High-voltage DC current breaker and high-voltage DC current breaking method
Provided is a DC current breaker having a high-speed breaking function appropriate to a voltage-type converter and a DC current breaking method. In addition, provided is a DC current breaker and a DC current breaking method capable of reducing cost of the breaker and securing economical competiveness by using a relatively simple configuration. The DC current breaker for breaking a DC current at the time of occurrence of an accident includes: a main conduction unit including three high-speed mechanical switches installed to be connected in series to a main conduction path for conducting a normal-operation-state current; a power semiconductor switch installed to be connected in parallel to one high-speed mechanical switch among the high-speed mechanical switches installed in the main conduction unit for current breaking of the main conduction unit; a capacitor installed on a circuit connected in parallel to the main conduction path; and a surge arrester installed to be connected in parallel to the capacitor connected in parallel to the main conduction path. The DC current breaking method uses the DC current breaker.
1. A DC current breaker for breaking a DC current at the time of occurrence of an accident, comprising:
a main conduction unit including a commutate switch, a protection switch, and a close/open switch which are connected in series to each other in this order on a main conduction path where a current is flowed in a normal operation state, the protection switch protecting the commutate switch, and the close/open switch finally breaking a flow of a current of the main conduction unit;
a power semiconductor switch connected in parallel to the commutate switch;
a capacitor connected in parallel to the commutate switch and the protection switch; and
a surge arrester connected in parallel to the capacitor,
wherein the commutate switch is a mechanical switch having a rated voltage which is lower than rated voltages of the protection switch and the close/open switch,
wherein an opening response characteristic of the commutate switch is faster than opening response characteristics of the protection switch and the close/open switch, so that an arc voltage is more speedily increased than those of the protection switch and the close/open switch,
wherein the capacitor has electrostatic capacitance so that, when a transient voltage applied at the time point when a current of the main conduction path is broken by the power semiconductor switch is shared by the protection switch and the commutate switch, a magnitude of a transient voltage across the protection switch and the commutate switch does not exceed a limit value of a withstand voltage of the power semiconductor switch.
2. The DC current breaker according to claim 1 , wherein a forward voltage of the power semiconductor switch is lower than an arc voltage generated when the commutate switch is opened in a conduction state, and the power semiconductor switch is turned on by the arc voltage generated in the commutate switch, so that a current flowing through the main conduction unit is commutated to the power semiconductor switch.
3. The DC current breaker according to claim 1 , wherein the commutate switch is a monostable switch, the commutate switch receives a trip signal of the DC current breaker to start an opening operation, and after a time point when the current of the main conduction unit is completely commutated to the capacitor, the commutate switch automatically returns to a closed state.
4. The DC current breaker according to claim 1 , further comprising a discharge unit for discharging a voltage charged in the capacitor after a DC current breaking operation is finally finished by the close/open switch.
5. The DC current breaker according to claim 4 , wherein the discharge unit is configured to include a discharge switch and a discharge resistor which are connected in series to each other on a discharge path connected in parallel to the capacitor.
6. The DC current breaker according to claim 1 , wherein the power semiconductor switch is formed with a single one-directional conduction switch or is formed by connecting two one-directional conduction switches reversely in series to each other and connecting free wheeling diodes in parallel to the respective one-directional conduction switches.