CA2130433C

CA2130433C - Electrical energy meter and methods therefor

Info

Publication number: CA2130433C
Application number: CA002130433A
Authority: CA
Inventors: Mark L. Munday; Rodney C. Hemminger
Original assignee: ABB Power T&D Co Inc
Current assignee: ABB Inc USA
Priority date: 1992-02-21
Filing date: 1992-11-05
Publication date: 2000-07-18
Anticipated expiration: 2012-11-05
Also published as: CN1079305A; US5548527A; US5544089A; AU665385B2; ES2214676T3; DE69233248T2; EP0671009A4; EP0857978A2; RU2126974C1; EP0671009B1; UA32555C2; AR247446A1; US5555508A; WO1993017390A1; EP0857978B1; MX9206230A; EP0671009A1; ES2124747T3; DE69233248D1; DE69227128T2

Abstract

The meter includes a first processor (14) for determining electrical energy from voltage (12A, 12B, 12C) and current signals (18A, 88B, 18C) and for generating an energy signal (42, 44, 46, 48) representative of the electrical energy determination and a second processor (16) For receiving the energy signal and for generating an indication signal representative of said energy signal.
An option connector (38) is connected to the first and second processors (14, 16), whereby the energy signal is provided to the option connector (38) and communication connection (40) is provided between the option connector (38) and the second processor (16). It is also preferred to provide the option connector (38) with certain operation signals such as a power fail signal, a master reset signal, an end of demand signal, a KYZ signal, and the potential to communicate with various components of the meter, such as serial data communication, communication signals transmitted and received through an optical port and display signals. It is also preferred for the first processor (14) to include a comparator, connected to receive a precision voltage (22) and a reference voltage (28), wherein a comparator signal is generated whenever the reference voltage exceeds the precision voltage.

Description

WO 93117390 ~ ~ ~ ~C~'/US92f09631 ..~.~

~~o~R~MM~,~~~ ~L~c~r~aioAZ ~~r~~~Y ~~T~R ~ M~~AOOS ~~~~r~~o~~
~'isxd ~f Inventi~ns The present invention relates generally to the field of utility company meters for metering electrical energy.
More particularly, the present invention relates to both ~ el.ectronic ~aatthour meters and meters utilized to meter real axad reactive energy in both the forward and reverse directions.
~~~kgl~ouild of tZDe I3lir~~~ ~oTi Miters for metering the various forms of electrical a~ energy, are well kn~wr~. Ll~tility company meters can be of three general type , namely, e3:ectro-mechanical based meters (output g~ne~at~d by a rotating disk), purely electronic component based meters (output component generated without any rotating pax°ts) grad a hy?arid mechanical/electronic meter. In the 1:5 h~br~:d meter, a so-galled electronic register is coupled, u~ual~y optically; to a.rotating disk: Pulses generated by tla~ rotating disk; fox example by light reflected fr~m a spot painted on the disk., are utilised to ~t~r~exate an electronic output signal, ~t will be appreciated that the use of electronic cemponen~s i.rr electri-c energy meters has gashed considerable acceptance due td their reliability. and extended ambient tampe~ature ranges of operation. Moreover, contemporary electronic n.ignal. pro~essi.ng devices, sucks as microprocessors, ~5 hare a greater accuracy potential for calculating electrical energy use than prior medhanical devices. consequently, dario~ts forms of electranic based meters lave been proposed which are virtually free of any moving parts. Several meters have been proposed which include a microprocessor.
U.S. Patent No. 4,298,839 - Johnston, discloses a programmable alternating current electric energy meter having a radiation responsive external data interface.
The meter is shown to include a metering sequence logic control circuit which in the preferred embodiment is stated to be formed by a single-chip microcomputer, type MK 3870 available from Mostek Corporation of Carrollton, Texas. The logic control circuit is said to be operative to calculate and accumulate different measured parameters of an electrical energy quantity. Current and voltage components are provided to the logic control circuit from a converter which produces current and voltage pulses at a rate proportional to the rate of the particular electrical energy consumed. The converter incorporates a rotating disk.
U.S. Patent No. 4,467,434 - Hurly et al, discloses a solid-state watt-hour meter which includes a current sensing device and a voltage sensing device coupled to a Hall-effect sensing and multiplying device. The Hall-effect device is coupled to a microprocessor.
U.S. Patent No. 4,692,874 - Mihara, discloses an electronic watt-hour meter which includes a single microprocessor and a power measuring device. The power measuring device is described as including an electric power converting circuit and a frequency divider. The electric power converting circuit provides an output pulse, the frequency of which is divided by the frequency divider. The frequency divider, however, is dependent upon a frequency dividing, ratio setting signal generated by the microprocessor.
U.S. Patent No. 4,542,469 - Brandyberry et al, discloses a hybrid type meter having a programmable demand register with a two-way communication optical port. The demand register is said to include a central processing unit such as the NEC 7503 microcontroller. The microcontroller is ~'O 9317390 ~ ~ ~ ,~ J~ ~ ~ PCd'lUS92l09631 -utilized not only for controlling and monitoring the demand register, but also to perform power and energy calculations.
tJ.S. Patent No> 4,884,022 - Hammond et al.
discloses a meter for metering polyphase power sources wherein cycles for each phase are sampled at each degree and converted to a binary representation of amplitude. Conversion is described as being carried out in two steps, the first being a range conversion where the sampled amplitude is evaluated with respect to eleven possible ranges of amplitude or scaling 1C factors. That range data is then stored and the sample is . amplified an accordance with the desired range code and submitted to an analogue to digital converter. A general purpose digital signal processor is said to be utilized for treating the parameters derived from each sample and to ZS develop pulse outputs which can be further processed or displayed by devices of conventional use in the industry. An electronic register is provided which is said to be controlled by a eonventional microprocessor. The implementation of Hammond's range conversiorn scheme results in the energy 20 measurement comp~nen~ts effectively being "hard coded" with the ~artacular m~~.era.ng scheme, thereby significantly reducing the adaptability of the meter for various known applications. The use 'of much a miter in the various utility company applications ~equ~res either keeping several different meter ~5 tykes in inventory, i.e. one meter °~ype for each type of application; or one meter into wh~.ch- all application forms have been incorporated. It will be appreciated that oa~e meter in~,o wh~.ch: all application foams have been incorporated would be exorba.tar~tly expensive 30 'Meters, such as those described above, which incqrporate registers, are generally programmable at two levels. At the first level; firmware can be masked into a register ire a relatively short peri~d ef tizme: At the second level, so-called soft switches can be programmed unto non-35 volatile memory, i:e:, electrcally erasable pr~grammable read on~.y memory, to tell the firmware which algorithms to perform.
Such systems work well for presently provided base metering W~ 93/17390 P~1U~92109631 -~~.3043'~
data. However, such systems cannot change basic meter functions nor are they adaptable to use with additional hardware. While adequate for present applications, such metering systems are significantly non-flexible in relation to future needs and/or developments in both hardware and programmability. ~ , U.S. patent No. 4,077,061.' Johnston et al.
discloses a digital. processing andvcalculating AC electric energy metering system. Thas syste~.:includes a single central processing unit for performing all energy determinations, system control and information display. Although this system does provide energy determination as output signals from the system, the system is not adaptable for modification of basic metering functions from external hardware or in relation to external communication signals.
~Gonsequently, a need exits for an electronic,meter which is designed to be programmable to the extent that basic metering functions can be changed relatively easily and which is economically adaptable for use with additional hardware.
Such a meter w~uld be capable of modification to handle vaxidus meter f~rans, to store calibration constants and to be capable of modification for future metering requirements. The present ihv~n~ion solves the aforementioned problems through the use of .a distributed processing electronic meter 2~ incorporating a metering processor which ig adaptable to multiple metering applications and which is utilized to gerfogm all ~lec~rical energy determinations and a second processor which generates a display ,signal based ~n such electrical energy d~terxainations, serves to cor~~rol the overall operation of 'the meter and~which, provides access to p~o~~ss~ng, storage and display information for future ,, ;
~rardware additi~ns.~
~ua~asry of the Inventi~na The above problems are overcome and the advantages 0~' the invention ' are achieved in methods and apparatus for metera.ng electrical energy in an electronic m~~,er. Such meter includes a first processor for determining electrical energy 2130~~~
from voltage and current signals and for generating an energy signal representative of the electrical energy determination and a second processor for receiving the energy signal and for generating an indication signal representative of said energy signal. An option connector is connected to the first and second processors, whereby the energy signal is provided to the option connector and a communication connection is provided between the option connector and the second processor. Tt is preferred for the option connector to be provided power signals such used by the meter in order to power any electronic components which may be connected to the option connector. Tt is also preferred to provide the option connector with certain operation signals such as a power fail signal, a master reset signal, an end of demand signal, and a KYZ signal. Zt is still further preferred to provide the option connector with the potential to communicate with various components of the meter, such as serial data coginmunication, communication signals transmitted and received thr~uc~h an optical port and display signals. It is also preferred' for the first processor to include a comparator, c~r~nect~d to receive a precision voltage and a reference vo2tage, wherein a comparator signal is generated whenever the reference voltage exceeds the precision voltage. It is also preferred for the meter to include a non-vo~:atile memory such as an electrically erasable programmable read only memory c~nne~ted to the fa:rst aaad second processors, far storing data used by the processors and for stor~.ng inf~rmation generated bY the';proc~ssors.
~~~ef Deseriptio~a ~f the Drawinost 3~ The present invention will be better understood, and itsinumerous,objects and advantages will become apparent to those skilled in the art by reference to the following detailed description of the invention when 'aken in conjunction with the following drawings; in which:
Fig. 1 i~ a black diagram of an electronic meter const~cucted in accordance with the present invention;

W~ 93t1739U ~FC°i'tUS92t09631 -s-Fig. 2 is a block diagram of the A/D&DSP processor shown ~n Flg . ~ ;
Figs. 3A-3E combine to provide a flow chart of the primary program utilized by the microcontroller disclosed in Fig. 1;
Fig. 4 is a flow chart of the download program utilized by the microcontro3ler~v~shown in Fig. 1;
Fig. 6 is a schematic diagram of the optical port disclosed in Fig. 1;
to Fig. 6 is a schematic diagram of the resistive divides and precision reference disclosed in Fig. 1.
Fig. '3,is a schematic diagram of the 5 volt linear power supply shown in Fig. 2; and Fig. 8 is a schematic diagram of various electronic button switches utilized by the microcontroller shown in Fig.
1.
Detailed Descri~tioats new and novel meter for metering electrical energy is shown in Fig. 2. and generally designated 10: It is noted ~0 at the outset that this meter is constructed so that the future implementation of higher level metering functions can b~ supported. Such future implementation feature is described ix~ gi'sater detail herein:
Meter 10 is shown to include three resistive voltage da:va:der networks 12A, 127, 12C; a first proces~Or - an AD~/DSP
(~nalag-t~-digital convexter/digital signal processors chip 14 o a second pro~~ssor ~ microcor~t~o~.ler is which in the pr~fe~r~d embodiment- is a Mitsubishi Model 50428.
m~.crocontl~oller; three current sensors 1.8A; 1~B, 18C; a 12v switching p~wer supply 2Q that is capably of receiving inputs in the range of ~6-528v; a 5V lineax° power supply 22; anon-, volatile power supply 24 that switches to a battery 26 when 5V supply 22 is inoperative; a 2.5V precision v~ltage reference 28; a liquid crystal disp~:ay (LGD~ 30; a 32.768 kHz 35: oscillator 32; a 6. 2208 MHz oscillator 34 that ~xovides ~im~.ng signals to c~aip 14 end whose s~.gnai is cdivided by 1 ~ 5 to provide a 4:1472 M~iz clock signal to mi~rocontroller 16; a 2 Pc°~ius9zio~6~~
wo ~~> ~ ~~~~
kByte EEPROM 35; a serial communications line 36; an option connector 38; and an optical communications port 40 that may be used to read the meter. The inter-relationship and specific details of each of these components is set out more fully below.
It will be appreciated that electrical energy has both voltage and current characteristics. In relation to meter 10, voltage signals are provided to resistive dividers 12A-12C and current signals are induced in a current transformer (CT) and shunted. The output of CT/shunt combinations 18A-18C is used to determine electrical energy.
First processor 14 is connected to receive the voltage and current signals provided by dividers 12A-12C and shunts 18A-i8C. d~s wild: be explained in greater detail below, prbcessor l4 converts the voltage and current signals to voltage and current digital signals, determines electrical energy fgom the voltage and current digital signals and :generates en energy signal representative of the electrical energy determination. Processor 14 will always generate 20: watthour delivered ("~~TThr Del) and watthour received (Whr Rec) signals, and depending on the type of energy being metered, will ~~ne~'e~e either volt amp reactive hour delivered (VARhr Del)/volt amp reactive hour received ('VARhr Rec) signals or volt amp hour delivered ('~Ahr Del)/volt imp hhur received (VAhr Recd signals. Zn the preferred emb~adiment, each trans~aion: on conductors 42-48 (each transit~.on from logic low t~: logic' high or vice versa) is representative of the, measurement of a u,niit ' of energy. Second pr~rc~ssor 16 is connected to first processor 14. As will be explained in gre~tex detail below; processor 16 receives the energy signals) and generates an indicatian s~.gnal representative of th.e'energy signal.
In relation to the preferred embodiment of meter 10, currents and voltages are sensed using convexationa.l current 3~ transforaners (CT's) and resistive voltage dividers, ~esp~ctively. The appr~priate multiplication as accomplished in a new integrated circuit, i.e. processor 14. Although WU 93/17390 P~.'T/US92109631 ,~~~;
-described in greater detail in relation to Fig. 2, processor 14 is essentially a programmable digital signal processor (DSP) with built in analog to digital (A/D) converters. The converters are capable of sampling three input channels simultaneously at 2400 Hz each with a resolution of 21 bits and then the integral DSP performs various calculations on the results.
Meter 20 can be operated as either a demand meter or as a so-called time of use (TOU) meter. It will be 1.0 recognized that TOU meters are becoming increasingly popular due to the greater differentiation by which electrical energy is billed. For example, electrical energy metered during peak hours will be billed differently than electrical energy billed during non--peak hours: As will be explained in greater detail 1~ below, ffirst processor 14 determines units of electrical energy while processor 1.6, in the TOU mode, gualifies' such energy units in relat~.on to the time such units were determined, i.e. the season as well as the time of day.
All indicat~rs and test features are brought out 20 through the face of mater ~.0; either on LCD 30 or through optical communieati~ns port 40. Power supply 20 for the electronics is a switching power supply feeding low voltage linear stapply 22. Such an aPProach all~ws a wide operating Vn~tage range for meter ~0.
25 Tn the preferred embodiment of the present invention, the so-called standard meter comp~nents and r~gisi~er electronics arm for the first time all 1~ca~ed on a sir~gl~ printed circuft board (nat shown) deffined as an~
electronics assembly. This electronics assemba.y houses power 30 s~ppl'ies 20, 22, 24 and 28, resistive dividers l2A-:12G for all .~hre'e phases,; the shunt resist~r porti~n of 18A-18C;' os~il3ator 34, processor 14; processor ~6; reset circuitry , (shown in Fig. 8), EEPROM 3~, oscillatgr 32, optieal port comg~onents 40; LGD 30, and an option board interface 38. When 35 this assembly is used for demand metering, the billing data is stored in EEPROM 3~: This same assembly is used for TOU

iV(3 93/17390 ~ ~ ~ ~ ~ ~ ~ P~.TliJS92/0963i f.-~.., i -metering applications by merely utilizing battery 26 and reprogramming the configuration data in EEPROM 35.
Consider now the various components of meter i0 in greater detail. Primary current being metered is sensed using conventional current transformers. It is preferred for the current transformer portion of devices 18A-18C have tight ratio error and phase shift specifications in order to. limit the factors affecting the calibration of the meter to the electronics assembly itself. Such a limitation tends to enhance the ease with which meter 10 may be programmed. The shunt resistor portion of devices 18A-18C are located on the elects~nics assembly,described above and are preferably metal film resisters with a maximum temperature coefficient of 20 PPm/°C.
The phase voltages are brought directly to the elactrox~ic assembly where resistive dividers 12A-12C scale these inputs to processor 14. In the preferred embodiment, the e3ectr~nic components are referenced to the vector sum of each line voltage for'three wire delta systems and to earth 2Q ground: for all other services. Resistive div~.sion is used to divide the input voltage so that a very linear voltage with minimal phase 'shift over a wide dynamic range can be obtained.
This.in combination with a switching power apply allows the wide, voltage operating range to be implemented.
25Referring brief3:y to Fig: 6, each resistive divider consists ~f two 1-Meg, 1/2 watt resistors SD/52, 54r56 and 58/60,', res~ectivel~. Resistors 50-6~ are used to drop the line voltage at an acceptable watt loss. Each-resister pair feeds a third resistor 62, 64 and 66, respectively. resistors .30 62-66 are metal film resisters having a m~xi~um temperature coefficient of 25 ppm/°C. This , combinati.on is ; very inexpensive compared to other voltage sensing °techniques.
Resistors 50-60 have an operating voltage rating of 3~~ Vrms each. These resistors have been individually tested with the 35 6 kV IEEE 587 impulse waveforms to assure that the resi tance i stable and that the devices axe not destroyed. Resistors 62-66 scales the input voltage to be less than 1 Volt peak to peak to processor 14. It is noted that resistors 62-66 can be in a range from about 100 ohms to about 1 k ohms in order to assure this maximum peak to peak voltage and still maintain maximum signal.
On grounded, three wire delta systems, those components of the electronics assembly operating on logic voltage levels (including the battery connector) can be at an elevated voltage. In such situations, the two, 1 Meg resistor combinations (50/52, 54/56, 58/60) provide current limiting to the logic level electronics.
The worse case current occurs during testing of a 480 V, 3 wire delta meter with single phase excitation.
It will be appreciated that energy units are calculated primarily from multiplication of voltage and current. The specific formulae utilized in the preferred embodiment are listed in Table 1. This especially preferred embodiment allows four wire delta applications to be metered using a four wire wye meter executing the four wire wye equations in Table 1. However, for purposes of Fig.
2, such formulae are performed in processor 14. Processor 14 includes an analog converter 70 and a programmable DSP 72. Converter 70 includes three three-chanel, over-sampled, 2nd order, sigma-delta A/D converters, depicted as a 9 channel ED analog-to-digital converter 74. The 6.2208 MHz clock signal is divided by 3 such that each A/D samples its input at 2.0736 MHz. Each A/D
performs a 96:1 reduction or averaging for each input that results in an effective sample rate of 2.4 kHz on each of the three inputs per A/D. The resolution of these samples is equivalent to 21 bits, plus sign. It is noted that such a E~
analog-to-digital conversion scheme results in a correct convergence by each A/D for each sample converted. It is recognized that the bandwidth for such a conversion scheme is relatively small, however, the frequency of the voltage and current being converted is also relatively small.

WO 93/17390 PC'T/U592/0963y 2~30~33 Tn the preferred embodiment, the three voltage inputs, Va, Vb and Vc are sampled by one of the A/D's and the three current inputs Ia, Ib and Ic are sampled by a second A/D. The third A/D is used to sample either the voltage or current input of the B phase. Such sampling of the voltage or current input of the B phase~is done because so-called 2 1/Z element meters require the combination of the B phase current with one or both of the other phase currents. In addition, so-called two element meters require the H phase ~croltage to be combined with the other phase voltages to produce the line to line voltage. Having a third A/D enables triese terms to be sampled simultaneously, thereby improving the measurement accuracy. This also improves the signal to noise ratio within processor 14.
DSP 72 is a reduced instruction set processor (RISC) which computes the desired energy quantities frog the a~nverted voltage and current samples. DSP 72 is shown to include a random access memory (RAM) memory ?6 having a capacity ~f 256 bytes ~f data. Memory 76 is used to store computations and the ubroutine stack. A read only memory (ROM) ~78 is .also shown and has a capacity of 640 bytes of data. Memory 78 is used to store those petering subroutines common to all :energy calculate~n: Another RAM memory 80 is depicted and has a capacity of 256 bytes of data. Idemory 80 25' is' used to store the main line program and specialised subroutines of DSP ?2.
DSP ?2 ~a also shown to include multiplier 82 and an accumulator 84 for processing the voltage and current digital signals thereby generating electrical energy informati.c~n. There is also included. arithmetic subtraction ur~it~ 86 interposed between multiplier 82 and' acoumulato'r 84.
From, the foregoing, it should be appreciated that program R~M, ioa. memory 76 is defined at the ~xide via level.
As this defining step occurs relatively late in the manufacturing process for processor 14, changes care be fade to such programming with minimal effort:-CVO 93117390 P'~i'IUS92/09631 Calibration constants for each phase and certain potential linearization constants are stored in memory 80.
Memories 76 and 80 are serially down-loaded from EEPRt~M 35 by microcontroller 26 on power-up of meter 20. Such an embodiment allows the benefit of being able to provide various meter forms economically, to. calibrate without hardware .
modification, and permits the future addition of metering VAR
or VA based on the per phase Vrms and Irms. The formulae for such operations are included in Table 1. Furthermore, the calculation of future, yet undefined, complex metering quantities could be obtained by merely reprogramming processor 14.
Processor 14 also contains a crystal oscillator (not shown), serial interface 88, power fail detect circuitry 90, 25 and potential present outputs B and C. The crystal oscillator requires an external 6.2208 MHz crystal oscillator 34.
Processor- 14 uses this frequency directly for driving the DSP
and indirectly for the A/D sampling. This frequency is also operated upon by clock generator 92 which serves to divide the 2~ output of oscillator 34 (input to processor 14 at KIM and X~UT) by 2.5, to buffer the divided clock signal and to output tlae divided clock signal at CK to processor 26 as its clock.
This clock output is specified to work down to a supply voltage of 2:0 VDC.
25 Serial interface 88 is a derivation of the Signetics ITC buss 4n~ serial address is assigned to processor 24.
This address accesses one of the four DSP control registers.
All information must pays through DSP data register 94 after writing the DSP address register. X11 memory, registers, and 30' ~utputs of processor 24 can be read serially. A chap select line CS has been added to disable the communicate~ns buffer.
~h~ input CS is connected to and controlled by processor 26: , Power fail detection circuit 90 is a comparator which compares a divided representation of the supply voltage 35 t~ a precision reference. The comparator's output at A
concurrently provides a power fail signal grad an indication of the presence of A phase voltage. Upon power fail, it is ~1'O X3/17390 ~ ~ ~ ~ 4 J ~ PGT/US92109631 °
preferable to reset processor 14. In such a situation, the output pins Whr, Whd, etc. are forced to logic low voltage levels. hdditionally, processor 34 goes into a lower power mode to reduce the current draw on power supply 20. In this lower power mode the comparator and oscillator operation are not affected, but DSP 72 ceases~to operate.
The power failure voltage PF is generated by dividing the output of supply 22 to generate a voltage which .
is slightly greater than 2.5V. In the preferred embodiment, a resistor voltage divider provides PF. Since PF is generated in rela~.ion to the Phase A voltage (Fig. 1), its presence is an indication that the Phase A voltage is also present.
In order to appreciate how the reference voltage is generated consider Fig. 7: There is shown in greater detail 'the components included in linear power supply 22. The 5V
output of supply 22 is pr~vided at 9s in Fig. 6. Resistor 98 ahd diode x.00 combine to generate a precision 2.5V reference ~r~lt~gee It is noted at this point that Va, Vb, Vc, Ia, Ib and Ic are each provie~ed to proczssor 14 in reference to VREF.
Consider again processor 14 as sh~wn in Fig. 2 . The phase~B and C potential indicators outputs are under control of DSP 72. The E output ~.s normally a logic level output.
The C output also pro~rides the power line time base function (nrrte that phase C i5 present in all applications). To m~nima:~e noise at the power line fundamental, this time base is at two times the power line fundamental.
The M37428 microcontroller 16 is a 0502 (a ~~aditional 8 bit microprocess~r) derivat~:ve with an expanded instruction set for bit test and manipulata.on. this 3~ ma.crocon~roller includes'substantial functionality including internal hCD drivers (128 quadraplexed segments) , 8 kbytes of ~OI4, 384 bytes of RAI~l,; a full duplex hardwars DART, 5 timers, dual clock inputs (32:768 kHz ahd up to 8 MHz) , and a low power operating m~de.
During n~rmal operation; processor ~,6 receives the 4.1472 MHz clock from processor 14 as described above. Such a clock signal translates to a 1:0368 MHz cycle time. Upon W~ 93/17390 PCT/US92/~9631 ~.3 a 43 ~ _ power fail, processor 16 shifts to the 32.768 kHz crystal oscillator 32. This allows Iow power operation with a cycle time of 16.38 kHz. During a power failure, processor 1.6 keeps track of time by counting seconds and rippling the time .
forward. t~nce processor 16 has ripgled the time forward, a WIT instruction is executed which. places the unit in a mode where only the 32:768 kHz oscillator and the timers are operational. t~hile in this mode a timer is setup to "wake up"
processor 16 every 32,768 cycles to count a second.
Consider now'the main operation of processor 16 in xelation to Figs. 3A-3E and Fig. 4. At step 1000 a reset signal is provided to microcontroller 16. As wall be appreciated in relation to the discussion of Fig. 5, a reset cycle occurs whenever the voltage level V~ rises through approximately 2.8 volts. Such a condition occurs when the meter is first powered up.
At step 1002, microcontroller 16 performs an init~:alize operation; wherein the suck painter is initialized, the internal'ram is initialized, the type of liquid crystal display is entered into the display driver portion of microcontx~oller 16 and timers which require ihitializatioa~ at power up are initialized. It will be noted that the operation of step 1002 does not need to be performed for each power failure occurrence: Following a 'power failure, microcantroller 16 at step 1004 returns to the main program at the point indicated when the power returns:, ~7pon 3nitial.~, power up cr the 'return of p~wer after a power failure, micro~ontraller 16' performs a xestore functi~n. At step 1006, microcontroller 3~6 disables pulses transmitted by processor 14. These pulses are disabled by pxc~vi~ing the appropriate signal restore bit. The presence of this bit indicates that a restore aperataon is occurring and that pulses generated during that time should be ignored.
Having set the signal restore bit; microcontr~aller 16 determines at step 1008 whether'the power fail signal is present. If the pawer fail signal is present, ~nicrocontroll~r 16 jumps to the power fail routine at 1.010. In the power fail W4 93/i 739~ PCT/US92/09631 - 1,5 -routine, the output ports of microcontroller 16 are w=itten low unless the restore bit has not been set. If the restore bit has not been set, data in the microcontroller 16 is written to memory.
If the power fail signal is not present, microcontroller -16 displays segments at step 1012. At this time, the segments of the display are illuminated using the phase A potential. It will be recalled that phase A potential is provided to microcontroller 16 from pr ocessor 14 . At 1014 , the UART port and other ports are initialized at 1016, the power fail interrupts are enabled such that if a falling edge is sensed from output A of processor 14, an interrupt will occur indicating power failure. It will be recalled that pr~cesscar 14 compares the reference voltage 'GTREF to a divided voltage generated by the power supply 20. Whenever the power supply voltage falls below the reference voltage a power fail Gandi~ion as occurring.
At step 1018,' the downloading of the metering ihtegrated circuit is, performed. Such downloading operation is described ~.n greater detail in relation to Fig. 4. At step 1020, the timer ihterrupts are enabled. It will be appreciated that certain tasks performed' by micr~controller 16 arc time dependem. Such tasks will require a timer interrupt when the time for performing uch tasks has arrived.
At X022, the self-test subroutines are performed.
Although no particular self-bests subroutine is necessary in oxder to practice the present invention, such subroutines can include a check to detez-~aine if proper display data is prea7ent. -.It, ~~s n~t~.d thatdata i.S ~Jtored i.n relat~.~n ao class d~eignation and that a value is assigned to each class such that the sum~of the class values equals a specified number.
If any d,asplay data is missing, the condition of the class values for data which is present will not equal the specified sum and an error message will be displayed. Similarly, ~nicroeontroller 16 compares the clock signal generated by processor 14 with the clock signal generated by watch crystal i~VO 93!17390 PCT/US92/09631 -32 in order to determine whether the appropriate relationship exZ.St 'nJ .
~Iaving completed the self-test subroutines, the ram is re-initialized at 1024. In this re-initialization, certain load constants are cleared from memory. At 1026, various items are scheduled. For example, the display update is scheduled so that as soon as the restore routine is completed, data is retrieved and the display is updated. Similarly, optical communicati~ns are schedulea~wherein microcontroller 16 determines whether any device is~ present at optical port 40, which device desires to communicate. Finally, at 1028 a signal is given indicating that the restore routine has been completed. Such a signal can include disabling the signal restore bit: Upgn such an occurrence, pulses previously disabled will now be considered valid. Microcontroller 16 now moves into the main routine.
At 1030, microcontroller 16 calls the time of day processing routine. In this routine, microcontroller 16 looks at the one second bit'of its internal and determines whether 2t1 the clock needs to be changed. For example, at the beginning and end of Daylight Savings Time, the clock is moved forward and hack ~ne h~ur, respectively. In addition, he ime of day processing routine sets the minute change flags and date change flags.- As will be appreciated hereinafter, such flags ~5 are periodically checked end processes occur if such f lags are preseht.
'It will be noted that there az~e two real time interrupts scheduled in mi:crocontroller 16 which ark not shown.
in Fig. 3, namely the roll minute interrupt and the day 3d interrupt: At th,e' beginning of every-minute,-certain minute tas~s occur. Similarly, at the beginning of every; day;
certain day tasks occur. Since such tasks are not necessary to the practice of the ,presently claimed inventian, no further details need be provided.
35 At 1032, microcontroller 16 determines whether a selft-reprogram routine is scheduled. If the self-reprogram routine is scheduled, such routine is called at 1034. The CVO 93!17390 PCTlUS92109631 ~~~~43~
''«' - i~ -self-reprogram typically programs in new utility rates'which are stored in advance. Since new rates have been incorporated, it will be necessary to also restart the display. After operation of the self-reprogram routine, microcontroller 16 returns to the main program. If it is determined at 1032 that the self-reprogram routine is not scheduled, microcontroller 16 determines at 1036 whether any day boundary tasks ire scheduled. Such a deteranination is made by determining the time and day and searching to see whether any day tasks are scheduled for that day. If day tasks are scheduled, such tasks are called at 1038. If no day tasks are scheduled; microcontroller 16 next determines at 1040 whether any minute boundary tasks have been scheduled.
It will be understood that since time of use switch points occur at minute boundaries;'for example, switching from one use period to another; it will be necessary to change the data storage locations at such a point. If minute tasks are scheduled; such tasks are called at 1042. If minute boundary tasks have not been scheduled; microcontroller 16 determines at 1044 whether any self-test have been scheduled. The self-tests are typically scheduled to occur ors the day boundary.
As indicated previously, much self-tests can include checking the accumulative display data class value to determine whether the sum is equal to a gres~ribed value. If self-tests are scheduled, such tests are called at 1046. If no self-tests are scheduled microcc~ntz~oller I6 determines at 1048 whether any season change billing data copy is scheduled. It w:.ll be appreciated that as season changes bilping: data changes.
Consequently, it will be necessary'for microcontroller 16 to store energy metered for one season and begin accumulating energy metered for the following season: If season change bill'~ng datacopy is scheduled, such routine is called at 1050. If no season change rautine is scheduled, microcantroller l6 determines at 1052 whether the self-redemand reset has been scheduled. If the self-redemand reset is scheduled, such routine is called at 1054. This routine requires ma.crocontroller 26 to in effect read itself and store V~'Q 93/17390 PCT/US92/09631 ~.~;..

the read value in memory. The demand reset is then reset.
If the self-demand reset has not been scheduled, microcontroller 16 determines at 1056 whether a season change demand reset has been scheduled. If a season change demand reset is scheduled, such a routine is called at 1058. In such a routine, microcontroller 16 reads itself and resets the demand.
At 1060, microcontroller 16 determines whether button sampling has been scheduled. Reference is made to Fig.
20 8 for a more detailed description of an arrangement of buttons to b~ ppsitioned on the face of meter 10. Button sampling will occur every eight milliseconds. Consequently, if an eight millisec~nd period has passed, microcontroller 16 will determine that button sampling is scheduled and the button sampling routine will be called at 1062.
If button sampling is not scheduled, microcorat~oller 16 determines at 1064 whether a display update has been scheduled. This routi.~e causes a new quantity to be displayed on 1;CD 30. As determined by the sgft switch settings menti~ned above, disp2ay updates are scheduled generally for every three-six seconds: If the display is updated more frequently, it may not be possible to read the display accurately. If the display update has been scheduled, the display update routine is called-at 2066.
If a airplay update has not been scheduled, microdontr~ller 16 determines at 1068 whether an annunciator flash is scheduled. It will be recalled that certain ~nnunciators on the display are made tea f lash. ! Such- f lashing typically occurs every half second. If an anr~unciator flash 3Q is scheduled, such a routine is .called at 10'70. If no annunciator f .ash a.s scheduled, microcontroller 16 determines at 1072 whether optical cpmmunication has been scheduled. It will be recalled that every half seGOnd microcontroller 16 determines whether any signal has been generated at optical 35 port: If a signal has been generated indicating that optical communications is desixed, the optical communication routine will be scheduled: If the optical communication routine is P~.T/US92/fl9631 WO 93/1739~

scheduled, such routine is called at 1074. This routine causes microcontroller 16 to sample optical port 40 for communication activity.
If no optical routine is scheduled, microcontroller 16 determines at 1076 whether processor 14 is signaling an error. If processor 14 is signaling an error, microcontroller 16 at 10?8 disables the pulse detection, calls the download routine and after performance of that routine, re-enables the pulse detection. If processor 14 is not signaling any error, microcontroller 16 determines at 1080 whether the download program is scheduled. If the download program is scheduled, the main xoutine returns to 1078 and thereafter back to the main program.
If the do~rnload program has not been scheduled or after the pulse detect has been re-enabled, microcontroller l6 determines at 1082 whether a warmstart is in progress. If a warmstart is in progress, the power fail interrupts are disabled at 1084. The pulse campul:ation routine is called after which the power fail interrupts are re-enabled. It will be noted that in the warmstart data is zeroed out in order to provide' a fresh start for the meter. Consequently, the pulse computation routine performs the necessary calculations for energy previously metered and places that computation in the apgrogriate point in memory. If ~ warmstart is not in ;progress, microcontroller 16 at 1084 updates the remote relays. Typically,' ;the remote relays are contained ors a board other than the electronics assembly board.
Referring now to Fig: 4', the program for d~wnloading processor 14 will be describede At 1100, microcontroller 16 30. enters the program. ~.t 102; the schedule indicating that a metering download should take place is cleared: At 1104, Mieroc~ntx°oller 16 initializes the communication bus, ~ihich in the preferred embodiment is INTB. At 1106, microcontrolle~
16 resets and stops processor by way of an interrupt or:
pr~cessor i.4. However, if there is a communications error between microcontroller 16 and processor l4, microcontroller 16 at 11:08 sets a warning and -schedules a download of W~ 93J17390 PCTJUS92J09631 a 2 0 _ .....,..
processor 24~. After 1108 the downloading program is terminated, microcontroller 16 returns to the main routine.
At 1110, microcontroller reads and saves the pulse line states. It will be recalled that as processor 14 makes energy determinations, each unit of energy is represented by a logic transition on outputs 42-48 (Fig.l). At 1110 the state of each output 42-48 is saved. At 1112, microcontroller initializes A/D converters 74, if a communication error occurs, microcc~ntroller proceeds to 1108. At 1114 the digital lp signal processing registers 94 are initialized. At 1116 program memory 78 is downloaded to memory. At 1118, the data memory 80 is downloaded to memory. At 1120, processor 14 is stated. zf a communication error occurs at any of steps 1114-2120, microcontroller 16 again returns to x.108. At 1122, any warning messages previously set at 1208 are cleared. At 112 4, microcontrdller l6 returns to its main program.
A11 data that'is considered non-volatile for meter 10, is stored in a 2 kbyte EEPROM 35. This includes conf ic~uration data (including the data for memory '76 and memory 80), total kWh, maximum and cumulative demands (Rate A demavds in TOU) ; historic TOU data, cumulat~.ve number of demand resets, cumulative number of power outages and the cumulative number of data altering communications. The present billing period TOil data is stored in the RAM' contained t~tithi.n processor 16. ''As long as the microdontroller 16 has adequate power, the RAM c~ntents and real time are maintained and the m~:crocontroller 16 will not be reset (even in a demand register):
As indi~ated,previously, opex°ationa~, constants are 3D. stored in EEPROM data. Idiicrocontroller 16 performs checks of these memory; areas by adding the Glass designations for various e3ata and comparing the sum to a reference number. For example, the data class is used to define the 256 byte block of program memory. Appended to the 256 bytes of program in this data class is the DSP code identification, -revision number, and the checksum assigned to this data class . The operational constants consist of the calibration ce~nstants and data RAM initial values, the meter's secondary Ke and Kh, and information that the microcontroller must use to process the meter's data.
LCD 30 allows viewing of the billing and other metering data and statuses.
Temperature compensation for LCD 30 is provided in the electronics. Even with this compensation, the meter's operating temperature range and the LCD's 5 volt fluid limits LCD 30 to being triplexed. Hence, the maximum number of segments supported in this design is 96. The display response time will also slow noticeably at temperatures below -30 degrees Celsius.
Referring now to Fig.S, optical port 40 and reset circuitry 108 are shown in greater detail. On power up, reset 108 provides an automatic reset pulse to processor 16. In operation, circuit 108 acts as a comparator, comparing a portion of the voltage generated by power supply 22 to the voltage provided by non-volatile supply 24. Whenever the voltage generated by power supply 22 either falls below or rises above that of the non-volatile supply, such a condition is an indication that the meter has either lost power or power has been restored and a reset signal is provided to processor 16.
Optical port 40 provides electronic access to metering information. The transmitter and receiver (transistors 110 and 112) are 850 nanometer infrared components and are contained in the electronics assembly (as opposed to being mounted in the cover). Transistor 110 and LED 112 are tied to microcontroller 16's DART and the communications rate (9600 baud) is limited by the response time of the optical components. The optical port can also be disabled from the DART (as described below), allowing the UART to be used for other future communications without concern about ambient light. During test mode, the optical port will WO 9311739 PCf/US92l09631 22 - 'i.
echo the watthour pulses received by the microcontrolle'r over the transmitting LED 112. While in test mode microcontroller 1~ will monitor the receive Line 114 for communications commands.
One feature which results from the distributed processing scheme described above is the adaptability or expandability of the invention in future applications. To this end, option connector.38 will play a key role. As shown in Fig. 1, option connector provides a connection from i0 processor 1~ to the outside world. Through connector 38 data output from processor l4 to EEPROM 35 or data output to processor 16 can be monitored. As will be described below, communication with processor 16 can occur since connector 38 is directly connected to several ports on processor 16. Thus through option connector 38, communication with processor is is possible and the ~per~tion of processor 16 may be modified.
For example, connector 38 may be used in order to csanvert meter l0 effectively ~.nt~ a peripheral device for another microcontroller ~no~ shown). Option connector 38 might be a0 used i.n relation ~o a modem in order to acca~s pieces of data or to operate optical port 40 in some desired fashion.
Connector 38 may also be used in relation to so called 3rd party services. In such- situations, third parties may be contracted to service the meter using their own equipment.
Through connector 38 it may be possible to more readily adapt such equapm~nt to be capable of servicing meter 10: Odnnector 38 array also be utilised for the connecti~n of a de~rice for the stbrage of an enere,~Y useprofile. Such devices require non-.
~olati:le supply voltages. The features made available on cOnnecta~ 38'makes it possible to "piggy-b~Ck°' such a device ~m miter 1~0 Asindicated above, it is desirable f or meter ~ 10 to economically perform existing polYghase demand arid time-of-use (T~U) metering as caell as be the platform fox- future metering products: Unfortunately, little is known ab~ut the future.
The problem therefore is how one allows for the changes the future might bring. The approach taken by the invention, ~O 93!17390 ~ ~ ~ ~ ~ ~ ~ PCl'/LJS92/09631 ~..~,.r - 2 3 -allows the electronics in meter 10 to act as a peripheral d~«ice to an option board (not shown) connected to option c:w~ector 3~, while supplying nominal power requirements for the option board. All power, signals, and communications to the option board are provided over a 20 pin connection.
Meter 10 provides the following power signals:
V+ A semi-regulated~l2VDC to lSVDc supply (the output of supply 20);
5V A regulated 5V volatile supply (the output of supply 22);
VDD A regulated 5V non-volatile supply (the output of supply 24); and Gnd The negative reference.
In the preferred embodiment, the option board is ~5 allowed a combined current draw of 50mA on these three supply signa3a. The option board can be allowed to draw up to 100~,A
from a supercapacitor contained in the output portion of supply 20 and battery 26 via supply 24 during a power outage, however, such an arrangement will reduce battery life.
2~ ~,eferrir~g to Fig: 1, meter 10 also provides the following operational: signals to option ~annector 38:
pFail Preferably logic level low (0) indicates the absence of AC power;
y~~ster Reset - A logic level low ( 0) 25 generated by circuit 1~8 (Fig. 5). used to reset the microcontroller upon loss of tTDD ' (preferably defined as VDD falling bel~w 2.~ to 2.2 volts);
Alt Ah ~~h~ or, duplication of the alternate 3p: display button position (determined by processor 16 at 106Q);
y ~ - Reset An'echo or' duplication of the demand reset butt~n position (determined by processor Z6vat 1060);
35 EOI End of demand interval indication, generated by processor 16 in relation to the main program at 1052, preferably high CVO 93/17390 PCf/US92A09b31 - T.a:i for one second at the end of the demand interval;
KYZ1 A KYZ output signal of watthour pulses subject to a pulse frequency divider and .
a watthour accumulation definition, wherein the accumulation definition allows .the KYZ signal to repeat the watthou-rs delivered pulses or a combination of watthours delivered and watthours received pulses;
KYZ2 A KYZ output signal of the VARhour or VAhour pulses also subject to the KYZ
divider and accumulation definition;
WHR The watthour received pulse train from prodessor 14; and VAR~iR The VARhours received pulse train, from processor 14.
~y provida,a~g the PF"ail signal to option connector ~s; determinations can be made of when AC power is no longer 2~ present. In the preferred embodiment, meter 10 guarantees that IOO~s of p~w~r supply remains when the pFail signal is g~nexateda The Master Reset signal can be used to reset any m~;~~oprocessor that may be connected to option connector 38, if it is powered from the V~ supply: ~therwi~e, an option 2~ board mi~crboomputer can be reset from a time delay on the P~'a~.l lix~~e. The KYZ~., hYZ2, WfiR, and VAR~iR signals can be uaSed ' t~ m'onl~or t~Pr Various power f l~w meass°7urP..mente~'J a ~.'he ~~I
signal can be used °to synchronize demand intervals b~t~aeen pgoce~sor 1~ and a ~niaroc~mputer connected to ~ption ca~nnector 3~.
Meter 10 further provides the following cs~mmunication~s connections SC1 Serial Clock - connection to serial co~,unications line 3~particularly the serial clock c~nnection with serial interface 88 Fig. 2) , wherein a serial W~ 93/17390 PC('/~IS92/a9631 2~~Q~3~
Z
clock is transmitted conforming to the IZC serial protocol;

SDA Serial Data - connection to serial communications line 36, particularly the serial data connection with serial interface 88 (Fig. 2) , wherein Serial bi-directional serial data is transmitted conforming to the I2C serial protocol;

R~ A connection to the serial receive 3.0 communications line connecting processor 16 and optical port 40;

TX A connection to the serial transmit .

communications line connecting processor 16 and optical port ~0;

1~ OPE Optical Port Enable - a connection to processor 16 and optical port ~0 ~rherein a 1~g~.c level high (1) allows access to optical port 4~ by the RX and T~f signals provided to option connector 38 by an 20 option board;

OPS Optical Port Select a connection to processor 1,6, wherein a 1~gic level high (1)'r~sults in processor 16 controlling the drive to optical port ~ 0 and logic 2,~ le~tel low ( 0 } allows a micr~proceseor connected to option connector 3~ to drive optical port ~40; and Display Select a conne~~i~n to~

processor -16 wherein a logac level high 30 (1)results in processor 16 e~nt~olling the drive to liquidcrystal: ' displ.~ay 3 ~

and logic level lows (O) allows a anicroprocessor conhected ~o option connector 38 to dri~re display 30. ., 35' The SC1'and SDA connections c~uld be used ~o drive an IBC Z/~ expander which in turn would p~ovade signals ~r~m meter 10 to multip le output relays. The R~, ~'X: end OPE

!~~ 93/17390 PCT/IJS92/09631 corinections would normally be used to drive optical port 40.
If the OPS line is pulled low, processor 16 would no longer attempt to drive optical port 40, but instead would listen at 9600 baud for an option board microcomputer to "talk" to processor 16. When the OPE line is high, processor 16 is commanded to assume that the option board is communicating out optical port 40 and thus to ignore the communication. This allows meter 10 through processor 16 to become a communications and data processing peripheral to option connector 38. EEPROM 35, in the preferred embodiment has a56 byes of extra memory spice that can be accessed by through option connector 38 via the normal communications protocol.
In such a situation, meter 10 can be either a data storage or configuration storage peripheral.
25 When the signal on the D8 connection is high, pgacessor 16 controls display 30 per information processor 16 stores in EEPROM 3 S : It wi 11 be noted that, in the pref erred embodiment; the li.quicl crystal display is controlled in relation to information contained in a display table (not shown) which table contains identifier and data fields (numeric fields and identification annunciators~ and which table is stored in memory 35. In the preferred embodiment, the di~pl~y table is a display segment memory map stored in memory 35 t~ produce the desired display- image on display 30.
2~ When processor 16 controls display 30, the display table is periods:cally updated with information generated by processor If: the DS' line is pulled low thr~ugh option connector 38, processor ld no longer updates the display table. In such a.
s~,~uation, a special communications command is provided in prt~cessor 16 to allow the display identifiers and data to be written through option connector 38, preferably by a macl~ocomputer'connected to connector 38: Thus meter 1!0 has the flexibility to become a display peripheral to an option board:
In an especially preferred embodiment, pulse indicat~rs, potential ~.ndicators, the "EOI'° ~.ndicator, and the "Test'° indicator located in display 30 are controlled by fields in the display table, which fields can only be modified by information generated by processor 16. In such an embodiment, even if DS is low, processor 16 will still generate this certain field information. Information provided meter 10 through option connector 38 will be exclusive ORed with information generated by processor 16 to update the display table.
It will be appreciated from the above that an option board can be easily added to meter 10. As discussed above, the option board can then take control of most functions of meter 10, including modifying the basic metering function and reading processor 14 directly via processor 16. This aspect to the design allows a great deal of flexibility for future, yet undefined, functions.
In addition to the option board connector, space is preferably provided in chassis (not shown) of meter 10 for additional large components, such as carrier coupling components or a larger power supply transformer. The voltage connections in the meter base provide additional tabs for picking off the line voltage for parts of this nature.
Meter 10 also provides the ability to be placed in the test mode and exit from the test mode via a new optical port function. When in an optically initiated test mode, the meter will echo metering pulses as defined by the command on the optical port transmitter. The meter will listen for further communications commands. Additional commands can change the rate or measured quantity of the test output over the optical port. The meter will "ACK" any command sent while it is in the test mode and it will "ACK" the exit test mode command. While in an optically initiated test mode, commands other than those mentioned above are processed normally. Because there is the possibility of an echoed pulse confusing the programmer/readers receiver, a command to stop the pulse echo may be desired so communications can proceed uninterrupted. If left in test mode, the usual test mode time out of three demand intervals applies.

Meter Formulae Watt formulae -3 : Wa t ts=K~ ( KAV~I~+KeVelIel+K~V~zI~= ) -2 : Wa t ts=K~ ( (KaV~-KgVBo ) I~+ ( K~V~-KDV~ ) I~~ ) -8 : Watts=K~(KaV~I~- (KBV~IBo+KDV~=I~) +K~V~=I~~) -7 : Wa tts=K~ (KAY~IAo-KPV~ho+K~V~=I~=) NOTE: Subscripts refer to the phase of the inputs.
Sub-subscripts refer to the A/D cycle in which the sample is taken. Va for -7 applications is actually line to neutral.
VA Formulae -3 : VA=K~(KAV~r~I~rms+K9Velrmslelsms+Kcvc=rmalc=rms) -2 : VA=KG ( ( KAV~ -KBVHo ) rmsl~rms+ ( K~Y~i -KDV~ ) rmslc=rms) (KgV~rms+KdVc,zms) o +K Y
-8 : VA=KG (K,~V~rms~.torms+ 2 Ie rms C c rms c rms) -7 : YA'=K~(KAV~r~I~rms+KBYxormsleorms+KcYcirmslcirms) RMS measurements are made over one line cycle and preferably begin at the zero crossing of each voltage.
VAR Formula VAR= VAa -Wa t to + YAg~ -Wa t tg + VAS - Wa t t~
where the subscripts are associated with the I
terms of Watts and VAs and the calculation is performed every cycle as shown below:
-3 : VAR=K~(Ka (Y zmsl 2-Ao .loans ) ( ~zsro v~b I~o ) +

K (Ye~rms~9,rms) - (~,zezo YBiIei) 2+K (YCzzmsICirms) 2- (~,zazoe YCsIC=) 2) -2 : VAR=KG( ( (KaV~o-KBVeo) rmsl~,rms) 3- (~,z roc (K~1V,~-KBVBo) I,~) 2+
T Z - cl'cT~_ ( ( K~Y~=-KDVB=) rmslC=ras) (zero (Kwc= KDvBi ) Ici ) ) z -8: VAR=K~(K,1 (Y,bzmsLlozms)2-(~,z zoc Y~~oL~o) +

( 2 (KBY.torms+KDYCzrms) I9orms) 2- (~seroe (KeV~Ieo+KDVc=IB=) ) 2+
y - ~cyc a K ( Vc=~I~=~) ( z.ro Ycir~s ) ) -7 : VAR=Kc ( Ka ( Y rmsl z - cYci a 2 2 - cyc a ~b .lozms) (~zsro Y~aLlo) +K (YAozmsIBorms) (~sero Y.I.oIBo) 2+

A

IC ~ vC=rmslC=rms~ ~~z roe vC='~~i ~ 2 For purposes of the above formulae, the following definitions apply:
-2 means a 2 element in 3 wire delta application;
-3 means a 3 element in 4 wire wye application;
-8 means a 2 1/2 element in 4 wire wye application;

-5 means a 2 element in 3 wire delta application;
-7 is a 2 1/2 element in 4 wire delta application.
While the invention has been described and illustrated with reference to specific embodiments, those skilled in the art will recognize that modification and variations may be made without departing from the principles of the invention as described herein above and set forth in the following claims.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. Apparatus for electronically metering electrical energy, said electrical energy comprising voltage and current characteristics, wherein voltage and current signals representative of said voltage and current characteristics are provided, said apparatus comprising:
a first processor, connected to receive said voltage and current signals, for determining electrical energy from said voltage and current signals and for generating an energy signal representative of the electrical energy determination;

a second processor, connected to said first processor, for receiving said energy signal, for generating an indication signal representative of said energy signal;

an option connector, connected to said first processor and said second processor, whereby said energy signal is provided to said option connector and a communication connection is provided between said option connector and said second processor; and a power supply, connected to receive said voltage signal, for generating a power signal, said power signal being provided to said option connector, whereby a power connection is provided, said power supply comprising a semi-regulated power source, a regulated power source and a non-volatile power source and wherein an electrical ground is provided, said option connector further providing a semi-regulated power connection, a regulated power connection, a non-volatile power connection and an electrical ground connection.

2. The apparatus of claim 1, wherein said first processor comprises an analog to digital converter for converting said voltage and current signals to voltage and current digital signals.

3. The apparatus of claim 1, wherein a reference voltage is provided, wherein said power supply generates a precision reference voltage and wherein said first processor comprises a comparator, connected to receive said precision voltage and said reference voltage, for comparing said reference and precision voltages and for generating a comparator signal representative of such comparison.

4. The apparatus of claim 3, wherein said comparator signal is provided to said option connector.

5. The apparatus of claim 4, further comprising reset circuitry, connected to said regulated power source and said non-volatile source, for comparing said regulated power signal and said non-volatile power signal and for generating a reset signal representative of such comparison.

6. The apparatus of claim 5, wherein said reset signal is provided to said option connector.

7. The apparatus of claim 1, further comprising a display for displaying said indication signal and a state button located on said display, said state button being connected to said second processor, wherein said second processor generates and provides a status signal to said option connector representative of the condition of said state button.

8. The apparatus of claim 1, wherein said second processor generates an end of demand signal representative of the end of a demand interval for electrical energy and wherein said end of demand signal is provided to said option connector.

9. The apparatus of claim 1, wherein said second processor generates a KYZ
signal in relation to said energy signal, said KYZ signal being representative of the flow of electrical energy and wherein said KYZ signal is provided to said option connector.

10. The apparatus of claim 1, wherein said second processor is capable of generating and receiving serial data signals, wherein said serial data signals are provided to said option connector.

11. The apparatus of claim 1, further comprising a display, connected to receive said indication signal, for displaying electrical energy information.

12. The apparatus of claim 1, further comprising a power supply for supplying power to said first and second processors.

13. The apparatus of claim 1, further comprising a programmable read only memory connected to said first and second processors, for storing data used by said first and second processors and for storing information generated by said first and second processors.

14. The apparatus of claim 13, wherein said programmable read only memory is electrically erasable.

15. The apparatus of claim 1, further comprising a light converter for converting light to an electrical signal, said light converter connected to said second processor.

16. The apparatus of claim 15, wherein said second processor is capable of generating and receiving communication signals through said light converter, wherein any generated or received communication signals through said light converter are provided to said option connector.

17. The apparatus of claim 15, further comprising an electrical connection between said light converter and said option connector, wherein the provision of said electrical signal to said second processor can be controlled through said electrical connection.

18. The apparatus of claim 15, wherein said first processor comprises a first program, wherein said first processor determines electrical energy and generates said energy signal in response to said first program, wherein said first program can be modified in response to a program signal transmitted by said second processor and wherein said program signal can be provided to said second processor through said light converter, whereby the determination of electrical energy and the generation of said energy signal can be modified in response to signals transmitted through said light converter.

19. The apparatus of claim 1, further comprising a display connected to said second processor for displaying said indication signal and said option connector being connected to said second processor so that a display connection is provided to provide display information to said second processor for inclusion in said indication signal, whereby the content of said indication signal can be controlled through said display connection.

20. Apparatus for electronically metering electrical energy, said electrical energy comprising voltage and current characteristics, said apparatus comprising:
voltage sensing means for sensing the voltage characteristics of said electrical energy;
a current sensor comprising a plurality of current transformers for sensing the current characteristics of said electrical energy;
a first processor, connected to said voltage sensor and said current sensor, for determining electrical energy from said voltage and current signals and for generating an energy signal representative of the electrical energy determination;
a second processor, connected to said first processor, for receiving said energy signal and for generating an indication signal representative of said energy signal;
and an option connector, connected to said first processor and said second processor, whereby said energy signal is provided to said option connector and a communication connection is provided between said option connector and said second processor.

21. The apparatus of claim 20, further comprising a power supply, connected to said first and second processor, a display, connected to said second processor, and a printed circuit board, wherein said first and second processors, said power supply, said option connector and said display define an electronics assembly, wherein said electronics assembly is mounted on said printed circuit board.

22. The apparatus of claim 20, further comprising a resistor divider network, interposed between said voltage sensor and said first processor for dividing said voltage signal.

23. The apparatus of claim 22, wherein said voltage signal comprises A, B and C
phases, wherein said resistor divider network comprises a resistor divider for each of said A, B and C phases.

24. The apparatus of claim 23, wherein each resistor divider comprises two series connected one megohm 1/2 watt resistors connected in series with a 1 k ohm resistor.

25. Apparatus for electronically metering electrical energy, said electrical energy comprising voltage and current characteristics, wherein voltage and current signals representative of said voltage and current characteristics are provided, said apparatus comprising:
a first processor, connected to receive said voltage and current signals, for determining electrical energy from said voltage and current signals and for generating an energy signal representative of the electrical energy determination, said first processor comprising a memory for the storage of instructions, said first processor performing electrical energy determinations in response to the execution of said instructions;
modification means, connected to said first processor, for modifying the instructions executed by said first processor; and an option connector, connected to said modification means, whereby said execution signal is provided to said modification means through said option connector.

26. The apparatus of claim 25, said apparatus further comprising an optical port, connected to said modification means, whereby said execution signal is provided to said modification means through said optical port.

27. Apparatus for electronically metering electrical energy, said electrical energy comprising voltage and current characteristics, wherein voltage and current signals representative of said voltage and current characteristics are provided, said apparatus comprising:
a first processor, connected to receive said voltage and current signals, for determining electrical energy from said voltage and current signals and for generating an energy signal representative of the electrical energy determination;
a second processor, connected to said first processor, for receiving said energy signal, for generating an indication signal representative of said energy signal, said second processor also generating a KYZ signal in relation to said energy signal, said KYZ signal being representative of the flow of electrical energy; and an option connector, connected to said first processor and said second processor, whereby said energy signal and said KYZ signal are provided to said option connector and a communication connection is provided between said option connector and said second processor.

28. The apparatus of claim 27, wherein said first processor comprises an analog to digital converter for converting said voltage and current signals to voltage and current digital signals.

29. The apparatus of claim 28, further comprising a power supply, connected to receive said voltage signal, for generating a power signal, said power signal being provided to said option connector, whereby a power connection is provided.

30. The apparatus of claim 29, wherein said power supply comprises a semi-regulated power source, a regulated power source and a non-volatile power source and wherein an electrical ground is provided, said option connector further providing a semi-regulated power connection, a regulated power connection, a non-volatile power connection and an electrical ground connection.

31. The apparatus of claim 29, wherein a reference voltage is provided, wherein said power supply generates a precision reference voltage and wherein said first processor comprises a comparator, connected to receive said precision voltage and said reference voltage, for comparing said reference and precision voltages and for generating a comparator signal representative of such comparison.

32. The apparatus of claim 31, wherein said comparator signal is provided to said option connector.

33. The apparatus of claim 32, further comprising reset circuitry, connected to said regulated power source and said non-volatile source, for comparing said regulated power signal and said non-volatile power signal and for generating a reset signal representative of such comparison.

34. The apparatus of claim 33, wherein said reset signal is provided to said option connector.

35. The apparatus of claim 27, further comprising a display for displaying said indication signal and a state button located on said display, said state button being connected to said second processor, wherein said second processor generates and provides a status signal to said option connector representative of the condition of said state button.

36. The apparatus of claim 27, wherein said second processor generates an end of demand signal representative of the end of a demand interval for electrical energy and wherein said end of demand signal is provided to said option connector.

37. The apparatus of claim 27, wherein said second processor is capable of generating and receiving serial data signals, wherein said serial data signals are provided to said option connector.

38. The apparatus of claim 27, further comprising a display, connected to receive said indication signal, for displaying electrical energy information.

39. The apparatus of claim 27, further comprising a power supply for supplying power to said first and second processors.

40. The apparatus of claim 27, further comprising a programmable read only memory connected to said first and second processors, for storing data used by said first and second processors and for storing information generated by said first and second processors.

41. The apparatus of claim 40, wherein said programmable read only memory is electrically erasable.

42. The apparatus of claim 27, further comprising a light converter for converting light to an electrical signal, said light converter connected to said second processor.

43. The apparatus of claim 42 wherein said second processor is capable of generating and receiving communication signals through said light converter, wherein any generated or received communication signals through said light converter are provided to said option connector.

44. The apparatus of claim 42, further comprising an electrical connection between said light converter and said option connector, wherein the provision of said electrical signal to said second processor can be controlled through said electrical connection.

45. The apparatus of claim 42, wherein said first processor comprises a first program, wherein said first processor determines electrical energy and generates said energy signal in response to said first program, wherein said first program can be modified in response to a program signal transmitted by said second processor and wherein said program signal can be provided to said second processor through said light converter, whereby the determination of electrical energy and the generation of said energy signal can be modified in response to signals transmitted through said light converter.

46. The apparatus of claim 27, further comprising a display connected to said second processor for displaying said indication signal and said option connector being connected to said second processor so that a display connection is provided to provide display information to said second processor for inclusion in said indication signal, whereby the content of said indication signal can be controlled through said display connection.

47. Apparatus for electronically metering electrical energy, said electrical energy comprising voltage and current characteristics, wherein voltage and current signals representative of said voltage and current characteristics are provided, said apparatus comprising:
a first processor, connected to receive said voltage and current signals, for determining electrical energy from said voltage and current signals and for generating an energy signal representative of the electrical energy determination, said first processor comprising a memory for the storage of instructions, said first processor performing electrical energy determinations in response to the execution of said instructions;
modification means, connected to said first processor, for modifying the instructions executed by said first processor; and an optical port, connected to said modification means, whereby said execution signal is provided to said modification means through said optical port.

48. Apparatus for electronically metering electrical energy, said electrical energy comprising voltage and current characteristics, wherein voltage and current signals representative of said voltage and current characteristics are provided, said apparatus comprising:
a first processor, connected to receive said voltage and current signals, for determining electrical energy from said voltage and current signals and for generating an energy signal representative of the electrical energy determination;
a second processor, connected to said first processor, for receiving said energy signal, for generating an indication signal representative of said energy signal; and an option connector, connected to said first processor and said second processor, whereby said energy signal is provided to said option connector and a communication connection is provided between said option connector and said second processor.

49. The apparatus of claim 48, wherein said first processor comprises an analog to digital converter for converting said voltage and current signals to voltage and current digital signals.

50. The apparatus of claim 48, further comprising a power supply, connected to receive said voltage signal, for generating a power signal, said power signal being provided to said option connector, whereby a power connection is provided.

51. The apparatus of claim 50, wherein said power supply comprises a semi-regulated power source, a regulated power source and a non-volatile power source and wherein an electrical ground is provided, said option connector further providing a semi-regulated power connection, a regulated power connection, a non-volatile power connection and an electrical ground connection.

52. The apparatus of claim 50, wherein a reference voltage is provided, wherein said power supply generates a precision reference voltage and wherein said first processor comprises a comparator, connected to receive said precision voltage and said reference voltage, for comparing said reference and precision voltages and for generating a comparator signal representative of such comparison.

53. The apparatus of claim 52, wherein said comparator signal is provided to said option connector.

54. The apparatus of claim 53, further comprising reset circuitry, connected to said regulated power source and said non-volatile source, for comparing said regulated power signal and said non-volatile power signal and for generating a reset signal representative of such comparison.

55. The apparatus of claim 54, wherein said reset signal is provided to said option connector.

56. The apparatus of claim 48, further comprising a display for displaying said indication signal and a state button located on said display, said state button being connected to said second processor, wherein said second processor generates and provides a status signal to said option connector representative of the condition of said state button.

57. The apparatus of claim 48, wherein said second processor generates an end of demand signal representative of the end of a demand interval for electrical energy and wherein said end of demand signal is provided to said option connector.

58. The apparatus of claim 48, wherein said second processor generates a KYZ
signal in relation to said energy signal, said KYZ signal being representative of the flow of electrical energy and wherein said KYZ signal is provided to said option connector.

59. The apparatus of claim 48, wherein said second processor is capable of generating and receiving serial data signals, wherein said serial data signals are provided to said option connector.

60. The apparatus of claim 48, further comprising a display, connected to receive said indication signal, for displaying electrical energy information.

61. The apparatus of claim 48, further comprising a power supply for supplying power to said first and second processors.

62. The apparatus of claim 48, further comprising a programmable read only memory connected to said first and second processors, for storing data used by said first and second processors and for storing information generated by said first and second processors.

63. The apparatus of claim 62, wherein said programmable read only memory is electrically erasable.

64. The apparatus of claim 48, further comprising a light converter for converting light to an electrical signal, said light converter connected to said second processor.

65. The apparatus of claim 64, wherein said second processor is capable of generating and receiving communication signals through said light converter, wherein any generated or received communication signals through said light converter are provided to said option connector.

66. The apparatus of claim 64, further comprising an electrical connection between said light converter and said option connector, wherein the provision of said electrical signal to said second processor can be controlled through said electrical connection.

67. The apparatus of claim 64, wherein said first processor comprises a first program, wherein said first processor determines electrical energy and generates said energy signal in response to said first program, wherein said first program can be modified in response to a program signal transmitted by said second processor and wherein said program signal can be provided to said second processor through said light converter, whereby the determination of electrical energy and the generation of said energy signal can be modified in response to signals transmitted through said light converter.