SU1766284A3 - Device for determining of cable line damage location - Google Patents

Abstract

The invention relates to a measuring and control technology and can be used to detect the damage site of an underground cable line. The aim of the invention is to improve the accuracy of detecting the location of damage to the cable line by increasing the noise immunity of the device from external industrial noise. The device contains a low-frequency generator connected to a damaged cable, and a receiving unit containing a source of DC voltage, as well as serially connected input circuit (receiving antenna), matching unit, narrow-band amplifier with adjustable gain, selective filter, threshold unit, indicator. The threshold unit contains three resistors, two pn-p-transistors and a capacitor and is made according to the scheme of a two-stage amplifier with voltage comparing. The search for the damage site is carried out by moving the antenna of the receiving unit of the device over the cable route. Since the threshold unit does not transmit a signal below the threshold for its operation, a dead zone is formed on both sides of the track, within which the signal is not fixed by an indicator (for example, a telephone). When the antenna is above the damage, the STEP 1 bar of the dead zone is reduced to a minimum, which is fixed by the indicator. By introducing a threshold unit and making the filter selective, all interferences induced by external sources are cut off, and the accuracy of detecting a cable fault is increased accordingly, regardless of the depth of the cable. 2 Il. J

Description

The invention relates to a measuring and control technique and can be used in devices for detecting a damage site of an underground cable line.

The purpose of the invention is to improve the accuracy of detecting the location of damage to the cable line by increasing the noise immunity of the device from industrial noise.

FIG. 1 shows a block diagram of the device; in fig. 2 - electric

selective filter circuit with a threshold block.

The device contains a low-frequency generator connected to a damaged cable (not present in the drawing) and a receiving unit containing a constant voltage source (not present in the drawing), an input circuit (receiving antenna) 1 connected in series, 1 matching unit 2, a narrow-band amplifier with an adjustable factor amplification, selective filter 4, threshold block (as part of filter 4), indicator 5, turn on VJ

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A series-connected broadband amplifier 6 and a telephone 7. The input of the amplifier 6 is an input of the indicator 5. The filter 4 is selective. It contains inductance 8, capacitor 9, which are connected in parallel to the input and output circuits of the filter (see Fig. 2). The threshold unit (see Fig. 2) contains the first 10 and second 11 pnp transistors, the first 12, the second 13 and the third 14 resistors, a capacitor 15. The first output pin of the selective filter 4 is connected to the pnp transistor base 10, the collector of which is connected via a resistor 12 to the negative terminal of a constant voltage source and through a capacitor 15 to the first terminal of a resistor 13 and the base of a pnp transistor 11, the collector of which is connected via a negative terminal of a resistor 14 and the first input of the indicator 5, the second input of which With a pnp transistor 11 emitter, with a second output of resistor 13, with a pnp transistor emitter 10, with a positive output of a constant voltage source, and with a second output output of a selective filter.

The proposed device operates as follows.

A low-frequency generator is connected to the cable to be tested. The receiving unit of the device is located near the generator and, by changing its frequency, the signal appears in the indicator (telephone).

After connecting the generator to the cable to be checked and adjusting the frequency of the low-frequency generator to the receiving frequency of the receiver of the locator, the receiving antenna of the device is placed at the maximum receiving level. In this case, the signal leading to the receiving antenna is fed to block 2, where a small input impedance of the antenna with a high input impedance of amplifier 3 is matched. Amplifier 3 amplifies the signal to the threshold level of the trigger device. Passing through filter 4, a signal of 0.25 V opens the transistor 10. Due to the fact that the base of the transistor 10 is bounded by the low resistance of the filter 4, the transistor 10 opens only with single-pole pulses, i.e. The signal level is 0.25 V. At the same time, it operates as a voltage comparator. From the collector of transistor 10, the signal is fed to a differential chain consisting of a capacitor 15 and a resistor 13. Since the level of the useful signal after filter 4 will always be greater than the level of interference, and the differentiating chain suppresses weak signals, the output signal will be observed at its output

of pointed pulses of the same polarity and the frequency to which the filter 4 is tuned. Next, from the integrating chain, the signal is fed to the base of transistor 11, which

also acts as a voltage comparator and opens with pulses larger than 0.3 V. The signal from the collector of transistor 11 is fed to indicator 5. At the output of transistor 10, interference is suppressed

0 with a level of 25 dB. After the differentiating chain and voltage comparator, which is played by transistor 11, the interference is suppressed with a level of 60 dB and is fed to indicator 5.

5 The input tailored loop (antenna) 1 is oriented above the line of the males to the minimum signal, and the signal at the output of the device when the receiving antenna is above the undamaged cable will be absent. When antenna 1 is displaced to the right or left of the laid cable axis in the control telephones, the frequency of the generator connected to the checked one will be heard

5 cable.

Due to the fact that the threshold device of the selective filter 4 does not pass a signal below the threshold of its operation, a dead zone is formed on both sides of the path.

0 Its size depends on the generator power, on the depth of the track, and on the voltage at which the threshold unit of the device operates.

When antenna 1 passes over damage, the width of the dead zone is reduced to a minimum, which is fixed by the display unit.

By introducing a threshold unit and applying a selective filter, the accuracy of detecting damage to an underground cable line is increased, regardless of its depth, and the power of the low-frequency generator is reduced by a factor of 10 to 15 and thus the weight of the device

Claims (1)

5 claims A device for locating cable line faults, including a low-frequency generator of the test signal, connected to the cable line to be tested, and a receiving unit containing a constant voltage source, an indicator, as well as serially connected input circuit, matching unit, narrowband amplifier with adjustable 5 by a gain factor, a filter different in tnm that, in order to improve the detection accuracy of the damage site by increasing the noise immunity of the device against industrial interference, a threshold unit is inserted in the device containing the first and second pnp transistors, the first, second and third resistors and a capacitor, while the first output of the filter is connected to the base of the first pnp-r transistor, the collector of which is connected via the first resistor to the negative terminal of the constant voltage source and through a capacitor to the left terminal of of the second resistor and the base of the second ppn transistor, the collector of which is connected 0 through a third resistor with a negative output of a constant voltage source and with the first input of the indicator, the second input of which is connected to the emitter of the second pnp transistor, to the second output of the second resistor, to the emitter of the first pnpp transistor , with a positive output of a constant voltage source and with a second output terminal of the filter, which is made selective. ABOUT Indicator