JPS63217917A - Failed phase selector - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION OBJECTS OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for fault phase selection in direct earthing systems.

(Prior Art) A fault point locating device is used to determine the distance to a fault point on a power transmission line. In this case, it is necessary to use the voltage and current in the fault phase for distance calculation. Fault point location is then performed using a digital arithmetic processing device as shown in FIG. That is, the voltage and current of the power system are taken in through the input converter 51 that centralizes and houses the auxiliary PCT,
Filtering is performed by a filter (FL) 52 that extracts only the commercial frequency component of the voltage. Since each filter output is an analog signal, it is sent to a sample hold circuit (S/I() 53 and a multiplex f(
MPX) 54 via analog/digital converter (
A/D) 5s and converts it into a digital signal. The converted voltage and current digital signals are
Data memo via Direct Memory Access (DMA) 56! J (RAM) 57 temporarily. CPU 58 is the current stored in RAM 57.

Digital calculation processing is performed on the voltage data according to the processing procedure stored in the read-only memory (ROM) 59, and orientation activation and orientation calculation are performed.

The orientation methods can be broadly classified into the following two methods.

The first method does not select the fault phase, but uses voltage and current to calculate the distance in the case of a ground fault and the distance to calculate the distance in the case of a short circuit, respectively, to find the distance to the fault point. It's a method.

The second method is to perform fault phase selection using an undervoltage relay with current compensation (a type of distance relay), and then find the distance to the fault point.

(Problems to be Solved by the Invention) In the conventional methods described above, since both methods use voltage and current, the processing becomes extremely complicated.

Particularly in the case of devices that perform digital processing, there is a drawback that the program becomes larger and the operating time becomes slower. The problem with the program can be solved by adding more memory, but this will not solve the problem of operating time.

The present invention has been made in order to solve the above-mentioned problems, and it is an object of the present invention to provide a fault phase selection method that can quickly and reliably perform fault phase selection using only current in a directly grounded system. .

[Structure of the invention]

(Means for solving the problems) The present invention will be explained using FIG. 1 corresponding to an embodiment.
The calculation unit 11 calculates the ratio between the line-to-line fault current of the power transmission line and the maximum value of this fault current, and if this ratio is smaller than a certain constant value, the 1-phase failure detection unit 121 determines whether the 1-line It is configured such that when a ground fault occurs and all three line-to-line phases are larger than a certain fixed value, the two-phase or more fault detection unit 122 determines that two or more wires are faulty.

(Operation) Therefore, the fault phase can be detected by the outputs from the l-phase failure detection section 121' and the two-phase failure detection section 122.

(Example) First, when focusing on the current at the time of a system fault in a directly grounded system, the following phenomenon occurs.

At the time of a one-line ground fault, the fault current concentrates on the faulty phase and does not flow to the healthy phases, so the phase change current between the healthy lines becomes zero. For example, if we take an a-phase one-wire ground fault as an example, the current changes in each phase are as follows: I, = I, Ib = Ic = 0. Therefore, the change in each line current is 1Iabl
= IIeal = III-Irbel = 0
becomes. That is, it can be seen that the ratio between the maximum phase of line current change and the value of each line current differs greatly only in the healthy line phase compared to the other cases. Here, if the ab phase and the ca phase are IPU, the be phase is OPU. In addition, in the event of a fault involving two or more lines, the amount of change in current between each line will be approximately 50 degrees or more compared to the maximum value. For example, in the case of a be-phase two-wire short circuit, each phase current is 1, = OIb = -I, = 1. Each line current is IIabl ” 1Ieal = III, 1Ibc
When l = 2111, each line current is 1/2 of the maximum line phase current. That is, if the be phase is IPU, then the ab phase=ca phase=1/2 PU. To summarize the above, when a system fault occurs in a directly grounded system, the fault current (change current) is as shown in Table 1 according to the fault type.

Table 1 [Eng. ') I Il'Il)',Ib' I
. /, ■. t-I, tl, 1.1b/, 1c'; Current for each phase change = CI person'] [IA'] m□; (:1.
':) The largest one a, b, c: phase name. It can be seen from Table 1 that if the above-mentioned detection is performed, it is possible to distinguish between a single wire ground fault fault and a fault involving two or more wires.

FIG. 1 is a functional block diagram of an embodiment for explaining the accident phase selection method according to the present invention. 10 in Figure 1
1 is a failure phase sorting device, which includes a calculating section 11 and a determining section 12, and the determining section 12 is composed of a 1-phase failure detecting section 121 and a 2φ phase or more failure detecting section 122.

FIG. 2 is a flowchart illustrating the phase selection operation, and in this case only simple phase selection is shown. When a system fault occurs, the pre-fault current is immediately memorized, and fault phase selection is performed using the judgment formula described below.

First, in step S21, from the pre-fault current C1,s) and the fault current [I4] among the stored pre-fault currents,
Calculate the changed current (L'). In step 822, the largest one (L': 1 m
Determine ax. In step 23, it is determined whether X is smaller than
Proceed to step 6 and determine that it is an accident involving two or more lines.

The judgment conditions are as follows.

Here, k is set to, for example, 0.2 to 0.3. Also [Eng. ′
]ml is the smallest of [unit Δ']. (1
) formula holds only in the case of a one-line ground fault accident, in which case the fault phase becomes the [workman') min phase. Also [artisan']
mlo is the smallest of [artificers']. Similar results can be obtained even if the accident phase is a phase unrelated to C'm' ]min.

Equation (2) holds true in the case of an O accident with two or more wires, and the accident phase is the maximum phase of C1,').

FIG. 3 is a flowchart illustrating the operation when applied to failure point location. In Figure 3, Stella f831~
The steps up to 834 are the same as the accident phase selection described above, and when the accident phase is determined in step 834, step S3
5 and subsequent fault point location calculations (conventionally known) are performed.

FIG. 4 is a flowchart illustrating the processing contents of another embodiment according to the present invention.

This example is applied to a digital relay, and therefore, when the fault point distance is within a predetermined range (within the protection range), in the Stella F848, except for deriving the trip output to the interrupter, as shown in FIG. This is similar to the embodiment shown in .

According to the above embodiment, fault phase selection can be reliably performed by simple calculation of the changed current, so that the load on the CPU is small and a small and inexpensive digital relay can be provided.

〔Effect of the invention〕

As explained above, according to the present invention, fault phase selection is performed using only the change in current caused by a fault, thereby providing a fault phase selection method that is fast, reliable, has a small program capacity, and is also compact and inexpensive. can.

[Brief explanation of the drawing]

Fig. 1 is a functional block diagram of an embodiment for explaining the fault phase selection method according to the present invention, Fig. 2 is a flowchart for explaining the phase selection operation, and Fig. 3 is a 70-chart when applied to failure point location. , FIG. 4 is a flowchart when applied to a protection relay, and FIG. 5 is a side view of a general digital relay configuration. 10... Accident phase sorting device, 11-... Arithmetic unit, 12-...
... Judgment unit, 121... 1-phase failure detection unit, 12
2...Failure detection unit for two or more phases. Figure 1 Figure 2 Figure 3 Figure 5

Claims (2)

[Claims] (1) In a fault phase sorting method for determining the fault phase at the time of a power transmission line fault based on the fault current value flowing through the power transmission lines constituting the power system, the fault current of the line current of the transmission line and the fault phase The ratio of the current to the maximum value is determined, and if this ratio is smaller than a certain value for one line-to-line phase, it is considered a single-line ground fault, and if all three line-to-line phases are less than a certain value. If the fault is large, it is considered to be a fault involving two or more wires, and in the case of a one-line ground fault, the phase with the maximum change in current for each phase is determined, and in the case of a fault with two or more wires, the phase with the maximum change in current between the lines is An accident phase selection method characterized in that each accident phase is set as an accident phase. (2) Fault phase selection according to claim 1, characterized in that in the event of a one-line ground fault fault, one phase other than the line-to-line phase where the line-to-line current change current is the minimum is determined to be the fault phase. Method.