Voltage Drop

What is the specified tolerance on the voltage of the LV side of the transformer at the customer's incoming terminals, please?

Is the voltage at the transformer 433 volts? Is the 200 volts you mentioned phase to neutral? What should it be? What is the phase to phase voltage at the end of the cable?

1. What is rating of ur installed Transformer (KVA)?

2. What is the Phase to phase voltage on LV side of thranformer ends on running load of Area -1 & Area- 2. ?

3.What is the the phase top phase voltage on second ends of the cables (Load Area End) ?

4. What is the running load & PF of cables Area-2 ?

5. What is the ambient and cable temperature on operation time ?

Sir,

The transformer is 630 kva, voltage near transformer is 415 volt phase to phase and 350 volt , phase to phase near second feeder end.

Measure the voltage drops across any terminations. Something is resistive.

Do you have an IR camera?

Is it the same on every phase?

Is the phase loading balanced (same current on each)?

Have you checked the batteries in your Infrared camera yet?

Capacitor bank is for PF correction.

What sort of loads do you have?

You are a bit stingy with collected data mate. You need to share it (if you actually have it) in order for anyone to make a proper recommendation.

Aluminium conductors, hmmm....., who supervised the termination of these?

Dear Mr. Santosh

We will calculate the voltage drop in volt as well as voltage drop in % which is more meaning full. We need some confirmations & some more clarification which are as follows:

A. Conformation

1. Transformer is rated KVA is 630

2. Transformer Primary Voltage is 22000V or 22KV & 3-Phase

3. Secondary Voltage is rated 433V & 3-Phase

4. There is no meaning for 0.92P.F. for transformer

5. Second cable which is 2* 3.5 c * 300 sq. mm cable, is Al. OR Cu

B. Clarifications

1. Read on transformer name plate what is the % Z or percent impedance

2. Tell us each load serving P.F. otherwise we will take general value as 0.85P.F.

3. Your mentioned Voltage 200 is Phase to neutral

4. All cables are rated to 433V or 600V

5. Unless you know the Power factor of the second load do not try to think of connecting the capacitor bank. Capacitor bank for P.F. Improvement but not for Voltage drop improvement

6. Your calculated voltage drop of 10V is Phase to Phase or Phase to Neutral

Dear Sir,

Transformer is 630 KVA , 22KV/.433 KV, delta / star connected.

second cable is aluminium, 1100 volt rated.

I have taken p.f on transformer side. we dont have pf meter on load side in second case so can not measure.

0.92 pf is showing in MSEDCL meter.

200 is phase to neutral voltage.

Regards,

santosh.

At 415V p-p, you will expect ~240V P-N

if 10% drop is accepted, then you should aim at 216V P-N

If at the transformer you are getting 415V P-P, you should aim at 216V P-N at the end of the 560m.

Having 200V means that your drop is about 15% (High!).

For a 300kVA load, the maximum current will be ~ 418A at P.F.=1

If your P.F. is 0.8, to get a 300kVA loading will draw 522A

If your P.F. is 0.7, to draw 300 kVA loading will draw 597A

Therefore, Depending on the load and P.F. of the load, you can easily exceed the current drawn on these cables.

What is missing from your info:

Check the No-Load voltage at the end, then the normal load voltage you are getting, by measurement.

Also, measure the current at that load.

these will give you your real voltage drop and you can estimate the % drop.

If the Load is supplied through a Watt meter and a VAR meter (kWatt and KVAR or even KVA), these will help you calculate the P.F. without a meter. All digital power meters have the facility to give you the P.F.

there are many cable size callculators available on the net (or Cable sizing tables with Voltage drop rates...) to help working out the size required, provided you get the required values to input.

Normally, Capacitor bank is not used for voltage boosting purpose; it is being used for improvement of Power Factor.As for solution of your problem, please check the cable terminations to detec loose connections,bad crimping of cable lugs etc. which may increase the contact resistance, the effect of which may be voltage drop along with abnormal heating of terminations and subsequent failures.Also please check the voltage regulation of the above transformer.You have not mentioned the type of load;many things depends on the type of load; for example,if the harmonics content are high (THD & THVD), additional currents may flow due to the harmonics.

Thanks,,

Manindra.

That voltage drop is doing work somewhere.

Do you have a non-contact thermometer?

Read.

Digest.

Get on with it!

The voltage drop in 2 parallel cables is 6.67% at P.F= 0.8, and corresponding voltage at load end is 404.1/233.3V.

If 3 cables are connected in parallel, then voltage drop will improve from 6.67% to 4.45% OR 404.1/233.3 to 413.7/238.8V

It is also required to chech the voltage at transformer teminal when both the full loads are connected.

If the Translformer with Z% of 7.5 or 7.5 per unit, at 650Amps, it shall not be dropped in transformer more than 18.75Volts phase to neutral.