JPS6226522B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a protection device, and more particularly to a protection device for a shield breaker against fault current failure of a power transmission line in a large-capacity power plant.

In general, fault currents in power transmission lines near power plants follow an extremely asymmetrical course with respect to the zero line of the current waveform, so it is possible that the zero-point crossing does not occur over many cycles of the current waveform. . Initially, fault currents, such as short-circuit currents, were considered only for generator protection and disconnectors on the low-voltage side. However, as high-quality main transformers have been installed for large-capacity generators, such as 500MVA class or higher, the ratio of the generator's negative phase reactance to the armature resistance has increased. Since the ratio of reactance to resistance of the short-circuit current path has become extremely small, consideration must be given to short-circuit currents that do not cause a current zero point over many cycles on the high-voltage side of the transformer. It's gone.

When such short-circuit current is interrupted by a conventional circuit breaker, such as a puffer-type gas circuit breaker, a two-pressure gas circuit breaker, or an air circuit breaker, the short circuit current is caused by the spraying time of the arc-extinguishing medium. In products where the time during which the short circuit current can be interrupted due to restrictions is limited,
Either the arc voltage must be raised above the circuit voltage very quickly, or the blowing time must be increased significantly. Therefore, this becomes a problem in the structural design of the arc extinguishing chamber of the arc breaker, and is not an effective means, but a problem that should be solved.

SUMMARY OF THE INVENTION An object of the present invention has been made in view of the above points, and it is an object of the present invention to provide a protection device that can quickly cut off a fault current without a current zero point.

In order to achieve the purpose of the present invention, a high frequency oscillating circuit and a resistor are provided in parallel with the breaker, and even in the case of a fault current where there is no current zero point, a high frequency oscillating current is forced to flow through the breaker to create a zero point. It is characterized by its ability to quickly cut off fault current.

The present invention will be described below with reference to embodiments shown in FIGS. 1 and 2. As shown in Fig. 1, a capacitor 1
2 and a transformer 13 having a high frequency power source 14, and a surge suppression resistor 1 that occurs when the current is interrupted.
5 are connected in parallel to form a protection device. Here, the circuit of the high frequency power supply 14 is connected to the input device 16.
However, the power supply 14 may be always inserted without providing an inserter.

When an accident occurs in such a power system, the current 20 flowing through the disconnector 11 as shown in FIG.
A superimposed current 2 in which a current with a frequency determined by the high-frequency power supply 14 of the transformer 13 is superimposed on the fault current
It becomes 1. Now, when a charging command due to an accident enters the input device 16 at the position indicated by the two-dot chain line 22, the position indicated by the two-dot chain line 2
At position 3, a superimposed current 21 of high frequency current is generated.

When the fault current 24 without a current zero point shown by the broken line flows through the circuit breaker 11, a high-frequency current is superimposed on this fault current, and the current zero points 26 and 27 are superimposed on this fault current, as shown by the superimposed current 21 shown by the solid line. The current is cut off at either current zero point. In this case, the fault current passes through the capacitor 12 to the transformer 1.
The capacitance of this capacitor 12 is set so that the current does not flow into the transformer, and when the high frequency power source 14 is used for the excitation current of the transformer, it is relatively easy to create a current zero point, and the capacitor's capacitance becomes small.

As described above, according to the present invention, when a fault current without a current zero point flows through a circuit breaker, a current zero point can be forcibly created in the superimposed current in which a high-frequency current is superimposed, so that the fault current can be quickly removed. A protective device can be provided that includes a shield that can be disconnected or the like.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing the protection device of the present invention, Figure 2 is a circuit diagram showing the protection device of the present invention.
The figure is a diagram showing the operation of the protection device of the invention. 11...Shiya disconnector, 12...Capacitor, 13
...Transformer, 14...High frequency power supply, 15...Surge suppression resistor, 16...Turning device.

Claims (1)

[Claims] 1. A protection device characterized in that a series circuit of a transformer and a capacitor having a high frequency power source is connected in parallel to a gas shield or disconnector for switching the main circuit of an electric power system, and a surge suppression resistor.