Servo-controlled voltage stabilizer

[sinhchoo]

We are facing a voltage drop problem at our load side fed by a long overhead low voltage cable from kilometers away. Currently, we are having a booster transformer installed at the source end of the line but during peak period, voltage at the load side can go as low as 335V (required voltage is 415V). Can I install a Servo-controlled voltage stabilizer at the load end of the line while keeping the booster transformer at the source end? If the booster transformer is taken out, the line voltage of less than 300V is too far off the input voltage range of the servo-controlled voltage stabilizer.

 

[Skogsgurra]

When the feeder is as weak as it seems to be, there is a risk that your stabilizer will 'self-quench'. That is, when the load goes up and the voltage on your side goes down, the stabilizer will move its brush up on the winding and cause even more current to be drawn. That will, at some point, result in such a large drop that the voltage collapses completely.

It will be fairly easy to calculate the risk (e-pete?) given the line impedance and loads expected.

There is another aspect, also. If your load changes are rapid, a servo stabilizer may have a problem compensating for the fast voltage drops. Making it faster will usually result in unstable operation. Self-oscillation.

But, apart from that, it will work.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[sinhchoo]

Skoqsqurra, thanks for your reply. This line is supplying to a housing complex. We are looking into locally available unit of 200kVA with a input voltage of 415V +/-20%. Therefore without the booster transformer, the "self-quench" scenario will most probably occur.

 

[waross]

I would seriously look at raising the voltage up to a medium voltage and then dropping it back down at the load end.
Replace the booster transformer with a step-up transformer to 6kV or more. Then instead of buying a regulator buy a step down transformer.
If you have 415V dropping to 300V then by simple arithmetic almost 29% of your voltage drop is in the supply line. Depending on the power factor of the load and the line impedance characteristics you may be losing almost 1/3 of your energy in line losses.
I know that it is not always possible to do the job the "best" way.
If you go with the regulator, I suggest setting the booster at +20%. That will avoid the voltage to the regulator going over the +20% rating of the regulator during periods of light load or no load. The regulator will be able to protect the loads against over-voltages and you will have a 40% adjustment range from +20% to -20%.
Feeding a housing complex the load changes due to diversity will probably be within the acceptable operating range of the regulator

Bill
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"Why not the best?"
Jimmy Carter

 

[sinhchoo]

Waross, thanks for your advice.