SU995027A1 - Device for checking three-phase electric network insulation conductivity - Google Patents

Description

The invention relates to a relay protection and automatics progivoavariynoy in electrical systems, it can be used as protection against ground leakage currents either for kontro- ₅ A conduction insulation in electrical networks of underground mining enterprises.

A device is known for determining the _Jo capacity of electrical installations relative to earth, for which the voltage of an extraneous source of non-industrial frequency is used as the measuring voltage, the elements of the device are included _t5 between neutral and earth [1D.

The closest technical essence to the invention is a device for continuous monitoring and automatic adjustment of capacitive current compensation 20, containing a voltage source of non-industrial frequency, a coupling choke, a frequency-selective amplifier, a phase-sensing unit and a measuring system unit, the operation of which is based on measuring the absolute value of the voltage on the inductor accession, the role of which in this case is performed by the extinguishing reactor

This voltage practically depends only on a change in the capacitive conductivity of the insulation, provided that the active conductivity of the insulation is small. For this reason, this device cannot be directly used for separate monitoring of the active and capacitive conductivities of the insulation of the electrical network.

The aim of the invention is to expand the functionality of the device.

This goal is achieved by the fact that in the device for monitoring the conductivity of the insulation of three-phase electrical networks containing a voltage source of non-industrial frequency, one

995027 4 terminal of which is connected to the common bus, 'and the second terminal is connected through the connection choke to the terminal for connecting the control object, the second output of the connection choke is connected to the input of the frequency-selective amplifier, a physically sensitive element connected to the indication element, an adder is inserted, a phase-shifting element, a second phase-sensitive element and a second indi-cation element, the second output of a non-industrial frequency voltage source connected to the first input of the adder, the second input of which is connected It is connected with the input of the phase-shifting element, the output of the hour-15 totes. selective amplifier and the first input of the first phase-sensitive element, the second input of which is connected to the output of the adder and the second input of the second phase-sensitive element, the first input of which is connected to the output of the phase-shifting element, and the output the second. phase-sensitive element is connected to the second indication element. 25

The drawing shows a diagram of the device., ·

It comprises a voltage source 1 nonindustrial frequency choke 2 attachment 30 frequency-selective amplifier 3 for separating non-industrial frequency component on the throttle connection, an adder 4, fazopovorognoe device 5, phase sensitive unit 6 prednazna- ₃₅ chenny voltages proportional to isolate active and capacitive insulation conductivity, measuring instruments 7 for visual reading of measured values. * before

The control process is as follows.

Controlling the current flowing through, resistive and capacitive isolation conduction network, causes a fall in voltage ⁴⁵ Niya on the throttle connection. The secondary winding of the induction choke is connected to the input of a frequency-selective amplifier 3. The voltage from which the component of the non-industrial ⁵¹ frequency Oc is extracted is supplied to one input of the adder, and the measuring winding of the source I of the industrial frequency voltage is connected to the other input.

From the output of the adder 4, the reference voltage is 5. ''0 _{s is} applied to the inputs of phase-sensitive circuits. The output of the frequency-selective amplifier 3 is connected to the second inputs of the phase-sensitive circuits. The selection of the active component is carried out by directly comparing the phase voltage and (j _c using the phase-sensitive circuit. To isolate the reactive component, the voltage (j ^ ^{to the} phase-sensitive circuit is supplied through phase-shifting a device that changes the phase of the voltage by 90. A phase-sensitive unit containing two phase-sensitive circuits performs phase comparison of the values of the reference voltage 0 _s and controlled 01 · which makes it possible to isolate the values proportional to the active and capacitive conductivities of the insulation of the network.Visual reading of the measured values is carried out using measuring instruments calibrated in units of conductivity or current units.

Compared with the known, the proposed device does not require measuring current transformers, and the voltages that are sources of errors, continuously monitors} _α and | p both under the operating voltage and when removing the operating voltage from the controlled network, in addition, connecting the device to The network does not lead to an increase in its total conductivity, since the inductance of the inductor can be connected. be adopted such that partial or full compensation of the network capacity is provided.

The device receives power from an independent source, which allows calibration of measuring instruments both in current units and in conductivity units.

Claims (1)

1. Electrical safety in the mining industry. M ,, Nedra, 1977, p. 191, 2, Weinshein R, A, and Ankov S, E. Continuous monitoring and automatic adjustment of capacitive current compensation using a superimposed current of part  tots 25 Gp. Sat reports Neutral modes in electrical systems .. Kiev, Naukova Dumka, 1974 (prototype). UA fff