Generating sets should be sized and installed by generator professionals like ECO Power Supplies. Our power and energy consultants are trained in the sizing, selection and installation of generators and their use within power continuity plans to deliver resilience and long term reliability, Our consultants will consider a wide range of factors when planning a generator installation.
- What do you want the generator for – standby power or prime power?
- Consider electrical load in terms of how it draws current – linear or non-linear, resistive, capacitive or inductive?
- Identify loads that have cumulative impact.
- Identify loads that have high in-rush currents.
- Consider kVA and kW levels at steady state.
- Consider non-linear loads, harmonics and impact on system sizing.
- Identify power factor and its impact on system sizing.
- Determine voltage, frequency and kVA.
- Consider housing, location and environmental implications.
- Consider monitoring and control and how this will be done – suitable automatic control system, compliant electrical protection system.
Apart from sizing the generator care has to be taken with generator pick-up for certain types of load including synchronisation with an uninterruptible power supply (UPS) system if installed as part of the power protection plan. Generators should not be sized on a 1:1 ratio with UPS as the generator may be required to power additional loads such as air-conditioning and emergency lighting. The generator also needs to allow for higher currents as the UPS charges its battery set. The UPS rectifier and static bypass must be synchronised to the output of the generator, and for load acceptance to occur, the UPS must synchronise to the voltage waveform supplied by the generator. This can be tricky as not all generators and UPS are compatible. Load type can have a bearing on generator sizing, as can loads that cause high in-rush current at start up (mechanical loads and Tungsten lighting, for example). Good diesel generator installation procedure is to oversize the generator by 1.25 to 2-times the size of the UPS.
Generators are supplied with an Automatic Mains Failure (AMF) panel (essentially part of the control circuit and switchgear), which monitors mains power and instructs the generator to start-up on failure and shut down once it is restored. Generators can be installed so that they can be monitored remotely through the AMF panel (and via a D9 communications port and RS-232 communication).
Generators are typically air-cooled and provision needs to be made for this and for ambient temperatures to be constant where the generator is housed. Generators also produce exhaust gasses, which must be vented, and noise (upwards of 100dBA). Catalytic converters with silencers can be installed to reduce emissions.
A clear understanding of the application for which a generator is intended and characteristics of loads will help ease the complexity of sizing and generator installation.