1. What is a surge?
Surge is also called a surge, as the name implies, is beyond the normal operating voltage of the instantaneous overvoltage. Essentially, a surge is a violent pulse that occurs in just a few millionths of a second. Possible causes of surges are: heavy equipment, short circuits, power switching or large engines. The products containing the surge blocking device can effectively absorb the sudden huge energy to protect the connected equipment from damage.
2. Characteristics of surges
Surge generation time is very short, about microsecond level. When a surge occurs, the amplitude of the voltage and current exceeds more than twice the normal value. This peak current is much larger than the steady-state input current because the input filter capacitor charges rapidly. The power supply should limit the level of surge that the AC switches, rectifier bridges, fuses, and EMI filter devices can withstand. Repeatedly switching the loop, the AC input voltage should not damage the power supply or cause fuses to blow.
This phenomenon usually lasts only a few nanoseconds to a few milliseconds
Surge occurs when the voltage and current values exceed the normal values by more thantwice.
3. The performance of surges
Surge is prevalent in the power distribution system, that is, the surge is everywhere. Surge in the power distribution system is mainly manifested by.
Voltage fluctuations
Under normal operating conditions, machinery and equipment will automatically stop or start
Electricity-using equipment with air conditioners, compressors, elevators, pumps or motors
Computer control systems often appear without reason to reset
Motors often have to be replaced or rewound
Electrical equipment has a shortened service life due to faults, resets or voltage problems
The following types of surges affect sensitive electronic and electrical equipment.
Damage
Voltage breakdown of semiconductor devices
Damage to the metallized surface layer of components
Damage to printed circuit board printed circuits or contact points
Damage to triac components/thyristors ……
Interference
Lockout, thyristor or triac element out of control
Partial corruption of data files
Error in data processing program
Errors and failures in receiving, transmitting data
Fault of unknown origin ……
Premature aging
Premature aging of parts and components, greatly shortened electrical life
Output sound quality, picture quality decline
4. Sources of surges
The power distribution system as a reference, then the surge can be divided into two kinds of system outside and within the system. According to statistics, the surge outside the system mainly from lightning and other systems impact, accounting for about 20%; the surge within the system is mainly from the impact of the system’s internal electrical load, accounting for about 80%.
-External – Mainly lightning strikes
-internal – switches of electrical equipment, etc.
Lightning.
-1, direct lightning, lightning strikes in lightning rods, lightning strips and a part of the building or refinery tower.
-2. Lightning electromagnetic radiation; the powerful magnetic field at the point of lightning strike radiates in all directions.
Lightning strikes even if it does not directly hit the building, it will also cause damage to the microelectronic equipment in the building, because as long as the center point of the lightning strike occurs within a radius of 2Km from the building, in the space within this range will generate an extremely strong electromagnetic field, all from this electromagnetic field across the power supply lines, networks and signal lines, etc., will be due to electromagnetic induction and generate a surge voltage on the line, and along the line into the building’s equipment input ports, which will destroy electronic
-3, lightning current shunt on the power and signal lines.
-4, lightning induction: lightning current from the lead line discharge process in the surrounding area to form a strong alternating magnetic field, in the magnetic field on the metal conductor to generate induced voltage.
-5. The local high potential formed at the site of the lightning strike.
-6, lightning department intrusion.
Direct lightning strikes hit the power line or lead line sparing lightning current, in the power line will produce lightning overvoltage and generate a strong electromagnetic pulse around the power cable, where a variety of power, signal and control lines within the range of this electromagnetic pulse will induce overvoltage, this part of the overvoltage will be transmitted alonga variety of lines to the back-end equipment, thus causing equipment misoperation or damage.
Internal surges in the power grid.
(1) The input and removal of large electrical loads.
Air conditioner, compressor, pump or motor
(2) Input and removal of inductive loads.
(3) Power factor compensation capacitor input and removal
(4) Short circuit fault
(5) Mechanical contacts
Mechanical switches include switching contacts of electromagnetic relays, push-button switches, keys, potentiometers with switches,etc.
-5. Classification ofsurges
