JPS62104427A - Branching reactor - 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 [Field of Application of the Invention] The present invention relates to a method suitable for eliminating current zero in a system in which a compensating shunt reactor is installed on the bus bar of a power transmission line with a large capacitance.

[Background of the invention]

For example, as shown in Paper No. 875 of the 1981 National Conference of the Institute of Electrical Engineers of Japan, ``Prediction of zero-miss occurrence of fault current,'' if rMffl that occurs during a power system fault is larger than the amplitude of AC, the current It is known that a phenomenon may occur in which the zero point does not occur.

・59.Currently, despite the occurrence of this no-current phenomenon, a command to open the circuit breaker is given to the circuit breaker due to the detection of an accident.

In this case, the circuit breaker mechanically opens the poles, but DC continues to be applied electrically, causing the circuit breaker to break due to arcing and contact melting. there is a possibility. Further, more than this, the problem is that the stability of the power system decreases due to the inability to eliminate faults for a long time.

Various studies have been conducted from the viewpoints of how to prevent this no-current phenomenon from occurring, how to quickly attenuate it after it occurs, and how to respond to it with circuit breakers or protective relays. . However, the reality is that there is no such thing as fixed.

This non-zero current phenomenon is said to easily occur in ultra-high voltage systems.

[Purpose of the invention]

In light of the above, an object of the present invention is to provide a system that can quickly eliminate the problem of zero current in a power transmission line with a large capacitance.

[Summary of the invention]

In ultra-high voltage power transmission systems, it is essential to install a shunt reactor between the bus bar or transmission line and the ground in order to compensate for charging current and suppress abnormal voltage in the event of an unbalanced accident. In the present invention, by installing a capacitor in series with the shunt reactor, a low-order frequency oscillation is caused in the current flowing out from the shunt reactor in the event of a transmission line fault, and this current causes the current passing through the circuit breaker to change. It is an attempt to create a zero point.

[Embodiments of the invention]

An example of an ultra-high pressure system to which the present invention is applied will be explained with reference to FIG. In the figure, electric station S1 has transformer TrotTrt,
This shows an example in which power is sent to an electric station S1 via power transmission lines Ll to L, and circuit breakers CBt to CBe are installed at both ends of the power transmission lines LI to Ls. Besides, shipping
F! In order to compensate for the capacitance IL of the L line, the circuit breaker CB
A shunt reactor Lh l” Lh e is installed on the bus side of the transmission line.
~When a two-wire short circuit occurs at a point on the receiving side of TJI, for example at point F in this figure, the delayed phase of the transmission line, that is, circuit breaker C
No current zero occurs in the current passing through BI. The reason for this is that the jH flow component determined by the pre-fault current, the DC component determined by the voltage at the time of the accident, and the DC component generated by the capacitance 1 of the transmission line act in a direction in which they are added to each other. When a shunt reactor is installed on the busbar side, as shown in Figure 4, the current that was flowing through the shunt reactor L at the time of the accident flows out through the fault point 1 (IZ in the figure). ), depending on the phase in which the fault occurs, this may lead to an increase in the transient DC current, making it more likely that the current will not reach zero. In the same figure, E, L
, respectively indicate the equivalent power supply and the equivalent reactance on the power supply side.

Therefore, even if a shutdown command is issued to the circuit breaker CB upon detection of an accident, the circuit breaker cannot be opened, and there is a concern that the circuit breaker may be damaged. The present invention seeks to compensate for the aforementioned drawbacks. FIG. 1 shows an embodiment of the present invention, which is the same as FIG. 1 except for the shunt reactor. In this figure, a capacitance C in series with the shunt reactor TJ b +~Lha.

The feature of the present invention is that ˜Cak is provided.

FIG. 3 is for explaining the effect of the shunt reactor proposed by the present invention, and in the same figure, C is the capacitance.

In the case of FIG. 3, the voltage applied to the reactor L and capacitor C causes a low-order harmonic current. The frequency f at this time is determined by f=2□17(1), and the magnitude of this current is determined as follows.

Here, ■ is the shunt reactor terminal voltage.

This current i. When becomes larger than the sum of the transient DC current l2 determined by the power flow and the transient DC component 1° determined by the charging current, the non-zero condition is resolved. From these relationships, the condition for eliminating zero is as follows.

Next, we will discuss the value of the capacitor installed in series with the shunt reactor.

If the degree of compensation of the shunt reactor is γ, and the ratio of the impedance of the capacitor at the system frequency to the actance of the shunt reactor is η, then Ct: the ground capacitance of the power transmission line, ω. =2πf0.

When η is calculated from (8) to (5), it becomes. If the condition shown in equation (6) is satisfied, the non-zero condition disappears rapidly.

〔Effect of the invention〕

According to the invention, the power flow in series with the shunt reactor.

By simply installing a capacitor determined by the terminal voltage 1 shunt reactor compensation degree, it is possible to solve the problem of no current zero.
The economic effects are extremely large.

[Brief explanation of drawings]

FIG. 1 is an ultra-high voltage power transmission system according to the present invention, FIG. 2 is a conventional system, FIG. 3 is a system diagram according to the present invention, and FIG. 4 is an analysis diagram of the conventional system. SI, S2...Electrical station, Tr+ l Trl "'Transformer, L.~L,... Transmission line, CD I"'= CB s...
Circuit breaker, Lh+~Lbe...Shunt reactor.

Claims (1)

[Scope of Claims] 1. A shunt characterized by installing a capacitor determined by the maximum power flow, operating voltage, and compensation degree of the shunt reactor in series with the shunt reactor installed to compensate for the charging current of the power transmission line. reactor. 2. In claim 1, when the maximum current is i_p, the maximum value of the operating voltage is e, the degree of compensation is γ, and the system frequency is f, the ratio of the impedance of the capacitor to the shunt reactor at the system frequency A shunt reactor characterized in that η is selected so that η<{1/[(2πf_oi_p/e)+γ]}^2.