Undervoltage in Supply System Voltage

[nmaverick]

Hello All...this is my first post and straight away I start with my doubts,which are bothering me since long.
I reside in India, where the nominal Single Phase supply voltage is 240 volts 50 Hz. As per the National Grid Code, voltage variation in the range of +/- 6% is allowable. In another Code, the maximum and min. values of LT supply voltages are mentioned at 220 volts and 264 volts.We have 3 phase-4 wire O/H distribution system.

1.)Recently, I have been experiencing under voltages. As it is summer season,during night,as the loading on feeder is more, my voltage dips sometimes to around 205-215 Volts and remains at that value for a pretty long time.For some other times it does show values between 215-220 volts. But During Switching ON-OFF of someone else's Air Conditioner Unit on the same feeder, for a couple of seconds the voltage also dips to 180 Volts.Of course the obvious effects of this to be seen are is dimming of CFL/TFL and slowing of Fans. Is such an undervoltage normal?

2.)A couple of years back I also bought a LG 1.5 Tonne Air Conditioner.Its nominal voltage is 230 volts and running current is 8.5 Amps. What can be the starting current of such an Air Conditioner. Because of such voltage profile , I am afraid to start my Air Conditioner, as I fear Voltage to drop further and in turn increasing the current.I do have an O/C MCB protection for Air Conditioner,but I have yet not started to use my Air Conditioner for fear of reducing its Life or damaging it by operating at undervoltage. Kindly guide me on these concerns.

3.) What can be the permissible voltage drop between Neutral and Earth? During Daytime when my voltage is fairly above 220 volts, I get this voltage as 3 volts or below 3 volts. But sometimes during day time and most of the time during night,I get this voltage as 5-10 volts. I worry ,if this is due to Earthing problems from my end. But if that is the case, then I think it should not vary with time. Are problems 1 and 3 related?

What can be the probable solution to such problems?
Thanks in Advance. I m a newbie so pardon me for such a long post.

 

[UPS-for-Africa]

No Need really to worry if above 200 Volts AC 50 HZ,
Induction electric motors will have major issues starting at any voltage under this

As per your questions

1. If you are experiencing a major volt drop when a large motor like an air-con unit starts, your feeder cable is not of the correct thickness and will need to be replaced, or your step down transformer on that line is inadequate

2. 2 options here thicken cable from feed transformer, or wherever feed is coming from, alternatively you can add a constant voltage transformer to ensure line remains at 220 volts

3. With 3 phase in India the neutral is grounded to earth typically after the step down transfromer, so if you see the voltage fluctuating severely between neautral and earth it might indicate problems with how the neutral is grounded at your feed transformer.
Also the higher the load the higher the voltage difference will be between neutral and earth

If you elaborate a little more about your overhead 4 line supply and what feeds it, as well as cable thickness max A and distance to point of use I can explain in more detail for you.