Conservation Voltage Reduction

[kev21903]

Conservation Voltage Reduction (CVR) basically is lowering substation voltages to save energy. There are many papers in existence to demonstrate the principle and report on successes and limitations of the various techniques.

 

My question is:-

 

How is the energy being saved?

 

I do understand where some of the energy is being saved but I don't want to lead this forum down a specific route. I would like to open this up for debate......

 

Any ideas and suggestions or hunches are welcome.

 

Kevin

[Guest]

By lowering the voltage to the customer the customers energy consumption will be reduced. By reducing the energy consumption, energy is saved through reducing electric line losses and the lower voltage will reduce non-load losses in distribution transformers. In the end, the utility will experience a reduction is electric losses (less waste) and the customer will save by having a lower electric utility bill.

 

KC Fagen

R. W. Beck, Inc

kfagen (at) rwbeck (dot) com

[marke]

If you have a resistive load and you reduce the voltage across it, the power will be reduced because P = I x I x R. This basically applies to incandescent lamps and heaters.

 

If you reduce the voltage on induction motors, you will lower the flux in the iron and reduce the iron loss, however, in order to produce the same shaft power with reduced flux, the slip increases, (the rotor slows slightly) the work component of the stator current increases and the magnetising current reduces. There is a reduction in iron loss but in most cases an increase in copper loss so no real gain, and often a loss situation. If the motor is operatig at very light load, there can be a reduction in magnetising curent , iron loss and copper loss.

 

The reduction in line voltage will reduce the thermal work that is done, but not the rotational work. In domestic systems, the reduction in voltage can result in a reduced current. In industrial systems, the reduction in line voltage can result in an increase in current and copper losses.

 

Best regards,

[subhash]

Dear Marke

In our case we having @ 40 % plant load is Air Heaters and Balance load is lighting and Inductive load mostly motors Maximum motors we are running through inverters ( Veriable frequency Drives).Presently my LT side system voltage is 415V to 425V.So let me know that by lowering Plant voltage upto 400V may i get Energy saving and what it will affect on my motors which are not connected through Veriable feequency drive

and what happens if voltage reduced further up to 395V by lowering Tap of Transformer .

Regards

Subhash.

[kens]

You are not actually saving energy on resistive loads as the output is also reduced so it is only the current losses that are saved. If the heaters output is halved then it will simply take twice as long to achieve the end result. If we assume that any heaters are sized correctly to the process then the heaters lack of output could end up delaying the process which would cost more than the small savings in losses on the supply line.

Ken