The ISA DRTS 6 Automatic Relay Test Set is a high-precision, multi-functional testing solution for protection relays and substation devices. Featuring automatic control, powerful software, and reliable three-phase outputs, it's ideal for modern power system maintenance. Unlike most 3-phase relays test sets, ISA have developed an. All ISA Test and Measurement Instruments have been designed to be used in severe environment such as high voltage substations and heavy industry plants. Item comes new from. pect to the standard model.