DETERMINATION OF THE ACTUAL PQ DIAGRAM OF THEHYDROGENERATORS, BEING IN SERVICE, IN ORDER TOESTABLISH THEIR MAXIMUM OPERATING DOMAINS ANDTHEIR CAPACITY TO PROVIDE SYSTEM SERVICES

摘要

The theoretical PQ diagram represents the diagram of the reactive power versus the active power of a hydrogenerator, deduced from the phasorial diagram of the synchronous machine with salient poles. The actual PQ diagram is in fact a thermal diagram, in which the main theoretical curves represent the isotherms of the maximum admissible temperatures of the different parts of the electrical generator. Determination of the actual PQ diagram of the hydrogenerators being in service is performed in steady state operation, by measuring the maximum overheating appearing in the stator and rotor windings, in the stator core and in the frontal teeth sheets of the stator core. On the actual diagram, the secondary band is delimitated, where the produced or absorbed reactive power is paid, because the operation in this region is done with higher strains and costs. Measurements were performed on 25 hydrogenerators, with powers between 27-170 MW.