what will happen if the sample installation got an excess current flow in the circuit like phase to phase contact

[admin]

Transformer capacity: 100KVA/13.8KV/231/133Y

Transformer LV overcurrent protection Device: 400 Amp,Ceramic knife blade fuse

Secondary Service LV cable size bet. xtfmr LV bushing and 400 amp fuse box(approx.6 Mtr).: 4×300 mm2,alum cbl.

Secondary Service LV cable size bet.. 400 amp fuse box and secondary service cndctr.(approx.10 Mtr.): 4x300mm2,alum cbl.

Secondary service LV cbl size bet.4×300 mm2 cbl and load.(Approx.150 mtr length,Direct joint ): 120mm2 alum cbl.

Secondary service LV cbl size bet.120mm2 and load: 70mm2,alum cbl.

Secondary overcurrent protection device bet.120mm2 cbl and load:150 Amp c.breaker.

If the cause is overheating due to overload what will happen to the cable (70 mm2) at the upstream side of 150 amp protective device?

[Spir Georges GHALI]

journeyman said:

Transformer capacity: 100KVA/13.8KV/231/133Y

Transformer LV overcurrent protection Device: 400 Amp,Ceramic knife blade fuse

Secondary Service LV cable size bet. xtfmr LV bushing and 400 amp fuse box(approx.6 Mtr).: 4×300 mm2,alum cbl.

Secondary Service LV cable size bet.. 400 amp fuse box and secondary service cndctr.(approx.10 Mtr.): 4x300mm2,alum cbl.

Secondary service LV cbl size bet.4×300 mm2 cbl and load.(Approx.150 mtr length,Direct joint ): 120mm2 alum cbl.

Secondary service LV cbl size bet.120mm2 and load: 70mm2,alum cbl.

Secondary overcurrent protection device bet.120mm2 cbl and load:150 Amp c.breaker.

If the cause is overheating due to overload what will happen to the cable (70 mm2) at the upstream side of 150 amp protective device?

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Dear ;

 

Excuse-me, but some things are not correct :

 

First :

You have a transformer ” 100 kVA ” with ” 231/133 V ” as output voltages, so, the nominal currant ” In ” for this transformer from LV side is :

– In : 100 x 10³ / 1.73 x 231 = 250 A

So, how this transformer is protected by ” Fuse : 400A ” ?

 

Second :

You mentioned to many outputs ” Cables' Sections  &  Fuses “, but you don't mentioned to the Loads' Powers !, because if the sum of the Fuses' currents is the total currents loads, this transformer will be certainly overloaded.

 

Third :

You defined for some outputs 2 cables' sections ” 300mm²  &  120 mm² ” , ” 120 mm²  &  70 mm² ” ?

 

Please clarify more precisely .

 

Regards.

[Author]

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