SU1083134A1 - Device for redetermination of cable insulation break location - Google Patents

Abstract

A DEVICE FOR ELIMINATING THE ELECTRICAL BREAKDOWN of a cable insulation comprising an electromagnetic channel, including a blocking signal generating unit and a serially connected first conversion unit, a first preamplifier, a first bandpass filter, and a first final amplifier, as well as an acoustic channel including a serially connected second conversion unit, the second pre-amplifier, the second band-pass filter. The second terminal amplifier and the first key element and the peak voltmeter connected in series, one of the outputs of the blocking signal generation unit is connected to the control input of the first key element, characterized in that, in order to improve the accuracy of determining the location of electrical insulation, instantaneous values, the second key element, and the output of the final amplifier of the electromagnetic channel is connected to the input of the block of instantaneous values, the output of which connected to the input of the blocking signal forming unit, one of the outputs of which is connected via the second key element to the control input of the block of instantaneous values, and the output of the final amplifier of the acoustic signal is connected to the information input of the first klk khevogo element.

Description

The invention relates to electrical measuring equipment and can be used to detect the location of electrical breakdown of insulation of a cable located in the ground. A device is known for refining the location of electrical isolation, which contains a high-voltage pulse generator, electromagnetic and acoustic transducers connected respectively by a standard amplifier and corresponding display units (headsets and gauges). However, the known device is characterized by an insufficient accuracy of determining the sample location. isolation of the cable due to the low reliability of recording of spark-break signals against the background of general interference, the sources of which are These include power transmission lines, electric transport, soil microvibration, etc. Closest to the proposed technical entity is a device comprising an electromagnetic channel with a blocking signal forming unit and an acoustic channel, each of which includes a series-connected transducer, a preamplifier, a band-pass filter, a terminal amplifier, and an amplitude detector as well as an acoustic indicator a driver, a driver of enabling pulses, and a key element — the driver of the driver of enabling pulses is connected to the input of an amplitude detector of electrons the output is connected to one of the inputs of the key element, the other input is connected to the input of the amplitude detector of the acoustic channel, and the output is connected to the input of the indicator of the acoustic channel, which uses a peak voltmeter 2. A disadvantage of this device is also the low accuracy of determining the location of electrical breakdown of the cable insulation, which is caused by the appearance of spurious pulses at the output of the amplitude detector of the electromagnetic channel, allowing the converted acoustic signal to pass through the key element, i.e. low immunity of the device and, as a consequence. low accuracy of limiting the cable breakdown zone. In addition, the use of a peak voltmeter in a known device, characterized by a large decay time of the indicator, prevents the operator from accurately registering each spark sample in the presequence of breakdowns separated by small time intervals. This results in misses of reception of spark gap signals, as a result of which there is a need to increase the total supply time for test high voltage cables, which leads to an increased likelihood of conductive paths (sintering) in places of reduced insulation of cable elements, after which damage location becomes impossible. The purpose of the invention is to increase the accuracy of determining the location of electrical breakdown and reduce the time to search for a place of damage. This goal is achieved in that the device for refining the location of electrical breakdown of cable insulation, comprising an electromagnetic channel, including a blocking signal generating unit and a first conversion unit connected in series, a first preamplifier, a first band-pass filter and a first terminal amplifier, and an acoustic signal, including a second conversion unit connected in series, a second pre-amplifier, a second bandpass filter, a second terminal amplifier and a sequence the first crank element and the peak voltmeter, one of the outputs of the blocking signal generation unit is connected to the control input of the first key element, the instantaneous value limiting unit is entered, the second key element is connected to the input of the instantaneous value limiting unit, the output of which connected to the input of the block forming signal blb4sirovki, one of the outputs of which through the second key element is connected to the control input of the block tim instantaneous values, and the output terminal of the amplifier is coupled to the acoustic signal data input of the first key member.

Figure 1 shows the block diagram of the device, figure 2 - time diagrams that explain its work.

The device contains an electromagnetic channel 1 and an acoustic channel 2. Channel 1 contains the first preamplifier 4, the first preamplifier 4, the first bandpass filter 5, the first, terminal amplifier 6, the instantaneous value limiting unit 7, the blocking signal generation unit 8 in series. Channel 2 15 contains a serially connected second conversion unit 9, a second preamplifier Yu, a second band-pass filter 11, a second terminal amplifier 12, a first key element 13, a peak voltmeter 14. One of the outputs of block 8 is connected via a second key element 15 the control input of the block 7. The other output of the block 8 is connected to the control- 25 of the first key element 13.

The operation of the device is based on the fact that the intensity is applied: by appropriate transducers of electromagnetic and acoustic signals excited by spark breakdowns of cable insulation increases as one approaches the site of damage, reaches a maximum above the spot, a spark breakdown, which is fixed by the corresponding device.

The device works as follows.

After determining the boundaries of the section (along the cable route) by known methods, within which the insulation resistance of the cable is lowered, the operator places the proposed device within this area. in this case, the conversion unit 9 is installed directly by the operator.

I

The test cable from the generator is supplied with test signals, 50 which are high voltage pulses, as a result of which spark breakdowns occur in the place of reduced cable insulation (for example, at the time of time (J figure 2, a) .. 55 Electromagnetic spark induced and acoustic vibrations are sensed by blocks 3 and 9 and converted

they are into electric pulse signals, the amplitude of which is inversely proportional to the distance from the transducers to the place of the spark sample.

In electromagnetic channel 1, the signal from the output of unit 3 is sequentially amplified by amplifier 4, filtered by filter 5, additionally amplified by amplifier 6 and fed to input of unit 7 at time ti (Fig. 2, b).

In the initial state, the block 7 is a maximum limiter with a zero threshold limit, therefore the negative signal peak (Fig. 2, b) goes through the limiter without loss to the input of block 8.

When the instantaneous value of the voltage of the negative peak U of the block 8 reaches, the blocking signal (Fig. 2, d) is generated at the output of the latter, which through the second key element 1.5 enters the control input of the block 7. At the same time, the limiting threshold at the moment of time. abruptly changes to zero, and the passage of any signals through the limiter completely stops. Thus for the time of i§ t4-i2 of Fig.2, c, and d). the input of block 8 is completely blocked. The blocking time is selected from the following ratio

2

 50P.Alax. 7

(one)

the resonant frequency of the band pass filter 11;

the longest delay time of the acoustic signal relative to the electromagnetic signal at the boundary of the spark-flash limit zone.

/ 1 A i / i

,

MCTKC

 .Uf

.c A

Max

V

a

radius of the spark cut-off zone;

the maximum normalized depth of the cable, the speed of propagation in

the ground of the acoustic and electromagnetic signal, respectively (Vc,.,) f At the output of block 8, a pulse is formed (Fig. 2, d), which closes the key element 13 in the time interval t. t, .. The front of this pulse is delayed around the front of the pulse at the output of block 8 for the time win W4H Un Zap ". In the acoustic channel 2, the signal from the output of block 9 is sequentially cast by amplifier 10, filtered by band pass filter 11, additionally amplified by amplifier 12 and through the key element 13 closed from the moment of time (Fig.), it is fed to the input of the peak voltmeter 14 and is indicated by it. The peak voltmeter reading is directly proportional to the amplitude of the first sub-wave (peak) acoustic

/

V

0tl9.l

t t

g whom the signal and, consequently, the greater, the closer is the acoustic transducer of the device to the place of the spark sample. Hence, the specification of the place of electrical breakdown of the cable reduces to the operator finding the position of the acoustic transducer on the ground surface, at which the indication of the peak voltmeter will be the highest. Obviously, the maximum readings will be observed directly above the spark point. The proposed device improves the accuracy of determining the location of the electrical insulation of the cable and also reduces the time it takes to detect cable damage and, consequently, the cable recovery time.

Claims (1)

DEVICE FOR REFINING A PLACE OF ELECTRIC BREAKTHROUGH Insulation of a cable, comprising an electromagnetic channel including a blocking signal generating unit and a first conversion unit, a first pre-amplifier, a first band-pass filter, and a first end amplifier, and an acoustic channel including a second conversion unit in series , a second preamplifier, a second bandpass filter, a second end amplifier, and a first key element connected in series nt and peak voltmeter, one of the outputs of the blocking signal generating unit is connected to the control input of the first key element, characterized in that, in order to improve the accuracy of determining the location of electrical breakdown of insulation, an instant value limiting unit, a second key element, are inserted into the device, and the terminal output the amplifier of the electromagnetic channel is connected to the input of the instantaneous value limiting unit, the output of which is connected to the input of the blocking signal generating unit, one of the outputs of which second key element connected to the control input of the restriction of the instantaneous values, and the output terminal of the amplifier is coupled to the acoustic signal an information, i nym key input of the first element. _a SU „„ 1083134