Normal Daily Voltage Variations

Some causes of supply voltage variations

Time of day and national demand… A country’s or region’s demand for electricity varies throughout the day, it even varies with the weather; sudden cloud cover can mean that lights get turned on either manually or automatically.  As demand increases both voltage and frequency can drop, as more energy is demanded from the prime movers, the turbines. Power companies have a good knowledge of their daily/weekly demand cycle (which tends to be quite predictable) and so cope well with this varying demand. Increased renewable generation can affect the stability of the voltage supply, a sudden dip in windspeed or solar energy can cause problems if the spinning reserves are not sufficient to cover the drop. National voltages tend to be higher at night and lower during the day. UK peak demand is from about 16.00 to 20.00 daily.

Voltage variations can also be self-inflicted, this is where generally a user is demanding current close to or over their supplied capacity. Power companies are obliged by law to be able to supply you with sufficient current at the specified voltage and frequency up to your rated capacity. As you approach or exceed your rating, this may cause a local voltage drop, particularly if the supply system in the local area is heavily loaded; we tend to want electricity when everyone else wants it! Of course, the converse is also true, if you have PV and wind energy in your neighbourhood, then voltage can rise suddenly when the sun comes out or the wind pick up. High voltage can be more damaging than low.

The Electrocorder range of voltage and power loggers are extensively used to diagnose voltage problems.

If you suffer from low voltages, what can you do to help,… without being radical?

Where possible never use electrical machines between the hours of 16.00 and 20.00, instead use them at night or earlier in the day.
Install LED lighting.
Buy fleeces for staff and turn the heating down a degree.
Start at 07.00 and close at 16.00.