Electrical services for stands at NEC are an exhibition in themselves
Exhibition centres throughout Europe are watching with great interest a pioneering approach at the National Exhibition Centre for supplying electrical services to stands that can be set up and controlled from a central point using a SCADA system. Ken Sharpe reports.
Large amounts of time at a major exhibition centre such as the NEC (National Exhibition Centre) at Birmingham are taken up not by exhibitions themselves but setting them up and breaking them down.
Specialised custom stands have to be built and decorated. Shell schemes take less time to build — but what all stands need is an electrical supply.
Every exhibition has a different layout. Stands have a wide range of electrical requirements, including both single-phase and 3-phase. Current requirements vary, too. Steve Neal, venue services manager with the NEC, tells us that a 63 A supply will satisfy the needs of 90% of stands. Stands needing even more power include those with large presses at the IPEX printing exhibition.
Even with the then advanced facilities designed into the NEC when it was built in the 1970s, wiring up an exhibition was a complex and time-consuming process.
However, a couple of years ago, Steve Neal started experimenting with a different approach — which has since grown into a sophisticated SCADA-controlled system that is much quicker to set up and strip down. In addition, it enables a central control point to establish whether a stand should have a single- or 3-phase supply, restrict the current that can be drawn by a stand or group of stands sharing the same supply and bill each and every supply.
SCADA stands for Supervisory Control and Data Acquisition. It generally refers to an industrial control system such as a computer system monitoring and controlling a process and has the power and capabilities to manage what the NEC expects.
Steve Neal tells us that this is the first such system in the world and that the NEC’s pioneering approach to setting up electrical supplies for exhibitions is being watched with great interest by other exhibition centres in Europe.
The NEC is the largest exhibition centre in Britain and the seventh largest in Europe. It has 21 halls with a total area of 200 000 m2.
Services for the stands are provided from below. Subways with a headroom of 2 to 2.5 m run the length of the halls, with ducts about 45 cm wide and 30 cm deep running off at right angles. These ducts have heavy covers to withstand the weight of vehicular traffic, and they are lifted manually to provide access.
Electrical power for the stands used to be provided by heavy cables tapped into busbars in the service tunnels and then drawn through the ducts to emerge near the stands to be serviced. The size of the cable had to be matched to demand, and a range of cable lengths had to be kept available. Overall, the process of powering up an exhibition was heavy and time-consuming work.
The beginnings of the current approach started a couple of years ago in response to changes in the Wiring Regulations requiring RCD safety protection. Panels with eight outgoing ways, each with RCD protection, were installed — with their power supplied by 300 A tap-offs from a busbar.
Steve Neal explains that the NEC’s Satchwell building-management system was set up to control these panels and that it could monitor power consumption. He describes it as a very successful development that prompted him to start thinking about permanently laid cables with no point in any hall more than 9 m from a socket in a floor duct and with a much more advanced control system. These cables would be capable of supplying single- or three-phase up to 63 A.
The wiring contractor that was bidding for the installation of sockets, cabling and panels for a system to upgrade the power supply to 17 of the 21 halls approached Severn Controls as a partner to provide software and build the panels. The NEC’s requirements were for a system that included fixed wiring to thousands of fixed sockets throughout the halls and panels to provide automated control over the entire system.
Chris Rowston, technical manager with Severn Controls, tells us that this contractor subsequently withdrew and that Severn Controls was invited to prepare a direct proposal for panel design, build and software development.
A detailed discussion of the NEC’s requirements led to Severn Controls suggesting developing a SCADA system using bespoke software to provide great flexibility and enable a huge range of functions to be automated.
A simulation of the proposed system was created to demonstrate how the software would make it possible to control all panels, sockets, meters etc. The capabilities of the system would include switching power on and off, allocating single- or 3-phase supply to any of the fixed sockets in the halls, limiting the current available and monitoring power consumption. In addition, the new electrical installation complies with the latest European safety standards. That demonstration led to the award of a £2 million order.
Using PLC (programmable logic control) and SCADA packages from Mitsubishi Automation, Severn Controls created a fully automated system. The company then created a bespoke utility for stand bookings and system configuration written as an SQL 2005 database.
Seventeen of the NEC’s halls are now prewired. There are 65 electrical distribution panels in the subways. Each panel supplies 30 circuits, and each circuit has two sockets — 1950 circuits and 3900 sockets in all. Every panel and every circuit has its own power meter. In addition, every circuit has a timer that can be set up from the centralised control system to turn power on and off when required. To avoid large power surges, circuits set to be energised at the same time are actually switched on at one-second intervals.
Chris Rowston believes that the NEC system is by some margin the largest in the UK.
The previous approach to energising an exhibition was, before it opened, the contractor had to go into the subways, put fuses into the circuit and turn on power to the stands. Power remained on until services were isolated at the end of each day.
Wiring from the sockets in the floor to the stands is carried out by stand electrical contractors, and the supply is not energised until the appropriate paperwork has been completed.
The entire system is controlled from a control centre with a 42 in screen, which displays an aerial shot of the NEC. From this aerial shot, it is possible to navigate to a particular hall and then right down to every socket and panel.
Identifying and locating faults from the control room is a very significant benefit of the SCADA system.
Previously, faults were reported to the exhibitor helpdesk and then passed on so that an engineer could be sent out to deal with the problem.
Now, if there is a problem with a panel, an MCB or RCD on a circuit, an alert appears on the control screen, and an engineer can be despatched with foreknowledge of the problem to be dealt with.
In the days, weeks and months before an exhibition, information about the electrical requirements of each stand can be entered and then used to provide the required power to each stand when the temporary wiring has been completed. At the end of an exhibition, data from the panels provides accurate billing information. A new configuration for an exhibition can only be activated when the entire power supply to a complete hall has been deactivated.
However, it is also very easy to respond to late stand bookings and to changes in requirements during the period of an exhibition — simply by reprogramming the appropriate socket.
Enabling a power supply to an extra stand is simply a matter of clicking on the socket icon nearest the stand and setting up the required current and whether the supply is single or 3-phase. A trip can also be set up to ensure that the agreed current is not exceeded. If an exhibitor later asks for more current to be available, this is easily set up.
Just as with any building-management with distributed intelligence, the central controller simply monitors and provides the means of setting up the SCADA system. Each panel is equipped with a PLC so that it will operate independently according to the instructions it has been programmed with — even if the server and network both fail.
With such powerful and centralised control, it could be all-too-easy to lose all power to an exhibition through human error. However, the system avoids this possibility by permitting only a single panel to be the largest unit that can be turned off — and then only when a series of warnings have been acknowledged.
Steve Neal is confident that the new fully automated electrical control and monitoring system, will prove a major success. He believes that the NEC is well ahead of other leading exhibition venues in Europe and tells us that they are keeping a keen eye on what is happening at the NEC.
