A circuit testing closer is capable of closing a power distribution circuit and interrupting the resulting current at the next current zero. Upon detecting a fault, the circuit testing closer is operable to open contacts to isolate the fault. Next, the circuit testing closer tests the faulted line to determine whether the fault has cleared. The circuit testing closer may generate a first test signal having a first polarity and a second test signal having a second polarity opposite the first polarity. Generation of the second test signal may be limited to occur when the first test signal indicates a fault.