RU2681416C1 - Device for searching for damages of insulation of high-voltage cable - Google Patents

Abstract

FIELD: electrical engineering.SUBSTANCE: invention relates to the field of converting electrical engineering and is intended for the formation of acoustic pulses when searching for places of damage in power cable lines. Device for generating an acoustic signal when searching for places of damage to the insulation of a high-voltage cable includes as a high-voltage source a burning device connected to a capacitor through a switch for remote control of high-voltage circuits. Switch for remote control is designed as a high-voltage pulse switch containing two resistors, a diode, a capacitor, a relay and a thyristor. Thyristor is connected to resistors connected in parallel, forming a divider, a capacitor and a diode connected in series with the thyristor and connected to the winding of the electromagnetic relay, also connected to the switch capacitor.EFFECT: improving the accuracy of finding the place of damage and accelerating the process of finding damage to the insulation of a high-voltage cable by an acoustic method.1 cl, 4 dwg

Description

The device according to the invention relates to the field of converting electrical engineering and is intended to improve the basic parameters of the acoustic pulse generator in electrical installations to search for damage points in power cable lines.

The prior art various methods for determining the location of damage in electrical networks and communication cables, which are conditionally divided into two groups: relative, allowing you to approximately determine the distance from the measurement location to the location of damage (pulsed, vibrational discharge, wave, loop, capacitive, high-frequency), and absolute, indicating the exact location of the damage on the track (acoustic, induction, induction-switching, contact).

At the same time, it is believed that at least two methods must be used: relative and absolute, since the first ensures the speed of determining the damage zone, and the second determines the exact place on the track where excavation is necessary. [V.S. Dementiev, V.K. Spiridonov, G.M. Shalyt "Determining the location of damage to power cable lines." Gosenergoizdat, Moscow-Leningrad, 1962].

There are later developed fairly quick and accurate methods for finding damage to cable networks using two considered absolute methods. So known is a complex of equipment for determining fault locations in cable networks, combining two absolute methods: acoustic, induction. This complex consists of a generator and a receiver with induction and acoustic transducers. [Molokanov M.V., Spiridonov V.K. “A complex of induction and acoustic equipment for determining the location of damage in cable networks”, Energetik, No. 11, 1979, p. 28-29.]. The induction method determines the route, the depth of the cable and the location of the short circuit. The magnetic field of the cable created by this current induces voltage in the induction converter, amplified on a special amplifier and moved along the path. The signal indicator is a headphone or dial gauge. And then the places of damage associated with a high-voltage discharge in this place are determined by the acoustic method, its signals are captured by the acoustic transducer. Both methods give a high search result, but do not work one without the other. The scheme for combining these methods is very complex and works intermittently.

At the same time, a combination of the two absolute methods of acoustic and induction in one device is known, although the authors called this method acoustic: [“A device for determining damage to cable lines by the acoustic method” RF Patent No. 2010253, IPC G01R 31/08], in which To increase the reliability and efficiency of the search, acoustic and induction transducers are simultaneously contained, connected to a two-channel amplifier with a common power supply, at the output of which a logical operation is implemented, and the signal is transmitted through a single-shot at the input of the indicator of the place of damage. The disadvantage of this device is that the acoustic and induction transducers are completely different in their characteristics, and they must work separately, and combining them in one device is a difficult, complex and expensive technical task. In addition, a piezoelectric element is used in the acoustic system, and this is a weak point in the system, since the use of piezocrystals implies a high sensitivity to interference from external electromagnetic interference and to mechanical shocks, i.e. it is necessary to provide the system with additional reinforced shielding from these interference, which significantly increases the weight and dimensions of the device.

The acoustic method is the most universal of the absolute methods, which consists in creating powerful electric discharges at the site of damage and fixing on the earth's surface electromagnetic waves transformed into sound using sensitive receiving devices. To create powerful discharges in the place of damage, electric energy is pre-accumulated in high-voltage capacitors or in the capacitance of the cable itself by charging from a rectifier installation. When the breakdown voltage is reached, this energy is consumed in a very short time (tens of microseconds) and a powerful blow occurs at the site of damage. The sound from this shock spreads in the environment and can be heard on the surface of the earth. Typically, the discharge frequency is 2-3 seconds.

The absolute immunity to industrial electromagnetic interference and the complete absence of “transfer” to neighboring objects make the acoustic method an excellent alternative to the electromagnetic method of searching for metal pipelines in difficult urban conditions, and the acoustic method is simply irreplaceable for tracing communications from non-conductive materials. The acoustic method allows you to:

- determination of the location of a cable line that is energized. The greater the load (current) of the line, the better it is tapped;

- determination of the route of the disconnected line. For this, an audio signal generator is used. It connects between two cores of the line at one of its ends, at the other end these cores are short-circuited. The signal supplied to the line is a sequence of modulated electromagnetic pulses with a low repetition rate.

- determination of the location of the closure of two cores with each other. For this, a signal is sent from one of the ends of the line to these cores. The cable radiates it to the place of damage, after it the signal disappears.

Due to the versatility, accuracy and speed of determining the location of damage in power cable lines, the acoustic method is widely used throughout the world.

The electrical industry produces pulse generators, including acoustic ones, for example, the GVI-2000M high-voltage pulse generator used in the LVI HVT-1 Laboratory (Yaroslavl Electromechanical Plant LLC), designed to store energy in high-voltage capacitors and send high-voltage pulses of various frequencies with the purpose of creating the conditions for determining the location of damage in power cables by the acoustic method [http://www.emzlvi.ru/doc/Leaflet%20LVI-3FAV.pdf], but this generator works in conjunction with equipment with etsialnoy mobile laboratory - a bulky device that moves together with the car. Automatic trace generator AG-144 is manufactured by Aka-Geo LLC [http://www.akageo.ru/], it is designed to create propagating signals in covert communications routes with active tracing methods (electromagnetic or acoustic). The device creates an alternating sinusoidal current in the communication under study, necessary to determine its location or sound impulses using the shock mechanism, but at the same time it has a large signal attenuation in the "long" communication. The device is quite cheap and easy to use, but not reliable. In addition, it is currently discontinued [http://www.geo-ndt.ru/pribor-955-generator-trassirovochnii-ag-144-moshnostu-60-vt.htm].

SSG 1100, SSG 1500, SSG 2100 and SSG 3000 surge generators manufactured by a German company. [BAUR GmbH https://www.baur.eu/products/cable-fault-location/surge-voltage-generators/ssg-1500] They are also pulse generators for locating faults in high and low voltage power cables, they are designed in such a way that they generate a pulsed voltage with a steep edge, which is used to break down the cable at the fault location. Highly pulsed electric current at the point of cable damage generates electromagnetic and acoustic waves that diverge from the place of cable damage. These waves can be detected on the surface of the earth using appropriate devices, such as search coils or ground microphones. The generators of this company are reliable, but very expensive, and the average search time, for example with the SSG 1500 generator, is 3-5 hours. Generators SSG 1100, SSG 1500 and SSG 2100 are equipped with a timer tied to the frequency of the mains, which allows you to automatically initiate pulses with repetition frequencies of 10 pulses / min. and 20 cpm The pulse frequency is very low, so the pulses are difficult to distinguish from interference, hence the increase in the search time.

The technical result consists in improving the accuracy of finding the location of the damage and accelerating the process of finding damage to the insulation of the high-voltage cable by the acoustic method, as well as in simplifying the circuit of the device, which is assembled from affordable inexpensive parts, its manufacture is simple and does not require large material costs.

The technical result is achieved in that in a device for generating an acoustic signal when searching for places of damage to the insulation of a high voltage cable, including a burning device as a high voltage source, a switch for remote control of high voltage circuits and a capacitor, a remote control switch charged from a high voltage source is made, as a high-voltage pulse switch controlled by a low-voltage generator, the role of which is the thyristor, is connected with a switch capacitor and one of the resistors, in parallel with which a second resistor is connected to supply voltage to the diode, which provides rectification of the direct current supplied to the winding of a low-voltage pulse electromagnetic relay.

Acquisition of damage by the acoustic method using the device, as a rule, is carried out on topographically defined tracks.

A diagram of a device for generating an acoustic signal when searching for insulation damage of a high voltage power cable is shown in FIG. 1. It includes a high voltage source 1, which is a small-sized burning device (MPU-3), which is constantly connected to the network. A switch for remote control of high-voltage circuits 2, which is a high-voltage pulse switch (VIC), is connected to its output. It is intended to provide a given frequency of impacts of electromagnetic pulses for the formation of an acoustic signal. The frequency of the blows should be such that it can be conveniently picked up by the search receiver of the PP 500 signals (tracer). The device also includes a pulse capacitor 3, which is charged from a high voltage source through a high voltage pulse switch, and when the breakdown voltage on the capacitor is reached, it is broken, which provides electromagnetic oscillations in the damaged cable, which are converted into an acoustic wave.

In order for the device to work quickly according to this scheme, and the accuracy of finding damage was high (the cable lies at a depth of up to 4 meters, and excavation is time-consuming and costly), changes were made to it: namely, in the remote control switch by high-voltage circuits 2, made as a high-voltage pulse switch (VIC), another additional device is integrated, the circuit of which is shown in FIG. 2.

The circuit of the high-voltage pulse switch (Fig. 2) additionally contains resistances Rl (1 K) and R2 (20 K) - both of them, this is a voltage divider. Both resistances were selected experimentally - by changing the volt ampere characteristic (I – V) of the voltage to the control electrode of the KU-201 thyristor. The KU-201 thyristor connected to the resistor R1 serves as a key to control the frequency of the acoustic wave signals. Diode D-203 is built into the circuit of a high-voltage pulse switch for rectification of alternating current into direct current, in order to turn on a low-voltage electromagnetic pulse relay P (14 volts). Capacitor C1 (40 Mk × 220 V), in a pulse switch, serves to create a circuit with frequency-dependent properties. Thus, the high-voltage pulse switch is controlled by a low-voltage generator, the role of which is performed by the KU-201 thyristor. The thyristor turns off when a negative voltage is applied to the control electrode, as a result of which the latter closes, and this process repeats: the capacitor charges again and discharges again by opening and closing the thyristor, and relay P operates in a given frequency mode, directing the signal to the damaged power cable (SC).

A graphical volumetric arrangement of parts of the device is shown in FIG. 3, and a general view of the device is shown in FIG. 4, where:

1. High voltage source - MPU-3 high-voltage burn-through generator (small-sized burning device).

2. High Voltage Switching Switch (VIC).

3. Pulse capacitor (4 Mkf × 6.3 kV).

4. The test power cable (SC).

GES is the main grounding bus.

One of the most significant characteristics when searching for the place of damage to the power cable by the acoustic method is the frequency of the sound wave, with which a signal is supplied to the receiver, with which the track is listened. The speed and accuracy of finding the damage very much depends on how clear and easily audible the signal is. Typically, acoustic installations with burning devices provide a frequency of impulses to the damaged cable once every 2-3 seconds (discharge frequency) [https://elektro-montagnik.ru/?address=labs/lab13/&page=page46]. The most convenient and acceptable for catching by the human ear is the frequency of discharges 1 time in 1.0-1.2 sec. (1 and 1.2 hertz) [A.N. Remizov “Medical and Biological Physics”, 4th ed. Section 2, Ch. 8, // GEOTAR-Media, 2012 .; http://vmede.org/sait/?page=l2&id=Medbiofizika_remizov_2012&menu=Medbiofizika_remizov_2012].

It is the proposed circuit of the high-voltage pulse switch, which is built into the device for locating damage to power cable lines, that provides an acoustic signal with a shock frequency of 1 hit in 1.2 seconds, which allows you to clearly find the location of the cable underground and not deviate from the track during the search , and the pitch (maximum - at the place of the gap) to clearly look for exactly the place of damage. The device allows you to reduce the search time by almost half (from 3-4 hours on average to 1.5-2.0 hours), and increase the accuracy of the search to 90%.

The device operates as follows:

1. Assemble the circuit as shown in FIG. one.

2. Apply voltage to the MPU-3 1 (Fig. 1) and high-voltage pulse switch 2. The speaker system starts after 20 seconds.

3. In the high-voltage pulse switch (Fig. 2), capacitor C1 begins to pass the charge current, and the voltage is supplied to the control electrode of the KU-201 thyristor, which includes the thyristor, the signal from which is fed to the coil of the pulse low-voltage relay P (at the output 14 V) setting the frequency of the signals. 1 hit in 1.2 sec.

4. When the pulse switch is turned on, the storage pulse capacitor C (4 Mkf × 6.3 kV) is discharged into the power cable (SC) to the point of damage to its insulation. A sound signal passes through the cable at a predetermined frequency (1 beat in 1.2 seconds), which is picked up by the headphones of the locator.

The device provides a uniform stable signal with a frequency of 1 hit in 1.2 seconds, which is very well traceable and cannot be confused with noise, therefore, the track is quickly and accurately listened, and the damage site is located, even at a depth of up to 4 meters. The accuracy of the search when using this device reaches 90%.

A device for generating an acoustic signal when searching for places of damage to the insulation of a high-voltage cable, in addition to halving the search time and providing high accuracy of finding breakdown, it is reliable in operation and easy to control. Its dimensions make it easy to carry the device along the track, even in hard-to-reach places. The device is assembled from accessible, interchangeable parts, it is easily mounted, and the material costs for its manufacture are negligible and do not significantly increase its cost.

Claims (1)

A device for generating an acoustic signal when searching for places of damage to the insulation of a high-voltage cable, including as a source of high voltage a burning device connected to A. A. to a capacitor through a switch for remote control of high voltage circuits, characterized in that the switch for remote control is designed as a high voltage pulse switch containing two resistors, a diode, a capacitor, a relay and a thyristor connected to parallel resistors forming a divider, a capacitor and a diode connected in series with a thyristor and connected to the coil of an electromagnetic relay, also connected to the capacitor of the switch.

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