modelled repex is likely to result in an estimate of forecast capex which reasonably reflects the capex criteria. The effect of excluding the opex maintenance intervention quantities from the repex model calibration data is to increase the mean replacement lives derived from the calibration model for towers in corrosion zone B by approximately 6.8 years (to 78.2 years), corrosion zone C by 3.2 years (to 61.1 years), and corrosion zone DEF by 0.8 years (to 45.8 years). We have applied these adjusted mean asset replacement lives for towers in modelling our alternative estimate of repex for the 2017–22 regulatory control period. Our substitute asset replacement lives are set out in below. Table . Powerlink and the AER's forecast average asset replacement lives (years) Powerlink AER draft Powerlink AER final initial decision revised decision Primary asset proposal Sub-category asset proposal asset category asset replacement replacement replacement replacement lives lives lives lives 40.3 46.6 45.0 45.8 Corrosion zone DEF 57.9 65.5 57.9 61.1 Towers Corrosion zone C 71.4 79.9 71.4 78.2 Corrosion zone B 34.2 40.2 35.2 35.2 Circuit breakers 39.8 45.8 40.6 40.6 Isolators/earth switches Primary substation equipment 34.6 40.6 35.1 35.1 Voltage transformers 33.2 39.2 34.2 34.2 Current transformers Secondary systems (bay 20.2 24.7 20.6 20.6 Secondary systems and non-bay) and telecommunications 10.7 10.7 10.7 10.7 Telecommunications 34.3 34.3 34.3 34.3 Substation buildings Buildings and Communications 42.3 42.3 42.3 42.3 infrastructure buildings 50.6 50.6 50.6 50.6 Site infrastructure Source: EMCa, Review of Powerlink's replacement capital expenditure, 2017, p. ii and AER analysis. The extended asset replacement lives for towers set out in Table 6.5, when applied as inputs to Powerlink's repex model, have the effect of deferring the profile of asset replacements forecast by the model and reducing forecast capex in the 2017–22 regulatory control period. The total reduction in forecast repex resulting from the
modelled repex is likely to result in an estimate of forecast capex which reasonably reflects the capex criteria. The effect of excluding the opex maintenance intervention quantities from the repex model calibration data is to increase the mean replacement lives derived from the calibration model for towers in corrosion zone B by approximately 6.8 years (to 78.2 years), corrosion zone C by 3.2 years (to 61.1 years), and corrosion zone DEF by 0.8 years (to 45.8 years). We have applied these adjusted mean asset replacement lives for towers in modelling our alternative estimate of repex for the 2017–22 regulatory control period. Our substitute asset replacement lives are set out in below. Table . Powerlink and the AER's forecast average asset replacement lives (years) Primary asset category Sub-category Powerlink initial proposal asset replacement lives AER draft decision asset replacement lives Powerlink revised proposal replacement lives AER final decision asset replacement lives Towers Corrosion zone DEF 40.3 46.6 45.0 45.8 Corrosion zone C 57.9 65.5 57.9 61.1 Corrosion zone B 71.4 79.9 71.4 78.2 Primary substation equipment Circuit breakers 34.2 40.2 35.2 35.2 Isolators/earth switches 39.8 45.8 40.6 40.6 Voltage transformers 34.6 40.6 35.1 35.1 Current transformers 33.2 39.2 34.2 34.2 Secondary systems and telecommunications Secondary systems (bay and non-bay) 20.2 24.7 20.6 20.6 Telecommunications 10.7 10.7 10.7 10.7 Buildings and infrastructure Substation buildings 34.3 34.3 34.3 34.3 Communications buildings 42.3 42.3 42.3 42.3 Site infrastructure 50.6 50.6 50.6 50.6 Source: EMCa, Review of Powerlink's replacement capital expenditure, 2017, p. ii and AER analysis. The extended asset replacement lives for towers set out in Table 6.5, when applied as inputs to Powerlink's repex model, have the effect of deferring the profile of asset replacements forecast by the model and reducing forecast capex in the 2017–22 regulatory control period. The total reduction in forecast repex resulting from the