About arrester classification and energy withstand testing is introduced: the line discharge classification is replaced by a classification based on repetitive charge transfer rating Q_rs, thermal energy rating Withzz and thermal charge transfer rating Q_th, respectively. The new concept clearly differentiates between impulse and thermal energy handling capability, which is reflected in the test procedures and minimum pass criteria.

The Definitions of these ratings are as follows:

• Thermal Energy Rating, W_th: The energy, given in kJ/kV of U_r, which may be dissipated by an arrester or arrester section in a thermal recovery test without causing a thermal runaway.





• Repetitive Charge Transfer Rating, Q_rs: The charge, given in coulombs (C) in the form of a single event that can be transferred at least 20 times ( at time intervals that allow for cooling to ambient temperature ) through an arrester without causing mechanical failure or unacceptable electrical degradation to the MO resistors.





• Thermal Charge Transfer Rating, Q_th: The charge, given in coulombs (C) that may be transferred through an arrester or arrester section in a thermal recovery test without causing a thermal runaway.





As shown in the table below, Station Class arresters will have a Q_rs and W_th rating. Distribution arresters will have a Q_rs and Q_th rating.