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Home > Support > Basics of Surge Protector

What is surge? What is transient voltage surge?

Surge and Transient Voltage Surge are temporary rise in voltage and current on an electrical circuit. Their voltage ranges are greater than 2000 volt and current ranges are greater than 100 ampere. Typical rise time is in the 1 to 10 microsecond range. Transient or surge is the most common power problems and its compacts are caused significant damages such as electrical or electronic equipments failure, frequent downtime, lost data, lost time and business downtime, etc.

Where do surges come from?
The major of electronics damage from surge is lightning strikes. The most damages is not caused by direct lightning strikes, but is the result of transient voltage and current surges induced on power, telecommunications or RF transmission lines by the strong electromagnetic fields created by during a lightning strike. And more common causes of power surge are the operation of high-power electrical devices, such as elevators, air conditioners and refrigerators by switching on-off compressors and motor. Other sources of power surge include faulty wiring, utility power supply failure and electrical noise.

What is surge protector?
Surge protector also known as Transient Voltage Surge Suppressor (TVSS), Surge Protection Devices (SPD) or Surge Suppression Equipment (SSE) is the equipment designed to protect electrical and electronic equipments from power surges and voltage spikes. Surge protector diverts the excess voltage and current from transient or surge into grounding wire.

How surge protector works
Surge protector diverts the excess voltage and current from transient or surge into grounding wire and prevents it from flowing through the electrical and electronic equipments while at the same time allowing the normal voltage to continue along its path. This excess energy can cause damages in electrical and electronic equipments, process control instruments-equipments.

Two main functions of the surge protector are
1. Provides low impedance path for conducting a lot of current to eliminate the extra voltage.
2. Absorbs and diverts the extra current to ground for protecting the effects of transient or surge.

Surge protector types
Surge protector are classified into two types as

  • Filter is a device that serves as barrier to high frequency current that is often noise, while allowing the low frequency power current to pass through unaffected.
  • Transients Diverter is a device that presents a very low impedance path to ground whenever voltage across the device exceeds certain value, but reduces voltage that could be presented to the sensitive equipments.

Surge protector components
The components used to reduce or limit high voltage usually includes MOV, Gas Discharge Tube, Silicon Avalanche Diode, etc. or combinations of these components. Each of these components is different features as follows:

  • MOV (Metal Oxide Varistor) composes of zinc oxide material, which is semiconductor with a variable resistance. In normal condition, MOV presents itself as a high impedance device but when voltage is too high, the resistance of MOV drops rapidly to provide a low impedance path of flow. MOVs have finite life expectancy and degrade when exposed to a few large transients, or many smaller transients. MOV is the most common component in AC surge protector.
  • Gas Discharge Tube (GDT) can divert the excess current from line to ground by using inert gas as conductor from hot line to ground line. In normal condition, the inert gas acts as poor conductor, but when voltage is above the acceptable level, the inert gas is ionized to be effective conductor to pass on current to ground until voltage returns to normal level. GDT will conduct at a voltage less than the high voltage that ionized the gas and able to conduct more current for their size than other components. GDT has a finite life expectancy, and can take a few very large transients or a greater number of smaller transients.
  • Silicon Avalanche Diode (SAD) provides the perfect limiting action of protective component, but has a lower current capability. When voltage increases above the limit level, SAD will tolerate avalanche breakdown resulting voltage is conducted to ground.
  • Other important components, such as resistors, capacitors and/or inductors, are used in conjunction with these protector components above.

Why do you need surge protector?
Nowadays a lot of electronic components in modern electrical devices are much smaller, delicate and more sensitive to current increases. Microprocessor which is an integral part of all computers and many modern electrical equipments, are particularly sensitive to surge. Your electrical equipments can be exposed to damaging surges from AC power line and telephone or signal lines.
Surge protector is suitable to use in every applications that connect to electricity (the utility power supplies or the locally generated), telephone lines (such as modem, fax, data, etc.), computer data lines and communication lines, etc. as follows:

  • Computers and peripherals such as printer, monitor, speaker, fax machine and modem, etc.
  • PABX and communication equipments, etc.
  • Entertainment components
  • Medical equipments, surgical equipments and scientific equipments, etc.
  • Weighting bridges and measuring equipments, etc.
  • Electrical equipments
  • Security systems

Surge protector location
Surge Protector is typically applied at several points throughout a facility. ANSI/IEEE C62.41-1991 standards define three categories of surge level, based on strategic location within a facilities wiring network, where power problem may be encountered. They classify the surge protector type, the potential impact of transient surge or spikes, and location as follows:

  • Category A: Defined as any outlets and long branch circuits extending more than 10 meters (30 ft.) from category B location or 20 meters (60 ft.) from category C. Surge protector for this location category is applied at the outlets or individual circuit level for individual protection of a specific piece of equipment such as computers, weighting bridges, measuring equipments, process control equipments and DC power supplies, etc.
  • Category B: Defined as all major sub-feeders, bus systems, and short branch circuits such as distribution panels, industrial busses and feeder systems, heavy appliance circuits, lighting systems in large building. The protection at this location is very effective in suppressing the much more frequent internally generated transients, ever-changing transient conditions, especially, sensitive equipments and equipments which are fed from the substations.
  • Category C: Defined as outside and main service entrance which includes main supply lines, transformer, service connections, and feeder line to main service entrance panels, any overhead or sub-feeders lines, underground lines to well pump. This surge protector type is applied to protect against externally caused power disruptions. This installation will help guard against lightning strike entering a facility via the power line.

These three categories A, B and C determine which surge protector or TVSS should be used at which location.

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