Question: 

Do “Non-cycling” HPS lamps protect the lighting system?

Answer:

There is some confusion in the market concerning “Cycling”.

Typically, “Cycling” is a term used to describe an HID lamp near end of life that “Cycles on and off” every minute or so due to uncontrollable voltage rise in the lamp.

Some manufacturers advertise “Non-cycling” lamps that will not “Cycle” on and off near the end of life. The manufacturers suggest that when the lamp light turns from Yellow to White, the white color is an indicator that the lamp is near end of life and should be changed. So protection of the lighting system is contingent upon the maintenance crew changing the lamp shortly after failure. 

The “Non-cycling” lamp can not control a fixture ignitor so it does not provide “fail-safe” protection for the system.

Once an HPS lamp fails to start, the fixture ignitor will “pulse” continuously all night long every night until the failed lamp is replaced. The continuous high voltage pulsing of the fixture ignitor eventually deteriorates the insulation on the ballast windings resulting in a short that causes the ballast to fail completely, or damages the ballast to the point that that new lamps installed in that fixture will fail prematurely. A damaged ballast can result in a numerous additional trips to that pole for re-lamping.

Ignitron lamps (More than 93% non-cycling at the end of life) have a built in ignitor whose starting pulse is greatly diminished, or completely stopped when the lamp fails. There is little, or no pulse to damage the ballast, which results in  “fail-safe” protection for the ballast, because it is not dependent on the lamp being replaced in a timely manner.