The type B differential relay is a device, compliant with IEC 60947-2 annex M, capable of detecting a residual direct current to earth, which could be harmful or dangerous. This device must be associated with a magnetothermal or electronic circuit breaker, sized to interrupt this dangerous residual current and guarantee adequate protection against overload and short circuit. The differential relay is in turn connected to a CT that detects the leakage currents in the plants up to 630 A. The associated circuit breaker is tripped by an undervoltage release (UVR) or a current release (ST). The range of type B differential relays consists of 2 solutions with 230Vac or 24Vdc and rated current up to 63A. Type B differential relays can be used in circuits with frequency converters, medical devices (such as X-RAY or TAC machines), inverters for photovoltaic systems, lift electric lines, laboratory test equipment, industrial cranes, crafts and trade, mechanical workshop (arc welders, numerical control machines), three-phase charging station for electric cars, three-phase UPS.