Summation current transformer for mixed AC/DC residual current detection
The Siemens 5SV8703-2KK is a SENTRON summation current transformer designed for Type B residual current monitoring — meaning it detects smooth DC residual currents as well as AC and pulsed DC, which standard Type A devices miss. Rated for 330 A continuous through the primary window and a 120 mm internal diameter, it fits around main conductors or busbars in distribution panels where mixed-frequency loads (VFDs, UPS, EV chargers) generate DC fault currents. Surge withstand is 8 kV, which keeps the secondary electronics safe during line-side transients.
Panel integration and wiring constraints
Mounting dimensions are 210 mm wide by 191.5 mm deep by 67 mm tall. The plug-in terminal connection accepts up to 6 conductors of 0.75 mm² each, so secondary wiring to the RCD or evaluation unit stays within a single terminal block. Maximum secondary wire length is 10 m — keep that in mind when locating the transformer relative to the trip unit. Operating ambient range is -10 °C to 55 °C with up to 95 % humidity, so it handles unconditioned electrical rooms within that band.