Motor Load Models for Fault-Induced Delayed Voltage Recovery Studies in Bulk Transmission Systems

As power systems have become more heavily loaded, infrastructure investments have declined, and high-power factor generation has increased, exposures to fault-induced delayed voltage recovery problems and sustained low voltages have increased. The issues are exacerbated by an ever-increasing penetration of induction motor loads. These motor loads are a major driver of these types of voltage control issues and properly representing them in bulk power system studies is important. All existing system simulation packages offer dynamic motor models ranging from complete time-domain options to so-called “reduced order” models where some of the motor electromagnetic transient response characteristics are neglected. In any case, the dynamic model for a single motor is typically from
$\mathbf{3^{rd}}$
to
$\boldsymbol{5^{\text{th}}}$
order and may involve small time constants. Performing system simulations where tens of thousands of such motors are included is very time consuming and often results in a reduced number of contingency events being evaluated which can of course lead to an operational degradation of system reliability. The purpose of this paper is to present an analysis and evaluation of two motor models that could be used for these types of studies where one is the most detailed practical option and the other is the most simple. The objective is to compare each model's performance in simulation scenarios associated with bulk transmission system voltage dynamics.