Flexible AC Transmission Systems | FACTSPublished on 24/2/2012 and last updated on Monday 30th of April 2018 at 06:41:54 PM
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Major influence on system voltage deviation
Limitation of power transfer
Steady-state and dynamic stability limits
Fig. Shows today’s most common shunt compensation devices, their influence on the most important transmission parameters, and typical applications.
Fig.: The active power/ transmission angle equation illustrates which FACTS components selectively influence which transmission parameters.
Flexible AC Transmission Systems (FACTS) – What and why?FACTS is the acronym for “Flexible AC Transmission Systems” and refers to a group of resources used to overcome certain limitations in the static and dynamic transmission capacity of electrical networks. The IEEE defines FACTS as alternating current transmission systems incorporating power-electronics based and other static controllers to enhance control ability and power transfer ability. The main purpose of these systems is to supply the network as quickly as possible with inductive or capacitive reactive power that is adapted to its particular requirements, while also improving transmission quality and the efficiency of the power transmission system.
Features of Flexible AC Transmission Systems (FACTS)
- Fast voltage regulation,
- Increased power transfer over long AC lines,
- Damping of active power oscillations, and
- Load flow control in meshed systems,
Influence of Reactive Power Flow on Power System Voltage
Reactive Power Compensation in Power Transmission SystemConsumer load requires reactive power that varies continuously and increases transmission losses while affecting voltage in the transmission network. To prevent unacceptably high voltage fluctuations or the Reactive power compensation consumer load requires reactive power that varies continuously and increases transmission losses while affecting voltage in the transmission network. To prevent unacceptably high voltage fluctuations or power failures that can result, this reactive power, must be compensated and kept in balance. The passive elements such as reactors or capacitors, as well as combinations of the two that supply inductive or capacitive reactive power, can perform this function. The more quickly and precisely the reactive power compensation can accomplish, the more efficiently the various transmission characteristics can be controlled. For this reason, fast thyristor-switched and thyristor controlled components are replacing almost these slow mechanical switched components. Owner failures that can result, this reactive power must be compensated and kept in balance.
Effects of Reactive Power FlowReactive power flow has the following effects:
- Increase in transmission system losses
- Adding to power plant installations
- Adding to operating costs
- Degradation of load performance at under voltage
- Risk of insulation breakdown at over-voltage
Parallel and Series
|Type||Shor-circuit level||Transmission phase angle||Steady-state voltage||Voltage after load rejection||Application|
|nearly unchanged||slightly increased||increased||high||voltage stabilization at heavy load|
|nearly unchanged||slightly increased||decreased||low||voltage stabilization at light load|
|nearly unchanged||controlled||controlled||limited by control||fast voltage control reactive power control damping of power swings|