Lightning protection means for XLPE-covered conductors as integral parts of the line insulation

Overhead power lines with XLPE-covered conductors must be protected against flashover due to lightning. Applying spark gaps in all phases causes a short-circuit between phases which may not comply with the power quality requirements. Substituting the gaps by arresters is a questionable solution due to the expected energy stresses on the arresters. This paper presents a combined solution applicable to networks with nonsolid grounded neutrals. The top conductor is protected by spark gaps and acts as a shielding wire for the two other phase conductors. Arresters are used to prevent backflashover. The energy stresses on these arresters are very moderate except when shielding failure occurs. It is, however, possible to obtain an acceptable arrester failure rate by keeping the risk of shielding failure sufficiently low. Several practical designs of the pole top are discussed and the potentially most attractive ones use arresters whose casing has sufficient mechanical strength to eliminate the need for the conventional line-insulators