APPLICATION OF INERTIAL LOAD TO A LOSS OF GENERATOR POSTMORTEM

ABSTRACT

The inertial load flow technique 2] is applied to a dynamic equivalent 1] derived from a NERC (North American Electric Reliability Council) data base to compute maximum tie line power flows for a 1980 MW loss of generation at the Nanticoke station in the Ontario Hydro system. The results were compared with a transient stability simulation and recorded tie line power and frequency measurements. The inertial load flow results were more accurate in capturing the filtered measurements of power flows during the first three to five seconds after a loss of generation contingency than the transient stability simulation. The transient stability simulation was shown to contain both synchronizing oscillations between generators as well as the quasi steady-state behavior captured by the filtered power measurements and inertial load flow.

The inertial load flow is an excellent tool for estimating proximity to voltage collapse since the field current limiters on exciters utilize filtered measurements of the inertial response that occurs 3-5 seconds after a loss of generation contingency. The loss of voltage control and reactive generation supply due to action of field current limiters is a principle cause of loss of voltage stability in power systems. The inertial response is shown to capture a filtered estimate of the peak of the deceleration wave that propagates from the point of disturbance and would indicate whether the filtered estimate of these peak real power flows would incur sufficient filtered generator field current levels to cause field current limiters to act. Generator field current levels rise in an attempt to counteract voltage decline and increase in reactive losses caused by the peak power flows that are observed in the inertial response. The action of the field current limiter reduces field current and reactive supply to prevent thermal damage to the generator. The action of field current limiters initiates the voltage decline that can result in voltage collapse.