SU1325376A1 - Device for measuring electric circuit insulation resistance - Google Patents

Abstract

The invention relates to the measurement and control of the insulation resistance of electric circuits of direct and alternating current with disconnected power sources and can be used in devices for continuous monitoring of the insulation state of various circuits, including alternating current, containing static converters and straighteners. The purpose of the invention, the improvement of measurement accuracy, is achieved by eliminating the error due to the capacitance of the electrical circuit under study, as well as the capacitance of the coupling capacitor. For this, diodes 3 and 5, a zero voltage level meter 7, terminals for connecting the measured circuit 4, an exemplary adjustable resistor 6, potentiometer 8 and a rectifier 9 are additionally introduced into the device. The drawing also shows a source I of an alternating voltage, capacitor 2, resistance 10 and capacitor II of the circuit to be measured. The introduction of these elements is also achieved by simplifying the device and expanding the area of its use. 1 il. (L bo 1C ate with 4J and

Description

The invention relates to electrical measuring equipment, in particular, to measuring and controlling the insulation resistance of electrical circuits of direct and alternating current with disconnected power sources, and can be used in. devices for the continuous monitoring of the isolation states of circuits for various purposes, including alternating current, containing static converters and rectifiers.

The purpose of the invention is to increase the measurement accuracy by eliminating the error due to the capacitances of the studied electrical circuit and the separation capacitor, as well as simplifying the device and expanding the range of its use.

The drawing shows the electrical circuit of the device for measuring the insulation resistance of electrical circuits.

The device contains a source of alternating voltage 1, a capacitor 2, a first diode 3, a measuring circuit 4, a second diode 5, an exemplary adjustable resistor 6, a meter 7 of a zero level of a constant voltage, a potentiometer 8, a rectifier 9, and one output the alternating voltage source 1 is grounded, the other output is connected to the first output of the capacitor 2 and the input of the measuring instrument 7 of the zero level of the constant voltage, the second output of the capacitor 2 is connected to the second input of the measuring instrument 7 of the zero level of the constant voltage, the anode of the diode 3 and the cat Odom diode 5, the anode is through a model adjustable resistor 6 is grounded.

The cathode of diode 3 is connected to a movable contact of a potentiometer 8, the two terminals of which in turn are connected to two inputs of the rectifier 9, and its three outputs through three terminals are connected to the measured electrical circuit 4, which is from the 10 insulation resistance (RHJ) “Insulation tanks 11 ().

The device works as follows.

During the second half period, the voltage of capacitance C of the measured electric circuit 4 remains practically charged, since the charge time constant is more than 100 times less than the discharge time, and the duration of one half period even at the supply voltage frequency of 50 Hz is 0 , 01s.

Thus, the charge - discharge of the capacitor 2 and the charge of the capacitance of the circuit 4 under study occurs during one period of the supply voltage of the source of alternating voltage.

In subsequent periods of operation of the alternating voltage source 1, the capacitance Su of the measured circuit 4 is charged and recharged by the capacitor 2 only through the exemplary adjustable resistor 6. Therefore, if the insulation resistance values of the circuit 4 and the exemplary adjustable resistor 6 are equal, the constant voltage of the capacitor 2 (average

voltage over the period of supply voltage) is zero.

Before measuring the insulation resistance of the circuit under study, a constant compensation is made.

component, due to the presence of the operating voltage on the circuit 4, using a potentiometer 8, the alternating voltage source 1 is de-energized and the value of the resistance of the potentiometer arms at which the readings of the dc voltage meter 7 have a value is selected. When the alternating voltage source 1 is turned on, under the action of its single-half-period voltage of one polarity, capacitor 2 and capacitance C in the first voltage period are charged.

circuit 4. At the same time, congenerator 2 is also charged. The capacitance of the capacitor 2 choose more than the maximum possible capacity of the investigated circuit 4.

After charge capacity studied

the circuit 4 continues to charge the capacitor 2 through the resistance 10 () of the insulation of the circuit 4. When the polarity of the source 1 changes, the half-wave voltage of the other polarity through the capacitor 2 and the pilot diode 5 is applied to the reference adjustable resistor 6. In this case discharge — charge of capacitor 2 and partial discharge of the capacitance of the circuit under study 4. The constant discharge of the capacitance of the circuit under study 4 with an expected insulation resistance value (over 100 kΩ) is 10–20 s, since this

3

voltage period of source 1, the capacitance of the circuit under study 4 is discharged only on the resistance of the circuit under study 4.

By selecting the sensitivity of the DC voltage meter, the specified accuracy of the measurement of the insulation resistance of the circuit under study 4 is ensured.

The magnitude of the insulation resistance is determined by the formula

R

RV RS R + R:

de

R

of

Ss

R R, K

insulation resistance of the measured circuit 4; resistance value of the reference adjustable resistor 6; resistance value of the shoulders of the compensating variable resistor 8.

Claims (1)

Invention Formula A device for measuring the insulation resistance of electrical circuits containing a variable source; Compiler V.Smirnov Editor E.Papp Tesfed V.Kadar Proofreader A.Ilyin Order 3102/39 Circulation 730 Subscription ° VNIIPI USSR State Committee for inventions and discoveries 113035, Moscow, LS-35, Raushsk nab. 4/5 Production and printing company, Uzhgorod, st. Project, 4 3253764 one output of which is polarized, and the other output is connected to the first capacitor output, the first to connect the measured circuit, which means that, in order to increase the measurement accuracy in a wide range of values of the measured electrical capacitance circuit and simplification, two diodes are inserted in it, a dc voltage level meter, a second and a third terminal for connecting a measured circuit, an exemplary adjustable 15 is a resistor, a potentiometer and a rectifier, the first capacitor lead being connected to the first input of a zero-voltage meter of a constant voltage, its second input is connected to the second 20 the output of the capacitor, the anode of the first and the cathode of the second diode, the anode of the second diode is grounded through an exemplary adjustable resistor, the cathode of the first diode is connected to a movable output 25 potentiometers, two terminals of which are connected to two inputs of the rectifier, three outputs of which are connected to three terminals for connecting the measured electrical circuit.