JPH0471322A - Distance relay - Google Patents

Abstract

PURPOSE:To rapidly remove an accident in one or two phases by discriminating that output signals of a number-of-phases discriminator for discriminating operation of one or two phases, and a second stage distance discriminator of the number-of-phases discriminator and a distance relay are simultaneously satisfied, and breaking three phases. CONSTITUTION:When three phases are broken by a first stage distance discriminator of a distance relay mounted at an opponent end bus B side, the fault continues in an overcurrent detector 12 of a first phase, and the operation is hence held, but overcurrent detectors 13, 14 of second and third phases are interrupted. Here, an output of an inverter 18 for detecting the interruptions of three phases of the detectors 12-14 continues the interruption. Accordingly, the output of an inverter 20 for detecting one or two phase operations of the detectors 12-14 is altered from an interruption to an operation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Field of Application) The present invention is applied to a distance relay that introduces electricity from a power system and operates in response to a system fault within a set distance setting range.

(Prior art) A distance relay is a device that inputs electrical quantities such as current and voltage from the power system, and trips a circuit breaker when the distance to the fault point is within the operating range of the distance setting value based on the input at the time of a fault. It is.

For example, as shown in the power system diagram of Fig. 6, the distance relay l inputs the voltage from the bus 3A of the power station A on the generator 2 side through the instrument transformer 4, and connects it to the bus 3B of the power station B on the generator 2 side. The amount of current is input from the power station A side of the power transmission line 5 to be connected to be protected via the instrument transformer 6. Fault point F is distance relay 1
If the distance is within the first stage distance setting, which is the operating range of , a trip signal is output to the breaker 7.

Generally, the first stage distance setting range of the distance relay 1 is set between electrical stations A and B, taking into account the error of the distance relay 1, the error of the instrument transformers 4 and 6, the constant error of the power transmission line 5, etc. No. 8
The impedance value is set to be approximately 0% proportional to the distance.

The second stage distance setting range of the distance relay 1 is used to protect the remaining 20% of the two sections between transmission lines A and B that exceed the first stage distance setting range, and to protect the busbar protection relay for the busbar 3B of electric station B. As a back-up protection against the failure of the distance relay connected to the bus 3B or the failure of the circuit breaker, the distance relay is set to approximately 1.5 times the first stage distance setting range, and the second stage distance setting range exceeding the first stage distance setting range is set to 1.5 times the first stage distance setting range. In the event of an accident within the stage distance setting range, a timed cutoff will be implemented.

(Problem to be Solved by the Invention) By the way, it is possible to eliminate accidents at high speed even in the remaining 20% section between transmission lines A and B that exceeds the first stage setting range of the distance relay 1 described above. This is desirable in order to provide a reliable power supply.

Methods for this purpose include the blocking method, the overreach method, the direction comparison distance relay method, and the underreach method, the transfer relay method.

However, as described above, both require the use of transmission means such as power line carriers to receive the operation information of the distance relay on the other side, and have the drawback of requiring expensive transmission equipment.

Therefore, the present invention can quickly detect one-phase or two-phase faults, which account for the majority of three-phase power system faults, based on the current and voltage information of the own terminal without using expensive transmission equipment. The purpose is to provide a distance relay that can be removed.

[Structure of the invention]

(Means for Solving the Problems) The distance relay of the present invention includes a first stage distance determination circuit, a second stage distance determination circuit, a time limit circuit into which an output signal of the second stage distance determination circuit is input, and an output circuit. The overcurrent detection circuit for each phase detects the presence or absence of power flow in the distance relay configured, and the number of phases that inputs the output signal of this overcurrent detection circuit to determine whether the 1-phase or 2-phase overcurrent detection circuit has operated. judgment circuit,
A logic circuit is added that determines whether the output signals of this phase number determination circuit and the second stage distance determination circuit are both established.The output signal of this logic circuit is introduced into the output circuit, and the three-phase It is configured to generate a cutoff output signal.

(Function) The first-stage distance determination circuit generates an operational output when the fault point is within the first-stage distance setting range, and outputs a three-phase trip signal from the output path to the breaker.

The second stage distance judgment circuit generates an operation output when the fault point is within the second stage distance setting range, and the next stage time limit circuit provides backup protection for the other bus and backup protection for the power transmission line connected to the other bus. After a time-limited operation delay necessary for protection is performed, a three-phase trip output signal is outputted from the output circuit to the circuit breaker.

Accidents in the remaining 20% of the transmission line protection section that exceed the first stage setting range of the distance relay are quickly eliminated by the configuration described below.

Each phase overcurrent detection circuit is a circuit that introduces the amount of current from the three-phase power system and detects the presence or absence of power flow, and generates an output when the current value is equal to or higher than a predetermined set value.

This set value is set to a value that allows detection of the presence or absence of power current, that is, a value that is larger than the charging current of the power transmission line to be protected. Therefore, each phase overcurrent detection circuit generates an operating output when the system fault current exceeds the set value or when the power flow is constant, and when the charging current or current is zero, that is, when the breaker at the other end or the own end is in an open state. does not generate any operational output. In other words, depending on the operating state of each phase overcurrent detection circuit, the open/closed state of the breaker at the other end or the own end can be known. The output signal of each phase overcurrent detection circuit is introduced into a phase number determination circuit at the next stage, and an operation output is generated when the one-phase or two-phase overcurrent detection circuit is in an operating state.

The logic circuit generates an output signal when both the output signals of the phase number determining circuit and the second stage distance determining circuit are established.

The relationship between the operational output of the logic circuit and the failure point of the system is explained as follows.

(υ For accidents within the remaining 20% section to the other side's bus line where the fault point exceeds the first stage distance setting range, it is first detected by the first stage distance judgment circuit of the distance relay installed at the other side's terminal, and protection is applied. A three-phase breaker installed at the opposite terminal of the target power transmission line performs 3-phase cutoff.

The first stage distance determination circuit of the distance relay of its own terminal is inoperative because the accident is outside the first stage distance setting range, and the second stage distance determination circuit is activated. If the fault is a 1-phase or 2-phase fault, the 2-phase or 1-phase transmission line current will be reduced to the charging current value due to the 3-phase cutoff at the other terminal, so the corresponding 2-phase or 1-phase overcurrent relay circuit The operating output of becomes zero.

Therefore, the phase number determination circuit in the next stage determines that the one-phase or two-phase overcurrent detection circuit is operating, and generates an operation output. In the next stage logic circuit, since the output signals of the phase number determination circuit and the second stage distance determination circuit are both established, an operation signal is generated, and a three-phase cutoff output is generated from the next stage output circuit.

If the fault occurs in three phases, the output signal of the overcurrent detection circuit becomes an operation signal for all three phases, so the phase number determination circuit does not generate an operation signal. Regarding this triple sum accident, the accident is removed by normal backup protection by the second stage distance determination circuit and the next stage time limit circuit of the self-end distance relay.

■ If the fault point occurs on the other side's bus or another power transmission line connected to the other side's bus, a three-phase cutoff will be performed at the corresponding breaker to protect the other side's bus or transmission line. The overcurrent detection circuit at its own end operates on all three phases before the three-phase cutoff, and after the three-phase cutoff, either all three phases operate or all three phases become inoperable depending on the position of the fault point, so the phase number determination circuit outputs an operating signal. is not output.

■ If the fault point is within the first stage distance setting range of the self-end distance relay, regardless of the fault type, the output of the overcurrent detection circuit will operate for all three phases before the three-phase cutoff, and will operate after the three-phase cutoff. 3
Since both phases become non-operating signals, the phase number determining circuit does not output an operating signal.

(Example) An embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a configuration diagram showing a distance relay 1 of the present invention.

Three-phase AC voltage and current introduced from the power system are input to the distance relay 1 via an instrument transformer.

8 is a first stage distance determination circuit, 9 is a second stage distance determination circuit, 1
0 is a time limit circuit which inputs the output signal of the second stage distance judgment circuit 9 and delays the operation by a predetermined time required for backup protection, and the output signals of the first stage distance judgment circuit 8 and the time limit circuit 10 are logically summed. The signal is introduced into an output circuit 11 consisting of a circuit, and outputs a breaker three-phase tripping signal from the output circuit 11. 1
2, 13. 14 is an overcurrent detection circuit that inputs the 1st, 2nd, and 3rd phase currents and operates based on tidal current, and 15 inputs the output signals of the overcurrent detection circuits 12 to 14 to detect 1-phase or 2-phase overcurrent. This is a phase number determination circuit that determines whether the detection circuit has operated. The phase number determination circuit 15 includes, for example, an AND circuit 16 that detects that the three-phase output signals of the overcurrent detection circuits 12 to 14 are both in operation, and an overcurrent detection circuit 12 to
an OR circuit 17 and an inverting circuit 18 that detect that the three-phase output signals of 14 are both inactive; an OR circuit 19 that detects that both the output signals of the AND circuit 16 and the inverting circuit 18 are active; It is constituted by an inverting circuit 20 that inputs the output signal of the OR circuit 19 and performs inverted logic,
When the overcurrent detection circuits 12 to 14 are in one-phase or two-phase operation, the output signal of the inverting circuit 20 is in operation.

Reference numeral 21 denotes a time-limited operation circuit which inputs the output signal of the inversion circuit 20 and delays the operation for a predetermined period of time, and detects the difference in the cut-off time for each phase when three phases are cut off, and the overcurrent detection circuits 12 to 21.
This is inserted for the purpose of preventing the phase number determination circuit 15 from temporarily outputting an operation signal due to the difference in the operation and recovery times of 14 for each phase.

22 is an AND circuit that outputs an operation signal when the output signals of the second stage distance determination circuit 9 and the phase number determination circuit 15 are both established, and the output signal of the AND circuit 22 is cut off via the output circuit 11. This becomes a 3-phase tripping signal.

Next, in the above-mentioned distance relay, we will use the output waveform diagrams in Figures 2 and 3 to calculate the operational response when a system fault occurs within the remaining 20% section from the first stage setting range to the other bus. I will explain. The distance relay 1 according to the present invention is installed at both ends A and B of the power transmission line, but the output waveform diagrams in FIGS. 2 and 3 are explained by taking as an example the distance relay installed at the A end of the power transmission line. This is a diagram. Figure 2 shows that the accident occurred only in the first phase at time t. The first stage distance determination circuit 8 is inactive and the second stage distance determination circuit 9 is activated at time t, but since the accident point is near bus line B, it is used for backup protection. The output of the time limit circuit 10 remains inactive until time t6.

When three-phase cutoff is performed at time t2 by the first stage distance determination circuit of the distance relay installed on the opposite end bus B side, the overcurrent detection circuits 12 to 1 of the distance relay 1 installed on the bus A side
14, the first phase overcurrent detection circuit 12 maintains its operation because the accident continues, but the second and third phase overcurrent detection circuits 13 and 14 keep operating at time t.
3 and t4, respectively, from operation to inoperation. At this time, in the phase number determination circuit 15, the overcurrent detection circuits 12 to 1
The output of the AND circuit 16 that detects the three-phase co-operation of the overcurrent detection circuits 12 to 14 changes from operating to non-operating at time t3, and the output of the inverting circuit 16 that detects the non-operation of the three phases of the overcurrent detection circuits 12 to 14 changes from operating to non-operating at time t3.
The output of No. 8 continues to be inactive. Therefore, the output of the inverting circuit 20 that detects one-phase or two-phase operation of the overcurrent detection circuits 12 to 14 changes from non-operation to operation at time t4.

The difference in the breaker opening time for each phase during three-phase cutoff, the operation for each phase of the overcurrent detection circuits 12 to 14, and the difference in recovery time are as follows:
The output signal of the AND circuit 22 is absorbed by the time limit operation circuit 21, and the operation output of the phase number determination circuit 15 is finally generated from the time limit circuit 21 at time t5.
Since the output signals of the stage distance determination circuit 9 and the phase number determination circuit 15 are both established, the circuit is activated, and the output circuit 11 outputs a breaker three-phase tripping signal.

FIG. 3 shows time t. It also shows the response of distance relay 1 when a three-phase fault occurs at time t2, and even after three-phase cutoff is performed at time t2 at the other terminal, the fault continues at the own terminal, so overcurrent is generated. Detection circuit 12-1
4 continues to operate, the output signal of the phase number determination circuit 15 is inactive, and the output signal of the AND circuit 22 is determined because both the second stage distance determination circuit 9 and the phase number determination circuit 15 are not satisfied. , is inactive. At time t6, the output signal of the backup protection time limit circuit 10 is activated, and at this point, the output circuit 11 outputs the breaker three-phase tripping signal, eliminating the accident.

FIG. 4 shows time t. It shows the response of the distance relay 1 on the bus A side when a 3-phase fault occurs at the other side bus B1] - -12=, and as the 3-phase fault is implemented at the other side terminal at time t2, the time Overcurrent detection circuit 12-1 at t3-t4
The output signals of No. 4 change from active to inactive for all three phases.

Due to the difference in the return time for each phase of the output signals of the overcurrent detection circuits 12 to 14, an output is temporarily generated within the phase number determination circuit 15 to the inverting circuit 20. Since the second temporary output is absorbed, the output signal of the phase number determination circuit 15 is inactive, and the distance relay 1
does not output a 3-phase cutoff signal. The above explanation can be similarly applied to a 1-phase fault and a 2-phase fault, and the distance relay 1 is inoperative in this case as well.

FIG. 5 shows time t. shows the response of the distance relay 1 on the bus A side when a first phase internal fault occurs on the transmission line near its own end, and in this case, the distance judgment circuits 8 and 9 of the first stage and second stage operate respectively. A breaker three-phase tripping signal is output from the first stage distance determination circuit 8 via the output circuit 11.

After the breaker three-phase is tripped, at time t2, the first stage and second stage distance determination circuits 8, 9, and overcurrent detection circuits 12-
14 is restored, but the output signal of the phase number determination circuit 15 is inactive, and no breaker exception signal is output after time t2.

As explained above, 1-phase or 2-phase faults, which account for the majority of 3-phase power system faults, can be eliminated at high speed based on the current and voltage information of the own terminal without using expensive transmission equipment. .

〔Effect of the invention〕

Therefore, the present invention provides distance relay protection for power transmission lines that performs three-phase cutoff by providing an overcurrent detection circuit for each phase to detect the presence or absence of power flow, and controlling the one-phase or two-phase operation of each phase overcurrent detection circuit. Since the three-phase cutoff is performed based on the result of this judgment and the operating conditions of the second stage distance judgment circuit, it is possible to obtain a distance relay that can eliminate one-phase or two-phase faults at high speed with a simple configuration.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the distance relay of the present invention, FIGS. 2 to 5 are output waveform diagrams of the distance relay of the embodiment, and FIG. 6 is a power system diagram to which the distance relay is applied. 1... Distance relay 8... First stage distance determination circuit 9
...Second stage distance determination circuit 10...Time limit circuit 11
... Output circuit 12.1.3.14 ... Overcurrent detection circuit 15 ... Phase number judgment circuit 22 ... AND circuit Agent Patent attorney Noriyuki Chika

Claims (1)

[Claims] Overcurrent detection circuit for each phase that detects the presence or absence of power flow in a distance relay that uses the voltage and current of a three-phase AC power system to determine whether the fault point is within the distance setting range and disconnects or disconnects three phases. And, it is determined that the output signals of the phase number determination circuit that determines one-phase or two-phase operation of each phase overcurrent detection circuit, this phase number determination circuit, and the second stage distance determination circuit of the distance relay are both established. A distance relay characterized by comprising a logic circuit that connects and disconnects three phases.