JPS5959013A - Current difference protecting relay unit - 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 [Technical Field of the Invention] The present invention relates to a current differential protection relay device for protecting power transmission lines and electrical equipment in a power system.

[Technical backbone of the invention and its problems]

Protection methods based on the current differential principle include power transmission line protection and transformer protection 2.
It has been widely applied to protect generators, etc., but progress in protection of power transmission lines has been remarkable, with PCM current differential relays, F
M current differential relays are a good example. Typical ratio characteristics of these relays are shown in Figure 1 for an example of a two-terminal system. Also,
FIG. 2 clearly shows the direction and position of the inflow current iAl and the outflow current In in FIG.

In FIG. 1, the solid line indicates that all of the inflow current IA flows out as the outflow current In.
.

IAl, = 180°, which is generally referred to as an external accident trajectory. Characteristic A is the first element 1 aimed at highly sensitive detection when there is no outflow current even when the fault current at the time of an accident within the protected area is small. Since this element is a highly sensitive detection element, there is a risk of malfunction due to current transformer saturation when introducing current to the relay due to incoming current passing between A and 8 in the event of an external accident, or a hardware error in the relay. The current differential relay has a second element 2 with a ratio characteristic of characteristic B to avoid this expected malfunction. For this reason,
In the event of an accident within the protected area, as shown by the hatching in Figure 1,
It is necessary that both characteristic A and characteristic B are within the operating range, and a relay block diagram based on this is shown in FIG.

Now, the problem with this characteristic is a decrease in internal fault detection sensitivity when current passes through the protected section.

That is, although the need for detecting micro-ground faults has recently increased, micro-ground faults are generally caused by trees coming into contact with power transmission lines, etc., and are said to have high ground fault resistance. For this reason,
The first is a slight ground fault when the load current θIC (power flow) passes through the system.
It is difficult to detect with the characteristics shown in the figure, and if necessary, a special relay for the purpose of detecting a slight ground fault must be used, which is uneconomical.

[Purpose of the invention]

The present invention was made in view of the above circumstances, and its purpose is to improve the detection sensitivity in the event of an accident inside the preservation section,
An object of the present invention is to provide an economical current differential film-protected relay system that can also detect small ground faults.

[Summary of the invention]

In order to achieve the above object, the present invention provides a current differential relay that protects power system transmission lines or electrical equipment by using a first element that detects faults within the protection range with high sensitivity in a small current area and a large The kit is made up of a second element that prevents malfunctions due to errors caused by current transformer saturation γi in the current domain, and when the first element and second element operate together, the The present invention is characterized in that one relay output is sent out, and when only the first element operates, a second relay output is sent out after a fixed time period.

Example of invention C] An embodiment of the present invention shown in the drawings will be described below.

FIG. 4 is a block diagram showing an example of the configuration of the current differential protection power system according to the present invention, and the same parts as in FIG. 3 are indicated by the same symbols.

In the figure, AND means that the first and second elements 1 and 2
The output is an AND circuit that receives the output of the circuit as an input, and sends the output as the first relay output via the OR circuit OR. Also, I
NH is an inhibit circuit which uses the output of the first element 1 as a gate input and the output of the second element 2 as an inhibit input, and its output is passed through the timer delay circuit TDK and the above OR circuit OR to the second element 1. The configuration is such that it is sent out as a relay output.

Next, the operation of this configuration will be explained.

Point X in Figure 1 shows an example of a slight ground fault within the protected area when there is a load current (tidal current) passing through the protected area. In the event of an internal accident, a difference current Id between A and In will necessarily occur, and if this is the point X, then the AND of the first element 1 having the conventional characteristic A and the second element 2 having the characteristic B It is not possible to output based on conditions! It will be made by B. On the other hand, the first element 1 with characteristic A operates, but the second element 2 with characteristic B does not operate, and the AND4 case does not hold, but the inhibit circuit INH is established and the time delay circuit (when operating delay)
It passes through TDK and is output after the delay time.

In this case, the maintenance relay device can be roughly divided into main protection relay device ffJ',
and backup protection relays, and current differential protection relays generally fall into the former category. The main protection device's mission is to detect and cut off large currents in the event of a fault for system stability at high speed 11C, or because the fault current is small and does not threaten system stability in the case of a slight ground fault or °11 fault. Book@tsu”
There is no problem even if the time delay circuit is output after TDE and the accident is removed.

In addition, the time of the time delay circuit TDE is determined by considering the case where the first element 1 malfunctions due to high sensitivity detection due to the passing current at the time of an external fault in the protection section. JE should be set to a value that takes into account the amount of time it takes for the main protection device or back-up protection device in that section to detect and eliminate the accident.

Since this current differential operating relay device is configured as described above, it is possible to significantly improve the sensitivity for detecting a slight ground fault even when there is a load current (tidal current).

Note that this relay device does not necessarily need to be configured within one set of relays as shown in the block diagram of FIG. The second elements may be respective relays, and the respective outputs may be constituted by relay external circuits.

one! In addition, in the above embodiment, the circuit outputs the output after the time delay circuit TDE under the condition that the first element 1 operates and the second element 2 does not operate, but the time delay circuit TDE outputs only when the first element l operates. It may be possible to output the information after a certain period of time. In this case, the operation and non-operation of the second element 2 are not equally involved, but the large current at the time of an accident inside the protected area is caused by the normal first element 1. The AND condition is established with the second element 2 operations,
It is possible to perform high-speed detection and output regardless of the time of the time delay circuit TDE, and a block diagram thereof is shown in FIG.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to provide an economical current differential protective relay device that can improve detection sensitivity in the event of an accident inside a protected area and can also detect a slight ground fault.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the ratio characteristics of a current differential relay, Fig. 2 is a diagram showing the protection system according to Fig. 1, Fig. 3 is a block diagram showing a conventional current differential relay device, Figs. FIG. 5 is a diagram showing one embodiment and another embodiment of the present invention, respectively. 1...first element, 2...second element, AND...
-AND circuit, OR...OR circuit, INH/inhibit circuit, TDE...time delay circuit. Applicant's Representative Patent Attorney Takehiko Suzue Figure 1 Figure 2 Figure 3 Figure 4 ■ Figure 5

Claims (2)

[Claims] (1) In current differential relays that protect power system transmission lines or electrical equipment, the first element is highly sensitive detection of small current areas to detect faults within the protection range, and current transformer saturation in large current areas. and a second element which is designed to prevent malfunction due to errors etc., and when the first element and the second element operate together, the first relay output is sent out, and the 1. A current differential protection relay device, characterized in that when only the first relay operates, a second relay output is sent out after a certain period of time. (2) The first element and the second element are each independent relays, and an accident is detected under the AND condition of each output.
A current differential protection relay device according to claim 1, wherein an accident is detected after a certain time period when only a relay equipped with the above elements operates.