JPS59103235A - Dc transmission system controlling and protecting 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 control and protection system, and in particular, a DC power transmission system control and protection system suitable for a multi-line, multi-terminal DC power transmission system using a DC breaker. Regarding.

[Prior art]

If a DC breaker is applied, the degree of freedom of the p system is increased.

Reliability can be improved. However, since a DC breaker is a complex device, it is orders of magnitude more expensive than an AC breaker. When an economical DC breaker is applied, it becomes difficult to protect all possible conditions using only the DC breaker.

There is a need for a highly reliable control and protection system for DC power transmission systems that allows the application of economical DC circuit breakers.

[Purpose of the invention]

An object of the present invention is to provide an economical control and protection system for a DC power transmission system using an economical DC breaker without reducing reliability.

[Summary of the invention]

The present invention prevents this decrease in reliability by controlling and protecting the converter, and enables economical controlled mining.

[Embodiments of the invention]

The circuit configuration of a DC breaker according to an embodiment of the present invention is shown in FIG. 1, and the circuit diagram of a two-line multi-terminal DC transmission system to which this DC breaker is applied is shown in FIG. The equipment includes a commutation breaker CB, a commutation capacitor C2, a commutation reactor L, a resistor r, a closing switch S, and a surge absorber z.
Consists of nO.

This DC breaker does not have a special charging device to charge the commutating capacitor 〇, and charges it from the line.

In the steady operating state, the commutation breaker CB is in the closed state and couples the direct current IDC. When the closing switch S is in the open state, the capacitor C is charged to a voltage equal to the rated voltage of the line via the resistor r. The surge absorber ZnO is in a non-conductive state.

When the circuit is cut off, the commutation breaker CB is opened and the closing switch S is turned on. As a result, the charge in the capacitor C is discharged via L, and a high frequency oscillating current flows through the circuits C-L and -8-CB. This oscillating current is superimposed on the DC arc current generated between the poles of commutating circuit breakers C and B, generating a current zero point, and commutating circuit breaker CB extinguishes the arc in the same manner as alternating current. Current IDC flows into capacitor C and increases the voltage at its terminals. When the voltage of the capacitor C reaches a predetermined value (for example, 1.6 times the rated voltage of the line), the surge absorber ZnO becomes conductive, and the current IDC flows into the surge absorber ZnO and is current-limited and cut off.

FIG. 2 shows the system configuration and the installation location of the DC breaker when this economical DC breaker is applied to a two-line multi-terminal DC transmission system.

Forward converter EC, DC reactor 1) CL, main line.

One line is composed of a DC reactor 1) CL, an inverter 10V, and a wire ml. Other lines with exactly the same configuration are installed in parallel. DC cutoff 61-4 and 9-1
2 is for the main line), and the rated voltage is high.

The DC circuit breakers 5 to 8 and 13 to 16 are for return wires and have low rated voltages. In particular, the DC circuit breakers 17 and 18 are for opening and closing between the main lines, and the DC circuit breakers 19 and 20 are for opening and closing between the return lines.The circuit configuration of both DC circuit breakers is shown in Figure 1. are the same.

In the steady operating state, all DC circuit breakers 1 to 20 are in the closed state. When the power transmission capacity of each line is equal, almost no current flows through the DC circuit breakers 17, 18 and 19, 20 between the lines; when the capacitance is different, current is flowing, and upon opening, Cutting ability is required.

When a ground fault occurs at point a of main line t, current from other lines flows through the interline DC breaker 17, so a current twice the rated current IDC flows into point a. In this case, even if the DC breaker is disconnected, the current flows further through the line-to-line DC breaker 18, so the ground fault arc continues. Therefore, the ground fault can be eliminated only after the DC breaker 3 is turned off. After the ground fault is cleared, power transmission will continue using the overload capacity of the other transmission lines.

When performing special control such as overall startup control or power flow reversal control, install direct current circuit breakers 17 and 18 and 19 and 2 in advance between the lines.
After opening 0 and creating an independent 2-terminal power transmission system, control each EC and NV, and after completing control of all 2-terminal systems, turn on 17, 18, 19, and 20. and enters steady operation.

If an accident occurs during the special control period, the two-terminal power transmission system where the accident occurred will stop power transmission under the control of the converter. If the power transmission power cannot be reduced, the system switches to overload operation of the remaining healthy two-terminal power transmission system and continues power transmission.

〔Effect of the invention〕

According to the present invention, the line voltage is lower than the rated voltage, the charging voltage of the commutating capacitor of the DC breaker is insufficient, the breaking ability is reduced, and the DC breaker cannot protect the system. If the system is not available, the system is protected by converter control, so it is possible to create an economical DC transmission system using an economical DC breaker without reducing reliability. be.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a DC breaker applied to one embodiment, and FIG. 2 is a circuit diagram of a two-line multi-terminal DC power transmission system to which the DC breaker is applied. 17.18... DC breaker between main lines, 19.20...
・DC breaker between return lines.

Claims (1)

[Claims] 1. In a multi-circuit, multi-terminal DC power transmission system in which the switch for opening and closing between each line is operated in the closed state during steady operation, when performing converter control such as overall start-up control and power flow reversal control, the above-mentioned line A direct current power transmission system control and protection method characterized by opening a switch between lines, then controlling a converter, and then turning on a switch between lines.