon initiation of
writing the updated/new program to EEPROM 120, meter microcomputer 114 also
interrupts the then active program and the metering data is stored in the
meter
memory. Upon successful completion of the program update, or loading the new
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program, microcomputer 114 designates the inactive segment containing the new
program as the active segment, and causes metering operations to then proceed.
The
metering data stored in the meter memory during the update is processed by the
new
program.
By interrupting metering program operations during the update, and
storing the metering data collected during the update and processing such data
with
the new program once the new program is loaded, the new program is utilized in
metering operations as soon as possible. Such operation sometimes is referred
to as
"rollback" because meter 100 "rolls back" to a previous configuration if a
change to a
current configuration is interrupted before it is completed. In this manner,
meter 100
is not left in an inconsistent state, and can continue operating with a
previously
programmed set of parameters. (Previously, meters would lose their programs
entirely
if programming were interrupted.)
If the new program is not successfully written into the inactive
segment, then microcomputer 114 does not change the designation of the active
segment and metering continues with the program stored in the active segment.
Specifically, the metering data collected during the attempted update is
processed
using the program in the active segment and metering operations continue.
Diagnostics
The following diagnostic operations are performed by meter
microcomputer 114. Of course, additional diagnostic operations could be
performed
by microcomputer 114, and fewer than all the diagnostic operations described
below
could be implemented. Set forth below are exemplary diagnostic operations and
a
description of the manner in which to perform such operations. In one
exemplary
embodiment, diagnostics 1-5 and 8 are checked once every 5 seconds. Also in
this
embodiment, diagnostics 6 and 7 are checked once every second. A programmable
number of consecutive failures are permitted for diagnostics 1-S and 8, and
another,
different, programmable number of consecutive failures are permitted for
diagnostics
6 and 7 before a diagnostic error results.
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Diagnostic #1 (Polarity, Cross Phase, Rev. Energy Flow)
This diagnostic verifies that all meter elements are sensing the correct
voltage and current for the electrical service. In an exemplary embodiment,
this
diagnostic is accomplished by comparing each voltage and current phase angle
with
expected values. In one specific embodiment, voltage phase angles must be
within ten
degrees of the expected value and current phase angles must be within 120
degrees of
the expected value to prevent a diagnostic 1 error.
Diagnostic #2 (Phase Voltage Alert)
This diagnostic verifies that the voltage at each phase is maintained at
an acceptable level with respect to the other phases. In an exemplary
embodiment,
and for diagnostic 2 tests, the A phase voltage is combined with the user
programmed
percentage tolerance to determine the acceptable range for the B and C phases
voltages as appropriate for the ANSI form and service type. For a 4 wire delta
service,
Vc is scaled before being compared to Va. In one embodiment, this diagnostic
is not
performed if Va is bad.
Diagnostic #3 (Inactive Phase Current)
This diagnostic verifies that the current of each phase is maintained at
an acceptable level. A diagnostic 3 error condition is triggered if the
current of one or
more phases, as appropriate for the ANSI form and service type, falls below a
user
programmed low current value and at least one phase current remains above this
value.
Diagnostic #4 (Phase Angle Alert)
This diagnostic verifies that the current phase angles fall within a user
a specified range centered on expected values. In an exemplary embodiment,
diagnostic #4 is enabled only if diagnostic #1 is enabled and is checked only
if
diagnostic #1 passes. The user programmed current phase angle tolerance value
for
diagnostic #4 has a range of zero to ninety degrees in increments of 1/10
degree.
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Diagnostic #5 (Distortion Alert)
This diagnostic verifies that the user-selected form of distortion
measured on each individual element and, in the case of distortion power
factor,
across all elements, is not excessive. This diagnostic is selectable to
monitor one of
the following distortion measures.
Distortion Power Factor (DPF), per element and summed
Total Demand Distortion (TDD), per element only
Total Harmonic Current Distortion (ITHD), per element only
Total Harmonic Voltage Distortion (VTHD), per element only, if a
valid element.
A diagnostic 5 error condition is triggered if any of the distortion
calculations exceed
a user-specified threshold.
Four counters are associated with diagnostic 5 (one counter for each
element, and for DPF only, and one counter for the total of all elements). 1n
an
exemplary embodiment, diagnostic 5 is checked only when the one second kW
demand exceeds a user programmed threshold which is the same demand threshold
used for the power factor threshold output. The user programmed distortion
tolerance
value for diagnostic 5 has a range of 0 to 100% in increments of 1 %.
Diagnostic 6 (Llndervoltage, Phase A)
This diagnostic verifies that the phase A voltage is maintained above
an acceptable level. In an exemplary embodiment, the user programs an
undervoltage
percentage tolerance for diagnostic 6 that has a range of 0 to 100% in
increments of
1%. A diagnostic 6 error condition is triggered if the voltage at phase A
falls below
the reference voltage (Vref) minus the undervoltage percentage tolerance (T).
Fail Condition: Va < Vref(100% - T%), for a programmable number of
consecutive checks.
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The threshold used for diagnostic 6 is also used for the potential
annunciators.
Diagnostic #7 (Overvoltage, Phase A)
This diagnostic verifies that the phase A voltage is maintained below
an acceptable level. In an exemplary embodiment, the user programs an
overvoltage
percentage tolerance for diagnostic 7 that has a range of 0 to 100% in
increments of
1%. A diagnostic 7 error condition is triggered if the voltage at phase A
rises above
the reference voltage (Vrefj plus the overvoltage percentage tolerance (T).
Fail Condition: Va > Vref(100% + T%)
Diagnostic #8 (High Imputed Neutral Current)
This diagnostic verifies that the imputed neutral current is maintained
below an acceptable level. In an exemplary embodiment, a diagnostic 8 error
condition is triggered if the imputed neutral current exceeds a user-
programmed
threshold. Foam 45 and 56 as 4WD and 4WY applications are not valid services
for
determining the imputed neutral values. In these cases, the imputed neutral is
zeroed
after the service type has been determined.
Meter 100 includes an event log stored in meter memory for capturing
information about events. The event log is used, for example, to store the
occurrence
of events, such as a diagnostic condition sensed as a result of performing one
of the
tests described above.
In addition, and using complex I/O board 138, an output can be
generated by microcomputer 114 to such board 138 to enable remote
determination of
a diagnostic failure. Such capability is sometimes referred to as a Diagnostic
Error
Alert. When configured for a diagnostic error alert, the following designation
may be
used to correlate a diagnostic error condition to an output.
Function Bit
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Diagnostic 1 0
Diagnostic 2 1
Diagnostic 3 2
Diagnostic 4 3
Diagnostic 5 4
Diagnostic 6 5
Diagnostic 7 6
Diagnostic 8 7
For example, an output of 01010101 provides a diagnostic error alert for
diagnostic
tests 1,3,5, and 7.
When one of the selected diagnostics is set, the output is set. When all
selected diagnostics are cleared, the output is cleared. Diagnostic operations
are not
performed when meter 100 is determining the electrical service.
Programmable Durations
In one specific embodiment, the diagnostic tests described above,
except diagnostics 6 and 7 (undervoltage and overvoltage), are performed every
5
seconds using one second worth of data. Diagnostics 6 and 7 are performed
every
second. If a diagnostic fails each check performed during a programmed
duration
which begins with the first failed check, the diagnostic error is set and the
diagnostic
counter is incremented.
In an exemplary embodiment, two programmable diagnostic fail
durations are provided. One programmable fail duration is for diagnostics 6
and 7,
and one programmable fail duration for the other diagnostics. The fail
duration for
diagnostics 6 and 7 is programmable from 3 seconds to 30 minutes in 3 second
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increments. The fail duration for the remaining diagnostics is programmable
from 15
seconds to 30 minutes in I S second increments.
In the exemplary embodiment, two consecutive error free checks are
required to clear a diagnostic error condition. The range for all diagnostic
counters is
0 to 255. When a diagnostic counter reaches 255, it must be reset by a user.
Diagnostic errors and counters may be reset via communications procedures.
Totalizations
As explained above, meter 100 includes a measurement profile 204
that accepts external inputs. The external inputs can, for example, be pulse
inputs
from other meters associated with a load, e.g., a manufacturing plant. The
external
inputs can be collected, scaled (e.g., every minute), and then totaled (i.e.,
summed
together) to provide a quantity of total energy consumed from one plant. The
totalized
value can then be stored in one location. In addition, internal quantities can
be
totalized (e.g., user-selected quantities can be totalized).
1 S Data Accumulators
In one embodiment, microcomputer 114 includes a 64KB on-board
RAM, microcomputer 114 is programmed to accumulate values in its RAM, and
these
accumulated values are then subsequently displayed on display 124. By
programming
microcomputer 114 to store and accumulate data in this manner, meter 100 can
accumulate metering data for display to an operator. Moreover, a utility
company can
monitor many quantities without having data by time of use rate, demand reset,
seasonal change, etc.
Load Profile
Electricity meters typically store integrated quantities as load profile
data. In addition to adding quantities, meter 100 can be programmed to store
the
maximum and minimum or most recent quantities, i.e., meter 100 can track non-
integrated quantities. A user, therefore, can select up to 20 quantities for
recording.
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Accordingly, microcomputer 114 is programmed to compare the maximum and
minimum values at every interval with the stored quantities, and if a new
maximum or
minimum is detected, the new maximum or minimum is stored in the appropriate
recorder channel.
Demand
As with load profile data, microcomputer 114 is programmed to
compare the demand value at every interval with a stored maximum demand in,
for
example, the on-board RAM. If the current demand is greater than the stored
maximum demand, then the current demand is copied over the stored maximum
demand and stored. In addition, for non-integrated quantities, momentary by
momentary interval comparisons can also be performed.
Coincident Power Factors
Meter 100 is configurable to determine multiple types of demands,
such as kW, kVAr, kVA, and distortion KVA. For each demand, there are other,
e.g.,
two, coincident values. Accordingly, meter microcomputer 114 determines, on
each
interval, demand values and compares the calculated demand values to the
stored
maximum values. if one of the then calculated values is greater than the
corresponding demand stored value, i.e., the current value is the maximum,
then the
value of the other demands is of interest. Specifically, power factor is the
quotent of
two of the demands, and two coincident power factors can be determined and
stored.
For example, if there are five demand types, an operator can specify that upon
the
occurrence of a maximum demand, two coincident power factor values are stored,
e.g., Demand 1 / Demand 2 and Demand 3 / Demand 4.
Multiple Distortion Measurements
Meter microcomputer 114 also is configured to calculate distortion
power factor for each element (e.g., distortion Vah / apparent Vah).
Microcomputer
114 also calculates a sum of the element distortion power factors, and VTHD~
ITHD~ ~d
Tdp, all per element. The equations used to calculate these values are well
known. In
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meter 100, the multiple distortion measurements are available for display, and
the
calculations are performed every momentary interval.
Bidirectional Measures
Microcomputer 114 is further configured to determine, for every
momentary interval, the quadrant in which user-selected quantities and other
metering
quantities such as watthours are being measured. As is well known in the art,
the
quadrants are defined by real (Wh) and imaginary (VAR). Meter 100 therefore
tracks
the quadrant in which energy is being received/delivered. Such measurements
are
specified by the user in measurement profile 204.
Transformer Loss Compensation
Microcomputer 114 is configured to compensate for energy losses that
occur within distribution transformers and lines. Such compensation is enabled
if a
user selects this option. Transformer loss compensation (TLC) is applied to
momentary interval per element Wh, Varh, and Vah data. The transformer model
for
1 S loss compensation is based on the following relationships with metered
voltage and
current as variables.
No-load (core) (iron) loss watts are proportional to VZ
Load (copper) loss watts are proportional to I2
No-load (core) (iron) loss vars are proportional to V4
Load (copper) loss vacs are proportional to IZ
Line losses are considered as part of the transformer copper losses.
Every momentary interval, the signed losses for each element (x = a, b, c) are
determined using the TLC constants and the measured momentary interval VZh and
IZh for each element:
LWhFex = iron loss watt hours = Vxzh * G
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LWhCUx = copper loss watt hours = IXZh * R
LVarhFEx = iron loss var hours = (VxZh/h) * VX2h * B/VZ
LVarhCUx = copper loss var hours = IxZh * X
Compensated watt hours and var hours are then determined for each element by
adding the signed losses to the measured momentary interval watthours and var
hours.
Compensated WXh = measured WXh + LWhFEX + LWhCUx
Compensated VarhX = measured Varh + LVarhFEX + LVarCUX
Momentary VAh calculations are made using the compensated watthours and var
hours. The distortion component of the Vah value is not compensated for
transformer
losses.
Pending Actions
When operating in a time-of use mode, a user may desire to implement
a new real-time pricing schedule. In one embodiment, microcomputer 114 also
checks every 15 minutes for a real-time pricing command.
More specifically, microcomputer 114 includes a real-time pricing
mode for executing a specified real-time pricing (RTP) rate for as long as
real-time
pricing is active. Microcomputer 114 enters the RTP mode by, for example, a
dedicated input from a modem board or an I/O board 130, or by a pending or
immediate action. The inputs for RTP include setting an RTP procedure flag
which
indicates whether to enter or exit RTP. A RTP activation delay (time in
minutes)
delays entering RTP after the input has been activated. In one specific
embodiment,
the delay is programmable from 0 to 255 minutes.
During power-up, the saved RTP procedure flag and time remaining
until RTP activation are retrieved from EEPROM 120 by microcomputer 114. After
microcomputer 114 completes its initialization tasks, the following task are
performed.
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If the power outage crossed one or more quarter-hour boundaries,
microcomputer 114 determines whether a pending RTP action was
scheduled for one of the crossed quarter-hour boundaries.
If an RTP action was scheduled, microcomputer 114 determines what
the pending RTP action was, and if the action was to enter RTP,
microcomputer 114 enters RTP and sets the RTP procedure flag. The
RTP activation delay does not delay entering the RTP rate via the
pending action.
If the RTP pending action was to exit RTP, the RTP procedure flag is
cleared.
If the RTP pending action was to exit RTP or no pending RTP action
was scheduled to start during the outage, microcomputer 114 checks
the status of the RTP input and the status of the RTP procedure flag. If
RTP has been activated, or the enter RTP command had been sent prior
to the power failure, microcomputer 114 checks the RTP activation
delay timer. If the timer is zero, microcomputer 114 enters the RTP
rate. Otherwise, microcomputer 114 enters the RTP rate after the timer
expires.
During normal operation, microcomputer 114 checks the status of the
RTP input. When microcomputer 114 detects that the RTP input has changed state
from inactive to active, microcomputer I 14 checks the programmed activation
delay
time. If the delay time is zero, microcomputer 114 enters the RTP rate.
Otherwise,
microcomputer 114 sets the activation delay timer and enters the RTP rate when
the
timer has expired.
During RTP mode operations, microcomputer 114 continues to
calculate data accumulations, and average power factor and demands are
calculated as
when in the TOU metering mode. When the RTP signal is de-activated,
microcomputer 114 checks the status of the RTP procedure flag. If the RTP
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procedure flag is not set, microcomputer 114 exits the RTP mode. Otherwise,
microcomputer 114 remains in the RTP mode until the exit RTP immediate
procedure
is received or a pending exit RTP action is executed.
When microcomputer 114 exits RTP, microcomputer 114 returns to the
TOU rate in effect for the time and date when the RTP ends. Microcomputer 114
processes any unprocessed summations and demand data. For block and rolling
demand, the demand intervals end.
In one embodiment, meter 100 is also able to automatically install a
new TOU schedule when a pending date/time is reached. This feature allows a
new
calendar and/or tier structure with setpoints. Generally, microprocessor 114
checks, at
midnight of every day, for a pending TOU schedule. If, for example, a TOU
schedule
is pending for September 1 at midnight, the pending TOU schedule is loaded and
becomes active.
Voltage Sags and Swells
The term voltage sag refers to a situation in which a phase voltage falls
below a predetermined level, and the term voltage swell refers to a situation
in which
a phase voltage rises above a predetermined level. Voltage sags and swells
generally
are power quality concerns, and typically are associated with brown outs and
similar
events. In meter 100, and if a voltage sag or swell is detected, an event is
logged in
the event log, and the voltages and currents per event (e.g., maximum and
minimum
voltage and current per phase) are stored.
Thresholds are selected to compare the current voltage values against.
Specifically, a sag threshold and a swell threshold are determined. For 120 to
480 V
services, an exemplary threshold is:
INT(Voltage' units x 1 ~ x 1 sample Z x 2 x 1 sec x 22a )
3600 sec SF x voltage hr 3281.25 samples '
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where SF is a scale factor equal to 3125 x 10~. For 57 to 120 V services, an
exemplary threshold is given by the above equation, where SF = 500 x 10~.
Mean voltages can be determined in accordance with the following:
V2x_cycle acum x 2e.
sample count
Given the number of units in a cycle and the sample count, the mean
measurement in
volts is:
# units SF x V z 1 cycle
( ) x [ ] x [3600 sec/hr] x 3281.25 samples/sec x
cycle 2 x 2'6 sample count
# units x SF x 90.122
sample count
The V~ cycle accumulations are accumulated every sample.
Remote Upgrade
Converting meter operation refers to enabling a user to selectively
operate the meter in different metering modes, such as selectively operating a
meter
either a time of use {TOU) or demand metering mode. Specifically, and as
described
below in more detail, a user can convert meter operation from a demand only
mode to
a time of use mode, for example. In one form, the meter has three different
modes.
These modes are the demand only mode, the demand with load profile mode
(sometimes referred to in the art as the demand with timekeeping mode), and
the TOU
mode.
In general, and in accordance with one aspect of the present invention,
a soft switch is associated with optional features, and the soft switch
enables remote
upgrade and downgrade of the meter. The routines associated with the optional
features are stored in meter memory, and when the soft switch for a particular
feature
is enabled, the routine for the enabled feature is executed, and tables become
visible.
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Similarly, when the soft switch for a particular feature is not enabled, the
routine for
the not-enabled feature is not executed and tables are no longer visible.
Examples of optional features enabled and disabled by soft switches
are listed below.
TOU
Expanded Measures
Basic Recording / Self read
Event Log
Alternate Communications
DSP Sample Output
Pulse Initiator Output
Channel Recording/Self reads
Totalization
transformer Loss Compensation
Transformer Accuracy Adjustment
Revenue Guard Plus
Voltage Event Monitor
Bi-Directional Measurements
Waveform Capture
To downgrade meter function, e.g., remotely using a remote computer
communicating with the meter via a communications option board, the meter
memory
is read to determine which soft switches are installed. An operator then
selects a soft
switch to be removed, and the appropriate file associated with the switch is
disabled.
If a significant change will result in removal of a switch, e.g., removing a
TOU switch
in a TOU meter, a warning message is displayed to the operator requesting
confirmation that the selected switch should be removed.
To upgrade a meter, an operator selects a soft switch to be installed.
The soft switch is then enabled in the meter and the particular tables and
routines
associated with the function for that switch are utilized during meter
operations.
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Additional details regarding upgrade/downgrade are set forth in U.S.
Patent Application Serial No. 08/565,464, filed November 30, 1995, now U.S.
Patent
No. 5,742,512, issued April 21, 1998, and entitled ELECTRONIC ELECTRICITY
METERS, which is assigned to the present assignee and hereby incorporated
herein,
S in its entirety, by reference. In this application, at least some operations
descnnea as
being performed in the DSP would be performed in the microcomputer of the
present
meter.
Meter Form Types
Meter 100 includes instruction sets identifying processing steps to be
executed to determine line voltages and line currents for respective meter
form types.
~uch instruction sets are stored, for example, in microcomputer memory.
Microcomputer 114 is configured to receive a control command via optical port
122,
and microcomputer 114 then processes the data received from ADC 112 in
accordance with the selected instruction set.
1 S The underlying process steps to make calculations such as reactive
power and active power are dependent upon the meter form and the electrical
circuit
in which the meter is connected. For example, the meter form types includes
meter
ANSI form 9 and meter ANSI form 16 type forms, the number of elements may be
3,
2, 2 1/2, or 1, and there are a number of circuit configurations in which the
meter can
be connected. The meter form, elements, and circuit configurations affect the
inputs
received by microcomputer 114 and the meter operation. Additional details
regarding
such operations are set forth in U.S. Patent Application Serial No.
08/857,322, filed
May 16, 1997, and entitled AN ELECTRONIC ELECTRICITY METER
CONFIGURABLE TO OPERATE IN A PLURALITY OF METER FORMS AND
RATINGS, which is assigned to the present assignee and hereby incorporated
herein,
in its entirety, by reference. In this application, at least some operations
described as
being performed in the DSP would be performed in the microcomputer of the
present
meter.
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It will be seen that the above-described embodiments of the present
invention provide methods and apparatus for metering electricity usage that
accommodates meter upgrading, and that retain memory in the event of a power
failure. In addition, the methods and apparatus described herein are not
limited to
providing functions that are prestored in the meter.
While the invention has been described in terms of various specific
embodiments, those skilled in the art will recognize that the invention can be
practiced
with modification within the spirit and scope of the claims.
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