JPH0112510Y2 - - Google Patents

Description

[Detailed description of the invention] (a) Technical field The present invention relates to a protective relay device, particularly a protective relay device that does not cause erroneous disconnection when switching to a grid after completing a distance relay test.

(b) Prior Art Conventionally, distance relays have been widely used in directional comparison conveyance protection relay devices or back-up protection relay devices. In general, a Moh distance relay having characteristics shown in the RX diagram as shown in FIG. 1 is used to protect power transmission lines. As can be seen from this characteristic diagram, the Moh distance relay has the ability to identify direction, and does not operate in the event of an accident behind it, but responds only to accidents in the internal direction, so it is used to detect the direction of the accident point. .

However, a normal short-circuit Maw distance relay that receives the system line voltage V and phase-to-phase current I as input becomes inoperable in the event of a short-circuit accident at a close point where the system voltage drops to zero. Here, the operation formula of an electromagnetic type Moh distance relay for detecting a short circuit accident which receives line voltage V and phase current I as input is generally as follows.

VICOS (θ−φ)−K ₁ V ² >K ₂ …(1) In formula (1), θ is the advance angle of input voltage V with respect to input current I, K ₁ and K ₂ are constants, and φ is the maximum torque angle It is. In equation (1), when the input voltage V=0, it becomes inoperable.

On the other hand, the operating formula of the Moh distance relay for detecting ground fault faults usually introduces the line voltage of the healthy phase as the polarity quantity, and is not affected by the fault phase voltage and can operate even in the case of internal one-wire ground faults. It is said that Furthermore, since short-circuit accidents are usually detected using a Moh distance relay for detecting short-circuit accidents, it is usually unnecessary to consider the closest point when using a Moh distance relay for detecting ground fault faults.

Normally, a voltage memory circuit is installed for the short-circuit fault relay, which becomes difficult to operate in such an internal short-circuit accident at a close point, and stores the grid voltage before the accident for several cycles. This problem is solved by operating the voltage and fault current for a period in which the voltage is stored.

The above-mentioned Maw distance relay 3 is used as a protection method for power transmission lines.
The second example of a three-stage distance relay method using a
and Fig. 3. Figure 2 shows three Maw distance relays: a first Maw distance relay M1 (hereinafter referred to as M1), a second Maw distance relay M2 (hereinafter referred to as M2), and a third Maw distance relay M3 (hereinafter referred to as M3). The torque angle is set to the maximum torque angle with respect to the impedance of the power transmission line. Also, A, B, and C on the impedance lines of the power transmission line are respectively A electric station,
Electrical station B and electric station C are shown, and correspond to A, B, and C in FIG. 3 shown below, respectively. In Figure 3, the vertical axis is time T, and the horizontal axis is impedance Z, which also serves as a system diagram.
It is assumed that M1, M2, and M3 in FIG. 2 are set as shown in the figure. First of all, the first stage M1 is about 80 to 90% from the relay installation point to the next terminal B.
The second stage M2 is the remaining 10 to 20% of the first stage M1 setting and approximately 20 to 50% of the next section (B-C), and the second stage M2 is set to about 20-50% of the next section (B-C) while)
In coordination with the first stage, a time-limited shutdown will occur. or,
The third stage M3 is a time-limited shutdown that is later than the second stage M2 as backup protection for a further distant accident.

Generally, ultra-high voltage systems are protected by two systems, and the distance relay method is often used mainly as backup protection. Accidents can be detected accurately in the case of multiple faults, and if the phase comparison method for each phase that performs multiphase reclosing or the differential current method for each phase is used as the main protection and the distance relay method is used as backup protection. Priority is given to main protection because of its high detection ability and the need to perform multiphase reclosing, and the primary protection is
It is necessary to limit the stage cutoff to a limited time. (Normally, the distance relay system is 3-phase cutoff.) If the above-mentioned Maw distance relay is used and the time-limited setting of the first stage is longer than several cycles of memorization, the main protection may malfunction and trip. If this is not done, there will be a problem that the output of the Maw distance relay will disappear before the first stage time limit elapses, making it impossible to shut off the relay.
As a countermeasure to this problem, a method is currently being adopted in which, once the Maw distance relay operates, it is held until the accident detection relay returns to its original state, thereby making it possible to reliably shut off the relay. In this method of holding the output of the motor distance relay, the fault detection relay always operates in the event of a system fault and returns after being cut off, making it possible to release the holding state. However, when an overcurrent relay is used as the fault detection relay, when testing the device by applying a test input from the test terminal to the relay device, a case may occur in which the output of the motor distance relay is held and cannot be released. An example of this problem will be explained next. When switching the relay input voltage from the grid voltage to the test voltage, or from the test voltage to the grid voltage, the voltage test terminal is pulled out once, so the voltage input to the relay disappears, and the Maw distance relay operates and is maintained. During the test, both the voltage and current inputs are supplied from the tester, so the input current is zero except for simulated accidents, and the output of the Maw distance relay is canceled, so there is no particular problem. After the test, when switching to grid input, if the voltage test terminal is finally connected, the voltage input becomes zero, and the Moh distance relay operates once and maintains its output. On the other hand, the input current is the power flow of the system, and if the overcurrent relay is in a set operating state, the output once activated by the motor distance relay will not be released and will remain held.

This will be explained with reference to FIGS. 4 and 5. Fourth
The figure shows electric station A, with bus 1, transmission line 2,
It is composed of a circuit breaker 3, an instrument current transformer 4, an instrument transformer 5, a Moh distance relay 6, a voltage test terminal 7, and a current test terminal 8. Further, FIG. 5 is composed of a flip-flop 21 having a set input S, a reset input R, and an output Q, and a not circuit 31A. The fault detection relay output FD is not shown in this diagram, but the fault detection relay output, ZONE 1
is the output of the first stage fault detection by the motor distance relay 6, and T is the output of the flip-flop 21.
In FIG. 4, under normal conditions, the test terminals 7 and 8 are in a connected state, and the system voltage and current are applied to the Moh distance relay 6. In testing the relay device, if the voltage test terminal 7 is opened while the current test terminal 8 is connected and the test voltage is connected to the Moh distance relay 6, the voltage input to the Moh distance relay 6 will temporarily become zero. Therefore, the motor distance relay 6 operates,
The ZONE1 input in FIG. 5 is held by the holding circuit 21, and the first stage tripping condition T is output. However, during the test, the tripping circuit is normally locked and the test current is also applied to the Moh distance relay, so the input current is zero except for the simulated accident, and release of holding is possible without any problem. However, after the test was completed and the current test terminal 8 was connected and switched to grid current,
When switching the voltage test terminal 7 to the grid voltage, there will be a current input but once there will be no voltage input, so
If the overcurrent relay is operating with power flow even after output ZONE 1 of the motor distance relay is output and switched to the grid voltage, the first stage fault detection FD is "1" and there is no reset input and the flip-flop is activated. The output T of 21 remains held. If the trip lock is released and operation is started in this state, an accident may occur in the external direction.
There is a problem that the end circuit breaker 3 may trip accidentally. Therefore, when the device is put into operation after testing, it is necessary to turn off the power switch and then turn it on again.

(c) Purpose of the invention This invention was made with the aim of solving the above-mentioned problems. It is an object of the present invention to provide a protective relay device that automatically releases the holding circuit when connected to a power grid, thereby preventing erroneous tripping.

(d) Examples Examples will be described below with reference to the drawings. FIG. 6 shows an embodiment of the protective relay device according to the present invention.
Reference symbols 21, 31A, ZONE1, T, and FD in the figure correspond to those in FIG. 5, respectively. 31 is a knot circuit,
41 is an AND circuit, 51 is a time-limited operation timer, 6
1 is an OR circuit. In Fig. 6, when the relay device test is completed and the voltage test terminal is switched to the grid voltage, the input voltage is zero and the first stage fault detection output ZONE1 of the Moh distance relay 6 is activated once, and the Even if the stage tripping output T is maintained, the time-limited operation timer 51 is activated due to the AND41 between the first stage fault detection output ZONE1 switching to the grid voltage and the first stage tripping output T. After the settling time has elapsed, the hold is released and the normal state is restored. As a result, after the relay device test is completed, the output of the Moh distance relay by switching the voltage input reliably releases the held circuit and returns it to its normal state, eliminating any malfunctions.

The holding release time-limited operation timer 51 is for reliably issuing a shut-off command in the event of an internal accident.
The settling time may be set to be longer than the settling time of the time-limited operation timer for first stage cutoff.

(e) Effect of the invention As explained above, according to the invention, once the test is completed and the power supply terminal is switched to the grid, the trip output when the voltage temporarily becomes zero and the output when the voltage is switched to the grid voltage. Since the output holding is released after the settling time has elapsed due to the subsequent recovery output, the normal protection function can be restored without requiring a troublesome reset operation using a switch. Although the embodiment of the present invention has been described using a three-stage distance relay method, it can also be easily applied to a protective relay device that maintains the output of a directional element using a direction comparison method.

[Brief explanation of the drawing]

Figure 1 is a characteristic diagram of the Moh distance relay, Figures 2 and 3 are diagrams to explain the three-stage time-limited distance relay system, and Figure 4 shows the characteristics of the Moh distance relay shown in Figure 1 installed in the power system. FIG. 5 is a diagram showing a conventional first-stage holding circuit for countermeasures against point-of-proximity accidents, and FIG. 6 is a diagram showing an embodiment of the present invention. 6...Maw distance relay, 7...Voltage test terminal, 8...Current test terminal, 21...Holding circuit,
41...AND circuit, 31, 31A...NOT circuit, 51...Time-limited operation timer, 61...OR circuit.

Claims (1)

[Scope of Claim for Utility Model Registration] A protective relay that performs time-limited interruption, consisting of a distance relay that inputs voltage and current from the power system, and a holding circuit that holds the output from the distance relay until the fault detection relay returns to normal. In the electric device, the distance relay operates and the holding circuit maintains this output on the condition that the holding output of the holding circuit and the return output of the distance relay continue for a certain period of time longer than the time limit cutoff. A protective relay device characterized by releasing a holding output.