GB2312771A

GB2312771A - Electricity control system with pre-payment and electricity credit balance indication

Info

Publication number: GB2312771A
Application number: GB9704129A
Authority: GB
Inventors: Alain Gilot
Original assignee: Schneider Electric SE
Current assignee: Schneider Electric SE
Priority date: 1996-05-02
Filing date: 1997-02-27
Publication date: 1997-11-05
Anticipated expiration: 2017-02-27
Also published as: GB9704129D0; FR2748338B1; FR2748338A1; PT102001A; GB2312771B; ZA973695B; PT102001B

Abstract

The system comprises an electricity management circuit to which an electricity credit can be allocated by entering a pre-payment code. The circuit reduces the amount of the electricity credit according to the measured electricity consumption. When the electricity credit balance (C) has been used up, the circuit causes opening of a circuit breaker. At the user's request, the credit balance (C) can be displayed (F6). It can also be displayed (F9) in the form of an estimate (T) of the remaining consumption time before his credit is used up and the circuit breaker opens, this estimate being calculated on the basis of the mean consumption (Pmean) of the user, calculated from data stored between two purchases at least. When this estimate (T) is lower than a previous alert threshold (4 days), the user is warned of this. He is also warned when the electricity credit balance (C) reaches an alert threshold formed by a fixed threshold and/or a predetermined percentage of the mean credit purchased by the user.

Description

ELECTRICITY CONTROL SYSTEM WITH PRE-PAYMENT WITH ELECTRICITY CREDIT BALANCE INDICATION The invention relates to an electricity control system with pre-payment comprising electricity management means comprising: - means for entering and storing an electricity credit purchased by a user, - means for measuring the electricity consumed by the user, - means for determining an electricity credit balance according to said electricity credit and to the quantity of electricity consumed, - means for displaying the electricity credit balance, - electricity comparison means for comparing the electricity credit balance with a first alert threshold representative of a predetermined quantity of electricity, - indication means actuated by the electricity comparison means when the credit balance is lower than or equal to the first threshold, - means for converting the electricity credit balance into an estimate of the remaining consumption time, - and means for displaying said time estimate.

Electricity control systems with prepayment are known wherein each user has a management circuit, with a circuit for measuring the electricity used, connected to a switch or a circuit breaker to interrupt the user's electricity supply when the amount of an electricity credit, stored in the management circuit and reduced as and when electricity is consumed, has been used up. The amount of the credit can be modified by entering a prepayment code into the management circuit. In known systems, this code is entered either via a keypad or by means of a magnetic card, or by means of an electronic chip token.

In state of the art systems, it is scheduled to display the electricity credit balance at the user's request. Moreover, it is scheduled to wam the user when this balance drops below certain preset alert thresholds. In conventional manner, a first lightemitting diode lights up when an alert threshold is reached, for example when the balance becomes lower than or equal to 50 KWH. A second lightemitting diode is also provided to warn the user that his balance has become lower than or equal to another alert threshold, lower than the previous one, and that he must quickly provision his system with a new electricity credit. To give an example, this other threshold can be about 10 KWH.

The object of the invention is to improve the efficiency of indication of a low electricity credit balance to a user.

This object is achieved by the fact that the beginning and end of a consumption cycle being defined by entry of two successive electricity credits, the electricity management means comprise means for estimating the mean consumption of at least one previous cycle, the conversion means converting the electricity credit balance into an estimate of the remaining consumption time according to said mean consumption, duration comparison means for comparing said estimate of the remaining consumption time with a previous alert threshold representative of a preset time, the duration comparison means actuating the indication means when the estimate of the remaining consumption time is lower than or equal to a previous alert threshold.

According to a preferred embodiment, the electricity management means comprise means for measuring the instantaneous power, the conversion means converting the electricity credit balance into an estimate of the remaining consumption time according to the instantaneous power when the electricity credit balance is lower than or equal to the first alert threshold.

Actuation of the indication means preferably causes continuous display of the electricity credit balance and display, at the user's request, of the estimate of the remaining consumption time, expressed in days and hours, as well as actuation of an indicator lamp when the electricity credit balance is lower than or equal to the first alert threshold.

Thus, the estimate of the remaining consumption time is normally calculated on the basis of the mean consumption of the user over at least one purchasing cycle. As soon as the estimate of the remaining consumption time reaches a preset previous alert threshold, the user is informed of this preferably by a continuous display of the credit balance, and on request, by display of the estimate of the remaining consumption time, still calculated on the basis of his mean consumption. Thus, this previous alert is performed on the basis of personalised criteria, according to the mean consumption of the user. The user is also alerted when the credit balance reaches a preset alert threshold, considered as critical and requiring a new electricity credit to be entered in the system in the short term. The alert is then preferably given on the one hand by means of an indicator lamp which is actuated and on the other hand by continuous display of the electricity credit balance. The user can also, on request, display the estimate of the remaining consumption time. This is then calculated on the basis of his instantaneous consumption re-updated in real time.

According to a development of the invention, the previous alert threshold is a few days.

The first alert threshold is preferably fixed andlor representative of a predetermined percentage of the amount of the purchased electricity credit entered in the system during a cycle or of the amount of the mean electricity credit purchased over at least two successive cycles.

Other advantages and features will become more clearly apparent from the following description of an illustrative embodiment of the invention given as a nonwrestrictive example only and represented in the accompanying drawings in which: Figure 1 represents an electricity control system with pre-payment according to the prior art, in which the invention can be implemented, Figures 2 to 5 illustrate particular embodiments of processing flow charts for implementation of the invention in a system according to figure 1.

The electricity control system with prepayment of figure 1 comprises a management circuit 1 and a switch 2. The switch 2 comprises contacts 3 fitted on power supply lines L1 and L2 designed to supply electricity to a user. Opening of the contacts 3 is performed by a relay 4 of the switch 2 under the control of the management circuit 1.

The management circuit 1 comprises a measuring circuit 5 connected to a microprocessor-based processing circuit 6. The measuring circuit 5 can comprise current sensors, and possibly voltage sensors, fitted on the lines L1 and L2, the processing circuit 6 then being able to calculate the electrical power delivered to the user and the electricity consumed. Alternately, the measuring circuit 5 can comprise an electricity meter of known type disposed in such a way as to measure the electricity supplied te the user by the power supply lines L1 and L2.

In the management circuit 1, the processing circuit 6 is connected to a memory 7, a display circuit 8 and a keypad 9. An electricity credit balance C is stored in the memory 7. The processing circuit 6 decreases the amount of this electricity credit balance according to the amount of electricity used W, the information necessary for measurement andlor calculation of the amount of electricity used being supplied to the processing circuit by the measuring circuit 5. The amount of the stored credit balance can be modified by means of a code entered via the keypad 9 accessible to the user. The display circuit 8 enables the user to be informed of the amount of the stored credit balance, i.e. the remaining electricity credit.

When the amount of the electricity credit balance stored in the management circuit has been used up, the processing circuit 6 operates the relay 4 so that the latter opens the contacts 3, causing the electricity supply to the user by the power supply lines L1 and L2 to be interrupted.

As represented in the flow chart of figure 2, the routine for power measurement and calculation of the electricity credit balance C comprises, in known manner, a first stage F1 of measurement and storing of the instantaneous power P and of the electricity consumed W between two measuring cycles. Then, in a stage F2, the balance C is updated, the amount of the balance C being reduced by the amount W of the electricity consumed. The processing circuit then checks, in a stage F3, if the credit balance C has been used up. If the amount of the balance C has been used up (C = 0), then the processing circuit proceeds to open the contacts 3 of the switch during a stage F4. To achieve this, the processing circuit 6 orders excitation of the relay 4 which opens the contacts 3. To supply his installation again, the user has to reclose the switch 2 manually. However, any closing of the contacts before a new electricity credit, which must not be zero, is entered in the management circuit 1 by means of a credit code, automatically leads to the contacts 3 opening again.

If the balance C is not zero, the processing circuit goes back to the stage F1 of measurement of P and W.

In parallel with the electricity measurement and credit balance C calculation routine, the processing circuit performs electricity management according to the flow charts represented in figures 3 to 5.

In the particular embodiment represented, a management cycle begins with a stage F5 during which the processing circuit checks if a display has been requested by the user or if a code has been entered. In practice, the display request and the beginning of a code entry can be achieved using an identical predetermined key of the keypad.

Actuating this key will have the same consequences at this level of the flow chart. In case of a display request or a code entry, the processing circuit then proceeds, in a stage F6, with display of the balance C. This display is preferably in alphanumerical form, the balance being expressed in KWH or in predetermined units corresponding to the units used when an electricity credit token is purchased.

After C has been displayed, the processing circuit checks, in a stage F7, if the user has requested a new display. If this is the case, it then calculates the estimate T of the remaining consumption time in a stage F8 and displays this estimate, expressed in days and hours, during a preset time, for example 5s, in a stage F9, before going back to the stage F6 in which C is displayed. The estimate of the remaining consumption time is obtained by calculating the ratio between the electricity credit balance C and the mean consumption Pmean, calculation of which will be explained in greater detail in figure 5. The mean consumption corresponds preFerably to the mean daily consumption of the user during the previous cycle. If this mean consumption is expressed in KWH/day, the estimate T can be expressed In days and hours.

If the processing circuit does not identify a display request during the stage F7, it then checks during a stage F10 if a code has been entered. If this is the case, the processing circuit processes this code in the manner represented in figure 5, which will be described in greater detail further on if a credit code is involved.

If, on the other hand, no code has been entered, the processing circuit then goes on to a stage F11 in which the estimate T is calculated. This calculation is performed in the same way as at F9, from the mean consumption Pmean.

After the stage F11, the processing circuit compares, in a stage F12, the estimate T of the remaining consumption time with a previous alert threshold. In the embodiment represented, this threshold is 4 days. If the estimate T is greater than 4 days, then the processing circuit clears the display of C in a stage F13 (blank display) before going back to stage F5 at the beginning of the management cycle. When on the other hand the estimate T is lower than or equal to 4 days, the processing circuit then goes on to an alert routine which will be described in greater detail with reference to figure 4.

When the user has neither requested display nor entered a code at F5, the processing circuit goes directly to the stage Fl 1 of calculating the estimate T from the mean consumption Pmean.

Thus, in normal operation, if no display request is made by the user and if no code is entered in the management circuit, the processing circuit calculates the estimate of the remaining consumption time, i.e. the availability time of the electricity supply, calculated on the basis of the mean consumption of this user during the previous cycle. This estimate is then compared to a previous alert threshold, preferably expressed in days. The management routine loops back on itself so long as the estimate T of the remaining consumption time remains greater than the previous alert threshold. Under these conditions the user can, on request, display the electricity credit balance C (F6) and if required the estimate T of the remaining consumption time (F9). He can also enter a code for example a credit code enabling the amount of the electricity credit balance C to be increased.

When the processing circuit detects (at F12) the fact that the estimate T of the remaining consumption time is lower than or equal to the previous alert threshold, it then goes on to an alert routine. In figure 4, this begins with a stage F14 in which C is displayed. Then the processing circuit, in a stage Fl 5, compares C to a predetermined percentage of the amount Camean of the mean electricity credit purchased over at least two successive cycles. In figure 4, this percentage is 10 %. If this minimum threshold is not reached, the processing circuit, in a stage F16, compares C to a fixed threshold. This fixed threshold is preferably about ten electricity units, 10 in the figure. If C is greater than this fixed threshold, the processing circuit goes on to a stage F17 where it checks if the user has requested a display. If this is the case, the estimate T of the remaining consumption time is calculated, in a stage F18 according to Pmean, in a similar manner to the calculation made in stages F8 or F11. The estimate is then displayed during a preset time, for example 5s, at a stage F19. The processing circuit then goes back to the stage F14 in which C is displayed.

If C is lower than or equal to 10 % of Camean or lower than or equal to 10, the processing circuit goes on to a stage F20 after the stages Fl 5 or F1 6. This stage F20 results in actuation of an indicator lamp. In the preferred embodiment of figure 3, this indicator lamp starts flashing. This indicator lamp can for example be formed by a light-emitting diode normally lit so long as the management circuit is powered on.

When this diode goes out, this means that the management circuit is no longer supplied. When it flashes on the other hand, this means both that the management circuit is powered on and that one of the minimum electricity credit thresholds has been reached. The electricity credit balance C displayed since the stage F14 is immediately indicated to the user. If the latter wishes, he requests display of its conversion into estimate T of the remaining consumption time. The processing circuit checks in the stage F21 if such a display is requested. If this is the case, it calculates T in a stage F22 to display it in a stage F23. In the stage F22, T is no longer calculated as before, but according to the instantaneous power P measured.

Thus, the value of T displayed in this case varies according to the present instantaneous electricity consumption of the user. The user can, by decreasing his consumption, easily observe the influence of this decrease over the time during which electricity is still available.

If no display request has been detected by the processing circuit during the stages F17 or F20, it then goes on to the input A of the flow chart of figure 3, i.e. to stage F10. Thus, so long as no new electricity credit is entered, the processing circuit loops back, after the stages Fl I and F12, on the alert routine. If a new electricity credit has not been entered, the value C in fact continues to decrease according to the electricity consumed, according to the flow chart of figure 2. The balance C decreasing the estimate decreases and then must remain lower than the previous alert threshold.

As soon as the estimate T is lower than or equal to 4 days, the value of C is displayed permanently and T can be displayed on request on the basis of the mean consumption of the user. Then, if C reaches or drops below one of the two thresholds constituted by 10 % of Camean and by 10 units, the alert indicator lamp then starts flashing and the estimate T can be displayed on request on the basis of the instantaneous consumption of the user.

Processing of a credit code, which takes place after the stage F10 if a credit code is entered in the management circuit, is represented in greater detail in figure 5.

During a stage F24, the processing circuit proceeds, in known manner, to read and validate a credit code corresponding to an electricity credit Ca purchased at a time Ta. The values Ca and Ta notably are decrypted and stored by the processing circuit. Then, in a stage F25, the processing circuit calculates the mean consumption Pmean of the user over the previous cycle. Pmean is obtained according to the following equation: Pmean + (Cd - C) I (Ta - Td) in which Cd is the value of the electricity balance stored after the previous credit code has been entered corresponding to the electricity credit balance at the beginning of the previous consumption cycle, after the electricity credit entered has been taken into account. Likewise, Td corresponds to the date of purchase of the previous credit stored when the previous credit code was entered. Thus, Pmean corresponds to the mean consumption between the last two credit token purchases, i.e. during the previous consumption cycle, the date of entry of the credit token being assimilated to its date of purchase.

Then the new electricity credit token entered is taken into account and added to the balance C to give the new credit balance C, in a stage F26. The credit balance C can then be displayed in F27, thus indicating to the user that the credit token which he has just entered has been duly taken into account.

The processing circuit then calculates, in a stage F28, the mean credit purchased over the previous consumption cycle and over the current consumption cycle, this value then being used to determine the alert threshold used during the stage F15 of figure 4. In the embodiment represented in figure 5: Camean = (Ca + Cap) t 2 where Cap is the amount of the credit purchased during the previous consumption cycle and stored when the previous credit code was entered.

Then, in the stages F29, F30 and F31, the processing circuit respectively stores the values C, Ta and Ca which become the values Cd, Td and Cap which will be used when a new credit code is subsequently entered to calculate Pmean and Camean.

The processing circuit then goes back to the management routine of figure 3. The value of the credit balance C having been increased by the amount of the credit Ca purchased, the estimate T then normally becomes greater than a mean consumption of 4 days, the display is extinguished (F13) and the management routine runs ordinarily until the moment when an alert threshold is reached (yes output of F12) or until a new code is entered (yes output of F10).

The invention is not limited to the embodiment described above. Comparison (Fl 5 and F16) of the credit balance C with the corresponding alert thresholds is in the embodiment represented performed only when the estimate T is lower than or equal to 4 days. This is satisfactory in most cases. However, it can be scheduled to perform this comparison also if the estimate T is greater than 4 days, i.e. in each management cycle, so as to wam the user that he has reached one of these thresholds due to an electricity consumption much greater than the mean consumption calculated according to the previous cycle.

Likewise, the mean credit purchased Camean can be replaced by the purchased credit Ca of the cycle.

Using the token purchase date as the cycle beginning date may sometimes give rise to certain problems. For example, if the user does not enter his credit codes in the order in which they were purchased, it is possible to have Td > Ta, whence a negative value of Pmean. In this case it is scheduled to ignore this calculated value and to keep the previously calculated value Pmean.

To avoid probiems of this kind, the actual date of entry of a credit code in the circuit can be used, provided that the management circuit comprises a calendar-clock representative of real time.

Claims

1. An electricity control system with pre-payment comprising electricity management means (1) comprising: - means for entering (9) and storing (7) an electricity credit (Ca) purchased by a user, - means (5, F1) for measuring the electricity (W) consumed by the user, - means (6, F2, F26) for determining an electricity credit balance (C) according to said electricity credit and to the quantity of electricity consumed (W), - means (8, F6, F14, F27) for displaying the electricity credit balance (C), - electricity comparison means (6, F15, F16) for comparing the electricity credit balance (C) with a first alert threshold representative of a predetermined quantity of electricity, - indication means actuated (F20) by the electricity comparison means (6) when the electricity credit balance (C) is lower than or equal to the first threshold, - means (6, F8, F11, F18, F22) for converting the electricity credit balance (C) into an estimate (T) of the remaining consumption time, - and means (8, F9, F19, F23) for displaying said time estimate (T), a system characterized in that the beginning and end of a consumption cycle being defined by the entry of two successive electricity credits (Cap, Ca), the electricity management means (1) comprise means (6, F25) for estimating the mean consumption (Pmean) of at least one previous cycle, the conversion means (F8,F11, F18) converting the electricity credit balance (C) into an estimate (T) of the remaining consumption time according to said mean electricity consumption (Pmean), duration comparison means (6, F12) for comparing said estimate (T) of the remaining consumption time with a previous alert threshold representative of a preset time, the duration comparison means actuating (F14) the indication means when the estimate (T) of the remaining consumption time is lower than or equal to a previous alert threshold.

2. The system according to claim 1, characterized in that the electricity management means (1) comprise means (5, F1) for measuring the instantaneous power (P), the conversion means converting (F22) the electricity credit balance (C) into an estimate (T) of the remaining consumption time according to the instantaneous power (P) when the electricity credit balance (C) is lower than or equal to the first alert threshold.

3. The system according to one of the claims 1 and 2, characterized in that the mean electricity consumption (Pmean) is representative of the daily consumption of the user.

4. The system according to any one of the claims 1 to 3, characterized in that actuation of the indication means causes continuous display (F14) of the electricity credit balance (C) and display (F19, F23), at the user's request (F17, F21), of the estimate (T)of the remaining consumption time, expressed in days and hours, as well as actuation (F20) of an indicator lamp when the credit balance (C) is lower than or equal to the first alert threshold.

5. The system according to any one of the claims 1 to 4, characterized in that the previous alert threshold is a few days (F12).

6. The system according to any one of the claims 1 to 5, characterized in that the first alert threshold is representative (Fl 5) of a predetermined percentage of the amount (Ca) of the purchased electricity credit entered in the system during a cycle or of the amount (Camean) of the mean electricity credit purchased over at least two successive cycles.

7. The system according to any one of the claims I to 5, characterized in that the first alert threshold is fixed (F16).

8. The system according to any one of the claims 1 to 5, characterized in that the first alert threshold is constituted by a fixed second threshold (F16) and by a third threshold (F15), representative of a predetermined percentage of the amount of the electricity credit (Ca, Camean) entered in the system, the electricity comparison means actuating indication means when the electricity credit balance (C) is lower than or equal to the second and third thresholds.

9. The system according to one of the claims 6 and 8, characterized in that the percentage is about 10 %.

10. The system according to one of the claims 7 and 8, characterized in that the fixed threshold is about ten electricity units.

11. An electricity control system with prepayment comprising electricity management means substantially as hereinbefore described with reference to the accompanying drawings.