SU1432420A1 - Device for checking insulation resistance - Google Patents

Abstract

The search is intended to measure the insulation resistance in the retard DC current under voltage, and to protect it against earth faults. The device for monitoring the insulation resistance contains keys 1, 2 ,, shunt resistor 3 connected to ground, voltage measuring transducers 4, 5, switch 6, filtering unit 7 to eliminate the influence of the variable component of the voltage of the monitored network on the measurement accuracy a calculation unit 8, the result of which is displayed on the indicator 9 and on the output unit 10, where the comparison is made, of this value with the setpoint and the delay for operation for use of the device in a chain x protection relay. The device has increased control accuracy of the insulation resistance and enhanced functionality due to the possibility of protecting the excitation circuits of the synchronous machine. 1 il. with S cl

Description

eight

00 Kd

This invention relates to electrical engineering and is intended to / C1 measure insulation resistance in direct current networks, is under voltage, and are subject to ground faults.

The purpose of the invention is to improve the accuracy of control of the insulation resistance and to expand the functional capabilities by providing the possibility of protecting the excitation circuits of a synchronous machine.

The drawing shows a block diagram of the device.

The device contains the first 1 and second 2 switches, the shunt resistor 3, the measuring transducers 4 and 5 of the voltage, the switch 6, the filtering unit 7, the computing unit 8, the indicator 9, the output unit 10, the control unit 11 and the equivalent resistances 12 and 13 poles of a controlled network.

The first pins of the first 1 and second 2 keys are centered with the first output of the shunt resistor 3, the second output of which is connected to ground, the second outputs of the keys 1 and 2 are connected to the corresponding poles of the monitored network and the inputs of the first 6 and second 5 voltage transducers respectively The outputs of which are connected respectively to the first and second terminals of the switch 6, the third output of which is connected via the filtering unit 7 to the input of the calculation unit 8, and the output of the latter is connected to the inputs of the indicator 9 and the output About unit 10, the first, second, third and fifth outputs of control unit 11 are connected respectively to the control inputs of the first 1 and second 2 keys, calculation block 8 and the switch, and the fourth output - to another control input of calculation block 8 control input of the output unit 10.

The device works as follows.

With open keys 1 and 2, the distribution of the potentials of the poles of the network with respect to earth is determined by the ratio of the equivalent resistances 12, 13 of the insulation of the poles R1, R2, i.e.

 - UcRj R1 + R2

 . R + R2

1 de Uj. - mains voltage at the moment of

measure

When one of the switches is closed, the potentials of the poles are redistributed, and the potential of the pole with a shunt-resistor 3 II, B, which is connected to it, is determined by the formulas

„Us1K1 1 Ksh) 3 - (R1 (I RJ + kg

П- - yciR2 (,)

  R + (R2 × R)

If the voltage Uj is the same at the time of measurement of U and and |, i.e. U U (3 const, then the equivalent insulation resistance of the network R eq R1 (/ R2 is determined by the ratio

 yJ)

.- R,

(one)

25 DA AQ -.d

35

50

55

To eliminate the influence of the variable component of the monitored network voltage on the measurement accuracy, filtering unit 7 is used. In block 8, the calculation is performed using the relation (1) using the Ut and Ut values stored in one cycle, the result of the calculations is displayed on the indicator 9 and on the input of the output block 10, where this value is compared with the setpoint and the response delay for using the device in the relay protection circuit.

Claims (1)

Invention Formula A device for controlling the insulation resistance containing a shunt resistor, one output of which is connected to ground and the other to the first terminals of the first and second keys, the BTopbie whose terminals are connected to the corresponding 1 pole of the monitored network, the first measuring voltage converter, computing unit, output which is connected to the input of the indicator, and a control unit, the first, second and third outputs of which are connected respectively to the control inputs of the first and second keys and the first input of the calculation unit, about This is so that, in order to increase accuracy and enhance functionality by providing protection to the excitation circuits of a synchronous machine, a second voltage measuring converter, a switch, a filtering unit and an output unit are introduced, and the inputs of the first and second voltage measuring transducers are connected to controlled poles, and the outputs, respectively, with the first and second outputs of the switch, the third output of which is connected through the filtering unit to the input of the computing unit, the output of which is connected to the input of the output unit, and the second input of the control is connected to the control input of the output unit and the fourth output control unit, the fifth output of which is connected to the control input of the switch.