CN102288883A - Oscillation wave partial discharge identifying and positioning method for asynchronous double-end power cable - Google Patents

Abstract

The invention discloses an oscillation wave partial discharge identifying and positioning method for an asynchronous double-end power cable. The method disclosed by the invention comprises the following specific steps: respectively installing oscillation wave partial discharge signal acquisition devices at the two ends of the cable; obtaining the voltage and partial discharge capacity signals at the two ends of the detected cable through data acquisition; recording and converting the corresponding data to obtain a waveform file which is needed for failure positioning; calling a partial discharge positioning algorithm to carry out the failure positioning; and computing the accurate position of a failure point generating partial discharge signals. The positioning analysis result obtained by the invention is more accurate; the error rate is small; the wave velocity does not need to be known, thereby reducing the errors caused by computing the wave velocity; the excessive manual intervention is needed; the problems of large data quantity, inaccuracy in positioning and the like because different pulses under the voltage of each experiment are matched are avoided; and the rapid and accurate failure positioning course of the method is beneficial to the timely repair of faulty lines and the reduction of loss caused by power failure.

Description

Recognition and location method of oscillatory wave partial discharge in asynchronous double-ended power cable

technical field

The invention belongs to the field of power systems, relates to power system signal processing application technology, in particular to an asynchronous double-ended power cable oscillation wave partial discharge identification and positioning method.

Background technique

Power cable fault location is an important measure to ensure the safe and economical operation of the power grid. Due to the concealment of power cable lines and the limitations of detection equipment, the rapid and accurate location and search technology of fault points is not yet perfect.

At present, there are mainly the following methods used in power cable fault location at home and abroad: traveling wave fault location, energy search algorithm fault location, double-terminal traveling wave location method and GPS fault traveling wave location method, etc. Among them, the fault location of the traveling wave method needs to match the incident wave and the reflected wave. Since the signals collected during the transmission of the cable include the incident wave, the reflected wave, the reflected wave of the incident wave, the reflected wave of the reflected wave and other interference Signal, so the incident wave and reflected wave generated by the same partial discharge point are difficult to match correctly; while the positioning method based on the energy search algorithm, the positioning error is centimeter level, but when the partial discharge signal propagation path occurs refraction and reflection, The effectiveness of this positioning method is poor; the double-terminal traveling wave positioning method is based on the initial traveling wave generated by the detection of faults at both ends of the line, and the fault distance is obtained by calculation using the time difference of the traveling wave arriving at both ends and the wave velocity. The main defects of the method are: The problem of time synchronization must be solved; the GPS fault traveling wave positioning method is an ideal time synchronization technology. Using the synchronous clock output of GPS, the time synchronization of the positioning devices at both ends is accurate to one microsecond. Communication link and GPS system to achieve time synchronization, the investment cost is relatively large, and when used in oscillatory wave signal acquisition devices, it needs to be done indoors, and indoor GPS signals are weak or even unreceivable.

All of the above methods have measurement errors and large limitations to varying degrees, difficulty in matching incident waves and reflected waves, inability to determine the precise position of partial discharge in power cables, and high costs, which limit their application in the detection of partial discharge in power cable oscillatory waves. further applications in the field.

Contents of the invention

The object of the present invention is to address the deficiencies of the above-mentioned prior art, and provide a method for identifying and locating partial discharge of an asynchronous double-ended power cable oscillating wave. By installing different partial discharge signal detection devices at both ends of the cable to be detected, the positioning device Detect the arrival time of the traveling wave signal, and then process all the time information by the fault traveling wave location master station, and calculate the partial discharge location by calculating the processed time information according to the traveling wave method.

An asynchronous double-ended power cable oscillatory wave partial discharge identification and location method, including the following stages:

(1) Preparation stage: Connect both ends of the cable to be tested to the oscillatory wave partial discharge signal acquisition device, and the partial discharge signal acquisition device records the original waveform and reflected waveform generated by the cable, and displays the recorded data information in real time;

(2) Signal acquisition stage: excite the fault point of the cable to be tested to generate a partial discharge signal, and the oscillatory wave partial discharge signal acquisition device collects the partial discharge signal generated by the fault point of the cable;

(3) Partial discharge signal location stage: filter the collected partial discharge signal, call the partial discharge location algorithm, and calculate the location of the partial discharge signal.

The oscillating wave partial discharge signal acquisition device of the present invention includes an A-end acquisition device and a B-end acquisition device; the A-end acquisition device is controlled by a switch, and the B-end acquisition device is triggered by a level mode.

In the stage (2) of the present invention, the process of exciting the fault point to generate the partial discharge signal is: using a high-voltage program-controlled DC power supply, applying an experimental voltage to the oscillatory wave partial discharge signal acquisition device, charging the resonant circuit, and passing through the equipment inductance and the cable capacitance to be tested Resonance occurs, a damped oscillation voltage is generated at both ends of the cable to be tested, the fault point is excited to generate a partial discharge signal, and the partial discharge signal is transmitted to both ends of the cable.

The signal acquisition process of the A-end acquisition device of the present invention is as follows: the partial discharge signal generated by the fault point is divided into two paths through the voltage divider and then enters the A-end acquisition device, one of which is filtered and directly enters the A-end acquisition device, and the other is filtered. All the way to the end of the cable transmission, total reflection occurs at the end of the cable, and then transmitted to the A-end acquisition device again, after the signal is converted by the coupler, it enters the A-end acquisition device. Since the waveform will be attenuated, scattered, reflected, etc. during the transmission of the cable, after a certain distance of transmission, after attenuation, the amplitude of the waveform corresponding to the partial discharge signal will decrease and the width will become wider. The amplitude of the resulting reflected wave is smaller than that of the incident wave, and the frequency becomes lower.

The signal acquisition process of the terminal B acquisition device of the present invention is as follows: the partial discharge signal generated at the fault point is transmitted to the cable B terminal acquisition device, and when the signal amplitude is large enough, the acquisition device at the B terminal is triggered to perform voltage division and coupling processing , and record the transmission distance corresponding to the waveform.

The signal collected by the terminal A collection device of the present invention is divided into two channels, one of which is a partial discharge signal generated by a fault point, and the other is a continuous signal including incident waves and reflected waves.

The partial discharge localization algorithm described in the present invention comprises the following steps:

(1) Initialize, filter the signal collected by the partial discharge signal collection device;

Find the pulse pair and find the time difference △T _i of a single partial discharge signal: According to the original waveform and reflected waveform of the A terminal and the B terminal recorded by the partial discharge signal acquisition device, find a pair of incident wave and reflected wave waveform in the A terminal The matching B-terminal waveform determines that this group of waveforms is produced by the same partial discharge position as a pulse pair i ; determine the time t1 and t2 corresponding to the incident wave and the reflected wave in the waveform file collected by the A-terminal acquisition device, and determine the B-terminal According to the time t3 corresponding to the waveform in the waveform file collected by the acquisition device, the displacement of the i -th pulse pair is determined according to t1, t2 and t3, that is, the time difference △T _i of a single partial discharge signal. The calculation formula is as follows:

;

(3) Analyze m sets of data of the experimental voltage under this level to obtain m sets of data △T ₁ , △T ₂ , △T ₃ ,..., △T _m ;

(4) Determine whether the data under the voltage level has been analyzed. If the analysis is not completed, analyze the next set of data, and perform steps (2) and (3) in sequence; if the analysis is completed, perform step (5);

(5) Calculate the time difference △T of partial discharge under the experimental voltage: remove the time points that do not meet the requirements from the data obtained in step (3) through the method of aggregation, and obtain the time difference corresponding to n groups of pulse pairs as △T ₁ , △ T ₂ , △T ₃ ,..., △T _n , carry out statistical processing to obtain the average value △T , the calculation formula is as follows:

；

;

(5) Time synchronization processing: The △T obtained in step (4) shifts the signal of the B-end acquisition device to obtain the signal of the actual transmission distance. The time before the shift is t', and the time after the shift is t=t' + △T ;

(7) Determine the fault location by calculation: the total length of the cable is L, the length L1 of the connecting cable between the acquisition device and the beginning of the cable is negligible, the length of the fault point from the acquisition device at end A is x, and the acquisition device at end B collects the waveform The corresponding transmission distance is L-x, then the transmission distance of the incident wave is x+L1, and the transmission distance of the reflected wave: 2L-x+L1; find the signal corresponding to the amplitude at the time point t in the signal collected by the B-end collection device Waveform, which is the partial discharge signal generated by the fault location, through

，

，可得：，

,

,Available: ,

； The partial discharge position is obtained by calculation:

;

(8) Determine whether the analysis of the test data is complete, if the analysis is complete, then end this cycle; if not, execute step (2) and continue to search for pulse pairs.

Compared with the prior art, the present invention has the following advantages:

(1) The present invention realizes double-terminal quasi-synchronization by converting the signals collected at both ends, without costly and synchronous devices, and without timing, so there is no timing error caused by non-synchronization in the GPS double-terminal positioning method;

(2) The invention has high measurement accuracy, good anti-interference performance, and strong anti-noise ability: the power cable partial discharge location algorithm based on asynchronous double-ended detection overcomes the shortcomings of single-ended measurement, can determine the real partial discharge signal, and effectively eliminate some Interference phenomena such as reflected waves of reflected waves and reflected waves of other incident waves;

(3) The waveform obtained by the oscillating wave signal acquisition device in the present invention is a steady-state continuous wave with stable energy, so the detection is easy and the waveform length is limited. After the oscillating voltage decays, the signal acquisition ends;

(4) The positioning method of the present invention is simple and convenient, and can be applied to occasions where the probe, the transceiver unit and the processing unit are wired or wirelessly connected. Even non-professional technicians can quickly master its usage;

(5) The present invention can be used not only for fault detection of running cables, but also for testing and detection of cables leaving the factory;

(6) Since the measurement accuracy of the present invention is less affected by the measurement environment, and the measurement accuracy can be improved by increasing the sampling rate, the technology is feasible and has strong applicability.

Description of drawings

Fig. 1 is a flow chart of the operating steps of the method for identifying and locating partial discharges of an asynchronous double-ended power cable oscillatory wave according to the present invention.

Fig. 2 is a schematic diagram of the connection mode between the oscillatory wave partial discharge signal acquisition device and the cable to be tested in the method of the present invention.

Fig. 3 is a flow chart of the partial discharge identification and location method of the present invention.

Detailed ways

The present invention will be further explained below in conjunction with the accompanying drawings and embodiments, but the protection scope of the present invention is not limited thereto.

Fig. 1 is the flow chart of the operation steps of the method of the present invention, as shown in Fig. 1, the asynchronous double-ended power cable oscillation wave partial discharge identification and location method of the present invention includes the following stages:

(1) Preparation stage: Connect both ends of the cable to be tested to the oscillatory wave partial discharge signal acquisition device, and the partial discharge signal acquisition device records the original waveform and reflected waveform generated by the cable, and displays the recorded data information in real time;

(2) Signal acquisition stage: excite the fault point of the cable to be tested to generate a partial discharge signal, and the oscillatory wave partial discharge signal acquisition device collects the partial discharge signal generated by the fault point of the cable;

(3) Partial discharge signal location stage: filter the collected partial discharge signal, call the partial discharge location algorithm, and calculate the location of the partial discharge signal.

As shown in Figure 2, the asynchronous double-terminal power cable oscillation wave partial discharge identification and positioning method of the present invention is to connect the oscillation wave partial discharge signal acquisition device at the A end and the B end of the cable to be tested at the same time, and the A end acquisition device passes the switch Control, the B-end acquisition device is triggered by level mode. The process of stimulating the fault point to generate the partial discharge signal is as follows: using the high-voltage program-controlled DC power supply, applying the experimental voltage to the oscillatory wave partial discharge signal acquisition device, charging the resonant circuit, and resonating with the cable capacitance to be tested through the equipment inductance. The damped oscillation voltage is generated at the end, the fault point is excited to generate a partial discharge signal, and the partial discharge signal is transmitted to both ends of the cable.

The signal acquisition process of the A-end acquisition device is as follows: the partial discharge signal generated by the fault point is divided into two routes through the voltage divider and then enters the A-end acquisition device. Transmission, total reflection occurs at the end of the cable, and then transmitted to the A-end acquisition device again, after the signal is converted by the coupler, it enters the A-end acquisition device. Therefore, the signal collected by the A terminal acquisition device is divided into two channels, one of which is the partial discharge signal generated by the fault point, and the other is a continuous signal including incident waves and reflected waves

The signal acquisition process of the B-end acquisition device is: the partial discharge signal generated by the fault point is transmitted to the cable B-end acquisition device. When the amplitude of the signal is large enough, the B-end acquisition device is triggered to perform voltage division and coupling processing, and the recorded The data information is displayed in real time, the waveform file required for positioning is obtained, and the transmission distance corresponding to the waveform is recorded.

As shown in Figure 3, the partial discharge localization algorithm of the present invention comprises the following steps:

(1) Initialize, filter the signal collected by the partial discharge signal collection device;

(2) Find the pulse pair and find the time difference △T _i of a single partial discharge signal: According to the original waveform and reflected waveform of the A terminal and the B terminal recorded by the partial discharge signal acquisition device, find a pair of incident waves and the reflected waveforms in the A terminal. The B end waveform that the reflected wave waveform matches determines that this group of waveforms is produced by the same partial discharge position, as a pulse pair i ; determine the time t1 and t2 corresponding to the incident wave and the reflected wave in the waveform file collected by the A end acquisition device, Determine the time t3 corresponding to the waveform in the waveform file collected by the B-end acquisition device, and determine the displacement of the i -th pulse pair, that is, the time difference ΔT _i of a single partial discharge signal, according to t1, t2 and t3. The calculation formula is as follows:

;

(3) Analyze m sets of data of the experimental voltage under this level to obtain m sets of data △T ₁ , △T ₂ , △T ₃ ,..., △T _m ;

(4) Determine whether the data under the voltage level has been analyzed. If the analysis is not completed, analyze the next set of data, and perform steps (2) and (3) in sequence; if the analysis is completed, perform step (5);

(5) Calculate the time difference △T of partial discharge under the experimental voltage: remove the time points that do not meet the requirements from the data obtained in step (3) through the method of aggregation, and obtain the time difference corresponding to n groups of pulse pairs as △T ₁ , △ T ₂ , △T ₃ ,..., △T _n , carry out statistical processing to obtain the average value △T , the calculation formula is as follows:

;

(6) Time synchronization processing: The △T obtained in step (4) shifts the signal of the B-end acquisition device to obtain the signal of the actual transmission distance. The time before the shift is t', and the time after the shift is t=t' + △T ;

，

，可得：

，通过计算得到局部放电位置：； (7) Determine the fault location by calculation: the total length of the cable is L, the length L1 of the connecting cable between the acquisition device and the beginning of the cable is negligible, the length of the fault point from the acquisition device at end A is x, and the acquisition device at end B collects the waveform The corresponding transmission distance is Lx, then the transmission distance of the incident wave is x+L1, and the transmission distance of the reflected wave: 2L-x+L1; find the signal corresponding to the amplitude at the time point t in the signal collected by the B-end collection device The waveform, which is the partial discharge signal generated at the fault location, is passed through:

,

,Available:

, the partial discharge position is obtained by calculation: ;

(8) Determine whether the analysis of the test data is complete, if the analysis is complete, then end this cycle; if not, return to step (2) and continue to search for pulse pairs.

Claims (7)

1. An asynchronous double-ended power cable oscillatory wave partial discharge identification and location method is characterized in that, comprising the following stages: (1) Preparation stage: Connect both ends of the cable to be tested to the oscillatory wave partial discharge signal acquisition device, and the partial discharge signal acquisition device records the original waveform and reflected waveform generated by the cable, and displays the recorded data information in real time; (2) Signal acquisition stage: excite the fault point of the cable to be tested to generate a partial discharge signal, and the oscillatory wave partial discharge signal acquisition device collects the partial discharge signal generated by the fault point of the cable; (3) Partial discharge signal location stage: filter the collected partial discharge signal, call the partial discharge location algorithm, and calculate the location of the partial discharge signal. 2. The asynchronous double-terminal power cable oscillatory wave partial discharge identification and location method according to claim 1 is characterized in that, said oscillatory wave partial discharge signal acquisition device comprises an A-end acquisition device and a B-end acquisition device; said A The end acquisition device is controlled by a switch, and the B end acquisition device is triggered by a level mode. 3. The asynchronous double-terminal power cable oscillation wave partial discharge identification and location method according to claim 1 or 2, characterized in that in stage (2), the process of exciting the fault point to generate a partial discharge signal is: using high voltage The program-controlled DC power supply applies the experimental voltage to the oscillating wave partial discharge signal acquisition device, charges the resonant circuit, resonates with the capacitance of the cable to be tested through the inductance of the equipment, and generates a damped oscillation voltage at both ends of the cable to be tested, and the fault point is excited to generate partial discharge Signal, partial discharge signal is transmitted to both ends of the cable. 4. The asynchronous double-terminal power cable oscillating wave partial discharge identification and location method according to claim 3, characterized in that, the signal acquisition process of the A-end acquisition device is: the partial discharge signal generated by the fault point passes through the voltage divider After the voltage is divided, it is divided into two paths to enter the A-end acquisition device, one of which is filtered and directly enters the A-end acquisition device, and the other is transmitted to the end of the cable, where total reflection occurs at the end of the cable, and then transmitted to the A-end acquisition device again, passing through the coupler After the signal is converted, it enters the A terminal acquisition device. 5. The asynchronous double-terminal power cable oscillating wave partial discharge identification and location method according to claim 4, characterized in that, the signal acquisition process of the B-end acquisition device is: the partial discharge signal generated by the fault point is sent to the cable B-end The acquisition device transmits. When the amplitude of the signal is large enough, the acquisition device at the B end is triggered to perform voltage division and coupling processing, and record the transmission distance corresponding to the waveform. 6. The asynchronous double-terminal power cable oscillating wave partial discharge identification and location method according to claim 5, characterized in that the signal collected by the A-end acquisition device is divided into two paths, one of which is the partial discharge generated by the fault point signal, and the other is a continuous signal that includes incident waves and reflected waves. 7. The asynchronous double-ended power cable oscillation wave partial discharge identification and location method according to any one of claims 1 to 6, wherein the partial discharge location algorithm comprises the following steps: (1) Initialize, filter the signal collected by the partial discharge signal collection device; (2) Find the pulse pair and find the time difference △T _i of a single partial discharge signal: According to the original waveform and reflected waveform of the A terminal and the B terminal recorded by the partial discharge signal acquisition device, find a pair of incident waves and the reflected waveform in the A terminal. The B terminal waveform that the reflected wave waveform matches determines that this group of waveforms is produced by the same partial discharge position, as a pulse pair i ; determine the time t1 and t2 corresponding to the incident wave and the reflected wave in the waveform file collected by the A terminal acquisition device, Determine the time t3 corresponding to the waveform in the waveform file collected by the B-end acquisition device, and determine the displacement of the i -th pulse pair according to t1, t2 and t3, that is, the time difference △T _i of a single partial discharge signal. The calculation formula is as follows:

; (3) Analyze m sets of data of the experimental voltage under this level to obtain m sets of data △T ₁ , △T ₂ , △T ₃ ,..., △T _m ; (4) Determine whether the data under the voltage level has been analyzed. If the analysis is not completed, analyze the next set of data, and perform steps (2) and (3) in sequence; if the analysis is completed, perform step (5); (5) Calculate the time difference △T of partial discharge under the experimental voltage: remove the time points that do not meet the requirements from the data obtained in step (3) through the method of aggregation, and obtain the time difference corresponding to n groups of pulse pairs as △T ₁ , △ T ₂ , △T ₃ ,..., △T _n , carry out statistical processing to obtain the average value △T , the calculation formula is as follows:

; (6) Time synchronization processing: The △T obtained in step (4) shifts the signal of the B-end acquisition device to obtain the signal of the actual transmission distance. The time before the shift is t', and the time after the shift is t=t' + △T ; (7) Determine the fault location by calculation: the total length of the cable is L, the length L1 of the connecting cable between the acquisition device and the beginning of the cable is negligible, the length of the fault point from the acquisition device at end A is x, and the acquisition device at end B collects the waveform The corresponding transmission distance is Lx, then the transmission distance of the incident wave is x+L1, and the transmission distance of the reflected wave: 2L-x+L1; find the signal corresponding to the amplitude at the time point t in the signal collected by the B-end collection device The waveform, which is the partial discharge signal generated at the fault location, is passed through:

,

,Available:

, the partial discharge position is obtained by calculation:

; (8) Determine whether the analysis of the test data is complete, if the analysis is complete, then end this cycle; if not, return to step (2) and continue to search for pulse pairs.

Images