SU659992A1 - Arrangement for measuring insulation resistance in networks with deadearthed neutral wire - Google Patents

Description

one

The invention relates to electrical measuring equipment and can be used to measure and control the insulation isolation with respect to the earth in networks with a neutral Mv.

The closest to the technical essence of the invention is a device for measuring the insulation resistance in networks with a solidly earthed neutral, containing a voltage generator, a grounding conductor, a power transformer of a controlled network, a barrier filter, connection capacitors and an actuator 1. The disadvantage of this device is low measurement accuracy with high leakage resistance values.

The purpose of the invention is to improve the measurement accuracy for large values of leakage co-forces.

This is achieved by introducing current transformers, an additional indicator with an actuator, a voltage transformer, and a switching unit into a known device containing a voltage generator, a grounding conductor, a main indicator with an actuator, a power transformer of the monitored network. In this case, the output of the voltage generator is shunted by the primary winding of the voltage transformer, the findings of the first

The secondary winding of which is connected to the output of the switching unit, and the terminals of the second secondary winding, respectively, to the neutral of the power transformer of the controlled network and the zero bus to which the grounding conductor is connected. The outputs of the main and additional indicators with executive elements are shunted by the windings of the corresponding current transformers. The winding of one of the current transformers is magnetically connected with the neutral of the power transformer of the monitored network, and the winding of the D ptoy current transformer --- with (|) the basics of the monitored network.

On the imp represented functional diagram of the device.

The device contains a generator 1, a grounding 2, a main indicator with an equivalent element 3, a power transformer 4 of a controlled network, current transformers 5 and 6, an additional indicator with an executive element 7, a switching unit 8, a transformer

9 iair marriages the contents of the primary winding 10 and secondary windings l-l, 12 and fuses 13.

Works mouth yustbo s.uduyupeii way.

With the help of generator 1 voltage

through the voltage transformer 9, a non-industrial frequency current is applied to the controlled network 14. When the insulation resistance of the phases of the monitored network 14 changes relative to the earth, the magnitude of the flowing current changes. This current in the windings of transformers 5, 6 induces an emf proportional to the insulation resistance of the controlled network 14 relative to the ground. The EMF of the current transformer 5 is proportional to the total insulation resistance with respect to the earth of the entire monitored network, and the current voltage of the transformer 6 is proportional to the total insulation resistance relative to the earth of the corresponding controlled network. The induced emf in the main indicator with the actuator 3 and the auxiliary indicator with the actuator 7 are converted into signals proportional to the active or full resistance of the insulation of the monitored network relative to the ground.

In order to ensure reliable automatic disconnection of areas of the monitored network during single-phase closure, the secondary winding 12 of the voltage transformer 9 is bypassed by the switching unit 8. As a result, the voltage transformer 9 is switched to short circuit mode. At the same time, the resistance of the secondary winding 11 decreases, and its value practically does not affect the resistance of the phase-zero loop of the monitored network. In this mode, the voltage generator 1 is turned off, and after the automatic shutdown of the damaged section of the monitored network, it is put back into operation.

The device allows you to record the level of insulation resistance relative to the ground of the entire monitored network and its individual sections at any time, which ensures the timely detection of the tendency to decrease

insulation resistance, i.e., makes it possible to predict preventive measures, and the damaged section of the monitored network can be turned off for preventive maintenance before the isolation of the monitored network to the ground breaks down.

Claims (1)

Invention Formula An apparatus for measuring insulation resistance in networks with a deaf-grounded neutral, comprising a voltage generator, a grounding conductor, a main indicator with an additional element, a power transformer of a controlled network, characterized in that, in order to improve the measurement accuracy at large values of leakage resistance, him entered current transformers, a secondary indicator with an executive element, a voltage transformer, a switching unit, the voltage generator output being shunted by the primary winding of a voltage transformer, the first secondary winding leads of which are connected to the output of the switching unit, and the second secondary winding terminals are connected respectively to the neutral of the power transformer a controlled network and a zero bus to which the earthing switch is connected, and the outputs of the main and auxiliary indicators with actuators are bridged by the windings of the corresponding current transformers, while the winding of one of the current transformers is magnetically connected to the neutral of the power transformer of the controlled network, and the winding of the other current transformer is phases of the monitored network. Sources of information taken into account in the examination 1. USSR author's certificate Kc 560190, cl. From 01K 27/18, 1975.