JPS6350938B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a protection device for a power system, and particularly to a protection device suitable for a case where a DC component included in a fault current is large.

It is well known that fault current in power systems includes a DC component, but depending on the system conditions, the amplitude of the DC component may be larger than the amplitude of the AC component, and the amplitude of the DC component may be larger than the amplitude of the AC component. There are cases where the polarity of the fault current does not reverse over a period of time (hereinafter this phenomenon is referred to as zero point shift phenomenon). When a fault current occurs due to such a phenomenon, the protective relay device can correctly detect the fault and issue a tripping command by removing the DC component with a filter. On the other hand, the shield circuit breaker can be mechanically opened in response to a trip command, but electrically the polarity of the fault current does not reverse, so the arc current continues to flow and the fault cannot be removed. Since the arc current flows over a long period of time, it may lead to contact welding or breakage of the disconnector.

In view of the above, it is an object of the present invention to provide a power system protection device that can eliminate accidents as early as possible while preventing breakage of circuit breakers.

In the present invention, focusing on the fact that the DC component included in the fault current decreases as the distance from the fault point increases, the present invention prevents the disconnector from tripping at the terminal where the zero point shift occurs, and eliminates the occurrence of the zero point shift. Disconnect the remote terminal or disconnector. To achieve this concretely, each terminal is equipped with a zero point shift detector and a means for transmitting its output between adjacent terminals. Pull out the disconnector. Furthermore, when a zero point shift is detected in the self-terminal current, the self-terminal or disconnector is actively prevented from tripping.

FIG. 1 shows a power system to which the present invention is applied, in which L is a power transmission line, CB bridge or disconnector, CT is a current transformer, and PD is a voltage transformer. RY is a protective relay device installed at each terminal.
The outputs of CT and PD and the transfer signal S from the adjacent terminal are input, and a trip command is given to the own terminal and disconnector CB. Details of RY are shown in Figure 2. In addition, in Figure 1
Symbols a, b, c, d, e, f, and g shown in RY represent input or output terminals of respective signals. Further, a separate power transmission line is connected to each terminal.

Details of the protective relay device RY shown in FIG. 2 In one embodiment, M.RY is a well-known main protective relay device;
In general high-voltage systems, a current differential system is used that provides a protective output according to the output difference between current transformers at both ends of the protection zone (for example, CT3 and CT4), or a current that similarly detects that the phase value of the current at both ends exceeds a predetermined angle. The phase comparison method is widely used. This M-RY is unique in that it does not respond to accidents in areas other than the protected area divided by CB3 and CB4, for example. The B-RY is a back-up protective relay device, and is unique in that it responds to accidents in areas other than those detected by the M-RY at its own end.In high-voltage systems, it is a distance relay system that receives current and voltage signals as input. has been widely adopted. Furthermore, in medium and low voltage systems, fault detection relays such as undervoltage relays or overcurrent relays are sometimes used.
This B-RY was installed to replace the accident removal when M-RY failed to remove it.
RY itself is capable of detecting accidents and outputting them within a short period of time, which is not much different from M・RY.
It is devised so that the final output does not occur unless it continues to operate for the time set by the timer TM. OR is an OR circuit that takes a logical sum, and in OR1, M.
When either RY or TM detects an accident and outputs "1", it outputs "1". This M・RY and B・RY
The schematic configuration of a conventionally known protective relay device is comprised of TM, OR1.

ZD is a zero point shift detection relay added according to the present invention, and gives an output "1" when the current at its own end is shifted to zero point. There are various ways to realize this detection relay, but for example, it can be realized by ensuring that the current signal does not reverse polarity for more than a predetermined period of time, or by determining the average magnitude of the current signal during one cycle. . The output of this ZD is given to output terminals a and c, and sent as a transfer signal S to the protective relay devices RY at both ends. Similarly, both ends
The operating status of RY's zero point deviation detection relay ZD is signal S.
are obtained at input terminals b and d. Also, the output of ZD is given to the inhibition circuit IN1, and when the output of OR circuit OR1 is "1" and the output of ZD is "0", IN1
As a result, the output "1" is obtained. The output of IN1 is applied to output terminal g via OR circuit OR3 and is used as a tripping signal for the circuit breaker. In other words, the first condition for tripping the breaker according to the present invention is that there is no zero point shift in the current at its own end, and the main or back-up protective relay device M.
This means that RY and B・RY are operating.
The second condition for tripping the breaker according to the present invention is determined by an AND circuit AND1 that calculates a logical product. NOT here
Since 1 is a negative circuit, the conditions for AND1 to be established are that there is an output at the own end B and RY, there is no output at the own end ZD,
This means that OR2 has an output. That is, when an accident is detected and there is no zero point shift in the current at the terminal, but a zero point shift occurs in at least one of the adjacent terminals.

Note that the reason for considering the B-RY conditions is to improve reliability against transmission noise.

The protection concept of the device of the present invention shown in FIG. 2 can be briefly described as follows.

When there is a zero point shift in the current at the end, it prevents the self-end and disconnector from tripping (since ZD outputs, the outputs of IN1 and AND1 cannot become "1").

Even if there is no zero point shift in the current at the own end, if a zero point shift is detected at the adjacent terminal, the breaker at the own end is tripped.

This idea is to protect all the terminals in the area where the zero point shift occurs, and the idea is to protect the terminals that are the limit of the zero point shift area.

In the present invention, the device shown in FIG. 2 is arranged at each terminal, and responds as follows depending on various accident situations. However, it is assumed that the accident occurred at point F, and that initially no zero point shift occurred at any terminal. At this time, since the zero point shift detection relays ZD of all terminals are inoperative, the transfer signals of all terminals are "0". Therefore, AND circuit AND1 is OR circuit OR2
It cannot be output because the output of is "0". Furthermore, since ZD is inoperative, the inhibition circuit IN1 is in a state where it can directly output the output of the OR circuit OR1, and protection is determined by the output of M.RY or B.RY. In other words,
If no zero point shift occurs, the operation of the device of the present invention is no different from that of conventionally known devices.

Next, in the event of an accident at the same location, current transformer CT2,
The operation of each protective relay device RY will be explained assuming that a zero point shift phenomenon occurs only in the output of CT3. first,
Looking at RY3, M・RY, B・RY, ZD
Both output, but since the operating time of ZD is said to be faster than that of M and RY, the inhibition circuit IN1
The output of is not "1". Also, the negative circuit NOT
Since the output of 1 is also "0", the AND circuit AND1
The output of is "0". For this reason, RY3 is prevented from tripping the disconnector even if an accident occurs within its protection zone. In RY2, B, RY and ZD operate. And for ZD to work, IN1 and AND1
The output of ``1'' is prevented from becoming ``1''. and
Looking at RY1, ZD is inactive, and B and RY are active. Therefore, the AND circuit AND1 is established if the OR circuit OR2 provides an output. In this case, since the operation output of ZD of RY2 has been transferred to OR2, it is established and the circuit breaker CB1 is tripped. In this way, RY1 has no zero point deviation at its own end, and the zero point deviation occurs at the adjacent terminal RY2, which is considered to be tripping of CB1.

On the other hand, looking at RY4, M・RY、B・
Since RY operates and ZD does not operate, inhibit circuit IN1
gives the output ``1'' of the main protective relay device M・RY to the subsequent stage and opens the breaker CB4. In this case, the transfer signal S from the adjacent protective relay device RY3
Since the content of is "1" which means the operation of the zero point deviation detection relay ZD, the AND circuit AND is established and the tripping command is given twice. lastly
Looking at RY5, RY6, and RY7, only the backup protection relay devices B and RY give an operational output, and the transfer signal from the adjacent terminal is also "0". Therefore, the AND circuit AND1 does not hold and the output of the inhibit circuit IN1 is determined by the output of the timer TM, but since the sheath breaker CB4 is tripped before the output of the timer TM, tripping at these terminals is not possible. is not executed.

Next, another embodiment of the present invention will be described with reference to FIG. The concept in Figure 2 can be said to be a distributed system in which each protective relay device can output independently depending on the zero point deviation situation between adjacent terminals, regardless of whether an accident occurs within the protected area or not. On the other hand, the one in Figure 3 detects an accident at both ends of the protection zone and transmits a signal indicating that it cannot be removed, and each end, upon receiving this signal, detects the possibility of removal at its own end. It is a so-called accident situation communication system that takes this into consideration and issues a trip command.

In this figure, the AND circuit AND1 is the same as in FIG. 2, and gives a tripping command depending on the zero point shift situation. AND2 emits a transfer signal S when there is an accident within its own protection zone and cannot be removed due to zero point shift, AND3 and AND4 transfer the transfer signal S from an adjacent terminal to another adjacent terminal. Decide whether or not to do so. Protective relay device RY in this figure
All terminals have the same configuration, and the states of input terminals d, b and output terminals g, c, and a are "0" before the accident occurs. In other words, due to the main protection relay device M/RY not working, the inhibit circuit IN1 and the AND circuit AND2
is outputting “0”, and backup protection relay device B.
Due to the non-operation of RY, the outputs of AND1, AND4, and AND5 are "0". Moreover, since the zero point deviation detection relay ZD is inoperative, the output terminal g,
The states of c and a are "0". Since the output terminals c and a of the adjacent end protection relay device RY are "0", the input terminals d and b of the own end RY
is also set to "0".

In this figure, first of all, in the case of accident F where zero point deviation does not occur, the zero point deviation detection relay ZD is inoperable, so its output is "0", and the main protection relay device M・RY
Trip is determined in the conventional manner by the cooperative operation of the backup protection relay devices B and RY. In this case, there is no forced tripping operation due to the establishment of the AND circuit AND1. In other words, in order to establish AND1 at the own end, the inputs to input terminals d and b must be "1", but this is due to the adjacent terminal protection relay device.
Since it is determined by the AND circuits AND2, AND3, AND4 of RY, it cannot be established as long as it is assumed that all terminals ZD are inoperative.

Next, let's consider what happens when the outputs of current transformers CT2 and CT3 shift to zero due to a point F accident. First, in the protective relay device RY3, the main and back-up protective relay devices M・RY, B・RY and the zero point deviation detection relay
All ZDs give output "1". At this time, the output of the inhibition circuit IN1 is "0" due to the output of ZD.
Since the output of the NOT circuit NOT1 becomes "0" due to the output of ZD, the output of the AND circuit AND1 becomes "0", and eventually the tripping of the circuit breaker CB3 is prevented. The AND circuit AND2 outputs an output by the operation of M·RY and ZD, and outputs it to the output terminal C. Then, in the protective relay device RY3 at both ends of the fault section, the negative circuit is activated by the operation of the main protective relay device M・RY.
Since the negative output from NOT2 is applied to the AND circuit AND3, the output from the output terminal a is "0". In the case of RY3, the output "1" at terminal C means "an accident has been detected within the self-protection zone, but it cannot be shut off due to zero point shift."

As is clear from the connection relationship in Figure 1, RY3
The output of terminal C of is applied to terminal d of RY2.
Looking at the situation of RY2 in this case, M.
RY not working, B/RY and ZD working. Due to this ZD operation, the output of the inhibition circuit IN1 is "0".
Furthermore, since the output of ZD is inverted by the NOT circuit NOT1 and applied to the AND circuit AND1, the output of AND1 is also "0", and as a result, opening of the circuit breaker CB2 is prevented. The transfer signal S applied to the terminal d of RY2 is input to the AND circuit AND3.
For M/RY non-operation, B/RY operation, and ZD operation
The output of AND3 becomes "1", which is output to terminal a.

The output of terminal a of RY2 is applied to terminal b of RY1. Here, RY2 is M・RY, ZD non-operating,
Since it is a B-RY operation, it is an AND circuit to which the signal "1" of terminal b is applied via the OR circuit OR2.
AND1 is output and the breaker CB1 is opened. Note that the signal at terminal b is also applied to the AND circuit AND4, but is not outputted because ZD is inactive. Also, ZD
Since AND2 and AND3 are not output due to non-operation, relaying of the transfer signal is interrupted here.

On the other hand, in the protective relay device RY4 of the other terminal that detected the accident within the protection area, M・RY, B・RY
works, but ZD does not work because zero point shift has not occurred. At this terminal, since ZD does not operate, the inhibition circuit IN1 outputs the output of the OR circuit OR1, and therefore, due to the cooperative operation of M.RY and B.RY, the circuit is disconnected.
CB4 is tripped. Note that due to the non-operation of ZD, the AND circuits AND2, AND3, AND4 do not output any output, and the transfer signal S cannot be obtained at the output terminals a and c.

Finally, regarding RY5, RY6, and RY7, since only B and RY operate, the timer TM
There is a possibility that a command to trip the breaker will be issued after a predetermined time determined by
Since CB1 and CB4 are released, B/RY returns. And RY4's own AND circuit
RY5, RY because AND2 does not hold and does not output
6. No transfer signal is sent to RY7, and therefore no tripping command is issued by the AND circuit AND1.

As described in detail above, in the embodiment shown in Fig. 3, the protective relay devices RY at both ends of the fault point send the transfer signal S to the terminals in the opposite direction of the fault, and each end uses this signal and the zero point deviation of its own end. Depending on the situation, it is decided whether to open the breaker or request that the breaker be opened at the adjacent end.

As explained in detail above, the present invention adds simple signal transmission between the zero point deviation detection relay ZD and adjacent terminals to the conventional device consisting of the main and back-up protective relay devices M・RY, B・RY. By simply providing a means, it is possible to take complete measures against the newly occurring systematic phenomenon of zero point shift. Moreover, many electrical stations in power systems have a busbar configuration and are interconnected to other power transmission lines, and the present invention can easily be extended to such other power transmission lines.

Note that since FIG. 2 shows the basic concept device of the present invention, various alternative modifications are possible especially in order to improve reliability.
It is effective to determine whether the breaker should be tripped or blocked immediately based on the operating status of the ZD, but in combination with other relay elements. Further, although the power transmission line in FIG. 1 is shown as one line for simplicity of explanation, the present invention is also applicable to cases where there are two or more lines.

[Brief explanation of the drawing]

FIG. 1, FIG. 2, and FIG. 3 are diagrams showing one embodiment of the present invention. ZD...Zero point deviation detection relay, M・RY...Main protection relay device, B・RY...Backup protection relay device.

Claims (1)

[Claims] 1. In a power system protection device that is equipped with a protective relay device at each terminal of the power system that detects a power system fault and issues a trip command to the self-terminal or disconnector,
Each protective relay device includes a zero point deviation detection relay that detects occurrence of zero point deviation in its own terminal current;
A transmission means for transmitting the output of this zero point deviation detection relay between the protective relay devices of adjacent terminals is added, and when a zero point deviation is detected in the current at the own end, the relay is tripped at the own end or the disconnector is tripped. 1. A protection device for a power system, characterized in that a current at an adjacent terminal has a zero-point deviation and a self-terminal current has no zero-point deviation, a command to trip the own-terminal current is given.