Series Resistance Method of Increasing Transient Stability Limit Series Resistance Inserted into Generator Circuit Loads Machines During Fault and Retards Subsequent Overswing

This paper considers the effect of resistance inserted in series with generators during and after a short circuit to increase the transient stability limit. The series resistance loads the machines during a fault and greatly reduces the normal tendency to overspeed. After the fault has been cleared the series resistance exerts a powerful influence in retarding excessive over-swing by taking advantage of the low generator stored energy relative to that of the load center. It is shown that by using series resistance a typical hydro system can maintain synchronism through a three-phase fault with speeds of circuit breaker and relay operation now available. A three-phase resistor normally short-circuited by a circuit breaker and connected into the neutral of each generator provides the most desirable arrangement. The cost will generally be much lower than the combination of other measures commonly taken such as high inertia generators, low reactance of generators and transformers, damper windings, transformer neutral impedance, special simultaneous relay schemes or other remedial measures such as lightning proof lines, and the expenditure can be deferred until it is justified by operating experience.