Arc suppression

Abstract: This paper proposes a flexible neutral grounding method based on electromagnetic hybrid Petersen coil (EHPC), which consists of a magnetically controlled reactor and an active power compensator (APC). Under normal conditions, the system's neutral point grounds through a reactor of high reactance. When a single line-to-earth fault occurs, the EHPC can be controlled flexibly to suppress the recovery voltage of faulty phase and to reduce the ground-fault current to almost zero. This paper expounds the two operating modes and corresponding characteristics, the measuring method of insulation parameters of the system (mainly including capacitance to earth and leakage resistance), and the full compensation principle for arc suppression based on the equivalent negative impedance of EHPC. This paper also proposes a compound control method of neutral-to-earth impedance based on neutral-point displacement voltage and a compensating method for the harmonic component of the ground-fault current. Compared to traditional grounding methods, this method can be fast and reliably make the residual current approach almost zero without arc reignition while greatly reducing the output capacity of APC and, thus, decreasing the cost of this device. Simulations and experiments verify the correctness of this measuring method and feasibility of this flexible grounding control strategy.

Abstract: Traditional arc-suppression devices have a weak effect on the arc-extinguishing result of earth fault because of increased active and harmonic components of fault current. To solve the problem, in this paper, a flexible arc-suppression device based on a three-phase cascaded H-bridge (CHB) converter with auxiliary sources is further developed; on this basis, an arc-suppression method based on the improved finite control set model predictive control is proposed. The proposed approach, which uses a combination of two voltage levels in a sampling period to reduce the steady-state current error, controls the CHB converter to inject compensation current into the distribution network. Taking into account the reduction of switching losses and balancing heat in each H-bridge cell, a novel method that causes the switching transitions to be distributed evenly among the H-bridge cells is proposed to select the optimal switching combination. The tracking capability of the improved control method is analyzed, and the parameters affecting the arc-suppression performance are obtained. The simulation and experimental results show that the proposed method achieves an excellent performance of suppressing fault current and extinguishing arc. Moreover, the balance of switching transitions is also achieved.

Abstract: A high voltage DC relay with arc suppression in which a MOSFET in parallel with the relay contacts is turned on during contact break mode by the controlled discharge of a capacitor between the MOSFET source and drain through a constant current diode to suppress arcing. A sensing coil positioned near the relay coil generates current used to charge the charging capacitor during the make contact mode to suppress arcing.