FR3067470B1 - CURRENT MEASUREMENT IN A MULTIPHASE ELECTRICAL NETWORK - Google Patents

Abstract

Device for measuring current flowing in an electrical network comprising a plurality of phases, characterized in that it comprises current measurement magnetic sensors (1, 2, 3) respectively intended for each phase of the electrical network, each magnetic sensor being housed in a separate housing, an electronic circuit (5) connected to the magnetic sensors and having a shunt resistor (R1, R2, R3) respectively for each phase of the electrical network and an overall shunt resistor (RG) for all phases of the electrical network , each magnetic sensor (1, 2, 3) being able to supply a measurement signal to the electronic circuit (5), the electronic circuit being able to produce phase voltage signals (V1, V2, V3) respectively representative of the current circulating in each phase and a global voltage signal (VG) representative of the vector sum of the currents flowing in the phases of the electrical network.

Description

CURRENT MEASUREMENT IN A MULTIPHASE ELECTRICAL NETWORK

DESCRIPTION

TECHNICAL AREA

The present invention relates to a device for measuring current flowing in an electrical network comprising several phases. It relates more particularly to low power current transformer type magnetic sensors, said LPCT according to the English "Low Power Current Transformer". The invention is equally applicable to low, medium or high voltage electrical networks.

STATE OF THE PRIOR ART

A current measuring device using magnetic sensors of low power current transformer type, called LPCT, and intended for a multi-phase network conventionally comprises a sensor per phase. To verify whether or not there is a ground fault, it is necessary to add a summation of the current measurements per phase and the sensors of the three phases must therefore be connected. For this, the sensors are integrated in a single housing adapted to the specific configuration of a relevant electrical equipment, and the distances between the sensors are fixed. Each apparatus therefore has its own housing, which lacks flexibility with respect to the variety of equipment.

DISCLOSURE OF THE INVENTION The invention aims to solve the problems of the prior art by providing a device for measuring current flowing in an electrical network comprising a plurality of phases, characterized in that it comprises

Magnetic current measuring sensors respectively for each phase of the electrical network, each magnetic sensor being housed in a separate housing,

An electronic circuit connected to the magnetic sensors and comprising a shunt resistor respectively for each phase of the electrical network and an overall shunt resistor for all the phases of the electrical network, each magnetic sensor being able to supply a measurement signal to the electronic circuit, the electronic circuit being able to produce phase voltage signals respectively representative of the current flowing in each phase and a global voltage signal representative of the vector sum of the currents flowing in the phases of the electrical network.

Thanks to the invention, the measuring device can be adapted to the distance between the conductors of the different phases of the electrical network, which provides greater flexibility. These conductors may be rigid cables, bars or bushings.

According to a preferred characteristic, the device for measuring current flowing in an electrical network comprising a plurality of phases comprises at least one element for connecting the housings of the magnetic sensors to each other, the at least one connecting element being able to connect the sensor housings. magnetic signals according to a variable distance between them. The connecting element makes it possible to secure the housing between them.

According to a preferred characteristic, the electronic circuit is integrated in the housing of one of the magnetic sensors.

According to an alternative preferred characteristic, the electronic circuit is integrated in a specific housing.

The configuration of the measuring device is thus adaptable to the specific needs of each electrical network, particularly in terms of dimensional constraints.

BRIEF DESCRIPTION OF THE DRAWINGS Other characteristics and advantages will appear on reading the following description of a preferred embodiment, given by way of non-limiting example, described with reference to the figures in which:

FIG. 1 represents the device for measuring current flowing in an electrical network comprising several phases, according to one embodiment of the invention,

FIGS. 2a, 2b and 2c show the current measuring device circulating in an electrical network comprising several phases according to different assembly configurations, according to one embodiment of the invention.

DETAILED PRESENTATION OF PARTICULAR EMBODIMENTS

According to a preferred embodiment, shown in Figure 1, the current measuring device flowing in a multiphase electrical network comprises a magnetic sensor 1, 2 and 3 current measurement for each phase. The electrical network is for example a medium voltage network, and it is three-phase in the embodiment shown. The drivers of the electricity network are not represented.

Each magnetic sensor is a low power current transformer, called LPCT according to the English "Low Power Current Transformer". The magnetic sensors 1, 2 and 3 are each arranged in a respective housing.

According to a first embodiment shown in FIGS. 2a, 2b and 2c, this housing is a housing, for example made of material of the PAT or PA66 type loaded with glass fibers. According to a second embodiment, this housing is simply an envelope surrounding the sensor. This envelope is achievable by overmoulding epoxy material or polyurethane.

The housing ensures a good level of electrical insulation that depends on the voltage range, as well as the mechanical strength of the sensors.

All the magnetic sensors are connected to an electronic circuit 5 which has shunt resistors R1, R2, R3 and RG. Each of these resistors makes it possible to supply a voltage signal representative of the current flowing in the resistor under consideration. The electronic circuit is for example made in the form of a Printed Circuit Board (PCB). Each magnetic sensor 1, 2 and 3 has a first output connected to a first terminal of a respective shunt resistor R1, R2 and R3.

The shunt resistors R1, R2 and R3 have a second common terminal connected to a first terminal of an overall shunt resistor RG.

Each magnetic sensor 1, 2 and 3 has a second output connected to a second terminal of the overall shunt resistor RG.

The point of connection between the shunt resistors R1, R2 and R3 and the overall shunt resistor RG is an output of the electronic circuit and is connected to a reference potential.

The first output of each magnetic sensor 1, 2 and 3 forms a respective output of the electronic circuit. The voltage V1, V2 and V3 between the first output of each magnetic sensor 1, 2 and 3 and the reference potential is representative of the current flowing respectively in each phase of the electrical network.

The second terminal of the overall shunt resistor RG is an output of the electronic circuit. The voltage VG between the second terminal of the overall shunt resistor RG and the reference potential is representative of the vector sum of the currents flowing in the phases of the electrical network. This signal makes it possible to check whether or not there is an earth fault.

The electronic circuit 5 thus provides measurement signals VI, V2 and V3 representative of the currents in the different phases of the electrical network and a measurement signal VG representative of the vector sum of these currents. These four output signals VI, V2, V3 and VG are then provided for analysis to a control unit, not shown, of the protection relay type, for example.

The electronic circuit 5 is integrated in a housing which, according to a first variant, is the housing of one of the three magnetic sensors, which makes it possible to economize on a proper housing dedicated to the electronic circuit. In this case, the housing of the sensor also integrating the electronic circuit is connected to the other two slots to route the signals from these sensors to the electronic circuit and is connected to the control unit to carry the four measurement signals.

In a second variant, the housing of the electronic circuit 5 may also be a specific housing, for example when the sensor housings are too small or when the sensor housing is an overmolded epoxy or polyurethane envelope. In this case, the housing of the electronic circuit 5 is connected to the three sensors to route the signals emitted by the sensors and is connected to the control unit to carry the four measurement signals.

The connections and interconnections between the magnetic sensors and the electronic circuit 5 are made by flexible shielded cables. The shielding makes it possible to respect electromagnetic compatibility standards EMC (according to the English Electromagnetic Compatibility).

Figures 2a, 2b and 2c show different possibilities for assembling the housings of the magnetic sensors. These housings are housings B1, B2 and B3 in the embodiment shown. As mentioned above, the magnetic sensors 1, 2 and 3 are each housed in a respective housing. The shape of the housings B1, B2 and B2 is identical and globally in the form of a ring. They thus each comprise a central opening for the passage of a conductor of a phase of the electrical network (not shown). Housings Bl, B2 and B3 are adapted to be assembled with each other, according to different configurations.

Each housing has cylindrical holes through T, here four in number, arranged square substantially on the periphery of the housing. The measuring device also comprises two intermediate connecting elements L1 and L2 which are generally elongate in shape and comprise a through hole also of oblong shape. Alternatively, this hole is replaced by a succession of cylindrical holes aligned next to each other.

The holes of the housings and connecting elements are intended to receive screws or pins not shown.

According to Figure 2a, the housings are assembled in the same orientation and shifted. More specifically, the housings are all substantially perpendicular to the same direction which is that of the phase conductors (not shown). A B2 housing in the central position is offset from the other two boxes B1 and B3 disposed on either side of the first.

In the assembly of FIG. 2a, it can be seen that the housings of the sensors can advantageously partially overlap, which makes it possible to use them when the network conductors are brought closer together, that is to say when the spacing between the conductors is not enough to install the boxes next to each other.

According to Figure 2b, the housings are also assembled in the same orientation and shifted, but the housings are further apart from each other than in the previous figure.

According to Figure 2c, the housings are also assembled in the same orientation, but are aligned in the same plane.

In all cases, the connecting elements L1 and L2 are in a plane perpendicular to the direction of the conductors of the phases. In Figures 2a and 2b, the connecting elements are placed between the housing in the central position and the other two housings. In Figure 2c, the connecting elements are placed against the housings. In all cases, the peripheral holes of the housings and the holes of the connecting elements are in facing relation, so that screws (not shown) can be inserted into the peripheral holes of the housings and the holes of the connecting elements. to stiffen the assembly of the housings. The assembly of the housings is thus easily adaptable to different configurations and different distances between the conductors of the electrical network.

Claims (4)

1. Device for measuring current flowing in an electrical network comprising a plurality of phases, characterized in that it comprises current measurement magnetic sensors (1, 2, 3) respectively intended for each phase of the electrical network, each magnetic sensor being housed in a separate housing (B1, B2, B3), an electronic circuit (5) connected to the magnetic sensors and having a shunt resistor (R1, R2, R3) respectively for each phase of the electrical network and a global shunt resistor ( RG) for all the phases of the electrical network, each magnetic sensor (1, 2, 3) being able to supply a measurement signal to the electronic circuit (5), the electronic circuit being able to produce phase voltage signals (VI , V2, V3) respectively representative of the current flowing in each phase and a global voltage signal (VG) representative of the vector sum of the currents flowing in the phases of the network electric. 2. Device for measuring current flowing in a multi-phase electrical network according to claim 1, characterized in that it comprises at least one element (L1, L2) for connecting the housings (B1, B2, B3) of the magnetic sensors. between them, the at least one connecting element being able to connect the housings of the magnetic sensors according to a variable distance between them. 3. Current measuring device circulating in a multi-phase electrical network according to claim 1 or 2, characterized in that the electronic circuit (5) is integrated in the housing of one of the magnetic sensors. 4. Device for measuring current flowing in a multi-phase electrical network according to claim 1 or 2, characterized in that the electronic circuit (5) is integrated in a specific housing.