Why do I need to install a circuit breaker?

With the advancement of human civilization, there is an omnipresent application of electricity in human life. The use of electricity greatly facilitates human life. However, there is a kind of disaster called thunder and lightning in the natural world. But it has greatly jeopardized human power facilities. Today, Lei Zhenzi's power surge protectors will tell you why power surge protectors must have circuit breakers on their front end.

The core component of the power surge protector is the varistor, which has high-pass and low-resistance characteristics. When the grid operates without exceeding the maximum continuous operating voltage, the two electrodes are in a high-impedance state. If the voltage between two electrodes exceeds the ignition voltage due to a lightning strike or overvoltage operation, the gap is broken and the overvoltage energy is released by the arc discharge. After the shock wave passes, the arc will be extinguished by the arc extinguishing system consisting of the arc segment and the arc extinguishing chamber, and the high impedance state will be restored to protect the system.

The function of the domestic Lei Zhenzi power surge protector: If the power surge protector itself fails, there will be a long-term connected state, causing a short circuit in the power supply or power distribution system. At this time, the front-end circuit breaker or fuse must be cut off in time. Ground loop to ensure the normal operation of the loop.

Power surge protector front circuit breaker or fuse action: how does this circuit breaker or fuse discriminate whether it is a short circuit caused by a short circuit caused by a lightning strike (called α) or a damage of a power surge protector itself (called β), Because if α is discriminated as β, the circuit breaker will be disconnected and the main circuit will be destroyed; if β is discriminated as α, the main circuit will continue to short circuit and it will also cause the circuit to burn down.

The lightning protection of the power surge protector we use is actually not a direct lightning strike that can destroy everything, but a high-voltage peak, large current, and very short-time induction lightning. The fuse needs to meet certain conditions to be blown, that is, energy accumulation. The transient lightning strike obviously will not blow the fuse when the power surge protector is working. Because of the fuse, neither the alpha nor the beta will burn the circuit, only the fuse will be disconnected and the circuit and ground will be safely disconnected.

The purpose of domestic Lei Zhenzi power surge protector plus fuse:

(1) Prevent freewheeling of the power frequency (for discharge gap type devices) damage to the SPD and its wiring due to lightning strikes.

(2) Easy maintenance Replace SPD.

(3) The aging of the power surge protector (such as the increased leakage current of the mov device) will cause the line fault. The front fuse of the power surge protector shall be installed according to the parameters of the domestic Lei Zhenzi power surge protector manufacturer. For example, Lei Zhenzi's power surge protector manufacturers do not specify, the general selection principle: according to (the maximum fuse fuse strength of the surge protector α) and (maximum supply current β of the connected distribution line) to determine (air open or fuse Breaking current γ).

(4) Determination method (according to “Code for Construction and Quality Acceptance of Building Lightning Protection Engineering” GΒ50601-2010 ):

When: α>β γ≤α

When: β=α, γ<α or no γ

When: β<α, γ<β or no γ