JPS5846525A - Power circuit - Google Patents

Abstract

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

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power circuit, and is particularly suitable for improving a phenomenon in which a short-circuit fault current has a large direct current component and a current zero point does not appear temporarily in the fault current, the so-called current non-zero phenomenon. Regarding power circuits.

Research and development efforts to reduce losses in generators and transformers have continued over a long period of time, and the need to improve system stability has led to efforts to shorten the operating times of relays and circuit breakers. achieved. However, depending on the operating conditions and accident conditions of the generator and power transmission system,
As shown in the figure, steady-state operating current i. When the short-circuit fault current i increases due to the fault that occurred at time to, the DC component included is large compared to the AC distribution width at that point, so a phenomenon occurs in which the current zero point does not appear for several cycles. However, there is a possibility that the circuit breaker may be opened during the L period when the current is zero.

In general, AC circuit breakers have the property of not being able to shut off unless a current zero point appears in the arc current.

In addition, a circuit breaker has a certain arc time width that is determined by its structure and breaking method, and if the current zero point does not appear within this time width, the current cannot be interrupted. Become.

As a countermeasure against this problem, systems based on almost the same principle as DC breaker have recently been proposed, but it is thought that there is still room for improvement in terms of economical efficiency and operational reliability.

SUMMARY OF THE INVENTION An object of the present invention is to provide a power circuit that can eliminate the current zero phenomenon and reliably cut off the current.

In the case of an accident on the high voltage side of a transformer, the present invention generates an arc voltage in series in the low voltage side circuit, commutates it to the parallel resistance, and converts the resistance to the high voltage side, allowing easy comparison of commutation. Focusing on the fact that the equivalent resistance can be large enough to eliminate the zero current phenomenon with a resistor of a relatively small value, by inserting a resistor in the low voltage side circuit, the current zero generated in the high voltage side circuit can be reduced. This is designed to eliminate the phenomenon of no data.

FIG. 2 is a circuit diagram showing an embodiment of the present invention.

From a generator 2 whose neutral point is grounded through a resistor 1, a circuit breaker 3
, the power transmission line 1 is passed through the breaker 5 having the parallel resistance 4, the low voltage winding 7 of the transformer 6, the high voltage winding 8, and the high voltage breaker 9.
Assume that power is being supplied to 0.

For example, a part of a power transmission line has a ground fault at point A or A.

If a short circuit occurs between the lines at point B, the circuit breaker 5'f
t: Open the terminal and insert the resistor 4 into the low voltage circuit. This mechanical resistance 4
can be converted to the high voltage side circuit by the square of the voltage ratio between the high voltage side and the low voltage side. 100K VRUHV (Ultra
When considering a Higb Voltage) system, it is easy to generate an equivalent resistance of about 100 on the high voltage side using this method, and it is sufficiently effective in eliminating the current non-zero phenomenon.

It is desirable that the command to shut off the circuit breaker 9 be delayed from the command to operate the circuit breaker 5, but if the opening time of the circuit breaker 5 is equal to or shorter than that of the circuit breaker 9, there is no problem even if the circuit breaker 9 opens almost simultaneously.

Although not shown, the high-voltage side circuit of the transformer is often connected to a two-line power transmission line, etc., and from the viewpoint of continuing the power supply
Second, it is necessary to select a resistance value that is low and large enough to eliminate the phenomenon of zero current in the high-voltage side circuit within a predetermined time.

Due to an accident in the high voltage side circuit, a zero current phenomenon may occur in the current flowing through the breaker 5. Therefore,
The breaker 5 may open only a specific phase or all three phases at once, as necessary.

As shown in Figure 2, when the breaker 5 is installed on the low voltage side, the value of the resistor 4 required to eliminate the no-current phenomenon is the square of the voltage ratio compared to when the breaker 5 is installed on the high voltage side. Since it can be small in proportion to the inverse ratio of Compared to the high pressure side,
It has the characteristics of being economically viable.

As explained above, if a breaker and its parallel resistance are installed in the low voltage circuit of a system connected by a transformer, and a no-current phenomenon occurs on the high voltage side due to an accident on the high voltage side,
By opening the circuit breaker installed on the low voltage side, a phenomenon similar to that of inserting a relatively large resistor in series in the high voltage circuit with equal constraints occurs, rapidly eliminating the no-current phenomenon, and reducing the high voltage. A side breaker can provide reliable current interruption.

In the embodiment shown in FIG. 2, depending on the system configuration and the arc voltage characteristics of the breaker, the resistor 4 connected in parallel to the breaker may be removed, and the arc of the breaker or the arc voltage generator that generates the highest possible arc voltage. The non-zero current phenomenon in the high-voltage side circuit can be resolved only by using a resistor.

FIG. 3 is a circuit diagram showing another embodiment of the present invention. In the figure, the same members as used in FIG. 2 are given the same reference numerals. In this embodiment, the resistor 4 in the embodiment shown in FIG.
A fast-operating switch 11 is connected in parallel with the switch. The other configurations are the same as those in the embodiment shown in FIG. 2, so their explanation will be omitted.

After the fault current is interrupted by the breaker 9 on the high voltage side in the same manner as in the previous embodiment, the resistor 4 is short-circuited by the breaker 11, and then the breaker 5 is closed, thereby protecting the resistor 4 from thermal destruction. can be protected.

When a short circuit accident occurs in a system consisting of a low voltage circuit and a high voltage circuit connected by a transformer, the present invention inserts a low resistance component into the low voltage circuit. This is equivalent to inserting a large resistor, and the no-current phenomenon can be effectively eliminated.

[Brief explanation of the drawing]

FIG. 1 is a current waveform diagram showing a state without zero current, FIG. 2 is a circuit diagram showing an embodiment of the invention, and FIG. 3 is a circuit diagram showing another embodiment of the invention.

Claims (1)

[Scope of Claims] 14. In a power circuit that has a transformer in the system in which a low voltage winding is connected to the power generation side and a high voltage winding is connected to the power transmission line side, a breaker having a parallel resistance valve is connected to the low voltage circuit. established,
A power circuit characterized in that the breaker is opened when a zero current state occurs in the high voltage circuit. 2. The power circuit according to claim 1, wherein the breaking section is any arc voltage generator without breaking performance. 3. The power circuit according to claims 1 and 2, wherein the parallel resistance basin is an arc resistance.