Unbalance Current

1. Unbalanced single phase loads for example lights on a three phase system or open circuit in one of the phase leading to a three phase load.

2. Single phasing of a three phase load for example motor will cause the motor to burn, uneven distribution of lights on a three phase system will cause increase in electricity bill.

3. Some relays for example Differential are very sensitive and inadvertent tripping could happen. EF relay is not associated with unbalance.

1. There are many reasons that cause the unbalance current in a three phase power system. To list a few:

a) Unequal Distribution and/or utilisation of Single Phase Loads

b) Voltage Unbalance

c) Harmonics

d) Inter-turn short in the windings of transformers/motors/generators, etc.

f) Double-Line or Double-Line-to-Earth Short Circuit fault

There could be many more.

2. Unbalance causes great damage in rotating machines, as it causes negative sequence currents and negative sequence torques in rotating machines; I have seen total rotor damage in motors due to unbalance currents. Even in other static equiment like transformers, it would cause additional heating in core, windings, etc.

3. If your relays are sensitive tto unalance, then there could be spurious tripping. If your relays are insensitive to unbalance. like an electro-mechanical relay, then you may not even know that there had been an unbalance (till it is revealed by an equipment damage)

And, yes! earth fault & unbalance are very closely related. Any single-line-to erath fault or a double-line-to-earth fault would very definitely cause unbalance in the system.

What happened to e

What you mean?

to prevent the unbalance. you can eliminate harmonics from system by putting more the filters into system.second, you must distribute equal power between single phase on morning, afternoon, evening, especially is the lighting loads, then you can use sensitive relay with unbalance, so you can regconise the faults about unbalance. so on.....

Unbalance current cause by unbalance distribution of load, this will draw current in neutral, increasing amp in neutral will cause heat on power supply. Yes, it has related with earth fault, if unbalance load happened and earthing resistance is high, it will cause earth fault.

loadshare: You not convince me yet.

Codswallop!