ARC FLASH

[bure961]

After a arc flash study has been completed to the main switchgear in a plant where the switchgear has not had any pm attention in years . The absents of pm'ing this switchgear can change its circuit breakers opening time. So what does this do to the breakers that are feed from the switchgear ? Does the lack of pm to the switchgear affect the performance of the down stream circuit breakers ? Thanks for the replys

 

[GoldDigger]

After a arc flash study has been completed to the main switchgear in a plant where the switchgear has not had any pm attention in years . The absents of pm'ing this switchgear can change its circuit breakers opening time. So what does this do to the breakers that are feed from the switchgear ? Does the lack of pm to the switchgear affect the performance of the down stream circuit breakers ? Thanks for the replys

It could, if the downstream studies relied on energy limitation by the main switchgear.
It should not affect the performance of the downstream breakers themselves under any particular set of input conditions, but it could affect what they are required to withstand, allowing them to to fail more violently while opening in the face of a downstream fault.
And it certainly could change the upper incident energy available when racking and operating those breakers.

 

[zog]

Maintenence of your breakers is a vital part of your safety program, the arc flash study ASSUMES the breakers will operate within thier designed clearing times per OEM TCC's. A 2007 IEEE paper addressing the reliability and integrity of low voltage overcurrent protective devices reviewed various surveys. It was found that nearly one?third of all circuit breakers failed while in service and thus would not have been identified unless proper maintenance was performed. In addition, 16% of all circuit breakers failed or were damaged while opening.

70E artice 130.5 says:
The arc flash hazard analysis shall take into consideration the design of the overcurrent protective device and its opening time, including its condition of maintenance.

Informational Note No. 1: Improper or inadequate maintenance can result in increased opening time of the overcurrent protective device, thus increasing the incident energy.

205.3 General Maintenance Requirements. Overcurrent protective devices shall be maintained in accordance with the manufacturers? instructions or industry consensus standards. Maintenance, tests, and inspections shall be documented.