how often is switchgear maintainance preformed?

[charlie tuna]

out of the many buildings we work for only a hand full do any type of switchgear maintainance. usually every seven years they hire us to oversee the manufacturer's service crew shutdown and clean and function all the components of a building's switchgear. they test all the set points. in many cases we find infrared problems in big safety switches because the blades are not fully engaged which reduces the current carrying capacity of the switch. the repair is easy,knolox the blades and operate the switch half dozen times, but its something to watch out for. think of a four hundred amp service switch thats twenty years old and never been turned off-then you turn it off and back on--check the engagement...

 

[bphgravity]

Re: how often is switchgear maintainance preformed?

A few years back, I started putting together a maintenance and service procedure program for a huge agricultural facility. This "farm" has nearly 50 services on site with dozens of huge 200A and 400A kife switch disconnects serving each greenhouse or field.

The first thing I noticed when inspecting the equipment "shacks" were short pieces of 2x4 lumber or PVC with notches at their ends next to the enclosures. As it turns out, hardly any of the switches would open without an incredible amount of force on the handle. One of the electricians would literaly bounce up and down on the handle to try to get the knife blades free.

Upon rengaging the switch, the blades would never reinsert. All the door interlock mechanisms had been removed so the doors could open with the switch in the closed position and the electrician would proceed to "hammer" the blades into place with the pieces of 2x4 or PVC.

This was striking evidence that preventitive maintenance and equipment servicing is of up most importance. When current flows through a conductor be it the wiring or the metallic parts of a switch, the heating and cooling chages the characteristics of the metal and structure of that conductor. In short, a current-carrying conductor is a moving part that requires maintanence and service like any other moving part on machinery.

I concluded, the fused disconnects out lived their usefullness, and recommended replacment with main breakers. Many have been changed to date, but many are still in operation. The crews now do a monthly switch exercise and part lubrication.

 

[charlie tuna]

Re: how often is switchgear maintainance preformed?

recently we were called to a county administation building by the elevator contractor who was being blamed for power problems in the building. after monitoring power to the elevator equipment we found a serious voltage drop to the elevator distribution equipment panel. eventually, it was traced to a 4000 amp prinkle switch that was engaging only about fifty per cent of the fully engaged position. this problem has been festering in this building for over the last fifteen years with equipment failures. you would think a government building would have some sort of maintainance guidlines????????????

 

[ShockedOneinAZsun]

Re: how often is switchgear maintainance preformed?

It has been my experience that this type of maintenance is only performed every 7-10 days. That is, 7-10 days after a major meltdown has occurred. Most factories I have worked around are operating on the "luck-factor".

 

[brian john]

Re: how often is switchgear maintainance preformed?

MAintenace:

Should be performed on regular schedules per the manufactures recommendations.

 

[brian john]

Re: how often is switchgear maintainance preformed?

Maintenance should be performed on regular schedules per the manufactures recommendations. Having said that in Washington DC all equipment 480/277 VAC 100 amps or larger is required to be serviced every three years.

As for large bolted pressure switches I would NOT recommend Nolox as a lubricant. The switch manufactures have specifications for the type of lubrication to be utilized, in addition there is required lubrication of the moving parts to ensure the switch functions per design, lastly I would recommended a DLRO/ducter/micro-ohm meter to verify contact resistance as part of any service, and testing of the GFP is recommended.