JPS61110067A - Ground-fault location system for parallel two-circuit - Google Patents

Abstract

PURPOSE:To locate the distance to a fault point from a bus terminal of its own at a high accuracy, by performing a computation for the location between the bus terminal of its own and a branch and between the branch and the opponent bus terminal separately by a specified formula from zero-phase currents flowing through circuits in case of a ground-fault of one line in a system having branches from the circuits of a parallel two-circuit power transmission line. CONSTITUTION:The case is divided as follows, where a ground-fault point exists between the bus terminal of its own and the branches and does between the branches and the opponent bus terminal. The distance X (0<=x<=1) to the fault point with each section put at 1, is determined by the formula I (I01 and I02 is zero-phase impedance of each circuit 0<=x<=1 Z0a, Z0b, Z0c: line impedance) for the fault point existing between the bus terminal of its own and the branches or by the formula II for the fault point existing between the branches and the opponent bus terminal to locate the distance to the fault point.

Description

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

(Prior Art) A fault point locating method using a zero-sequence current shunt ratio is generally considered for locating a fault point for a ground fault in a parallel two-circuit power transmission line. About the principle of this failure point locating method $2
First, explanation will be given based on FIGS. 3 to 3.

Figure 2 shows a system diagram (single phase representation) of two parallel lines, A,
B is each bus line on the own end side (location device installation point side) and the other end side,
II, , 2L are parallel lines provided between bus lines B and B. The figure now assumes that a one-wire ground fault has occurred at point F of l1IL.

The zero-phase equivalent circuit obtained from the symmetric coordinate method for the above-mentioned fault is expressed as shown in FIG. Here, when the total length of the line is 1, the distance from the own end to the fault point F is 1.
4K (ratio), io is the zero-sequence impedance of each line, i
ol and La2 are the zero-sequence currents of each line, and fdr is the fault point zero-sequence current, which can be expressed by the following relational expression.

fof==io1+foz fl)x
ZaIo1=(1+1-x)ZoIo2+
21 (11, +21 formula, 1o1=”7'jof, 1az=teIof (31
(Formula 31 is obtained, 6 is, before (41, (Formula 51 is line IL, respectively)
Give the distance from the own end of 2L to the failure point.

By the way, Figure 5 shows the zero-phase equivalent circuit when a one-wire ground fault occurs between DB in a system in which branches lsI L' and 2L' are provided from each line of two parallel lines as shown in Figure 4. .

Here, the distance (ratio) between λF and Dr is X+
, then Vf ==vg -I 02 Zoa (2-xt)
Zob X o3 (sl?f=?o-I'o
, Zoa-xtZob(io1+ioz-1as)
(71?f=?o-1oz Zoa-2(1oz-T
”o3) 2ocHowever, 0≦x1≦1 0≦X!≦1 ?f: Voltage to ground at the end point tO: Self-end zero-sequence voltage Zoa: Line impedance between AD zob: Line impedance between D and B 20c: DC
A line impedance between the two is established. x the previous +61, +71, +81 formulas
Solving for l yields. 1, the relationship between x4 is xt (ZOa-)-ZQb)=ZOa+xr Zo
b, so xl is expressed as. Here, when formula (9) is compared with formula (4), the only common part is t02 I01+IO2, and therefore formula (4) has an error compared to formula (9). This is because in the case of the previous +41.151 formula, the current meridian to the ground fault point F is two routes: person → IL-F and person → 2t-B → 1L → F, whereas in a system with branches, , in addition to these two routes, people → 2L → D
This is because a current path of -+C4D→1L→F is added.

(Problem that @Akira is trying to solve) As mentioned above, in a system where each line of two parallel lines has a branch line, if the conventional method using the zero-sequence current shunt ratio is applied as is, incorrect orientation will occur. Focusing on the fact that
The purpose is to remove this error and locate the distance to the failure point with a high degree of accuracy.

(Means for solving the problem) The method according to the present invention is divided into two cases: a case where the ground fault fault point exists between people and a case where it exists between DBs, and when rJtl of each section is set to 1. The distance to that failure point X (
However, it is characterized in that 0≦work≦1) is determined by the following equation. In other words, (however, if the failure point exists between AD) (however, if the failure point exists between DB), in the previous (1G, (b) equation),
αG is where the failure zone exists, and if the answers found by equation (b) are XAD and XDB, then 0 when between AD.
When ≦XAD≦1, XDB≦0゜DB, 1≦xA
Since D, 0≦xDB≦1, it can be determined by comparing XAD and XDB.

Also, to determine whether the failure point is line 1L or 2L, in the case of 1L, the above applies, and in the case of 2L, 1≦XAD, j≦XDB, so it can be determined that it is not the fault of 1L, and in this case, the equation in the equation This can be determined by replacing 101 and I''02.

(Example) A specific example using the method of the present invention is shown in FIG. 1 below.

IL' and 2L' are branch lines.

Current transformer ICT installed at the own end of lines IL and 2L.

2CT, the zero-sequence current io1. Get the ioz.

IAX and 2AX are auxiliary current transformers that convert the zero-sequence currents fot and foz into appropriate voltage values, and AF cuts harmonic components included in the zero-sequence YIL flow information obtained from the grid and eliminates aliasing errors. This is an analog filter provided for the purpose of VH is a sample hold circuit, which stores the zero-phase current information, for example, by 1 based on a command from the control circuit CON.
Simultaneous sampling is performed 12 times (at 60° intervals) during the cycle and the sampled values are held. MPX is a multiplexer that sequentially switches and outputs the sample values, and ¥D is an AD converter that converts the analog sample values into digital quantities. The CPU is an arithmetic device such as a microprocessor that stores the digital information and simultaneously performs predetermined arithmetic operations, 0UTi! This is an output circuit. In addition, MPX, A/
D.

The CPU performs predetermined operations based on commands from the S/I (similarly, the control circuit CON).

Therefore, if a ground fault occurs in any line, a zero-sequence current io1. ioz will flow, so these should be stored in the CPU as sampling data.

Then, the fundamental wave component is extracted from the sampling data by the CPU. Here, the line length (between λB) and line impedance of each line and branch line are known, so (IG, (
b) Calculate according to the formula. This calculation output is nothing but the distance X to the failure point.

(Effects of the Invention) As described above, the present invention can be applied to a high-resistance grounded parallel two-circuit power transmission line that has a branch line between its own end and the other end, and can also be applied to systems with no errors in principle and high precision. This has the effect of locating the failure point.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is a single line system diagram of parallel two-line AM, Fig. 5 is a zero-phase equivalent circuit diagram at the time of failure, and Fig. 4 is a diagram showing the system of the present invention. A single-line system diagram of two parallel circuits with branch lines for explanation, and FIG. 5 is a zero-phase equivalent circuit diagram at the time of failure. 1L, 2L...Each line IL', 2L'...Each branch line AP...Analog filter S/) (...Sample hold circuit MPX...Multiplexer CON...Control circuit 4/D... ...Analog-to-digital converter cpσ...Arithmetic unit

Claims (1)

[Scope of Claims] 1. In a system that is a high-resistance grounded parallel two-circuit power transmission line and has branch lines branching from each line, the zero-sequence current of each line that flows when one line is grounded is input, and The orientation between the end and the branch line is ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ The orientation between the branch line and the end of the other bus line is ▲ The orientation is ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ However, 0≦X≦1 ■＿0＿a, ■_0_b, ■_0_c: Parallel two-line ground fault fault point locating method that calculates according to the line impedance and locates the calculated output as the distance from the own bus line end to the fault point.