Use of Isolator Switch on a Live Plant

[PRincez]

Hi,

This question is related to a site in the UK.

I designed electrical power supplies for the site security swiping system. Some of the supplies were for control panels and auxiliaries 300m away from the power source.

I always include local isolation in my design for electircal consumers located exeternally in plant however in this instance I have been asked if the isolators can be removed. I am not confortable with this and want to back the intent up with an IEC or BS standadrd.

Does anyone know the applicable standard(s) for use / selection of electrical isolator switches please.

 

[ScottyUK]

If there is a means of securing a remote isolation then a local isolator may not be required. Conversely if no means of securing the remote isolation exists then a local isolator probably will be required. Does the site have a recognised safe system of work, for example a permit system with controlled isolations? For example, a remote isolation secured in a controlled-access substation on a site operating a permit-to-work system wouldn't worry me. Equally there are plenty of situations where I would be downright uncomfortable with a remote isolation. You need to look at the specific circumstances of the site and the competence and capabilities of the site owners / users.

I don't think you'll find anything in UK law which makes a local isolator mandatory - the law requires a means to provide safety from the system, a phrase which has specific meaning in law, but the law does not define how to achieve safety from the system. In this respect the law really isn't much help.

 

[Hoxton]

Perhaps there is a concern that isolators on external panels can be operated by the public, putting the panel out of action. In this case, an isolator elsewhere may be acceptable, provided that there is a safe system of work in place. Alternatively, an isolator inside a section of the remote panel, opening the isolator permits access to the power section.

For general guidance, I suggest that you look at HSE Electricity at Work : Safe Working Practices on the following link.

http://www.hse.gov.uk/pubns/priced/hsg85.pdf

Download is free

Isolation is not the only issue, there must be a safe system of work, risk assessments, permits to work etc etc

 

[KuanYau]

To PRincez (Electrical)
(OP)

1. " I am not comfortable with this and want to back the intent up with an IEC or BS standard. "
I suggest you may look up the following documents on this matter:
a) BS 7671 : 2008 Clause 537.2.2.5 , or later editions, and
b) IEC 60364-5-53 :2002 Clause 536.2.1.2 and Clause 536.2.2.6 , or later editions.

2. Please inform me if the above mentioned documents are not available in your location.
I am able to furnish the [full text of the above clauses] from both Standards.