KR20110075763A - Method for detecting fault location on transmission line using second-order differential of travelling waves - Google Patents

Abstract

PURPOSE: A method for detecting a defective point of a transmission line using a second differential is provided to detect rapidly a failure point by measuring an approaching time point of a traveling wave using a second differential of normal current. CONSTITUTION: Current is received through a current transformer at a relay point. A low pass filter is used for removing the noise by filtering the current. The measured current is divided into symmetric components. A current pager is calculated. The second differential of the current pager is calculated. The second differential and time are stored by determining a first traveling wave. The second differential and time are stored by determining a second traveling wave. A distance from a failure point is calculated by comparing two differentials and two time data.

Description

Method for detecting fault location on transmission line using second-order differential of traveling waves}

The present invention relates to a method for detecting a failure point of a transmission line using a secondary difference of a traveling wave signal. More particularly, the present invention relates to a fast wave arrival time by using a secondary difference of a steady-state current phaser of a symmetric component of a traveling wave signal. The present invention relates to a method for detecting a failure point of a transmission line by using a second difference of traveling wave signals applicable to a multi-line transmission line and a non-free transmission line by detecting an accurate failure point.

Accurately identifying the point of failure in the event of a failure of a transmission line is essential for rapid failure recovery to maintain a stable system. In recent decades, the fault-point expression algorithm has been actively studied. The fault expression algorithm can be classified into a method using a traveling wave, a method using a propagation equation, and an impedance method using fundamental wave components of voltage and current.

In general, a method for detecting a failure point of a transmission line is performed by sampling and extracting a voltage and a current at a transmission relay installation point and then filtering using a finite impulse response (FIR) filter. This filtered signal is stored in memory and updated continuously. When a failure occurs, the current filtered signal and the existing stored signal are subtracted to extract the overlapping component, the forward wave signal and the backward wave signal at the relay installation point are extracted from the overlapping component, and the forward wave sample is stored. If the magnitude of the forward wave is larger than the threshold, it is determined as a failure, and the value of the cross-correlation function of the forward and backward wave signals is calculated to determine the distance from the time when the calculated value is maximum to the point of failure.

The prior art described above has the following problems.

First, it is about the application of smoke rail. First, the Yeonga Line is a line made by equilibrating various parameters (R, L, C) of the transmission line, and the unbalanced line has unbalance for each phase. In particular, in Korea, all 765kV transmission lines are being constructed as non-combustion due to practical matters. However, all the prior art ignores the difference in mutual impedance and propagation speed of traveling waves by phase and unbalance in each phase by assuming a soft line. Here, the magnitude of the mutual impedance and unbalance are factors that directly affect the voltage and current signals that appear when a failure occurs, and also affect the voltage and current measured by the relay. That is, in the conventional technique of extracting traveling wave signals from signals of voltage and current, it is assumed that the transmission line is a soft line, which makes it difficult to apply to an ultra-high voltage power line by not considering the influence of mutual impedance in the non-coiled line. .

Second, the application to multi-line tracks. As in the case of smoke / non-flame on three-phase tracks, there is an unbalance between lines in the two-line or more multi-line track, and the degree of inequality becomes greater than that of the love / non-flame problem. In addition, the prior art designed on the basis of the three-phase one-line line does not consider a method for applying to a multi-line line. However, domestic transmission lines are 345kV and 765kV. As the voltage class goes up, there is almost no one-line line, and most of them are constructed as multi-line transmission lines. Therefore, the conventional technology that does not consider a multi-line transmission line has a problem that it is difficult to apply in the real world.

Third, it relates to noise in signal extraction. The fault point detection method in transmission line using traveling wave is used by sampling voltage and current at high frequency. In theoretical calculations and computer simulations, a signal with no measurement noise can be obtained in the extraction of voltage and current signals. However, in real hardware implementation, the measurement noise of various frequencies is mixed to measure voltage and current. Such measurement noise generally has a high frequency signal, which causes a great difficulty in detecting a fault point in a transmission line using traveling waves. Therefore, countermeasures are necessary, but the conventional technology does not consider the countermeasures for such a problem, and therefore, a significant problem arises in actual implementation and application.

The present invention has been made to solve the above problems, by measuring the traveling wave arrival time using the secondary difference of the steady-state current phaser of the traveling wave signal symmetrical component to detect the failure point quickly and accurately multi-line transmission line and It is an object of the present invention to provide a method for detecting a failure point of a transmission line using a second difference of traveling wave signals applicable to a non-combustion transmission line.

The fault point detection method of a transmission line using the secondary difference of the traveling wave signal of the present invention for realizing the object as described above, in the fault point detection method of the transmission line when a fault occurs in the transmission line, the current through the current transformer at the relay point Receiving an input; Filtering using a low pass filter to remove measurement noise of the input current; Decomposing the measured current into symmetrical components and calculating a current phaser of normal delivery among the symmetrical components; Calculating a secondary difference of the current phaser of normal delivery; The second difference value of the current phaser is compared with the reference value tol1, and when the second difference value exceeds the reference value tol1 for the first time, the second difference value peak1 is determined as a first traveling wave signal. Storing time t1; Second, when the second difference value exceeds the reference value tol1 and the second difference value is larger than the reference ratio value tol2, the second difference value peak2 and time t2 are stored. step; And comparing the codes of the two stored second difference values peak1 and peak2 and calculating a distance to the failure point by using the stored two time t1 and t2 information.

에 의하여 계산되는 것을 특징으로 한다. In addition, when the signs of the stored second order difference values (peak1 and peak2) are different,

It is characterized in that calculated by.

에 의하여 계산되는 것을 특징으로 한다. In addition, when the signs of the two stored second difference values (peak1 and peak2) are the same,

It is characterized in that calculated by.

According to the method for detecting a failure point of a transmission line using the secondary difference of the traveling wave signal according to the present invention, it is also applicable to a multi-line transmission line and a non-combustion transmission line, and implemented by using a simple equation to use a traveling wave that requires high-speed processing. It has the advantage of overcoming the difficulties in implementing the method in hardware and more easily in hardware.

Hereinafter, the configuration and operation of the preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. Here, the same reference numerals will be used for the same components as the prior art.

1 is a block diagram of a control unit according to the present invention.

As shown in Figure 1, the control unit 1000 of the present invention is a current input unit 100 receives a current through the current transformer at the relay point, the filter unit 200 for removing the noise of the input current, the measured current A calculation unit 300 for calculating the current phaser of the normal part of the symmetrical component and calculating the second difference of the current phaser of the normal part and the distance to the failure point, and the second difference value of the current phaser; Comparing unit 400 for comparing the reference value and the storage unit 500 for storing the second difference value (peak1, peak2) and the time (t1, t2) according to the result of the comparison unit 400.

Hereinafter, a method for detecting a failure point of a transmission line using the secondary difference of the present invention is disclosed.

2 is a flowchart of a method for detecting a failure point of a transmission line using the second difference of traveling wave signals according to the present invention. In the case where the transmission line is a multi-line line, a failure point detection method of the transmission line using the second difference of the traveling wave signal is applied to each line independently.

The current input unit receives the current through the current transformer at the relay point and measures the current of each phase (S10). The filter unit removes the measured noise of the input current by applying a Butterworth second low pass filter having a cutoff frequency of 20 kHz (S20).

Since problems caused by mutual impedance and non-combustion in the transmission line result in impedance unbalance in each phase, the symmetrical component calculating unit calculates the symmetrical component of the current so that it can be applied even in a multi-line line (S30). The symmetric component is a mathematical technique for solving the unbalance problem of a three-phase power system, and the current measured using the symmetric component is decomposed into an image division current, a normal division current, and a reverse phase current. Here, the steady-state current means that the component having the unbalanced measurement current has the same direction and phase difference as that of the normal phase rotation, and the steady-state current is a physical quantity necessarily generated in any three-phase unbalance circuit. Is defined as

[Equation 1]

, Normal Current:

,

이다. Where a is the pacer operator

to be.

The pager calculating unit calculates a pager using the Discrete Fourier Transform (DFT) with respect to the steady-state current to extract the fundamental wave component (S31), which is defined by Equation 2 below.

[Equation 2]

,Real part:

,

,Imaginary part:

,

Size of Phaser:

Where i _k is the sample value of the input current and N is the number of samples per cycle.

The second difference calculation unit calculates a second difference of the normal current pager to more accurately and clearly detect the traveling wave arrival time from the normal current pager (S32), which is defined in Equation 3 below.

[Equation 3]

,Calculation formula for the second difference of the normal current phaser:

,

Where In is the nth sample of the pager, K is the scale factor, and K = 1 / (sampling time) * 100 with respect to the sampling time.

Next, the first threshold comparison unit compares the secondary difference value of the secondary difference of the normal current pager with the reference value tol1 (S40), and when the secondary difference value exceeds the reference value tol1 for the first time ( S41) It is determined that the first traveling wave signal, the second difference value (peak1) and the time (t1) is stored in the storage unit (S60).

Subsequently, in the second threshold comparison unit, the second difference value of the current phaser of the normal portion exceeds the reference value tol1 (S42) and the second difference value is larger than the reference ratio value tol2 (S43). It is determined that the traveling wave signal, the second difference value (peak2) and the time (t2) is stored in the storage unit (S61).

The failure point calculator compares the signs of the two stored second difference values peak1 and peak2 (S70), and when the signs are different, the first and second traveling waves are determined to be different forward or backward waves, and The distance to the failure point is calculated by 4 (S71).

[Equation 4]

,

,

On the other hand, if the signs are the same, the first traveling wave and the second traveling wave is determined to be the forward wave or the same wave is the same wave and calculate the distance to the failure point by the following equation (5) (S72).

[Equation 5]

,

,

Where d = distance to the failure point, t1 = first traveling wave arrival time, t2 = second traveling wave arrival time, v = propagation propagation velocity on the transmission line (= 3.0x10 ⁵ km / s) and l = length of the entire transmission line. Indicates.

Figure 3 is a systematic model for verifying the present invention, Figures 4, 5, 6 and 7 is a graph showing a failure point estimation error to which the present invention is applied, Figure 8 is a temporary example of the present invention.

In order to verify the performance and accuracy of the present invention, various simulation failures are simulated using EMTP, one of the world's recognized power system transient analysis programs, based on the model system of the 765kV transmission line in Korea. The results of the estimation of the merits were obtained.

As shown in FIG. 3, the control line 1000 measures the current through the current transformer 700 at the relay point using a steel tower configuration, conductor information, etc. of a 765kV transmission line in Korea and has a transmission line length of 137 km. Calculate the distance to the point of failure by applying

As shown in Table 1 below, a simulated failure was applied by combining various conditions such as the type of failure and failure resistance at the failure point.

Table 1

Failure Type Ground fault 1, Ground fault 2, Line short fault, phase 3 fault Fault angle 0˚, 45˚, 90˚ Fault distance 13.74km to 123.66km (simulated by dividing the entire track by 10% units) Fault resistance 0,10,100,200,300,500 [Ω]

4 to 7 are diagrams showing the fault point estimation error of the present invention for each simulated fault of Table 1, and the fault point estimation error was calculated using Equation 6 below.

[Equation 6]

As shown in Figures 4 to 7, it can be seen that the maximum estimation error is very accurate to 0.120%.

It takes 0.1ms to roundtrip the 137.4km transmission line simulated by the traveling wave. Here, the traveling wave generated at the point of failure travels between the relay point and the point of failure and reflects the fault. When the second second wave is measured at the relay point after the first first wave is reached, the fault distance is calculated.

As shown in Fig. 8, even when the fault occurrence point is 137.4km, which is the end of the transmission line, the traveling wave is reflected from the fault point to the relay point (reaching the first traveling wave) and then again at the fault point to move the relay point (reaching to the second traveling wave). The time it takes to follow the path is about 0.15ms, so the fault distance can be calculated accurately in a very short time.

The above-described embodiments of the present invention can be written in a program that can be executed in a computer, and can be implemented in a general-purpose digital computer which operates the program using a computer-readable recording medium.

It is apparent to those skilled in the art that the present invention is not limited to the above embodiments and can be practiced in various ways without departing from the technical spirit of the present invention. will be.

1 is a block diagram of a control unit according to the present invention;

2 is a flowchart of a method for detecting a failure point of a transmission line using a secondary difference of a traveling wave signal according to the present invention;

3 is a system model for verifying the present invention;

4, 5, 6 and 7 are graphs showing a failure point estimation error to which the present invention is applied;

8 is a temporary example of the present invention.

<Explanation of symbols for the main parts of the drawings>

100: current input unit 200: filter unit

300: operation part 400: comparison part

500: storage unit 600: result output unit

700: current transformer 1000: control unit

Claims (6)

In the method of detecting a failure point of a transmission line when a failure of the transmission line occurs, Receiving a current through a current transformer at a relay point; Filtering using a low pass filter to remove measurement noise of the input current; Decomposing the measured current into symmetrical components and calculating a current phaser of normal delivery among the symmetrical components; Calculating a secondary difference of the current phaser of normal delivery; The second difference value of the current phaser is compared with the reference value tol1, and when the second difference value exceeds the reference value tol1 for the first time, the second difference value peak1 is determined as a first traveling wave signal. Storing time t1; Second, when the second difference value exceeds the reference value tol1 and the second difference value is larger than the reference ratio value tol2, the second difference value peak2 and time t2 are stored. step; And Comparing the codes of the two stored second difference values peak1 and peak2 and calculating a distance to the failure point by using the stored two time t1 and t2 information; A method for detecting fault points of transmission lines using the second difference of The method of claim 1, If the sign of the stored two secondary difference value (peak1 and peak2) is different, the fault point detection method of the transmission line using the secondary difference of the traveling wave signal, characterized in that calculated by Equation 4. [Equation 4]

, Where d = distance to the failure point, t1 = first traveling wave arrival time, t2 = second traveling wave arrival time, and v = traveling wave propagation speed (= 3.0x10 ⁵ km / s). The method of claim 1, When the stored two secondary difference value (peak1 and peak2) the same sign, the fault point detection method of the transmission line using the secondary difference of the traveling wave signal, characterized in that calculated by Equation 5. [Equation 5]

, Where d = distance to the point of failure, t1 = first traveling wave arrival time, t2 = second traveling wave arrival time, v = propagation propagation velocity on the transmission line (= 3.0x10 ⁵ km / s) and l = length of the entire transmission line Indicates. 3. The method of claim 2, In the case where the codes of the two stored second difference values peak1 and peak2 are different, the first traveling wave and the second traveling wave are forward or backward waves different from each other. Fault point detection method. 3. The method of claim 2, If the two stored secondary difference values peak1 and peak2 have the same sign, the first traveling wave and the second traveling wave are forward waves that are the same wave or backward waves that are the same wave. How to detect failure points The method of claim 1, wherein the transmission line is a multi-line line.

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