GB1563676A

GB1563676A - Maximumdemand electricity meters

Info

Publication number: GB1563676A
Application number: GB629078A
Authority: GB
Original assignee: Heliowatt Werke Elektrizitaet GmbH
Current assignee: Heliowatt Werke Elektrizitaet GmbH
Priority date: 1977-02-17
Filing date: 1978-02-17
Publication date: 1980-03-26
Also published as: ATA116578A; CH621630A5; FR2381312B1; DE2707200A1; FR2381312A1

Abstract

The current supply device of the maximum-demand mechanism (MW) provides a direct voltage and its voltage regulator (SR) supplies a regulated feed voltage to the maximum-demand mechanism. The maximum-demand mechanism has a computer. In the event of a mains failure, an unambiguous signal output is supplied in time to the maximum-demand mechanism in order to initiate continued operation on return of the mains. This involves capacitors (C1, C2) and non-volatile memories. <IMAGE>

Description

(54) MAXIMUM-DEMAND ELECTRICITY METERS (71) We, HELIOWATT WERKE ELEKTRIZITATS-GESELLSCHAFT mbH, a German company of Wilmersdorfer Strasse 39, 1000 Berlin 12, Federal Republic of German, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to electronic maximum-demand electricity meters, and is particularly concerned with power supply arrangements therefor.

Electronic maximum-demand meters desireably include means for informing a maximum-demand register in good time when the mains fails or when the mains voltage falls below a preset threshold. This information must be given early enough to ensure that the maximum-demand register can carry out all necessary logic and computing operations before its feed voltage collapses. When the mains supply is restored, the maximum-demand register must recommence operation only when completely satisfactory feed voltage supply has been ensured. Brief mains surges or reductions should not cause the maximumdemand register to operate faultily.

The invention is concerned with providing means by which unambiguous mains failure signals are supplied to a maximum-demand register, and which initiates resumption of running on restoration of the mains supply.

According to the present invention there is provided an electronic maximum-demand electricity meter comprising a maximumdemand register, a non-volatile store, and a power supply arrangement which comprises a voltage regulator and comparing means, the voltage regulator being arranged to receive a unidirectional input voltage and to feed a regulated output voltage to the register, the comparing means being arranged to compare said input voltage with upper and lower threshold values and to emit an output signal which assumes a first value when said input voltage exceeds the upper threshold value and a second value when said input voltage falls below the lower threshold value, the lower threshold value being in excess of the minimum value of the input voltage which is acceptable to the voltage regulator, and the register being arranged to receive said output signal and to operate normally only when the said output signal has its first value, and to transmit data into the non-volatile store when said output signal has its second value.

For a better understanding of the invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawing, the single figure of which is a block circuit diagram of an electronic maximum-demand electricity meter in accordance with the invention.

In the illustrated meter, there is provided from the voltages of all of three phases (or alternatively from the voltage of only one phase), in a manner known per se by rectification, either directly or through suitable mains transformers or taps or additional windings of voltage coils of the meter, a unidirectional input voltage to a voltage regulator SR, which input voltage is present on a first capacitor C1 operating as a filtering and buffer capacitor. Advantageously, there is provided a Zener diode ZD, which prevents excessive rise of the voltage at the first capacitor C1. The voltage regulator SR produces at its output a regulated feed voltage for a maximum-demand register MW, which is filtered and buffered by a second capacitor C2.

As the input voltage for a signal device SE. there is employed the unregulated input voltage of the voltage regulator SR. The signal device SE compares this input voltage with an upper and a lower limit or threshold value. When the upper limit value is exceeded, the output signal from the device SE, which is preferably constructed in bistable form, is changed over to the logic state "1", and this signal informs the maximumdemand register MW that it can proceed with its normal operation. The maximumdemand register MW is so constructed that it performs no operations before the arrival of the aforesaid signal, even if it has already received sufficient feed voltage from the output of the voltage regulator SR. When the input voltage of the signal device SE falls below the lower limit value, its output signal changes to the logic state "0". This signal informs the maximum-demand register MW of an impending mains failure and causes all the data which is to be saved to be transmitted into a non-volatile store. Preferably, the register MW is arranged to transmit data into the non-volatile store in order of priority of the importance of the data.

After completion of the operations provided for on mains failure, the maximum-demand register MW stops. even if a sufficiently high feed voltage is still present.

The advantage of this arrangement resides in that it is not the feed voltage itself, i.e. the voltage at the output of the voltage regulator SR or at the second capacitor C2, but the input voltage of the voltage regulator SR that is monitored and compared in the device SE.

Most electronic component parts, including digital circuits such as microcomputer switching circuits, for example, only operate reliably within narrow tolerances for the feed voltage. If this feed voltage were directly monitored, a precision comparator having adjustable switching thresholds would be necessary and the buffer capacitors C1, C2 would have to be so designed as to hold the feed voltage of the maximumdemand register within the prescribed tolerances until all data to be saved has been transmitted into the non-volatile store. In addition, in the case of direct monitoring of the feed voltage, the voltage at the output of the voltage regulator SR decreases by a measurable amount only when the input voltage of the latter is so low that regulation ceases.

On cessation of the regulation, there suddenly appears at the output of the regulator a high ripple voltage, which can be in itself sufficient to cause a serious disturbance in the operation of particular microcomputer switching circuits, despite the fact that the mean value lies within the tolerances. Also, from the instant that regulation ceases, the output voltage of the regulator follows the further decreasing input voltage.

These disadvantages are avoided in the illustrated arrangement.

The two switching thresholds of the signal device SE lie far above the input voltage required by the regulator SR for reliable operation. When the mains is switched on, the signal device consequently does not respond until the input voltage of the voltage regulator has exceeded the minimum necessary value for its output voltage to have reached its desired value. On failure of the mains, the signal device SE responds even while the input voltage of the regulator is still far above the minimum acceptable value, so that satisfactory supply of the maximum-demand register MW with the regulated feed voltage is ensured, until the input voltage of the regulator has fallen from the lower switching threshold of the signal device to the voltage at which the regulator ceases to operate. The function of buffering is thus shifted principally to the first capacitor C1. In this way, good utilisation of the first capacitor C1 is obtained, because the voltage present thereat can fluctuate by relatively large amounts in both directions without the regulated feed voltage of the maximum-demand register being influenced. Mains surges and reductions initiate the mains failure signal NS only when they are of such extent that the voltage at the capacitor Cl crosses one of the switching thresholds of the signal device SE.

In an advantageous development of the invention, the signal device SE comprises a bistable trigger circuit, for example, a complementary Schmitt trigger, the two switching thresholds preferably being derived from a reference voltage which is independent of the input and feed voltages, for example, from one or two Zener diodes. In addition, it is desirable for the input voltage to the signal device SE to be differently delayed by suitable RC elements for the two switching thresholds and to be freed from disturbances. Advantageously, the signal for the upper switching threshold is delayed to a greater extent than the signal for the lower switching threshold. The result is thereby obtained that the turn-off signal is produced relatively rapidly and the turn-on signal is produced with a relatively long delay in order that the maximum-demand register may not be started at every brief restoration of the mains voltage, for example, in the event of abortive attempts at restoration by the electicity supply undertaking.

In addition, circuit elements are provided by which the energy contained in the delay elements at the input of the signal device SE are dissipated substantially without delay when the voltage at the first capacitor C1 falls.

In German Patent Applications Nos. P 2613112 (corresponding British No. 11692/ 77) serial No 1524794, P2630969 (corres ponding British 28627/77) serial No.

1524795, P 2633182 and P 2635345 (corresponding British 30985/77), serial No.

1539128 there are described electronic maximum-demand registers comprising a microcomputer. The present invention is applicable to such and other arrangements, in which cases the output signal NS of the signal device SE should be suitably applied to the computer in order that, on recognition of a mains failure, no unnecessary operations have to be performed, but the operations which are necessary on mains failure are performed as rapidly as possible.

If the computer has an interrupt input, the signal NS is applied thereto. If the computer has available interrupt inputs of different grades, the output signal NS is preferably applied to a non-maskable interrupt input. If interrupt inputs of different pnoritys are provided, the signal NS is preferably given the highest priority. The computer is so programmed that, on recognition of mains failure, which is communicated to it through a corresponding interrupt input, it transmits into a non-volatile store, in the interrupt routine, that data which is to be saved.

If the computer employed has no interrupt input, the signal NS must be tested as to its logic state at sufficiently short intervals of time, programme-controlled by the computer, in the same way as the other input signals of the latter.

The computer of a maximum-demand register may have, inter alia, the object of deriving times for measuring period resets, and where necessary, for automatic monthly resets and other purposes from a suitable reference frequency. For this purpose, the mains frequency is preferably employed, this frequency being applied to the computer by way of one of its inputs. The computer can recognise, under program control, a mains failure from the absence of a predetermined number of mains cycles.

This monitoring of the individual mains cycles by the computer may be combined with the previously described signal genera tion by the signal device SE, for example. by the computer resuming a maximum-demand calculation, when not only the signal NS is present, but also a predetermined number of mains cycles has been counted without disturbance. As long as distorted cycles are included, the computer assumes that the mains has not yet with certainty been restored. On the other hand, the computer can conclude from the occurrence of dis tored cycles or from the absence of indi vidual cycles, even before the signal NS has ceased, that a mains failure is imminent, and it can then, for example. immediately com mence storage operations, it being immate rial if in doing so it stores values unnecessarily.

WHAT WE CLAIM IS: 1. An electronic maximum-demand electricity meter comprising a maximumdemand register, a non-volatile store, and a power supply arrangement which comprises a voltage regulator and comparing means, the voltage regulator being arranged to receive a unidirectional input voltage and to feed a regulated output voltage to the register, the comparing means being arranged to compare said input voltage with upper and lower threshold values and to emit an output signal which assumes a first value when said input voltage exceeds the upper threshold value and a second value when said input voltage falls below the lower threshold value, the lower threshold value being in excess of the minimum value of the input voltage which is acceptable to the voltage regulator, and the register being arranged to receive said output signal and to operate normally only when said output signal has its first value, and to transmit data into the non-volatile store when said output signal has its second value.

2. A meter according to claim 1, wherein the power supply arrangement includes rectifying means for providing said unidirectional input voltage.

3. A meter according to claim 2, wherein said rectifying means is arranged to receive polyphase inputs.

4. A meter according to claim 1, 2 or 3, wherein the power supply arrangement includes first and second capacitors on which said input and output voltages respectively appear.

5. A meter according to any preceding claim, wherein the register is arranged to transmit data into the non-volatile store in order of priority of the importance of the data.

6. A meter according to any preceding claim, wherein the comparing means comprises a complementary Schmitt trigger.

7. A meter according to any preceding claim, wherein the upper and lower threshold values are derived from a reference voltage which is independent of the output voltage of the voltage regulator.

8. A meter according to any preceding claim, wherein the comparing means comprises delay means which provides a delay in a rise in magnitude of said input voltage, as compared in the comparing means, towards the upper and lower threshold values, the delay for the upper value being greater than that for the lower value, and provides substantially no delay in a fall in the magnitude of said input voltage as compared in the comparing means.

9. A meter according to any preceding claim, wherein the maximum-demand register comprises a computer having a plurality

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

ponding British 28627/77) serial No.

1524795, P 2633182 and P 2635345 (corresponding British 30985/77), serial No.

1539128 there are described electronic maximum-demand registers comprising a microcomputer. The present invention is applicable to such and other arrangements, in which cases the output signal NS of the signal device SE should be suitably applied to the computer in order that, on recognition of a mains failure, no unnecessary operations have to be performed, but the operations which are necessary on mains failure are performed as rapidly as possible.

If the computer has an interrupt input, the signal NS is applied thereto. If the computer has available interrupt inputs of different grades, the output signal NS is preferably applied to a non-maskable interrupt input. If interrupt inputs of different pnoritys are provided, the signal NS is preferably given the highest priority. The computer is so programmed that, on recognition of mains failure, which is communicated to it through a corresponding interrupt input, it transmits into a non-volatile store, in the interrupt routine, that data which is to be saved.

If the computer employed has no interrupt input, the signal NS must be tested as to its logic state at sufficiently short intervals of time, programme-controlled by the computer, in the same way as the other input signals of the latter.

The computer of a maximum-demand register may have, inter alia, the object of deriving times for measuring period resets, and where necessary, for automatic monthly resets and other purposes from a suitable reference frequency. For this purpose, the mains frequency is preferably employed, this frequency being applied to the computer by way of one of its inputs. The computer can recognise, under program control, a mains failure from the absence of a predetermined number of mains cycles.

This monitoring of the individual mains cycles by the computer may be combined with the previously described signal genera tion by the signal device SE, for example. by the computer resuming a maximum-demand calculation, when not only the signal NS is present, but also a predetermined number of mains cycles has been counted without disturbance. As long as distorted cycles are included, the computer assumes that the mains has not yet with certainty been restored. On the other hand, the computer can conclude from the occurrence of dis tored cycles or from the absence of indi vidual cycles, even before the signal NS has ceased, that a mains failure is imminent, and it can then, for example. immediately com mence storage operations, it being immate rial if in doing so it stores values unnecessarily.

WHAT WE CLAIM IS: 1. An electronic maximum-demand electricity meter comprising a maximumdemand register, a non-volatile store, and a power supply arrangement which comprises a voltage regulator and comparing means, the voltage regulator being arranged to receive a unidirectional input voltage and to feed a regulated output voltage to the register, the comparing means being arranged to compare said input voltage with upper and lower threshold values and to emit an output signal which assumes a first value when said input voltage exceeds the upper threshold value and a second value when said input voltage falls below the lower threshold value, the lower threshold value being in excess of the minimum value of the input voltage which is acceptable to the voltage regulator, and the register being arranged to receive said output signal and to operate normally only when said output signal has its first value, and to transmit data into the non-volatile store when said output signal has its second value.
2. A meter according to claim 1, wherein the power supply arrangement includes rectifying means for providing said unidirectional input voltage.
3. A meter according to claim 2, wherein said rectifying means is arranged to receive polyphase inputs.
4. A meter according to claim 1, 2 or 3, wherein the power supply arrangement includes first and second capacitors on which said input and output voltages respectively appear.
5. A meter according to any preceding claim, wherein the register is arranged to transmit data into the non-volatile store in order of priority of the importance of the data.
6. A meter according to any preceding claim, wherein the comparing means comprises a complementary Schmitt trigger.
7. A meter according to any preceding claim, wherein the upper and lower threshold values are derived from a reference voltage which is independent of the output voltage of the voltage regulator.
8. A meter according to any preceding claim, wherein the comparing means comprises delay means which provides a delay in a rise in magnitude of said input voltage, as compared in the comparing means, towards the upper and lower threshold values, the delay for the upper value being greater than that for the lower value, and provides substantially no delay in a fall in the magnitude of said input voltage as compared in the comparing means.
9. A meter according to any preceding claim, wherein the maximum-demand register comprises a computer having a plurality

of interrupt inputs, and is arranged to receive said output signal from the comparing means on one of the interrupt inputs which is of highest priority or is nonmaskable.
10. A meter according to any preceding claim, wherein the maximum-demand register comprises a computer which is arranged to receive a mains frequency signal and to count the cycles thereof, the computer being so programmed that, when it recognises distortion or absence of said cycles, it starts to transmit data into the non-volatile store irrespective of said output signal from the comparing means, and only when it has counted a predetermined number of undistorted and uninterrupted said cycles and when said output signal has its first value does the computer resume normal operation.
11. An electronic maximum-demand electricity meter substantially as hereinbefore described with reference to the accmopanying drawing.