CN110058120A - A kind of extra high voltage direct current transmission line fault recognition method based on voltage transformation trend chi sequence Differential Detection - Google Patents

Abstract

The invention relates to a fault identification method for ultra-high voltage direct current transmission lines based on the cross-order differential detection of voltage transformation trends, and belongs to the technical field of power system relay protection. First, read the fault voltage data obtained by the high-speed acquisition device at the measuring end; secondly, perform cross-sequential differential SOD transformation on the obtained voltage data; when the SOD-transformed fault voltage Su(n) is less than the set value of 100, determine the occurrence area External fault, when Su(n) is greater than the set value of 100, it is judged that the internal fault occurs. In the present invention, the voltage Su(n) after 4th-order cross-order differential transformation theoretically enhances the degree of change, filters out low-frequency signals, is beneficial to eliminating noise, and can better distinguish the fault curves within and outside the area.

Description

A UHVDC Transmission Based on Cross-Sequence Differential Detection of Voltage Transformation Trends Line fault identification method

technical field

The invention relates to a fault identification method for ultra-high voltage direct current transmission lines based on the cross-order differential detection of voltage transformation trends, and belongs to the technical field of power system relay protection.

Background technique

The key to the protection of DC transmission lines lies in the accurate and reliable identification of line faults. The physical entity boundary composed of smoothing reactors and DC filters on both sides of the DC line has a high-frequency blocking effect on the transient electrical quantities caused by faults, so that the high-frequency components of the transient electrical quantities at the line observation terminals are different under internal and external faults. This is the core basis for the setting of DC line protection criteria. Based on this, various line internal fault identification components based on the differential characterization and characterization algorithm of the high-frequency content of the internal and external fault waveforms of the UHVDC transmission line can be constructed.

The current protection scheme of SIEMENS DC line is based on traveling wave protection with voltage and current change rate as the core criterion. In this protection, du/dt is not only used as the starting criterion, but also as the action equation of the internal fault of the line. In this way, if it is necessary to ensure the sensitivity of the line protection action in the case of an internal line fault, and the reliable non-action of the line protection under the line external fault, it is often difficult to balance the two, especially for remote high-resistance faults. Therefore, drawing on the successful experience of AC system protection, this paper separates the fault-starting element, the fault-selecting element and the main protection function, and configures them independently to improve the performance of the SIEMENS traveling wave main protection. When a fault occurs on the transmission line, the fault point will generate a fault traveling wave that propagates along the line to the busbars on both sides. The main protection of du/dt performs a differential operation on the waveform, but when a ground fault occurs at the remote end, the voltage change rate is the same as The voltage change rate is very close when the fault occurs outside the area, and it is difficult to obtain the fault identification criterion. If the fault signature can be amplified and the noise can be eliminated as much as possible, the identification of the remote high impedance fault can be greatly beneficial. Cross-order difference transform, that is, SOD transform, can meet this requirement. The SOD uses the extracted fault initial voltage data to perform cross-sequential differential transformation, so as to quickly detect the fault initial voltage, and the SOD transformation can be performed only by extracting the first few sampling points of the fault voltage signal. Rather than focusing solely on phase characterization, it is an enhancement of the magnitude of the fault feature.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to provide a fault identification method for UHVDC transmission lines based on the cross-order differential detection of the voltage transformation trend, so as to solve the above problems.

The technical scheme of the present invention is as follows: a method for identifying faults in UHVDC transmission lines based on cross-sequential differential detection of voltage transformation trends. Perform cross-order differential SOD transformation; when the SOD-transformed fault voltage Su(n) is less than the set value of 100, it is judged that an out-of-area fault has occurred, and when Su(n) is greater than the set value of 100, it is judged that an internal fault has occurred.

The specific steps are:

The first step, when the power transmission system fails, obtain the initial fault voltage u _M at the measurement point;

The second step is to intercept the fault voltage data in the 2ms time window, and perform 4th-order cross-order differential transformation on the data to obtain Su(n);

Su(n)=u _M (n)-4×u _M (n-1)+6×u _M (n-2)-4×u _M (n-3)+u _M (n-4) (1 )

In the formula, u _M represents the voltage of the measurement terminal, and n represents the number of sampling points;

The third step is to use the SOD transformed value Su(n) to form the fault identification criterion:

When Su(n) is less than the set value of 100, it is judged as an out-of-area fault;

When Su(n) is greater than the set value of 100, it is judged that an internal fault occurs.

The sampling rate in the present invention is 10 kHz.

The principle of the invention is: the fault voltage is acquired by the high-speed acquisition device at the measuring end, and the physical entity boundary formed by the smoothing reactor and the DC filter on both sides of the DC line has a high-frequency blocking effect on the transient electrical quantity caused by the fault, so that the The high-frequency components of the transient electrical quantities of the line observation terminals under the internal and external faults are quite different, which is the core basis for the setting of the DC line protection criteria. The SOD performs cross-sequential differential transformation with the extracted fault initial voltage data, so as to quickly detect the fault initial voltage, and the SOD transformation can be performed only by extracting the first few sampling points of the fault voltage signal. Rather than focusing solely on phase characterization, it is an enhancement of the magnitude of the fault feature. According to the SOD-transformed value of the fault voltage, the internal fault and the external fault are judged.

The beneficial effects of the present invention are:

1. When a ground fault occurs at the remote end, the voltage change rate is very close to the voltage change rate when the fault occurs outside the area, so it is difficult to obtain the fault identification criterion. The SOD transformation can amplify the fault characteristics, which is of great benefit to the identification of remote high-resistance faults. The SOD uses the extracted fault initial voltage data to perform cross-sequential differential transformation, so as to quickly detect the fault initial voltage, and the SOD transformation can be performed only by extracting the first few sampling points of the fault voltage signal. Rather than focusing solely on phase characterization, it is an enhancement of the magnitude of the fault feature.

2. The voltage Su(n) after the 4th-order cross-order differential transformation theoretically strengthens the degree of change, filters out low-frequency signals, which is conducive to eliminating noise, and can better distinguish between the fault curves inside and outside the area.

Description of drawings

Fig. 1 is the structure diagram of the UHV DC power transmission system of the present invention;

Fig. 2 is the original waveform diagram of the fault voltage of the positive line at a distance of 800km from the M terminal in Example 1 of the present invention;

Fig. 3 is the SOD transformation waveform diagram of the fault voltage of the positive line at a distance of 800km from the M terminal in Embodiment 1 of the present invention;

Fig. 4 is the original waveform diagram of the ABC three-phase grounding fault voltage on the rectifier side in Embodiment 1 of the present invention;

Fig. 5 is the SOD transformation waveform diagram of the ABC three-phase ground fault voltage on the rectifier side in Embodiment 1 of the present invention;

6 is an original waveform diagram of the fault voltage of the positive line at a distance of 400km from the M terminal in Embodiment 2 of the present invention;

Fig. 7 is the SOD transformation waveform diagram of the fault voltage of the positive line at a distance of 400km from the M terminal in the second embodiment of the present invention;

Fig. 8 is the original waveform diagram of the two-phase grounding fault voltage of the rectifier side AB in Embodiment 2 of the present invention;

Fig. 9 is the SOD transformation waveform diagram of the AB two-phase grounding fault voltage on the rectifier side in Embodiment 2 of the present invention;

10 is an original waveform diagram of the fault voltage of the positive line at a distance of 200km from the M terminal in Example 3 of the present invention;

Fig. 11 is the SOD transformation waveform diagram of the fault voltage of the positive line at a distance of 200km from the M terminal in Embodiment 3 of the present invention;

12 is an original waveform diagram of a single-phase grounding fault voltage on the rectifier side A in Embodiment 3 of the present invention;

FIG. 13 is a waveform diagram of SOD transformation of the single-phase grounding fault voltage on the rectifier side A in Embodiment 3 of the present invention.

Detailed ways

The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

Example 1: Zhundong-East China ±1100kV UHV DC transmission system structure diagram is shown in Figure 1, and its line parameters are as follows: the total length of the DC transmission line is 3300km.

(1) Acquire fault voltage data at the measurement point according to the first step in the manual.

(2) According to the second step in the specification, take the fault voltage data within the 2ms time window, and perform cross-order differential transformation on the fault voltage data to obtain Su(n).

(3) According to the third step of the specification, the SOD transformed value Su(n) obtained in (2) is used to form a fault identification criterion. It can be seen from Figure 3 that Su(n) is significantly larger than the set value of 100 after the fault occurs, while Su(n) is significantly smaller than the set value of 100 after the fault occurs in Figure 5. Below is an analysis of the two failure scenarios.

(4) Fault location: a fault occurs on the positive line 800km away from the M terminal; the fault start time is 0.7s; the sampling frequency is 10kHz.

(5) Fault location: ABC three-phase grounding fault on the rectifier side; the fault start time is 0.7s; the sampling frequency is 10kHz.

Example 2: The simulation model of Zhundong-East China ±1100kV UHVDC transmission line is shown in Figure 1, and its line parameters are as follows: the full length of the DC transmission line is 3300km.

(1) Acquire fault voltage data at the measurement point according to the first step in the manual.

(2) According to the second step in the specification, take the fault voltage data within the 2ms time window, and perform cross-order differential transformation on the fault voltage data to obtain Su(n).

(3) According to the third step of the specification, the SOD transformed value Su(n) obtained in (2) is used to form a fault identification criterion. It can be seen from Figure 7 that Su(n) is significantly larger than the set value of 100 after the fault occurs, while Su(n) is significantly smaller than the set value of 100 after the fault occurs in Figure 9. Below is an analysis of the two failure scenarios.

(4) Fault location: a fault occurs in the positive line 400km away from the M terminal; the fault start time is 0.7s; the sampling frequency is 10kHz.

(5) Fault location: AB two-phase grounding fault on the rectifier side; the fault start time is 0.7s; the sampling frequency is 10kHz.

Example 3: The simulation model of Zhundong-East China ±1100kV UHVDC transmission line is shown in Figure 1, and its line parameters are as follows: the full length of the DC transmission line is 3300km.

(1) Acquire fault voltage data at the measurement point according to the first step in the manual.

(2) According to the second step in the specification, take the fault voltage data within the 2ms time window, and perform cross-order differential transformation on the fault voltage data to obtain Su(n).

(3) According to the third step of the specification, the SOD transformed value Su(n) obtained in (2) is used to form a fault identification criterion. It can be seen from Figure 11 that Su(n) is significantly larger than the set value of 100 after the fault occurs, while Su(n) is significantly smaller than the set value of 100 after the fault occurs in Figure 13. Below is an analysis of the two failure scenarios.

(4) Fault location: a fault occurs in the positive line 200km away from the M terminal; the fault start time is 0.7s; the sampling frequency is 10kHz.

(5) Fault location: A phase ground fault on the rectifier side; the fault start time is 0.7s; the sampling frequency is 10kHz.

The specific embodiments of the present invention have been described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned embodiments, and can also be made within the scope of knowledge possessed by those of ordinary skill in the art without departing from the spirit of the present invention. Various changes.

Claims (2)

1. a kind of extra high voltage direct current transmission line fault recognition method based on voltage transformation trend chi sequence Differential Detection, It is characterized in that: reading the false voltage data obtained by the high speed acquisition device of measuring end first；Secondly to acquired voltage Data carry out chi sequence difference SOD transformation；When the false voltage Su (n) converted through SOD is less than setting valve 100, judge to send out Raw external area error when Su (n) is greater than setting valve 100 judges that troubles inside the sample space occurs.

2. the extra high voltage direct current transmission line according to claim 1 based on voltage transformation trend chi sequence Differential Detection Fault recognition method, it is characterised in that specific steps are as follows:

The first step, when transmission system breaks down, measurement point obtain primary fault voltage u_M；

The data are carried out 4 rank chi sequence differential transformations, obtain Su by false voltage data when second step, interception 2ms in window (n)；

Su (n)=u_M(n)-4×u_M(n-1)+6×u_M(n-2)-4×u_M(n-3)+u_M(n-4) (1)

In formula, u_MIndicate the voltage of measurement end, what n was indicated is the number of sampled point；

Third step forms fault identification criterion using the transformed value Su (n) of SOD:

When Su (n) is less than setting valve 100, it is judged as external area error；

When Su (n) is greater than setting valve 100, judge that troubles inside the sample space occurs.