CIRCUIT TESTING AND DIAGNOSIS

Systems (400; 500) and methods (600) for testing a lightning protection circuit are provided. Aspects include providing an alternating current (AC) test signal source (404; 504) coupled to a circuit under test (420), the circuit under test comprising a lightning protection circuit (202) having a threshold voltage, a first filter (212), and a second filter (210), providing a direct current (DC) voltage supply (406) in series with a filtering device (410), the filtering device coupled to the AC test signal source, providing a first capacitor (408) coupled between the AC test signal source and the circuit under test, operating the DC voltage supply and the AC test signal source to provide a first test signal to the circuit under test, wherein the first test signal comprise a first voltage that exceeds the threshold voltage, measuring a first impedance of the circuit under test responsive to providing the first test signal, wherein the first impedance corresponds to the first filter.