Need Help Between Two Circuiting Options for a Street Lighting Feeder Pillar

There are advantages and disadvantages with both methods:-

Option 1 :-

Pros - 1. Less mechanicals to go wrong.

Cons - 1. Depending on lighting load, the contactors could be quite large and expensive although your mention of a 40 amp contactor suggests a fairly small setup. 2. A contactor failure could result in large areas with no lighting at all.

Option 2:-

Pros - 1. Smaller contactors will be cheaper each unit and thus cheaper to replace upon failure. 2. Multiple contactors reduce blackout area if a contactor fails.

Cons - 1. More mechanicals to fail. 2. More space needed for placement of contactors.

Another option to consider:-

Main feed to all lights. Separate controller at each light standard - something like the Philips Starsense or GE lightgrid controls. Utilise a Lonworks powerline protocol to tell each of those controllers whether they should be on or off during failure modes. Most of these protocols include repeater technology that enables long range communication. You could have luminaires with 2 lamps, one of which is isolated during failure thus providing more even lighting at those times.

Pros:- 1. less cabling - only one feeder for both essential and non-essential lighting. 2. Less space requirement for contactors and busbars. 3. No mechanicals to fail. 4. Easier servicing.

Cons:- 1. Possibly higher capital cost for controllers and signalers.

There is a third option:

Purchase lighting fixtures with individual day/night photocell control.

Divide the circuits up to meet the area lighting requirements. (Example: Every third fixture fed from the emergency lighting supply (standard) or for 50% availability it would be every other lighting fixture. )

Install a transfer switch at the emergency lighting distribution panel that allows normal system power to be applied to all lighting circuits until there is a loss of power at which point the transfer switch switches the designated emergency lighting circuits over to the backup generator once it has started and reached stable speed.

This option keeps the quantity of lighting loss from a component failure down to a minimum.