What is the difference between Type A and Type B RCD protection for home solar inverter systems?

Type A residual current devices (RCDs) are designed to detect sinusoidal alternating residual currents and pulsating direct residual currents up to 6 mA, making them suitable for most single-phase inverters with galvanic isolation. Type B RCDs, defined in IEC 62423, additionally detect smooth DC residual currents and high-frequency AC currents up to 150 kHz, which are characteristic of transformerless inverters and battery storage systems. The selection depends on the inverter topology: transformerless PV inverters mandate Type B RCDs on the AC side to handle potential DC fault currents exceeding 6 mA, as specified in IEC 60364-7-712 for photovoltaic power supply systems.