EXPERIMENTAL-ANALYSIS OF A DC BUCKING MOTOR BLOCKING GEOMAGNETICALLY INDUCED CURRENTS

An experimental study investigates the performance of a dc bucking motor for the blocking of geomagnetically induced currents (GICs) within a 3 kVA/416 V three-phase distribution feeder. This blocking method consists of connecting a separately excited de motor between neutral and ground of a Y-grounded transformer consisting of a bank of three single-phase transformers. Losses and currents of the transformer and the blocking device are measured at no-load, rated-load, unbalanced-load and line-to-neutral short circuit conditions without and with GICs. Thereafter, the dc, ad and total lambda-iota characteristics of one single-phase transformer of the above-mentioned transformer bank are simultaneously measured using an arbitrary waveform generator, a power amplifier and a digital data acquisition network. These lambda-iota characteristics -where the dc bias current is a parameter- are then used to model a single-phase transformer under de bias current conditions (e.g., assumed GICs) and to calculate voltages and currents of a single-phase transformer when subjected to GICs. The simulated signals are then compared with measured time functions.