SU779918A1 - Device for measuring electric network insulation resistance - Google Patents

Description

The invention relates to devices for measuring the insulation resistance of electrical networks and, in particular, to devices for controlling the resistance of insulation of electrical networks of alternating current containing static converters and rectifiers as a load. ;

A device for measuring the insulation resistance of electrical networks is known, comprising a measuring DC voltage source, a current meter, and an alternating resis. a torus, whose motor is connected to the Earth through a measuring DC voltage source connected in series with a current meter (l} .-

However, the device cannot be used to measure insulation resistance in AC networks containing rectifiers and static converters as loads. .

The closest proposed by its technical essence is a device for measuring the insulation resistance of electrical networks, consisting of a series-connected meter, measuring

a constant current source and a resistor connected between the earth and the variable resistor engine, the terminals of which are connected

5 to the controlled network 2.

This device also cannot be used to control the insulation resistance of electrical AC networks containing

10 as a load, static converters and rectifiers due to meter distortions, if any; constant component in a controlled network of alternating currents. The purpose of the inventions is to enhance the functionality: and to provide an insulation resistance measurement in AC networks containing a constant voltage component.

The goal is achieved by the fact that a device for measuring the insulation resistance of electrical networks, containing a variable resistor and a circuit of a series-connected measuring source of direct current voltage and a direct current meter connected between

30 engine variable resistor and common bus, entered semiconductor rectifier, the inputs of which are connected to the phases of the controlled network, g outputs - to the terminals of the variable resistor. The drawing shows a schematic diagram of the device.

The device consists of a direct current meter 1, one pole connected to a common bus, a measuring source of direct current voltage 2, one pole of which is connected to the second pole of a direct current meter; variable resistor 3, the slider of which is connected to the second pole of the DC voltage source; the semiconductor rectifier 4, which is connected to the phases of the monitored network, and the outputs - to the terminals of the variable resistor. . -G-A-, .- ..

The device works as follows. - :. -.:. ..-. -

In the compensation mode, the measuring DC voltage source 2 is disconnected and the slider. The variable resistor 3 moves until a voltage (current) equal to zero is obtained between the variable resistor slider 3 and the Earth, thereby generating a constant component that distorts the result. measurements. After that, the measuring DC voltage source 2 is switched on, and the readings of the DC current meter 1 correspond to the total equivalent insulation resistance of the entire Electrical Network. In this case, the current through the DC meter 1 is determined by the equation -.-, - h shm.

-five,- . . ., u

idling voltage

measuring voltage source of direct current; Rg - equivalent - network insulation resistance; resistance to change of 4-resistor;

g is the internal resistance of the measuring DC voltage source. The total conductivity of the circuit isolation is determined by the equation

-ir - ..

 one

(2)

where R, Rj, Rj insulation resistance

AC phase; R.J. . . R isolation resistances

positive poles of the load rectifier; R. . .R - insulation resistance, negative poles

rectifier load. From the given equations (1) and (2), it is obvious that the measurement value is determined not only by the value of eIBIvalent insulation resistance, but also by the ratio of the insulation resistances of rectifier poles and static load converters.

Claims (2)

Invention Formula A device for measuring the resistance of an electrical network, comprising a variable resistor and a circuit consisting of a measuring DC voltage source connected in series and a DC current meter connected between the variable resistor motor and the common bus, in order to expand the functional capabilities, a semiconductor rectifier is introduced into it, inputs to which are connected to the phases of the monitored network, and outputs to the terminals of a variable resistor. Sources of information taken into account in the examination one-. Magarshak B. G. Ship electrical measuring instruments. L., Shipbuilding, 1965, p. 141-146. 2. Magarshak, B. G. Ship's zlekt; measuring instruments. L., Sudo building. 1965, p. 302-306 (prototype