Ive just run a calculation for a distribution board with the following inputs 1000KVA transformer @ 4.75% showing a fault current as 28.7KA EFLI at 0.0089. On this transformer there is a bolt on protection 125A Supply is via a 125A 3P fixed pattern ABB TMax MCCB type XT1N160R125 fitted with TMA thermal magnetic overcurrent protection, providing adjustable overcurrent (0.7 – 1 x In) and short circuit protection. (set at 0.8) = 100A The cable from this cable is to be a 25mm 4 core run on tray on it own for 5m before it terminates in a Distribution board. My problem is at the Main Panel the fault level is 28.7KA (from supply page), But my calc (short circuit fault summary) at the DB (only 5m away is coming out as 7,233A (b). I would expect it to be in the 20's range. Am i missing something I was expecting a fault level issue due to the proximity of the board to the supply? regards Ian S Langley

Hevacomp

Hevacomp Forum Fault Level at distribution board close to transformer

Fault Level at distribution board close to transformer

Offline Ian S Langley over 2 years ago

Ive just run a calculation for a distribution board with the following inputs

1000KVA transformer @ 4.75% showing a fault current as 28.7KA EFLI at 0.0089.

On this transformer there is a bolt on protection

125A Supply is via a 125A 3P fixed pattern ABB TMax MCCB type XT1N160R125 fitted with TMA thermal magnetic overcurrent protection, providing adjustable overcurrent (0.7 – 1 x In) and short circuit protection. (set at 0.8) = 100A

The cable from this cable is to be a 25mm 4 core run on tray on it own for 5m before it terminates in a Distribution board.

My problem is at the Main Panel the fault level is 28.7KA (from supply page), But my calc (short circuit fault summary) at the DB (only 5m away is coming out as 7,233A (b). I would expect it to be in the 20's range.

Am i missing something

I was expecting a fault level issue due to the proximity of the board to the supply?

regards

Ian S Langley