JPS5932973B2 - Multi-line ground fault protection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a multi-line ground fault protection device for detecting and protecting against multi-line ground faults in distribution substation C.

Generally, a ground fault protection device in a power distribution substation I is constructed as shown in FIG.

1 is the main transformer, 21 to 2o are circuit breakers, and 51 is a bus bar, and when a ground fault occurs on the bus bar 5□ or the distribution lines 52 to 5nI, the zero-phase voltage V, as is well known.

occurs, and this voltage V. is obtained by the voltage transformer 4.

Additionally, zero-sequence current transformers 3□-3o are installed on each distribution line 5□-5n, and the zero-sequence current 1 flowing in the event of a ground fault occurs.
01 to ■oo are detected.

8 is a ground fault overvoltage relay, and the zero-sequence voltage ■ obtained from the zero-sequence voltage detection line 7.

When becomes larger than a predetermined value (this operation occurs).

6,~6o are earth fault direction relays, earth fault direction relays 6□~
6n performs phase discrimination of the input zero-sequence current and voltage, detects ground faults in the protection section of each relay, and the detected relay issues a trip signal to the circuit breakers 2□ to 2n-1 to protect them. Cut off the section.

The trip signal is an AND output of the ground fault direction relays 6□ to 6o and the ground fault overvoltage relay 8.

Incidentally, in recent years, in this type of power distribution substation, equipment operations, current, voltage, power records, etc. have been automated to save labor in substation maintenance. It is easier to handle information obtained from voltage/current transformers at substations by converting it into digital quantities.

In recent years, digital processing of current and voltage has become effective in comprehensive protection control using information on multiple electric power stations, especially due to increases in power transmission voltage and capacity, as well as longer distances. Although many systems have been proposed for power distribution substations, the trend toward digitalization is also rapid.

In order to make the entire relay system of a power distribution substation digital, the effectiveness cannot be measured simply by replacing the conventional relays shown in Figure 1 with computerized relays.

In other words, in order to take advantage of the essential benefits of digitalization, such as faster failure detection and labor-saving maintenance and inspection, it is necessary to make effective use of the advanced judgment functions of microcomputers and minicomputers.

The present invention has been made in view of the above circumstances, and uses digitally quantified zero-sequence voltage and current at a predetermined sampling period to protect a large number of distribution lines from ground faults at a distribution substation. It is an object of the present invention to provide a multi-line ground fault protection device that can speed up failure detection and save labor in maintenance and inspection since the processing is carried out by a control device.

An embodiment of the present invention will be described in detail below based on the drawings.

FIG. 2 shows an outline of a multi-line ground fault protection device to which the present invention is applied, and the same reference numerals as in FIG. 1 indicate the same or corresponding parts.

In FIG. 2, the zero-sequence voltage information obtained by the voltage transformer 4 is Iok (k = 1, 2, ..., n-1
) is the zero-sequence current information obtained from the 3kl zero-sequence current transformer.

Each piece of information is held and sampled at a fixed cycle or arbitrarily at the same time by sampling and holding circuits 90 to 91-1, and then A/D converted by an analog-to-digital converter 11 at a predetermined cycle via 10 multiplexers to become digital data. , computer (hereinafter referred to as CPU)
12 is input.

The processing within the CPU 12 is shown in a flowchart in FIG.

First, zero-phase voltage data V is obtained by step rlJ.

is taken in to obtain an effective value or an amount proportional to this, and in step "2" f, it is determined whether the value is larger than the determination condition value.

This judgment part corresponds to the ground fault overvoltage relay 8 in Fig. 1,
Ground fault voltage V.

This is a ground fault determining means that determines whether or not a ground fault has occurred.

If the determination result is Jnoj, no ground fault is detected, so the process returns to step "1" and V of the next sampling data is determined.

This is repeated until ryes, J is obtained in step "2".

When the result is "yes", the ryes and J signals are sent to step "3" in order to detect a ground fault in the distribution line for the first time.

In step "3", first V. and the zero-sequence current data 1 obtained by the zero-sequence current transformer 3 installed on the first distribution line 5□
1, phase discrimination is performed by the phase discrimination means, and the determination is made in step "4".

If a ground fault has occurred in the first distribution line 5□, the ground fault is detected in step "4" and a yeS signal is generated.

The yes signal becomes a trip signal for the breaker 2□ and is outputted from the CPU 12 (new breaker command output means).
At the same time as tripping breaker 2□, step "5"
is also sent to switch 5 in this step r5J.
W=SW+1F and sent to step "6".

Note that SW is a counter representing address contents and is set as 5W=O between steps "2" and "3".

The reason for adding 1 to SW+1 when a yes signal occurs is that ground faults can occur not only in the distribution line but also on the bus 51. It is used as an identification signal.

If no ground fault is detected in step F4J (in this case, the no signal goes directly to step "6").

Therefore, steps r3J, r4j, and r5J are for detecting a ground fault in the first distribution line 5□.

Next, the second power distribution line 53 (even if this occurs, similar detection is performed in steps r6J, r7J, and r8J).

In other words, V at steps r6J and r7J.

and 1°2 phase discrimination and its judgment, and if yes, issue a new command to cut off the circuit breaker 23 at step "8", and after 5W = SW + 1c, the third
A similar detection is performed for the distribution line 54.

If no in step “7” (also, the third distribution line 54
(I got stuck and performed the same detection.

This detection is repeated in the same manner.

Finally, step [9J, ■ in rlOJ.

and '0n-1 and its determination is performed, and in YES, a new command is issued to cut off the circuit breaker 2n from step [1xJt, and sw=sw+i is set.

In step "12", it is determined whether 5W=O or not. For example, if an accident has occurred in the first and second distribution lines, 5W=SW
Although it is +2, if SW-〇, it means that no ground fault was detected in any distribution line.

In this case, there is a possibility of a ground fault on the bus bar 51, so
V again.

If it is determined that a ground fault has occurred for a predetermined period of time, an alarm is issued or a predetermined breaker (for example, 21) is shut off to eliminate the fault.

The busbar accident determination means issues this warning or a shutdown command.

Now, in the above-mentioned protection method, when detecting a ground fault in a distribution line, the data at the local point is taken in, converted into an effective value, and judged.
In another embodiment of the present invention, data at the time of occurrence of a ground fault may be stored in the storage section of the CPU 12, and this data may be used to determine in which distribution line a ground fault has occurred.

The data storage device stores each data of each distribution line and V.

A device that stores data for a predetermined period of time (for example, one cycle).The stored data is constantly updated, and at the time of a ground fault, the latest data at the time of the fault is stored for each distribution line I remember.

However, if it is determined that an accident has occurred, data updating is interrupted at that point, and ground fault detection for each distribution line is performed using the data stored in the storage device.

Furthermore, if necessary, data for a certain period of time after it is determined that an accident has occurred may be stored, and ground fault accident detection may be performed using the stored data.

The flowchart is shown in FIG. 4.

The parts that are different from the flowchart in Figure 3 are A.
The data of the continuous power distribution line is 1°k (k = 1.

2,...n-1) and V.

The data stored in the storage device (memory) can be used to detect ground faults in distribution lines. It is.

Note that the processing method is the same as the explanation in FIG. 3.

In this way, sampling will not be performed from the time of YES in step "2" (when the accident occurred), and all data stored in the memo will be protected.
Freed from constraints such as sampling frequency.

Therefore, it is possible to speed up the protection process. As described above, only one multi-circuit earth fault protection relay is sufficient, and the protection system is suitable for a multi-circuit earth fault protection relay, which is extremely efficient.

As described above, according to the present invention, since the zero-sequence voltage and current that are digitally quantified at a predetermined sampling period are used, failures can be detected extremely quickly and labor-saving maintenance and inspection can be achieved. There are effects such as being able to do it.

[Brief explanation of drawings]

FIG. 1 is a single line diagram showing a conventional example, FIG. 2 is a block diagram showing an embodiment of the present invention, and FIGS. 3 and 4 are processing flowcharts in the computer (CPU) 12 shown in FIG. . 9... Sampling hold circuit, 10...
... Multiplexer, 11 ... Analog-to-digital converter, 12 ... Computer (CPU)
.

Claims (1)

[Claims] 1. A zero-sequence voltage detection unit is provided on the bus connected to the power receiving line, and a zero-sequence current detection device is provided for each of the plurality of distribution lines connected to this bus, and the analog voltage detected by each of these detection devices is After sampling the zero-sequence voltage and current signals at a predetermined sampling period and converting them into digital signals,
In a device that is introduced into a control device to detect ground faults, the digitally converted zero-sequence voltage signal is taken in at each sampling and compared with the respective judgment condition values, and the zero-sequence voltage signal is determined. a ground fault determining means that determines a ground fault when the value is larger than a condition value; A sequential phase discrimination means for sequentially discriminating the phase with the zero-phase voltage signal to determine a ground fault; After the new command output means outputs a new command and the sequential phase discrimination means discriminates the phase of the zero-sequence voltage signal and the zero-sequence current signals of all distribution lines, if there is no fault on the distribution line, a bus fault is detected. A multi-line ground fault protection device, characterized in that the control device is equipped with a busbar accident determination means that determines that the power receiving line is damaged and issues an alarm or a new command to the circuit breaker of the power receiving line.