JPH06347505A - Ground fault position locating apparatus - Google Patents

Abstract

PURPOSE:To locate a ground fault position by detecting a current only at a receiving terminal by a method wherein a zero phase current value at a complete grounding is settled and a ground rate is calculated from a measured zero phase voltage at the occurrence of a fault so that a fault current is estimated based on a measured zero phase current and the ground rate and an operation of zero phase current divisional rate is subjected thereto. CONSTITUTION:A zero phase voltage V0 from a zero phase voltage transformer GPT and zero phase currents IO1', IO2' from a zero phase current transformer ZCT are inputted to a fault position locating section 1 and stored in a memory 16 via an auxiliary voltage transformer 12, an S/H 13 and an A/D convertor 14. On the other hand, a distance d from a sending terminal A to a receiving terminal B, a zero phase current NGRI on the complete grounding and a system voltage official value E are stored in a memory 17 as settlement values. A CPU 18 fetches data immediately after a fault from the memory 16 to calculate a ground rate rho=¦V0¦/E by using the zero phase voltage V0 and the system voltage official value E so that a fault current I0f is estimated in accordance with an equation of I0f=NGRIXrho. A distance X from a sending terminal A to a fault position is calculated by using an equation of X=(-IO2'$+IO1')d/ I0f for a one L line fault or an equation of X=(IO2'-IO1')d/I0f for a two L line fault.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fault point locating method for a high resistance grounding type two-terminal parallel two-line power transmission line, and more specifically, a fault point locating method when a current detecting section is provided only at a load end. It is about.

[0002]

2. Description of the Related Art As a conventional ground fault fault locating method in a high resistance grounding system 2-terminal parallel 2-line transmission line, zero-phase currents I ₀₁ and I ₀₂ of each line of parallel 2 lines are detected.
The zero-phase current diversion ratio I _0i / (I ₀₁ + I ₀₂ ) (i takes 1 or 2) is calculated, and the distance from the power transmission end to the ground fault point is calculated based on the zero-phase current diversion ratio. There is a way.

FIG. 3 is a zero-phase equivalent circuit diagram for explaining the zero-phase current shunt ratio calculation method. The lengths of the power transmission end A and the power reception end B of the two-terminal parallel two-line power transmission lines 1L, 2L are d. It is assumed that the zero-phase current I ₀₁ flows through the 1L line at the power transmission end A and the zero-phase current I ₀₂ flows through the 2L line. A ground fault occurs in the 1L line at a distance x from the power transmission end A, and the zero-phase current I _0f starts flowing from the fault point.

The distance x from the power transmitting end A to the failure point can be calculated by the following equation based on only the current information of the power transmitting end A. x = 2dI ₀₂ / (I ₀₁ + I ₀₂ ) (1) The basis for deriving the above formula is, for example, Japanese Patent Laid-Open No. 2-1977.
This is described in Japanese Patent No. 9 as prior art.

[0005]

However, if the current detecting section is installed only at the power receiving end B, the above-mentioned zero-phase current shunting ratio calculation method cannot be applied. This will be described in detail. FIG. 1 is a zero-phase equivalent circuit diagram for explaining a zero-phase current shunt ratio calculation method having a measuring unit at the power receiving end. V ₀ , V ₀ ′ and V _of represent the zero phase voltage at the power transmitting end A, the power receiving end B and the fault point, respectively. 1L of this circuit
In _{line, V of = V 0 -x (} Z 0 I 01 + Z 0m I 02) V of = V 0 '- (d-x) (Z 0 I 01' + Z 0m I 02 ') holds. However, Z ₀ is a zero-phase impedance per unit distance, and Z _0m is a zero-phase mutual impedance per unit distance. Subtracting both equations, V ₀ −V ₀ ′ = x (Z ₀ I ₀₁ + Z _0m I ₀₂ ) − (d−x)
(Z ₀ I ₀₁ ′ + Z _0m I ₀₂ ′) Similarly for the 2L line, V ₀ −V ₀ ′ = x (Z ₀ I ₀₂ + Z _0m I ₀₁ ) − (d−x)
(Z ₀ I ₀₂ ′ + Z _0m I ₀₁ ′) If V ₀ and V ₀ ′ are eliminated from the above equations, x (Z ₀ −Z _0m ) (I ₀₁ −I ₀₂ ) = (d−x) (Z ₀ −
Z _0m ) (I ₀₁ ′ −I ₀₂ ′), and (Z ₀ −Z _0m ) can be erased, and x (I ₀₁ −I ₀₂ ) = (d−x) (I ₀₁ ′ −I ₀₂ ′) Become. Solving for x gives x = (I ₀₂ + I ₀₁ ′) d / (I ₀₁ + I ₀₁ ′) (2). However, I ₀₂ + I ₀₂ ′ = 0 was used.

Since I ₀₁ + I ₀₁ ′ is equal to the fault current I _0f , equation (2) can also be written as follows. x = (I ₀₂ + I ₀₁ ′) d / I _0f (3) The equation (2) above contains the current I ₀₁ at the power transmission end A, and the equation (3) contains the fault current I _0f. Therefore, the distance x from the power transmission end A to the failure point cannot be obtained based on only the current information of the power reception end B.

Therefore, an object of the present invention is to solve the above technical problems and provide a ground fault fault point locating method capable of finding a ground fault fault point even when current detection is performed only at the power receiving end B. Is.

[0008]

A ground fault fault location method according to claim 1 for achieving the above object is a line length d from a transmitting end to a receiving end and a zero-phase current at a complete ground fault. Value NG
The RI is settled, the zero-phase voltage at the receiving end, the 1L line zero-phase current and the 2L line zero-phase current are measured, the ground fault ρ is calculated based on the measured zero-phase voltage at the time of failure, and the zero-phase current is calculated. Value NGRI
This is a method of locating a ground fault point by estimating a fault current value based on the ground fault degree ρ and performing a zero-phase current shunt ratio calculation based on the estimated fault current value.

[0009]

When the zero-phase current NGRI at the time of a complete ground fault is settled, the zero-phase current (fault current) I when there is an actual ground fault
_0f is expressed as I _0f = NGRI × ρ. Here, ρ is the ground fault degree, and is expressed as ρ = | V ₀ | / E by using the zero-phase voltage V ₀ at the time of failure and the system voltage nominal value E.

When the voltage drop of the transmission line due to the ground fault current is ignored (the absolute value of the ground fault current is small, this approximation does not hold true), the zero-phase voltage V ₀ is the same as that measured at the power receiving end B. What is measured in A can be regarded as the same. Therefore, the ground fault degree ρ is calculated based on the zero phase voltage V ₀ at the power receiving end, and the fault current value I _0f is estimated based on the zero phase current value NGRI and the ground fault degree ρ, and this is estimated. Based on the fault current value I _0f , the zero-phase current diversion ratio calculation x = (I ₀₂ + I ₀₁ ′) d / I _0f = (− I ₀₂ ′ + I ₀₁ ′) d / I _0f shown in equation (3) is performed. Thus, the ground fault point can be located.

[0011]

Embodiments will be described in detail below with reference to the accompanying drawings showing embodiments. FIG. 2 is a block diagram showing a zero-phase current transformer ZCT provided at a power receiving end B of each of the power transmission lines 1L and 2L, a zero-phase transformer GPT provided at a bus of the power receiving end B, a fault locator 1 and the like. It is a figure.

The fault location device 1 includes a zero-phase transformer GPT.
The zero-phase voltage V ₀ , which is the detection voltage of _0, and the zero-phase currents I ₀₁ ′ and I ₀₂ ′, which are the detection currents of the zero-phase current transformer ZCT, are input. The zero-phase voltage V ₀ and the zero-phase currents I ₀₁ ′ and I ₀₂ ′ are digitized through the auxiliary transformer 12, the sample hold circuit 13, and the A / D conversion circuit 14 and supplied to the bus line 15, and the data memory 16 is provided. Stored in.

On the other hand, the line length d from the power transmitting end A to the power receiving end B, the zero-phase current NGRI at the time of a complete ground fault, and the system voltage nominal value E
(For example, if the system is 6.6 kV, E = 6.6 kV /
√3) is stored in the settling value memory 17 as a settling value. This storage can be done by a keyboard through the I / O device 20, for example. CPU1
Reference numeral 8 denotes the memory 1 when a failure detection circuit (not shown) provided separately from the failure point locating device 1 detects a ground fault.
The data immediately after the failure is taken out from 6, and the ground fault degree ρ is calculated based on the equation, ρ = | V ₀ | / E, using the zero-phase voltage V ₀ at the time of the failure and the system voltage nominal value E The current I _0f is estimated by the formula I _0f = NGRI × ρ.

Then, using the zero-phase current values I ₀₁ ′ and I ₀₂ ′ stored in the data memory 16, the calculation of the equation x = (− I ₀₂ ′ + I ₀₁ ′) d / I _0f is performed and 1 L When the line breaks down, the distance from the power transmission end A to the failure point is calculated. Similarly, x = (I ₀₂ ′ −I ₀₁ ′) d / I _0f is calculated to find the distance from the power transmission end A to the failure point when the 2L line fails.

The orientation output of the CPU 18 is the I / O device 19
Is output to the display device through the display device, and the failure line and the distance to the failure point are displayed on the display device.

[0016]

As described above, according to the ground fault fault location method of the present invention, the ground fault degree ρ is calculated based on the zero phase voltage at the power receiving end, and the zero phase current value NGRI and this ground fault are calculated. The fault current value I _0f can be estimated based on the degree ρ. Therefore, even in the case where the current is detected only at the power receiving end, which was conventionally considered to be inapplicable to the zero-phase current shunt ratio calculation method, the zero-phase current shunt ratio calculation is performed based on the estimated fault current value I _0f. It is possible to locate the ground fault point.

[Brief description of drawings]

FIG. 1 is a zero-phase equivalent circuit diagram for explaining a zero-phase current shunt ratio calculation method of the present invention.

FIG. 2 is a block diagram showing a zero-phase current transformer ZCT provided at a power receiving end B of each of the power transmission lines 1L and 2L, a zero-phase transformer GPT provided at a bus of the power receiving end B, a fault locator 1 and the like. It is a figure.

FIG. 3 is a zero-phase equivalent circuit diagram for explaining a zero-phase current diversion ratio calculation method.

[Explanation of symbols]

 1L, 2L High resistance grounding system 2 terminals Parallel 2 lines Transmission line A Transmission end B Receiving end

Claims (1)

[Claims] Claim: What is claimed is: 1. A method of locating a distance x from a power transmission end to a ground fault point of a high resistance grounding two-terminal parallel two-circuit power transmission line, wherein a line length d from the power transmission end to the power reception end is set to complete earth ground. Set the zero-phase current value NGRI at the time of the fault, measure the zero-phase voltage at the receiving end, the 1L line zero-phase current and the 2L line zero-phase current, and ground fault based on the zero-phase voltage at the receiving end at the time of failure. Degree ρ is calculated, the fault current value is estimated based on the zero-phase current value NGRI and the ground fault degree ρ, and the zero-phase current shunt ratio calculation is performed based on the estimated fault current value. A ground fault fault point locating method characterized by locating fault points.