METHOD FOR DETECTING THE AVOID OF A NEUTRAL CONDUCTED IN BEFORE A COUNTER AND COUNTER, COMPUTER PROGRAM AND PROGRAM SUPPORT FOR IMPLEMENTING THIS METHOD

Description

[0001] The present invention relates to the measurement of energy consumption of an electrical installation connected to a polyphase distribution network. STATE OF THE ART

[0002] It is known to connect each consuming electrical installation to several phases of a polyphase distribution network via a meter arranged to measure the total amount of energy consumed by the electrical installation.

[0003] In a polyphase network, one of the most serious problems that can occur is a neutral wire break upstream of the meter. Indeed, in such a case, imbalances between phases generate significant voltages that can damage electrical installation equipment.

[0004] In addition, meters equipped with power line communication (PLC) capabilities are now available, enabling data exchange between meters and data concentration units to facilitate metering management. Data is transmitted by the meter by injecting data signals onto one of the phases of the distribution network. The transmitted data includes information relating to the installation's consumption. The use of these data signals to send alerts for anomalies detectable by the meter has been considered.

[0005] It would therefore be beneficial if meters could detect a neutral break, either to alert the user or to alert the distribution network operator. SUBJECT OF THE INVENTION

[0006] One aim of the invention is to provide a means to detect a neutral break in an electrical distribution network from a meter connected to the distribution network and to a consuming installation. BRIEF SUMMARY OF THE INVENTION

[0007] For this purpose, according to the invention, a method for detecting the absence of a neutral is provided according to claim 1.

[0008] When the network has its neutral correctly connected, the voltage ratio is equal to 1. Conversely, this ratio becomes greater than 1 when the neutral is missing and the three impedances downstream of the meter are not balanced. It is therefore easy to detect the absence of a neutral using the method of the invention.

[0009] The invention also relates to an electric meter for implementing this process.

[0010] The invention further relates to a computer program product and a computer program support for implementing this method.

[0011] Other features and advantages of the invention will become apparent from the following description of particular, non-limiting embodiments of the invention. BRIEF DESCRIPTION OF THE FIGURES

[0012] Reference will be made to the attached drawings, including: there figure 1 is a schematic view of a meter according to the invention, the figure 2 is a diagram illustrating the process of the invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] With reference to the figure 1The electricity meter according to the invention, generally designated as 1, is arranged to connect an electrical distribution network 100 to an electrical installation 200 that consumes electricity. The electrical distribution network 100 is a three-phase network comprising three phases P1, P2, P3 and a neutral N: such a network is known in itself and will not be described in further detail here. The electrical installation 200 comprises three phases P'1, P'2, P'3 and a neutral N': such an installation is known in itself and will not be described in further detail here.

[0014] Counter 1 includes: Voltage measurement means between phases P1, P2, P3, neutral N, and a reference potential of meter 1; current measurement means on each phase P'1, P'2, P'3; a disconnection device 2 for meter 1 from the network 100; a control unit connected to the various measurement means and the disconnection device 2, comprising a processor connected to a memory containing a program executable by the processor and arranged to implement the method of the invention for detecting the absence of a neutral in the distribution network 100 upstream of meter 1. The program storage means may be a memory permanently mounted in the control unit or a removable data storage medium (e.g., a USB memory device). The computer program may be stored in the memory at the factory or downloaded from a storage medium temporarily connected to the control unit.

[0015] The control unit of meter 1 is further arranged here to transmit data signals on one of the phases of network 100 (PLC signal injection) to transmit consumption data or alerts.

[0016] In operation, in addition to the classic tasks of energy metering, the method according to the invention provides for periodically measuring the voltages V 1 , V 2 , V 3 between the phases P 1 , P 2 , P 3 and the neutral N and calculating the impedances Z 1 , Z 2 , Z 3 of the phases downstream of the meter (step 21).

[0017] The impedances Z i are equal to (Z i -Z Li ) / (Z i +Z Li ) for i varying from 1 to 3, where Z' i are the internal impedances of counter 1 and Z Li are the impedances on each phase P' i.

[0018] This allows us to calculate the voltage V'N which results from the following equality: V → 1 Z 1 + V → 2 Z 2 + V → 3 Z 3 = V → ′ N 1 Z 1 + 1 Z 2 + 1 Z 3 .

[0019] This also allows, in a way known in itself, to calculate the effective voltages V' 1 , V' 2 , V' 3 across the terminals of each of the loads of the consuming installation 200.

[0020] Finally, a threshold β is periodically calculated, equal to the ratio between the highest impedance Zi and the lowest impedance Zi. This threshold is stored in the control unit of counter 1 for later use.

[0021] The process continues with step 22 of comparing the impedances Z1, Z2, Z3 with each other.

[0022] When the impedances Z1, Z2, Z3 are equal to each other, the control unit issues an alert indicating that neutral absence detection is impossible (step 23).

[0023] When the impedances Z1, Z2, Z3 are unequal with each other, the absence of neutral detection is continued.

[0024] A ratio α is then calculated between the highest of the voltages V'1, V'2, V'3 and the lowest of the voltages V'1, V'2, V'3 (step 24)

[0025] When this ratio α is greater than 1, the control unit issues an alert representing a lack of neutral (step 26).

[0026] Preferably, the process also includes step 28 of activating the disconnect device 2 of meter 1 if a neutral absence is detected. More specifically, the disconnect device 2 is activated only if the voltage ratio α is greater than the threshold β. The threshold value β used for comparison with the voltage ratio α is the last threshold value β determined before the neutral absence was detected.

[0027] In the event of a neutral break, the voltage V'N becomes zero and generates an imbalance between the voltages V'1, V'2, V'3: the voltage ratio α becomes greater than 1. It is considered that, when the ratio α is less than the threshold β, the risk of degradation of the installation 200 is low or even non-existent: it is therefore not necessary to isolate the installation 200 from the network 100.

[0028] Of course, the invention is not limited to the embodiments described but encompasses any variant falling within the scope of the invention as defined by the claims.

[0029] In particular, the invention applies to any electrical distribution network comprising at least two phases and a neutral.

[0030] The process might not include an alert phase as long as the voltage ratio α remains below the threshold β.

[0031] It is possible to have a threshold that is not modified dynamically but fixed once and for all.

Claims

1. Method for detecting an absence of neutral in a polyphase network from a counter connecting a consumer installation to the distribution network, the method comprising: - determine the impedances of the phases downstream of the counter, - when the impedances are equal to each other, issue an alert indicating that the absence of neutral is impossible to detect, - when the impedances are unequal to each other, determine the effective voltages between the phases downstream of the counter and a reference potential of the counter, - calculate a ratio between the highest of these voltages and the lowest of these voltages, - when this ratio is greater than 1, issue an alert representative of an absence of neutral and actuate a device for disconnecting the counter in the event of detection of an absence of neutral if the voltage ratio is greater than a threshold value greater than 1 and equal to a ratio between the highest of the impedances of the phases and the lowest of the impedances of the phases.

2. Method according to claim 1, wherein the threshold value is determined periodically and the threshold value used for the comparison with the voltage ratio is the last threshold value determined before the detection of an absence of neutral.

3. Counter for a polyphase network, comprising: - means for measuring the voltage between the phases and a reference potential of the counter, - a control unit connected to the voltage measuring means and programmed to implement the method according to any one of the preceding claims.

4. Computer program product for carrying out the method according to any one of claims 1 and 2.

5. Computer storage means containing a computer program arranged for carrying out the method according to any one of claims 1 and 2.