CT saturation calculations - are they applicable in the modern world? - Part III, low-ratio, high-current CT/microprocessor relay comparisons at a high-current testing laboratory

Part III is an extension of the Part II testing effort, but with relay manufacturers providing, commissioning, and configuring the relays for the high-current test laboratory activities. Part III provides high-current testing laboratory results for multiple 50 kA and 63 kA tests involving several typical low-ratio switchgear CTpsilas (with typical burdens) and microprocessor feeder relay instantaneous 50 elements. Saturated low-ratio CT graphical waveform plots obtained from a series of tests are analyzed. Microprocessor relay 50 element true rms and bipolar peak detector relay filter algorithm types are considered. Discussions also include power system concerns resulting from delayed microprocessor relay instantaneous 50 element operation, i.e., arc flash PPE recommendations, relay coordination selectivity, equipment. Comments about electro-mechanical instantaneous relays are included.