JPS6350936B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a busbar protection relay device.

One of the bus bar protection relay devices is a current differential relay system. As shown in Figure 1, this method
Connected to BUS. Current transformers CT 1 _to CT ₆ are provided on multiple lines L ₁ to L ₆ , one end of the secondary side of the current transformers CT ₁ to CT ₆ is commonly connected, and the operation of the current differential relay is connected to this common connection point. One end of the coil OC is connected to one end, and one end of each of a plurality of suppression coils RC ₁ to _{RC 6} is connected to the other end, and the other ends of the suppression coils RC ₁ to RC ₆ are connected to the secondary sides of the current transformers CT ₁ to _{CT 6} . They are connected to each other separately at the other end. As is well known, the determination formula for the system configured as described above is as follows.

ΣIi−KΣ｜Ii｜>0 However, ΣIi...Amount of movement, Σ|Ii|...Amount of suppression, K...
Suppression rate When the above judgment formula is satisfied, the relay does not operate. Here, there is a failure on track L ₂ (external accident)
occurs, and fault current I _F flows to line _L2 . Since this current I _F is a large current, the current transformer CT ₂ becomes magnetically saturated. Then, a difference current (operation amount) is generated in the apparent current differential relay, which may cause the relay to malfunction. For this reason, there is a conventional method of using a voltage differential relay system as a countermeasure against malfunctions due to saturation of current transformers. However, this method has the following drawbacks, so a current differential relay method has been adopted.

(1) All current transformer characteristics must be the same.

(2) There is a limit to the resistance value of the current transformer secondary cable.

(3) The insulation of the current transformer secondary circuit must be reinforced.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a busbar protection relay device that prevents the differential relay from operating in the event of an external accident.

An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 2, 10 is a current differential relay, and this relay 10 has the above-mentioned determination formula. 11 is a highly sensitive overcurrent relay, and this relay 11 is activated when the scalar sum current value of the lines L ₁ to _{L 6} shown in FIG. 1 exceeds a certain value. That is, the overcurrent relay 11 detects the rise of the suppression amount, and supplies the detected output to the timer circuit 12 to start the timer circuit 12. The operating output of the current differential relay 10 is applied to this timer circuit 12 . When this operational output is given to the timer circuit 12, the timer circuit 12 is reset. However, there are two conditions for this reset: The first is 1 from the rise of the suppression amount detected by the overcurrent relay 11.
When the operation output is given to the timer circuit 12 after more than one cycle has elapsed, the timer circuit 12 is not reset and continues to send out the timer output, and when the operation output disappears, the timer circuit 12 is reset. Second, when the operational output is given to the timer circuit 12 within one cycle from the rise of the suppression amount, the timer circuit 12 is reset. The operating output of the current differential relay 10 is applied to a first input of an inhibit circuit 13, and the output of the timer circuit 12 is applied to a second input of the inhibit circuit 13. This inhibit circuit 13 has an input at its first input terminal, and sends a trip command to its output terminal when there is no input at its second input terminal.

In the embodiment configured as described above, first, the saturation of the current transformer will be described. Saturation of the current transformer gradually occurs because the terminal voltage of the current transformer increases as the primary current increases. occurs in Therefore, saturation of the current transformer in the event of an external fault occurs one to several cycles after the rise of the current at the time of the fault. That is, it is known that the operating amount rises approximately one cycle later than the suppressing amount. On the other hand, it is also known that in the event of an internal accident, the amount of operation and the amount of suppression rise simultaneously.

The operation of the embodiment will be described below using the above-mentioned reasons. In the event of an external fault, a current flows through the operating coil OC of the current differential relay 10 as shown in FIG. 3A, and a current as shown in FIG. 3B flows through the suppression coil OC. On the other hand, since the overcurrent relay 11 detects the rise of the suppression amount as described above, its output appears at the time shown in FIG. 3D.
When this output is given to the timer circuit 12, the timer circuit 11 is started, and an output waveform as shown in FIG. 3E appears at its output terminal. Since the operating output of the current differential relay 10 appears with a delay of one cycle from the amount of inhibition as shown in FIG. given to. The operating output of the relay 10 is applied to the first input terminal of the inhibit circuit 13, but no trip command is sent to the output of the circuit 13. (Fig. 3F) Therefore, no malfunction occurs when an external accident occurs.

On the other hand, in the event of an internal fault (when there is a fault on the bus shown in FIG. 1), currents as shown in FIGS. 4A and 4B flow through the operation and suppression coils of the current differential relay 10. On the other hand, the output of overcurrent relay 11 appears at the time shown in FIG. 4D, and timer circuit 12 is started. Also, since the operating output of the current differential relay 10 appears within one cycle from the amount of suppression, ie, as shown in FIG. 4C, the timer circuit 12 is reset and its output disappears as shown in FIG. 4E. Therefore, a trip command is sent to the output of the inhibit circuit 13. (Fig. 4F) Fig. 5 shows another embodiment of the present invention, in which a current transformer
The outputs of CT ₁ to _{CT 6} are input to the current/voltage converter I/V. Each output of these current/voltage converters I/V is input to a multiplexer MPX via a sampling hold circuit S/H. The output of this multiplexer MPX is input to the central processing unit CPU via the analog-to-digital converter A/D.
The central processing unit CPU processes the input signals to prevent the trip command from being sent out in the case of an external accident, and to send out the trip command in the case of an internal accident, as in the previous embodiment. In addition, in the figure, BUS is a bus bar, and L ₁ to L ₆ are lines.

As described above, according to the present invention, a current differential relay to which the output of the current transformer is input and an overcurrent relay that detects the rise of the suppression amount are provided, and the current difference When the operating output of the dynamic relay occurs, the output of the timer circuit is held, and when it is within one cycle, the timer circuit is reset, and when the former output is held, the trip command is not sent, but when the latter is reset, the trip command is sent. This prevents the current transformer from malfunctioning even if it becomes saturated due to a large current caused by an external fault.In addition, in the event of an internal fault, it is reliably detected and the bus bar can be protected, and the advantages of the current differential relay system can be utilized. This has the advantage of being able to take measures against current transformer saturation without causing damage.

[Brief explanation of drawings]

Figure 1 is a circuit diagram of the current differential relay system, Figure 2 is a block diagram showing an embodiment of the present invention, and Figure 3A.
3F and 4A to 4F are waveform diagrams for explaining the operation of FIG. 2, and FIG. 5 is a block diagram showing another embodiment of the present invention. L ₁ to L ₆ ...Line, BUS...Bus bar, from CT ₁
CT ₆ ...Current transformer, 10...Current differential relay, 11
...Overcurrent relay, 12...Timer circuit, 13
...Inhibit circuit (output circuit).

Claims (1)

[Claims] 1 A current transformer installed separately on multiple lines, a current differential relay into which the output of these current transformers is input, an overcurrent relay that detects the rise of the suppression amount, and an overcurrent relay that is activated by the output of this overcurrent relay. is started, and when the current differential relay sends an operating output with a delay of several cycles or more after the rise of the suppression amount, the output is held, and when the operating output is within a few cycles, the output is reset. When the output and the output of the current differential relay are input, and the holding output is being sent out from the timer circuit, the trip command is not sent out, and when the timer circuit is not sending out the output, the output circuit is configured to send out the trip command. A busbar protection relay device equipped with