I have a 400VAC generator here that will be used on an offshore platform, 4 wires out (1,2,3,N). There is a toroid type earth leakage relay on it inside the generator main breaker enclosure with all 3 phases and neutral running through it. My understanding is that the toroid will sense any unbalance between the currents travelling on all 4 wires. In any normal situation, any current travelling out of the gen will also be travelling back in, whether it be on another phase or on the neutral. So the net sum of current travelling on all lines should always be 0 at the breaker panel.
This all makes sense to me, but here is the confusing part: The neutral and frame of the generator are not bonded. Which means that even in the event of a line to frame fault, there will not be any fault detected, as there is no path for the fault current to travel back to the star point of the gen. Which makes me wonder, what’s the point of the earth leakage relay? Where can any stray current possibly “leak” to?
Even if they are relying on neutral to ground bonding to take place in a main distribution panel in the field, that still means that a line to frame fault on the generator would not cause an imbalance on the ELR, as fault current would still be returning on the neutral wire to the start point.
Is there a gap in my knowledge somewhere? I cant see how the ELR can do anything, unless current from the generator actually “leaks” out of the electrical system completely…..to where??
Sorry if it's a noob question, this is my first time dealing with the thing...
This all makes sense to me, but here is the confusing part: The neutral and frame of the generator are not bonded. Which means that even in the event of a line to frame fault, there will not be any fault detected, as there is no path for the fault current to travel back to the star point of the gen. Which makes me wonder, what’s the point of the earth leakage relay? Where can any stray current possibly “leak” to?
Even if they are relying on neutral to ground bonding to take place in a main distribution panel in the field, that still means that a line to frame fault on the generator would not cause an imbalance on the ELR, as fault current would still be returning on the neutral wire to the start point.
Is there a gap in my knowledge somewhere? I cant see how the ELR can do anything, unless current from the generator actually “leaks” out of the electrical system completely…..to where??
Sorry if it's a noob question, this is my first time dealing with the thing...
