Learn Stage Lighting

Stage Electrics – Lighting Distro for Dummies

A brief guide to the understanding and using of electricity systems in stage lighting, we start by looking at the basics of how electricity arrives at the stage and common equipment used in stage electrics.

Reader curiosity about power equipment and it’s uses has sparked (?!) this article. We won’t go through all the ins and outs of electrical theory but instead give you an overview of the systems involved and how to recognise certain elements.

Stage Lighting Rack

Disclaimer: This article is intended to provide some insight into the working of a professional stage electrical system for the beginner. It does not provide comprehensive training in electrics or safety and should not be viewed as such. The design of a stage lighting electrical system should be entrusted to an experienced and competent person. No warranty is implied concerning the accuracy of any information contained therein. On Stage Lighting can accept no responsibility for any inaccuracy of information or for any loss, damage or injury arising from any interpretation of its contents.

Stage Electrics and the Lighting Department

Historically, the wrangling of show electricity has been entrusted to the aptly named Electrics Dept. in theatres or the Lampies in a concert touring environment. These days, sound crew and riggers have an increased knowledge of power distro and often take care of much of their supply management and while on larger shows, a whole separate Mains department is common. No wonder, electricity is the one thing that we really can’t get by without.

While many departments use power, the overall design and distribution of a safe and bombproof electrical supply still often falls into the hands of the LX crew. Temporary power distribution equipment for events is commonly of the “plug and play” variety which doesn’t require a degree in electrical engineering to connect a system together but it does a good understanding of electrical theory and safety.

Anatomy of Stage Electricity Supply

It’s important to understand a little about how power arrives for us to use on stage, without going into all the details about substations, transformers and power stations.

Incoming Supply – With any luck, the venue has one or more incoming electrical supplies (usually 3 Phase) that comes in on a hefty set of cables. Big Cable = Big Power. The incomer(s) ends up in some kind of box ready to be split off to different parts of the building. You shouldn’t ever need to see the incomer but just know that it’s there.

Distribution Boards – Supplies from the main incomer are sent to a number of dist boards situated around a building depending on the electrical needs of each area. Each board has a set of switches that do different things and recognising them is important, particularly if you have a supply outage “upstream” from your kit. We’ll go into that in detail further on.

It’s also good to understand that some distribution boards, particularly smaller ones, can be fed from another distro panel – worth knowing in the case of a supply interruption.

3 Phase and Single Phase

When you’re new to stage lighting, 3 phase electricity is perceived as both mystical and dangerous – something scary and hugely difficult to comprehend. Let’s just clear this up – ALL ELECTRICITY CAN BE DANGEROUS. It can kill you, 3 phase or single phase.

Is 3 phase electricity more dangerous?

In the UK, our supply voltage is around 230 volts. This is the Potential Difference between the supply and Ground and if you get a Single Phase 230V electric shock it can at least ruin your day if it doesn’t kill you. With a 3 phase supply, each phase to Ground still has a p.d of 230V – however, the p.d between two phases can reach up to 415 Volts. So, what we call a “phase to phase” shock is more likely to kill you. In that sense, 3 phase is more dangerous but the thing that really does for you is the current (Amps). All large electricity supplies deliver lots of current, that’s their job. A domestic 13A socket will send you 13 Amps of sizzle before it fuses (plenty to knock you off your perch). Large lighting supplies can deliver >400 Amps and three lots of it too!!!

Let’s let the Grim Reaper take five for a moment and try to get behind the mystics of 3 phase electrics. Because of the way electricity is generated, it comes to us in three different supplies. What do I mean by supplies? Well, take a the socket on one side of your kitchen then another on the opposite side. Chances are, they are both different outlets of the same supply – and on the same phase. In fact, unless you live is a big house, you are likely to only have one phase coming into your house in total. One supply. Your neighbours house may well be on a different phase to you, with neighbours on the other side on the third phase. They are on different supplies.

We use all three phases in stage lighting systems because it brings more power into one place. The use of a large 3 phase cable is where confusion sets in but it’s just three supplies – 3 x Line/Live conductors and 1 x Neutral (shared between the supplies) plus an Earth. 3 Phase plugs usually have 5 pins, one for each conductor (actually, some 3 phase plugs have only 4 pins but we don’t need to worry about that right now).

Stage Electrics and Protection

Festival Lighting Rig

A major part of safe electrical systems design is what we call protection, things that stop people getting hurt by electricity and the fallout when something goes wrong.

People protection – The parts of an electrical system that protect people from electric shocks cut the supply at the first sign of trouble. In the UK, Residual Current Devices (RCDs,) are built into different parts of the distro system particularly at the “user” end such as on stage supplies to backline equipment. An ideal show supply would have individual RCDs protecting small power socket outlets, moving lights, consoles etc meaning that any interruption does not remove the entire supply. RCD’s are called GFIs in the US.

Kit protection
– Fuses or MCBs (Miniature Circuit Breakers) provide overload protecton – cutting the supply if any equipment draws more power than the supply was designer for. Overload on a circuit is a good way of detecting some kind of fault and ditching the supply prevents fires and excess damage to kit. Fuses or MCBs don’t save people.

Recognising Switches

On venue dist panels and lighting distro kit, switches are very much the thing. Working out what they do is the first step on the road to recovery in a power outage. If you do suffer from a loss of power, work out where in the stream the loss has occurred and switch off all outlets downstream of it before firing it up again. The most important part about re-energising (fancy word) is to do it in a controlled manner and with a full understanding of the entire system. Flicking a breaker back on when your buddy has his hand in the back of another distro will make you either unpopular or a criminal or both.

– A switch that simply isolates the power. Maybe a big, single red switch on a dist board or a separate box with a toilet flush handle, the isolator is used to shut off power to a panel when performing maintenance on the installed system. The isolator is not like an MCB or RCD, it doesn’t go off of it’s own freewill.

It is worth knowing that some electrical installation boxes have some form of isolator that activates when the front panel is disturbed or door is opened, particularly ones that have live terminals inside. If you are still reading this article, obviously you wouldn’t be poking around in such a box but mysterious power outages have been solved by banging on a worn isolator door to shut it properly.

RCD’s – RCD’s on a panel or distro box are often different to the majority of other switches in appearance. They usually have writing on them that give details of the tripping current such as 30mA or 0.003A and have a Test (T) button. If a RCD can’t be reset, it’s likely that you will need to unplug all equipment downstream before fault finding.

MCB’s – MCB’s usually make up the majority of switches on a board and provide an isolator to the circuit as well as overload protection. Usually marked up with their type letter and their maximum power rating in Amps such as C16 – a C type rated at 16 Amps. 3 Phase MCB’s look like a line of 3 switches with their handles joined together and are again marked with their type and rating.

Temporary Stage Power System Basics

When designing a stage power system, you essentially have the same elements as the building supply we talked about at the start:

Incoming Supply – From the venue, a facility panel with one or more sockets. These sockets might have their own isolator switches, RCD’s or overload protection near them but they could also be upstream and the dist board supplying the outlet. It’s good to find out where this is before you need it.

Main Distro Box – Often receives a large 3 phase supply and splits it down into smaller outlets either 3 or 1 Phase. Each outlet has it’s own MCB protection and the whole box may have some form of RCD. The RCD on a Main Distro box might have a key switch to disable it – this is for situations where you have adequate RCD protection downstream of the box and wish to eliminate the chance of a whole supply outage. The switch isn’t to be used just coz you have earth problems with the kit and the supply keeps popping out.

Sub Distros – Further down stream, you might have small supplies feeding other distribution boxes for a load of moving light supplies, dimmer feeds and power for other departments such as sound or rigging. What each department requires is very much where the system design starts (with regard to how much total power is available at the incomer too, of course).

Individual Feeds
– Dimmer outlets, cables to moving lights, sockets for the band etc. This is where the user meets the juice.

The End Result

A stage electrics system is just like any other power distribution. It starts with a very large supply and cascades it down through various types of protection until it arrives where it is needed via a much smaller socket.

Using specifically designed distro kit with competence, creating a safe and reliable power system doesn’t have to be hard. Getting a rock solid incomer in certain parts of the world can be tough and getting a decent earth in the desert even harder – but that’s another story.

Electricity should be taken seriously. Stay safe.

  1. Rob Sayer

    @ Jimmy – Larger shows + specials like outdoor events have power requirements that need a dedicated team to look after them. There is a decent amount of work in this area – quite a lot of lampies also work as main engineers.

    I did this on the G20 Summit at Excel, just mains – the lighting department being a different crew. You can imagine how important the electric supply is on a large site like that.

  2. Rob Sayer

    While systems design and wiring require a level of competence/qualification, most of the components are plug and play.

    Lampies have more experience of these temporary supplies than standard electricians so are ideal to crew the mains department. The right bits of paper usually belong to those who oversee the work and the test/inspect guys (who usually know more about earth loop impedance that what the rigger want from a supply).

    We all do our own thing.

  3. Ross

    Nice article as always : )

    All electricity is safe as long as it’s used correctly, i’ve had more than one shock from a domestic 13A ring main and yes, it’s painful – and can be lethal.

    The current required to be fatal is as little as 30mA under the right (or wrong) circumstances so any supply can deliver that, I seem to remember once of the reasons why three phase is more dangerous is something to do with them being out of phase as well.. either way I haven’t heard of a case where someone has survived a shock from a three-phase supply so it does somewhat encourage you to treat it with rather a lot of respect 😉

    Other thing worth noting under the topic “Lighting Distro for Dummies” … I’ve met many people from various walks of life who dabble in lighting (i include myself under that “dabbling” category also) who don’t realise that a dimmer channel at 0 is still “on” and has a very real and very painful 230v present at the output 😉

  4. Lewis

    Nice article. Thanks Rob. I would have liked it to read on in a little more detail though.

    I have had a little shock from a dimmer channel at 0 before in full knowledge that “0” does not mean “off”. I was up a ladder struggling to unplug a lantern where the socket on the extension was particularly tight and I eventually gave in and used my Leatherman to pries the plug out. I hadn’t plugged the other end in yet, but I didn’t check with my colleagues and one of them had patched it in for me. I received a nice little jolt as a reward. I got off lightly with a mild shock and I’ve never been so careless since.

  5. Peter Balint

    Rob. I realise this not quite your field but it is close!

    What curve trips would you advise to use on a stage power distribution for a sound system and musicians?

    I need to build a power distribution system for a PA I’m putting together. I’m starting with a 64 amp connector in, which will split into 2 x 32 amp outputs via a RCD and 2 x 32 amp MCB trips. I’m then building 2 more 32 amp splitters which will have 16 amp sockets out via 16 amp MCBs which will supply the racks and stage floor boxes if necessary. I’ll have various adaptors to I can handle varying situations. Including a 3 phase plug to single phase 64 amp cable although only one phase will be connected; I toyed with the idea that I could make that a switchable adaptor so I could choose a phase but I cannot think why!

    One phase is enough and desirable although not essential and I won’t need 64 amp but it may be what is offered if not I’ll go straight into the 32 amp boxes. In the worst case scenario the 16 amp ins are adapted to 13 amp and plugged into a lot of sockets but the total power of the system would probably be quite limited (there is 10 Kw of amps and although there draw is less they still don’t plug in a wall socket that easily!) I will try to keep musicians power separate from the PA if possible.

    Today I thought I would order the metal distribution boxes but I did not know which is the best curve for this type of use. B would offer the most protection but I feel would be open to nuisance tripping and D seems to allow quite a spike, is C a good compromise? I suppose the equipment is fairly well protected by it’s own fuses and protection circuits. So maybe D is the way to go for trouble free gigs but are there any regulations on such things or even standard practice.

    I’m coming back into this after quite a long break and I cannot remember what we used to use, I probably didn’t take much notice as most the kit I have used over the last 40 yrs belonged to the companies I worked for and trips rarely gave problems.

    Thanks for a good article.

    All the best, Peter

  6. Rob Sayer

    Hi Peter. I also can’t remember offhand. I’ll have a think and look at some distros. …

    BS 7909 is the place to look, along with 7671.

    A number of 13A out stage boxes I’ve come across are a 32A incomer and wired as a ring main.

  7. Peter Balint

    Hi Rob

    Thanks for getting back to me. I’ve never used a ring main system on stage but I was thinking that it might be possible; I just didn’t realise it had been done. The issues I came up with were safe connectors, i.e. if the ring main is broken by someone unplugging a cable on a box there is going to be some live pins exposed on the box or lead as the power is coming in both ways! Although the 64 and 32 amp connectors will be the usual Ceeform I was going to try the 16 amp Neutrik True 1 connector for the floor boxes (the ring would be on a 32 amp trip) but the risk is still there with that connector I believe. The original 20 amp Neutrik Powercon may offer a solution as I think the terminals are covered on both in and out connectors but I didn’t want to use that as it cannot be disconnected live.

    I came to the conclusion that the musicians are not going to need a huge amount of amperage, although my system has a fair bit of power it is not being designed as a loud system. It’s an analogue project using a high specification equipment; the speakers are all Tannoy and do not give as large a SPL as other speakers of similar size but they do sound good. I think genres like jazz, acoustic and music that could benefit from a very high quality of sound will be the most suitable rather than heavy rock bands. (I’ve got to an age where I feel like being choosy!) I suspect a few guitar amps and keyboard setups is about it rather than huge Marshall stacks, so sending out a few 16 amp radial feeds to the musicians should be suffice.

    The main area where power is required is the amps and the desk end. As the amps are in racks behind each speaker stack I am going to send a 32 amp cable across the stage to provide power for the remote rack. (I would like to send it across the front but I suspect due to H&S I should be ready to send it round the back of the stage in some venues). The desk and outboard racks could plug in where they are sited in the auditorium if there are sockets available as all lines to stage are balanced and isolated so phase and earth variations should not be a problem. I will have a long 32 amp cable though so the desk etc can all star wire back to the stage distribution point. As I say in a lot of instances I will be happy to just put 13 amp tails on a couple of stage box extensions for the back-line equipment and keep the musicians off my system distribution system. That way they are the venues responsibility!

    Thanks for pointing out BS 7909, that is the one I have to read, and a quick scan tells me that things have tightened up a bit since I last got involved in live sound; but I have a feeling though that sound and lighting companies do not adhere too rigidly to the following:

    “Re-testing and re-certification (or amended certificates) when substantial changes in the distribution occur. Each event is different, but examples may be: New locations – each time a system is put together in a new location or venue”. Ha! Really…

    Yes I can believe it does happen at outdoor and events where power is from generators (something I’ll definitely leave to others) and large indoor events; however at a small gig in a club or a theatre or even live at the pub I just cannot see the testers coming out beyond the plugin type. (I always have a simple Martindale plugged in on the desk rack sockets just so it’s available to flash each feed at it’s end, and yes I have found places – even a large theatre – without an earth on the supply feed.) I will need to study BS 7909 carefully. I have bought a PAT tester for my equipment, I personally think the test is fairly meaningless but hire equipment needs to be tested and show the stickers for conformity.

    I’m old school and all my power cables will be Rubber H07 RN-F Cable; I did a check to see if it still complied and I notice it is still passes for outdoor use whereas most PVC actually doesn’t. New regulations is something I am very conscious of, but I’m sure my power will comply; I find that good quality materials and a technically sound design put together carefully normally wins the day.

    Thank you for all your help.

    Regards, Peter

  8. Rob Sayer

    Just to clarify, the ring wiring I mean is an enclosed box with 32A in, breaker etc. and 6 – 8 13A outlets wired internally as ring circuit. The boxes are installed radially when it comes to on stage cabling. The result is like a room ring-main-in-a-box. To be honest, if you want to put together some really robust and compliant distro, I’d talk to Rubber Box Co or similar. Their stuff isn’t particularly cheap but the result is bombproof, long lasting and easily defensible in case of incident. Then it’s plug and play.

  9. Paul Grace

    Thanks for such an interesting article. I’m a drama teacher in a school and was told when I was hired that a space was being refurbished as a fully equipped drama studio. I’ve just found out that to keep costs down they are planning on only running single-phase power. Not being a spark I don’t really know what this means! What sort of limitations will this put on the potential of the lighting rig?

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