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Topic Title: Electrical safety rubber gloves
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Created On: 18 May 2010 05:39 AM
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 18 May 2010 05:39 AM
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janaka077

Posts: 38
Joined: 25 July 2008

we are working 132kV /33kv grid substations. Our workers usually
engage in isolator operations and maintenance. we are going to purchase electrical safety rubber gloves. which class of gloves do we have to purchase?.
 18 May 2010 09:36 PM
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dlane

Posts: 689
Joined: 28 September 2007

If I understand your question correctly, I would have to ask what you are doing at these kind of voltages that warrants the issuing of insulated gloves?

All tooling / work procedures should keep your work force outside of the minimum safety distances specified in your safety rules. Once the conductors have been proven dead and earths applied they can then be allowed to encroach the safety distance and work on the conductors.

EN 60903 is the European Standard for insulated gloves and gives a maximum of class 4 that has a proof voltage of 40kV rms so they are insufficient for 132kV anyway.

Kind regards

Donald
 19 May 2010 12:18 AM
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simongallagher

Posts: 148
Joined: 28 July 2005

The way I understand the question, the poster wants to supply electrical gloves for his engineers use when switching out and earthing the circuits. This is normal practice when operating manual HV O/H switches/Isolators.

Along with earthing matts and insulated inserts, this forms a system for reducing risk.
 25 May 2010 04:40 PM
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janaka077

Posts: 38
Joined: 25 July 2008

thank you for your replies.
As 'simongallagher' said , we use gloves at following cases,
1.open isolators/disconnector switches (manually )after circuit breaker open. or
2.close isolators before circuit breaker close.

the busbar voltage 132kV
 25 May 2010 08:25 PM
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dlane

Posts: 689
Joined: 28 September 2007

New one on me, I have never been trained to use insulated gloves when operating 132kV isolators and earth switches.

I'll have a word with some other SAPs and see what the reaction is.

Kind regards

Donald Lane
 26 May 2010 02:02 PM
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ArthurHall

Posts: 735
Joined: 25 July 2008

Use of HV rubber gloves is common when operating certain distribution voltage switchgear such as pole mounted switches, line and busbar isolators in substations and cubical type substations. I dont think they are used as much at transmission voltages.
I think the ones I used to have wear were rated for about 6KV and were in addition to primary insulation and operator earth mats.
 26 May 2010 10:09 PM
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alancapon

Posts: 5745
Joined: 27 December 2005

The insulalating gloves are an extra protection against things going wrong. In theory, air break isolators should have an insulating insert in the operating rod, and an earth mat at the position where the operator is supposed to stand, electrically bonded to the operating handle. In theory, this means that there will not be any potential across the operator, regardless of what happens at the top of the pole. Some companys require additional protection "just in case", such as insulating gloves, which are rated for the voltage which might develop between the handle and the ground if something goes wrong (which will almost certainly be much less than the phase to earth voltage), insulating wellington boots (to guard against step potential if the operator is stood in the wrong place or running away). The other option is to remove the handle completely, and operate the switch using a set of tested insulating rods.

Regards,

Alan.
 28 May 2010 04:11 AM
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janaka077

Posts: 38
Joined: 25 July 2008

thank you Alan , for your explanation. Then can u tell me, what class of gloves should I purchase for applications like operating 132kV isolators (manual operation). what is the minimum voltage that might be occured (or considered) between isolator hadle and groud earth mat.

regards,
janaka
 28 May 2010 08:50 PM
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alancapon

Posts: 5745
Joined: 27 December 2005

That is not an easy question to answer, in fact I am not going to geve a specific answer here. You will need to look at your construction standards, your maintenance regime and your fault current.

The worst-case scenario is a single insulator failing to earth on the isolator at the time it is operated. You will need to calculate the rise of earth potential during such a fault, the likelihood of this happening, and the likelihood that the operator will be standing at a position where they will be subjected to a voltage between their feet and the operating handle. This should give you a rating of the gloves you require. You also need to remember that the higher ratings of gloves may be safer, but will be less flexible, and you may not be able to operate the mechanism of the isolator with them on, making them impossible to use.


Regards,

Alan.
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