To fully understand and appreciate the importance of Uninterruptible Power Supplies (UPS), it is crucial to first understand how electricity is generated and distributed in whatever country in the world you are in. In many westernized societies it is tightly controlled, regulated and quite reliable, but in other areas it is not and energy protection at the end point of consumption, be it commercial or residential, must take this into account. It may be that some form of microgeneration is what is needed, as well as an uninterruptible power supply.

Electricity can be derived from a number of sources these days and the call for renewable technology in response to environmental pressures means the list is getting longer. Coal, gas or nuclear power stations have been the main methods so far, but wind, wave or solar power are starting to make their mark.

The phenomenon that generates electricity is called Electromagnetic Induction. Its output is an alternating current (AC) waveform. The process by which this happens uses magnets on a shaft that rotates near the windings (usually three) in which the electrical current is induced; called electromotive force. The process is the same in each case; the only difference between each of the power generation types is the fuel it uses to turn the shaft.

The windings within a generator are separated by 120 degrees of rotation, creating a three-phase waveform comprising components P1 (phase 1), P2 (phase 2), and P3 (phase 3).

The kV measurement, at which electricity is generated, varies around the world, from country to country, region to region. In the UK for example it is usually 25kV which is stepped up to 275/400kV before being distributed as a 3 phase 50Hz supply. It needs to be distributed at a high voltage to overcome resistance (which could be in the mains ) or transmission losses. However, as it moves through the network to the point of use, the voltage drops. On the outskirts of major towns and cities, substations reduce the voltage. In the UK this would be at 132kV. These substations are connected to even smaller substations which reduce the voltage further to 33 kV and 11 kV (UK). These are located within or near the delivery point.

It is in these substations where a neutral and earth reference is added so that, in the case of the UK, a 400Vac, three-phase, plus neutral and earth (TP+N+E) can be supplied to the site’s incoming unit. or building, which can be residential (larger buildings such as tower blocks), commercial, or industrial. The physical point at which this happens is known as the Point of Common Coupling (PCC). In the UK, a single phase 230Vac supply (more typically for residential consumer use) can be derived from the same substation (or entrance), drawing on any phase and neutral. In this way, the ground and neutral references are connected throughout the route of the distribution network to the substation.

Each country or region of the world has its own set of transmission and distribution network codes that govern the generation and distribution of electricity. In particular, these stipulate minimum and maximum values ​​of voltage and frequency allowed.

For any site, the quality of power received through its input is directly affected by the performance of the upstream electrical distribution network. Today this can be intercontinental and encompass a variety of political and cultural settings. Within a distribution network, power problems can be caused by:

Network operation, network switching, automatic reclosers and fault location.
Network hardware failure, including transformer and circuit breaker malfunction.
Power shortages during periods of peak demand when supply is restricted.
Accidental cutting of supply cables during construction or street works.
Acts of terrorism, vandalism or deliberate sabotage.
Environmental activities such as lightning, heat, rain, snow, ice, wind, or wildlife.

On any site, a stable and clean supply of electricity can be affected and influenced by local surges, simple switch failures, and the operation of industrial or commercial equipment and fixtures, including power presses, welding equipment, elevators, escalators, air conditioners. air conditioners, photocopiers and fluorescent lights. All of this can induce power issues on a main power supply that may have been reasonably stable and clean beforehand.

A review of power generation and distribution and the effect it could have on power quality (along with other environmental, political and social disturbances that may have an effect) has a bearing on the size and type of power supply uninterrupted which can be ideal for a facility.

This article was compiled from information available in The Power Protection Guide: The Design, Installation, and Operation of Uninterruptible Power Supplies (ISBN: 9 780955 442803). By Robin Koffler and Jason Yates of Riello UPS.