SU676950A2 - Device for locating power cable insulation fault - Google Patents

Description

During the breakdown of isolation of only one core, impulses that occur at the site of insulation damage are first fed to the input of a pulse sensor connected to a damaged core, then at a time interval t, simultaneously to the inputs of two other pulse sensors connected to intact veins.

In the case of the simultaneous breakdown of two cable cores (which often occurs during high-voltage tests of three-phase power cables), the pulses that occur at the insulation damage site are first simultaneously supplied to the inputs of those two sensors that are connected to damaged wires and then temporary interval / - to the input of the sensor connected to the intact vein. In the first case, the signal from that of the sensors (2, 3 and 4) to which the pulse generated by the isolation breakdown had previously approached opens the key circuit 6. Normalized pulses generated by the generator

7, are fed to the input of the counter 8. Simultaneous signals from the other two sensors, to which the pulses from the fault site approach later, close the key circuit 6, interrupting the flow of pulses from the generator 7 to the counter input

8. The number of counted pulses, proportional to the measured time interval t, is registered by the indicator 9. In the second case, the device works in the same way, only the key circuit 6 opens simultaneous signals of those two sensors to which the pulses generated by the breakdown of the insulation came earlier. The key circuit 6 closes the signal of that of the sensors, to the input of which, a pulse from the place of damage later approached.

The proposed device can be simplified if the sensors of 2, 3 and 4 pulses are replaced by one common sensor, for example, a current transformer that is worn on the three wires of the tested three-phase power cable. In this case, during the breakdown of one or two veins, the impulses generated by the breakdown of the insulation, which came along the conductor, the insulation of which is damaged, open the key circuit 6, and the impulses that came along intact veins with a time interval t close the key circuit. Thus, the introduction of an additional impeller sensor, as well as the shorting of all three test leads at the opposite end of the power cable, can at least double the reliability of determining the location of damage and simplify the operation of the device.

Increased reliability is due to the fact that

The additional invention, unlike the main one, determines the distance to the site of damage. The simplification of the operation of the proposed device is due to the fact that when all three cores are shorting at the opposite end of the power cable, their insulation is tested simultaneously and does not require additional testing, as is

takes place at a known device. It is most efficient to use the inventive device for preventive testing of three-phase power cable lines.

Claims (1)

Invention Formula A device for determining the location of damage to the insulation of power cables according to ed. St. No. 565262, characterized in that, in order to increase the reliability of the device and reduce the measurement time, a third pulse sensor was inserted into it, with the third input of the time measurement block connected to the output The third pulse sensor, the input of which is connected to the first output of the third core of the cable under test, the second output of which is connected to the second terminal of the second core of the test cable. Information sources, taken into account during the examination 1. USSR Copyright Certificate No. 565262, cl. G OR 31/08, 1975. 77