Excitation Systems:
AVR and PSS Testing

Electric Research personnel have performed all types of excitation system testing since 1964. We are well versed in all types of excitation control systems from the early star-wheel voltage regulators onward. Excitation control system testing includes the interactions of all automatic voltage regulator (AVR) functions with the exciter, generator and power system. Of particular interest are the stabilizing functions including the power system stabilizer (PSS) and the excitation limiting functions including maximum and minimum excitation limiting functions. We regularly perform testing onsite to validate that all excitation system functions are operational, to coordinate limiting and protective functions, and to determine or validate models used in stability studies.


Since 1997 there has been a steadily increasing awareness of and commitment to excitation control systems in the electric power industry. Stability issues have been of real concern in the western U.S. since the 60’s when the first PSS was designed and tested on two hydro plants by our personnel. We have been involved in the application and testing of PSS ever since. We have participated (and sometimes chaired) the Institute of Electrical Engineers (IEEE) Power Engineering Society (PES) Excitation System Subcommittee (ESS) task forces to develop and revise the 421 series of standards related to excitation control system. Our focus has often been on the dynamic performance of excitation control systems and the testing to select their parameter settings.

In 1984 we developed an Excitation System Test set. It is a computer-based system that can supply the voltages and currents required by the PT and CT circuits of the excitation control system for testing when the generator is shut down. This test set is very useful for testing excitation control systems during outages for maintenance. This test set originally required a complete model of the excitation control system for the unit under test. In 1999 we discontinued manufacture of this test set. Manufacture was terminated primarily because the system is too complex to be used infrequently. It requires someone well versed in excitation system testing and modeling who performs excitation system testing frequently.



We continue to use this test set to perform testing during full-load, partial-load, no-load and shutdown operation. We are available to assist the electric power industry with training, testing and modeling of all excitation control system equipment. PSS testing requires some testing be performed near full-load. Thus PSS testing is often scheduled just before or just after a maintenance outage so that excitation system testing is completed during the outage and PSS testing is completed both during the outage and just before or after the outage.

Integrating Non-Utility Generation With the Grid

Control and Excitation Systems

Excitation System Test Set