Implementing the 18th Edition in concerts, theatre and events. Easy as…?
Concert in a field for 20,000 people? No problem, the electrical supplies, distribution and final circuits will be installed in a couple of days, tested and handed over. If it were made from scratch, it’d take many electrical wholesalers that long just to source all the hardware.
This is all good, but when the spectre of change to electrical standards loom, it can be a worrying time. When a temporary system is put together, it’s classed as a new installation, so should comply with the current version of BS 7671. In other words, from January 2019 every event will need to be compliant; having pre-built equipment that you can easily re-use is fine, until it needs changing. That is the Achilles heel of most systems; there is no physical room to add extra protection devices if it’s required, so changes can involve major – and expensive – re-engineering to stock equipment. It’s also possible that some distribution units could be rendered obsolete overnight. Ordinary electrical installations don’t have this issue so much; the distribution boards are specified based around the protection required given the requirements at the time.
So what changes are likely to affect the industry? We asked some of the ABTT companies for comment on the 18th Edition, and how it might affect their businesses.
Chapter 41 which covers protection for electric shock sees quite a few changes. Currently Table 41.1 requires circuits under 32 A to have a disconnection time of 0.4 seconds, whereas this is being increased to 63 A going forwards. This is not a problem if you use miniature circuit breakers for protection, as the operating time is the same between 0.1 and 5 seconds. However, as Mark White, EU Sales Manager for the international stage lighting manufacturer ETC notes
“Many theatres still have legacy equipment with re-wireable fuses in them; they won’t pass muster anymore. It could have financial implications for some.”
Regulation 411.3.3 requires the use of 30 mA RCDs to provide additional protection against the risk of electric shock. It has been revised and now applies to socket-outlets with a rated current not exceeding 32 A indoors. In events, both single and three-phase 32 A circuits are often used for distribution, powering other units with appropriate RCD protection on final circuits.
Richard Bunn, Senior Consultant for Venues with Consultancy Arup, elaborated on this
“We have been routinely specifying 30 mA RCD protection on circuits up to 63A. This is based on the view that these sockets are often very accessible and used by people with limited electrical knowledge, so the RCD reduces the risk of injury due to electric shock. Above this power level, there is a reasonable expectation that connection and associated equipment will be by a knowledgeable technician. From this viewpoint the amendments are in-line with our current thinking.”
There is of course the problem of ensuring appropriate selectivity (formerly referred to as ‘discrimination’) between devices, and ensuring that unwanted operation of RCDs does not occur given the normal leakage currents from equipment. Bunn continued
“The rise of LED based luminaires with smaller loads and deliberate leakage currents associated with EMC filtering is presenting a significant challenge for distribution strategies. The limiting factor on the number of luminaires that may be connected to a circuit has once again become avoidance of unwanted tripping of the RCD rather than total load on the circuit. This will impact the design of new connection panels for temporary equipment.”
For the first time in a while, a new type of protective device makes a debut in this Edition - the Arc Fault Disconnection Device (AFDD). These devices can identify arcing in a circuit and will provide protection for insidious faults like cable damage or equipment failure where there may not be enough current flowing to operate other protection such as circuit breakers, but enough to start a fire.
Currently they are recommended in final circuits where there’s a heightened risk of fire or the effects thereof i.e. sleeping accommodation, locations storing flammable substances or installations at risk of fire such as old wooden buildings for example. This is where they could come in particularly useful; many old theatres are full of old timbers in stages and roof structures for example. They usually contain lots of old wiring and equipment too – as such retrofitting AFDDs could provide significant benefits. Mark White did highlight the skilled nature of crews on events though
“We have had a sort-of manual arc fault detection in at least lighting circuits in theatres for many years. We all are taught that electrical termination screws come loose with time, and when that happens technicians spot the flickering in tungsten lights due to the loose terminals. However, what about the circuits you can’t see? Also not all stage lighting is incandescent, so electronic power supplies can mask the effects”.
Richard Bunn noted that
“The AFDD is an interesting development. If we risk assess our environment to be at heightened risk (temporary cables with connectors running across a wooden grid?), this could add significant expense. Embracing this will also be dependent on manufacturers designing the protection into dimmer and distribution product so that it is available on the market. It will be interesting to see whether this becomes a more standard requirement over time, noting that RCDs were originally introduced as a similar innovation in a very limited way, but the scope of their application has been extended in each revision of the Wiring Regulations.”
Another change that has caused a lot of excitement especially on social media is the need to protect cables against premature collapse in the event of a fire. The last Amendment (3) to BS 7671 has required cable in escape routes to be suitably protected, such as can be achieved by using metal cable supports. There has been a lot of debate about what constitutes an ‘escape route’ as it may not always be obvious – for example in a theatre the aisle of an auditorium could be classed as such, as could the ramp off the back of a stage at a festival. Regulation 521.10.202 has been updated and now requires cables to be adequately supported against their premature collapse in the event of a fire. This now applies throughout the installation and not just in escape routes. As Mark White observed though,
“Technical Standards for Places of Entertainment has had a requirement for many years that all cabling shall be enclosed in metal containment so as to contain it in the event of a fire and to provide mechanical protection.”
Surge Protection Devices (SPDs) are not a new introduction to BS 7671, but the relevant Section in BS 7671 has been substantially revised. SPDs made more of an impact in Amendment 3 of the 17th Edition, but included the requirement for a risk assessment based on the AQ criteria. That requirement has now changed and protection against transient overvoltages has to be provided where the consequence caused by overvoltage (Regulation 443.4):
(a) Results in serious injury to, or loss of, human life, or
(b) Results in interruption of public services/or damage to and cultural heritage, or
(c) Results in interruption of commercial or industrial activity, or
(d) Affects a large number of co-located individuals.
Few events would not fulfil at least one or more of the above. A large number of co-located individuals or ‘Commercial or industrial activities’? Well, pretty much everything the industry does fits into one or both categories.
Jim Brown, General Manager of rental company Pearce Hire neatly rounds up the industry barometer:
“As with all new regulations and standards there’s understandably a fear from businesses that they will be hit with extra demands and additional costs. The final changes, in the main, appear fairly reasonable. Some questions of interpretation remain-particularly with regards to Surge Protection Devices in temporary systems.”