CN106940413A - The short trouble section determination methods and device of high pressure long cable circuit - Google Patents

Abstract

The invention relates to a method for judging a short-circuit fault section of a high-voltage long cable line, which is used for judging in which cable cross-connection section a short-circuit fault occurs in a high-voltage long cable line, and each cable cross-connection section includes several sections of wire cores directly Connected to form a three-phase cable line, and the metal sheath is cross-connected to form a cable section with a three-section sheath connection path. The method for judging the short-circuit fault section is: separately detect the current at both ends of the three-section sheath connection path in each cable cross-connection section Direction, if the current direction at both ends of any section of the sheath connection path in a certain cable cross-connection section is opposite, a short-circuit fault occurs in the cable cross-connection section. The invention uses the current direction at both ends of the cable cross-connection section as a criterion to judge whether a short-circuit fault occurs in the cable cross-connection section, which can realize on-line monitoring, and can quickly and timely find out the fault section after a fault occurs.

Description

Method and device for judging short-circuit fault section of high-voltage long cable line

technical field

The invention relates to a method and a device for judging in which cable cross-connection section a short-circuit fault occurs in a high-voltage long cable line.

Background technique

Distance protection is widely used in high-voltage transmission lines. The protection principle based on parameter identification uses the parameters that change in the system after a fault to form protection criteria. The high-voltage long cable line has the characteristics of long transmission distance, large transmission capacity, obvious distribution parameter characteristics, multiple complete cable cross-connection sections, and complex line channel environment, which will significantly affect the operation performance of the distance protection algorithm. Since the measured impedance is no longer proportional to the fault distance, the protection range of the traditional distance protection algorithm will be reduced. In practical applications, the distance protection using line impedance still has the situation that the calculation of line impedance is inaccurate and the information of line length is incomplete.

The traveling wave method is another method widely used for fault location of overhead lines or cable lines. This method detects the propagation time of the transient traveling wave on the fault line between the bus and the fault point for fault location. Since the propagation speed of the transient traveling wave is close to the speed of light, the fault location mode based on the traveling wave method has noise elimination and The wave head is extracted at all times. In addition, multiple cross-connection sections and complex line channel environments cause the wave velocity of long cable lines to be inconsistent and wave impedance to be discontinuous. This method is difficult to apply to actual long cable lines.

Contents of the invention

The purpose of the present invention is to provide a method for judging the short-circuit fault section of the high-voltage long cable line, which is suitable for long-voltage long cable lines and can quickly and conveniently determine which cable cross-connection section the short-circuit fault occurs in.

In order to achieve the above object, the technical scheme adopted in the present invention is:

A method for judging a short-circuit fault section of a high-voltage long cable line, which is used to judge in which cable cross-connection section a short-circuit fault occurs in a high-voltage long cable line composed of several cable cross-connection sections, and each of the cable cross-connection sections Each interconnection section includes several sections of wire cores that are directly connected to form a three-phase cable line, and metal sheaths that are cross-connected to form a three-section sheath connection path. The current direction at both ends of the sheath connection path of the three sections in the interconnection section, if the current direction at both ends of the sheath connection path in any one of the cable cross-interconnection sections is opposite, then in the cable cross-interconnection section A short circuit fault has occurred.

Preferably, collect the current signals at both ends of the three sections of the sheath connection path in each of the cable cross-connection sections, and perform fast Fourier transformation on the current signals to obtain the phase angle of the current signals; The phase angle of the current signal at both ends of each section of the sheath connection path is subjected to a phase difference calculation, so as to determine whether the current direction at the two ends of each section of the sheath connection path is opposite.

Preferably, when the phase angle difference of the current signals at both ends of any section of the sheath connection path is within the phase allowable range centered at ±180°, it is judged that the current direction at the two ends of the sheath connection path of the section is opposite .

Preferably, the phase allowable range is (120°, 240°)∪(-240°, -120°).

The present invention also provides a short-circuit fault section judging device adopting the short-circuit fault section judging method of the above-mentioned high-voltage long cable line. A plurality of current transformers that describe the current signals at both ends of the sheath connection path, a host that is connected to each of the current transformers and judges whether a short-circuit fault occurs in each of the cable cross-connection sections, and the host communicates remotely with the monitoring center connect.

Preferably, both ends of each section of the sheath connection path are connected to a grounding box, and the current transformer is arranged at the grounding box.

Preferably, the host performs remote communication with the monitoring center via the GPRS/3G/4G network through an antenna.

Due to the use of the above technical solutions, the present invention has the following advantages compared with the prior art: the present invention uses the current direction at both ends of the cable cross-connection section as a criterion to judge whether a short-circuit fault occurs in the cable cross-connection section, which can realize online monitoring , can quickly and timely find out the fault section after the fault occurs.

Description of drawings

Accompanying drawing 1 is the schematic diagram of the mechanism of the power system.

detailed description

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

Embodiment 1: A simple power system as shown in Figure 1, which consists of a power supply - a transmission line - a load, wherein the transmission line adopts a high-voltage long cable line. A long high-voltage cable line consists of a number of connected cable cross-connection sections, and each cable cross-connection section includes several cable sections. In each cable cross-connection section, the cores of the cable sections are directly connected to form a three-phase cable line, and the metal sheaths are cross-connected to form three sections of sheath connection paths. In the specific example shown in FIG. 1 , the high-voltage long cable line includes three complete cable cross-connection sections, which are respectively cross-connection section 1, cross-connection section 2 and cross-connection section 3. Each complete cable cross-connect section is composed of nine cable sections. Taking the cross-connect segment 1 as an example, the nine cable segments included are A1, A2, A3, B1, B2, B3, C1, C2, and C3. The nine cable sections are divided into three groups, in which the wire cores of A1, A2, and A3 are directly connected in turn to form the A-phase cable line, and the wire cores of B1, B2, and B3 are directly connected in turn to form the B-phase cable line, and C1, C2 The wire cores of C3 and C3 are directly connected in turn to form a C-phase cable line. The metal sheaths of each cable section are cross-connected in the following way: the metal sheaths of A1, B2, and C3 are connected in sequence to form the first section of sheath connection path, and the metal sheaths of B1, C2, and A3 are connected in sequence to form the second section. In the second section of the sheath connection path, the metal sheaths of C1, A2, and B3 are connected in sequence to form the third section of the sheath connection path. The metal sheaths of the two cable sections are cross-connected through the cross-connection boxes J1 and J2. The structures of the cross-interconnection section 2 and the cross-interconnection section 3 are similar to the structure of the cross-interconnection section 1, see FIG. 1 , and will not be repeated here.

Taking each cable cross-connection section as an object, the following method is used to determine which cable cross-connection section the short-circuit fault occurs in the entire high-voltage long cable line: respectively detect the current direction at both ends of the three-section sheath connection path in each cable cross-connection section , if the current direction at both ends of any section of the sheath connection path in a certain cable cross-connection section is opposite, a short-circuit fault occurs in the cable cross-connection section.

For the cross interconnection section 1, the total six current signals at both ends of the three-section sheath connection path are: I _1a and I _2c at both ends of A1-B2-C3; I _1b and I _2a at both ends of B1-C2-A3; C1 —I _1c , I _2b at both ends of A2—B3. For the cross interconnection section 2, the total six current signals at both ends of the three-section sheath connection path are: I _3a and I _4b at both ends of A4—C5—B6; I _3b and I _4c at both ends of B4—A5—C6; C4 —I _3c , I _4a at both ends of B5—A6. For the cross-interconnection section 3, a total of six current signals at both ends of the three-section sheath connection path are: I _5a and I _6c at both ends of A7-B8-C9; I _5b and I _6a at both ends of B7-C8-A9; C7 —I _5c , I _6b at both ends of A8—B9.

In the cable line shown in attached drawing 1, when a breakdown fault occurs in any section of the cable line, the wire core forms a short circuit to the metal sheath, and the wire core current flows directly through the metal sheath from the grounding point at both ends to the ground, causing a faulty cable The metal sheath current of the section and the cable cross-connection section where it is located increases, and the metal sheath current is close to the fault current. At the same time, due to the electromagnetic induction effect, the lines adjacent to the faulty line will also induce a large current. Based on this, the present invention will locate the fault according to the change of the sheath current under the fault.

For the long cable line shown in Figure 1, the metal sheath of the cable is limited by the current amplitude induced by the wire core. The sheath current is very large, and the sensors at both ends detect that the direction of the sheath current is opposite; the non-faulty section has a serious three-phase unbalance due to the large core current of the faulty phase line (close to the power supply direction) or missing (close to the load direction), and it is not a fault The sheath current of the section will also increase, but because of the fault current induction, the sheath current amplitude of the non-fault section is smaller than that of the fault section, and the direction of the sheath current at both ends of the non-fault section is the same. In order to make the criterion of the fault section more significant, the present invention mainly uses the opposite direction of the sheath current at both ends of the fault section (cable cross interconnection section) as the criterion.

Since there is a transient process in the cable metal sheath current during a fault, the fault current is mainly a power frequency current, so it is necessary to extract the power frequency signal of the current through the FFT (Fast Fourier Transformation: Fast Fourier Transformation) method. That is, the current signals at both ends of the three-section sheath connection path in each cable cross-connection section are collected, and the phase angle of the current signal is obtained by performing fast Fourier transformation on the current signal. When a ground fault occurs at any point of the core in a long cable line, the fault current will flow into the ground from the grounding point at both ends along the metal sheath, so the current direction of the sheath at both ends is opposite. The phase difference of the current and power frequency signals at both ends is close to 180°. Since the cable line in a complete cross-connection section generally does not exceed 1500m, the phase difference of the sheath current signals at both ends will not be equal due to the distance between the fault point and the two ends. There is a big difference. Therefore, the phase difference calculation is performed on the phase angle of the current signal at both ends of each sheath connection path, so as to determine whether the current direction at both ends of each sheath connection path is opposite.

In the present invention, use B (I) to represent the power frequency phase (unit is angle) of current signal I, and P (section) represents the sheath current phase difference (section ∈ [" C1 " " C2 " " C3 "], where "C1", "C2", and "C3" respectively represent the complete cross-connection section 1, cross-connection section 2, and cross-connection section 3).

Then the phase differences of the three-section sheath connection paths in the cross-connection section 1 are respectively:

P(C1A)=B(I _2c )-B(I _1a )

P(C1B)=B(I _2a )-B(I _1b )

P(C1C)=B(I _2b )-B(I _1c )

For cross-connection section 2 and cross-connection section 3, there are:

P(C2A)=B(I _4b )-B(I _3a )

P(C2B)=B(I _4c )-B(I _3b )

P(C2C)=B(I _4a )-B(I _3c )

P(C3A)=B(I _6c )-B(I _5a )

P(C3B)=B(I _6a )-B(I _5b )

P(C3C)=B(I _6b )-B(I _5c )

Usually, when the phase angle difference of the current signal at both ends of any section of the sheath connection path is within the allowable phase range centered at ±180°, it is judged that the current direction at both ends of the sheath connection path is opposite. Since the phase difference between the faulty section and the non-faulty section under fault conditions is quite different, a large margin can be left when formulating the faulty section criterion, and the phase allowable range is (120°, 240°)∪( -240°, -120°), that is, when the phase angle difference is within the above range, it is considered that a fault has occurred. Generally, the phase difference of the non-faulty section is very small, within ±30°, so it can be judged by the above method. That is, when the typical long cable line structure shown in accompanying drawing 1 fails, It is considered that the fault occurred in the first cable cross-connect section, Then it is considered that the fault occurred in the second cable cross-connect section, Then it is considered that the fault occurred in the third cable cross-connect section.

The above method for judging a short-circuit fault section is realized by a device for judging a short-circuit fault section. The device for judging the short-circuit fault zone includes a plurality of current transformers and a host computer. Each current transformer is used to respectively detect the current signals at both ends of the sheath connection path of each section in each cable cross-connection section. Usually both ends of each section of sheath connection path are connected to the grounding box (such as G1-G6), and the current transformer is arranged at the grounding box. The host computer is connected to each current transformer, so that the current signal detected by the current transformer is transmitted to the host computer, and the host computer uses the above-mentioned phase method to judge whether a short-circuit fault occurs in each cable cross-connection section. The host also communicates remotely with the monitoring center via the GPRS/3G/4G network through the antenna, thereby remotely uploading the judgment results to the monitoring center.

First, install each current transformer at the position of the above-mentioned grounding box (G1-G6), so as to detect I _1a , I _1b , I _1c , I _2a , I _2b , I _2c , I _3a , I _3b , I _3c , and I _4a , I _4b , I _4c , I _5a , I _5b , I _5c , I _6a , I _6b , I _6c .

The data collected by the current transformer in real time is transmitted to the nearby host, and the host processes the data collected by the current transformer in real time, and performs FFT (Fast Fourier Transformation: Fast Fourier Transformation) on the collected signal to obtain each monitoring point The power frequency amplitude and phase angle of the sheath current, and the phase difference calculation is performed on the monitoring points at both ends of all sections. The processing of data specifically includes:

(1) FFT operation:

in, is the twiddle factor; x(n) is a finite length sequence of length N, that is, the original signal collected by the current transformer; X(k) is a finite length sequence of N points in the frequency domain.

(2) Calculate the phase difference of the monitoring points at both ends of the section:

P(C1A)=B(I _2c )-B(I _1a )

P(C1B)=B(I _2a )-B(I _1b )

P(C1C)=B(I _2b )-B(I _1c )

P(C2A)=B(I _4b )-B(I _3a )

P(C2B)=B(I _4c )-B(I _3b )

P(C2C)=B(I _4a )-B(I _3c )

P(C3A)=B(I _6c )-B(I _5a )

P(C3B)=B(I _6a )-B(I _5b )

P(C3C)=B(I _6b )-B(I _5c )

Among them, B(I) represents the power frequency phase of the current signal I (unit is angle), P(section) represents the phase difference of the sheath current of the corresponding cable section (section ∈ ["C1" "C2" "C3"], Among them, "C1", "C2", and "C3" represent the first, second, and third complete cross-connection sections respectively).

(3) Determination of faulty section

1) Then it is considered that the fault occurred in the first cable cross-connect section.

2) It is assumed that the fault occurred in the second cable cross-connect segment.

3) Then it is considered that the fault occurred in the third cable cross-connect section.

After the above processing, the host communicates via GPRS/3G/4G by setting up an antenna, and finally the judgment result of fault location is uploaded to the terminal monitoring center.

The above method is mainly applied to the judgment of short-circuit fault sections of 110kV and above long cable lines. Once a short-circuit fault occurs in a long high-voltage cable line, the fault section can be quickly judged. Compared with the prior art, the present invention can realize the judgment of the fault section of the high-voltage long cable line, the method can realize on-line monitoring, and the fault section can be found out in time after a fault occurs.

The above-mentioned embodiments are only for illustrating the technical conception and characteristics of the present invention, and its purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly, and not to limit the protection scope of the present invention. All equivalent changes or modifications made according to the spirit of the present invention shall fall within the protection scope of the present invention.

Claims (7)

1. A short-circuit fault section judging method of a high-voltage long cable line, which is used for judging in which of the cable cross-connection sections the short-circuit fault is formed in a high-voltage long cable line composed of a number of cable cross-connection sections, each of the The cable cross-interconnection sections all include several sections of wire cores directly connected to form a three-phase cable line, and the metal sheaths are cross-connected to form a three-section sheath connection path. It is characterized in that: the short-circuit fault section judgment method is: respectively detect The current direction of the two ends of the sheath connection path of the three sections in each of the cable cross-interconnection sections, if the current direction of the two ends of the sheath connection path of any one of the cable cross-interconnection sections is opposite, the A short-circuit fault occurred in the cross-connect section of the cable described above. 2. the short-circuit fault section judging method of high-voltage long cable line according to claim 1, is characterized in that: gather the current signal of three sections described sheath connection path two ends in each described cable cross interconnection section, to Perform fast Fourier transform on the current signal to obtain the phase angle of the current signal; then perform a phase difference calculation on the phase angle of the current signal at both ends of each section of the protective layer connection path, thereby judging the phase angle of each section of the protective layer Whether the direction of current flow at both ends of the connection path is opposite. 3. the short-circuit fault section judging method of high-voltage long cable line according to claim 2, is characterized in that: the difference of the phase angle of the current signal at any one section described sheath connecting path two ends is centered on ± 180 ° When the phase is within the allowable range, it is judged that the current direction at both ends of the sheath connection path in this section is opposite. 4. The method for judging a short-circuit fault section of a long high-voltage cable line according to claim 3, characterized in that: the phase allowable range is (120°, 240°)∪(-240°,-120°). 5. A short-circuit fault section judging device adopting the short-circuit fault section judging method of the high-voltage long cable line described in any one of claims 1-5, characterized in that: the short-circuit fault section judging device includes respectively A plurality of current transformers for detecting the current signals at both ends of the sheath connection path of each section in each section of the cable cross-connection, connected to each of the current transformers, and judging whether a short circuit occurs in each of the cable cross-connection sections A faulty host, said host is remotely connected to the monitoring center. 6 . The device for judging a short-circuit fault section according to claim 5 , wherein both ends of each section of the sheath connection path are connected to a grounding box, and the current transformer is arranged at the grounding box. 7 . 7 . The device for judging a short-circuit fault section according to claim 5 , wherein the host performs remote communication with the monitoring center through an antenna via a GPRS/3G/4G network.