Voltage Reduction Help

[Esurfer]

We have implemented voltage reduction in substation level,how ever we got couple of substations with down-line regulators.I was wondering whether there's away to remotely shut these down-line regulators while on voltage reduction.

I would like to hear how you guys accomplish this at your utilities.

Thank you and your help is much appreciated.

P.S: we got both TWACS and Cannon installed in our system.

 

[cranky108]

First we don't use voltage reduction. We had several problems when we did that years ago, inculding replacing several customer motors.

Voltage regulators can do voltage reduction just like LTC's can. You need the right control to do it.

 

[magoo2]

Presumably you need the downline regulators to deliver acceptable voltage to customers near the end of the circuit. You would have to see if remotely just shutting them off when you reduced voltage at the substation would result in acceptable voltage for customers beyond the line regulators.

What we do for our substation voltage control is provide a 3 V bias to station regulators and LTC. We switch in the bias voltage when we want to reduce voltage. The control sees the actual voltage (from PTs) plus the bias voltage as the presumed output voltage. This results in the regulating device changing taps to reduce voltage. There's no reason why it can't be used for the line regulators too instead of simply shutting them off.

 

[marks1080]

The regulators should tap up on their own.

Out of curiosity, what's going on that you need to do voltage reduction? What's the rated voltage of the main transmission section? What's the normal running voltage? What are the voltage levels when they get too high?

 

[magoo2]

We've used voltage reduction to reduce demand primarily during emergency conditions, for example, if you lose a major generating station during a heavy load condition or something like that. If you have a big mismatch between load and the available generation (including ties with neighboring utilities), the voltage reduction trick gives you an equivalent % demand reduction for each % voltage reduction. The 3 V example on a 120 V base gives us a 2.5% reduction. We'll go to as high as a 5% reduction in voltage before we have to resort to load cycling or interrupting.

Now we're finding lower voltage benefits customers because it reduces their energy usage so we are doing it more toward off-peak conditions too.

As far as the regulators "should tap on their own", they do but the voltage setting can be changed and they will tap on their own based on the new voltage setting.

 

[Esurfer]

Thank you for your responses.

cranky>> Yeah, voltage reduction has a negative impact on the induction motors.

magoo2>> We are actually using SEL voltage controls to accomplish 2.5% voltage reduction.We basically send a SCADA command to the regulator controls so that it would go into voltage reduction mode.The controls we have down-line are old and they are not capable of SCADA communication.

Mark>> That's exactly the problem,when we lower voltage at substation level,the down-line regulators will start stepping up.That's why we want to take them offline during voltage reduction.Our norminal voltage is 126.0V and when at voltage reduction it would be 123.0V.