Limits of allowed ampacity of EHV/UHV overhead lines with ACSR and ACCC conductors, in the specific climatic conditions of the Slovak Republic

摘要

Overhead lines of SR have so far been built exclusively on the traditional ACSR rope conductors. Their mechanical and electrical properties are nor optimal either efficient in terms of increasing transmission capability OHL-overhead lines, intended mainly for the power output from large nuclear sources, but neither for our transit line integrated into ENTSO-E. This is due to a combination of material constants of steel and aluminium, and because of hysteresis of shape stress-strain diagram of the combined ACSR rope structure. In the inelastic area arise permanent geometric subsidence and metallurgical creep of ACSR rope conductors. So while their long-term loading this would occur in: gain of elongation +Δε_(ACSR) (%), gain maximum sag +Δf_(ACSR_max) (m), decrease the minimum sparkover distance of ACSR phases from the ground -Δh_(ACSR_min) (m), and thus by forced reducing the allowed current capacity -ΔI_(ACSR_allowed) (A). This is reflected by decreasing the transmission capability -ΔS_(OHL) (MVA) OHL, which may be lower, as derived from the instantaneous allowed current capacity ACSR conductors I_(ACSR_allowed) (A), at less than the minimum allowed spark-over distance h_(ACSR_min) (m). This presents a potential problem in elderly OHL designed according to standard [2], which should be in accordance with [3] operate in permanent allowed conductor temperature T_(cond_allowed) = 80 (°C). OHL transmission capability is therefore inter alia function of distance hACSR_min (m) lower phases from the ground, and must be able to predict at the OHL design stage, because latently growing by permanent inelastic elongation of ACSR conductors throughout the lifetime of the OHL. Replacement of steel core in ACSR conductor by composite core in ACCC conductor, led to the decrease of the sag Δf_(ACCC_max) (m) in area behind knee-point-temperature, removed the magnetization non-existent steel core, and remove the AC resistance increase of steel core magnetization ACSR conductor ΔR_(ACSR_ac) = 0 (Ω.km~(-1)), so not incurred reduce the transmission capability of the OHL -ΔS_(OHL) (MVA) as in conventional ACSR rope conductors.