FR2753016A1 - Prepaid electricity supplies for low-income consumers - Google Patents

Abstract

The group supply (P,N) is received by a 3OA 4-pole main switch (D). If 1-phase, the line poles (P1,P2,P3) operate in parallel. A microprocessor-based controller (1), with current sensor input (2,3,4), has memory (6) and display (7) facilities for regulating prepayment arrangements. Current-limiting, overcurrent and residual current protection are installed, also a pay-in register key-pad (8). Consumers (U11-U14; U21-U24; U31-U34) allotted to each distributor (P11/N11;P14/N14, etc.) each have a main switch (D11-D14;D21-D24;D31-D34) with overcurrent and residual protection. Typically, these trip if more than 2.5A is drawn and the main group switch if more than 10A. All consumers can lose supply if one illegally exceeds his limit. Satisfactory operation requires one consumer to accept responsibility for identifying offenders, settling disputes, maintaining prepayment, etc.

Description

PREPAYMENT ENERGY PROTECTION AND MANAGEMENT ASSEMBLY
The invention relates to a prepayment energy protection and management assembly supplied by an electrical network comprising a primary neutral conductor and at least one phase primary conductor, assembly comprising - prepayment energy management means comprising means for entering and storing an energy credit, means for measuring the current, means for counting the amount of energy consumed and means for reducing the amount of the memorized credit as a function of the amount of energy consumed, - protection means comprising means for interrupting the energy supply in the event of a fault as well as, under the control of the energy management means, when the amount of the credit is zero.

Prepaid energy control systems are known in which each user has a management circuit connected to a circuit for measuring the energy used and to a switch or a circuit breaker to interrupt the energy supply to the user when the amount of an energy credit, stored in the management circuit and reduced gradually as energy consumption is canceled. The amount of the credit can be modified by the introduction into the management circuit of a prepayment code. In known systems, this code is introduced either by means of a keyboard, or using a magnetic card, or by means of an electronic chip support.

Such a management circuit is often associated with a circuit breaker, more particularly with a differential connection circuit breaker, the system thus achieving both the protection of the installation by the circuit breaker, the management of energy as a function of the quantity d energy paid for by the user and stored in the management circuit, as well as the protection of people against direct or indirect contact.

This type of system, which minimizes the financial risks for the distributor, nevertheless requires an investment in equipment of too high a cost for small consumers with weak resources, in particular the consumers of certain rural communities.

It has been proposed to abandon metering entirely so as to minimize the cost of connecting small consumers to an electrical network. It would thus be possible to use very simplified connection equipment comprising for each user a very small connection circuit breaker, for example 2.5 A. In the absence of metering, payment of electricity to the distributor would be made on a flat rate basis, simply in the form of a subscription for example. To deter massive fraud by bridging the circuit breaker, it has been envisaged to have an additional, collective circuit breaker, upstream of the individual branch circuit breakers. For example, four individual 2.5A circuit breakers would be connected to a collective circuit breaker of 10
A. If one of the users short-circuits his individual circuit breaker to have a higher power, this fraud is detected by the collective circuit breaker which opens as soon as the total intensity of the current exceeds 10A. This would penalize all users connected to the collective circuit breaker. However, such a system has never been implemented because it poses problems from the point of view of selectivity, in particular because of the low calibers used and their proximity, and also because it does not provide any guarantee of payment to the distributor.

The object of the invention is to provide an economical system making it possible both to provide electrical protection for the end user and to count electricity with pre-paid energy management.

According to the invention, this object is achieved by the fact that the prepayment energy protection and management assembly is intended to supply a plurality of users, in that it comprises three secondary phase conductors upstream of the protection means, in that a predetermined number of users is connected to each secondary phase conductor, and in that the protection means comprise a common four-pole magnetic circuit breaker comprising a neutral pole crossed by the primary neutral conductor and three phase poles respectively crossed by one of the three secondary phase conductors, the current measurement means comprising three current sensors respectively associated with the three secondary phase conductors, the common circuit breaker comprising a control input connected to the energy management means , common to all users, so as to ensure the interruption of the power supply when the amount the credit is zero as well as in the event of an overload in one of the secondary phase conductors, the protection means also comprising a plurality of individual circuit breakers, associated respectively with each of the users and ensuring magnetic protection and differential protection of said user .

The incoming electrical network can be single-phase or three-phase.

Other advantages and characteristics will emerge more clearly from the following description of a particular embodiment given by way of nonlimiting example and represented in the appended figures in which FIG. 1 corresponds to a single-phase network and FIG. 2 to a three-phase network.

A plurality of users, 12 in FIG. 1, are connected to a single-phase electrical network comprising a primary conductor of neutral N and a primary conductor of phase P. The users are divided into three groups of 4 users, respectively U11 to U14, U21 to U24 and U31 to U34. The primary phase conductor P is connected to three secondary phase conductors, P1, P2 and P3, respectively associated with each of the user groups.

A four-pole circuit breaker D, common to all users, is supplied, pole by pole, respectively by the primary neutral N and secondary phase conductors P1, P2 and
P3. I1 is associated with a prepayment energy management circuit 1 connected to current sensors 2, 3 and 4, respectively associated with the secondary phase conductors P1, P2 and P3, to supply to circuit 1 signals representative of the current flowing the associated driver.

In known manner, the prepayment energy management circuit 1 comprises a processing circuit 5, with microprocessor, connected to a memory 6, a display 7, and an input circuit constituted by a keyboard 8 in the figure. The processing circuit 5 can control the opening of the circuit breaker D.

The connection of end users to the primary neutral conductor and to the secondary phase conductor associated with the group is carried out by means of individual circuit breakers, an individual circuit breaker DU being associated with a user Uij, where i corresponds to the number of the group considered (i = 1 to 3) and j corresponds to the number of the user in the group (in figure j = 1 to 4).

Each individual circuit breaker Dij is thus crossed by a final neutral conductor Nij, connected to the primary neutral conductor N, and by a final phase conductor Pij, connected to the corresponding secondary phase conductor Pi.

In a particular embodiment, each group of users has 4 users. The individual circuit breaker associated with a user is a very small size circuit breaker, for example of 2.5 A rating, comprising a differential of 30 mA. Such a power is for example sufficient to ensure the lighting and the use of a television set and a refrigerator. Each individual circuit breaker thus ensures the protection of property and people for the corresponding user. n also controls the authorized power at the individual level since it opens if the current exceeds 2.5A.

The common four-pole circuit breaker D is a very low power circuit breaker ensuring the protection of the distribution cables P1, P2, P3. In the embodiment considered, it is a 30A circuit breaker, with a selective differential of 500 mA. In fact, a 30A circuit breaker limited to 10A per phase is used, the neutral having to accept the currents of the 3 groups.

The energy management circuit 1 can perform an energy metering separately for each secondary phase conductor, therefore for each group of users, from the measurement of the current by the corresponding current sensor. This count can be stored in memory 6 and displayed on the display 7. As long as a non-zero energy credit is stored in the memory 6 of circuit 1, circuit 1 ensures the counting of the energy consumed. by each group of users, calculates the arithmetic sum of the energy consumed by the three groups and consequently reduces the amount of the memorized credit.

When the amount of the credit is zero, circuit 1 controls the opening of circuit breaker D, thereby interrupting the supply of electricity to all users connected to the common circuit breaker. As is known in prepayment management systems, the remaining credit can be displayed permanently by the circuit 1 and the amount of the credit can be modified at any time by the introduction into the management circuit of a code corresponding to the prepayment of a predetermined amount of energy.

Circuit breaker D automatically provides protection against short-circuits and against insulation faults in the 3 secondary phase conductors and in the neutral conductor. In addition, in connection with the management circuit 1, it ensures the control of the authorized power limit for all the users of a group, or overload control in one of the secondary phase conductors. For this, the management circuit 1 compares each of the measured currents with an appropriate long delay trip curve. Such a curve, corresponding to a current threshold of 10 A in the embodiment considered, nevertheless allows small overshoots for several minutes and strong peaks over a few seconds. Such a time delay is more particularly suited to the different types of loads normally connected in each assembly, for example to the use of refrigerators.

The assembly described above makes it possible to limit the cost of the installation for each user, while providing satisfactory protection of goods and people and ensuring financial security for the distributor thanks to the prepayment management circuit.

The set is in fact made up, for 12 end users, of 12 individual circuit breakers and of a centralized common prepayment set, itself constituted by the low-power four-pole circuit breaker D, 3 measurement sensors 2, 3 and 4, and the prepayment energy management circuit 1. The individual circuit breakers, of very small caliber, are very inexpensive and the price of the common assembly, divided by the number of users, is no longer prohibitive.

The use of a four-pole circuit breaker supplying the three user groups separately is particularly interesting. In fact, it makes it possible to supply three times more end customers with a single energy management circuit with associated prepayment, and its price is lower than that of three individual single-phase circuit breakers.

If one of the users tries to defraud by short-circuiting his individual circuit breaker to exceed the power allocated to him, this overload will be detected by the management circuit which is programmed to detect on each secondary phase conductor an overload greater than 4 times the maximum power allocated to each user. Such an overload then automatically leads to the opening of circuit breaker D and the interruption of the electricity supply to all users, whether or not they belong to the same group as the unscrupulous user.

A manager of the community formed by the users is responsible for the proper functioning of the whole, in particular the prepayment. In the event of fraud by a user leading to the interruption of the supply to all of the users, he will be responsible by them for detecting the fraudster. The responsibility for energy management is therefore transferred to the community.

The number of users per group is to be determined to allow an optimum solution.

Indeed, the greater the number of users per group, the lower the cost of an individual connection, the cost of the centralized unit being divided between a greater number of users. On the other hand, the higher the number of users per group, the greater the risk that an abuse by a single user will go unnoticed in the mass. Thus, a common circuit breaker D limited to 10A per phase makes it easy to detect fraud by a user among 4 having an individual circuit breaker of 2.5A or among 5 having an individual circuit breaker of 2A. On the other hand, if 20 users with an individual circuit breaker of 2.5A are connected to a common circuit breaker limited to 50A per phase, fraud by a single user is likely to go unnoticed.

In practice, an optimum solution is constituted by 4 users per group, with a common circuit breaker of 10A rating or by 8 users per group with a common circuit breaker of 20A rating, that is to say respectively 12 or 24 end users supplied by a primary network supplying 30A respectively. or 60A.

As a variant (FIG. 2) if the incoming network allows, that is to say if it is a 4-wire network comprising the neutral conductor N and three primary phase conductors offset by 1200, the primary supply can be three-phase. Each primary phase conductor is then connected to a corresponding secondary phase conductor P1, P2, P3.

The neutral conductor N is then traversed by the unbalanced current between phases, and not by the sum of the three single-phase currents. I1 can therefore be dimensioned for the same maximum current as each of the phases.

 It is then possible to supply three times more users than with a single-phase network, with a common circuit breaker of the same rating. For example, with a 30A four-pole circuit breaker supplied with three phase one can then connect 12 users to each secondary phase conductor, and for a 60A four-pole circuit breaker supplied with three phase one can connect 24 users with each secondary phase conductor, each individual circuit breaker being a 2.5A circuit breaker.

It is also possible, by keeping the same number of users as in the case of a single-phase network, to use a smaller four-pole circuit breaker, therefore less expensive. For example, 4 or 8 users can be connected to each secondary phase conductor, the four-pole circuit breaker being a circuit breaker of 10A rating or, respectively, of 20A rating.

In a preferred embodiment each individual circuit breaker is a circuit breaker provided with a socket (figs 1 and 2).

By appealing to the sense of collective responsibility for energy management, such a set makes it possible to bring an economic solution to the problem of electrification in rural areas with small consumers with few means, while ensuring a good security of goods and people and guaranteeing payment of electricity to the distributor.

Claims (7)

1 - Pre-payment energy protection and management assembly supplied by an electrical network comprising a primary neutral conductor (N) and at least one phase primary conductor (P), assembly comprising - means (1-4) for prepaid energy management comprising means (8) for entering and memorizing (6) an energy credit, means (2-4) for measuring the current, means for counting the quantity of energy consumed and means for reducing the amount of the memorized credit as a function of the quantity of energy consumed, - protection means comprising means for interrupting the supply of energy in the event of a fault as well as, under the control of the means for energy management, when the amount of the credit is zero, set characterized in that it is intended to supply a plurality of users (U11 U14, U21-U24, U31-U34), in that it comprises three secondary phase conductors (P1, P2, P3) upstream of the protection means, in that a predetermined number of users is connected to each secondary conductor phase and in that the protection means comprise a common four-pole magnetic circuit breaker (D) comprising a neutral pole crossed by the primary neutral conductor (N) and three phase poles respectively crossed by one of the three secondary phase conductors (P1 , P2, P3), the current measurement means comprising three current sensors (2-4) respectively associated with the three secondary phase conductors, the common circuit breaker (D) comprising a control input connected to the energy management means (1), common to all users, so as to ensure the interruption of the power supply when the credit amount is zero as well as in the event of an overload in one of the secondary phase conductors (P1-P3), the mo protective yen also comprising a plurality of individual circuit breakers (Dl l-D14, D21-D24, D31-D34), associated respectively with each of the users and ensuring magnetic protection and differential protection of said user. 2. - An assembly according to claim 1, characterized in that the energy management means comprise three separate energy metering means respectively associated with each current sensor. 3. - assembly according to one of claims 1 and 2, characterized in that the electrical network is a single-phase network comprising the neutral conductor (N) and a single primary phase conductor (P), the primary phase conductor being connected to the three secondary phase conductors (P1, P2, P3) upstream of the protection means. 4. - assembly according to claim 3, characterized in that 4 users are connected to each secondary phase conductor, each individual circuit breaker being a 2.5A circuit breaker and the four-pole circuit breaker being a 30A circuit breaker, limited to 10A by phase. 5. - An assembly according to claim 3, characterized in that 8 users are connected to each secondary phase conductor, each individual circuit breaker being a 2.5A circuit breaker and the four-pole circuit breaker being a 60A circuit breaker, limited to 20A by phase.  6. - Assembly, according to one of claims 1 and 2, characterized in that the electrical network is a three-phase network comprising the neutral conductor and three primary phase conductors respectively connected to the three secondary phase conductors. 7. - An assembly according to claim 6, characterized in that 4 users are connected to each secondary phase conductor, each individual circuit breaker being a 2.5A circuit breaker and the four-pole circuit breaker being a 10A circuit breaker 8. - Assembly according to claim 6, characterized in that 8 users are connected to each secondary phase conductor, each individual circuit breaker being a 2.5A circuit breaker and the four-pole circuit breaker being a 20A circuit breaker 9. - assembly according to claim 6, characterized in that 12 users are connected to each secondary phase conductor, each individual circuit breaker being a 2.5A circuit breaker and the four-pole circuit breaker being a 30A 10 circuit breaker. - Assembly according to claim 6, characterized in that 24 users are connected to each secondary phase conductor, each individual circuit breaker being a 2.5A circuit breaker and the four-pole circuit breaker being a 60A circuit breaker