RO116852B1 - Protective device for low voltage power installations - Google Patents

Abstract

The invention relates to a device for the protection of the low voltage power installations against shortcircuit, overload, residual differential current and also against overvoltage of environmental origin. According to the invention, the protective device comprises a torroidal measuring transformer (Tmas) whose secondary winding is linked to the terminals (a and b) of an electronic control circuit (A) which supplies through the terminals (c and d) the coil (4) of an electromanget which switches off the disjunctor (5), a varistor (v) being coupled with the phase input terminal (F1) and the neutral terminal (N2) of the supply network employed by the consumers, the device being tested at differential current by means of a test button (1) and a test resistor (R1) connected with the phase input terminal (F1) and the neutral terminal (N2) of the supply network employed by the consumers.

Description

The invention relates to a device for the protection of low voltage electrical installations at short circuit, overload, residual differential current, overvoltage, as well as at overvoltages of atmospheric origin.

A short-circuit and overload protection device known in patent application FR 2399729 is known, which is provided with a system of levers for manual arming / disarming, which can be actuated automatically when a short circuit is displayed by an electromagnetic relay or at the occurrence of an overload by a thermal relay.

Also known is an electronic overvoltage protection relay of atmospheric origin, disclosed in patent JP 8279331, which is provided with an overvoltage sensing circuit, coupled with an electronic circuit for actuating a thyristor-type interrupting element. allows consumers to be protected against excess voltage of atmospheric origin.

There is also known a differential current protection device, presented in patent application EP 0977234, which is provided with a toroidal transformer, which actuates, by means of an electromagnetic control coil, an electromagnetic control relay with a magnetic field remaining, at the occurrence a residual differential current in the circuit of the low voltage electrical installation.

These devices have the disadvantage that they can provide only one type of protection, either short circuit and overload protection, or differential current or overvoltage.

The device, according to the invention, removes the disadvantages shown above, in that it has a toroidal measuring transformer, provided with some primary windings connected to the phase and to the null, the secondary winding of the toroidal measuring transformer is connected to some terminals of a circuit. electronic control that supplies through a coil terminals of an electromagnet to disconnect the circuit breaker, a varistor coupled to the phase input and output terminals of the consumer power supply network, testing the operation of the device at the differential current being performed with the aid of a button test and a resistor connected to the phase input and output terminals of the consumer power supply network.

By using the device, according to the invention, a complex protection of the electrical system is achieved at short circuit, overload, residual differential current, overvoltages, as well as protection at overvoltages of atmospheric origin.

An example of embodiment of the invention is given below, in connection with FIG. 1 and 2, representing:

FIG. 1, the general scheme of the device according to the invention;

- fig. 2, the principle diagram of the electronic control circuit shown in fig. 1.

The device, according to the invention, is provided with a t _m8 toroidal transformer of measurement measuring the residual differential current, provided with some primary windings 1 and 2 connected to some terminals F _n of phase and l \ _{n n} of the input of the power network. to which consumers connect.

As the toroidal transformer T _MAA is also provided with a secondary winding 3 is connected to the terminals a and b of the input of an electronic control circuit.

RO 116852 Bl

The electronic control circuit A controls a coil 4 of an electromagnet 45 which operates a circuit breaker 5 provided with some IC contacts, and Ka. which interrupt the supply of the F ₂ phase and N ₂ terminals of the output node of the network to which the consumers are connected.

A varistor V is connected between the terminal F, the phase input and the zero output terminal, which limits atmospheric surges, as well as a test circuit 50 of the device comprising a test button T and a test resistor R _t , which simulates the residual differential current.

The electronic control circuit A is supplied through terminals c and d, through coil 4 of the electromagnet and a resistive divider formed by resistors R, and R ₂ and a rectifier diode. 55

Some diodes D ₁ and D ₂ Zenner perform the stabilization of the supply voltage of an operational IC amplifier, its filtering being realized by means of a capacitor C ₁ .

The non-inverting input of the operational IC amplifier is connected to the output of a resistive divider consisting of a fixed R ₃ resistor and a variable R ₄ resistor, which allows 6o to adjust the comparison threshold and thus change the value of the differential current at which the protection is actuated.

In order to inhibit the protection circuit in the event of disturbing signals and to reduce the unexpected actions, two resistors R ₆ , R, and some capacitors Cg, G, and (½. 65) are provided in the input circuit of the operational IC amplifier.

The protection of the operational IC amplifier against overvoltages is achieved by means of diodes D ₃ and D _4. A resistor R _s polarizes in the DC the secondary circuit of the measuring transformer T _ «- and the capacitor C ₄ ensures the frequency compensation of the operational IC amplifier.

The output of the operational IC amplifier is connected to the gate of a thyristor T _y 70 by means of a diode D _s , a diode D ₆ Zenner and a resistor R ₈ .

Timing and protection at accidental drive of thyristor T _y is achieved by tying in the gate of thyristor T _y a capacitor C ₅ and a resistor R ₉ . The sensing of the overvoltage in the network is realized by means of diodes D ₇ , D ₈ , D _g Zenner and diode D ₁₀ , coupled to the gate of thyristor T _y . Diode D ₁₀ has at the same time 75 the role of voltage limitation applied on the thyristor gate T _y through the R _e resistor, from the output of the operational IC amplifier.

claims

Claims (3)

1. Device for the protection of low voltage electrical installations that has a toroidal transformer of measure provided with some primary windings connected to the phase and the null of the network and to the contact of a circuit breaker, as well as a secondary winding, characterized in that the winding (3), secondary , of the toroidal measuring transformer (T _mee ) is connected to terminals (a and b) of an electronic control circuit (A) 85 which feeds through terminals (c and d) of a coil (4) of a disconnecting electromagnet of the circuit-breaker (5), a varistor (V) coupled to the phase input terminal (F ₁ ) and the supply network null terminal (N ₂ ) to which it is connected VRO 116852 Consumers, testing the operation of the device at differential current, being performed with the aid of a test button (1) and a resistor (test RJ connected to the terminal (F ₁ ) of phase input and to the terminal (l \ l ₂ ) to cancel the supply network to which the consumers are connected. Device according to claim 1, characterized in that the electronic control circuit (A) is provided with a resistive voltage divider consisting of resistors (R, and y and diodes (Di and D ₂ ) Zenner, as well as a capacitor (filter CJ, a resistive voltage divider made of resistors (R ₃ and R ₄ ) coupled to an operational amplifier (IC), for inhibition at disturbing signals are provided resistors (Re and R ₇ ) as well as some capacitors (C ₂ , C ₃ and C ₆ ), operational amplifier (IC) protection against overvoltages is achieved by means of diodes (D ₃ and D ₄ ), the output of the operational amplifier (IC) is coupled by means of diodes (D ₅ and D ₆ ] and a resistor (Rg) at the gate of a thyristor (T _y ) which is timed and protected against accidental actuation by means of a capacitor (C ₅ ) and a resistor (R ₉ ), for sensing surge voltage r of the network being provided with diodes (D ₇ , D ₈ and Dg) Zenner and a diode (D ₁₀ ), which are coupled to the thyristor gate (T _y ). Device according to claims 1 and 2, characterized in that the resistor (RJ of the voltage divider (Ra and Ra) connected to the inverter input of the operational amplifier (IC) has a variable resistance that allows the comparison threshold to be adjusted.