JPH0444491B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention is applicable to 112 electrical stations such as power plants and substations.
The present invention relates to a carrier-type current differential relay device applied to the protection of power transmission lines connected to a breaker bus.

[Technical background of the invention]

In general, a 112-line breaker bus is a circuit connected in series between a double bus bar consisting of a bus 1A and a bus 2A by three breaker switches 6A, 7A, and 8A, as shown in Figure 1. This is a busbar system in which the transmission line 3 is connected between the disconnectors 6A and 7A, and the transformer 9A is connected between the disconnectors 7A and 8A. If it is desired to further increase the number of lines, a bus system is used which can be constructed by increasing the number of circuits in parallel to the series-connected circuits.

In addition, in this type of bus system, when a failure occurs in the power transmission line 3, line protection current transformers 4A and 5A
The transmission line protection relay device LP1 is operated by the differential current based on the output current of the current transformers 4B and 5 connected to the buses 1B and 2B at the other end
Transmission line protection relay device LP2 operates via B,
The fault is removed by tripping the shield breakers 6A, 7A and 6B, 7B.

[Problems with background technology]

In the transmission line protection relay device with the system configuration shown in Figure 1, when a fault F occurs on the bus 2A, the current transformer 4
An excessive passing current IF flows in A and 5A, and a difference current occurs in the sum circuit of the secondary current transformers of 4A and 5A due to CT saturation, etc., as if an internal failure had occurred in the transmission line 3 in the protection zone. This causes the transmission line protection relay device to operate unnecessarily, causing problems such as erroneous or disconnected healthy circuits.

[Purpose of the invention]

The present invention has been made to solve the above problems, and uses the vector sum current of the two current transformer secondary circuits of the 112-wire disconnector bus as the input current to the current differential relay device. The purpose of the present invention is to provide a carrier-type current differential relay device that, when introduced, will not malfunction due to differential currents caused by errors caused by current transformer saturation due to excessive passing current during bus bar failure.

[Summary of the invention]

In the present invention, each differential current from the own end and the opposite end is introduced to determine internal and external failures according to variable ratio differential characteristics, and the results of this determination are mutually transmitted via a transmission line. A current differential relay device is provided at each electrical station to determine whether the relay is disconnected or disconnected based on the logical product of the determination result and the determination result from the other end.

[Embodiments of the invention]

Examples will be described below with reference to the drawings.

First, the concept of an FM current differential relay device will be explained as an example of a current differential relay device. In other words, it is an FM current differential type power transmission line protection device that uses FM waves as a carrier wave (hereinafter abbreviated as FM relay).
modulates the amount of electricity input at each terminal of the transmission line into FM waves, transmits and receives it at each terminal via the transmission line, and calculates the difference between the amount of electricity input at one end and the amount of electricity transmitted from the other end. This principle protects power transmission lines.

FIG. 2 is a configuration diagram of an embodiment of the carrier type current differential relay device according to the present invention. In this diagram, bus line 1
The A and 2A sides represent the A electric station, and the bus 1B and 2B sides represent the B electric station, and the symbols A and B of each device correspond to the devices installed at that electric station.

In Fig. 2, 10A and 10B are current/voltage converters that convert current to voltage, and 11A and 11B are converters that convert the voltage obtained by combining the outputs of the secondary current/voltage converters of each current transformer into frequency using a sum circuit. 13A, 13B are communication devices, 15A, 15B
is a demodulator that demodulates a carrier signal into a voltage signal, 1
9A, 19B are current transformers 4A, 5A and 4, respectively.
Transmission delay compensation device provided corresponding to B, 5B, 2
0A and 20B are determination circuits, and the determination circuit 20B at the B terminal performs a differential operation using the self-end signal V _B output from the transmission delay compensator 19B and the output V _A of the demodulator 15B as inputs.

In other words, the judgment circuits 20A and 20B are judgment circuits for FM relays with variable ratio differential characteristics as shown in Fig. 3, and their inputs are the secondary currents/
Input the output electrical quantity of the voltage converter given through the transmission delay compensator and the output electrical quantity of the secondary current/voltage converter of the current transformer at the other terminal given via the transmission line 14 and the demodulator. are doing. And 21A and 21B are AND circuits, which respectively input the FM relay output which is the output of the determination circuit at the own end and the FM relay output at the opposite end.

Here, an example of the current differential characteristics of the FM relay shown in FIG. 3 will be described. Generally, variable ratio differential characteristics are used for the differential characteristics of FM relays. In FIG. 3, the horizontal axis represents the passing current IF, and the vertical axis represents the differential current Id. While a comparison of normal ratio differential relays takes a constant value in a large current range, in a relay with variable ratio differential characteristics, the ratio increases significantly in a region where a large passing current flows. Generally, when performing high-speed protection, relays tend to malfunction due to transient current transformer errors caused by the DC component of the fault current that flows in the event of an external fault, but relays with variable ratio differential characteristics can easily operate even in such cases. It is designed to be difficult to malfunction.

Here, the determination circuit 20A is the transmission delay compensation circuit 1
2 of current transformers 4A and 5A input via 9A
Assuming that the secondary currents are IA1 and IA2, and the secondary currents of current transformers 4B and 5B at the other terminals input via the communication device are IB1 and IB2, the judgment circuit 20A
As is clear from FIG. 3, the operation determination formula is as follows. (The same applies to the judgment circuit 20B) Id>K1ΣIA+K0 (small current range) Id>K2ΣIA+K0 (large current range) Here, K0, K1, K2 (>K1) are constants ΣIA=|IA1|+IA2|+|IB1+IB2| Id= |(IA1+IA2)+(IB1+B2)| The response of the determination circuit having the above configuration will be explained using an example of an external failure, which has been a problem in the past.

For example, under the worst case scenario where the inflow current from the other station is zero due to external fault F on bus 2A of electric station A, the difference current (|
Consider a case where IA1+IA2｜>0) occurs.
In this case, the secondary currents of current transformers 4A and 5A are input to the judgment circuit 20A via the transmission delay compensation circuit 19A, so the output of the judgment circuit 20A of the FM relay at electric station A is the passing current (ΣIA ) is large, it becomes point "A" in the variable ratio characteristic diagram of FIG. 3 and is not output. Further, this no-output condition is inputted to the communication device 13A via the modulation device 11A, and the output of this communication device 13A is transmitted via the transmission line 14 to the communication device 13B of the opposite terminal B electric station.

Next, we will explain the response of the FM relay at electric station B. When an external fault F occurs in the bus 2A of electric station A, and a difference current occurs between the secondary currents of current transformers 4A and 5A, the voltage/frequency converter 11A
The differential current is received at the B electric station. At this time, B
If the secondary currents of the current transformers 4B and 5B of the electric station are smaller than the passing current of the electric station A, this corresponds to point "B" of the variable ratio characteristic in FIG. 3, and is output. However, since the trip output of the B electric station is based on the condition of the AND circuit 21B, which is the FM relay output from the A electric station, the output of the AND circuit 21B is ``None.'' Therefore, it is determined that it is an external failure, and it is possible to prevent the FM relay device from being erroneously or disconnected due to the differential current generated in the current transformer secondary due to the excessive passing current when the A bus breaks.

Next, the response when an internal failure occurs in the power transmission line 3 will be explained. When there is an internal failure in the transmission line 3, the difference current between the passing current due to the secondary current of each current transformer at electric stations A and B is sufficiently large, so that the current will be around point "C" in the variable ratio characteristic diagram in Fig. 3. Therefore, the outputs of the judgment circuits 20A and 20B of the FM relays at each electric station will be "Yes", and these outputs will be used as inputs.
The outputs of the AND circuits 21A and 21B also become "present", and the FM relay device reliably outputs a trip command to the breaker.

The above explanation deals with the case of an external failure at electric station A, but even if a difference current occurs in the case of an external failure at electric station B, the same operation will occur, and the FM relay device will not issue a trip command by mistake. do not have.

In addition, when there is an external fault on the bus 2A of electric station A in Figure 2, there is also a fault current from electric station B, but the magnitude of the inflow current from electric station B and the outflow current from electric station A are equal. The phases are assumed to differ by 180°, and the difference current Id generated between electric stations A and B is assumed to be zero, so it is not particularly taken into account in the present invention.

Next, as a modified application example, it is obvious that the present invention can also be applied to other current differential relay devices such as a PCM current differential relay device that uses a differential system by modulating an analog electrical quantity into a pulse code.

〔Effect of the invention〕

As explained above, according to the present invention, the internal failure judgment conditions of both terminals are transmitted to each other and
Since the AND configuration is adopted, it is possible to provide a carrier-type current-operated relay device that does not malfunction even due to a difference current caused by a current transformer error current due to an excessive passing current when an external failure occurs in a 112-wire disconnection line configuration.

[Brief explanation of drawings]

Figure 1 is a system overview diagram of the 112-year-old disconnection bus.
FIG. 2 is a configuration diagram of an embodiment of the carrier-type current differential relay device according to the present invention, and FIG. 3 is a characteristic diagram of the variable ratio operating relay. 1A, 1B, 2A, 2B... Bus bar, 3... Transmission line, 4A, 4B, 5A, 5B... Current transformer, 6A,
6B, 7A, 7B, 8A, 8B... Shiya disconnector, 9
A, 9B...Transformer, LP1, LP2...Protective relay device, 10A, 10B...Current/voltage converter, 1
1A, 11B...Current/frequency modulator, 12A...
...Transmitter, 13A, 13B...Communication device, 14...
...Transmission line, 15A, 15B, 17B...Frequency/
Voltage demodulator, 16B, 18B...Lock circuit, 1
9A, 19B...Transmission delay circuit, 20A, 20B
...Judgment circuit, 21B...AND circuit.

Claims (1)

[Claims] 1 Each electric station has a 112-wire disconnect bus configuration, with current transformers installed on both sides of the connection point between the bus and the transmission line, and current information from each current transformer is mutually transmitted. In a carrier-type current differential relay device that protects power transmission lines, each electric current from the own end and the other end is introduced into each electrical station, and the passing current of the current transformer at the own end and the other end is A determination circuit that determines internal and external failures according to variable ratio differential characteristics determined by the difference between the differential current of the current transformer and the differential current of the current transformer at the other end; mutually transmitted via
1. A carrier-type current differential relay device comprising an AND circuit that determines whether or not a circuit breaker is to be tripped when a determination result from the own end and a determination result from the opposite end are both established.