The Siemens SENTRON 5SV8706-0KK is a summation current transformer, type A, designed for AC systems. It carries a 630 A rated operational current and a 210 mm internal diameter, meaning it wraps around multiple conductors to sum their residual currents for downstream RCD monitoring. The 210 mm opening accommodates large cable bundles or busbars common in main distribution panels.
The minimum detectable residual current is 300 mA — this sets the threshold for the RCD or relay it feeds; a 300 mA Idn is typical for fire-prevention or general protection in commercial/industrial panels, not for personnel shock protection (which requires 30 mA or lower). Surge voltage withstand is 4 kV, consistent with basic insulation coordination for a transformer feeding electronic trip units. The screw-type terminals accept 0.13 to 2.1 mm² conductors, which is fine for the control wiring to the RCD module; the main power conductors pass through the 210 mm window, not through the terminals.
Dimensions are 299 mm wide, 284 mm deep, and 33 mm tall. The 33 mm height is slim for a 210 mm ID transformer — it fits into tight horizontal cable-raceway sections or onto a backplate with minimal vertical clearance. The 10 m maximum wire length from the transformer to the evaluation unit (RCD/relay) defines the practical separation distance in the panel; keep the secondary wiring under that limit to avoid measurement errors.