This part of IEC 60099 provides information, guidance, and recommendations for the
selection and application of surge arresters to be used in three-phase systems with nominal
voltages above 1 kV. It applies to gapless metal-oxide surge arresters as defined in
IEC 60099-4, to surge arresters containing both series and parallel gapped structure – rated
52 kV and less as defined in IEC 60099-6 and metal-oxide surge arresters with external series
gap for overhead transmission and distribution lines (EGLA) as defined in IEC 60099-8. In
Annex J, some aspects regarding the old type of SiC gapped arresters are discussed.
Surge arrester residual voltage is a major parameter to which most users have paid a lot of
attention to when selecting the type and rating. Typical maximum residual voltages are given
in Annex F. It is likely, however, that for some systems, or in some countries, the
requirements on system reliability and design are sufficiently uniform, so that the
recommendations of the present standard may lead to the definition of narrow ranges of
arresters. The user of surge arresters will, in that case, not be required to apply the whole
process introduced here to any new installation and the selection of characteristics resulting
from prior practice may be continued.
Annexes H and I present comparisons and calculations between old line discharge
classification and new charge classification.