JPS61110066A - Ground fault point location system for parallel multi-circuit - Google Patents

Abstract

PURPOSE:To locate the distance to a fault point at a high accuracy by a specified formula from a zero-phase voltage of its own terminal electric point which will be generated at the ground-fault in one line and zero-phase current flowing through circuits in a system in which a transformer at the end of an opponent bus in a parallel multi-circuit power transmission line having a mid-point impedance. CONSTITUTION:In case a ground-fault occurs, computation is performed about circuit 1, 2, 3... and (n) by the formula [wherein (i) represent 1, 2, 3...(n), but (n) is number of circuit, I01: circuit zero-phase current, V0: own terminal current, Z: mid-point impedance of transformer at opponent bus terminal, l: circuit length] from the zero-phase voltage of its own and the zero-phase current per circuit flowing into an opponent terminal zero-phase impedance. When the computed value Xi reaches the maximum among those X1, C2, X3... and Xn, the (i) circuit is in trouble. The distance to the fault point is located by computed values X1, X2, X3... and Xn of all the circuits but the affected one.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a parallel multi-circuit ground fault fault location method in a high resistance grounding system.

(Prior Art) A fault point location method using a zero-sequence current shunt ratio is generally used to locate a fault point for a ground fault in a parallel two-circuit power transmission line.

The principle of this method based on the zero-sequence current shunt ratio will first be explained with reference to FIGS. 3 and 4.

Figure 6 shows a system diagram (single-phase representation) of two parallel lines.
B is each bus line I on the own end side (location device installation point side) and the other end side
L and 2L are parallel lines provided between the bus line and B. In the figure, it is assumed that a one-wire ground fault has occurred at point F of circuit 111L.

The zero-phase equivalent circuit obtained from the symmetric coordinate method for the above fault is expressed as shown in FIG. Here, X is the distance from the own end to the fault point F when the total length of the line is j, 2
0 is the zero-sequence impedance per unit length of each line, I”0
1. IO2 is the zero-sequence current of each line, and iof is the zero-sequence current at the fault point, and these can be expressed by the following relational expression.

Iof=Io1-4-Ioz
filxZoio1=7ZoI"oz+(z-x)zo
ioz t21ill, +21 equation gives 2<t31. +41 type is each line IL
, Give the distance from the own end of 2L to the failure point.

By the way, in the system shown in Figure 3, the other end (B end)
In some cases, equipment with zero-sequence impedance, such as an arc extinguishing reactor, is installed, but in that case, the influence of zero-sequence impedance will be noticeable, and the above +31. (If formula 41 is used, a positioning error will occur. This will be explained below. In Fig. 5, Re is an arc-extinguishing reactor provided at the other end (end B), and as above, at point F of line 1L. FIG. 6 shows a zero-phase equivalent circuit when a one-wire ground fault occurs.

Here, i0'1: Zero-sequence current from end B to point F? 6:
Zero-sequence voltage λ at B end: Zero-sequence impedance at B end? Of: Zero-sequence voltage at the fault point jof; Assuming zero-sequence current at the fault point, ? of=? o -XZQ iα1f51? or=? o
-JZOI”02-(J-x)ZoLn (61i6
1=1o2−? o/north (7) holds true. (From formula 51, +61, xio1= 1ioz+(t-x) ]”61
f81f71. (8+Equation di01+fO'1=f
If you use 161 = iar - iol, then jol
-ioz ='-5-"1.of (g
l1o1-44oz = l'of +'lG/Z
QQ+91. (From Equation 10, if we apply the principle of the zero-sequence current shunt ratio, we get: The second term on the right side of Equation (2), or the second term on the right side, is the cause of the error. In a high-resistance grounding system, the zero-sequence voltage is generally high (completely When there is a ground fault, the phase voltage is about the same as normal phase voltage), and the magnitude of the voltage drop may be about the same as that of a jof.

Therefore, in a system having a neutral point impedance, that is, a zero-sequence impedance at the opposite end as described above, fault point location using the zero-sequence current shunt ratio cannot be applied.

(Problems to be Solved by the Invention) In the present invention, as described above, in a system having zero-sequence impedance at the other end, the second term on the right side of equation (to) becomes an error factor.

The purpose of the present invention is to locate the distance to the failure point with high precision without being affected by zero-sequence impedance (Means for solving the problem) The principle of the method according to the present invention will first be explained. . 7th
The figure shows a system diagram (single-phase representation) of parallel n lines, where A and B are the self-end side (location device installation point side), each bus line on the other side, and IL-
nL is each parallel line provided between bus lines A and B. Re is an arc extinguishing reactor provided on the other end side (B end) as described above.

Similarly to the above, the zero-phase equivalent circuit when a one-wire ground fault occurs at point F of line 1L is shown in Figure 8. Here, I61
: B end l) What is the zero-sequence current to point F? : Zero-sequence voltage 2 at B end : Zero-sequence impedance at B end? Of: Zero-sequence voltage at the fault point jof: Zero-sequence current at the fault point, then I[;1 = (IO2+IO5+−−・=+l0n
) -V6/beggar aSQ4. From equation (g), xI"o1=, gioz+(z-x)i61 (17) Also, from equation Q6, ""X O2= I 03--------
= I onUsing this in formula 00, I61 = (n-1)IO2-V6/Z
From formula 07969, x(Io1+fa1)=J(I”
oz+161) Using the formula (to) in this formula, we obtain. This α9 formula is an expanded zero-sequence current division ratio I-based location calculation formula, where λ-ce (infinity), n
If = 2, it matches the equation (4) above;
Recognize.

Equation (6) requires zero-sequence current information at the opposite end, that is, the B electric station, in addition to the zero-sequence current information directly obtained at the own end, that is, the electric station B. Ideally, it would be possible to locate using only the current and voltage information of the own end electrician, but in a high-resistance grounding system,
Is the transformer neutral point impedance much larger than the line impedance? 0′=? o −j Zo
What is the voltage drop 7zoioz on the line at ta2?
It can be ignored compared to 0. Therefore, there is no problem in considering it as voyvo.

From the above, we obtain a one-wire ground fault fault location formula for a high-resistance grounded parallel n-line circuit with neutral point impedance at the other end.

Here, Iol: Faulty line zero-sequence current 102: Healthy line zero-sequence current? a: Zero-sequence voltage at own end: When applying the previous formula (2) as the neutral point impedance at the other end, it is necessary to select a faulty line and a healthy line from n lines, but for this reason nIg
The selection of the l line and its orientation to the fault point will be detailed below.

From the previous equation, 1oz=ios=・・・・・・=Ion
Therefore, the denominator of the previous equation (e) becomes.

Here, Xi(
However, "=112131-...+") front (to)
Formula and io1+1o1=iof, ? Using the relationship oαtO, or is obtained, so using equation (2) in equation (2), Xx=
nj-(n-1)x It can be seen that the distance to the failure point is given by the calculated value Xj of lines other than the failure line. Therefore, selection of a faulty line and location of its fault point can be performed in the following manner.

First, the previous c2°C formula, where i=1.2.5.・・・・・・
, n. is calculated according to the above formula. This XI, X2,...
The iL line exhibiting the maximum value from among the Xa O is selected as the faulty line.

Furthermore, Xj other than xi is selected as the orientation value to the failure point.

FIG. 2 is a flowchart illustrating the above procedure in detail, and in step (1) it is determined whether a ground fault has occurred. Step (2) when the zero-phase voltage 9 is greater than or equal to the preset setting level L.
In step (2), the current per line flowing into the zero-sequence impedance of the other end is calculated. In step (3), the current flowing through the zero-sequence impedance is removed. In step (4), the distance is calculated based on the current shunt ratio. In step (5), a faulty line is selected. In step (6), the fault point location values are averaged (arithmetic errors are averaged). In step (7), the above orientation value is output. Finally, in step (8), it is determined whether the ground fault has disappeared, and if YBs, the process ends.

In this way, according to the principle of the present invention method, it can be applied to high resistance grounded parallel multi-circuit transmission lines with neutral point impedance (zero-sequence impedance) at the other end, and in principle, almost no error occurs. It has the feature of being able to perform highly accurate orientation without any problems.

(Example) A specific example using the method of the present invention is shown in FIG. 1 below. Current transformer ICT-n installed on the own end side of times m1L-nL
Zero-sequence currents io1 to Ion for each line are obtained by c'r. IAXCT-nAXCT is the zero-sequence current io1 to Io
An auxiliary current transformer that converts n to an appropriate value of 11 voltage, and FT is an instrument transformer that is the zero-sequence voltage of the system? Get 0.

AXPT is an auxiliary transformer. Is the zero-sequence voltage obtained from each of the above systems for AF? 0. This is an analog filter provided to cut off harmonic components included in the zero-phase current io1 to Ion information and remove aliasing errors. s7H
are sample and hold circuits, which sample the information obtained from the system at the same time, for example, 12 times (6C3 intervals) during one cycle based on a command from the control circuit CON, and hold the sampled values. MPX is a multiplexer that sequentially switches and outputs the sample values, and A/
1) is an AD converter that converts the analog sample value into one digital value. CPU is an arithmetic unit such as a microprocessor that stores the digital information and simultaneously performs predetermined arithmetic operations, and OUT is an output circuit.

Note that the MPX, A/D, and CPU perform predetermined operations based on commands from the control path CON.

Therefore, if a ground fault occurs in any line, a zero-sequence voltage 90 is generated and at the same time zero-sequence currents io1 to Io are generated in each line.
Since n flows, these are CP as sampling data.
Be remembered by U. Then, the fundamental wave component is extracted from the sampling data by the CPU, and the zero-phase voltage? Since the setting level L and line length j for 0 are known, the previous 0
Calculate according to the formula. The output of this calculation is nothing but the distance between the faulty line and its fault point +4x.

(Effects of the Invention) As described in detail, the present invention can be applied to a system having a neutral point impedance at the other end in a high-resistance grounded parallel multi-circuit transmission line, and in principle, there is almost no error. This has the effect of realizing highly accurate failure point location without any problems.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is a flowchart showing the processing procedure according to the invention, Fig. 3 is a single-line system diagram of a parallel two-circuit power transmission line, and Fig. 4 is a diagram showing a failure state. Zero-phase equivalent circuit diagram, Figure 5 is a single-line system diagram with neutral impedance deficiency at the other end, Figure 6 is a zero-phase equivalent circuit diagram at the time of failure, and Figure 7 is a parallel diagram to explain the method of the present invention. n[gli
Figure 8 is a single-line system diagram of the power transmission line, and is a zero-phase equivalent circuit diagram at the time of failure. IL -nL...Line line...Equipment AP with poor neutral point impedance...
Analog filter S/) (...Sample hold circuit MPX...Multiplexer CON...Control circuit A/D...Analog-digital converter CPU...Arithmetic unit

Claims (1)

[Scope of Claims] 1. In a high-resistance grounded parallel multi-circuit transmission line in which the transformer installed at the end of the other bus has neutral point impedance, the power station at the own end that occurs when one wire is grounded is Input the zero-sequence voltage and the zero-sequence current flowing through each line, and define Xi as ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ However, i = 1, 2, 3,...n n: Number of lines■_0_1
:Line zero-sequence current ■_0: Self-end zero-sequence voltage■: Neutral point impedance of transformer at partner bus end l: Calculated based on line length, and the maximum value is obtained from the calculated outputs X1, X2, ..., Xa. A parallel multi-circuit ground fault fault location method in which line i is determined to be a faulty line based on Xi, and calculation outputs Xi other than Xi are located at the distance from the electrical station at its own end to the fault point.