SU491169A1 - High Speed Current Relay - Google Patents

Description

The relay is intended to signal single-phase earth faults in electrical systems with a voltage of 3-35 kV with insulated neutral or in compensated networks.

The relay is triggered by transient currents that occur when the insulation is damaged.

A relay is known that uses the transient currents of the pr.i circuit to earth.

This device uses a current relay of the ET series, which is directly affected by the transient current. Therefore, the moment developed by the mobile system depends on the magnitude and frequency of this current.

Moving the closing point along the line simultaneously causes a change in the magnitude of the current, its frequency, and hence the inductive resistance of the relay.

The higher frequency of the earth fault current in the transition process, the period of which is less than the period of free oscillations of the moving system of the relay, causes the deviation of the moving system in proportion to the area of the acting pulse, i.e. it depends not only on the amplitude, but also on the pulse shape and duration.

The inconsistency of the frequency forces to allow currents through the relay winding, in several

times the accepted actuating currents. As a result, the relay current is so large that the impact of the fixed contacts when the relay is triggered causes contact damage and protection failures.

In addition, this relay can only be used for connections that are significantly extended from power supplies where the transient current frequency is low.

The purpose of the invention is to ensure the dependence of the operating time of the relay only on the magnitude of the transition current at a constant, pre-selected, optimal frequency of 30-40 Hz.

This goal is achieved by the fact that the relay is equipped with an oscillating circuit in the form of a group of capacitors and an actuator. The oscillatory circuit is a transient current frequency converter 200-10000 Hz to the operating current frequency of the executive electromagnetic relay, which is a constant, pre-selected value that ensures reliable operation of the executive body. The dependence of the operating time of the relay on only one parameter greatly simplifies the calculation and selection of settings, setting the relay, improves reliability and simplifies operation.

Relay circuit is shown in the drawing.

The relay consists of a resistor /, diodes 2 and 3, an adjustment unit in the form of a relay 4, capacitors 5 and 6.

The relay with its input contacts 7 and 8 is connected directly to the secondary winding of the CTPS zero sequence current transformer 9. Resistor 1 is used to adjust the voltage (current) response, as well as to limit the overvoltage on the circuit after charging the capacitors 5 and 5, since TTP 9 is constantly resilient.

The relay works as follows.

At the time of the earth fault, an alternating current voltage with a frequency of 200-10000 Hz appears on the secondary winding of the TTPC. sB during the first quarter of the first half cycle, the capacitor 5 is charged, and during the first quarter of the second half period, the capacitor 6 is charged. The charged capacitors 5 n 5 are discharged to the coil of the electromagnetic relay 4, which has a high inductance.

The process of discharging capacitors 5 m 6 to the winding of relay 4 is oscillatory in nature. Here, the natural frequency is here chosen such that relay 4 reliably operates. For electromagnetic relays, this frequency is 30-40 Hz. The use of capacitors 5 and 5 as a storage element of the current energy of the transient process ensures the operation of relay 4 in a wide frequency range of the transient process.

Subject invention

A high-speed current relay for protection of single-phase earth faults in electrical systems with insulated neutral and in compensated networks, contains an actuator, such as an electromagnetic relay, characterized in that it is equipped with an oscillatory circuit in order to enhance the functionality of the relay in the form of two capacitors and the specified actuator, so that the oscillating circuit is a transient current transducer for short circuit on the ground to the frequency of the operating current of the specified executive body, which is a constant value selected in advance, ensuring reliable operation of the executive body, determined by the parameters of the oscillating circuit.