Sch 1E para 4 Permissible effect of transient electromagnetic phenomena
The effect of an electromagnetic disturbance on an electrical energy meter shall be such that during and immediately after a disturbance: — any output intended for testing the accuracy of the meter does not produce pulses or signals corresponding to an energy of more than the critical change value, and in reasonable time after the disturbance the meter shall: — recover to operate within the MPE limits, and — have all measurement functions safeguarded, and — allow recovery of all measurement data present prior to the disturbance, and — not indicate a change in the registered energy of more than the critical change value. (m being the number of measuring elements of the meter, Un in Volts and Imax in Amps).