can anyone advise what would be best set up to use with a delta delta 690/480v transformer being used to supply two 15kw vsd with emc filter to ground . insulation metering versus imedance relay and ground monitoring , i take it ground monitoring equipment for a delta/star set up will not work with the former it system unless with impediance relay, or am i missing something ,this is for offshore situation . and a retro fit .
For ” IT ” system :
– If the transformer's secondary is with Neutral : the Neutral point can be either connected to the Earth point by ” Impedance ” or not connected ( completely opened ).
– If the transformer's secondary is without Neutral : one phase ( any one ) can
be either connected to the Earth point by ” Impedance ” or not
connected ( completely opened ).
– Some of ” Insulation Monitoring ” are internally equipped by ” Impedance “, so, we don't need it. Noting that we can know from the schematic diagram of intallation if we need an impedance or not.