Power system operations and control: Difference between revisions

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Minutes-ahead operation: Expanding article
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== Minutes-ahead operation ==
In the minutes prior to the delivery, a system operator is using the [[power-flow study]] algorithms in order to find the [[optimal power flow]]. At this stage the goal is reliability ("security") of the supply.{{sfn|Conejo|Baringo|2017|p=10}} The practical electric networks are too complex to perform the calculations by hand, so from 1920s the calculations were automated, at first in the form of specially-built [[analog computer]]s, so called ''[[Network analyzer (AC power)|network analyzers]]'', replaced by digital computers in the 1960s.
 
== Minutes-after control ==
The ''secondary control'' is used to restore the system frequency after a disturbance, with adjustments made by the balancing authority control computer (this is typically referred to as [[load-frequency control]] or [[automatic generation control]]) an manual actions taken by the balancing authority staff. Secondary control uses both the [[Spinning reserve|spinning]] and non-spinning reserves, with balancing services deployed within minutes after disturbance (hydropower plants are capable of an even faster reaction).{{sfn|NERC|2011|pp=12-13}}
 
== Seconds-after control ==
The ''primary control'' is engaged automatically withing seconds after the frequency disturbance. Primary control stabilizes the situation, but does not return the conditions to the normal and is applied both to the generation side (where the [[Governor (device)|governor]] adjusts the power of the [[Prime mover (engine)|prime mover]]) and to the load, where:{{sfn|NERC|2011|p=12}}
* induction motors self-adjust (lower frequency lower the energy use);
* under-frequency relays disconnect [[interruptible load]]s;
* [[ancillary services]] are engaged.
 
== References ==