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Re-energized Arrestor

Our job was to change out a 10 kva overhead transformer with broken secondary bushings. The Arrester was configured with the high-side tap for the cutout on a T-bracket. I opened the cutout door, then removed the hot high side cutout tap which de-energized the MOV Arrester to gain clearance to change out the transformer. After changing out the transformer and reconnecting grounds and neutrals I attempted to re-energize the high side of the cutout which re-energizes the Arrester. I was using an 8-foot grip-all to install the LLC when I heard a buzzing noise and pulled the duck-bill away from the stirrup. Repositioning the bucket to gain the most clearance as possible, I ducked down and re-installed the duck-bill. Moments later the arrester failed violently. The Isolator separated and the side of the arrester ruptured. The 80-amp recloser operated clearing the fault current, then it re-closed picking up the feeder load. The Crew leader called up to see if I was alright, my ears were ringing a little, but I continued to change out the defected arrester, and then picked up the customer.

I am ok today because all my Safety Equipment was used.

All PPE was being used. Maximum clearance and ducking my hard hat directly towards the Arrester helped protect me from the flash. Common sense alerted me to the buzzing as an indication of an Arrester or other equipment was getting ready to fail.

The lesson I learned:

Never energize a previously energized Arrester using 15 kv gloving methods. Always use at least an 8-foot grip-all maintaining maximum clearance. Only use gloving methods to install a brand new out of the box arrester. Change out the questionable Arrester or use an Arrester tester to verify the condition of the Arrester before re-energizing.

Be safe, use Safe work habits, you never know when you will need them.

Lucky lineman

Some responses to the above posting

17 Jul 2001

To the LUCKY LINEMAN, I agree that you were lucky in that you used a shotgun or grip all to place the arrestor back in service, but I disagree with the lesson you learned. The lesson learned is actually this....you should always use a grip all stick or shotgun to energize an arrestor whether it is new or old and no matter what type it is. The reason being is because it can be faulty even though it is brand new. If it is a faulty arrestor you are essentially placing a dead ground onto an energized conductor. I don't know about you but I would rather take the extra step of using the 8 foot stick to do that with that just a set of rubber gloves....... If you disagree....just ask someone who has made that same mistake and had it backfire on them...

17 Jul 2001

To the concerned individual. We are 15 kv glovers. Our work practices and gloving procedures keep us Safe. With the proper rubber up, arrestor cover, split blanket, ect we have never had a brand new out of the box arrestor fail in the last 10 years we have been gloving. Ferroresonance, circulating current and improper switching have caused newely installed arrestors to fail on the line. But so far, I am not aware of any new ones which have failed new out of the box. Our intention is to minimize the risk of any unforseen hazard. If we can not get a tank mounted transformer out of service, always our first option we have gloving procedures to protect us... On most banks and single pole applications, with the correct cover, we have a history of doing the change out Safely. Please understand these are our rules, everyone uses a stick first. Please share your experiences, we are all here to learn. Thanks,

18 Jul 2001

You are correct that sometimes it is necessary to use the gloving method to remove and place an arrestor in service. I have had to do the same on voltages up to 34.5 KV, and understand that it can be done if all the proper cover material and safety procedures are used. From first impression you seemed to be saying that it was okay to glove them as long as they are new.....although it can be done, it is not the preferred method. I see where you were going with that now. I was questioned by my apprentice about it and figured there were others out there that might need to know that the only for sure way to stay safe is to use a shotgun stick. As far as arrestors failing on new installations, well in the 5 years I have been around them, I have seen 2 fail that were brand new. Hope this clears up any misunderstanding of my concerns.

Date:

02 Aug 2001

When dealing with arresters, caution is the word. We ran into a situation about 10 years ago where a *kv arrester and a 3kv arrester were virtually the same. Same size color and the thing is, the only way to tell is to remove them from their boxes or look at the fine print on the bottom. Well needless to say, at night and in some new installations the 3kv ended up on the 8kv. Dead short to ground. Think about putting a ground onto an energized phase by hand. That's what you get. But how many of you guys are building a line and hooking up the hotline clamp onto the line which is hooked to the source side of the switch and than going to the feed pole and making the tap by hand.

Use sticks at all times when hooking up an arrester or a line that has arrester attached to it. Don't be stupid!