JP2729496B2 - Power circuit breaker protection method - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a protection method for a power circuit breaker, and more particularly, to prevention of failure of interruption due to multiple lightning.

(Prior art and its problems) When a ground fault occurs due to a lightning strike, the fault line is temporarily cut off at both ends to recover from the fault with no voltage, and then the breaker is turned on again to continue power transmission. Immediately after the interruption of the ground fault current generated by the first lightning strike on the line, that is, during the period in which the dielectric strength between the circuit breakers is reduced (multiple lightning), there is a lightning strike again, and the abnormal voltage due to the lightning surge repeatedly enters. When proceeding toward the circuit breaker, the gap between the circuit breakers may flash, and the circuit may be re-ignited or re-ignited so that the circuit cannot be interrupted and the circuit breaker may be destroyed. In order to prevent this, for example, as shown in FIG. 1, the abnormal voltage intrusion side of the circuit breaker (1), that is, between the line (2) side and the ground (3) is connected via the normally open circuit closing device (4). The circuit breaker (1) is connected by a conductor (5) having a very small resistance value, and after the line (2) is cut off by the circuit breaker (1) working based on the first lightning strike.
In conjunction with this, the closing device (4) is closed and the line (2) is grounded by the conductor (5). Thus, a method has been proposed in which an abnormal voltage is bypassed from the circuit breaker (1) to reduce the voltage value to prevent interruption or destruction.

However, this method cannot provide protection from immediately after the interruption of the fault current to grounding, particularly during the period when the dielectric strength most required is reduced. In order to make this possible, when the grounding is performed during the current interruption period by the circuit breaker, a large current corresponding to the fault current is generated by the input device (4).
To the grounding conductor (5). Therefore, since a large current carrying performance is required for the grounding device, there is a problem that the grounding device becomes large and expensive, and it is difficult to implement.

(Object of the Invention) The present invention reduces the abnormal voltage due to the multiple lightning that enters during the period from the current interruption to the re-input due to the recovery from the failure due to the interruption, and can protect the circuit breaker from interflash. In providing the formula.

(Means of the Present Invention for Solving the Problems) The features of the present invention are as follows. That is, a non-linear resistor having a voltage and current characteristic as shown by a curve (a) in FIG. 4 is connected to the entry side of the abnormal voltage via a closing device in place of the conventional conductor having a very small resistance value. The operating voltage level of the resistor is selected to be a voltage value on the abnormal voltage entry side, that is, a value slightly larger than the sum of the fault point voltage and the line voltage drop to the circuit breaker. Then, the breaker is turned on and grounded in synchronization with the breaking operation of the breaker so that the current flowing through the ground circuit is kept at a small value, and the breaker is switched over the entire area from the current cutoff to the re-closing. It is something that can be protected. Next, the present invention will be described in detail with reference to the drawings.

(Embodiment) FIG. 2 is a diagram showing an embodiment of the present invention (the same reference numerals as in FIG. 1 indicate the same parts). In the figure, (6) is a power transformer, (7) is a lightning arrester for transformer protection, (1) is a power circuit breaker, (2) is a line, (8) is a lightning arrester for a line entrance,
Reference numeral (4) denotes a closing device, which is configured to operate in conjunction with the shutoff operation of the power circuit breaker (1). (9)
It is a non-linear resistor, the fourth view of (a) such voltage curve has a current characteristic, the operating voltage level V _L to the fourth
Slightly greater than the line voltage V _F at the time of a failure shown by (b) curve of FIG, it is selected lower than the protection voltage level V _A of FIG. 4 (c), line shown in curve service entrance for arrester (8).
Next, the protection operation will be described with reference to FIGS.

During normal operation, the line voltage is the time shown in FIG.
It is maintained at a predetermined voltage V as before t ₀ , and the circuit breaker (1)
The load current I flows as shown in FIG. 3 (b). At this time, the circuit breaker (1) is in a closed state, and the closing device (4) is in an open state.

Fault current I _F as next Figure 3 by a ground fault, as in the second view (10) is generated at time t ₀ to the line (2) (b)
Flows, the protection relay (not shown) detects this and sends an opening command to the circuit breaker (1), and the time t _{1 in} FIG. 3 (c).
The opening is started at. Then perform interruption of fault current I _F as Figure 3 completely by opening at time t ₃ (b).

On the other hand, a closing command is sent to the closing device (4) in synchronization with the start of opening of the circuit breaker (1).
Non-linear resistor at a time t ₂ (9) of the line (2) and is connected between ground (3), the operating voltage level V _L is the 4 (a in this case non-linear resistor (9) ) as a curve, is set a little Uwamawaru so than the voltage V _F of the sum of the voltage drop of the fault point voltage and the line. Thus the time t ₄ from the non-linear resistor at a time t ₂ of FIG. 3 (9) is connected to the line (2)
, A re-closing command signal is applied to the circuit breaker (1), the closing device (4) is opened just before closing of the circuit breaker (1), and the nonlinear resistor (9) is disconnected from the line (2). During this time, the abnormal voltage that has traveled along the line toward the circuit breaker (1), that is, the abnormal voltage having a level higher than the operating voltage level _VL , is absorbed by the non-linear resistor (9). Therefore, the circuit breaker can be protected including the period in which the dielectric strength has been reduced immediately after the opening.

In contrast the third view of time t _2, the at the time when the charged was made non-linear resistor according to the dosing device (4) (9), circuit breaker (1) at time t ₃ not completed the opening Complete the shutdown. Therefore from time t ₂ to t ₃ nonlinear resistor (9)
Although the voltage V _F of the sum of the fault point voltage and the line voltage drop is applied to the, this voltage is below the operating voltage level V _L of the nonlinear resistor (9) as the non-linear resistor (9) Has a high resistance value. Therefore, since a large current does not flow through the non-linear resistor (9), the input device (4) and the non-linear resistor (9)
, The current carrying capacity can be remarkably reduced, and miniaturization and cost reduction can be achieved.

(Effects of the Invention) As is clear from the above, according to the present invention, the protection level is lower than that of the lightning arrester for the line entrance through the non-linear resistor during the period from interruption by the circuit breaker to retransmission of power by re-input. By coordinating with the dielectric strength inside the circuit breaker, which has decreased immediately after the current interruption, it is possible to prevent re-ignition or re-ignition of the circuit breaker due to intrusion of an abnormal voltage or failure of interruption. Therefore, it is possible to prevent the breaker from being damaged by multiple lightning strikes, and to contribute to the stable supply of electric power.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a conventional system, FIGS. 2 and 3 are diagrams of an embodiment of the present invention and waveform diagrams for explaining the operation thereof, and FIG. 4 is a voltage of a non-linear resistor used in the present invention. FIG. (1) Circuit breaker, (2) Transmission line, (3) Ground, (4) Loading device, (5) Conductor with extremely low resistance, (6) Power Transformer, (8) Lightning arrester for track entrance, (9) Non-linear resistor.

Claims (1)

(57) [Claims] An operating voltage characteristic is higher than a combined voltage of a line voltage drop and a fault point voltage at the time of a line fault through an input device between an abnormal voltage intrusion side line of the circuit breaker to be protected and the ground, In addition, a non-linear resistor having a characteristic lower than the protection voltage level of the lightning arrester for the line entrance at the time of normal operation is connected, and the abnormal voltage intrusion occurs from the start of the fault current interruption operation by the circuit breaker until the circuit is turned on again. A power circuit breaker protection system in which a side line is grounded via the non-linear resistor to prevent re-arcing or re-ignition of the circuit breaker.