Experimental study was carried out for classified a mechanism of failure of low-voltage electronic Watt-Hour Meters. As the results, the mechanism of failure of electronic meters is clarified into two patterns. One is due to the magnetic field generated by lightning current passing through the inside of an electronic meter. The other is due to the blow out of electric wire caused by lightning current flowing into the power supply circuit for processing unit. For these failure mechanisms, following counter measures were clarified. One is that a magnetic shielding measure using a metallic plate covering the processing unit was effective for reducing the magnetic field. The other measure is that a relocation of the ZnO device in the electronic meter was effective for reducing the lightning current flowing into the power supply circuit.