CN100410673C - Cable fault predetermined point detection method and detection device - Google Patents

Abstract

A method and a detection device for detecting a predetermined point of a cable fault belong to the field of electric fault detection. It is characterized in that the output ends of the high-voltage DC pulse generating unit and the audio signal injection unit are connected to one end of the discharge unit, and the other end of the discharge unit is connected to one end of the faulty cable, and the high-voltage DC pulse generating unit discharges the faulty cable through the discharge unit, and the The audio signal injection unit superimposes an audio pulsating DC current on the cable on the basis of the ignited arc during the time period when the arc is stable, and receives the audio pulsating DC current through the cable through an audio magnetic field receiving device moving along the cable laying path. The radiated magnetic field, according to the characteristics of a large difference in the amplitude of the audio magnetic field before and after the fault point, judges that the audio magnetic field receiving device is in front of or behind the fault point, so as to quickly perform preliminary rough measurement of the cable fault point point detection. It can be widely used in the field of fault detection of various cables.

Description

Cable fault predetermined point detection method and detection device

technical field

The invention belongs to the detection field of electrical faults, in particular to the detection and location of high-resistance fault points of power cables.

Background technique

With the development of social economy and the acceleration of modernization construction, the electricity consumption of industrial and agricultural production and people's life is increasing day by day, the demand for electricity is increasing, and the safe operation of power grid is required to be higher and higher.

As a power cable that connects various electrical equipment, transmits and distributes electric energy, it has gradually replaced the overhead line. The transmission performance of cable power supply is more stable and reliable than overhead lines in urban and rural areas, and it occupies a small area, which will not affect the city appearance and is not restricted by the natural environment, thereby improving the safety of power supply. It has become the main trend of the future development of domestic and foreign power transmission and distribution networks to use underground power cables to replace overhead transmission lines.

Power cables play a key role in the power system as a carrier for transmitting and distributing electrical energy and connecting various electrical equipment. Therefore, maintaining the safe operation of cables is a vital task.

Theoretically, power cables are less affected by external environmental factors and human factors, and the reliability of safe operation is high. However, the long-term accumulated power cable operation experience and experimental research results have confirmed that power cable lines are prone to cable operation failures during the period of 1 to 5 years after they are put into operation.

The main causes of power cable failures are external force damage, manufacturing quality defects of cable accessories, cable installation quality defects or cable body manufacturing quality defects and other factors.

The situation of cable failure is more complicated. In order to shorten the time of fault finding and repairing and not affect the normal power supply, fast and effective detection methods must be adopted to find out the fault point quickly and accurately and carry out emergency repairs.

The power cable fault test is generally divided into two steps: one is "rough test" and the other is "fixed point". First, choose the correct test method according to the fault phenomenon, and measure the approximate range of the fault point, that is, "rough test"; then, use the equipment to determine the specific location of the fault point, that is, "fixed point".

The publication date is April 26, 1995, and the Chinese invention patent application with the publication number CN1101984A discloses a "high-voltage discharge method for detecting cable disconnection points". This method is to connect the output terminal of a high-voltage small current generator to On one side of the broken pair, the broken pair is shorted on the other side. The high-voltage electricity must produce a discharge phenomenon at the disconnection point, and the discharge phenomenon will produce sound. Use a radio with a probe to move the probe 3 along the cable sheath. When it moves to the place where there is a discharge sound, this position is the disconnection point.

However, this method can only adapt to short-distance and short-distance cable laying small-scale detection and fault finding (that is, the aforementioned "fixed-point" detection), its detection speed is slow, it is easily disturbed by the surrounding electromagnetic field, and has relatively high requirements for the detection environment and users. High, it is not suitable for long-distance cables, cables laid by direct burial, or places with large electromagnetic interference in the surrounding environment.

The date of announcement is April 8, 1992. The Chinese patent with the approval number CN1013618B discloses a "detection system and device for ground faults of electric power equipment", which installs two optical magnetic sensors separately at both ends of the cable section, The signal from the optical-magnetic sensor is transmitted to the optical-electrical conversion circuit connected to it through the optical fiber cable connected to it. The identification circuit judges whether a ground fault has occurred and where the fault is based on the output signal of the optical-electrical conversion circuit, and according to The magnetic value difference or phase or the combination of the two output signals of the light-to-electricity conversion circuit is used for judgment. Although it solves the detection problem of long-distance cable laying, the entire detection device involves a photomagnetic sensor and an optical fiber cable of the same length as the detected cable, and the implementation cost is relatively high. It is difficult for users to implement fault point detection for cables that have been laid.

Contents of the invention

The technical problem to be solved by the present invention is to provide a simple, practical, and low-cost cable fault prediction method that can quickly and initially measure the cable fault points of cables laid directly, directly buried, or through non-metallic pipes within a long distance. Point detection method and detection device.

The technical scheme of the present invention is: provide a kind of cable fault predetermined point detection method, it is characterized in that:

(1) Connect the output ends of the high-voltage DC pulse generation unit and the audio signal injection unit to one end of the discharge unit, and the other end of the discharge unit is connected to one end of the faulty cable;

(2) The high-voltage DC pulse generating unit discharges the faulty cable through the discharge unit, and ignites and maintains the arc at the fault point;

(3) The audio signal injection unit superimposes an audio pulsating DC current on the cable on the basis of the ignited arc during the time period when the arc is stable;

(4) Receive the magnetic field radiated by the above-mentioned audio pulsating DC current through the cable through an audio magnetic field receiving device moving along the cable laying path;

(5) According to the characteristics that there is a big difference in the amplitude of the audio magnetic field before and after the fault point, it is judged that the audio magnetic field receiving device is in front or behind the fault point, so as to quickly perform preliminary rough measurement and predetermined point detection on the cable fault point .

Wherein, an arc continuing unit is also connected to the output end of the high-voltage DC pulse generating unit, and the arc continuing unit supplements energy to the ignited arc to prolong the duration of the arc. The high-voltage DC pulse generating unit, the arc continuing unit and The audio signal injection units are connected in parallel or in series.

The running time of the audio signal injection unit is shorter than the time when the high-voltage direct current pulse generating unit and the arc-continuing unit cause an arc at the fault point of the cable.

The audio frequency pulsating direct current is an intermittent audio frequency pulsating direct current.

The present invention also provides a cable fault predetermined point detection device using the above detection method, including a signal generating part and a signal receiving part, the output end of the signal generating part is connected with one end of the faulty cable, and the signal receiving part can be connected along the cable. Laying path for movement, characterized in that: the signal generating part includes a high-voltage DC pulse generating unit, an arc continuation unit, an audio signal injection unit and a discharge unit, and the high-voltage DC pulse generation unit, an arc continuation unit and an audio signal injection unit After the output terminals of the discharge unit are connected in parallel or in series, they are connected to one end of the discharge unit, and the other end of the discharge unit is connected to one end of the fault cable; the high-voltage DC pulse generation unit discharges the fault cable and ignites an arc at the fault point; The arc continuation unit supplements energy to the ignited arc to prolong the duration of the arc; the audio signal injection unit superimposes an audio pulsating DC current on the cable during the time period when the arc is stable; the signal receiving part is a magnetic field Detection, amplification and display device.

Wherein, the high-voltage DC pulse generation unit includes a DC high-voltage generator 9, a high-voltage capacitor C1 and a current-limiting resistor R1; the output terminal of the DC high-voltage generator 9 is connected to one end of the high-voltage capacitor C1 and the current-limiting resistor R1, and the high-voltage capacitor C1 The other end of the current-limiting resistor R1 is connected to one end of the discharge unit; its DC high-voltage generator charges the high-voltage capacitor, and the current-limiting resistor plays a damping role on the discharge current of the high-voltage capacitor.

The arc continuation unit includes a DC power supply 10, a capacitor C2 and a unidirectional conduction device VD1; the audio signal injection unit includes a DC power supply 11, a high-power power electronic switch 12, a unidirectional conduction device VD5, and an audio square wave generator device 13 and control circuit 14; wherein, the capacitor C2 is connected to both ends of the DC power supply 10 in parallel, the output end of the DC power supply 10 is connected to one end of the unidirectional conduction device VD1, and the other end of the unidirectional conduction device VD1 is connected to one end of the discharge unit Connection; the output end of the DC power supply 11 is connected to the input end of the high-power power electronic switch 12, the output end of the high-power power electronic switch is connected to one end of the discharge unit through the unidirectional conduction device VD5, and the control circuit 14 is connected to the audio frequency square wave generator. 13 is connected to the control terminal of the high-power power electronic switching device 12; its DC power supply 10 charges the capacitor C2, and automatically supplies the current to the ignited arc through the unidirectional conduction device VD1, prolonging the duration of the arc; its unidirectional The pass device VD1 plays the role of one-way isolation; its DC power supply 11 and audio frequency square wave generator 13 are under the control of the high-power power electronic switch 12, superimposing and injecting an intermittent audio frequency into the cable on the basis of the ignited arc. Pulsating DC current; its one-way conduction device VD5 plays the role of one-way isolation; its high-power power electronic switch is controlled by an audio square wave generator and a control circuit to turn it on and off.

Alternatively, the arc continuation unit includes a DC power supply 10, a capacitor C2, and a one-way conduction device VD1; the audio signal injection unit includes a DC power supply 11, a high-power power electronic switch 12, one-way conduction devices VD3, VD5, audio Square wave generator 13 and control circuit 14; Wherein, DC power supply 10 and DC power supply 11 are connected in series, capacitor C2 and unidirectional conduction device VD1 are connected in parallel at the two ends of DC power supply 10; The input end of the switch 12 is connected, the output end of the high-power power electronic switch is connected to one end of the discharge unit through the one-way conduction device VD5, and the control circuit 14 is connected to the control end of the high-power power electronic switch device 12 through the audio square wave generator 13 The unidirectional conduction device VD3 is connected in parallel between the series connection point of the DC power supply 10 and the DC power supply 11 and the output end of the high-power power electronic switch 12; its DC power supply 10 charges the capacitor C2, and through the unidirectional conduction devices VD1, VD3 and VD5 automatically supplies current to the arc that has been ignited to prolong the duration of the arc; its unidirectional conduction device VD1 plays the role of unidirectional isolation; its DC power supply 11 and audio frequency square wave generator 13 are used in high-power power electronic switches Under the control of 12, an intermittent audio pulsating DC current is superimposed and injected into the cable on the basis of the ignited arc; its one-way conduction devices VD3 and VD5 play the role of one-way isolation, and its high-power power electronic switch is controlled by the audio side. A wave generator and a control circuit control its on and off.

Alternatively, the audio signal injection unit includes at least two groups of DC power sources 11A, 11B, and each group of DC power sources is correspondingly provided with a corresponding high-power power electronic switch, a one-way conduction device, an audio frequency square wave generator and a control circuit: wherein, the DC The power supplies 11A, 11B are set in series with the DC power supply 10 of the arc continuing unit, the output terminals of the DC power supplies 11A, 11B are respectively connected to the input terminals of the corresponding high-power power electronic switches, and the output terminals of the large-power power electronic switches are unidirectionally connected The device is connected to one end of the discharge unit, and each control circuit is connected to the control end of the corresponding high-power power electronic switching device through an audio frequency square wave generator.

Further, between the DC power supply 10 and the unidirectional conduction device VD1 or between the high-power power electronic switch and the unidirectional conduction device VD5, a current-limiting resistor R2 or R3 is also provided; wherein, the resistor R2 is used to prolong the duration of the arc Time: Resistor R3 is used to protect high-power power electronic switching devices.

Compared with prior art, the advantages of the present invention are:

1. Using the method of audio pulse signal superposition injection, the cable under test can generate an easily detectable audio current magnetic field before the fault point. When the user travels along the cable with a magnetic field signal receiver, he can clearly know whether the fault has been detected. Walking through the fault point, it can quickly and initially determine the fault point of various direct-laid, directly buried or pipe-laid cables;

2. The principle and method used are simple and practical, and can quickly determine the approximate location of the fault point in a large area, which can greatly shorten the fault finding time and processing workload of long-distance cable laying, and reduce the damage caused by power failure to users loss;

3. The manufacturing cost of the device is relatively low, easy to be accepted by users, and easy to popularize.

Description of drawings

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

Fig. 1 is detection step and method flowchart of the present invention;

Fig. 2 is a kind of connection schematic diagram of detection device of the present invention;

Fig. 3 is another connection schematic diagram of the detection device of the present invention;

Fig. 4 is another connection schematic diagram of the detection device of the present invention;

Fig. 5 is the waveform diagram of each point in Fig. 2;

Fig. 6 is the circuit diagram of audio frequency square wave generator embodiment;

Fig. 7 is the circuit diagram of control circuit embodiment;

Fig. 8 is a schematic diagram of waveforms at various points of the control circuit;

Fig. 9 is a circuit diagram of a direct current high voltage generator embodiment;

Figure 10 is a circuit diagram of an embodiment of a DC power supply.

In the figure, 1 is the detection device, 2 is the audio magnetic field signal receiver, 3 is the fault cable to be tested, 4 is the fault point, 5 is the high-voltage DC pulse generating unit, 6 is the continuous arc unit, 7 is the audio signal injection unit, 8 9 is a DC high-voltage generator, 10, 11, 11A, and 11B are DC power supplies, 12, 12A, and 12B are high-power power electronic switches, 13 is an audio frequency square wave generator, and 14 is a control circuit.

Detailed ways

Among Fig. 1, the present invention provides a kind of cable fault predetermined point detection method, and its concrete practice is as follows:

(1) Connect the output ends of a high-voltage DC pulse generating unit, an arc continuing unit and an audio signal injection unit in parallel, and connect them to one end of a discharge unit, and the other end of the discharge unit is connected to the phase line at one end of the faulty cable;

(2) The high-voltage DC pulse generating unit discharges the faulty cable through the discharge unit, and ignites and maintains the arc at the fault point;

(3) The arc continuation unit supplements energy to the arc that has been ignited to prolong the duration of the arc;

(4) The audio signal injection unit superimposes an audio pulsating DC current on the cable on the basis of the ignited arc during the time period when the arc is stable;

(5) Receive the magnetic field radiated by the above-mentioned audio pulsating DC current through the cable through an audio magnetic field receiving device moving along the cable laying path;

(6) According to the characteristics that the amplitude of the audio magnetic field before the fault point is much higher than the amplitude of the audio magnetic field after the fault point, it is judged that the audio magnetic field receiving device is in front or behind the fault point, so as to quickly conduct a preliminary rough analysis of the cable fault point Measure predetermined point detection.

The running time of the audio signal injection unit is shorter than the time when the high-voltage direct current pulse generating unit and the arc-continuing unit cause an arc at the fault point of the cable.

Its audio pulsating direct current is an intermittent audio pulsating direct current.

In Fig. 2, the cable fault predetermined point detection device adopting the detection method described in Fig. 1 includes a signal generating part 1 and a signal receiving part 2, the output end of its signal generating part is connected with an end of the faulty cable 3, and its signal receiving part can be connected along the The laying path of the cable is moved.

Wherein, the signal generating part includes a high voltage direct current pulse generating unit 5, an arc continuing unit 6, an audio signal injection unit 7 and a discharge unit 8, and the output ends of the high voltage direct current pulse generating unit, the arc continuing unit and the audio signal injection unit are connected in parallel or in series (this The figure is in parallel form), connected to one end of the discharge unit, the other end of the discharge unit is connected to one end of the faulty cable, and the fault point of the cable is represented by 4.

The high-voltage DC pulse generation unit discharges the fault cable and ignites the arc at the fault point; the arc continuation unit supplements energy to the ignited arc to prolong the duration of the arc; the audio signal injection unit During the period of stable existence, an audio frequency pulsating direct current is superimposed on the cable; the signal receiving part is a magnetic field detection, amplification and display device.

Specifically, the high-voltage direct-current pulse generation unit 5 includes a direct-current high-voltage generator 9, a high-voltage capacitor C1, and a current-limiting resistor R1; The other end is grounded, and the other end of the current limiting resistor R1 is connected to one end of the discharge unit.

Its DC high-voltage generator charges the high-voltage capacitor, and the current-limiting resistor plays a damping role on the discharge current of the high-voltage capacitor.

The arc continuation unit 6 includes a DC power supply 10 (for ease of understanding, it is represented by a battery symbol in the figure, the same below), a capacitor C2 and a unidirectional conduction device VD1; the audio signal injection unit 7 includes a DC power supply 11, a high-power power electronic switch 12, One-way conduction device VD5, audio frequency square wave generator 13 and control circuit 14; Wherein, capacitor C2 is connected in parallel with the two ends of DC power supply 10, and the output end of DC power supply 10 is connected with one end of one-way conduction device VD1, unidirectional conduction The other end of the device VD1 is connected to one end of the discharge unit; the output end of the DC power supply 11 is connected to the input end of the high-power power electronic switch 12, and the output end of the high-power power electronic switch is connected to one end of the discharge unit through the unidirectional conduction device VD5 , the control circuit 14 is connected to the control terminal of the high-power power electronic switching device 12 via the audio frequency square wave generator 13 .

Its DC power supply 10 charges the capacitor C2, and automatically supplies current to the arc that has been ignited through the unidirectional conduction device VD1, prolonging the duration of the arc; its unidirectional conduction device VD1 plays the role of one-way isolation; its DC power supply 11 and the audio square wave generator 13 under the control of the high-power power electronic switch 12, superimpose and inject a large-value intermittent audio pulsating DC current to the cable on the basis of the ignited arc; its unidirectional conduction device VD5 starts To the role of one-way isolation; its high-power power electronic switch is controlled by an audio square wave generator and a control circuit to turn it on and off.

The DC high voltage generator 9 may be composed of a power frequency high voltage transformer and a high voltage silicon stack, or an intermediate frequency or high frequency DC high voltage generator in the form of a switching power supply.

The DC high-voltage generator charges the high-voltage capacitor, and the current-limiting resistor plays a damping role on the discharge current of the high-voltage capacitor. The protection between units and the discharge of faulty cables are realized by the one-way conduction characteristics of the one-way conduction element inside the unit - the silicon stack.

The output voltage of the high voltage DC generator should be above 3000V. The DC high voltage generator in this figure has a negative polarity output.

Among them, the current-limiting resistor R1 can be selected from 10Ω to 1000Ω according to the output voltage of the high-voltage DC pulse generating unit.

The capacitance of the capacitor C2 in the arc continuation unit should be greater than that of C1, and the large capacity of C2 is beneficial to prolong the arc continuation time.

The high-power power electronic switch can be IGBT, high-power triode, MOS tube or other high-power power electronic switch devices, and its model selection is as follows:

IGBT: BSM75GB120DN2, BSM100GB120DN2, SKM 100 GAR 123D, FF100R12KS4 or FMG2G75US120;

High-power MOS tube: STE50DE100, IXFB80N50Q, IXFB38N100Q, IRFIB5N50L or IRFPS40N60K;

Shutdown SCR: 5SGA 06D4502.

The turn-on and turn-off of the high-power power electronic switch is controlled by an audio frequency square wave generator and a control circuit.

Its unidirectional conduction devices VD1-VD5 can be silicon stacks, diodes or thyristors.

The time control circuit in the control circuit controls the audio square wave generator to start running a few milliseconds after the discharge device (if the discharge device is controllable) is closed, or a current pulse detection device detects the high voltage DC pulse generation unit After the pulse current is output, start the time control circuit to make it control the audio frequency square wave generator to start running in several milliseconds when the arc is ignited.

After the audio square wave generator starts running for several milliseconds, the time control circuit controls it to stop working, and the high-power power electronic switch is in the off state before the audio square wave generator works and after it stops working.

The running time of the audio frequency square wave generator should be shorter than the time when the high-voltage DC pulse generating unit and the arc-continuing unit cause an arc at the fault point of the cable.

Between the DC power supply 10 and the unidirectional conduction device VD1 or between the high-power power electronic switch and the unidirectional conduction device VD5, a current-limiting resistor R2 or R3 is also provided; wherein, the resistor R2 is used to prolong the duration of the arc; Resistor R3 is used to protect high-power power electronic switching devices. According to the test results, both can use ohm-level resistors.

The discharge unit 8 is a high-voltage relay, a contact driven by an electromagnet or a discharge ball with an adjustable discharge gap, which belongs to the prior art and will not be described in detail here.

The signal receiving part is a magnetic field detection, amplification and display device, which belongs to the prior art and will not be described in detail here.

In this figure, the relationship between the continuous arc unit and the audio signal is essentially a superimposed relationship of current.

Through the above devices and their connections, an intermittent large-value audio pulsating DC current is injected into the cable to be tested. This audio current is short-circuited by an arc at the fault point 4 of the cable and does not continue to propagate forward. Through magnetic field detection, The amplification and display device receives the magnetic field radiated by the current through the cable. The amplitude of the audio magnetic field before the fault point is much higher than that after the fault point. By this method, it can be judged whether the magnetic field detection device is in front of the fault point. or rear.

In Fig. 3, the arc continuation unit and the audio signal injection unit are connected in series.

Its arc continuing unit includes DC power supply 10, capacitor C2 and unidirectional conduction device VD1; audio signal injection unit includes DC power supply 11, high-power power electronic switch 12, unidirectional conduction devices VD3, VD5, audio square wave generator 13 and control circuit 14.

Wherein, the DC power supply 10 and the DC power supply 11 are connected in series, and the capacitor C2 and the unidirectional conduction device VD1 are connected to both ends of the DC power supply 10 in parallel.

The output end of the DC power supply 11 is connected to the input end of the high-power power electronic switch 12, the output end of the high-power power electronic switch is connected to one end of the discharge unit through the unidirectional conduction device VD5, and the control circuit 14 is connected to the The control terminal of the high-power power electronic switching device 12 is connected.

The unidirectional conduction device VD3 is connected in parallel between the series connection point of the DC power supply 10 and the DC power supply 11 and the output end of the high-power power electronic switch 12 .

Its DC power supply 10 charges the capacitor C2, and automatically supplies current to the ignited arc through the unidirectional conduction devices VD1, VD3 and VD5, prolonging the duration of the arc; its unidirectional conduction device VD1 plays the role of one-way isolation .

Its DC power supply 11 and audio square wave generator 13 are under the control of high-power power electronic switch 12, superimpose and inject an intermittent audio frequency pulsating DC current to the cable on the basis of the ignited arc; its unidirectional conduction device VD3 and VD5 plays the role of one-way isolation; its high-power power electronic switch is controlled by an audio square wave generator and a control circuit to turn it on and off.

The rest are the same as in Figure 2.

In this figure, the arc-continuing unit and the audio signal are essentially a current/voltage superposition relationship.

The purpose of using the DC power supply 10 and 11 in series is to reduce the voltage and capacity of the DC power supply 11, reduce the volume of the entire device and the requirement for the DC power supply, and be more conducive to engineering and improve its practicability.

In Fig. 4, the audio signal injection unit adopts a two-stage series circuit structure, and the arc continuation unit and the audio signal injection unit are connected in series.

Its audio signal injection unit includes at least two groups of DC power supplies 11A, 11B, and each group of DC power supplies is correspondingly provided with a corresponding high-power power electronic switch, a one-way conduction device, an audio frequency square wave generator and a control circuit (for simplicity, not shown in the figure) out audio square wave generator and control circuit).

Among them, the DC power supplies 11A, 11B are set in series with the DC power supply 10 of the arc continuing unit, the output terminals of the DC power supplies 11A, 11B are respectively connected to the input terminals of the corresponding high-power power electronic switches, and the output terminals of the various power electronic switches are connected through The one-way conduction device is connected to one end of the discharge unit, and each control circuit is connected to the control end of the corresponding high-power power electronic switching device through the audio frequency square wave generator.

The rest are the same as those shown in Figure 2 or Figure 3.

Set up at least two sets of DC power supplies 11A and 11B, and each set of DC power supplies should be equipped with corresponding high-power power electronic switches, unidirectional conduction devices, audio frequency square wave generators and control circuits, the purpose of which is to reduce the resistance to high-power power electronic switches. To meet the voltage requirements, the voltage levels of the DC power supplies 11A and 11B are reduced, so as to reduce the volume and manufacturing cost of the entire device.

According to this idea, the continuous arc unit can also adopt the circuit structure of two or more DC power supplies connected in series to further reduce the requirements for the voltage and capacity of each group of DC power supplies. Those skilled in the art should easily It can be realized and will not be described here.

In FIG. 5 , the working waveform of each point of the device is illustrated by taking the circuit structure of FIG. 2 as an example, so as to help understand the working principle of the present invention.

Among them, A is the output voltage waveform diagram when the high-voltage DC pulse generating unit works alone, B is the output voltage waveform diagram when the arc continuation unit works alone, C is the output voltage waveform diagram when the audio signal injection unit works alone, D is each When the units work together, the signal voltage waveform diagram injected into the middle of the cable, E is the signal received by the signal receiver before the cable fault point, after resonance, filtering, and amplified signal waveform diagram, F is the signal receiver in the cable The received signal after the fault point, the signal waveform diagram after resonance, filtering and amplification.

It can be seen that the discharge time of A is extremely short, the discharge time of B is greatly extended, and the output of C is audio pulsating DC. The superposition of the three achieves the effect of D. By comparing E and F, it can be seen that the signal received by the magnetic field detection device is far away from the fault point. Stronger than the signal after the point of failure.

Fig. 6 is a kind of realization mode of audio frequency square wave generator 13, is formed oscillator circuit by time base integrated circuit 555 (IC number is U401 among the figure) and its peripheral circuit, its 3 pins output audio frequency square wave signal, and it is controlled by PORT1 The control port is controlled by an AND gate to allow or prohibit output. The final signal is output by PORT2. PORT1 is high-level (logic 1) to allow output, low-level (logic 0 to prohibit output), and PORT2 is low when output is prohibited. level.

U402 in the figure is a conventional AND gate circuit, and there are no special requirements for other components.

The audio square wave generator can adopt a conventional square wave generating circuit, and can also adopt a conventional sine wave generating circuit to obtain the required square wave signal after transformation/shaping, which belongs to the prior art and will not be described again.

Fig. 7 is a kind of realization mode of control circuit 10, and control circuit is composed of oscillator circuit by U501 time base integrated circuit 555, to control the closing or opening of discharge device 8, output high level (logic 1) to control the triggering of discharge device 8 The points are closed, outputting a low level (logic 0) to control the contacts of the discharge device 8 to separate. The time for outputting logic 1 is between 0.1 second and 1 second, and the time for outputting logic 0 is between 1 second and 10 seconds (see the waveform at point H in FIG. 8 ).

In addition, C503 and R504 constitute a differential circuit, VD501 controls only the positive polarity pulse to pass through, and converts the rising edge of the signal at point H into a positive polarity spike, and VT501 and R503 form an inverter circuit, which converts the positive polarity spike into a negative polarity Spike pulse (see waveform at point I in Figure 8). This sharp pulse triggers the monostable circuit 1 composed of the U502 time base integrated circuit 555, and outputs a positive polarity pulse with a fixed width (see the waveform at point J in FIG. 8 ). This signal is changed into a negative polarity pulse through the inverter composed of R506, VT502, and R507 (see the waveform at point K in Figure 8). The rising edge of this pulse is converted into a negative polarity spike through the differential circuit and one-way conduction circuit composed of C506, R508, and VD502 (see the waveform at point L in Figure 8). This sharp pulse triggers the monostable circuit 2 composed of U503 time base integrated circuit 555, and outputs a positive polarity pulse with a fixed width (see the waveform at point M in FIG. 8 ).

It can be seen that the function of the monostable circuit 1 is to generate the trigger signal of the monostable circuit 2. This trigger signal is several milliseconds later than the contact closure of the discharge device. The monostable circuit 2 generates the control signal of the audio square wave generator. The signal controls the audio frequency square wave generator to output for a few milliseconds and then stop the output. The time to stop the output must be before the contacts of the discharge device are separated.

FIG. 8 is a schematic diagram of the waveforms of each point of the control circuit, and its specific meaning has been described in the description of FIG. 7 .

Fig. 9 is an implementation of the DC high voltage generator 9. The input 220V AC mains voltage is boosted by the T101 high voltage power frequency transformer, the unidirectional conduction control is performed by the V101 silicon stack, and the current limiting protection is performed by the R101.

Figure 5 shows an implementation of the DC power supply. The input 220V AC mains is transformed and isolated by the T201 industrial frequency transformer, rectified by the B201 rectifier bridge, and current-limited by R201 for protection.

Field tests were carried out using the above methods and devices, and the test results are as follows:

serial number cable condition The actual position of the fault point from the starting point of the cable Scheduled point range Signal strength before fault point Signal strength after point of failure 1 Cable voltage level: 10KV. Overall length: 1200 meters Fault nature: Core wire to armor breakdown Fault resistance: 5M 1050 meters 2 meters front and rear 60dB 30dB 2 Voltage level: 10KV. Overall length: 560 meters Fault nature: Core wire to armor breakdown Fault resistance: 1M 360 meters 3 meters front and back 65dB 35dB 3 Voltage level: 600V. Total length: 210 meters Fault nature: Core wire to ground breakdown Fault resistance: 20K 90 meters 1.5 meters front and back 80dB 20dB

It can be seen from the above data that the present invention can quickly and initially measure the cable fault points of cables laid directly, directly buried or through pipes within a long-distance range. The signal strength contrast is obvious, which is easy for users to grasp and understand implement.

Since the present invention detects by injecting and superimposing audio pulsating DC current signals on the cable to be tested and detecting its current magnetic field, when the user walks along the cable with a magnetic field signal receiver, he can clearly know whether he has passed the fault For all kinds of cables laid directly, directly buried or through pipes, the approximate location of the fault point can be quickly judged in a large area, which can greatly shorten the fault finding time and processing workload of long-distance cable laying, and reduce Losses caused by power outages to users, the cost of making the device is relatively low, easy to be accepted and implemented by users, and easy to promote.

The invention can be widely used in the field of fault detection of various cables directly buried, laid through non-metallic pipes or cable tunnels.

Claims (10)

1. A cable fault presetting point detection method is characterized in that:

(1) connecting the output ends of the high-voltage direct current pulse generation unit and the audio signal injection unit to the first end of the discharge unit, and connecting the second end of the discharge unit to one end of the fault cable;

(2) the high-voltage direct-current pulse generation unit discharges the fault cable through the discharge unit, and an electric arc is ignited and maintained at the fault point of the fault cable;

(3) in a time period when the electric arc stably exists, an audio frequency pulsating direct current is superposed on the cable on the basis of the ignited electric arc by an audio frequency signal injection unit;

(4) receiving the magnetic field radiated by the audio pulsating direct current through the cable by an audio magnetic field receiving device moving along the cable laying path;

(5) according to the characteristic that the amplitude of the audio magnetic field is greatly different before and after the fault point, the audio magnetic field receiving device is judged to be positioned in front of or behind the fault point, and therefore preliminary rough detection preset point detection is rapidly carried out on the cable fault point.

2. The method for detecting the cable fault preset point according to claim 1, wherein an arc continuing unit is connected to an output end of the high-voltage direct current pulse generating unit, the ignited electric arc is supplemented with energy by the arc continuing unit, the existence time of the electric arc is prolonged, and the high-voltage direct current pulse generating unit and the arc continuing unit are connected with the audio signal injection unit in parallel or in series.

3. The cable fault predetermined point detecting method as claimed in claim 2, wherein the operating time of the audio signal injecting unit is shorter than the time when the high voltage direct current pulse generating unit and the arc continuing unit induce an arc at the cable fault point.

4. The method of cable fault pre-determined point detection as claimed in claim 1, wherein said audio pulsating direct current is an intermittent audio pulsating direct current.

5. A cable failure predetermined point detecting apparatus using the detecting method according to claim 1, comprising a signal generating section whose output terminal is connected to an end of a failed cable and a signal receiving section which is movable along a running path of the cable, characterized in that:

the signal generating part comprises a high-voltage direct-current pulse generating unit, a continuous arc unit, an audio signal injection unit and a discharging unit, wherein the output ends of the high-voltage direct-current pulse generating unit, the continuous arc unit and the audio signal injection unit are connected in parallel or in series and then connected to the first end of the discharging unit, and the second end of the discharging unit is connected with one end of a fault cable;

the high-voltage direct-current pulse generating unit discharges to a fault cable and ignites an electric arc at a fault point of the fault cable;

the arc continuation unit supplements energy to the ignited arc, and prolongs the arc duration;

the audio signal injection unit superposes an audio pulsating direct current on the cable in a time period when the electric arc stably exists;

the signal receiving part is a magnetic field detection, amplification and display device.

6. The cable fault pre-determined point detection device of claim 5, wherein the high voltage direct current pulse generation unit comprises a direct current high voltage generator (9), a high voltage capacitor C1 and a current limiting resistor R1:

the output end of the direct-current high-voltage generator (9) is connected with one end of a high-voltage capacitor C1 and one end of a current-limiting resistor R1, the other end of the high-voltage capacitor C1 is grounded, and the other end of the current-limiting resistor R1 is connected with the first end of the discharge unit;

the direct current high voltage generator charges the high voltage capacitor, and the current limiting resistor plays a damping role in discharging current of the high voltage capacitor.

7. The cable fault pre-determined point detection device as recited in claim 5, wherein said arc continuing unit comprises a first dc power source (10), a capacitor C2 and a one-way conducting device VD 1; the audio signal injection unit comprises a second direct-current power supply (11), a high-power electronic switch (12), a one-way conduction device VD5, an audio square wave generator (13) and a control circuit (14);

the capacitor C2 is connected in parallel at two ends of the first direct current power supply (10), the output end of the first direct current power supply (10) is connected with one end of the one-way conduction device VD1, and the other end of the one-way conduction device VD1 is connected with the first end of the discharge unit;

the output end of the second direct current power supply (11) is connected with the input end of the high-power electronic switch (12), the output end of the high-power electronic switch is connected with the first end of the discharge unit through a one-way conduction device VD5, and the control circuit (14) is connected with the control end of the high-power electronic switch device (12) through an audio square wave generator (13);

a first direct current power supply (10) charges a capacitor C2, and automatically supplements current to the ignited electric arc through a one-way conduction device VD1, so that the storage time of the electric arc is prolonged; the one-way conducting device VD1 plays a role in one-way isolation;

a second direct current power supply (11) and an audio square wave generator (13) are controlled by a high-power electronic switch (12), and an intermittent audio pulsating direct current is injected into the cable in a superposition mode on the basis of an ignited arc; the one-way conducting device VD5 plays a role in one-way isolation; the high-power electronic switch is controlled to be switched on and off by an audio square wave generator and a control circuit.

8. The cable fault pre-determined point detection device as recited in claim 5, wherein said arc continuing unit comprises a first dc power source (10), a capacitor C2 and a one-way conducting device VD 1; the audio signal injection unit comprises a second direct-current power supply (11), a high-power electronic switch (12), unidirectional conducting devices VD3 and VD5, an audio square-wave generator (13) and a control circuit (14);

the first direct-current power supply (10) is connected with the second direct-current power supply (11) in series, and the capacitor C2 and the one-way conduction device VD1 are connected to two ends of the first direct-current power supply (10) in parallel; the output end of the second direct current power supply (11) is connected with the input end of the high-power electronic switch (12), the output end of the high-power electronic switch is connected with the first end of the discharge unit through a one-way conduction device VD5, and the control circuit (14) is connected with the control end of the high-power electronic switch device (12) through an audio square wave generator (13);

the one-way conduction device VD3 is connected in parallel between the serial connection point of the first direct current power supply (10) and the second direct current power supply (11) and the output end of the high-power electronic switch (12);

a first direct current power supply (10) charges a capacitor C2, and automatically supplements current to the ignited electric arc through unidirectional conducting devices VD1, VD3 and VD5 so as to prolong the storage time of the electric arc; the one-way conducting device VD1 plays a role in one-way isolation;

a second direct current power supply (11) and an audio square wave generator (13) are controlled by a high-power electronic switch (12), and an intermittent audio pulsating direct current is injected into the cable in a superposition mode on the basis of an ignited arc; the one-way conducting devices VD3 and VD5 play a role in one-way isolation; the high-power electronic switch is controlled to be switched on and off by an audio square wave generator and a control circuit.

9. The cable fault presetting point detecting device of claim 7 or 8, wherein the second direct current power supply comprises at least two groups of second direct current power supplies A, B, each group of direct current power supplies is correspondingly provided with a corresponding high-power electronic switch, a one-way conducting device, an audio square wave generator and a control circuit;

the second direct current power supply A, B is connected in series with the first direct current power supply (10) of the arc continuation unit, the output ends of the two groups of second direct current power supplies A, B are respectively connected with the input ends of the corresponding high-power electronic switches, the output end of each high-power electronic switch is connected with the first end of the discharge unit through a one-way conduction device, and each control circuit is connected with the control end of the corresponding high-power electronic switch through an audio square wave generator.

10. The cable fault prefixed point detecting device according to claim 7 or 8, characterized in that a current limiting resistor R2 or R3 is provided between said first dc power source (10) and a unidirectional conducting device VD1 or between the high power electronic switch and a unidirectional conducting device VD 5; wherein,

the resistor R2 is used for prolonging the existence time of the arc;

the resistor R3 is used to protect high power electronic switching devices.

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