Water and Energy Abstracts

The rapid growth in generation and associated transmission network has enormously increased the complexity of operation and control of interconnected power system. With increased interconnection, a disturbance in one part often leads to grid collapse. After such blackouts, system studies are carried out to analyze the occurrence. The studies may reaveal deficiencies in design, mal-operation of elements or improper coordination. However many times these simulation studies may not indicate the true picture as the data used for the studies are not actual measured data. These studies are based on the design data given by manufacturer or typical data given in publication which may vary widely from actual site data. Generators are the heart of interconnected power system and understanding its behaviour under all conditions has always been a challenge to power system engineers. The major generator parameters which influence system stability are: - Inertia constant (H), sub-transient resistance (X”_d); transient reactance (X’_d), synchronous reactance (X_d), direct axis open circuit time constant (T’_d0), -Excitation system; and - Governor system. In 1996, after the western part of US collapsed, WSCC (Western System Coordination Council) insisted on testing of generator units to obtain reliable generator parameters (Generator and exciter including PSS, governor-turbine). The testing helped in validating design data and thereby improving the predictability of system performance during system contingencies. Companies like GE performed tests at site and derived unit parameters for use in dynamic stability studies. Since these tests are performed at low power levels, risk to the machines is also low. On the same vein, we have recently conducted tests on 250 MW unit in one of our thermal power plants at Dahanu, India. Following tests were conducted: -Saturation Curve Measurement (OCC). -Short circuit tests (SCC). -V-curve measurement. -Partial load trip test. -No load, zero power factor trip test with AVR in Manual mode.