SU1695441A1 - Device for protection against leakage of current in a c network with solidly grounded neutral - Google Patents

Abstract

The invention relates to electrical engineering and is intended for relay protection against earth faults. The aim of the invention is to simplify with simultaneous j. increase reliability. When the knife switch 10 is turned on, the executive body 2 is energized. When the button 7 is pressed, a single-phase voltage is applied to the monitored section. If the insulation resistance value of this section is at an acceptable level, the single-phase leakage current is less than the actuator actuation current 2. The control circuit is prepared for the start of the electrical receiver: contacts 3 are closed, the magnetic starter coil 8 is powered, its contacts 12 are closed and the electrical receiver 5 is connected to the power network. If the insulation resistance of the monitored section is less than the permissible value, then a single-phase leakage current flows through the transformer 1 control circuit, enough to actuate the actuator 2, contacts 3 of which open and block the motor start by pressing button 7. 1 slug. with

Description

The invention relates to electrical engineering and can be applied in industrial networks of three-phase and single-phase current.

The aim of the invention is to simplify while increasing reliability.

The drawing shows a diagram of the proposed device.

The device comprises a zero-sequence current transformer 1, an actuator 2 with opening contacts 3, an additional section 1a - 3A, introduced with a current-limiting resistor 4, to form an insulation control circuit.

The control circuit of the current collector 5 contains the opening contacts 3, the Stop button 6, the Start button ”7, the coil 8 of the magnetic starter with block contacts 9.

In addition, the device contains a switch 10.

The monitored section of the network includes an electric receiver 5 and a segment of the power network 11, power contacts 12 of the magnetic starter.

The protective function of the device during switching on.

When you turn on the switch 10 to the Executive body 2 is supplied with power. When button 7 is pressed, a single-phase voltage is applied to the monitored section.

If the insulation resistance of this section is at an acceptable level, the leakage current is less than the actuation current of the actuator 2. The control circuit is prepared to start the power receiver: contacts 3 are closed, the coil 8 of the magnetic starter is powered, its contacts 12 are closed and the power receiver 5 is connected to the power network.

If the insulation resistance of the monitored section is less than the permissible value, then a leakage current flowing through the transformer 1 flows enough to actuate the actuator 2, the contacts 3 of which open and block the start of the electric motor when button 7 is pressed.

Protective function during the operation of the current collector.

If the insulation resistance of the monitored section drops below an acceptable level, a leakage current flows along the insulation monitoring circuit, actuator 2 activates, opening contact 3 and disconnecting the coil 8 of contactor 12 and, therefore, the current collector.

At the same time, the proposed device allows the measurement of insulation resistance by determining the current through 4 or voltage drop across it. This can be used to measure the insulation resistance in power and lighting networks without turning off the power consumers, which has to be done when measuring the resistance with a megger.

Thus, the invention allows, performing all the functions of the prototype, to simplify the protection device while improving reliability.

Claims (1)

Claim A device for protection against current leakage in an alternating current main with a grounded neutral containing a contactor, a zero-sequence current transformer, to the secondary winding of which an actuator is connected, the opening contact of which is connected in series to the power supply circuit of the contactor coil, which includes a series button Start, shunted by the contactor of the contactor, and having conclusions for connection between the conductor of one of the phases of the network and the neutral conductor from the source mains supply network, characterized in that, in order to simplify while improving reliability, the zero sequence current transformer is designed to be installed after the power contacts of the contactor on the side of the power receiver and the current-limiting resistor is inserted again, one output of which is connected between the Start button and the opening contact of the actuator, the second the output of which is designed to connect to the phase conductor of the network between the power contact of the contactor of the phase of connecting the power circuit of the coil of the contactor and a zero sequence current transformer.