Volt-VAr Volt-Watt? Watt are they talking about?

Tuesday, February 4, 2020
Industry

We've had a lot of questions from clients recently regarding what Volt-Var is and how it will impact their projects, so we thought we would attempt to clear up some of the confusion!

Once upon a time engineers only had to worry about the network being a one-way street. They were initially concerned with Loads, in other words, things that consume power. These loads caused the voltage at the street to drop. 

However, as with most things, things change and so too must the network. With the advent of solar and the countless systems installed, past-present-&-future, it is forcing engineers to deal with new unprecedented problems. The key one being voltage rise, which is the opposite to voltage drop due to loads. 

A generator, such as a solar system pushes excess energy into the grid, the voltage, or pressure, increases. If there is too much pressure in the network we will quickly have issues running most electrical appliances and devices.

Up until this point, the electricity distributors that operate and own the poles and wires, have been counteracting this issue by tapping down transformers. Typically a transformer which converts the high voltage (HV)  lines in the street to low voltage (LV) usable power in the home or business, can be adjusted depending on where the consumer or prosumer is located in the network. This is done to ensure the consumer is delivered with power that falls inside the regulatory requirements. And tapping up or down is one method of ensuring this.

This will only get us so far though. Some distributors in recent years have been forced to stop energy being put back into the grid by solar systems, aka export limit. The export limit is one way of ensuring the energy produced by the solar system is only consumed on-site and will not be exported to the grid. This negates voltage rise issues but is by no means the best mechanism as the excess energy produced by the solar system should be used elsewhere.

So, if we can’t tap down the transformer any more, and if the export limit isn’t really a solution because it increases the payback period, watt are we going to do? Introducing Volt-VAr and Volt-Watt response modes. Now we’re talking. 

For some time inverters have had settings buried deep in the user interface that us in the industry ignored, probably because we had enough to worry about. But now the distributors are requesting these be programmed to their specific settings.

Without getting into too much technical jargon, Volt-VAr regulates reactive power to manage voltage and offsets the impact of solar generation on the grid. While Volt-Watt reduces real power output to avoid nuisance tripping of the solar PV system when the grid voltage is high.

Doing this makes the network dynamic as opposed to a one-way street, where power is delivered by the regulators and consumed by businesses and homes. With these response modes being programmed at the inverter level means depending on the line conditions, perhaps in summer in the middle of the day. The inverters will react to the high line voltages due to higher impedance in the network and have the capacity to shift the type of power they produce to counteract the network conditions, or ultimately decrease their power output if things get out of hand.

What does this mean for you?

As of the 1st of November 2019, all new applications for listing an inverter on the CEC Approved Product List must demonstrate they have Volt-Watt and Volt-VAr capability. Also By the 1st of May 2020, all inverters currently on the CEC Approved Products List must be able to demonstrate Volt-Watt and Volt-VAr capabilities or they will be delisted.

This is good news in some respect because it means the network will be more intelligent and it will future proof the network for the next 5 years or so. We know, we did say only ‘5 years.’ But look, you can blame the original engineers for not being able to see into the future.

If you would like assistance ensuring your new commercial system meets these new regulatory requirements and that the inverters are programmed correctly, check out our injection testing services and get in touch!


Solar Industry Services