Power Quality FAQs

We have lots of helpful FAQs regarding the PUD.  Click on the categories on the left.  If you have any questions, please contact us.

Click on each question to link down to the answers.

1.  What does “power quality” mean?
2.  What is a power surge?
3.  What about low voltage?
4.  How is an interruption or power outage different?
5.  What is electrical “noise”?
6.  Is the PUD responsible if my equipment is damaged due to an outage or power surge?
7.  How can I protect my equipment?


1. What does “power quality” mean?

Power quality refers to the consistency of the electric voltage. Voltage outside the proper range can damage electrical equipment. Prior to the age of electronics, power was used to operate mostly motors and lights. Today, homes and businesses are filled with sophisticated and highly sensitive equipment such as computers, televisions, stereos, appliances and other equipment containing electronic microchips. These devices are extremely sensitive to the quality of power.

2. What is a power surge?

Spikes and/or surges are sudden increases in voltage that last less than 1/60th of a second. Large spikes can burn or melt electronic components causing instant failure. Repeated “hits” from small spikes gradually erode components and can shorten their useful life. Most spikes originate inside your home or business and are caused by other electric equipment such as when the compressor in your refrigerator kicks on, or when copy machines, laser printers and large motors are turned on and off. A smaller percentage of spikes originate outside your building, caused by lightening strikes, short circuits in electric lines and large equipment used in businesses. While these spikes are less frequent, they tend to be more serious. Lightning strikes to a telephone line, cable TV system or satellite dish also carry voltage spikes. Devices that are connected to more than one wire, such as cordless telephones, answering machines, computer modems and TV’s are especially vulnerable.

3. What about low voltage?

Low voltage is a decrease in voltage that affects electric motors when they don’t get the power they need to operate. This is the most common form of power quality problem. This dip in voltage usually lasts less than a second. Voltage drops longer than one second are called brownouts. When power returns, spikes often occur as equipment in the system springs back into action.

4. How is an interruption or power outage different?

A power interruption or outage is a total loss of power, which may last less than a second or up to several hours. You may not notice a split second interruption, but your computer might restart or your digital clock may start flashing.

5. What is electrical “noise”?

Electromagnetic Interference (EMI) commonly referred to as “noise” doesn’t cause much damage, but it can be a nuisance. You see electrical noise as ‘snow’ on the TV screen. Noise may also be heard as static on the radio and is referred to as Radio Frequency Interference (RFI).

6. Is the PUD responsible if my equipment is damaged due to an outage or power surge?

It depends on the circumstances. There are many things that can cause a power outage or interruption. It may be a normal system operation where equipment detects a fault and usually, the breakers will try three times to clear the line. If, after the third try or blink, the problem isn’t cleared, it will turn off the power. The equipment is operating as it was designed to do to prevent further damage to the system. Squirrels and birds cause many outages as do vehicles hitting power poles, lightning and storm (ice, wind and snow) damage. These are all out of our control and usually claims are denied. As a general rule of thumb, some claims are compensable if it can be determined the PUD was negligent in some way -- did we do something we shouldn’t’ have done, or didn’t do something we should have done; Because damage can come from within the home as well as outside, and because many times it is impossible to tell exactly what caused the damage, it is the customer’s responsibility to protect his equipment with properly rated surge protection devices. (Please refer to the information on Surge Protection to determine the appropriate rating needed for various equipment and appliances.) If you feel your equipment that has been damaged due to a power fluctuation, please contact the PUD office immediately following the event so we can try to determine what happened.

7. How can I protect my equipment?

Proper grounding of the electrical system is essential. If your home or business doesn’t have grounded, three-pronged outlets, the first step is to install them. It’s best to put sensitive equipment on its own dedicated circuit.

Fuses and circuit breakers protect building circuits from overheating and causing fires. However, damaging spikes and surges occur so quickly that they pass through circuit breakers. To catch spikes and surges before they damage your equipment, you need surge suppressors. Surge suppressors react within one billionth of a second (called a nanosecond) to divert the excess voltage to the building’s electrical ground. Good surge suppressors also filter line noise.

Plug in Protection – Most electronic equipment today needs the protection of plug-in surge suppressors. They are the simplest, least expensive and most effective way to prevent problems with electronic appliances. Surge suppressors are installed between the appliance and the wall outlet. Their job is to reduce the size of voltage surges to a safe level.

Surge suppressors will not stop digital clocks from blinking after a power interruption. Nor will they prevent loss of data from a computer system dueto an interruption or surge. They DO protect the equipment in most cases.

Uninterruptible Power Supplies or UPS provide a battery backup for computers. UPS devices insure power quality during sags and interruptions protecting both data and hardware. Most UPSs provide 10-16 minutes backup time, allowing you time to close files and exit programs. Most UPSs provide surge suppression as well. A UPS must be UL listed.

Retail outlets usually have a good selection of surge suppressors, and UPSs can be purchased at computer equipment stores. If the information on your computer is valuable, we strongly recommend it be UPS protected.


  • It is better to be safe than sorry and taking the time to purchase a properly rated surge suppressor when you purchase electronic equipment is money well spent.
  • More expensive is not always better. Read the fine print and select a surge suppressor that is rated to protect the equipment you are purchasing. If you have questions, call the PUD and we can help you determine what size is recommended.

Back to top >>