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Electrical Riddle No.51 - Illumination for security purposes
Which is the best kind of lamp recommended for illuminating security fence and adjoining areas?.
When power returns after a power failure which kind of lamp out of Sodium vapour,Mercury vapour,Metal halide,Induction lamp etc will reignite quicker than other types?. What are the other considerations required to select a lamp for security fences or areas?.
Author : Sinnadurai Sripadmanaban - From: Srilanka
Mon, March 28th, 2011 - 00:53
In planning a security lighting system, the following must be considered:

- Cost of replacing lamps and cleaning fixtures, as well as the cost of providing the required equipment (such as ladders and mechanical buckets) to perform this maintenance.
- Provision of manual-override capability during a blackout, including photoelectric controls.
These controls may be desirable in a peacetime situation but undesirable when a mandatory blackout is a possibility.
- Effects of local weather conditions on lighting systems.
- Fluctuating or erratic voltages in the primary power source.
- Grounding requirements.
- Provisions for rapid lamp replacement.
- Lamp compatibility with the luminaire.
- Use of lighting to support a CCTV system.
- Lighting requirements for adjoining properties and activities.
- Strike or warm-up time of the lamp (the time required before the light will function properly when first turned on). See table below, for warm-up times.
- Restrike time of the lamp (the time required before the light will function properly after a brief power interruption).
- Color accuracy.
- Other facilities requiring lighting, such as parking areas.

Fenced perimeters require the lighting specifications indicated in UFC 4-020-02. Specific lighting requirements are based on whether the perimeter is isolated, semi-isolated, or non isolated (see figure below).
- Isolated fenced perimeters are fence lines around areas where the fence is 100 feet or more from buildings or operating areas. The approach area is clear of obstruction for 100 or more feet outside of the fence. Other personnel do not use the area. Use glare projection for these perimeters, and keep patrol routes unlit.
- Semi-isolated fenced perimeters are fence lines where approach areas are clear of obstruction for 60 to 100 feet outside of the fence. The general public or installation personnel seldom have reason to be in the area. Use controlled lighting for these perimeters and keep patrol routes in relative darkness.
- Non isolated fenced perimeters are fence lines immediately adjacent to operating areas. These areas may be in an installation or public thoroughfares. Outsiders or installation personnel may move about freely in this approach area. The width of the lighted strip depends on the clear zones inside and outside the fence. Use controlled lighting for these perimeters. It may not be practical to keep the patrol area dark.

Author : Hamid - From: Iran
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