Re: voltage drop

Spir Georges GHALI

@yudhi said:
Hi I am yudhi

I have problem with voltage drop ,
When the load at 3400 amp the voltage drop until 360 volt
I use 4000 kva step down transformer from 20 kv to 400 volt.
The cable is NYY 1x400mm , 8 cable for each phase at 400 volt
And 1x120mm at 20 kv, cos q is 0.9
Distance grom transformer to switchboard around 60 mtr

I dont know where the problem
I hope you guys can help me to solve this problem



Dear ;

First, by calculating the voltage drop of cables between the transformer and switchboard, I found that should be around “ 1% ”, noting that I assumed the arrangement of these cables is “ Trefoil ”, but let me know if the mentioned voltage drop “ ≈5% ” is only for this distance ? Or in a another place of network ?

If it’s only of this distance, you should do the following :

– Measure the output voltage of the secondary’s transformer at no-load.

– if it’s “ 400V ”, we should know the specifications of the transformer and the length of MV line to be able to calculate if this phenomena is caused by MV line.

– if the output voltage is smaller than “ 400V ”, the reasons are either the MV voltage is less “ 20kV ” (you should know this value), or the position of the “ Tap-off changer ” is not correct, in all cases, try to change this position to have around “ 400V ” or even just a little more.

– if this voltage drop is in another place of network, please let me the type, section, length, and arrangement ( if it’s Single Core ) of that cables to be able to calculate the voltage drop at that point.