JPS63114525A - Current differential relay - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Object of the invention] (Industrial application field) The present invention transmits the current waveform of one end to the other end using PCH transmission means or FM transmission means, and This invention relates to a current differential relay device that detects the difference in current between the two and distinguishes between internal and external faults in the system.

(Prior Art) FIG. 2 is a configuration diagram of a two-terminal system of a current differential relay device. In the figure, 1 is the power transmission line, 2B is the current transformer, 3
A, 3B are voltage transformers, 4A, 4B are current waveform transmitting circuits, 5^, 5B are current waveform receiving circuits, 6 is PCH transmission line or FH transmission line, 7A, 7B are current differential relay operation determination circuits, 7A (T), 7B(T) is the output of the judgment circuit, 8
A and 8B are circuit breakers, and RY (A) and RY (B) are current differential relays. Subscripts A and B indicate the A terminal and B terminal.

Hereinafter, the response will be explained using the A terminal as an example.

Current and voltage information on the power transmission line 1 is taken into the current differential relay RY(A) via the current transformer 2^ and the voltage transformer 3A. The current waveforms of each phase taken into the current differential relay RY (8) via the current transformer 2^ are introduced into the operation determination circuit 78, and are also sent to the PCM transmission line or F) by the current waveform transmission circuit 4A. It is transmitted to the other end (8 terminals) via the l transmission line 6.

The current waveform of each phase at the other end (B terminal) is introduced into the current waveform receiving circuit 5A of the current differential relay RY (A) via the PCM transmission line or FH transmission line 6, and then the operation judgment circuit 7
introduced into A. The operation determination circuit 7A processes the input data according to a predetermined determination algorithm, controls the operation determination output cuff Am, and controls the "open command" to the breaker 8.

Here, the configuration of an operation determination circuit in a conventional current differential relay device will be explained with reference to FIGS. 3 and 4.

FIG. 3 shows the configuration of the most basic operation determination circuit. In the figure, 7A-1 indicates a differential current detection circuit for each phase (or between lines). Current input for each phase at its own end (2A-IN) from the current transformer 2A and current input for each phase at the other end (5^-IN) from the current waveform receiving circuit 5A is the difference current between each phase (or between lines). It is introduced into the detection circuit 7^-1, and with the output of 7A-1, it is directly sent to the judgment output cuff A of the operation judgment circuit 7A.
(T). This method has a simple configuration, but since it consists of only a current input, the input circuit (CT
If a defect occurs in the circuit), malfunction may occur. The defect here refers to a case where normal input information is not transmitted to the relay due to a mode such as disconnection or short circuit.

FIG. 4 shows the configuration of an operation determination circuit that improves the drawbacks of FIG. 3. In the figure, IA-2 indicates an undervoltage detection circuit, and 7A-3 indicates an AND circuit.

The differential current detection circuit 7A-1 for each phase (or between lines) is the same as that shown in FIG. 3. A voltage input (3A-IN) from the voltage transformer 3A is introduced into an undervoltage detection circuit 18-2, which detects a voltage drop in the event of a fault in the protection system.

The output of the differential current detection circuit 7A-1 and the output of the undervoltage detection circuit 7A-2 are connected to the AND circuit 7A-
In this method, the output of the AND circuit is used as the judgment output cuff A(T) of the operation judgment circuit.

In this method, when considering the failure of the input circuit (CT circuit) described in Fig. 3, one of the inputs of the AND circuit 7A-3 has the same configuration as in Fig. 3, so the condition is satisfied. but,
The other condition is not satisfied because the input circuit (PT circuit) is healthy.

(Problem to be solved by the invention) In the case of the method shown in FIG. 4 described above, the AND of multiple input conditions
Therefore, a single fault will not cause a malfunction, but depending on the nature of the system fault, there may be a mode in which the system malfunctions.

This example will be explained using the three-terminal system diagram shown in FIG. In the figure, the A end and the B end have a power supply behind them, so-called power supply ends, and the C? It is assumed that Ia is a load end (non-power end) that does not have a power source behind it, and is branched at a location near end A. In such a configuration, it is assumed that a system fault occurs at point F near end B, as shown in the figure. Since the fault current flows into the fault point from the A terminal and B terminal of the power supply terminal, the difference current detection circuit 7A-1, 7B-1 (7C
-1) can detect accidents. The problem is the undervoltage detection circuit 7A-2, 7B-2 (7C-2)
It is.

At the B end, since it is a near end accident, a sufficient voltage drop can be expected and operation is possible. At the A terminal, the fault is far away and a sufficient voltage drop may not be expected, but the fault current flows sufficiently, so for example, the undervoltage detection circuit 7A-2 in Fig. 4 can be replaced with an undervoltage detection circuit with current compensation. This is a detection circuit whose undervoltage characteristics automatically change depending on the magnitude of the current, and can be operated using a commonly used detection circuit.

Now let's consider the C end. Since the C terminal is branched close to the A terminal, the voltage drop is not sufficient like the A terminal. or,
Since there is no power supply behind it, the fault current is almost zero, and the effect of the current compensation described above cannot be expected.

Therefore, in the configuration of the operation determination circuit as shown in FIG. 4, when an internal fault occurs, the undervoltage detection circuit 7A-2 cannot detect a system fault, resulting in a malfunction as a protection device.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a current differential relay device that operates reliably in the event of an internal accident and has high reliability.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention differentially connects each phase current at its own end and each phase current transmitted from the opposite end, and The signal is transmitted from the other end to a first circuit that detects the phase difference current level and a second circuit that detects a voltage drop in the event of an accident using an undervoltage detection circuit with current compensation installed at the other end. A third circuit for detecting an overcurrent level from each phase current is provided, and the second and third circuits are connected to the output of the first circuit.
The logical sum output from each circuit is used as the other output to derive the logical product output.

(Function) Therefore, even if the undervoltage detection circuit at terminal C is inoperative due to a fault at point F in FIG. 5, it is possible to detect an internal fault by the current flowing through the overcurrent detection circuit from each terminal.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a configuration diagram of an embodiment of a current differential relay operation determination circuit according to the present invention.

7A-1, 7^-2, and 7A-3 are the circuits already explained in the conventional system, and detailed explanation will be omitted. IA-4
is an overcurrent detection circuit for each phase (or between lines), which outputs an overcurrent when any one of the phases detects an overcurrent. 7
A-5 indicates an OR circuit, and 7A-4 and 7A-5 are newly added circuits according to the present invention. The current input for each phase at the other end (5A-IN) is introduced into each phase (or line-to-line) overcurrent detection circuit 7^-4, and its output is connected to the output of the undervoltage detection circuit with current compensation 7A-2 and the OR circuit 7A. -5, and furthermore, the output of the OR circuit is introduced into each phase or line) difference current detection circuit 7A-1 and AND circuit 7A-3, and this AN
The output of the D circuit was configured to be used as the determination cuff A(T) of the current differential relay operation determination circuit.

The effect in each case will be explained below.

■When a self-end CT circuit failure occurs, in this case, each phase (or line-to-line) difference current detection circuit γA-1 may malfunction, but the undervoltage detection circuit 7A-2
and the other end each phase (or line-to-line) overcurrent detection circuit 7A-4,
Since none of them operate, the operation determination circuit 7A does not malfunction.

■When a defect occurs in the CT circuit at the other end, in this case, each phase (or between lines) difference current detection circuit 7A-1 and each phase (or between lines) overcurrent detection circuit 7A-4 at the other end,
Both of them may malfunction, and the operation judgment ratio cuff ^
(T) may occur.

However, this operation judgment ratio cuff A(T) is an accident detection element (not shown) (usually an element that responds to a single current and voltage element at its own end and always operates when a system fault occurs. , is an OR condition of an undervoltage detection element, a voltage change detection element, an overcurrent detection element, a current change detection element, etc.
The change detection element is configured to hold the output for a certain period of time during operation so that protection can be reliably performed.A14D constitutes the trip output. Opposite end C
When the T circuit is defective, the fault detection element at its own end does not operate, so the protective device will not malfunction.

■ Regarding the influence of the system configuration, assuming an accident with the system configuration shown in Figure 5,
Let us consider the C-terminal response, which was a problem in the conventional operation determination method shown in the figure, using the operation determination circuit of the present invention shown in FIG.

Note that the diagram will be explained using the symbol for the A terminal. As mentioned above, in this case, the undervoltage detection circuit 7 with current compensation
The operation of A-2 cannot be expected.

However, each phase (or line-to-line) overcurrent detection circuit 7A-4 based on the current at the other end is provided under an OR condition with 7A-2. Considering end A and end B, which are opposite ends to end C,
The fault current is flowing sufficiently, and each phase of the other end at the C terminal (
(or line-to-line) overcurrent detection circuit 7A-4 is activated.

Therefore, the condition of the AND circuit 7A-3 with the output of the operating phase (or line-to-line) difference current detection circuit 7A-1 is established, and the operation determination ratio cuff A(T) is generated.

Furthermore, regarding the aforementioned accident detection element (not shown) that is inserted into this judgment output by AND, the undervoltage detection element cannot operate, but the voltage change detection element detects the instantaneous voltage change at the time of an accident and operates. As a result, an operational output as a protection device is generated.

In other words, even if the conventional system malfunctions, the present invention allows normal operation.

Here, some additional information will be given regarding the other end overcurrent detection circuit 7A-4. In the case of a two-terminal system, there is one mating end, but in the case of a multi-terminal system with three or more terminals, there are multiple mating ends. In this case, the overcurrent detection circuit 7A-4 is installed for each mating terminal, and the OR condition of these outputs is used. In the current differential method, it is a prerequisite that a large power supply exists at least at one end, and such an OR configuration enables reliable operation at the non-Nm end. In addition, the detection level is set to be higher than the normal system passing current,
Prevents malfunction due to CT failure during heavy current.

In the above description, the overcurrent detection circuit 7A-4 is based on phase current or line current, but it may also be based on negative phase current derived from phase current.

In the case of Fig. 2 described above, the overcurrent level is detected at the receiving end from the transmitted phase currents at the other end, but the overcurrent level detection circuit is provided on the transmitting end,
Of course, the object of the present invention can also be achieved by transmitting the result to the other end.

[Effects of the Invention] As explained above, according to the present invention, the overcurrent condition of each phase (or between lines) at the other end can be set as a fail-safe condition for each phase (or between lines) differential current trip circuit at the own end. Because it is implemented as an AND, it is not affected by single defects in the CT circuit, but it is also not affected by the system configuration.In particular, the PCH current difference between the digital relay and the relay judgment circuit configured with software is not affected by the system configuration. In the dynamic relay device, the hardware configuration may be the same as the conventional one, and it is possible to provide a current differential relay device with great cost advantages.

[Brief explanation of the drawing]

FIG. 1 is a current differential relay operation determination circuit according to an embodiment of the present invention, FIG. 2 is a two-terminal configuration diagram of a current differential relay device, and FIG. 3 is a conventional current differential relay operation determination circuit. FIG. 4 is a diagram showing still another example of the current differential relay operation determination circuit of the prior art, and FIG. 5 is a three-terminal system diagram for explaining the problems of the prior art. 1... Power transmission line 2A, 2B... Current transformer 3A, 3B... Voltage transformer 4^, 4B... Current waveform transmitting circuit 5A, 5B... Current waveform receiving circuit 6... PCH Transmission line or FM transmission line 7A, 7B...Current differential relay°-operation determination circuit 7A
-1...Difference current detection circuit 7A-2...Undervoltage detection circuit 7A-3...AND circuit 7A-4...Overcurrent detection circuit 7A-5...OR circuit 7A(T), 7B(T)... Output 8A of judgment circuit 7B, 8B... Breaker

Claims (2)

[Claims] (1) Equipped with means for transmitting the current waveform of one end to the other end,
A first circuit that differentially connects each phase current at its own end and each phase current transmitted from the other end to detect the difference current level of each phase, and an undervoltage detection with current compensation provided at its own end. In a current differential relay device that uses each output to determine an internal fault, the overcurrent level is detected from each phase current transmitted from the other end. A third circuit is provided, and an AND output is derived from the output of the first circuit by using the OR output from each of the second and third circuits as the other output. Current differential relay device. (2) The overcurrent level is detected on the transmitting side and the result is transmitted to the other end, thereby making it a condition for the second circuit on the receiving side. Current differential relay device.