Beyond the service entrance certain electrical and electronic equipment within the facility may require additional protection against internally generated surges and by lightning entering through grounds and conductors (other than the incoming power lines). The service entrance arrester may be too far away to protect this equipment and therefore “secondary” local protection becomes necessary. This protection consists of smaller SPD’s (suppressors and protectors are other names) mounted right at the equipment, at distribution panels, or at the wall receptacle.
The following information is useful for determining the proper protection:
Briefly describe the equipment requiring protection.
What is the voltage of operation? Is it AC, DC, RF, signal, data or other.
How many wires feed the equipment.
What are the actual voltage values wire to wire and each wire to neutral?
Any comments which may be useful.
Choosing a Surge Protective Device Application : At The Service Entrance
The service entrance SPD is the first line of defense against lightning and surges coming in on the power lines from the outside world. The service entrance is the location where the power company supplies electric power to the customer and where the neutral (if used) is earth-grounded. The following information is useful for determining the proper protection :
The following information is useful for determining the proper protection :
A) Is the service voltage single phase or three phase? B) What are the rated voltage values each line to line? What are the voltage values each line to neutral (or to center tap)? C) If a neutral does not exist, is a corner of a delta system grounded? D) What is the KVA (or ampere rating) of the incoming power? E) If the frequency is not 60 Hz (U.S.), please specify. F) Are lightning occurrences very severe in the area? G) Are man-made surges severe in the area? (These surges are caused by electrical operation of anyone’s equipment on the power company’s lines, including switching operations by the power company) H) Is the SPD to be installed indoors or outdoors? Will the atmosphere be corrosive or explosive? I) The SPD is provided with indicator lamps to show that it is functional. Are remote alarm relays desired for remotely monitoring the SPD? J) Are there any helpful comments to clarify the description of the power system, concerns about protection of special or unusual equipment, or any questions whatsoever on lightning and surge protection of electrical and electronic equipment?