Abstruct -This paper describes what automatic generation control (AGC) might be expected to do, and what may not be possible or expedient for it to do. The purposes and objectives of AGC are limited by physical elements involved in the process and, hence, the relevant characteristics of these elements are described. For reasons given in this paper, it is desired that AGC act slowly and deliberately over tens of seconds or a few minutes. From a perspective of utility operations, there is no particular economic or control purpose served by speeding up the AGC action.By this Task Force paper, the System Control Subcommittee is providing a resource to the power engineering community to help guide research into topics related to AGC.
Thls paper I s one o f a series presented on behalf o f the System Operations Subcomittee w l t h the i n t e n t o f focusing industry a t t e n t l o n on current problems faced by e l e c t r l c u t i l l t l e s I n the operation o f the bulk power supply system. Five short note reports are presented dealing w i t h various cost aspects associated w t t h Automatic Generation Control (AGC), Inadvertent energy and tlme e r r o r . The f i r s t r e p o r t provides a general overvlew o f some o f t h e AGC operatlng costs t o consider. Q u a n t i f i c a t i o n o f some o f these operatlng costs I s o u t l i n e d i n t h e second report. Report number three deals w l t h ' t h e 'reserve l l a b l l l t y ' and the ' r a t e t o c o n t r o l ' costs when purchasing AGC c a p a b l l l t y . I n r e p o r t four, economlc Implications o f inadvertent energy are consldered. I n t h e f i n a l report. t h e cost impact o f time e r r o r and tlme e r r o r c o r r e c t l o n are presented.
The authors whole-heartedly agree that voltage sags are of critical concern to certain customers, and STSs are candidate solutions for voltage sag mitigation. In fact, since this paper 1 has been submitted, the authors have integrated comprehensive voltage sag analysis capabilities to their predictive reliability assessment tool. This includes the voltage sag impact of STSs.To model voltage sags, each customer is assigned a customized set of voltage sag levels (e.g., sag to 80%, sag to 70%, and sag to 60%). When a fault occurs on a component, the voltage profile is computed for the entire system (three-phase bolted faults are assumed). If a customer sags below a specified level and is not subsequently interrupted, that customer's "sag index" for that voltage level is incremented by the fault frequency. The sags results for a customer would look something like: 12.7 sags below 80%, 4.6 sags below 70%, and 2.8 sags below 60%.The impact of STSs on sags is handled in the same manner as interruptions. The only twist is that the voltage level at the STS secondary must be above a specified threshold for the transfer to occur. This provides a reasonable model of the STSs impact on a customer's complete voltage sag profile.As the discussers have correctly identified, a fault on a feeder will cause a voltage sag not only on itself, but on other feeders connected to the same bus at the substation. This means that all feeders on a low voltage bus need to be included to accurately model voltage sags. In addition, substation transformers must be modeled so that voltage sags can be computed accurately.
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