JPS59101728A - Protecting system for dc transmission system - 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 DC power transmission system, and particularly to a DC power transmission system suitable for multi-circuit or multi-terminal power transmission.

[Prior art]

DC breakers are applied to multi-circuit or multi-terminal DC transmission systems, and since the DC current used for removing faults on power transmission lines or switching systems does not have a natural current zero point, special measures are required to break it. is necessary. To cut off a large current or high voltage DC, a method is usually used in which an oscillating current is superimposed on the DC current to generate a current zero point, and the current is cut off like an AC circuit breaker. The circuit configuration of this type of DC breaker is shown in Figure 1. In the figure, the commutating capacitor 2 is constantly charged by a charging device (not shown), and when the circuit is cut off, the breaker section 1 is opened and the normally open closing switch 4 is turned on. The oscillating current generated by the current capacitor 2 being discharged via the reactor 3 is superimposed on the direct current flowing through the breaker 1 to generate a current zero point.

However, in this method, the current zero point occurs only at the cutoff section, so the DC current will not be cut off unless the energy remaining in the inductance of the DC line is absorbed. For this reason, a method is adopted in which nonlinear resistors 5 to 7 are installed to the ground or between the poles of the breaker 1 to process this residual energy.

[Purpose of the invention]

The purpose of the present invention is to reduce the size and cost of DC circuit breakers by significantly reducing the required amount of nonlinear resistance for energy absorption, which is the most expensive component for DC circuit breakers. It is.

[Summary of the invention]

The present invention focuses on the fact that, by analyzing the conditions under which a DC breaker operates on and off, it is not necessary to process a large amount of residual energy as long as the DC breaker does not operate unnecessarily. This is a condition that sets the conditions for the DC breaker's breaking operation.

That is, FIG. 2 shows a system configuration of a bipolar two-line system as an example of a multi-line DC power transmission system. In the same figure, DC breaker 1
Let's consider their responsibilities with a focus on

In order to consider the responsibility of the DC breaker 1, FIG. 3 shows only a single-pole system in which the DC breaker 1 is involved. The DC circuit breakers 11, 12, 15, 16, and 19.21 are always closed. Now, suppose that an accident occurs on the DC transmission line 39, the DC circuit breakers 11 and 12 are opened, and the DC transmission line 3
9 from the system and eliminate the accident. DC power transmission line 39
The DC current flowing through the DC power transmission line 41 flows through the connecting busbars 43 and 44. Therefore, the DC breaker 11
What is necessary is to process the energy remaining on the line from point A to the fault point on the DC transmission line 39.

, but DC breaker 1966? is a direct current flower cutter 21
If, for some reason, only the DC breaker 11 operates to cut off when is in the open state, it is necessary to process the entire energy of the unipolar system including the DC reactors 23, 24. Since DC, AC, and ACdles usually have a large inductance, their residual energy is enormous.The DC breaker is designed to absorb as much energy as possible in order to cope with the above-mentioned situations. Of all the equipment that makes up the device, the nonlinear resistance for storing residual energy is the most expensive.

Through these studies, it was found that switching means consisting of a DC breaker or switch installed on the DC line of a different line or terminal is closed, and the current flowing through the DC breaker connected to the power transmission line passes through the switching means. If a DC breaker operates to cut off only when the current can flow,
Nonlinear resistance can be made economical by reducing residual energy absorption.

[Embodiments of the invention]

Hereinafter, a specific embodiment for carrying out the F1 invention will be described with reference to FIG. The figure shows only one pole of the same polarity of the bipolar two-line DC transmission α system shown in FIG.

DC breaker 11 installed at both ends of DC transmission line 390
．． 12, the DC circuit breakers 19.21 installed on the buses 43 and 44 connecting the DC transmission line 39 and the DC transmission line 41 are checked to determine whether the DC circuit breaker 19.21 is in the closed state or open. A signal 51 is sent to the DC breaker 11.12 to prevent the DC breaker 19.21 from opening even if a shutdown command is input.
゜52 or 53.54 is a DC breaker 19゜21
If it does not indicate the closed state, an interlock is applied to prevent it from operating.

In FIG. 5, a signal 55.56 indicating the open/closed state of the DC breaker 19.21 is constantly sent to a control device 59 that sends a shutdown command to the DC breaker 11, 12, and the DC breaker 19.21 is A control circuit is constructed so that the control device 59 does not send a cutoff command to the DC breaker 11 or 12 unless it is in the closed state.

In FIG. 6, the A contact 60.61 of the auxiliary switch of the control circuit for the operating device of the DC breaker 19.21 is the cutoff command switch 6 of the control circuit for the operating device of the DC breaker 11.12.
2.63 is connected in series. In this configuration, when the DC breaker 19.21 is in the open state, the A contact of the auxiliary switch is in the 1 open state. The control circuits 64, 65 for the actuators of .12 are not excited, and the DC circuit breakers 11, 12 are not operated.

Although the explanation here was about DC breaker 11.12, other DC breaker for power transmission lines 13゜14.15.1
The same applies to 6, 17, and 18.

〔Effect of the invention〕

According to the present invention, the amount of residual energy in a DC transmission system that a DC breaker must handle can be significantly reduced, thereby significantly reducing the amount of nonlinear resistance needed to handle the residual energy.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing an example of the configuration of a DC breaker, Fig. 2 is a circuit diagram of a bipolar two-circuit DC transmission system configuration showing an example of a DC transmission system to which the present invention is applied, and Fig. 83 is a fragment of Fig. 2. 4 to 6 are circuit diagrams showing only poles, and FIGS. 4 to 6 are circuit diagrams showing different embodiments of the invention.

Claims (1)

[Claims] 1. In a DC power transmission system with multiple lines or three or more terminals, a DC breaker connected to a power transmission line is designed to ensure that the DC current flowing through the DC line to which the DC breaker is connected is A method for protecting a DC power transmission system, characterized in that a cutting operation can be performed only when a DC line is provided with a circuit number or terminal different from that of the DC line, and nine DC breakers or switches are closed. .