The Earth Fault Protection Card was developed to fulfil two critical safety functions for solar inverter systems:
1. Perform a sequence of eight consecutive earth resistance measurements on the inverter's solar array as a mandatory precondition for startup.
2. Continuously monitor earth leakage currents during inverter operation.
Due to strict certification restrictions, the entire design had to exclude microcontrollers. This constraint led to a fully hardware-based implementation using discrete digital logic and analogue signal processing.
A custom-built discrete logic state machine was engineered to perform the earth resistance measurement sequence, validate each measurement, and store the pass/fail result. The overall test passes only if all eight individual measurements meet the required criteria.
Electron Artz led the complete design from the ground up, with some design collaboration with Ario Metapower. The initial version passed certification successfully - no revisions required.
Ario MetaPower approached Electron Artz for design assistance with the electronic hardware of their 200kW inverter. Electron Artz was tasked with reviewing, redesigning, and adding new functionality to two of the three boards in the inverter control stack. Additionally, we were commissioned to design two entirely new boards for the inverter from the ground up.
The Earth Fault Protection Card was one of these new boards, developed completely from scratch.
