This article is about standby generation and its integration into a project’s electrical system. Although this article is intended to be purely descriptive, it has by necessity to include some of the formulae associated with generators and electrical networks.
For standby generation the key question is what level of electrical supply security is required for any particular load. Once that question is answered it is possible to determine whether standby generation is required and if affirmative to calculate the size of the standby generation plant. If it is determined that a no-break standby electrical supply is required then UPSs should be considered, these are described in detail in article 02-03-00-00. Where UPSs are included in a scheme then the UPSs will themselves require support from the standby generation system.
Once the need for standby generation is determined the size of the plant is only one of the factors that has to be considered, the maximum size of motor that may be started when the site is running on standby power and the maximum deviation of voltage and frequency from the nominal when the system is running both at steady state conditions and step load conditions. A hidden factor is the psychological one, if standby power is supplied throughout a site for its process but the maintenance workshops do not have standby power for the kettles and showering facilities then either a rapid unauthorised system modification takes place or the maintenance staff let their feeling be known in no uncertain terms. The same is true of other workers who are not of the privileged group of workers with standby power. Their feelings of inferiority will affect the morale of those workers and will almost certainly have a detrimental effect to any team camaraderie that has been fostered by the management.
There are two basic forms of standby generation, the first is the traditional engine alternator combination which starts when called, with this type of standby system there is a delay between the system being called to run and power being available from it. The second is the synchronous motor/alternator combination with a flywheel and engine all on one shaft, its normal operating condition is for the synchronous motor to drive the flywheel, when the power to the synchronous motor fails the engine starts and runs up to speed when it connects to the alternator via a clutch, the motive power to the motor which becomes an alternator is provided by the flywheel during that period between the power failing and the engine taking the load.
This article examines the various standby generating systems and the determination of the size of generators and the most appropriate number of generators for the systems.
This article also examines the control systems that may be employed to control the standby generating systems.
Overall the aim of this article is to enable the early determination of the system requirements and the placement of contracts for the standby generation systems for a project. Also included within this article is the integration of the standby generation system into the electricity supply distribution system of the project.