SU128077A1 - Device for determining the location of damage in electrical cables - Google Patents

Description

The present invention relates to devices for detecting a damage site in electric cables based on the supply of a high voltage electric pulse to a conductor of a cable under test, which creates an oscillating spark through a damaged place. Determining the distance to the location of damage is performed in such devices by measuring the duration of the discharge oscillation using a circuit containing a capacitor, charged through a control electronic lamp, the unlocking and locking of which is carried out under the action of pulses from the two auxiliary lamps, at the onset of and the end of the measured time interval.

The proposed device differs from the known ones in that a capacitor is included in the bridge circuit, the shoulders of which are the indicated control electronic lamp and a number of active resistances included in this circuit through normally closed contacts of the relay disconnecting the capacitor from the circuit after its charge ends.

With such an implementation of the device, leakage of current is eliminated and the charge of the capacitor is retained, which increases the accuracy of the intent of the time intervals.

FIG. Figure 1 shows the scheme for determining the location of cable damage by means of the device proposed; in fig. 2 - electrical device diagram.

The device makes it possible to determine the place of damage of the electric cable laid in the ground (Fig. 1) by feeding into the cable the source from the source AND of an electric impulse of high voltage creating an oscillating spark in the damaged place I The distance to the damage site is found by measuring the duration of the first half period of oscillations of this discharge. For this purpose, an electronic microsecond MC is used. This Device (Fig. 2) contains a capacitor C |, charged from a DC source through a control electron lamp // i, works. in key mode. Unlocking and locking the lamp L. occurs at the moments of the beginning. and the end of one half period of the measured oscillations. Electric (pulses for unlocking and locking this lamp are from two auxiliary lamps L and Lz. At the device entrance there is a block of L and L electron tubes used to convert the first half-cycle of oscillations into electric pulses, the interval between which is equal to the measured time interval.

Up to the time of measurement, the voltage on the charge capacitor Ci is zero. During the measurement, the lamp L is unlocked for a time corresponding to the duration of the measured interval, and the capacitor C is charged ;. The voltage on the charge capacitor Ci, obtained during the charging process, is measured by an electronic voltmeter assembled on the lamp L, and determines the duration of the charging pulse.

To eliminate the influence of leakage currents on the charge of the capacitor Ci, a compensation circuit is applied, the circuits of which pass through the contact of relay P. This circuit is a bridge, the shoulders of which are the control lamp L1 and a series of active resistances R, and a capacitor is inserted into the diagonal Ci. Not before the start of measurement, the winding of the relay P does not flow around the current and the relay contacts are arranged as indicated in the diagram (Fig. 2). Balancing the bridge, at which the voltage at the terminals of the capacitor Ci is zero, is achieved by adjusting the resistance RT. At the end of the charge of capacitor Ci, relay P disconnects it from all external circuits.

Subject invention

A device for detecting a damage site in electric cables, based on supplying a high voltage electric pulse to a conductor of a tested cable that generates an oscillating spark across a damaged place, and determining the distance to the damage site by measuring the duration of the discharge oscillations using a circuit containing a capacitor charged through a control electron tube, unlocking and locking of which occurs under the action of pulses from two auxiliary lamps, B moments n The beginning and the end of the measured time interval, characterized in that, in order to increase the measurement accuracy of time intervals by eliminating the self-discharge of the capacitor, the latter is included in the bridge circuit, the shoulders of which are the specified control lamp and a number of active resistances included in this circuit through the normally closed contacts of the relay, which disconnects the capacitor from the circuit after its charge ends.

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