JPH0124010B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a protective relay device that transmits and collects the amount of electricity at each terminal and detects a failure.

[Technical background of the invention and its problems] There are various types of relay devices that protect conventional power systems, but the current differential FM carrier protection relay device uses the FM modulation method (frequency modulation method). The transmission method used transmits and collects the instantaneous values of the currents at each terminal, and in the case of an external failure or under normal conditions, the relay will not operate because the sum of the currents will be zero.
In the case of an internal failure, the sum of the currents becomes a differential current corresponding to the current at the failure point, which causes the relay to operate.

An example of such a transport protection relay device will be described with reference to FIGS. 1 and 2.

In FIG. 1, the A end and the B end (not shown) are interconnected by a power transmission line 1, and a current transformer 2 is provided at each terminal. 3 is a directional ground fault relay, which responds to ground faults by inputting the zero-sequence current of the power transmission line 1 and the neutral point current I _N of the main transformer (not shown). Reference numeral 4 denotes a current differential relay, which responds to the current difference between each phase (R phase, S phase, T phase) of the A terminal and the B terminal. 5 is an input transformer, 6 is a transmitter, 7 is a receiver,
8 is a determination circuit, in which the current at the A end detected by the input transformer 5 is FM modulated by the transmitter 6, and transmitted to the B end via the carrier end station device 9 and the wireless device 10;
Further, the current signal at the B end is received by the wireless device 10, inputted to the receiving section 7 via the carrier end station device 9, and FM demodulated there. The determination circuit 8 detects the current difference between the A terminal and the B terminal, and has operating characteristics in the shaded area in FIG. Reference numeral 11 denotes a constant monitoring circuit which inputs the own terminal current and the other terminal current, and monitors defects such as gain fluctuations of the current differential relay 4 by utilizing the fact that the difference current is always zero.

In FIG. 3, 30 indicates a slight ground fault or disconnection. 3a, 4a, and 31a are output circuits of a directional ground fault relay 3, a current differential relay 4, and a failure detection relay 31, which will be described later. 32 is an AND circuit which outputs the AND of the output signals of the output circuits 3a and 4a.
A delay circuit 33 delays the output signal of the AND circuit 32 by a set time _T1 . 34 is a knot circuit, which inverts the output signal of the output circuit 31a. 35 is an AND circuit, which outputs the AND of the output signals of the delay circuit 33 and the NOT circuit 34 as a trip signal.

In FIG. 4, 11a is an output circuit of the constant monitoring circuit 11, 40 is a delay circuit, and the output circuit 11 is
The output signal of a is delayed by a set time _T2 . A defect detection relay 31 responds to the output signal of the delay circuit 40.

Now, if a slight ground fault occurs on power transmission line 1, A
A difference occurs between the currents at the end and the B end, the current differential relay 4 at the A end operates, and a signal of logic level "1" is output from the output circuit 4a. Further, the directional ground fault relay 3 operates by inputting the zero-sequence current of the slight ground fault and the neutral point current of the transformer, and a signal of "1" is output from the output circuit 3a.

Furthermore, due to the difference in current between the A terminal and the B terminal, the constant monitoring circuit 11 operates, and the output circuit 11
"1" is output from a. Output circuits 3a and 4
Since both the outputs of a become "1", the output of the AND circuit 32 becomes "1", and after the set time _T1 ,
The output of the delay circuit 33 becomes "1". At this time,
If it is set so that T ₁ <T ₂ , the AND condition of the AND circuit 35 is satisfied and a trip command is given to a disconnector (not shown).

As described above, in order to improve the reliability of the current differential relay 4, the constant monitoring circuit 11 is provided to constantly monitor that there is no differential current in the system. Therefore, the constant monitoring circuit can operate sufficiently with the difference in current that occurs due to an accident or a slight ground fault within the protected area. By the way, in the case of a normal accident, it is possible to quickly disconnect the shear breaker at high speed with another shear disconnection circuit, but in the case of a slight ground fault, the shear breaker will be suddenly disconnected after the set time T ₁ . Become. On the other hand, the constant monitoring circuit 1 shown in FIG.
1 operates, and if this operation continues for the set time _T2 , the defect detection relay 31 operates. As the failure detection relay 31 operates, the output of the output circuit 31a in FIG. ing. In other words, a slight ground fault or disconnection is carried out by giving a trip command to the ground disconnector after a set time _T1 after the current differential relay 4 and the directional ground fault relay operate, but a slight ground fault or disconnection occurs. 30 may be locked by the output of the output circuit 31a of the defect detection relay 31, and a slight ground fault may occur or disconnection may not be possible.

A case where such a slight ground fault or disconnection becomes impossible will be explained with reference to FIGS. 5 and 6.

FIG. 5 shows a two-terminal power system, in which the A end and the B end are interconnected by power transmission lines 51 and 52. In addition, each terminal A, B is connected to the above-mentioned transport protection relay device 5.
3,54 are installed. Here, the A end is the power supply end, and the B end is the non-power end. Note that 55 is a power supply behind the A terminal.

If a slight ground fault occurs at _one point near end B, a fault current greater than the setting value of the directional ground fault relay 3 at each end A and B will flow, and both ends A and B will have a current differential. The relay 4 and the directional ground fault relay 3 operate simultaneously, and after the set time _T1 , the breaker is tripped.

However, if a slight ground fault occurs at _two points near end A, the fault currents I _FA ,
I _FB is playing. Due to the relationship between these currents and the line impedance, the fault current I _FA flowing through the directional ground fault relay 3 at the A end is a current greater than the set value, but the fault current I _FB flowing through the directional ground fault relay 3 at the B end is the set value. The current will be less than The directional ground fault relay at the B end can operate only after the A end disconnector is tripped and the fault current I _FB shown by the dotted line flows. Therefore, as shown in FIG. 6, for the A terminal, the current differential relay 4 and the directional ground fault relay 3 operate simultaneously, and the output "1" is generated from the delay circuit 33 before the failure detection relay 31 operates. A disconnection trip is carried out, but for the B end, the A disconnection trip is carried out.
Until the end breaker is tripped, the fault current will be less than the setting value of the directional earth fault relay 3 and the directional earth fault relay 3 will not operate. On the other hand, constant monitoring circuit 1
1 operates simultaneously with the occurrence of an accident, and after a set time _T2 , the failure detection relay 31 operates and the output of the output circuit 31a becomes "1".

Therefore, when the output of the delay circuit 33 becomes "1", the output of the output circuit 31a becomes "1" and the output of the knot circuit 34 becomes "0", and the slight ground fault or disconnection 30 is locked. As a result, a trip command is not output, making it impossible to detect a slight ground fault or break.

In such a device, if a slight ground fault occurs at point _F2 in Figure 5, the directional ground fault relay 3 at the B end will operate after the disconnector at the A end is tripped. Therefore, it had the disadvantage of being unable to cause slight ground faults or break.

[Purpose of the invention]

The present invention has been made in order to eliminate the above-mentioned drawbacks, and provides a protective relay device that can prevent unnecessary locking by a constant monitoring circuit in the event of a slight ground fault, and can reliably perform a slight ground fault or disconnection. With the goal.

[Summary of the invention]

In order to achieve the above object, the present invention provides a current differential relay 4 that responds to the current difference between its own end and the opposite end.
, a directional ground fault relay 3 that operates when a fault current exceeding a set value flows, and a constant monitoring circuit that monitors the current differential relay by utilizing the fact that the current difference is always zero and operates due to a failure. B11 and
Failure detection relay 31 that operates on the condition that the operation of this constant monitoring circuit B11 continues for a set time T ₂
and a first AND circuit 32 that takes the AND of the output signals of the current differential relay 4 and the directional ground fault relay 3;
The output signal of this first AND circuit is set for a time T ₂
First delay circuit 3 with a shorter setting time T ₁ delay
3, and a second delay circuit which receives the output signal of the first delay circuit.
When a slight ground fault occurs at the end closest to the power supply end, the AND circuit 35 is shorter than the difference between the set time T ₂ and the operating time difference of the current differential relay and the directional ground fault relay at the non-power end. A second delay circuit 70 that delays the output signal of the directional ground fault relay by a set time T ₃ , a signal obtained by inverting the output signal of this second delay circuit, and an output signal of the failure detection relay are inverted. An unnecessary lock prevention circuit 74 is provided to supply the input signal to the second AND circuit 35, so that the output of the first delay circuit is at logic level "1".
When this occurs, the output of the unnecessary lock prevention circuit is always set to the logic level "1".

[Embodiments of the invention]

An embodiment of the present invention will be described with reference to FIGS. 7 to 9.

In FIG. 7, 4a is an output circuit of the current differential relay 4, and as shown in FIG. 2, the logic level " 1” signal is output. 3a is an output circuit of the directional ground fault relay 3;
A fault current exceeding the set value flows and the directional ground fault relay 3
operates to output a signal of logic level "1". 32 is an AND circuit, and output circuit 3
The output signals of a and 4a are ANDed. 33 is a delay circuit, which outputs the output signal of the AND circuit for a set time.
T ₁ delay. 70 is a delay circuit, which delays the output signal of the output circuit 3a of the directional ground fault relay 3 for a set time.
T ₃ delays. Reference numeral 71 denotes a knot circuit, which inverts the output signal of the delay circuit 70. Reference numeral 72 denotes an AND circuit, which performs a logical product of the output signal of the NOT circuit 71 and the output signal of the output circuit 31a of the defect detection relay 31. 73 is a not circuit, and an AND circuit 7
Invert the output signal of 2. In this way, the NOT circuit 71, the AND circuit 72, and the NOT circuit 73 constitute an unnecessary lock prevention circuit 74. 35
is an AND circuit, which provides a trip signal to the shear breaker when the output signals of the delay circuit 33 and the NOT circuit 73 both become "1".

Next, the operation of this embodiment will be explained.

If a slight ground fault occurs at the _F2 point in Figure 5, the current differential relay 4 and the directional ground fault relay 3 operate simultaneously at the A end, as shown in Figure 8, and the output circuit 3a and the output of 4a becomes "1". The output of the delay circuit 33 becomes " ₁ " after a set time T1 from the occurrence of the accident. Further, the output of the delay circuit 70 becomes "1" after _T3 from the occurrence of the accident. That is, after _T3 after the occurrence of the accident, the output of the delay circuit 70 becomes "1", the output of the NOT circuit 71 becomes "0", the output of the AND circuit 72 also becomes "0", and the output of the NOT circuit 73 becomes "1". Therefore, the gate of the AND circuit 35 is opened and the output signal of the delay circuit 33 is awaited. Thereafter, after _T1 , the output of the delay circuit 33 becomes "1", and at this point a trip command is given to the breaker from the AND circuit 35, and the breaker is tripped.

In addition, at the B terminal, as shown in Figure 9, the directional ground fault relay 3 operates when the A terminal disconnector is tripped and a fault current exceeding the set value flows, so the output The output of the circuit 3a becomes "1" later than the output of the output circuit 4a. The output of the delay circuit 33 becomes "1" after a further set time _T1 . In addition, the output of the delay circuit 70 is connected to the directional ground fault relay 3.
From the time of operation, it becomes "1" after the set time T ₃ , and
At that time, the output of the knot circuit 71 becomes "0".
The output of the output circuit 31a is output for a set time after the occurrence of the accident.
It becomes "1" after T ₂ . Therefore, when the output of the delay circuit 33 becomes "1", the output of the AND circuit 72 is "0", the output of the NOT circuit 73 is "1", and a trip command is given from the AND circuit 35 to the disconnector. The disconnector is then tripped.

Note that the set time _T3 of the delay circuit 70 is such that the delay circuit 70
In other words, from the set time _T2 of the delay circuit 40, the operating time difference T4-3 of the current differential relay 4 and the directional ground fault relay 3 installed at the non-power supply end is subtracted so that the output of is "_1" . (T ₂ − T _4-3 ) should be set so that it is shorter than (T ₃ <T ₂ −T _4-3 ).

Therefore, according to this embodiment, even if the operation of the directional ground fault relay 3 lags behind the operation of the current differential relay, unnecessary locking due to the operation of the constant monitoring circuit 11 can be prevented, and a slight ground fault or disconnection can be prevented. It can be done reliably.

〔Effect of the invention〕

According to the present invention, as explained above, unnecessary locking by the constant monitoring circuit in the event of a slight ground fault is prevented,
It is an object of the present invention to provide a protective relay device that can reliably perform slight ground faults and disconnections.

[Brief explanation of drawings]

Figures 1, 3 and 4 are block diagrams showing a conventional FM carrier protection relay device, Figure 2 is a characteristic diagram showing the operation of the current differential relay in Figure 1, and Figures 5 and 4 are diagrams showing the configuration of a conventional FM carrier protection relay device. 6 is a circuit diagram and a time chart showing the operation of the device shown in FIG. 1, FIG. 7 is a configuration diagram showing an embodiment of the present invention, and FIGS. 8 and 9 are diagrams showing the operation of the device shown in FIG. 7. This is a time chart. 3... Directional ground fault relay, 4... Current differential relay, 1
1... Constant monitoring circuit, 32... First AND circuit, 3
3...first delay circuit, 35...second AND circuit,
70...Second delay circuit, 74...Unnecessary lock prevention circuit.

Claims (1)

[Claims] 1 A current differential relay is installed in a power system where one end is a power supply terminal and the other end is a non-power supply terminal, and which responds to the difference in current obtained at one end and the other end. A directional ground fault relay that operates, a constant monitoring circuit that monitors the current differential relay using the fact that the current difference is always zero and activates due to a failure, and a constant monitoring circuit that operates for a set time T ₂ a failure detection relay that operates on the condition that the current differential relay and the directional ground fault relay operate;
The output signal of this first AND circuit is
A slight ground fault occurred between the first delay circuit that delays by _{T 1 for} a set time shorter than T 2, the second AND circuit that inputs the output signal of the first delay circuit, and the end closest to the power supply end. When, the set time T ₃ is within a range shorter than the difference between the set time T ₂ and the operating time difference of the current differential relay and the directional ground fault relay at the non-power supply end.
a second delay circuit that delays the output signal of the directional ground fault relay, a signal obtained by inverting the output signal of this second delay circuit, and a signal obtained by inverting the logical product of the output signal of the failure detection relay; 1. A protective relay device comprising: an unnecessary lock prevention circuit provided as an input to a second AND circuit.