In DC traction systems impermissible touch voltages may occur between the return circuit and the structure earth due to operational and short-circuit currents. In this case, a voltage-limiting device must be used between the return circuit and the structure earth in accordance with IEC 62128-1 / EN 50122-1.

The Sitras SCD reduces excessively high voltages by reliably short-circuiting the return circuit and structure earth temporarily. Furthermore, the formation of stray currents is minimized by automatic opening of the short-circuiting device.