The greatest cause of equipment damage from a power outage may be unavoidable electrical surges when power is restored. Although steps can be taken to protect equipment from surges, few businesses implement such measures.
Surge protection devices (SPDs) installed on a building's incoming electrical service can reduce potential damage caused by most externally generated surges, such as lightning or utility operations. Further protection is achieved if SPDs also are installed on distribution panels supplying critical or sensitive loads, and at specific equipment. This SPD layering throughout a facility — known as a zone of protection — is the most effective way to protect your facility against surges.
Most large commercial and industrial customers take our three-phase service, which provides greater capacity and an ability to use larger motors.
When a phase is lost, equipment may be damaged and downtime can result. While single phasing is not common, we recommend that you use loss-of-phase protection that senses single phasing. You can protect equipment from single phasing by using fuses, thermal trip devices, balance relays or electronic controls. These devices can be added at your main panel board or individual equipment. For more information, see the National Electrical Code Article 430, as published by the National Fire Protection Association, Inc.
What to do following an outage depends upon planning. Develop a well-written, easily understood procedure, which includes updated one-line diagrams and keep them in a central location with related documentation. Also develop a list of emergency generators and the loads to which they will be connected. A step-by-step procedure on how to connect each portable generator saves time and stress when an outage occurs.
Your procedures also should include disconnecting or turning off loads even though they are not running when the power is out. This limits the equipment exposed to the surge when the power is restored. Start by simply turning electrical equipment OFF. Depending on your system configuration, you may need to open circuit breaker switches to isolate equipment. When power is restored, close circuit breakers and disconnect switches closest to the supply source first.
The next step is to close circuit breakers or turn on switches one at a time, working toward the load, until all of equipment is energized and power restored. This procedure also should be followed when connecting portable emergency generators to critical loads. Make sure the circuit breakers and the disconnect switches in the circuit are open before the generator is started. Then, slowly close one breaker or switch at a time, working from the source (generator) to the load (equipment).
Careful planning is key to successfully reducing risk to your facility caused by power interruption. Take steps today to protect your facility and your residents from a power interruption's adverse effects.