Voltage Drop Calculation for MV cable

[dltee]

Will someone be able to show me how to calculate voltage drop on the medium voltage cable (i.e 11 miles of 350 Kcmil 15 KV EPR cable with 133% insulation to support 150A Load at 13,200 volt)? There are plenty of calculations available for low voltage system.

 

[rbulsara]

Basic method is no different. It is still I/Z. Cable manufacture should be able to provide you with the reactance and resistance values of the cable and use those values. VD=I(R+jX). Use per phase values. I is the line current, VD will be L-N, regardless of the system configuration.

If you have a software, use that.

 

[rbulsara]

See this. I hate to do this normally (to pick a site and post it here, but this was just easy..)

http://www.okonite.com/engineering/voltage-regulation.html

 

[dpc]

For 11 miles of 15 kV cable, you may want to also consider the capacitive reactance of the cable and resulting charging current. This is generally neglected in low voltage calculations, but could be of interest in 11 miles of cable. For 150A of load (what pf?), the charging current may not be too critical, but becomes more important as the cable gets longer and longer.

You would need a cable model that includes appropriate shunt capacitance in addition to the series inductance and resistance.

 

[cuky2000]

See the enclose sample

http://cuky2000.250free.com/VD.pdf

 

[ArtAllm]

To get precise values of voltage drop you have also to take into consideration the ground temperature, which has an influence on the cable resistance.

http://www.allmend.net