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CT1 and CT2

lyledunn

The connection of SPDs using CT1 appears to provide protection only in common mode. That seems be the normal method employed. However, looking at CT2 am I correct in assuming that the clamp voltage would need to be very much less as the protection is provided across the conductors supplying load components? It seems to me that CT1 is for lightning and CT2 more for overvoltages derived from switching???

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    The reason I ask about the series arrangement

    Just to add into the mix that both CT1 and CT2 have a series arrangement - where you might get 2kV instead of 1kV between L & PE with CT2 you could equally get 2kV instead of 1kV between L & N with CT1.  In terms of equipment connected between L & N only - CT2 might actually be better. For Class 1 equipment, something's going to get stressed anyway - either live conductors to chassis or between live conductors. There's insulation and often components between both.

    I think the N-PE SPD in CT2 arrangements is usually different technology (spark gap rather than MOV perhaps?) - which may have an effect on relative clamping voltages (maybe someone with more knowledge than me could illuminate).

       - Andy.

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  • 0

    The reason I ask about the series arrangement

    Just to add into the mix that both CT1 and CT2 have a series arrangement - where you might get 2kV instead of 1kV between L & PE with CT2 you could equally get 2kV instead of 1kV between L & N with CT1.  In terms of equipment connected between L & N only - CT2 might actually be better. For Class 1 equipment, something's going to get stressed anyway - either live conductors to chassis or between live conductors. There's insulation and often components between both.

    I think the N-PE SPD in CT2 arrangements is usually different technology (spark gap rather than MOV perhaps?) - which may have an effect on relative clamping voltages (maybe someone with more knowledge than me could illuminate).

       - Andy.

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