CA1233519A - Electronic demand register - Google Patents
Electronic demand registerInfo
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- CA1233519A CA1233519A CA000484612A CA484612A CA1233519A CA 1233519 A CA1233519 A CA 1233519A CA 000484612 A CA000484612 A CA 000484612A CA 484612 A CA484612 A CA 484612A CA 1233519 A CA1233519 A CA 1233519A
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Abstract
ELECTRONIC DEMAND REGISTER
ABSTRACT OF THE DISCLOSURE
An electronic demand register includes a processor for calculating a demand in a demand subinterval. At the end of each demand subinterval, the calculated demand is summed with the demand in the preceding N-1 subintervals to derive an interval demand over N contiguous subintervals. The interval demand is compared to a previously recorded maximum demand and, if the interval demand exceeds the maximum demand, its value is substituted for the maximum demand for use in subsequent comparisons. The processor employs volatile memory. A non-volatile memory is provided for storing the billing data and programmed constants in the event of an impending power outage. A power monitor detects the possibility of an impending power outage and, operating on stored energy, both enables and powers the transfer of data to the non-volatile memory. When power is resumed, the power monitor enables resetting the processor and retransferring the data from the non-volatile to the volatile memory for resumption of demand metering. A
grace period is provided after the resumption of power before beginning demand metering to permit the energy user's starting loads to pass before demand metering begins. Provision is made for treating the beginning and ending of a test operating mode similar to a power outage. In addition, the demand register responds to its removal from, and its replacement in, the electric meter in a manner similar to its response to a power outage. In this manner, when the demand register is removed from the electric meter, the billing and other data is safely stored in the non-volatile memory from ABSTRACT OF THE DISCLOSURE
(Cont'd) which it can be copied to a replacement demand register. When the original or replacement demand register is replaced in the electric meter, the demand register treats the replacement in the same manner that it treats the resumption of power following a power outage.
ABSTRACT OF THE DISCLOSURE
An electronic demand register includes a processor for calculating a demand in a demand subinterval. At the end of each demand subinterval, the calculated demand is summed with the demand in the preceding N-1 subintervals to derive an interval demand over N contiguous subintervals. The interval demand is compared to a previously recorded maximum demand and, if the interval demand exceeds the maximum demand, its value is substituted for the maximum demand for use in subsequent comparisons. The processor employs volatile memory. A non-volatile memory is provided for storing the billing data and programmed constants in the event of an impending power outage. A power monitor detects the possibility of an impending power outage and, operating on stored energy, both enables and powers the transfer of data to the non-volatile memory. When power is resumed, the power monitor enables resetting the processor and retransferring the data from the non-volatile to the volatile memory for resumption of demand metering. A
grace period is provided after the resumption of power before beginning demand metering to permit the energy user's starting loads to pass before demand metering begins. Provision is made for treating the beginning and ending of a test operating mode similar to a power outage. In addition, the demand register responds to its removal from, and its replacement in, the electric meter in a manner similar to its response to a power outage. In this manner, when the demand register is removed from the electric meter, the billing and other data is safely stored in the non-volatile memory from ABSTRACT OF THE DISCLOSURE
(Cont'd) which it can be copied to a replacement demand register. When the original or replacement demand register is replaced in the electric meter, the demand register treats the replacement in the same manner that it treats the resumption of power following a power outage.
Description
~35~
llME 126 E:LECTRONIC DEMAND REGISTER
_ACKGROUND OF THE INVENTION
The present invention relates to electric meters and, more particularly to demand registers for electric meters.
Conventional electric meters employ an aluminum disk driven as a rotor o~ a small induction motor by an electric field at a speed which is proportional to the electric power being consumed by a load. Geared dials, or cyclometer discs, integrate the disk motion to indicate the total energy consumed, conventionally measured in kilowatt hours (one kilowatt hour equals one thousand watts of power consump-tion for one hour).
In addition to the above measurement of consumption, some eLectric meters contain demand registers haviny means for separating the consumption into those parts of consumption occurring during peak and off-peak hours (however defined) and for recording maximum demand during any one of a contiguous set of demand intervals over a predetermined period of time in order to adjust billing accordiny to such parameters. In one such meter disclosed in U.S.
Patent 3,586,97~ - D. M. Ham et al issued ~une 22, 1971, a mechanical demand reyister records -the maximum 3~
llME 126 ~ _ demand during a predetermined period of time and stores the value for reading~ The predetermined period of time may be, for example, the time between meter readings, or a period of time corresponding to the billing period of the u-tility providing the power. A clockwork mechanism restarts the demand register at ~he end o~ each demand interval which may be, for example, a Eraction oE an hour, so that, at the end of -the predetermined period, the stored value represents the highest value of power usage occurring during any one of the demand intervals in the predetermined period.
Demand registers o-E the mechanical type, such as disclosed in the above U.S. Patent, have limited flexibility. Once their design is completed for a particular meter physical configuration, the design is not transferrable to a meter having a different physical configuration. Also, the demand-measurement functions cannot be redefined without major mechanical redesign.
When a power outage occurs, the clockwork motor driving the demand register is halted.
Following the restoration of power, the clockwork motor driving the demand register is restarted without recognizing the fact tha-t a power outage has occurred~ ~here is some cluestion whether resumption of operation can be performed in this way while strictly abiding by the regulations for demand metering as definecl b~ the commissic)ns haviny jurisdiction over the utility provicling the electric power and without penalizing a custo~ler for ~n apparent very high demand which is the result oE the power outage and resumption and not the fault of the customer.
S:l~
llME 126 Maximum demand metering is conventionally clefined as the maximum amount of power consumed in any one contiguous demand interval during the time interval of interest; that is, the maximum amount of power ~onsumed in any one of the interval~ oE, for e~ample, 15 minutes, 30 minutes or one hour. If the accumulation of actual usage during one of such demand intervals i~ paused by a power outage and then res~llned, the demand accumulated at the end of the interrupted time period consist of an initial portion before the outage interruption and a final portion following the outage interruption. Not only does the intervention of the outage interruption appear to violate the definition of demand metering, but also, lS if the customer load includes a substantial number of motors or other devices having a large starting load compared to their running load, when power is restored, all or most of such motors and devices may be forced to go through their starting sec~uence at the ~0 same time. Under normal conditions, some of the customer's motors may run continuously and others may cycle on and off in an unsynchronized manner . Thus, the motor starting loads are normally distributed over time and their effect on demand metering is similarly distributed over time. As is well known, the starting load imposed by a motor is much higher than the running load. By synchronizing all or most of the customer's startiny load in a single time periocl followiny restoration of power, an unnaturally ~ h demand may be registered in -that time period when, in fact, the unnaturally high demand is the r~sult of the utility permitting a power outage to occur and not the result of the customer load producing the registered maximum demand.
3~
llME 126 In addition to the above limitations o~
mechanical demand metering, a useful demand metering technique known as rolling demand is not practically ~easible using mechanical demand registers. In rolling demand meteriny, a demand interval is divided into N contiyuous subintervals. The usage during each demand subinterval is summed with the demand recorde~
during the precediny N-l subintervals. At the end of each subinterval, the total demand recorded is the demancl for N subintervals, i.e. for the entire preceding demand interval. The maximum demand may then be -taken as the maximum over any interval sensed at the end o a subinterval. The use of such rolling demand metering avoids distortion in the billing data which could otherwise occur due to short-term extremes in the usage data which would otherwise become lost in the averaging process over an entire demand interval.
Greater Elexibility in demand metering may be obtainable using electronic acquisition, integration and processing of power usage. An electronic processor such as, ~or example, a microprocessor, may be employed to manage the acquisition, storage, processing and display o~ the usage and demand data. U.S. Patents ~,179,65~ -W. R. Germer issued December 18, 1979; 4,197,582 -P. M. Johnston et al issued April 8, 1980; 4,229,795 -G. Viewig et al issued October 21, 1980; ~,2833,772 -P~ M. Johns-ton issued August 11, 1981; ~,301,508 -J. A. Anderson issued November 17, 1981: ~,361,872 A. Spalti issued November 30, 1982; ~,368,519 -S. P. Kennedy issued ~anuary 11, 1983, among others, illustrate the Elex:ibility that electronic processing brings to the power and energy usage measurement.
Each of these electronic measurement devices includes means ~or producing an electronic signal having a characteristic such as, for example, a ~requency or a :~3~5:~
- 5 - llME 126 pulse repetition rate, which is rela-ted to the rate of power usage. The eleetronic processor is substituted for the mechanical demand regis-ter of the prior art to keep track of the demand during defined periods of time.
An electronic processor of an electronic demand recJister eonventionally employs volati.le random access memory for the h:igh speed and low power consump-tion characteristics offered by such devices.
When a power outaye occurs, iE steps are not taken to prevent it, all data in such volatile storaye may be lost. This could .include both prior demand data as well as a sense of where, in a time period, the outaye occurred. The loss of demand data has an obvious negative impact on billing. The loss of time sense would require that all users in the area affected by the power outage MUSt beyin a new time period for accumulation of demand. Such synehronization of demand meteriny is eonsidered undesirable by a.t least some utilities. Canadian Patent Applieation Serial No. 484,608, filed on June 20, 1985, Germer discloses means for storing data in non~volatile memory when a power outaye oecurs and for ignoring or tolerating certain normal devia-tions of the line power, such as, for example, momentary overvoltaye, surges, noise and momentary power outages enduring for a very short -time period, This new capability to store demand billincJ data and procJrammed constants ln non-volatile memo:ry permits re-thinkiny the manner in whieh demand data aecumulated before and after an outaye interruption may be handled so as to provide fairness both to the eonsumer and to the uti:Lity.
OBJECTS AND SUMMARY OF T~:[E INVENTION
Aeeordinyly, it is an object of the invention to provide an eleetronie demand reyister for an eleetrie meter whieh overeomes the drawbaeks of the 35~
llME 126 prior art.
~ t is a fur-ther object of -the invention to provide an electronic demand reyister of the type employing a digi-tal processor and a random access memory which includes means or storing volatile data in a non-volatile atorage medium during periods when the inteyrity of the data may otherwise be threatened and ~or retrieviny the data from the non-volatile storage medium and resuming normal operation following the threatening condition in a manner which re-tains relevant billing data accumulated before the threatening condition occurred.
Briefly stated, the present invention provides an electronic demand register having a processor or calculating a demand in a demand subinterval. At the end of each demand subinte~val, the calculated demand is summed with the demand in the preceding N-l subintervals to derive an interval demand over N contiguous subintervals. The interval demand is compared to a previously recorded maximum - demand, and if the interval demand exceeds the maximum demand, its value is substituted for the maximum demand for use in subsequent comparisons. The processor employs volatile memory. A non-volatile memory is provided for storing the billing data and programmed constants in the event oE an impending power outage. A power monitor detec-ts the possibility of an impending power outage and, operating on stored energy, both enable~ and powers the transfer oE data to the non-volatile memory. ~len power is resumed, the power monitor enabLes resetting the processor and retransferring the data from the non-volatile to the volatile memory for resumption of demand metering. A
grace period is provided after the resumption of power before beginning demand metering to permit the energy user's starting loads to pass before demand metering 33~
llME 126 -- 7 ~
begins. Provision i5 made for treating the beginning and ending of a -test operating mode similar to a power outac3e. ~n addi-tion, the demand register responds to its removal from, and it5 replacement in, the electric meter in a mannar similar to its response to a power outage. Ln this manner, when the demand register i9 rertloved from the electric meter, the billing and other data is saEely stored in the non-volatile memory, from which it can be copied, to a replacement demand :L0 register. When the original or replacement demand register is replaced in the electric meter, the demand register treats the replacement in the same manner that it treats the resumption of power ~ollowing a power outage.
According to an embodiment of the invention, there is provided a demand register for an electric meter comprising a processor, means in the processor for calculating a rolling demand including means Eor summing a demand in a subinterval with demands in a preceding N-l subintervals to derive an interval demand over N contiguous subintervals, means for storing a maximum demand, means for replacing the maximum demand with the interval demand if the interval demand exceeds the maximum demand, the processor including a volatile memory, a non-volatile memory, means responsive to a predetermined reduction in a voltage fed to the electric meter for enabling a fir~t transfer O~e at least the maximum demand and a plurality o~ programmed constants from the volatile memory to the non-volatile memory, means respon~ive to a predetermined restoration in a voltage fed to the electric meter for enabling a second transeer Oe the maximum demand and the plurality of constants erom the non-volatile memory to the volatile memory and means for resuming operation of the demand regis-ter ~ollowing the second transfer at a time in a first l'Z~35~
llME 12 subinterval corresponding to a time at which a prior subinterval was interrupted by the first transfer.
The above, and other objects, features and advantages of the present invention will become apparent rom the following description read in conjunction with the accompanying drawings, in which like reference nuTnerals designate the same elements.
BRIEF DESCRIP'rION OF TH~ DR~WINGS
E'ig. 1 i3 a schematic dia~ram of an electric meter to which the present invention may be applied.
Fig. 2 is a block diagram of a demand register of Fig. 1 according to an embodiment o~ the invention.
DETAILED D~SCRIPTION OF THE PREFERRED EMBODIMENT
The present invention is a demand metering system whose detailed functions are performed by a number of elements which represent separate inventions and for which Canadian Patent Applications have been filed. Since the detailed disclosures of the elements making up the system are fully detailed in their xespective patent applications, the present application omits the fuLl detail but provides reference to the individual applications for such detail. Instead of presenting the full detail, the present application summarizes the disclosures of each of the applications to the extent required for an understanding of the system beiny disclosed hereill.
Although the present invention may be adapted to any 9Ui table type of electric meter which employs an element rotating at a speed proportlonal to power consumption, including, for example, sing:Le phase or polyphase meter~ with one or more current and voltage coils, for concreteness, the detaile~
description which follows is directed towa.rd an illustrative example of a 2-wire single phase meter of the type having a single current coil and a sinyle ~Z~3~
llME 126 _ g _ voltage ~oil.
~ eEerring now to Fig. 1, there is shown, generally at 10, an electric meter which includes a small induction motor 12 driving a register 1~.
Induction motor 12 includes a stator 16 made up oE a voltacJe coil 18 and a current coil 20 disposed on opposite sides of a disk 22. Voltage coil 18 employs a core 2~ upon which is wound a large number oE turns of fine wire. Voltage coil 18 is connected across lines 26 and 28 which feed power to a load (not shown). Current coil 20 employs a core 30 upon w'hich a small number of turns, typically two or more, oE
heavy conductor are wound. Current coil 20 is connected in series with the power being fed to the load on line 26.
Disk 22 is affi~ed to a shaft 32 which is supported on suitable bearings (not shown) to permit concerted rotation of disk 22 and shaft 32 under the influence of a rotating magne-tic field produced by the combined in~luence of voltage coil 18 and current coil 20. A permanent magnet 34, having its poles disposed on opposite sides of disk 22, applies a retarding force which is proportional to the rotational speed o-f disk 22. The rotational torque produced by voltage coil 18 and current coil 20 combined with the retarding torque produced by permanent magnet 3~ is effective to rotate dis'k 22 at a speed which is proportional to the product of the voltage and the current: that is, the power, con~umed by the load.
Register 1~ includes a watthour register 36 which may include, for e~ample, a plurality of diaLs 38 w'hich are suitably geared and driven by a mechanical coupling ~0 in proportion to the rotation of shaEt 32. ~n the embodiment shown, mechanical coupling ~0 includes a worm ~2, which may be integrally formed in shaEt 32, engaging and rotating a -~Z~3351~3 llM~ 126 worm gear 44. Additional elements may be present in mechanical coupling 40 for coupling the rotation o~
worm gear 44 to watthour register 36 wi-th or without change in speed and direction according to the design of the particular electric meter lO. As is conventional, watthour register 36 totals the number of revolutions oE shaft 32, suitably sca:Led by the gear ratios employed, for billing purposes.
~ demand register ~6, shown schematically as a box in E'ig. l, i9 also connected by a suitable coupling means ~ to respond to -the rotation of shaft 32. In the prior art, demand register ~6 is conven-tionally a mechanical register having dials, or other indicating devices (not shown), and coupling means ~ is conventionally a mechanical arrangement including shafts and gearing driven by rotation of shaft 32. The dials, or indicating devices, in the mechanical embodiment of demand register 46 are urged forward for a fixed demand interval by a pusher mechanism (not shown). The pusher mechanism is reset and restarted at the end of each of the demand intervals, leaving the indicating devices with an indication proportional to the power usage (the demand) during the demand interval. The indication on the indicating devices at any time is, therefore, the maximum demand which has occurred during any one of the demand intervals since the last time the indicating devices were reset. The recorded maximum demand is employed in billing.
When a power outage occur~, the timiny motor driving the gearing oE mechanical demancd register ~6 is hal-ted at whatever stacJe in the demand interval and at whatever demand readings existed on demand register ~6 at the time the power outage occurred. At the end of the power outage, the timLng motor again begins driving the gear train and dials from the ~23~
~ llME 126 positions they had at the beginning of the power outage and demand metering is resumed from the same position within the demand interval as existed a-t -the beginning of the power outage. This practice may fail to rigorously satisfy the c1efinition oE demand metering and may also impose an unfair hurden on the user. This sys-tem does have -the one desirable feature, however that, since -the demand meteriny picks up a-t the same point in the demand interval that it had when the outage occurred, it proceeds to complete the demand interval and thus a power outage does not have the efEect of synchronizing all of the demand registers in the affected area.
In the present invention, demand register 46 is an electronic demand register.
Referring to Fig. 2, there is shown a simplified block diagram of a demand register 46 according to an emhodiment of the invention. For present purposes, it is sufficient to note that the - signal related to power usage fed from coupling means 48 to demand register 46 is an electronic signal having a characteristic such as, for example, a frequency or pulse repetition rate, which is variable in dependence on the rate of power usage. Any suitable electronic signal generating apparatus may be employed to produce a power usage signal which is applied on a line 50 to processor 52 in demand register 46.
Processor 52 appropriately perEorms calculations on the usage data, such as, for example, countiny pulses and scalincJ, to clerive desired demand parameters and stores the resul-t. In particular, processor 52 perEorms rolling demand metering as more ,?.
~Z33~
- 12 ~ llME 126 fully detailed in Canadian Patent Application Serial ~o. 48~,615~ filed June 20, 1985, Germer. srieEly described, rolling demand metering divides a demand interval into N equal demand subintervals. The demand is accumulated over the current subinterval ancl, at the end of the curren-t subinterval, the demand in the just-completed subinterval is summed w:ith the demands in the preced:iny N-:L demand subintervals to derive a curren-t demand interval value.
The current demand interval value is compared with a previously stored rnaximum demand and, if the current demand interval value exceeds the previous maximum demand, the previous maximum demand is replaced with the current demand interval value.
Rolling demand metering, as summarized above, and as fully detailed in the referenced Canadian Patent ~pplication, avoids losing revenue such as may occur by the use of a large demand interval which tends to average out actual peaks in demand, and also avoids distortion in demand data which may occur due to fortuitous straddling of a demand peak over an end of one demand interval and the beginning of the next demand interval.
In addi-tion to calculating and recording demand, processor 52 may provide an output on a line 5~ suitable for driving a display 56. The stored data may be transmitted on a line 58 to a remote location (not shown) for ~urther analysis and/or billing.
Due to the extremes oE env:i.ronment in which electric meters may be used, clisplay 56 may need special compensation for environmen-tal parameters.
Such special compensation may include a display temperature compensator 60 whose detailed structure and operation are fully disclosed in Canadian Patent Application Serial No. ~80,605, filed ~ay 2, 1985, ~233~
llME 126 6 ~P~ R . For the present application, it is suf~icient to note that a threshold voltaye exists ~or turnin~ liquid crystal display elements on and of~. 'rhis threshold voltage is non-linearly dependent on temperature. Display temperature compensator 60 is opera-tive -to con-trol a set of supply voltages fed to display 56 in a non-linear relationship to temperature in a manner which generally tracks the non~linear -temperature dependence o-~ the threshold voltage.
As previously noted, processor 52 conventionally employs vola-tile random access memory elements which lose any data stored in them in the event o~ a power outa~e~ rrhis i8 usually not acceptable in an electric meter where such loss of usage and/or demand data has a negative financial impact on the utility supplying the electric power.
Mon-volatile storage elements such as, for example, electrically erasable programmable read only memory elements, are well known for use with processor 52.
~Iowever, such non-volatile storage elements normally have relatively slow write and erase times on the order of 10 or 20 milliseconds. This is too slow ~or most applications. Besides this drawback, the power required -to erase and write such memory elements is quite high compared to that required by volatile memory elements of processor 52. Finally, a wear-out mechanism in electrically erasable programmable read only memory cells limits the number of times they can be erased and re-recorded. About lO,000 cycles of write and erase bring~ such a memory element to the end of its reliable useful life. '~'he volatile memory elements in processor 52 must, of course, be written and erased many thousands of times a day. 'rhus, an electrically erasable proyrammable read only m~mory would have a very short life as the operatin~ memory ~33.~g - 14 - llME 126 for processor 52.
In order to provide sa~e storage for data and/or programmed cons-tants during a power outaye or during -test operation, a eonventional non-volatile memory 6~ is provided into which such data and constants can be written and from which the data and constants ca:n ayain be read upon res-tora-tion of normal condi-tions. In their role in non-volatile memory 6~, eleetrically erasable programmable read o:nly memory elements are erased and rewri-tten only when a relatively serious power outage occurs and possibly during a relatively small number of test cycles. Such operations are not expeeted to occur on a frequenk enough basis in demand register 46 of eleetric meter 10 to represent a limit on the life of the register.
An incompatibility exists between the protocols required for transmitting and receiving data between some commereially available types of processor 52 and non-volatile memory 64. In order to adjust the protocols of the two devices, processor 52 formats an output message for transmission to non-volatile memory 64 in a manner which fools non-volatile memory 64 into recognizing a received word as one havlng the correct protocol. Similarly, processor 52 operates on a message reeeived from non-volatile memory 6~ using appropriate shift teehni.ques to align the data in -the reeeived message into a format whieh processor 52 can accept. A full disclosure o;~ the apparatus and Eune-tions involved in perform:ing the above memory interface is contained in Canadian Patent Applicat:ion Ser:ial No. ~81,268, Eiled May 10, 19~5, Simon.
A power supply ancl power monitor 66 receives AC power from lines 26 and 28 or the production of a regulated DC voltaye which is appliecl on a line 68 to all circuits in demand register 46 requiring such ~2~3~
- 15 - llME 126 power. In addition to producing regulated DC power, power supply and power monitor 66 also monitors the condition oE the AC power on lines 26 and 23 and, in response -to detected conditions indicating the possibility an impeding power outage or the actuali-ty of such a power outage, applies an emergency store signal on a line 70 to processor 52 which controls the transfer oE data rom processor 52 to non-volatile memory 6~ in the event of an apparent power outage and resets processor 52 in the even-t of an actual power outaye. Prior -to transferring the da-ta and programmed constants to non-volatile memory 64, processor 52 checks -to determine whether the demand during the current interval up to the time of the power outage exceeds the maximum demand previously recorded. If the demand in the current interval does exceed the maximum demand, the demand for the current interval is substituted for the maximum demand and the thus-modified data is transmitted to non-volatile memory 6~ for storage. Upon restoration of power, power supply and power monitor 66 applies a reset signal on line 70 to processor 52 for initiating the sequence for resuming demand metering, as will be explained. A full disclosure of the structure and function of power supply and power monitor 66 is contained in aforementioned Canadian Patent App:Lica-tion Serial No. ~3~,60~.
Resumption of demand metering Eollowing a power outage is clesirably perEormed to accomp:Lish the EollowincJ objec-tives:
1. A grace per:iod should be provided for permitting the energy user's motor starting loads, and other load peaks which are due totally or princ:Lpally by the power outage, to be comple-ted beEore demand meteriny is begun. This avoids penaliziny energy users , ~Z~3~
llME 126 for peak loads which are caused by the power outage and not by their intentional creation of peak demand.
llME 126 E:LECTRONIC DEMAND REGISTER
_ACKGROUND OF THE INVENTION
The present invention relates to electric meters and, more particularly to demand registers for electric meters.
Conventional electric meters employ an aluminum disk driven as a rotor o~ a small induction motor by an electric field at a speed which is proportional to the electric power being consumed by a load. Geared dials, or cyclometer discs, integrate the disk motion to indicate the total energy consumed, conventionally measured in kilowatt hours (one kilowatt hour equals one thousand watts of power consump-tion for one hour).
In addition to the above measurement of consumption, some eLectric meters contain demand registers haviny means for separating the consumption into those parts of consumption occurring during peak and off-peak hours (however defined) and for recording maximum demand during any one of a contiguous set of demand intervals over a predetermined period of time in order to adjust billing accordiny to such parameters. In one such meter disclosed in U.S.
Patent 3,586,97~ - D. M. Ham et al issued ~une 22, 1971, a mechanical demand reyister records -the maximum 3~
llME 126 ~ _ demand during a predetermined period of time and stores the value for reading~ The predetermined period of time may be, for example, the time between meter readings, or a period of time corresponding to the billing period of the u-tility providing the power. A clockwork mechanism restarts the demand register at ~he end o~ each demand interval which may be, for example, a Eraction oE an hour, so that, at the end of -the predetermined period, the stored value represents the highest value of power usage occurring during any one of the demand intervals in the predetermined period.
Demand registers o-E the mechanical type, such as disclosed in the above U.S. Patent, have limited flexibility. Once their design is completed for a particular meter physical configuration, the design is not transferrable to a meter having a different physical configuration. Also, the demand-measurement functions cannot be redefined without major mechanical redesign.
When a power outage occurs, the clockwork motor driving the demand register is halted.
Following the restoration of power, the clockwork motor driving the demand register is restarted without recognizing the fact tha-t a power outage has occurred~ ~here is some cluestion whether resumption of operation can be performed in this way while strictly abiding by the regulations for demand metering as definecl b~ the commissic)ns haviny jurisdiction over the utility provicling the electric power and without penalizing a custo~ler for ~n apparent very high demand which is the result oE the power outage and resumption and not the fault of the customer.
S:l~
llME 126 Maximum demand metering is conventionally clefined as the maximum amount of power consumed in any one contiguous demand interval during the time interval of interest; that is, the maximum amount of power ~onsumed in any one of the interval~ oE, for e~ample, 15 minutes, 30 minutes or one hour. If the accumulation of actual usage during one of such demand intervals i~ paused by a power outage and then res~llned, the demand accumulated at the end of the interrupted time period consist of an initial portion before the outage interruption and a final portion following the outage interruption. Not only does the intervention of the outage interruption appear to violate the definition of demand metering, but also, lS if the customer load includes a substantial number of motors or other devices having a large starting load compared to their running load, when power is restored, all or most of such motors and devices may be forced to go through their starting sec~uence at the ~0 same time. Under normal conditions, some of the customer's motors may run continuously and others may cycle on and off in an unsynchronized manner . Thus, the motor starting loads are normally distributed over time and their effect on demand metering is similarly distributed over time. As is well known, the starting load imposed by a motor is much higher than the running load. By synchronizing all or most of the customer's startiny load in a single time periocl followiny restoration of power, an unnaturally ~ h demand may be registered in -that time period when, in fact, the unnaturally high demand is the r~sult of the utility permitting a power outage to occur and not the result of the customer load producing the registered maximum demand.
3~
llME 126 In addition to the above limitations o~
mechanical demand metering, a useful demand metering technique known as rolling demand is not practically ~easible using mechanical demand registers. In rolling demand meteriny, a demand interval is divided into N contiyuous subintervals. The usage during each demand subinterval is summed with the demand recorde~
during the precediny N-l subintervals. At the end of each subinterval, the total demand recorded is the demancl for N subintervals, i.e. for the entire preceding demand interval. The maximum demand may then be -taken as the maximum over any interval sensed at the end o a subinterval. The use of such rolling demand metering avoids distortion in the billing data which could otherwise occur due to short-term extremes in the usage data which would otherwise become lost in the averaging process over an entire demand interval.
Greater Elexibility in demand metering may be obtainable using electronic acquisition, integration and processing of power usage. An electronic processor such as, ~or example, a microprocessor, may be employed to manage the acquisition, storage, processing and display o~ the usage and demand data. U.S. Patents ~,179,65~ -W. R. Germer issued December 18, 1979; 4,197,582 -P. M. Johnston et al issued April 8, 1980; 4,229,795 -G. Viewig et al issued October 21, 1980; ~,2833,772 -P~ M. Johns-ton issued August 11, 1981; ~,301,508 -J. A. Anderson issued November 17, 1981: ~,361,872 A. Spalti issued November 30, 1982; ~,368,519 -S. P. Kennedy issued ~anuary 11, 1983, among others, illustrate the Elex:ibility that electronic processing brings to the power and energy usage measurement.
Each of these electronic measurement devices includes means ~or producing an electronic signal having a characteristic such as, for example, a ~requency or a :~3~5:~
- 5 - llME 126 pulse repetition rate, which is rela-ted to the rate of power usage. The eleetronic processor is substituted for the mechanical demand regis-ter of the prior art to keep track of the demand during defined periods of time.
An electronic processor of an electronic demand recJister eonventionally employs volati.le random access memory for the h:igh speed and low power consump-tion characteristics offered by such devices.
When a power outaye occurs, iE steps are not taken to prevent it, all data in such volatile storaye may be lost. This could .include both prior demand data as well as a sense of where, in a time period, the outaye occurred. The loss of demand data has an obvious negative impact on billing. The loss of time sense would require that all users in the area affected by the power outage MUSt beyin a new time period for accumulation of demand. Such synehronization of demand meteriny is eonsidered undesirable by a.t least some utilities. Canadian Patent Applieation Serial No. 484,608, filed on June 20, 1985, Germer discloses means for storing data in non~volatile memory when a power outaye oecurs and for ignoring or tolerating certain normal devia-tions of the line power, such as, for example, momentary overvoltaye, surges, noise and momentary power outages enduring for a very short -time period, This new capability to store demand billincJ data and procJrammed constants ln non-volatile memo:ry permits re-thinkiny the manner in whieh demand data aecumulated before and after an outaye interruption may be handled so as to provide fairness both to the eonsumer and to the uti:Lity.
OBJECTS AND SUMMARY OF T~:[E INVENTION
Aeeordinyly, it is an object of the invention to provide an eleetronie demand reyister for an eleetrie meter whieh overeomes the drawbaeks of the 35~
llME 126 prior art.
~ t is a fur-ther object of -the invention to provide an electronic demand reyister of the type employing a digi-tal processor and a random access memory which includes means or storing volatile data in a non-volatile atorage medium during periods when the inteyrity of the data may otherwise be threatened and ~or retrieviny the data from the non-volatile storage medium and resuming normal operation following the threatening condition in a manner which re-tains relevant billing data accumulated before the threatening condition occurred.
Briefly stated, the present invention provides an electronic demand register having a processor or calculating a demand in a demand subinterval. At the end of each demand subinte~val, the calculated demand is summed with the demand in the preceding N-l subintervals to derive an interval demand over N contiguous subintervals. The interval demand is compared to a previously recorded maximum - demand, and if the interval demand exceeds the maximum demand, its value is substituted for the maximum demand for use in subsequent comparisons. The processor employs volatile memory. A non-volatile memory is provided for storing the billing data and programmed constants in the event oE an impending power outage. A power monitor detec-ts the possibility of an impending power outage and, operating on stored energy, both enable~ and powers the transfer oE data to the non-volatile memory. ~len power is resumed, the power monitor enabLes resetting the processor and retransferring the data from the non-volatile to the volatile memory for resumption of demand metering. A
grace period is provided after the resumption of power before beginning demand metering to permit the energy user's starting loads to pass before demand metering 33~
llME 126 -- 7 ~
begins. Provision i5 made for treating the beginning and ending of a -test operating mode similar to a power outac3e. ~n addi-tion, the demand register responds to its removal from, and it5 replacement in, the electric meter in a mannar similar to its response to a power outage. Ln this manner, when the demand register i9 rertloved from the electric meter, the billing and other data is saEely stored in the non-volatile memory, from which it can be copied, to a replacement demand :L0 register. When the original or replacement demand register is replaced in the electric meter, the demand register treats the replacement in the same manner that it treats the resumption of power ~ollowing a power outage.
According to an embodiment of the invention, there is provided a demand register for an electric meter comprising a processor, means in the processor for calculating a rolling demand including means Eor summing a demand in a subinterval with demands in a preceding N-l subintervals to derive an interval demand over N contiguous subintervals, means for storing a maximum demand, means for replacing the maximum demand with the interval demand if the interval demand exceeds the maximum demand, the processor including a volatile memory, a non-volatile memory, means responsive to a predetermined reduction in a voltage fed to the electric meter for enabling a fir~t transfer O~e at least the maximum demand and a plurality o~ programmed constants from the volatile memory to the non-volatile memory, means respon~ive to a predetermined restoration in a voltage fed to the electric meter for enabling a second transeer Oe the maximum demand and the plurality of constants erom the non-volatile memory to the volatile memory and means for resuming operation of the demand regis-ter ~ollowing the second transfer at a time in a first l'Z~35~
llME 12 subinterval corresponding to a time at which a prior subinterval was interrupted by the first transfer.
The above, and other objects, features and advantages of the present invention will become apparent rom the following description read in conjunction with the accompanying drawings, in which like reference nuTnerals designate the same elements.
BRIEF DESCRIP'rION OF TH~ DR~WINGS
E'ig. 1 i3 a schematic dia~ram of an electric meter to which the present invention may be applied.
Fig. 2 is a block diagram of a demand register of Fig. 1 according to an embodiment o~ the invention.
DETAILED D~SCRIPTION OF THE PREFERRED EMBODIMENT
The present invention is a demand metering system whose detailed functions are performed by a number of elements which represent separate inventions and for which Canadian Patent Applications have been filed. Since the detailed disclosures of the elements making up the system are fully detailed in their xespective patent applications, the present application omits the fuLl detail but provides reference to the individual applications for such detail. Instead of presenting the full detail, the present application summarizes the disclosures of each of the applications to the extent required for an understanding of the system beiny disclosed hereill.
Although the present invention may be adapted to any 9Ui table type of electric meter which employs an element rotating at a speed proportlonal to power consumption, including, for example, sing:Le phase or polyphase meter~ with one or more current and voltage coils, for concreteness, the detaile~
description which follows is directed towa.rd an illustrative example of a 2-wire single phase meter of the type having a single current coil and a sinyle ~Z~3~
llME 126 _ g _ voltage ~oil.
~ eEerring now to Fig. 1, there is shown, generally at 10, an electric meter which includes a small induction motor 12 driving a register 1~.
Induction motor 12 includes a stator 16 made up oE a voltacJe coil 18 and a current coil 20 disposed on opposite sides of a disk 22. Voltage coil 18 employs a core 2~ upon which is wound a large number oE turns of fine wire. Voltage coil 18 is connected across lines 26 and 28 which feed power to a load (not shown). Current coil 20 employs a core 30 upon w'hich a small number of turns, typically two or more, oE
heavy conductor are wound. Current coil 20 is connected in series with the power being fed to the load on line 26.
Disk 22 is affi~ed to a shaft 32 which is supported on suitable bearings (not shown) to permit concerted rotation of disk 22 and shaft 32 under the influence of a rotating magne-tic field produced by the combined in~luence of voltage coil 18 and current coil 20. A permanent magnet 34, having its poles disposed on opposite sides of disk 22, applies a retarding force which is proportional to the rotational speed o-f disk 22. The rotational torque produced by voltage coil 18 and current coil 20 combined with the retarding torque produced by permanent magnet 3~ is effective to rotate dis'k 22 at a speed which is proportional to the product of the voltage and the current: that is, the power, con~umed by the load.
Register 1~ includes a watthour register 36 which may include, for e~ample, a plurality of diaLs 38 w'hich are suitably geared and driven by a mechanical coupling ~0 in proportion to the rotation of shaEt 32. ~n the embodiment shown, mechanical coupling ~0 includes a worm ~2, which may be integrally formed in shaEt 32, engaging and rotating a -~Z~3351~3 llM~ 126 worm gear 44. Additional elements may be present in mechanical coupling 40 for coupling the rotation o~
worm gear 44 to watthour register 36 wi-th or without change in speed and direction according to the design of the particular electric meter lO. As is conventional, watthour register 36 totals the number of revolutions oE shaft 32, suitably sca:Led by the gear ratios employed, for billing purposes.
~ demand register ~6, shown schematically as a box in E'ig. l, i9 also connected by a suitable coupling means ~ to respond to -the rotation of shaft 32. In the prior art, demand register ~6 is conven-tionally a mechanical register having dials, or other indicating devices (not shown), and coupling means ~ is conventionally a mechanical arrangement including shafts and gearing driven by rotation of shaft 32. The dials, or indicating devices, in the mechanical embodiment of demand register 46 are urged forward for a fixed demand interval by a pusher mechanism (not shown). The pusher mechanism is reset and restarted at the end of each of the demand intervals, leaving the indicating devices with an indication proportional to the power usage (the demand) during the demand interval. The indication on the indicating devices at any time is, therefore, the maximum demand which has occurred during any one of the demand intervals since the last time the indicating devices were reset. The recorded maximum demand is employed in billing.
When a power outage occur~, the timiny motor driving the gearing oE mechanical demancd register ~6 is hal-ted at whatever stacJe in the demand interval and at whatever demand readings existed on demand register ~6 at the time the power outage occurred. At the end of the power outage, the timLng motor again begins driving the gear train and dials from the ~23~
~ llME 126 positions they had at the beginning of the power outage and demand metering is resumed from the same position within the demand interval as existed a-t -the beginning of the power outage. This practice may fail to rigorously satisfy the c1efinition oE demand metering and may also impose an unfair hurden on the user. This sys-tem does have -the one desirable feature, however that, since -the demand meteriny picks up a-t the same point in the demand interval that it had when the outage occurred, it proceeds to complete the demand interval and thus a power outage does not have the efEect of synchronizing all of the demand registers in the affected area.
In the present invention, demand register 46 is an electronic demand register.
Referring to Fig. 2, there is shown a simplified block diagram of a demand register 46 according to an emhodiment of the invention. For present purposes, it is sufficient to note that the - signal related to power usage fed from coupling means 48 to demand register 46 is an electronic signal having a characteristic such as, for example, a frequency or pulse repetition rate, which is variable in dependence on the rate of power usage. Any suitable electronic signal generating apparatus may be employed to produce a power usage signal which is applied on a line 50 to processor 52 in demand register 46.
Processor 52 appropriately perEorms calculations on the usage data, such as, for example, countiny pulses and scalincJ, to clerive desired demand parameters and stores the resul-t. In particular, processor 52 perEorms rolling demand metering as more ,?.
~Z33~
- 12 ~ llME 126 fully detailed in Canadian Patent Application Serial ~o. 48~,615~ filed June 20, 1985, Germer. srieEly described, rolling demand metering divides a demand interval into N equal demand subintervals. The demand is accumulated over the current subinterval ancl, at the end of the curren-t subinterval, the demand in the just-completed subinterval is summed w:ith the demands in the preced:iny N-:L demand subintervals to derive a curren-t demand interval value.
The current demand interval value is compared with a previously stored rnaximum demand and, if the current demand interval value exceeds the previous maximum demand, the previous maximum demand is replaced with the current demand interval value.
Rolling demand metering, as summarized above, and as fully detailed in the referenced Canadian Patent ~pplication, avoids losing revenue such as may occur by the use of a large demand interval which tends to average out actual peaks in demand, and also avoids distortion in demand data which may occur due to fortuitous straddling of a demand peak over an end of one demand interval and the beginning of the next demand interval.
In addi-tion to calculating and recording demand, processor 52 may provide an output on a line 5~ suitable for driving a display 56. The stored data may be transmitted on a line 58 to a remote location (not shown) for ~urther analysis and/or billing.
Due to the extremes oE env:i.ronment in which electric meters may be used, clisplay 56 may need special compensation for environmen-tal parameters.
Such special compensation may include a display temperature compensator 60 whose detailed structure and operation are fully disclosed in Canadian Patent Application Serial No. ~80,605, filed ~ay 2, 1985, ~233~
llME 126 6 ~P~ R . For the present application, it is suf~icient to note that a threshold voltaye exists ~or turnin~ liquid crystal display elements on and of~. 'rhis threshold voltage is non-linearly dependent on temperature. Display temperature compensator 60 is opera-tive -to con-trol a set of supply voltages fed to display 56 in a non-linear relationship to temperature in a manner which generally tracks the non~linear -temperature dependence o-~ the threshold voltage.
As previously noted, processor 52 conventionally employs vola-tile random access memory elements which lose any data stored in them in the event o~ a power outa~e~ rrhis i8 usually not acceptable in an electric meter where such loss of usage and/or demand data has a negative financial impact on the utility supplying the electric power.
Mon-volatile storage elements such as, for example, electrically erasable programmable read only memory elements, are well known for use with processor 52.
~Iowever, such non-volatile storage elements normally have relatively slow write and erase times on the order of 10 or 20 milliseconds. This is too slow ~or most applications. Besides this drawback, the power required -to erase and write such memory elements is quite high compared to that required by volatile memory elements of processor 52. Finally, a wear-out mechanism in electrically erasable programmable read only memory cells limits the number of times they can be erased and re-recorded. About lO,000 cycles of write and erase bring~ such a memory element to the end of its reliable useful life. '~'he volatile memory elements in processor 52 must, of course, be written and erased many thousands of times a day. 'rhus, an electrically erasable proyrammable read only m~mory would have a very short life as the operatin~ memory ~33.~g - 14 - llME 126 for processor 52.
In order to provide sa~e storage for data and/or programmed cons-tants during a power outaye or during -test operation, a eonventional non-volatile memory 6~ is provided into which such data and constants can be written and from which the data and constants ca:n ayain be read upon res-tora-tion of normal condi-tions. In their role in non-volatile memory 6~, eleetrically erasable programmable read o:nly memory elements are erased and rewri-tten only when a relatively serious power outage occurs and possibly during a relatively small number of test cycles. Such operations are not expeeted to occur on a frequenk enough basis in demand register 46 of eleetric meter 10 to represent a limit on the life of the register.
An incompatibility exists between the protocols required for transmitting and receiving data between some commereially available types of processor 52 and non-volatile memory 64. In order to adjust the protocols of the two devices, processor 52 formats an output message for transmission to non-volatile memory 64 in a manner which fools non-volatile memory 64 into recognizing a received word as one havlng the correct protocol. Similarly, processor 52 operates on a message reeeived from non-volatile memory 6~ using appropriate shift teehni.ques to align the data in -the reeeived message into a format whieh processor 52 can accept. A full disclosure o;~ the apparatus and Eune-tions involved in perform:ing the above memory interface is contained in Canadian Patent Applicat:ion Ser:ial No. ~81,268, Eiled May 10, 19~5, Simon.
A power supply ancl power monitor 66 receives AC power from lines 26 and 28 or the production of a regulated DC voltaye which is appliecl on a line 68 to all circuits in demand register 46 requiring such ~2~3~
- 15 - llME 126 power. In addition to producing regulated DC power, power supply and power monitor 66 also monitors the condition oE the AC power on lines 26 and 23 and, in response -to detected conditions indicating the possibility an impeding power outage or the actuali-ty of such a power outage, applies an emergency store signal on a line 70 to processor 52 which controls the transfer oE data rom processor 52 to non-volatile memory 6~ in the event of an apparent power outage and resets processor 52 in the even-t of an actual power outaye. Prior -to transferring the da-ta and programmed constants to non-volatile memory 64, processor 52 checks -to determine whether the demand during the current interval up to the time of the power outage exceeds the maximum demand previously recorded. If the demand in the current interval does exceed the maximum demand, the demand for the current interval is substituted for the maximum demand and the thus-modified data is transmitted to non-volatile memory 6~ for storage. Upon restoration of power, power supply and power monitor 66 applies a reset signal on line 70 to processor 52 for initiating the sequence for resuming demand metering, as will be explained. A full disclosure of the structure and function of power supply and power monitor 66 is contained in aforementioned Canadian Patent App:Lica-tion Serial No. ~3~,60~.
Resumption of demand metering Eollowing a power outage is clesirably perEormed to accomp:Lish the EollowincJ objec-tives:
1. A grace per:iod should be provided for permitting the energy user's motor starting loads, and other load peaks which are due totally or princ:Lpally by the power outage, to be comple-ted beEore demand meteriny is begun. This avoids penaliziny energy users , ~Z~3~
llME 126 for peak loads which are caused by the power outage and not by their intentional creation of peak demand.
2. A new partial demand subinterval should be begun Eollowing the grace period at point in a partial demand subinterval correspondiny to the point where the prior subinterval was interrupted by the power outage. This avoids synchroniziny demand intervals and subinterval~ throughout the area aEEected by the power outage.
3. A new demand interval should be begun æimultaneously with the new demand subinterval with demands in the prior N-l subintervals set to ~ero.
4. The previously stored value of maximum demand should be re-stored for comparison with the on~going interval demands.
~he preceding objectives are achieved in processor 52 in cooperation with power supply and power monitor 66 and non-volatile memory 64 in the ' ~3 manner fully disclosed in Canadian Patent Application ji ~ NoO ~ filed J~e~d,l1 ~
It is desirable to provide means ~or testing ~5 demancl register 46 in the shop or in the field without compromising stored billing data and programmed constants. A manual input 62 is provided for suitably changing the Eunctional operation of demand register ~6 by applying an appropriate signal to proce~sor 52. When test operation is begun, processor 52 responds to it as though a power outage were occurring. That isl processor 52 checks to determine whether the presen-t interval demand exceeds the maximum demand and, if it does, stores the present interval demand as the new maximum demand, and then transfers subinterval timiny, maximum demand and ~233S~9 llME 126 progra~Jned constants to non-vola-tile memory 6~. This permits test opera-tion of processor 52 under control of, ~or example, switches in manual input 62 to manipulate the data in processor 52 and to provide ~or display of data on display 56 which is not displayed duriny normal u~e of demand reyister 46. At the end of test operation, normal operation is resumed in a manner identical to the manner o~ resumption of operation EoLlowiny a power outage. That i~, demand accumulation i~ begun during a partial subinterval, a new demand interval is begun with demand in the prior N-1 subintervals set to zero and the previous maximum demand and the programmed constants are retrieved ~rom non-volatile memory 6~ and re-stored in processor 52 for use as previously described. Test operation o~
demand register 46 is ~ully disclosed in Canadian ~ ~ Patent Application Serial No. ~4~d~ ~iled JU~4JIq~
- In order to adapt demand register 46 of the present invention to as wide a range o~ electric meters as possible, a single electronic design is employed. The programmed constants which are employed in processor 52 customize processor 52 ~or the particular style of electric meter 10 in which it is installed and for the particular customer installation. The programmed constants are stored in non-volatile memory 6~ using a conventional, or especially adapted, EEPROM programmer beore demand register ~6 is installed in electric meter 10. When demand register ~6 is installed and connected to a power line, a power-up sequence identical to that perEormed a~ter a power outage, and previously described herein, is per~ormed. That is, the programmed constants are read into processor 52 and demand metering is begun in the manner described.
llME 126 In the case o~ equipment ~ailure in the field, one convenient troubleshooting method employs the substitution of a replaceable module for a module which may ~e defective~ Such a troubleshooting method is foreseen for use with the system of the present invention. Such a troubleshooting method raises the problem o~ defininy a practical way of copying the unique set o~ programmed constants and billing data from a non-volati:le memory 64 in a demand register ~6 being replaced into a non-volatile memory 64 of a replacement demand register 46. This copying function is performed in a programmer (not shown) which reads out the data from a non-volatile memory 64 when its demand register 46 has been removed from the circuit, temporarily stores this data, and then copies the temporarily stored data into non-volatile memory 64 in the replacement unit. This copying function is enabled by the manner in which demand register 46 responds to the apparent loss of power and its resumption. That is, when demand register 46 is removed from electric meter lO, power supply and power monitor 66 senses this as a power outage and stores the described data in non-volatile memory 64 which it can be read using the programmer~ When power is restored to the replacement demand register 46, power supply and power monitor 66, processor 52 and non-volatile memory 64 respond as though to a normal resumption of power following a power outage. That is, bi:llinc~ data and programmed constants are trans~erred from non-volatile memory 6~ to processor 52 and the described po~t-power-outage sequence is followecl. Since the particular programmer used to read, temporarily store and to copy the data from a non-volatile memory 64 being replace to -the replacement element may be conventional, a full ~3~
- 19 - llME 126 description and illustration thereof is omitted from -the presen-t disclosure. A full disclosure of the apparatus and method for the copying function is provided in Canadian Patent Application Serial No. 484,614, filecl June 20, 1985, Germer.
I-laving described pre-ferred embodlments of the :invention wi-th reference -to the accompanying drawinys, it i5 to be understood that the invention is not limited to those precise embodimen-ts, and that various changes and modifica-tions may be effected therein by one skilled in the art without departing from the scope or spirit o the invention as defined in the appended claims.
~he preceding objectives are achieved in processor 52 in cooperation with power supply and power monitor 66 and non-volatile memory 64 in the ' ~3 manner fully disclosed in Canadian Patent Application ji ~ NoO ~ filed J~e~d,l1 ~
It is desirable to provide means ~or testing ~5 demancl register 46 in the shop or in the field without compromising stored billing data and programmed constants. A manual input 62 is provided for suitably changing the Eunctional operation of demand register ~6 by applying an appropriate signal to proce~sor 52. When test operation is begun, processor 52 responds to it as though a power outage were occurring. That isl processor 52 checks to determine whether the presen-t interval demand exceeds the maximum demand and, if it does, stores the present interval demand as the new maximum demand, and then transfers subinterval timiny, maximum demand and ~233S~9 llME 126 progra~Jned constants to non-vola-tile memory 6~. This permits test opera-tion of processor 52 under control of, ~or example, switches in manual input 62 to manipulate the data in processor 52 and to provide ~or display of data on display 56 which is not displayed duriny normal u~e of demand reyister 46. At the end of test operation, normal operation is resumed in a manner identical to the manner o~ resumption of operation EoLlowiny a power outage. That i~, demand accumulation i~ begun during a partial subinterval, a new demand interval is begun with demand in the prior N-1 subintervals set to zero and the previous maximum demand and the programmed constants are retrieved ~rom non-volatile memory 6~ and re-stored in processor 52 for use as previously described. Test operation o~
demand register 46 is ~ully disclosed in Canadian ~ ~ Patent Application Serial No. ~4~d~ ~iled JU~4JIq~
- In order to adapt demand register 46 of the present invention to as wide a range o~ electric meters as possible, a single electronic design is employed. The programmed constants which are employed in processor 52 customize processor 52 ~or the particular style of electric meter 10 in which it is installed and for the particular customer installation. The programmed constants are stored in non-volatile memory 6~ using a conventional, or especially adapted, EEPROM programmer beore demand register ~6 is installed in electric meter 10. When demand register ~6 is installed and connected to a power line, a power-up sequence identical to that perEormed a~ter a power outage, and previously described herein, is per~ormed. That is, the programmed constants are read into processor 52 and demand metering is begun in the manner described.
llME 126 In the case o~ equipment ~ailure in the field, one convenient troubleshooting method employs the substitution of a replaceable module for a module which may ~e defective~ Such a troubleshooting method is foreseen for use with the system of the present invention. Such a troubleshooting method raises the problem o~ defininy a practical way of copying the unique set o~ programmed constants and billing data from a non-volati:le memory 64 in a demand register ~6 being replaced into a non-volatile memory 64 of a replacement demand register 46. This copying function is performed in a programmer (not shown) which reads out the data from a non-volatile memory 64 when its demand register 46 has been removed from the circuit, temporarily stores this data, and then copies the temporarily stored data into non-volatile memory 64 in the replacement unit. This copying function is enabled by the manner in which demand register 46 responds to the apparent loss of power and its resumption. That is, when demand register 46 is removed from electric meter lO, power supply and power monitor 66 senses this as a power outage and stores the described data in non-volatile memory 64 which it can be read using the programmer~ When power is restored to the replacement demand register 46, power supply and power monitor 66, processor 52 and non-volatile memory 64 respond as though to a normal resumption of power following a power outage. That is, bi:llinc~ data and programmed constants are trans~erred from non-volatile memory 6~ to processor 52 and the described po~t-power-outage sequence is followecl. Since the particular programmer used to read, temporarily store and to copy the data from a non-volatile memory 64 being replace to -the replacement element may be conventional, a full ~3~
- 19 - llME 126 description and illustration thereof is omitted from -the presen-t disclosure. A full disclosure of the apparatus and method for the copying function is provided in Canadian Patent Application Serial No. 484,614, filecl June 20, 1985, Germer.
I-laving described pre-ferred embodlments of the :invention wi-th reference -to the accompanying drawinys, it i5 to be understood that the invention is not limited to those precise embodimen-ts, and that various changes and modifica-tions may be effected therein by one skilled in the art without departing from the scope or spirit o the invention as defined in the appended claims.
Claims (7)
1. A demand register for an electric meter comprising;
a processor;
means in said processor for calculating a rolling demand including means for summing a demand in a subinterval with demands in a preceding N-1 subintervals to derive an interval demand over N contiguous subintervals;
means for storing a maximum demand;
means for replacing said maximum demand with said interval demand if said interval demand exceeds said maximum demand;
said processor including a volatile memory;
a non-volatile memory;
means responsive to a predetermined reduction in a voltage fed to said electric meter for enabling a first transfer of at least said maximum demand, a value representing a time at which a subinterval is interrupted by said predetermined reduction in said voltage and a plurality of programmed constants from said volatile memory to said non-volatile memory;
means responsive to a predetermined restoration in a voltage fed to said electric meter for enabling a second transfer of said maximum demand, said value and said plurality of constants from said non-volatile memory to said volatile memory; and means for resuming operation of said demand register following said second transfer at a time in a first subinterval corresponding to a time represented by said value.
a processor;
means in said processor for calculating a rolling demand including means for summing a demand in a subinterval with demands in a preceding N-1 subintervals to derive an interval demand over N contiguous subintervals;
means for storing a maximum demand;
means for replacing said maximum demand with said interval demand if said interval demand exceeds said maximum demand;
said processor including a volatile memory;
a non-volatile memory;
means responsive to a predetermined reduction in a voltage fed to said electric meter for enabling a first transfer of at least said maximum demand, a value representing a time at which a subinterval is interrupted by said predetermined reduction in said voltage and a plurality of programmed constants from said volatile memory to said non-volatile memory;
means responsive to a predetermined restoration in a voltage fed to said electric meter for enabling a second transfer of said maximum demand, said value and said plurality of constants from said non-volatile memory to said volatile memory; and means for resuming operation of said demand register following said second transfer at a time in a first subinterval corresponding to a time represented by said value.
2. A demand register according to claim 1 wherein said means for resuming operation includes means for providing a grace period following said second transfer during which a start of demand metering is delayed.
3. A demand register according to claim 1, further comprising means for changing a functional opera-tion of said demand register between a first operation and a second operation, said means for changing a func-tional operation including means for enabling said first transfer in response to changing said functional operation from said first operation to said second operation and for enabling said second transfer in response to changing said functional operation from said second operation to said first operation.
4. A demand register according to claim 3 wherein said means for resuming operation includes means for providing a grace period following said second transfer during which a start of demand metering is delayed.
5. A demand register according to claim 1 wherein a data protocol for communication between said volatile memory and said non-volatile memory is incompatible, further comprising:
formatting a first data message for transmission from said volatile memory to said non-volatile memory containing at least a leading portion which said non-volatile memory ignores, a remainder of said first data message including a data protocol which said non-volatile memory is capable of accepting; and processing a second data message received in said volatile memory from said non-volatile memory by at least a selective shift and an ignoring of at least part of said second data whereby a remainder of said second data message includes a data protocol which said volatile memory is capable of accepting.
formatting a first data message for transmission from said volatile memory to said non-volatile memory containing at least a leading portion which said non-volatile memory ignores, a remainder of said first data message including a data protocol which said non-volatile memory is capable of accepting; and processing a second data message received in said volatile memory from said non-volatile memory by at least a selective shift and an ignoring of at least part of said second data whereby a remainder of said second data message includes a data protocol which said volatile memory is capable of accepting.
6. A demand register according to claim 1 further comprising:
means for copying data from a non-volatile memory of a first demand register which has been removed from said electric meter to a second demand register before it is installed in said electric meter;
said means for copying including means in said first demand register for recognizing a removal of said first demand register as the equivalent of an impending power outage and for transferring data from said volatile memory to a first non-volatile memory in said first demand register;
said programmer including means for reading a content of said first non-volatile memory and for temporarily storing said content;
said programmer further including means for writing said content into a second non-volatile memory in said second demand register; and means in said demand register for recognizing an installation of said second demand register in said electric meter as the equivalent of a resumption of said voltage to said electric meter whereby said second transfer from said non-volatile memory to said volatile memory is performed and normal operation of said electric meter including said second demand register is resumed.
7. A demand register for an electric meter comprising:
a processor;
means in said processor for calculating a rolling demand including means for summing a demand in a subinterval with demands in a preceding N-1 subintervals to derive an interval demand over N
contiguous subintervals;
means for storing a maximum demand;
means for replacing said maximum demand with said interval demand if said interval demand exceeds said maximum demand;
said processor including a volatile memory;
a non-volatile memory;
means responsive to a predetermined reduction in a voltage fed to said electric meter for enabling a Claim 7 continued:
first transfer of at least said maximum demand, a value representing a time at which a subinterval is interrupted by said predetermined reduction in said voltage and a plurality of programmed constants from said volatile memory to said non-volatile memory;
means responsive to a predetermined restoration in a voltage fed to said electric meter for enabling a second transfer of said maximum demand, said value and said plurality of constants from said non-volatile memory to said volatile memory;
means for resuming operation of said demand register following said second transfer at a time in a first subinterval corresponding to a time represented by said value;
means for changing a functional operation of said demand register between a first operation and a second operation;
said means for changing a functional operation including means for enabling said first transfer in response to changing said functional operation from said first operation to said second operation and for enabling said second transfer in response to changing said functional operation from said second operation to said first operation;
said means for resuming operation including means for providing a grace period following at least some of said second transfers during which a start of demand metering is delayed;
a data protocol for communication between said volatile memory and said non-volatile memory being incompatible;
means for formatting a first data message for transmission from said volatile memory to said non-volatile memory containing at least a leading portion which said non-volatile memory ignores, a remainder of said first data message including a data protocol which
means for copying data from a non-volatile memory of a first demand register which has been removed from said electric meter to a second demand register before it is installed in said electric meter;
said means for copying including means in said first demand register for recognizing a removal of said first demand register as the equivalent of an impending power outage and for transferring data from said volatile memory to a first non-volatile memory in said first demand register;
said programmer including means for reading a content of said first non-volatile memory and for temporarily storing said content;
said programmer further including means for writing said content into a second non-volatile memory in said second demand register; and means in said demand register for recognizing an installation of said second demand register in said electric meter as the equivalent of a resumption of said voltage to said electric meter whereby said second transfer from said non-volatile memory to said volatile memory is performed and normal operation of said electric meter including said second demand register is resumed.
7. A demand register for an electric meter comprising:
a processor;
means in said processor for calculating a rolling demand including means for summing a demand in a subinterval with demands in a preceding N-1 subintervals to derive an interval demand over N
contiguous subintervals;
means for storing a maximum demand;
means for replacing said maximum demand with said interval demand if said interval demand exceeds said maximum demand;
said processor including a volatile memory;
a non-volatile memory;
means responsive to a predetermined reduction in a voltage fed to said electric meter for enabling a Claim 7 continued:
first transfer of at least said maximum demand, a value representing a time at which a subinterval is interrupted by said predetermined reduction in said voltage and a plurality of programmed constants from said volatile memory to said non-volatile memory;
means responsive to a predetermined restoration in a voltage fed to said electric meter for enabling a second transfer of said maximum demand, said value and said plurality of constants from said non-volatile memory to said volatile memory;
means for resuming operation of said demand register following said second transfer at a time in a first subinterval corresponding to a time represented by said value;
means for changing a functional operation of said demand register between a first operation and a second operation;
said means for changing a functional operation including means for enabling said first transfer in response to changing said functional operation from said first operation to said second operation and for enabling said second transfer in response to changing said functional operation from said second operation to said first operation;
said means for resuming operation including means for providing a grace period following at least some of said second transfers during which a start of demand metering is delayed;
a data protocol for communication between said volatile memory and said non-volatile memory being incompatible;
means for formatting a first data message for transmission from said volatile memory to said non-volatile memory containing at least a leading portion which said non-volatile memory ignores, a remainder of said first data message including a data protocol which
Claim 7 continued:
said non-volatile memory is capable of accepting;
means for processing a second data message received in said volatile memory from said non-volatile memory by at least a selective shift and an ignoring of at least part of said second data whereby a remainder of said second data message includes a data protocol which said volatile memory is capable of accepting;
means for copying data from a non-volatile memory of a first demand register which has been removed from said electric meter to a second demand register before it is installed in said electric meter;
said means for copying including means in said first demand register for recognizing a removal of said first demand register as the equivalent of an impending power outage and for transferring data from said volatile memory to a first non-volatile memory in said first demand register;
said means for copying further including a programmer;
said programmer including means for reading a content of said first non-volatile memory and for tem-porarily storing said content;
said programmer further including means for writing said content into a second non-volatile memory in said second demand register;
and means in said second demand register for recognizing an installation of said second demand register in said electric meter as the equivalent of a resumption of said voltage to said electric meter whereby said second transfer from said non-volatile memory to said volatile memory is performed and normal operation of said electric meter including said second demand register is resumed.
said non-volatile memory is capable of accepting;
means for processing a second data message received in said volatile memory from said non-volatile memory by at least a selective shift and an ignoring of at least part of said second data whereby a remainder of said second data message includes a data protocol which said volatile memory is capable of accepting;
means for copying data from a non-volatile memory of a first demand register which has been removed from said electric meter to a second demand register before it is installed in said electric meter;
said means for copying including means in said first demand register for recognizing a removal of said first demand register as the equivalent of an impending power outage and for transferring data from said volatile memory to a first non-volatile memory in said first demand register;
said means for copying further including a programmer;
said programmer including means for reading a content of said first non-volatile memory and for tem-porarily storing said content;
said programmer further including means for writing said content into a second non-volatile memory in said second demand register;
and means in said second demand register for recognizing an installation of said second demand register in said electric meter as the equivalent of a resumption of said voltage to said electric meter whereby said second transfer from said non-volatile memory to said volatile memory is performed and normal operation of said electric meter including said second demand register is resumed.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000484612A CA1233519A (en) | 1985-06-20 | 1985-06-20 | Electronic demand register |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000484612A CA1233519A (en) | 1985-06-20 | 1985-06-20 | Electronic demand register |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1233519A true CA1233519A (en) | 1988-03-01 |
Family
ID=4130779
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000484612A Expired CA1233519A (en) | 1985-06-20 | 1985-06-20 | Electronic demand register |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1233519A (en) |
-
1985
- 1985-06-20 CA CA000484612A patent/CA1233519A/en not_active Expired
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| MKEX | Expiry |