New arc extension circuit design and specifications for 4000MVA high power test facility expansion project

Korea Electrotechnology Research Institute (hereinafter referred to as `KERI') has expanded 4000MVA grade high power test facilities since 2011. The test facilities to be expanded include not only direct test facilities but also the test building under construction, which is capable of additional synthetic tests using exiting synthetic test facilities. To implement the new synthetic test building, KERI utilizes existing capacitor banks to generate the synthetic test current and is additionally implementing the reignition test facility that is applied to circuit breakers that have long arcing time. This paper described the design on reignition test facility for the synthetic test of the circuit breaker with long arcing time. The reignition circuit and test facility were composed of the current zero anticipator unit and the reignition circuit and the trigger unit. The reignition circuit was composed of the capacitor bank, the DC charger unit, resistors and reactors. The current for reignition was designed as the impulse current with 4kA peak and 160μs time constant. By the result of simulation on the 72.5kV and 31.5kA rated circuit breaker, using the current zero anticipator unit capable to control the time in the unit of 100μs provided a sufficiently large slope at the current zero point and did not create current chopping, which was considered to ensure the rated arcing time of the circuit breaker.

I. Introduction

KERI has expanded the high power test facility since 2011 [1]. The expansion project of the high power test facility included required all facilities of direct tests such as the short circuit generator, the short circuit transformer, the making switch, the backup breaker, the current limiting reactor, the disconnecting switch and auxiliary breaker. Because the performance of high-voltage circuit-breakers are so high that verification of their short-circuit interrupting capability under the full rated voltage is generally not possible with direct tests circuits, the synthetic test facility was also included in this projet[2] [3]. This project included the new synthetic test building that would additionally enable the synthetic test using existing synthetic test facilities. The new synthetic test building required not only connection of the voltage source circuit for the main trigger bank but also the additional arc extension circuit. In this paper, the design of the reignition circuit to be applied on the circuit breaker with a long arcing time was described. It can be said that the arc extension circuit is the test technology that is used to apply the circuit breaker with a relatively long arcing time to the synthetic test. In general, in the synthetic test of the circuit breaker with a relatively long arcing time, the test voltage applied lower than the rated voltage may break the circuit breaker before the rated arcing time of it. Because the correct test cannot be realized in this case, for the synthetic test to have the rated arcing time, applying the reignition current just before the current zero point is actually made or at the immediate previous current zero point to prevent the circuit breaker from breaking the current before the rated arcing time. Therefore, the reignition test facility can be considered one of the important test components for the success of the synthetic test. In this paper, described was the design on the reignition test facility (arcing time extension circuit) that would be newly implemented in KERI.