The relationship between virtual time and quality factor for heavy-current test circuits

The use of deviations in virtual time for plotting the time-current characteristics and evaluating the thermal effect of the DC component of a fault current is discussed. The relationship between the virtual-time deviation, the initial EMF phase making angle and the Q factor is used as the basis of a newly developed method for evaluation of the Q factor. This method is particularly useful in the range of higher values of Q, where other methods are not as efficient. For example, the most common DC component damping method is very vulnerable to even small errors in the estimation of the value of this component. In the method presented here, the main contributing factor is that the evaluation of Q is based on measuring the constant component of the virtual-time deviation, which in turn is directly proportional to the time constant of the circuit. The only major shortcoming of the method is the need to maintain the test current until the quasi-steady state is reached