A New Transmission Line Parameter Estimation Technique and Its Impact on Fault Localization

Parameters of an underground cable (UGC) line are highly prone to change with aging and atmospheric conditions, which severely hamper the performances of some protection algorithms such as fault localization methods. Online parameter estimation is the key to solve this problem. Here, a new noniterative transmission line parameter estimation (TLPE) technique is proposed by deriving the expressions of line resistance, inductance, and capacitance mathematically in terms of time-domain voltages and currents. From these derivations, line parameters are directly obtained using only one-cycle prefault signals. To verify its utility, this TLPE technique is applied for locating faults on a UGC line by the lowest potential point search method, which becomes very simple with the help of estimated parameters as it does not need to solve any complex constraint-based optimization problem. Extensive simulations are carried out to verify the proposed method and estimated parameters are found accurate for various loading conditions, noises, synchronization errors, data acquisition errors, and line types. Moreover, comparison with existing TLPE methods and verification with field data justify its utility. Appreciable accuracy is also achieved in fault localization, which does not depreciate with cable aging because of usage of line parameters estimated from prefault values of the signals utilized for locating faults.