JP2863952B2 - Ground fault fault location method and device, ground fault distance relay - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method and an apparatus for locating a fault on a transmission line,
In particular, the present invention relates to a method suitable for improving the positioning accuracy at the time of an imperfect ground fault in a neutral point resistance grounding system.

[Conventional technology]

Conventionally, as a measure to increase the accuracy of fault location,
As disclosed in Japanese Patent No. 39431, a method using a difference signal between current data at the time of an accident and current data before an accident is known.

[Problems to be solved by the invention]

However, according to the method disclosed in the above-mentioned publication, there is a point to be improved in terms of accuracy improvement, because the tidal current changes before and after the accident, and data can be obtained only within the time difference.

In addition, the ground fault distance relay is designed to have a wide operating area in consideration of the influence of the fault point resistance due to an imperfect ground fault, which is incompatible with prevention of unnecessary operation under load. .

An object of the present invention is to solve the above conventional problems,
In other words, it is an object of the present invention to provide a method and an apparatus for locating a fault which can reduce a fault locating error caused by a fault resistance at a ground fault point and improve the locating accuracy.

[Means for solving the problem]

The present invention, in order to achieve the above object, detects a voltage and a current at a reference point of a transmission line determined on a power supply side from a ground fault point and views the reference point based on the detected voltage and the detected current. Calculating the load-side impedance of the transmission line and dividing the obtained load-side impedance by a known line impedance per unit length of the transmission line to obtain a distance from the reference point to a ground fault point. In the method of locating a ground fault fault of a neutral point resistance grounding system, based on at least one of the detection voltage and the detection current and known data related to the power transmission system, a ground fault fault point resistance included in the detection voltage is used. A related error is estimated, and the calculation relating to the load-side impedance is corrected by the estimated error.

[Action]

With this configuration, even if there is a fault point resistance due to an incomplete ground fault or the like, and even if the detected voltage or the like includes a fault point voltage due to the effect, it can be estimated and removed. In addition, it is possible to improve the accuracy of the fault location.

〔Example〕

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

FIG. 1 is an overall configuration diagram of a power transmission system to which a supplement is applied. As shown in the figure, power supplied from a power supply 11 is transformed by a transformer 12 and transmitted to a load 14 via a transmission line 13. Secondary system of the transformer 12 is a neutral point resistor grounding system, the neutral point is grounded via a neutral grounding resistor R _N. The fault point locating device 21 targets the transmission line 13 to be located, and detects each phase detected by the current transformers 22a, b, c and the voltage transformers 23a, b, c provided at the power supply side end of the transmission line 13. The current signal and the phase voltage signal are input.

Now, installation point of fault point locating system 21 (hereinafter, referred to as a reference point) the distance from to the ground fault point F and l (miles), the fault point resistance R _F, a phase of the load impedance was Z _L The following describes an example of the orientation at the time of ground fault. In addition, the following three-phase AC 1
A description will be given using a line model.

In order to measure the distance 1 related to the location of the ground fault point, theoretically, as shown in the following equation (1), the positive-phase impedance Z _1F from the reference point to the fault point F is measured, and this is measured using the transmission line. It can be obtained by dividing by the positive phase impedance Z _1U (Ω / km) per unit length of the 13 lines.

The positive-phase impedance Z _1U is one of the line constants (distribution constants) of the transmission line 13 and can be calculated in advance from the type, arrangement, and dimensions of the line. Note that to obtain l, (1)
Instead of the positive-phase impedances Z _1F and Z _1U in the equation, the negative-phase impedances Z _2F and Z _2U or the zero-phase impedances Z _0F and Z _0U
It is also possible, It is also possible to use the total line impedance Z _F and distribution impedance Z _U made, including those used.

Z _1F and Z _1U are complex numbers each including a resistance component and an inductive reactance component. It is assumed that the capacitance reactance is sufficiently smaller than the inductive reactance, and the description is ignored. Therefore, focusing on the imaginary part of each of the positive-phase impedances Z _1F and Z _1U , the distance 1 in the expression (1) can be obtained also by the following expression (2). However, in equation (2), []
Im means the imaginary part.

The distance measurement by the formula (2) corresponds to the operation of the reactance detecting element of the distance relay in the general protection relay system.

In order to improve the accuracy of the fault location, the fault point F
It is important to accurately measure or obtain the inductive reactance among the positive-phase impedances Z _{1F up} to this point.

Here, for the fault case in FIG. 1, a symmetric equivalent circuit of the three-phase circuit is shown in FIG. 2, and a method for obtaining the positive-phase impedance Z _1F up to the fault point F will be described. In the case of applying the conventional ground fault distance relay method, the following equations (3) to
By the processing shown in (5), the impedance Z _{RY viewed} from the ground fault distance relay is obtained. That is,
The phase voltage Va when the ground fault of a phase go to the reference point expressed by the following equation, I _F R _F is faulty point voltage.

_{Va = I 1 Z 1F + I} 2 Z 2F + I 0 Z 0 F + I F R F ... (3) where Equation (3) gives Va = ３Ia + (K ₀ -1) Io｝ Z _1F + I _F R _F. Becomes

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

V ₁ : Positive phase voltage at reference point V ₂ : 〃 Negative phase voltage V ₀ : 〃 Zero phase voltage I ₁ : 〃 Positive phase current I ₂ : 〃 Negative phase current I ₀ : 〃 Zero phase current Z _1F : Up to fault point positive-phase impedance Z _2F of: inverse sequence impedance Z _0F to failure point: 〃 zero sequence impedance Z _RY: impedance See the ground fault distance relay scheme I _F: fault point current _{= (I 1 + I 2 +} I 0) = 3I 0 va: a detection voltage _{= (V 1 + V 2 +} V 0) equation (5) of the right side impact value according to the second term fault point resistance R _F of the reference point of the fault phase, with respect to the positive-phase impedance Z _1F to be obtained Error. Especially when there is a phase difference between the positive phase and negative sequence current I _1, I ₂ and zero-phase current I _0, there is a problem because fault point resistance R _F is affected as a reactance component. That is, in the equation (2), because attention is paid only to the reactance component, but R _F is not left as a problem if pure resistance, the error factor to act as a reactance.

Next, a fault point locating method of the present invention will be described. The present invention is introduced as shown in (5) the following expression a correction term to clear the error component related to fault point resistance R _F in equation (6). That is, when the line impedance on the load side viewed from the reference point is _ZFL , the following equation is obtained.

Equation (6) is a basic equation of the orientation according to the present invention. The first term is the load-side impedance as viewed from the reference point, and the second term is the correction term. However, I _O of this correction term, Ia, K _O is known by the detection or the like, for fault point resistance R _F is unknown, must be estimated it. Then this R _F
An example of a method for estimating the value will be described.

It can be estimated fault point resistance R _F from the reduction of estimation 1 fault phase voltage.

That is, the simplified equivalent circuit at the time of the a-phase ground fault in FIG.
As shown in the figure. In this figure, Vas is an a-phase power supply voltage, and this voltage can be approximated by an a-phase detection voltage Va at a reference point in a normal state. Here, the line impedance of the transmission line is sufficiently smaller than the neutral point resistor R _N and fault point resistance R _F (usually while the former is 40 [Omega / miles, R _N or R
_{Since F} is 100Ω to several hundred Ω), ignoring them results in the following equations (7) to (9) from FIG.

Vas = 3Io (R _N + R _F ) (7) Va = Vas−3IoR _N (8) Va = 3IoR _F (9) Here, equation (9) is rearranged for 3Io, and this is expressed by equation (8). To remove the Io component and solve for R _F , the following equation (10) is obtained.

Note that the neutral point resistance _RN is known.

Equation (10) is used to calculate the detected phase voltage Va using Va as a reference vector.
Is approximated by the following expression (11).

By the R _F obtained above (6) are substituted into the equation the following equation (12), Z _FL corrected is obtained.

By determining the impedance Z _1F up to the failure point in this way, the orientation distance 1 shown in the equation (2) is determined.

Also, instead of the a-phase voltage Vas at the time of sound, the line voltage of the sound layer such as the b-phase and the c-phase Or a method using a phase voltage immediately before the failure of the a-phase. In this case, the method of using the voltage of the healthy phase or the voltage signal immediately before the failure of the a-phase as Vas is the most desirable because the input signal level corresponds to the fluctuation of the operating voltage of the system.

It is possible to estimate the fault point resistance R _F from the generation amount estimation methods 2 zero-phase voltage Vo. That is, in FIG. 3, complete ground fault (R _F
= 0), Vos = −Vas = 3IosR _N (13) On the other hand, the zero-sequence voltage Vo and the fault current 3Io at the reference point at the time of incomplete ground fault (R _F ≠ 0) are expressed by the following equations (1)
4) and (15).

Solving equations (14) and (15) for R _F yields the following equation (16).

Here, ignoring the phase difference between Vos and Vo, R _F is given by the following equation (1
It can be approximated by 7).

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

Thus the R _F obtained (6) is substituted into equation equation (18)
As shown in the equation, the line impedance Z _IF up to the desired fault point
Can be requested.

It can be determined fault point resistance R _F from the generation amount estimation methods 3 zero-phase current Io.

That is, assuming that the zero-phase current at the time of the complete ground fault is Ios, the following equation (19) is obtained by substituting R _F = 0 into the previous equation (7) and solving for 3Io.

On the other hand, when there is an incomplete ground fault, from equation (7), Therefore, from equations (19) and (20), solving for R _F gives When approximating the absolute value of Io with Ios as a reference, the fault point resistance _RF is obtained by the following equation (22).

From R _F obtained by this, as shown in Figure 2, the fault point voltage V _F is expressed by the following equation (23).

V _F = 3IoR _F (23) The obtained V _F is substituted into the following equation (6), and the line impedance _FL is obtained by the following equation (24).

FIG. 4 is a block diagram of a specific embodiment of the fault point locating device 21 of FIG. In the present embodiment, the above-described orientation processing is performed by digital arithmetic processing, and FIG. 5 shows the processing flow. As shown in FIG. 4, the fault point locating device 21 includes an auxiliary transformer 31, a filter 32, a quantization circuit 33, a signal processing unit 34, and a set value unit 35.

The auxiliary transformer 31 is configured to include a number of auxiliary transformers corresponding to the input signal, and the phase voltage of each phase of the transmission line 13 detected by the current transformer 22 and the transformer 23 provided at the reference point and It has a function of receiving line current, converting those data to a signal of a level suitable for orientation processing, and insulating 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. The quantization circuit 33 has a function of periodically and periodically sampling each of the input signals that have been subjected to the filter processing at the same time, sequentially quantizing them, converting them into digital signals, and outputting the digital signals to the signal processing unit 34. Setting value unit 35 is intended to provide data necessary for fault point locating process in the signal processing unit 34, for example, locating the target come definite by power lines rated voltage Vas, the neutral grounding resistor R _N other setpoint Set in advance.

The signal processing unit 34 performs orientation processing according to the processing flow of FIG. 5 based on the set values and the input data. The fault point locating value including the fault point distance 1 as the processing result is transmitted to a maintenance office via the communication line 36 or the like,
Output to a recording device such as a typewriter.

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

Step 101 is a step of inputting necessary data. As input information, each of three phases a, b, c with complex number information
Phase voltage signals Va, Vb, Vc of each phase, line current signals Ia, Ib, Ic, line constants Z _IU , Z _OU , neutral point ground resistance R _N , and phase voltage rating Vas
And so on.

Step 102 is a step of calculating a compensation term of the zero-phase impedance represented by the following equation (22). Since this operation is a complex number operation, it may be separately obtained for the real part and the imaginary part.

In step 103, the zero-phase current Io is obtained by the following equation (23).

In step 104, the phase voltage absolute value |
Va | Step 105 is a step of calculating an estimated value of the fault point resistance _RF , which is obtained, for example, according to the example shown in the above equation (11).

In step 106, the R _F and the like obtained in step, the (12) performs a calculation shown in the equation determining the line impedance Z _IF to failure point.

Step 107 is a distance conversion unit for calculating the orientation distance l, which is calculated according to the above equation (2). At step 108, the orientation data including the obtained orientation distance 1 is output to the outside.

As described above, according to the present embodiment, the fault point resistance is estimated based on the detected data and the known data at the reference point, thereby correcting the error caused by the fault point resistance. There is an effect that a highly accurate ground fault point locating which is hardly affected by the fault can be performed.

Incidentally, the degree of the effect of the fault point resistance R _F depends on the relationship between the load side impedance Z _L of the target system and the value of the neutral point ground resistance R _N , for example, R _F , R _N , Z _It is assumed that _L is about the same, about 100 to 200Ω, and the transmission line length is assumed to be about 10km. In this case, the positive phase inductive reactance of the line is about 3 to 5Ω over a length of 10 km. Therefore,
In the term relating to the fault point resistance R _F shown in the equation (5), even if several% of R _F acts as an inductive reactance, the orientation distance 1 is erroneously recognized as twice the true value. However, according to the present embodiment, it is possible to reduce the error.

In particular, the effect is great when high-precision orientation is required even for an incomplete ground fault (with a fault point resistance).

Further, according to the correction according to the above-described embodiment, there is an effect that an error due to a shunt effect on a load or a power supply line connected in parallel with the fault point resistance is also corrected.

In the above description, the case of the a-phase ground fault has been described as an example, but the ground faults of the other phases b and c are in the same order of homology and can be similarly located.

Further, in the above embodiment, the method or apparatus for locating the ground fault point has been described. However, if the above embodiment is directly applied to the distance locating unit of the ground fault distance relay, the locating accuracy particularly at the time of an incomplete ground fault is improved. The ground fault distance relay can be realized.

〔The invention's effect〕

As described above, according to the present invention, the error due to the fault point resistance at the fault point is estimated based on the voltage / current data and the known data at the reference point, and the line impedance calculation up to the fault point is calculated based on the estimated value. Since the correction is performed, the fault location error caused by the fault point resistance can be kept small, and the location accuracy can be improved.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of an embodiment including a 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. FIG. 4 is a detailed configuration diagram of the fault locating apparatus of the embodiment shown in FIG. 1, and FIG. 5 is a flowchart showing a processing procedure in the signal processing unit of FIG. 13 ... transmission line, 14 ... load, 21 ... fault locating device, 22
... current transformer, 23 ... voltage transformer, 34 ... signal processing unit, 35 ... setting value unit.

Continued on the front page (72) Inventor Hiroshi Takiguchi 1-1-1, Kokubuncho, Hitachi City, Ibaraki Prefecture Inside the Kokubu Plant of Hitachi, Ltd. (72) Kenji Murata 3-3-22 Nakanoshima, Kita-ku, Osaka-shi, Osaka No. Kansai Electric Power Co., Inc. (72) Koji Ishizu, Inventor 3-3-22 Nakanoshima, Kita-ku, Osaka, Osaka Prefecture Kansai Electric Power Co., Ltd. 22 Kansai Electric Power Co., Inc. (56) References JP-A-59-81568 (JP, A) JP-A-55-66768 (JP, A) JP-A-53-132745 (JP, A) (58) Field (Int.Cl. ⁶ , DB name) H02H 3/40 G01R 31/08

Claims (9)

(57) [Claims] 1. A method for detecting a voltage and a current at a reference point of a transmission line which is set closer to a power source than a ground fault point, and based on the detected voltage and current, the load side impedance of the transmission line as viewed from the reference point. And calculating the distance from the reference point to the ground fault point by dividing the obtained load-side impedance by the known line impedance per unit length of the transmission line. In the method for locating a ground fault in a ground system, an error relating to a ground fault fault resistance included in the detected voltage is estimated and calculated based on at least one of the detected voltage and the detected current and known data on the power transmission system. And correcting the calculation relating to the load-side impedance based on the estimation error. 2. The method according to claim 1, wherein the estimation of the error relating to the ground fault fault point resistance is performed by estimating the fault point resistance based on a voltage drop rate at a reference point of a fault phase. Ground fault fault location method. 3. The method according to claim 1, wherein the estimation of the error relating to the resistance of the ground fault is performed by estimating the resistance of the fault from the amount of generated zero-sequence voltage. . 4. The method according to claim 1, wherein the estimation of the error relating to the resistance of the ground fault is performed by estimating the resistance of the fault from the amount of generated zero-phase current. . 5. A detecting means for detecting a voltage and a current at a reference point of a transmission line defined on a power supply side with respect to a ground fault point;
Load-side impedance calculating means for obtaining the load-side impedance of the transmission line from the reference point based on the detection voltage and the detection current; and dividing the obtained load-side impedance by a known line impedance per unit length of the transmission line. And a distance calculating means for calculating a distance from the reference point to a ground fault point.In a ground fault point locating apparatus of a neutral point resistance grounding system, at least one of the detected voltage and the detected current. An error estimating means for estimating and calculating an error related to a ground fault fault resistance included in the detected voltage based on known data relating to the power transmission system, and the load side impedance is calculated based on the estimated error obtained by the means; A ground fault fault locating device that corrects the calculation according to (1). 6. The error estimating means divides a detected voltage of a failed phase at a reference point by a voltage drop relative to a voltage in a normal state, and a value obtained by multiplying the calculated result by a neutral point resistance is used as a fault point resistance. 6. The ground fault fault locating apparatus according to claim 5, further comprising a configuration for estimating and calculating the error based on the estimated value. 7. The error estimating 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 a fault by the zero-sequence voltage at the time of a fault, and adds a neutral point resistance to the calculation result. 6. The ground fault fault locating apparatus according to claim 5, further comprising a configuration for estimating the multiplied value as a fault point resistance and estimating and calculating the error based on the estimated value. 8. The error estimating means divides the difference between the zero-phase current at the time of a complete ground fault and the zero-phase current at the time of a fault by the zero-phase current at the time of a fault, and adds a neutral point resistance to the calculation result. 6. The ground fault fault locating apparatus according to claim 5, further comprising a configuration for estimating the multiplied value as a fault point resistance and estimating and calculating the error based on the estimated value. 9. A ground fault distance relay comprising the ground fault fault locating device according to any one of claims 5, 6, 7, and 8.