Surge (Electrical surge), as the name implies, is an instantaneous peak beyond the stable value, which includes surge voltage and surge current.
Surge voltage is an instantaneous overvoltage that exceeds the normal operating voltage. Essentially, a surge is a violent pulse that occurs in just a few millionths of a second. Possible causes of surges include heavy equipment, short circuits, power switching or large engines. Products containing surge arrestors can effectively absorb sudden bursts of huge amounts of energy to protect connected equipment from damage.
The sources of power supply system surges are divided into external (lightning causes) and internal (electrical equipment start/stop and failure, etc.).
External causes:
Lightning strikes may act in two ways on the low-voltage power supply system:
(1) direct lightning strikes: lightning discharges directly hit the components of the power system, injecting a large pulse current. The probability of occurrence is relatively low.
(2) Indirect Lightning Strike: the lightning discharge strikes the earth near the equipment, inducing moderate currents and voltages on the power lines.
Direct lightning strikes are the most serious events, especially if the lightning strikes an overhead transmission line near a customer's inlet. During these events, overhead transmission line voltages rise to hundreds of thousands of volts, often causing insulation flashover. Lightning currents travel over distances of one kilometer or more on power lines, with peak currents of 100 kA or more near the point of strike. The current in the low voltage line at the customer's inlet can reach 5kA to 10kA per phase, and in areas with high lightning activity, power facilities may be subjected to several direct lightning strikes per year causing severe lightning currents. In areas with high lightning activity, power facilities may experience several direct lightning strikes per year resulting in severe lightning currents. These events are rare when power is supplied by underground power cables or in areas where lightning activity is infrequent.
Indirect lightning strikes and internal surges have a higher probability of occurring, and the vast majority of damage to electrical equipment related to it. Therefore, the focus of the power supply surge prevention is the absorption and suppression of this part of the surge energy.
Internal causes:
The reason for the occurrence of internal surge with the power supply system within the equipment start and stop and power supply network operation faults:
Power supply system due to the start and stop of high-power equipment, line faults, casting and cutting action and inverter equipment, etc., will be brought to the internal surge to the power equipment to bring about adverse effects. Especially computers, communications and other microelectronic equipment to bring a fatal impact. Even if no permanent equipment damage is caused, abnormalities and stoppages in system operation can have very serious consequences. For example, nuclear power plants, medical systems, large-scale factory automation systems, stock exchange systems, telecommunication bureaus with switches, network hubs.
Surge protector, also known as lightning protector, is a kind of [1] for a variety of electronic equipment, instrumentation, communication lines to provide safety protection of electronic devices. When the electrical circuit or communication line because of external interference suddenly produced a spike in current or voltage, the surge protector can be in a very short period of time conduction shunt, so as to avoid surge damage to other equipment in the circuit.