610 / 2017-05-15 16:52:20

Simulation of pressure relief valve movement in the compression volume of a self-blast interrupter

self-blast,pressure relief valve ,circuit breaker

Most of the failure of the high voltage circuit breaker reported is known as a defect in the mechanical operation. Thus, there has been a lot of effort to reduce the operating energy and improve overall mechanical reliability. Thanks to the development of innovative interrupting principles, the breaker with the latest interrupting principles now uses much less operating energy than the conventional circuit breaker, which makes it possible to apply a low-energy spring mechanism instead of a high-energy hydraulic or pneumatic one, leads to longer service life.
The self-blast principle of extinguishing the arc by the blast pressure which is generated by the arc itself has been widely applied worldwide and has been applied to the 420/550 kV single break circuit breaker. In the case of high currents interruption in the self-blast principle, the arc energy produces a high overpressure in the thermal volume, which leads to the closure of the check valve and thus isolating the thermal volume from the compression volume. The current approaches zero and the gas from the thermal volume blasts up through the nozzle, cooling the arc and extinguishing it. Excessive pressure in the compression volume is released through the pressure relief valve fitted on the piston.
The design of the pressure relief valve operation is very important for the performance of self-blast interrupter. In case of higher short-circuit current, the pressure relief valve limits overpressure in the compression volume and prevents mechanical shock to the operating mechanism. On the other hand, in the case of lower short-circuit current, it is ensured that the valve is closed for a certain period of time and its operation as a puffer piston is necessary for the interruption.
Practically, the movement of pressure relief valve is actuated by the spring force. The operating pressure is set according to the spring tension and the cross-sectional area of the valve plate so that the valve is designed to open when the overpressure becomes greater than the designated operating pressure. In the conventional gas flow analysis for the self-blast interrupter, it has been simulated that this movement of pressure relief valve is instantaneously happened. It means that the pressure relief valve is instantly opened when the pressure of the compression volume becomes greater than the designated value of pressure relief valve. But, the movement of the pressure relief valve in reality is observed to gradually move according to the pressure difference. This gives a notable difference in the simulation analysis of the compression chamber pressure.
In this paper, the actual movement of the pressure relief valve is simulated analytically and compared with the actual experimental results. The difference between models which simulate the movement of the pressure relief valve and the effects of different pressure relief valve models are analyzed by gas flow simulation tools. This will help greatly in the design of a self-blast circuit breaker as the operation of the pressure relief valve is optimized by the simulation method presented in this paper.