Hybrid direct-current circuit breaker

Abstract

The invention discloses a no-arc cut-off hybrid direct-current circuit breaker. The no-arc cut-off hybrid direct-current circuit breaker comprises a high-speed vacuum switch, an LC forced branch circuit of a turn-off device with a power electronic gate, a voltage-sharing capacitor, an over-voltage limiting circuit and a control system, wherein the high-speed vacuum switch VB, the LC forced branch circuit and the over-voltage limiting circuit are connected in parallel. The turn-off device of the LC forced branch circuit is controlled to be conducted and turned off so that the no-arc opening of the high-speed vacuum switch can be realized, and electric current in the high-speed vacuum switch limits di / dt in a smaller range within a short period of time before zero passage, thus the problem that electric arcs ablate switch contacts is eliminated in the cut-off process of the contacts, simultaneously, the recovery character of a medium between the contacts is good under the no-arc breaking condition, and the over-voltage is low, and the break-time is short in the breaking process under the low di / dt condition.

Description

technical field [0001] The present invention relates to a hybrid DC circuit breaker, in particular to a device unit that can be turned off by a power electronic gate to control the discharge of a forced transfer circuit LC to achieve arc-free breaking and limit the rate of change of zero-crossing current to a relatively low range. breaker. Background technique [0002] In recent years, with the continuous growth of power system capacity and the continuous increase of power load, the level of short-circuit current in the power grid is increasing, especially for some specific power use occasions, such as power supply systems on large ships, rail transit power supply system, etc., the peak value of the short-circuit current can reach more than 100kA, and the rate of rise of the short-circuit current is extremely high (over 20A / μs). The traditional mechanical circuit breaker is limited by its own physical mechanism. When the moving and static contacts are separated, an arc will...

AI Technical Summary

Problems solved by technology

However, compared with mechanical switches, solid-state switches have a large loss in normal flow conditions, serious heat generation, and require a complex cooling system, so their rated load-carrying capacity is limited

At the same time, solid-state switches also have great limitations in terms of anti-inrush ability and anti-system overvoltage.

On the other hand, during the breaking process of the HVDC circuit breaker, due to the large peak value of the breaking current, there is usually a high change rate di / dt when the current crosses zero, such as figure 1 For the curve AB shown in , not only is it difficult to accurately predict the current zero crossing point, but also it is impossible to control the high-speed mechanism to drive the contacts to open at the current zero crossing point, and the high di / dt breaking will generate high overvoltage, resulting in dielectric shock between the contacts Wear, and then cause breaking failure

Images