Lessons Learned in Static VAR Compensator Protection
Aaron Findley, Mychal Hoffman POWER Engineers, Inc.
Dan Sullivan, Jan Paramalingam Mitsubishi Electric Power Product Inc.
Presented by: Aaron Findley Presentation Contents i. Introduction to SVC’s ii. SVC components iii. SVC protection and lessons learned iv. Summary v. Questions Introduction to SVCs
• Static var compensators are shunt-connected var generators or absorbers • Outputs are varied to control specific reactive power flow • Comprised of capacitors an reactors that are placed in and out of service using power electronic switching devices • Term “static” no moving or rotating main components Introduction to SVCs
The common types of reactive power devices that make up all or part of static var system include: • Thyristor-switched reactor (TSR) • Thyristor-controlled reactor (TCR) • Thyristor-switched capacitor (TSC) • TSCs and TCRs are commonly used Introduction to SVCs
• Capable of controlling individual phase voltages of the buses to which they are connected • They can be used for control of negative- sequence as well as positive-sequence voltage deviations • Primarily used for three phase control of the power system Introduction to SVCs
• Ideally suited for rapid control of voltage • They provide faster response time than mechanical switched devices • They Provide continuous and smooth control of VARS Components of an SVC Components of an SVC system TSC
TSC: Thyristor Switched Capacitors, • Capacitor banks switched on and off by using Thyristors • In three phase applications, the units are connected in delta • Integral cycle control is used where a change can be made every half cycle • Avoid switching when bus an capacitor voltages are unequal TSC TCR
• A reactor in series with a bidirectional switch • Anti‐parallel thyristors conduct on alternate half‐cycles depending on firing angle • Reactors are switched on for a controllable fraction of every half cycle • Will require AC filtering because the non‐ sinusoidal current draw results in harmonics. TCR
Relay event report showing TCR firing delay. The reactive current magnitude decreases as the firing delay increases Harmonics