JPH04140016A - Method and device for locating ground fault, and ground fault distance relay - Google Patents

Abstract

PURPOSE:To improve location accuracy by estimating an error relevant to the ground fault point resistance contained in a detected voltage based on at least one of detected voltage or current and known data pertaining to transmission system, correcting the operation of load side impedance based on thus estimated error thereby reducing the fault point location error caused by the fault resistance at the ground fault point. CONSTITUTION:A fault point locator 21 covers a transmission line 13 and provided with phase current signals and phase voltage signals. When a load side impedance is calculated, a correction term for eliminating the error component relevant to a fault point resistance RF is introduced. The fault point resistance RF is an unknown value and estimated based on voltage drop of faulty phase, the amount of zero-phase voltage or the amount of zero-phase current. According to the constitution, fault point location error due to the fault point resistance is suppressed and location accuracy is improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a fault point locating method and device for power transmission lines, and in particular aims to improve the locating accuracy in the event of an incomplete ground fault in a neutral point resistance grounding system. Concerning what is suitable for.

[Conventional technology]

Conventionally, as a measure to improve the accuracy of failure point location,
As shown in Japanese Patent No. 39431, a method is known that uses a difference signal between current data at the time of the accident and current data before the accident.

[Problem to be solved by the invention]

However, according to the method disclosed in the above-mentioned publication, there are some points that need to be improved in terms of accuracy, such as the fact that the current changes before and after the accident, and that data can only be obtained within a time period in which the difference is taken.

In addition, in ground fault distance relays, the operating range is widened in consideration of the influence of fault point resistance due to incomplete ground faults, which contradicts the idea of preventing unnecessary operations under load. .

An object of the present invention is to solve the above-mentioned conventional problems. In other words, it is an object of the present invention to provide a fault point locating method that can suppress the fault point location error caused by the fault resistance of the ground fault fault point to a small value and improve the location accuracy. An object of the present invention is to provide a method and apparatus.

[Means to solve the problem]

In order to achieve the above object, the present invention detects the voltage and current at a reference point of a power transmission line set on the power supply side than the ground fault fault point, and calculates the voltage and current as seen from the reference point based on the detected voltage and current. Determining the distance from the reference point to the ground fault point by determining the load-side impedance of the transmission line and dividing the claimed load-side impedance by the known line impedance per unit length of the transmission line. In the method for locating the ground fault point of a neutral point resistance grounding system,
Based on at least one of the detected voltage and the detected current and known data regarding the power transmission system, an error related to the ground fault point resistance included in the detected voltage is estimated and calculated, and the estimated error causes the load-side impedance to change. It is characterized by correcting such calculations.

[Effect]

With this configuration, even if there is a fault point resistance due to incomplete ground fault, etc., and the fault point voltage due to the effect is included in the detected voltage, etc., this can be estimated and removed. , it becomes possible to improve the accuracy of failure point location.

〔Example〕

Hereinafter, the present invention will be explained based on examples.

FIG. 1 is an overall configuration diagram of a power transmission system to which the present invention is applied. As shown in the figure, power supplied from a power source 11 is transformed by a transformer 12, and is passed through a power transmission line 13 to a load 1.
Power is being transmitted to 4. The secondary system of the transformer 12 is a neutral point resistance grounding system, and the neutral point is grounded via a neutral point grounding resistance RN. Fault point locating device 21 is connected to power transmission line 13
The current transformers 22a, b, c and voltage transformers 23a, b provided at the power supply side end of the power transmission [13] are targeted for orientation.

Current signals and phase voltage signals of each phase detected by C are input.

Now, when the distance from the installation point of the fault point locating device 21 (hereinafter referred to as reference point) to the ground fault fault point F is Q (km), the fault point resistance is RF, and the load impedance is ZL, in the case of an a-phase ground fault. This will be explained using the orientation of . Further, the following explanation will be based on a three-phase AC single line model.

In order to measure the distance wlQ related to the location of the ground fault fault point, theoretically, as shown in the following equation (1), the positive sequence impedance 21F from the reference point to the fault point F is measured, and this is connected to the transmission line 1.
The positive sequence impedance Z, u (
It can be calculated by dividing by Ω/-).

1U Positive sequence impedance Z□U is one of the line constants (distribution constants) of the power transmission line 13, and is 1! It can be calculated in advance from the line type, its arrangement, and dimensions. In addition, to find Ω (
In place of the positive sequence impedance ZIFIZI in equation 1), it is also possible to use the negative sequence impedance Z 2 F tZ2u or the zero sequence impedance 20F, Zou, and the total line impedance ZF including them and the distributed impedance Zu It is also possible to use

21F and Zlu are complex numbers each consisting of a resistance component and an inductive reactance component. Note that the description will be made assuming that the capacitive reactance component is sufficiently smaller than the inductive reactance component, and will ignore it. Therefore, each positive sequence impedance 21
Focusing on the imaginary parts of F and 71U, the distance Q in equation (1) can also be determined by the following equation (2). However, in equation (2), [) Im means the imaginary part.

Distance measurement using equation (2) corresponds to the operation of a distance relay actance detection element in a general protection relay system.

In order to improve the accuracy of failure point location, it is important to accurately measure or obtain the inductive reactance portion of the positive-sequence impedance zlF up to the failure point F.

Here, for the failure case shown in FIG. 1, a symmetrical equivalent circuit of the three-phase circuit is shown in FIG. 2, and a method for determining the positive sequence impedance ZXF up to the failure point F will be described. In the case of applying the conventional one-way ground fault distance relay, the following equation (3) ~
By the process shown in (5), the impedance Z11 seen from the ground fault distance relay is determined. That is, the phase voltage Va at the time of a ground fault of the a phase that can go to the reference point is expressed by the following equation, where IFRF is the fault point voltage.

Va=I, Z, F+l2Z2F+I. Zot-+IFR
FHere, assuming that, Equation (3) becomes: Va= (1a+ (Ko-1) Io) Z, F+ IFRF, and therefore I a + (Ko 1 ) I.

becomes.

here, The meanings of the symbols in the above formula are shown below.

■□ Positive sequence voltage of two reference focal points■2: Negative sequence voltage■. = Zero-sequence voltage■□: Positive-sequence current engineer 2: Negative-sequence current■. = Zero-sequence current Z, F: Positive-sequence impedance up to the fault point 22F: Negative-sequence impedance up to the fault point ZoF: Zero-sequence impedance ZRY: Impedance seen by one type of ground fault distance relay 1F = Fault point current = (■1+■ 2 + 1°) = 3 engineering.

va: Detection voltage at reference point of faulty phase ==(V1+V2+V
. ) The second term on the right side of the above equation (5) is the influence value due to the fault point resistance RF, and becomes an error with respect to the desired positive sequence impedances Z and F. In particular, the positive-sequence and negative-sequence currents I0. I2 and zero-phase current work. If there is a phase difference between the fault point resistance RF
This is a problem because it affects the reactance component. In other words, since equation (2) focuses only on the reactance component, there is no problem if the RF is a pure resistance, but if it acts as a reactance it becomes an error factor.

Next, the fault point locating method of the present invention will be explained. The present invention introduces a correction term as shown in the following equation (6) to eliminate the error related to the fault point resistance RF in equation (5). That is, if the line impedance on the load side viewed from the reference point is ZFL, the following equation is obtained.

Va 3I.

=ZIF... (
6) This equation (6) is the basic equation for orientation according to the present invention, and the first
term is the load-side impedance seen from the reference point, and the second
term is a correction term. However, out of this correction term, Io, I
a, Ko are known through detection etc., but the fault point resistance RF
Since is an unknown quantity, it must be estimated.

Next, an example of a method for estimating this RF will be described.

Reiji 1jffi top The fault point resistance RF can be estimated from the drop in fault phase voltage.

That is, the simple equivalent circuit at the time of the a-phase ground fault in FIG. 1 is as shown in FIG. 3. In the figure, Vas is the a-phase power supply voltage, and this voltage can be approximated by the a-phase detection voltage Va at the reference point in a healthy state.

Here, the line impedance of the transmission line is the neutral point resistance RN
and fault point resistance RF (normally, the former is 40 Ω/b, whereas RN or RF is 100 Ω/b
(several hundred Ω), so if ignored, the following equation (7) can be obtained from Figure 3.
~(9) holds true.

Va s=3 I o (RN+RF) −(7)
Va = Vas-3IORN-(8) Va
=3 I ORF − (9) where (9
) is rearranged for 3Io, substituted into equation (8) to remove the Io acid component, and further solved for RF to obtain the following equation (10).

Vas-Va Note that the neutral point resistance RN is known.

When formula (10) is approximated for the absolute value IVa1 of the detected phase voltage Va using Vas as a reference vector, the following formula (11) is obtained.
becomes.

By substituting the RF obtained above into the equation (6), the corrected ZFL is obtained by the following equation (12).

Ia ten (Ko-1) I.

I a+ (Ko-1) I.

Vas-Va #Z Engineering F...(
12) In this way, the impedance 2 up to the failure point
By determining 1F, the target road 1 shown in equation (2) is
Find ρ.

Furthermore, instead of the a-phase voltage Vas when it is healthy, the phase voltage of the b-phase which is very good and immediately before the failure of the a-phase may be used. In this case, the most desirable method is to use the voltage of the healthy phase or the voltage signal immediately before the failure of the a phase as Vas, since the input signal level corresponds to the operating voltage fluctuations of the system.

1 L] LI The fault point resistance RF can be estimated from the amount of zero-sequence voltage Vo generated. In other words, in Fig. 3, when there is a complete ground fault (
If the zero-sequence voltage at RF=○) is Vos, then there is a relationship as follows: Vos=-Vas=3IosRN.-(13). On the other hand, zero-sequence voltage Vo and fault current 3I at the reference point during incomplete ground fault (RF≠O).

are expressed by equations (14) and (15), respectively.

Vo=-Vas-3l 0RF = Vos-3IORF (14) When equations (14) and (15) are solved for RF, the following equation (1
6) is obtained.

Here, if the phase difference between Vos and Vo is ignored, RF can be approximated by the following equation (17).

However, Vos is a zero-sequence voltage level that occurs at the time of a complete ground fault, and can also be determined from the line voltage of a healthy phase or the phase voltage immediately before a failure.

Substituting the RF obtained from this into equation (6), the following equation (18
) Line impedance Z up to the desired failure point as shown in the equation
You can find the IF.

Va Ia+(Ko-1)I.

Ia + (Ko-1) Io l V.

Cape ZIF...
- (18) Fault point resistance RF can be determined from the amount of generated zero-sequence current Io.

That is, if the zero-sequence current at the time of a complete ground fault is Ios, then by substituting RF=O into both equations (7) and solving for 3Io, we get
The following equation (19) is obtained.

N On the other hand, in the case of incomplete ground fault, from Equation 1 (7), RN + R
F. Therefore, from equations (19) and (20), solving for RF gives the following equation, and by approximating by the absolute value of ■0 with Ios as the reference, the fault point resistance RF can be found by the following equation (22).

From the RF thus obtained, the fault point voltage VF can be expressed by the following equation (23), as shown in FIG.

VF=3IORF...-(2
3) By substituting the VF thus obtained into both equations (6), the line impedance ZFL is found using the following equation (24).

Va 3I.

Ia+(Ko-1)I.

Ia+(Ko-1)I.

FIG. 4 is a block diagram of a specific embodiment of the failure point locating device W21 shown in FIG. This example uses digital calculation processing to
The above-mentioned orientation processing is carried out, and the processing flow is shown in FIG. As shown in Fig. 4, the failure point locating device 2
1 is an auxiliary transformer 31, a filter 32, a quantization circuit 33,
It is configured to include a signal processing unit 34 and a setting value unit 35.

The auxiliary transformer 31 includes a number of auxiliary transformers corresponding to the input signal, and converts the phase voltage of each phase of the power transmission line 13 tested by the current transformer 22 and transformer 23 provided at the reference point. It has the function of inputting line current and converting the data into signals at a level suitable for location processing, as well as communicating within 1 m from the outside. The filter 32 includes a number of filters corresponding to the number of input signals, and has a function of removing unnecessary harmonic components for each input signal. Quantization circuit 3
3 has a function of periodically sampling and bolding each filtered input signal at the same time, sequentially quantizing this, converting it into a digital signal, and outputting it to the signal processing unit 34. The setting value unit 35 provides the signal processing unit 34 with data necessary for failure point locating processing. For example, the rated voltage Vas, neutral point grounding resistance RN, and other setting values determined by the power transmission line to be located are set in advance. It is settled.

The signal processing unit 34 performs orientation processing according to the processing flow shown in FIG. 5 based on the given setting values and input data. The processing result, the fault point location value including the fault point distance Q, is transmitted to a maintenance center or the like via the communication line 36 or the like, or output to a recording device such as a typewriter.

Here, the processing in the signal processing unit 34 will be explained with reference to FIG.

Step 101 is a step for inputting necessary data. The input information is three phases a and b each having complex number information.
, C phase voltage signals Va, Vb.

Vc line current signal of each phase Ia + Ib + Ic, line constant zI
υTZOu, neutral point grounding resistance value RN, phase voltage rated value V
This includes as, etc.

Step 102 is a step of calculating a zero-sequence impedance compensation term shown in the following equation (22). Since this operation is a complex number operation, the real part and the imaginary part may be calculated separately.

Z) IJ In step 103, the zero-sequence current Io is determined by the following equation (23).
seek.

1 o =-(I a + I b + I c) ”-・
(23) In step 104, the phase voltage absolute value 1Val of the a phase, which is the failed phase, is determined. Step 105 is a step of calculating the estimated value of the fault point resistance RF, for example, according to the example shown in equation (11) above.

In step 106, the calculation shown in equation (12) above is performed using the RF etc. obtained in the above step, and the line impedance ZIF up to the failure point is obtained.

Step 107 is a distance conversion unit that calculates the orientation hole 11N, and calculates it according to the above equation (2). In step 108, the orientation data including the determined orientation hole lliρ is output to the outside.

As described above, according to this embodiment, the fault point resistance is estimated based on the detected data and known data at the reference point,
This corrects the error caused by the fault point resistance, so it is possible to locate the ground fault point with high precision, which is less susceptible to the influence of the fault point resistance.

Incidentally, the degree of influence of the fault point resistance RF varies depending on the relationship with the load impedance zL of the system to be located and the neutral point grounding resistance value RN.
It is assumed that IZL is approximately the same, about 100 to 200Ω, and that the transmission line length is about 10 km. In this case, the positive phase inductive reactance of the line is approximately 3 to 5 for a length of 10 km.
It is about Ω.

Therefore, in the term related to the fault point resistance RF shown in equation (5), even if a few percent of RF acts as an inductive reactance, the orientation hole @Q will be incorrectly recognized as twice its true value. However, according to this embodiment, it is possible to suppress the error to a small value.

This is particularly effective when highly accurate orientation is required even in the case of an incomplete ground fault (with resistance at the fault point).

Further, the correction according to the above embodiment has the effect that errors due to the influence of shunting on the load or power supply line connected in parallel with the fault point resistor are also corrected.

In addition, although the above explanation took the case of an a-phase ground fault as an example, ground faults of other phases and c can also be located in the same order and can be located in the same manner.

Furthermore, in the above embodiment, a method or device for locating a ground fault fault point has been shown, but if the above embodiment is applied as is to the distance locating part of a ground fault distance relay, the locating accuracy will be improved especially in the case of an incomplete ground fault. A ground fault distance relay can be realized.

〔Effect of the invention〕

As explained above, according to the present invention, the error caused by the fault point resistance at the fault point is estimated based on the voltage/current data and known data at the reference point, and the line impedance calculation up to the fault point is performed using this estimated value. Since the correction is performed, it is possible to suppress the failure point location error caused by the failure point resistance to a small value and improve the location accuracy.

[Brief explanation of drawings]

Fig. 1 is an overall configuration diagram of an embodiment including the transmission line system to which the present invention is applied, Fig. 2 is a symmetrical equivalent circuit diagram at the time of a-phase ground fault, and Fig. 3 shows the estimation method. 4 is a detailed configuration diagram of the failure point locating device of the embodiment shown in FIG. 1, and FIG. 5 is a flowchart showing the processing procedure in the signal processing unit of FIG. 4. 13...Power transmission line, 14...Load, 21...Fault point locating device, 22...Current transformer, 23...Voltage transformer, 3
4. Signal processing unit, 35... Setting value unit.

Claims (1)

[Claims] 1. Detect the voltage and current at a reference point of the power transmission line that is set on the power source side than the ground fault fault point, and calculate the voltage and current of the power transmission line as seen from the reference point based on the detected voltage and current. The load-side impedance is determined, and the distance from the reference point to the ground fault point is determined by dividing the determined load-side impedance by the known line impedance per unit length of the transmission line. In the method for locating a ground fault fault point in a resistive point resistance grounding system, based on at least one of the detected voltage and the detected current and known data regarding the power transmission system,
A method for locating a ground fault fault point, characterized in that an error related to the ground fault fault point resistance included in the detected voltage is estimated and calculated, and the calculation related to the load-side impedance is corrected using the estimated error. 2. The ground fault fault according to claim 1, wherein the error related to the ground fault fault point resistance is estimated by estimating the fault point resistance based on a voltage drop rate at a reference point of the fault phase. Point orientation method. 3. The ground fault fault point locating method according to claim 1, wherein the error related to the ground fault fault point resistance is estimated by estimating the fault point resistance from the amount of generated zero-sequence voltage. 4. The ground fault fault point locating method according to claim 1, wherein the error related to the ground fault fault point resistance is estimated by estimating the fault point resistance from the amount of generated zero-sequence current. 5. Detection means for detecting the voltage and current at a reference point of the power transmission line set on the power supply side than the ground fault fault point, and the load-side impedance of the power transmission line as seen from the reference point based on the detected voltage and current. load-side impedance calculation means for calculating the load-side impedance, and dividing the calculated load-side impedance by the known line impedance per unit length of the transmission line,
Distance calculation means for calculating the distance from the reference point to the ground fault fault point, in a ground fault fault locating device for a neutral point resistance grounding system, comprising at least one of the detected voltage and the detected current and the power transmission system An error estimation calculation means is provided for estimating and calculating an error related to the ground fault point resistance included in the detected voltage based on known data regarding the load side impedance. A ground fault fault point locating device characterized by correcting. 6. The error estimation calculation means divides the detected voltage of the faulty phase at the reference point by the voltage drop with respect to the normal voltage;
6. The ground fault fault according to claim 5, further comprising a configuration in which a value obtained by multiplying the calculation result by a neutral point resistance is estimated as the fault point resistance, and the error is estimated and calculated based on the estimated value. Point locating device. 7. The error estimation calculation means divides the difference between the zero-sequence voltage at the time of a complete ground fault and the zero-sequence voltage at the time of the failure by the zero-sequence voltage at the time of the failure,
6. The ground fault fault according to claim 5, further comprising a configuration in which a value obtained by multiplying the calculation result by a neutral point resistance is estimated as the fault point resistance, and the error is estimated and calculated based on the estimated value. Point locating device. 8. The error estimation calculation means divides the difference between the zero-sequence current at the time of a complete ground fault and the zero-sequence current at the time of the failure by the zero-sequence current at the time of the failure,
6. The ground fault fault according to claim 5, further comprising a configuration in which a value obtained by multiplying the calculation result by a neutral point resistance is estimated as the fault point resistance, and the error is estimated and calculated based on the estimated value. Point locating device. 9. A ground fault distance relay comprising the ground fault point locating device according to any one of claims 5, 6, 7, and 8.