Electrical installations work is carried out by our qualified teams of electricians and electrical contractors. These engineers are both certified and qualified to provide the necessary levels of expertise and skills required whether the job is to install electrical lighting, single or three phase wiring circuits, extensions and distribution boxes to complete electrical fit-outs and the connection of uninterruptible power supplies and air conditioning systems.
How we approach electrical work does of course depend on whether the site is a new build or existing one. For new builds, our planning team may be working to drawings, models, bills of materials and tender specifications. For existing buildings, this may also be the case if an extension or new fit-out is planned but in most cases, we are adding to an existing system.
The key to successful electrical contracts is communication and for this we generally like to start a new project with a site survey and meeting the relevant parties. Not only do we have to ensure a clean and accurate scope of works but whatever the electrical works we are doing on site, what we do has to be reliable and conform to the necessary local and national building codes and the latest edition of the BS7671 IEE Wiring Regulations (currently the 18th edition) and the Electricity at Work Regulations 1989. We also must ensure that the electrical work we do on site does not interrupt or interfere with other works and electrically powered systems or data carrying cables.
A site survey is such an important part of our electrical works program. From this we can uncover all sorts of issues regarding the electrical system including load profiles, electrical history, distribution, cable and breaker sizes, discrimination, fault-tolerance and resilience levels. Many sites including those with server rooms and their own datacentres can also today have on-site power generation in the form of renewable power (e.g. solar PV or wind) and be looking to the future where they may also consider local energy storage to help the site go ‘off-grid’ at selected times.
Electrical Project Scope
The complexity and scale of any electrical installation depends on the work involved, systems to be installed and connected and their size, and the overall existing installation limitations. When scoping out the electrical project we typically cover the following stages:
- Building incomer and load connections: from the LV switchboards and additional sub-distribution panels and ways, including UPS maintenance bypass arrangements for critical power loads, essential and non-essential loads.
- Electrical cabling works: AC and DC cabling works associated with UPS systems and battery sets, automatic transfer switches (if a generator is to be in circuit), static transfer switches (if N+X supplies are required) and future for electrical energy storage and resale from an existing renewable power set-up.
- Power distribution: to the connected loads in terms of plugs, sockets, fused spurs, hardwired terminals, power cords and PDUs including energy usage and efficiency monitoring.
- Interface cabling: for alarm and security panels, fire suppression and environment sensors, building management and network interfaces.
Power Discrimination and Fault Clearance
When designing electrical circuits for server rooms and datacentres it is becoming ever more important to both remove any potential single-points of failure and to ensure there is sufficient discrimination and fault clearance tolerances.
A single-point of failure, as the name implies is any single aspect of the electrical installation that could interrupt supply and catastrophically close the data processing operation. An example would be a complete UPS system failure and shutdown.
On-line UPS systems have an automatic bypass built-in that monitors the output wave of the inverter. Any collapse in the voltage or current waveforms generated on the output side of the inverter should trigger the automatic bypass to transfer the connected load to the other side of the UPS and the mains power supply (if present). Of course, the mains power supply must be present for this to work and the battery sufficiently sized to cover any break in power. Additional resilience can be added through an N+X arrangement (normally N+1) whereby an additional UPS system is installed. The same type of N+1 arrangement can be achieved for critical cooling to give resilience to the cooling system which again in turn is typically AC powered from the mains power supply.
In terms of electrical power, discrimination is the configuration of two or more protective devices so that an electrical shirt-circuit leaves the faulty device taken out of circuit quickly, without interruption to other devices. This is to protect the remaining devices and keep the datacentre or server room system up and running.
The process of correct discrimination relies on the electrical cabling design and selecting the correct circuit breakers and residual current devices (RCDs). Fuses are rarely used within electrical circuits as any failure can result in excessive downtime. It is easier to reset a breaker than to replace a fuse. Fuses should only be used and blown in extreme circumstances. The aim being to prevent excessive current causing a potential fire or damaging upstream or downstream equipment. Circuit breakers or residual current devices also provide these properties but tend be used within circuits. Fuses tend to be used within devices. At an LV switchboard or HV/LV switchboard, the circuit breakers may even be motorised and know as ACBs (air circuit breakers).
The sizing of the RCD in an electrical circuit is important due to the overloads and response times. It is also important to understand the characteristics of the loads in terms of their inrush currents and their duration. Whilst want to size economically, it is also important to remove any chance of nuisance tripping which again can lead to datacentre downtime.
Another important aspect to be avoided within any electrical systems is harmonics which can overload circuits and lead to hidden hot-spots. These build-up of heat areas often go unnoticed as they are behind panels. An example being within an LV switchboard. Not only can harmonics affect electrical efficiency but they can disruption operation and generate a fire risk.
In the EU electrical equipment connected to a supply must comply with the requirements of EN 50160 and for harmonics to G5/4. Whilst most systems do, the more electrical devices you connect to an electrical circuit, the more the chance for harmonics and electrical interference and disruption.
Power factor is another type of load-related power problem that can cause disruption to electrical devices, and to some types of older UPS systems. On large sites, a reactive power (kVAR) charge may be applied to an electrical bill each quarter and this can often be negated through the installation of suitable power factor correction.
High mains voltage can also be a problem on some UK sites. The reason for a high mains voltage in some parts of the UK arise from an increased number of renewable power system connection to the local mains power supply and the density of the connection map. A high mains voltage can lead to decreased energy efficiency and a suitably sized voltage optimiser can help to negate this effect. An uninterruptible power supply can also provide some of the benefits of voltage optimisation as the inverter can be set to deliver a very tightly controlled level of AC voltage output (230Vac single phase or 400Vac three phase) over a wide input voltage window.
Earthing and Bonding
Earthing and bonding are further considerations for electrical installations. This can help to protect installations from overheating, fire risk, failure and potentially lethal earth faults. BS7671 lists five types of earthing system referred to as TN-C-S (the most common for a UPS system), TN-S, TN-C, TT and IT. In the abbreviations T refers to Earth (French word Terre), N refers to the Neutral, S to Separate and C to Combined with I referring to Isolated. The source of an IT system is either connected to Earth via a deliberately introduced earthing impedance or is isolated from Earth.
Planning and scoping the electrical works for any aspect of a server room or datacentre is important to ensure its overall resilience and reliability. To future proof any electrical investment requires building the ability to scale either using modular systems or easy to extend devices, cables and components.