How to prevent voltage sag

Power Quality Analysis Equipment

When it comes to issues with power, most facility owners are most concerned about the potential havoc that can be wreaked by power outages. But it is not only losing power completely that can cause enormous problems for businesses and operations – voltage sags can seriously affect the running of systems. They are also typically far more common than outages and you might not even be aware that they are causing damage.

Voltage sags can be especially problematic for modern equipment that has a relatively high power usage such as process controllers, industrial computers and robots. Here we take a look at voltage sags and what you can do to avoid them.

What is a voltage sag?

Voltage sags are very common power events. They are defined by the IEEE as a short-duration reduction in voltage magnitude. For up to a few seconds, power quality is reduced before it returns to the normal level. The level of voltage reduction can be between 10% and 90% of the normal voltage.

They are the opposite of a voltage swell (where voltage temporarily increases) and separate from a voltage interruption (where voltage is lost completely), but they can still have severe consequences for your system.

What causes them?

The majority of voltage sag events are blamed on electricity providers, and these sags can occur for a huge variety of reasons that may not be immediately obvious. Simple human error during switching operations can cause sags, but also events that are impossible to track such as heavy wind, trees falling on power lines and even animals interfering with cables can cause sags.

Of course, there is little you can do about these sorts of events. But it is also worth remembering that sometimes the sags are as a result of equipment within your facility.

How to detect sags

If you are concerned about voltage sags within your system, undoubtedly the first step you need to take is to get an understanding of the quality of the power that is coming into your system. Invest in a power quality monitor which can capture power information and transfer it to a computer to allow you to analyse any issues. This can provide you with the information you need to take steps to prevent future sags.

Steps you need to take

If voltage sag is causing problems with your equipment then it may be necessary to take steps to protect your facility. Power line conditioning technologies such as uninterruptable power supplies (UPS) can be extremely useful. These protect sensitive equipment from momentary losses by sensing voltage sags and transferring the power supply to a battery.

At Outram we are experts in power quality monitoring – if you are worried about your power quality and are having issues with sags, our specialist equipment can help you understand the problem. Please contact us today if you require any further information or advice on which power quality monitor would be best for you.