Siemens 5SV8111-4KK — SENTRON modular RCD, Type B, 24 V DC
The Siemens 5SV8111-4KK is a modular residual current device from the SENTRON family, designed as a digital Type B unit. It operates on a 24 V DC supply (19.2–28.8 V DC range) and is rated for a residual current of 30 mA across a frequency range of 0–2000 Hz, making it suitable for detecting all types of fault currents including smooth DC and high-frequency AC components. Type B detection covers AC, pulsating DC, smooth DC, and high-frequency residual currents up to 2000 Hz — essential for variable-speed drives, UPS systems, and other non-linear loads where standard Type A RCDs may not trip. The unit mounts on a DIN rail (fastening method: DIN rail) and occupies a compact footprint: 36 mm wide, 85 mm high, 64 mm deep. Screw-type terminals accept AWG 24–14 conductors with a stripped length of 8 mm.
The 30 mA rated residual current is the standard threshold for personal protection against electric shock. The 0–2000 Hz frequency range covers fault currents from modern power electronics. The integrated LCD provides a real-time residual current display, and the error memory logs trip events — useful for fault-finding on intermittent earth faults. Password protection prevents unauthorized changes to the trip threshold or time delay settings. Time delay is adjustable from 0.06 s (initial value) up to 10 s (full-scale value), allowing selective coordination with downstream RCDs or upstream breakers.
IP30 on the front face, IP20 at the terminals — adequate for enclosed distribution boards; not rated for washdown environments. External summation current transformers (CTs) are required — compatible types listed include 5SV8701-2KK, 5SV8701-2KP, 5SV8702-2KK, 5SV8702-2KP, 5SV8703-2KK, and 5SV8704-2KK. Maximum wire length from CT to the RCD is 10 m. Power loss is 6.5 VA maximum at the rated supply voltage — negligible thermal impact in a crowded enclosure.