Surge Protection F.A.Q
PSP Products Inc.
8535 Phoenix Drive
Mannassas, VA 20110
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What is the difference between lightning protection and surge protection?
This is a topic that can get quite lengthy . Think of lightning protection as a means to protect equipment, facilities and people from the effects of nearby or direct lightning events. Whereas, surge protection provides protection to equipment from the effects of more distant lightning events and/or power system anomalies. In purely scientific terms, lightning can be described by a waveform of 10/350µs, while surges are described by an 8/20µs.
What is a surge protector?
A surge protector is an electronic device that limits transient over voltages  protecting equipment from damage or disruption. A surge protector may also be expressed using the following terms: SPD (Surge Protective Device), TVSS (Transient Voltage Surge Suppressor. An arrestor (used by utility companies and communication companies) is also a surge protector, but is typically employed in a different part of the electrical system than a surge protector.
How does a surge protector work?
A surge protector works by momentarily “switching” from an open circuit mode into a low impedance mode. This low impedance mode diverts the surge current through the protector and in doing so, limits the over voltage to a safe level. When the surge event is over, the protector returns to its open circuit mode, ready for the next event.
What is a metal oxide varistor
A metal oxide varistor is a voltage-dependent, semiconductor-based, variable resistor. Electrically, it appears as an open circuit across a power line until its voltage threshold is reached. When this occurs, the varistor will instantaneously change from a high resistance mode (open circuit) to a low resistance mode (short circuit),  conducting currents through it. Once the over voltage event has passed and the voltage returns to below the threshold level of the varistor, it will return to an open circuit again until the next over voltage event that exceeds its threshold occurs.
How do we select the right size device?
Device size is determined by a number of element like , size of distribution transformer, surge environment, importance of equipment , cost of downtime, etc.
breaker. Parallel protectors are commonly used where large surge energies exist. They’re used on service entrance panels and switchgear, plus branch and local panels. There are lots of reasons why parallel protectors are very popular. They are proven reliability and effectiveness. They are easy to install. And since parallel connected protectors do not have to support system load currents, they are relatively small and not costly. Parallel connected protectors are the staple for all AC applications, except the aforementioned small equipment level applications.