SU141217A1 - Device for signaling a decrease in the insulation resistance of a cable and determining a section with a reduced value of insulation resistance - Google Patents

Description

Devices are known for signaling a decrease in the insulation resistance of a cable and detecting a section with a reduced insulation resistance value, which contain detectors made on cold cathode thyratrons, located along the cable and connected to the control conductor at each monitored cable section. In such devices, the distance to the insulation fault location is determined by long-term measurements using a DC bridge, the measurement accuracy being low due to the effect on the measurement results of the change in the magnitude of the contact resistances at the fault site and the interference currents. In addition, these devices do not provide verification of the operability of the detectors and the determination of the number of the faulty detector.

In the proposed device, the detectors are connected according to the self-register register, the output of which is connected to the decade ring counting circuit, and a key is turned on between the detector thyratron grid and the resistance connected to the cable jacket, and when closed, the number of the defective detector is determined by the number of pulses. This allows us to simplify the device, automate the process of determining the number of the section with reduced resistance, and monitor the operability of the detectors.

The block diagram of the described device shown in the drawing.

The device contains detectors made on cold cathode tiratrons located along the cable and connected to the control core on each monitored cable section. Detectors 1, installed in cable boxes and located relative to each other at a distance of one or several building lengths, are included according to the self-propelled register scheme. The output of the self-propelled gun No 141217-2 of the gist through the pulse shaping unit 2, made according to the repeater scheme, is connected to the decade ring counting circuit 3. The ten-count ring counting circuit 3 is installed on the serviced amplifying point. Using this scheme, the number of pulses arriving from the output of the salute register is counted, and the number of the activated detector is determined.

When the insulation resistance of the cable decreases, due to penetration of moisture into it, through the hole in the lead sheath of the cable in one of the monitored sections of the control cable core, for example, section N, the corresponding N-ro detector responds. At the time of actuation, a current pulse passes through the detector / and transformer 4 in point A. This pulse from transformer 4 goes to pulse shaping unit 2 and further on counting circuit 3. The detector that is triggered creates a potential in the adjacent section of the control core cable, located closer to point A, that is sufficient to trigger the adjacent rear detector (). The detector circuit is assembled in such a way that it only works in one direction, and therefore the detector (L / -j-) does not work.

At the moment of activation (/ V -) of the detector, a current pulse passes through the transformer 4 at point A, which in a similar way goes to the counting circuit 3. The detector (L-1) creates a potential on (N - 2) the detector, due to which will trigger the last, then the detector (L-3) will work, and so on, until all the detectors work. Transformer 4 in point A will then pass N pulses and the digit N will be fixed on the counting circuit, which will correspond to the N-ip detector.

To check the operation of the detectors and determine the number of the defective detector, switch 6 is turned on between the detector thyratron grid installed at the last point B for this section and resistance 5 connected to the cable jacket. In case of a failure of one of the detectors, switch 6 also closes by the number of pulses calculated by a ring counting circuit, determine the number of the faulty detector. The insulation resistance is lowered at one of the sections of the cable test core by means of block 7, and the device is powered from the power supply unit 8, which is a voltage converter on semiconductor triodes, the power source being connected to the power core plus - to the lead sheath cable.

The described device can be used to signal the cable resistance decrease and to determine the section with the low insulation resistance value and is extended to cables that cannot be supplied with air pressure and, in particular, low-frequency broadcasting, and plastic-sheathed cables having two loose conductors.

Subject invention

Claims (2)

I. A device for signaling a decrease in the insulation resistance of a cable and determining a section with a reduced resistance value, an insulator containing detectors made from cold cathode pairs, along the cable and connected to the control core in each monitored cable section, characterized in that in order to automatically determine the number of the section with reduced insulation resistance, the detectors. installed in cable boxes, included in the self-propelled register scheme; the output of which through the pulse shaping unit, made according to the repeater circuit, is connected to a decade ring counting circuit installed at the serviced amplifying point and used to count the number of pulses received from the output of the self-propelled register and thus determine the number of the activated detector. 2. The device, made according to claim 1, is made so that, in order to check the operability of the detectors and determine the number of the faulty detector, between the detector tiratron grid installed in the last controlled area and the resistance connected to the cable jacket, a switch is turned on; when closed, the number of the failed detector is determined by the number of pulses counted by the ring counting circuit. Point and 1