Surge Suppression and LPS

[cslater]

I have a few questions about Surge Suppression as it relates to Lightning Protection.

1) Is the primary purpose to protect equipment from damage or to prevent a surge from coming up a wire and starting a fire?

2) In a catenary LPS system that has surge suppression at the 12kV side (i.e. on the pole), and where all of the secondary voltage is within the protected area, is there a need for surge suppression at the panel?

3) For low voltage systems (like alarms) are there external surge suppression systems that can be installed to protect from a surge travelling along these wires and starting a fire?

Thanks in advance for your help.

 

[juleselec]

Hi cslater,

1) The primary purpose is to protect equipment from voltage transients, which can damage electronic equipment and contribute to insulation degradation of other equipment. Preventing fire due to propagating transients is also a goal of course, but LPS and surge protection is supposed to protect against both.

2) Typically, you'd have some kind of surge arrestor at the main cable entry point into the building, where a propagating voltage surge could affect the equipment inside (or start a fire). If you already have instaled a lightning arrestor for the equipment outdoors, then a lower rated surge protection device for the building (e.g. MOVs) may be suitable for other transients (e.g. switching).

3) By low voltage systems, I presume you're talking about control and instrument cables. You don't normally protect these against lightning, I guess because it's rare that they'll suffer voltage transient effects. In any case, I can't find any mention about protecting non-power circuits in IEEE C62.41 (Recommended practice on surge voltages in LV AC power circuits).

Jules