Protecting Electronic Equipment from Power Surges

Power Disturbances / Power Quality

Today's electronics are more sensitive to power disturbances than ever before. Most electrical devices can tolerate short-term power disturbances without any noticeable effects. However, some equipment in your home or office can be affected including computers, digital clocks, answering machines, large screen televisions, DVD players, electronic cash registers, security systems, and heating and air conditioning systems.

We are proud of our reputation for providing a safe, reliable supply of electricity, but severe storms, lightning, high winds, power equipment failures, cars hitting utility poles, and even squirrels, raccoons or birds interfering with electrical equipment, can cause power line disturbances. For these reasons, it is impossible for any utility to maintain perfectly constant voltage 100 percent of the time. This is reflected in our Conditions of Service, Section 2.3 - Conveyance of Electricity.

Identify the Problem

Since power disturbances are almost always intermittent, they can be difficult to identity. You may need to call in a professional to help identify the type of power disturbance you are experiencing from the list below.

Safety first! Always have a licensed electrician check your wiring. To find a qualified electrician, please visit the Electrical Safety Authority website.

Momentary Outages

In most instances, contact with a power line only lasts a fraction of a second and our relay system automatically restarts the flow of electricity. Today a split-second loss of power is sometimes just enough to upset sensitive digital equipment. That's what causes microwaves, electric clocks, and VCRs to blink from time to time.

Symptom: Flashing/Blinking

Cause: Lightning, accidents involving poles and lines, tree limbs falling across power lines, stormy weather.

Protection: Built-in battery backup feature in the appliance will preserve clock, memory or programming.

Voltage Spikes

Spikes are very fast-moving periods of high voltage. A spike can be caused by lightning, large electrical equipment switching off near your home, or appliances such as air conditioners or furnaces switching off. Spikes cause electricity to rush through your wiring and can cause damage to unprotected equipment.

Symptom: Damage

Cause: Lightning, birds/animals on power lines, normal operation of large-load home.

Protection: Have a lightning arrester installed by a licensed electrical contractor. This will protect most major appliances that do not have digital displays. Use surge suppressors or other power protection equipment to protect sensitive electronic equipment.

Sag and Surge

Sometimes you may notice that your lights get dim and then bright for short periods of time. This is caused by voltage sags and surges. Sags and surges can occur during storms, or when large electrical loads such as air conditioners, refrigerators, and dishwashers turn on (sag) and off (surge). Often these appliances affect one another because the wires connecting them are not large enough to carry the proper electric load. Sags and surges stress appliance motors and circuits, microchips and motors in sensitive equipment causing them to wear out sooner than expected.

Symptom: Lights Dim / Get Bright

Cause: Operation of major home appliances, faulty wiring.

Protection: Call Guelph Hydro Electric Systems Inc. at 519-822-3017 and report the problem. If the problem isn't Guelph Hydro related, have an electrician check wiring and/or install surge protector for sags and surges. To find a qualified electrician, please visit the Electrical Safety Authority website.

Electrical Noise

You cannot only hear electrical noise but you may see it, for example, when someone turns on an electric motor (such as a blow dryer) while you are watching TV. The static and white lines on your set are audible and visual displays of electrical noise. Other causes of noise can include fluorescent lights, motorized appliances, radio transmitters and loose electrical connections. Noise is seldom damaging to most equipment, but it can be very annoying.

Symptom: Noise on Radio / TV

Cause: Small appliance motors, loose electrical connections

Protection: Use shielded cables for antenna connections. Do not use "noisy" equipment on the same circuit as the TV/radio. Purchase power protection devices with noise suppression. Have a licensed electrician check for loose connections. To find a qualified electrician, please visit the Electrical Safety Authority website.

How to Protect Sensitive Equipment

The following is provided for information purposes only. Guelph Hydro Electric Systems Inc. does not supply or install any of this equipment. Please consult with a local electrical expert if you have questions about these devices. To find a qualified electrician, please visit the Electrical Safety Authority website.

Dedicated Circuits
When a variety of equipment shares a circuit, voltage fluctuations may be caused by the equipment switching on and off. By putting more sensitive equipment on its own circuit, you reduce the wear and tear and help to ensure the quality of power to that equipment.
Surge Suppressor

A surge suppressor protects equipment from spikes and surges, which account for only 17 - 20 percent of all power disturbances. Note, however, that they will not protect equipment from the other 80 percent of power disturbances which can cause long-term or immediate damage.

The tips below will help you select a surge suppressor that will help protect your equipment.

  • A surge suppressor must protect your equipment from every connection to the outside world. If you have cable TV, the suppressor must protect incoming power as well as the cable line.
  • Most suppressors have limited energy handling capabilities for lightning and should be used in conjunction with a lightning arrester installed at your main power service entrance.
  • A plug-in surge suppressor should be UL-listed and have a number on it telling you how many volts it will let through to your equipment before it begins to operate. This number will be printed next to the UL label and be listed in kV or volts (kV or kilo-volts is equal to 1000 volts). Look for a number equal to or less than .5kV or 500 volts for a plug-in device.
  • Suppressors should also have electrical noise filtering. Look for EMI/RFI filtering information usually shown as a number. In general, the higher the number, the better the suppression.
  • After you have found a surge suppressor that meets your needs, you can further protect your equipment by plugging them into circuits that do not supply large electrical loads like refrigerators, freezers and air conditioners.
Line Conditioner
A line conditioner is designed to regulate and condition incoming voltage to within the safe limits of a piece of equipment. A line conditioner will protect your equipment from most sags and surges, but it will not protect your equipment during an outage.
Uninterruptible Power Source (UPS)

A UPS uses an internal power source (batteries) to power connected equipment during outages or when the line voltage goes below or exceeds limits set in the unit. UPS's usually have between 5 and 15 minutes of battery power, which will let you "work-through" short outages or give you enough time to turn your system off in an orderly manner without damage to the equipment or data.

When purchasing a line conditioner or UPS, remember to buy a product that is UL-listed and capable of handling the electrical load of the connected equipment. Also, make sure that the unit provides surge and noise suppression. If it does not, you will also need to purchase a surge suppressor.