VESDA system installed to monitor the air inside switchgear and MCCs?

[majesus]

Anyone ever install a Vesda system to monitor the air within sections of a 4kV Switchgear & 600V MCC?

Vesda is an aspirating detector that monitors the air for smoke to provide the earliest warning of a potential fire. We shall install this system in our electrical rooms. However, our client wants us to air sample inside the MCCs and switchgear by installing Vesda capillary piping into each section. We have one MCC that is eighteen sections long. Going to be interesting.

I anticipate switchgear failing immediately if there is a problem. Intermittent smoke that eventually escalates to a fire, is that how switchgear typical fails? I'm curious to know if a sampling air inside MCCs and switchgear is worth the effort and cost to install the capillary piping.

 

[rcw retired EE]

Our client's insurance company wanted a CO2 discharge head and detector in every MCC and switchgear compartment and space, 7.2 kV, and 600V. After a lot of discussion we finally went to the sniffer approach with sensing tubing in each vertical section.

A single detector with a pneumatic multiplexor sampled each section in sequence. (Don't remember the frequency, every 10 mintues?) The sniffer was supposed to detect combustion products prior to flames appearing. The demo worked great, alarming when the paper was charred brown but had not yet ignited.

After six months work and adjustments false alarms dropped to about one a week. Alarms did not appear to be related to breaker operation, motor starting. overloads or other electrical operations. The fie alarm contractor kept blaming dust. The electrical rooms were large but had full HVAC with positive pressure to keep out dust.

I'll never use it again.

 

[Miguel Villarroel]

must have been the ozone that activated

If there was no electricity there would be no internet. Good point, don´t you?

 

[FreddyNurk]

I've heard about arc flash detection within switchgear cubicles to detect any arcing so that the board can be isolated (admittedly not very much though), but surely with requirements for type tested assemblies, putting VESDA gear inside it would breach the type test conditions?

I'd imagine that an internal fault, depending on the type of switchgear or MCC installed, would generate enough smoke and other byproducts to set off the VESDA within the switchroom regardless.

Setting a VESDA system up inside an arc tunnel might be an idea, though how effective it would be and how many false positives you'd get I'd not want to speculate on.

 

[alehman]

Traditional VESDA is an optical obscuration sensor, so whatever was setting it off had to be particulate in nature. Ozone would not. We commonly install it in electrical equipment rooms, but not in the actual equipment. I've never heard of that requirement.

Alan
“The engineer's first problem in any design situation is to discover what the problem really is.” Unk.

 

[jraef]

Switchgear, probably OK, but MCCs? I wouldn't. Every time a contactor opens, and to a lesser extent closes, there is an arc that jumps across the contacts, vaporizing a minute amount of contact material every time, along with some carbon from airborne dust and contaminants. Depending on how sensitive the equipment is, that may give you no end of headaches from false alarms.

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