Construction sites and the use of RLV, guidance on the use of residual protection?

 RCDs on 110v sockets

from the discussion above, which is a few years ago, a conclusion was made that RCD’s are not required for RLV/ CTE transformer used in construction sites from Sec 4. 
It is clear from section 4 that additional protection for RLV sockets is not a requirement, for obvious reasons CTE 55v etc. 

however I have noticed a more recent trend of RCCB’s integral to the secondary side of the windings being implemented to ensure fault protection that can clear within the 5 second disconnection time under 411.8.3. It would seem primarily this is due to chaining multiple extension leads together or excessive lighting circuit lengths, which are difficult to account for except by direct supervision on site. 
Blakley, being one of the leading manufacturers offer a great deal of good technical guidance on the subject - but largely it would appear the practice of having both RLV + residual protection combined into one transformer is down to preference rather than a requirement of BS7671 or BS7375 for that matter, meaning this would be ‘best practice’ as apposed to mandatory unless a contractor were to make part of their policy. 
I would be interested in the forums opinions on this subject, and your own experiences, I think there are changing trends in the industry as to what was historically an acceptable risk may no longer be the case, particularly I’ve noticed 110v Tx plugged into blue commando sockets with a 30mA RCD protecting the primary side, I’m unsure what degree of protection this will offer to outgoing artic flex on the secondary side and it doesn’t seem it would be the same as a multiple pole device that’s installed on the secondary side?

Parents
  • I have been in the construction industry for fifty years and still have a full kit of 110 volt tools, extension leads, four transformers and three generators.

    I have only ever blown fuses due to overload back in the days of fused extension plugs on extension leads,  not due to faults and all three of the petrol engine generators I have will stall before the circuit protection built into them operates, as I have found out. 

    None of the younger guys have 110 volt kit,  they are using battery tools, the voltages and risks are probably similar. I don't think I would want to short one of the big backpack batteries used on some of the corded "cordless" power tools, particularly with the battery pack on my back. 

  • Indeed, battery tools are now considered the safest option to achieve ALARP. There are some hefty lithium batteries on the market now that are capable of doing serious damage if not handled with care and respect, I’ve even come across 230v inverter packs specifically designed to use class II core drills and the like, but when the manufacturer are requested to quote on compliance with British Standards they declined- the instructions were beyond layman’s interpretation too further adding ambiguity. 
    if everyone conducted their business as responsible professionals I’m sure many of today’s issue would be reduced, I guess some of it will be down to the growing skills shortage. 

Reply
  • Indeed, battery tools are now considered the safest option to achieve ALARP. There are some hefty lithium batteries on the market now that are capable of doing serious damage if not handled with care and respect, I’ve even come across 230v inverter packs specifically designed to use class II core drills and the like, but when the manufacturer are requested to quote on compliance with British Standards they declined- the instructions were beyond layman’s interpretation too further adding ambiguity. 
    if everyone conducted their business as responsible professionals I’m sure many of today’s issue would be reduced, I guess some of it will be down to the growing skills shortage. 

Children
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