Report

Nuttall Consulting Purpose overview of the form and use of the AER’s augex tool Not Detailed reference material on the underlying spreadsheets Defence of the tool’s regulatory role and suitability Nuttall Consulting Summary Background Augex model data requirements Overview of workbook – augex modelling tool Overview of augmentation algorithm Discussion of issues raised Nuttall Consulting Nuttall Consulting Background – capex category Capex driver Demand driven: customer connection Capex activity Replacement Additional assets replacement and development of assets to facilitate the connection of customers Augex tool Demand driven: augmentation replacement and development of network assets to increase the capacity of the network Repex tool Non-demand driven replacement of aged assets with modern equivalents Nuttall Consulting installation of new assets Background - key aims Regulatory tool NOT planning/management tool Should account for main driver at aggregate level but not concerned with excessive detail Allow intra- and inter-company comparisons Targeting of matters for detailed review Development of benchmarks But not intended to determine specific network constraints and solutions Nuttall Consulting Overview Similar in form to repex tool Similar to tools used by ESV and NSPs Asset state • network utilisation and capacity • growth in peak demand Outputs • forecast capacity • forecast costs • forecast utilisation Planning parameters • utilisation thresholds • augmentation costs Nuttall Consulting Overview Tool is spreadsheet based - uses VBA functions Does not rely upon proprietary – or “black box” – algorithms Uses probability model – to apply utilisation threshold relatively simple to independently verify Asset utilisation = peak loading / normal rating Nuttall Consulting Anticipated application Augex tool assessment 1 - Base-case 2 - Calibration 3 - Comparison • Prepare individual DNSP models based upon DNSP data • Derive planning parameters from actual historical information of DNSP • Prepare individual DNSP calibration models • Derive benchmarks parameters based upon set of DNSPs’ calibrated planning parameters • Prepare individual DNSP benchmark models inform other elements of the review for example, targeting matters for more detailed review, set expenditure allowance Nuttall Consulting Nuttall Consulting Network representation - segments Multiple network segments used to improve accuracy allows for differences between networks reduce impact of aggregation e.g. differences in planning parameters Individual segments represent typical planning components sub-transmission lines – load type and/or arrangements sub-transmission/zone substations – load type and/or transformer number distribution feeder – load type distribution substations – load type 15 – 30 separate segments Nuttall Consulting Network representation - grouping Each network segment must be assigned to a group allows aggregation for analysis and reporting Example distribution groups Sub-transmission lines CBD distribution feeders CBD distribution substations Sub-transmission substations Urban distribution feeders Urban distribution substations Zone substations Short rural distribution feeders Short rural distribution substations Long rural distribution feeders Long rural distribution substations Nuttall Consulting Segment input data For each network segment 1. Asset state data a. b. Utilisation profile – array of the capacity (MVA) of assets at utilisations (0% to 151% - in 1% increments) Utilisation annual growth rate – %pa average over study period 2. Planning parameters a) b) c) Utilisation threshold – mean and standard deviation (assumes a normal distribution) Capacity factor – capacity added = capacity factor x capacity requiring augmentation Augmentation unit cost - (k$ per MVA of capacity) Nuttall Consulting Data – asset status Obtain: loading, rating, type and growth data Form of data required: loadings, ratings, types, should reflect actual data individual components: sub-transmission lines and substations, zone substations, and distribution feeders grouping of data for distribution substations (and LV feeders?) latest loading and rating data is used to develop utilisation profile input other actual data is used to assess changes (calibration) Nuttall Consulting Data – asset status General comments Actual maximum demand should exclude abnormal operating conditions Maximum demand estimate acceptable if not directly measured Distribution feeders – trunk model maximum demand at feeder exit rating of main trunk section Distribution substations expect segments to be based upon load type or categories of substation capacity or substations type Demand growth rates – most appropriate that are available for category Nuttall Consulting Data – capex and capacity Obtain: historical and future capex and capacity Form of data required: Capex should be exclusive of corporate overheads Unmodelled capex – separately identify augmentation capex that is not considered to be related to utilisation and peak demand growth Assuming there will be an “augmentation” capex category in the regulatory reporting requirements – overall capex should be reconcilable to this category The type of capacity should reflect rating types defined for asset status Capex ideally should be “as commissioned” Nuttall Consulting Supporting information Explanations of data sources, calculations, assumptions for tool data inputs rationale for segments if defined by NSP basis of asset status data - maximum demand, ratings, growth rates derivation of planning parameters Nuttall Consulting Possible other supporting information Other responses to aid understanding of data Inclusions and exclusions in capex actual development costs, direct project analysis/planning costs, other costs allocated to the project Capex-capacity allocations rules it is expected that internal systems may not align to AER groups Explanation of unmodelled capex Project/program descriptions, drivers, outcome on capacity Comparability with other DNSPs Differences that may impact augmentation requirements – utilisation levels, project types and costs Nuttall Consulting Nuttall Consulting workbook structure Input sheets Model initialisation data sheet – “Tables” segment data input sheet – “Asset data” Output sheets Asset category summary sheet – “Utilisation profile summary” Augmentation forecast sheet – “aug forecast” Chart sheets Utilisation profile – “utilisation profile chart” Augmentation forecast – “Forecast Ch1” and “Forecast Ch2” Internal calculation sheets Nuttall Consulting Overview of demo model Nuttall Consulting See handbook for more detailed reference material Nuttall Consulting Nuttall Consulting Forecasting – for each segment Figure 1 augmentation algorithm utilisation profile and demand growth probabilistic model to account for variations in the threshold capacity requiring augmentation (probabilistic model) utilisation threshold (similar to asset lives in repex model) capacity added capacity factor expenditure augmentation unit cost Nuttall Consulting VBA function Array function =aug_calc(utilisation profile index, capacity profile, growth, capacity factor, utilisation threshold, SD, method, years) Inputs utilisation profile index – array of utilisation (%) increments capacity profile – array of capacity (MVA) matched to utilisation profile index growth – average per annum compound growth in peak demand (%) capacity factor – as discussed utilisation threshold – mean utilisation at augmentation point (%) SD – standard deviation of utilisation at augmentation point (%) method – augmentation algorithm method (only 1 at this time) Years – number of years for forecast Outputs Array of forecast capacity added by year Array of forecast average utilisation by year Nuttall Consulting VBA function – worked example Assume a network segment is defined in the model Where – utilisation threshold Mean utilisation threshold = 65% SD of threshold = 5% Capacity factor – 0.5 (i.e. add 1 MVA for every 2 MVA requiring augmentation) Augmentation cost = $1,000 per MVA added Nuttall Consulting VBA function – worked example VBA function steps through each element of the utilisation profile to prepare a forecast for the existing capacity at that utilisation level That is, the capacity that has survived to that utilisation level For each element of capacity in the utilisation profile Step 1 – calculate for each forecast year the amount of capacity requiring augmentation (the probabilistic calculation) Step 2 – calculate the amount of capacity to be added (using the capacity factor) Post-function calculation - expenditure forecasts calculated outside of VBA function as - capacity added x augmentation cost For example, assume we still have 100 MVA that is utilised at 60% Nuttall Consulting Step 1 – probability calculation unconditional CRA CRA, given survived to be utilised at 60% 10.0 CRA (MVA) 8.0 6.0 4.0 2.0 0.0 20 30 40 50 60 70 80 90 100 utilisation (%) Proportion of capacity requiring augmentation (CRA) at utilisation, u, given the capacity has survived to be utilised at 60% = , ℎ 60% Nuttall Consulting Step 1 – transform u to year unaugmented utilisation 75 utilisation (%) 70 65 60 55 50 0 1 2 3 14 CRA (MVA) 12 4 5 7 capacity8 requiring9 augmentation 10 6 forecast year 10 8 6 4 2 0 1 2 3 4 5 6 7 8 9 forecast year using peak demand growth for that segment – assume here it is 2% pa. transform the x-axis from utilisation to forecast year Nuttall Consulting 10 Step 2 – capacity added For each forecast year Using forecast capacity requiring augmentation (CRA) Capacity added = CRA x capacity factor For example in year 1, CAR is 7.7 MVA (utilised at 61.2%) Capacity added = 7.7 MVA x 0.5 = 3.9 MVA Utilisation of augmented capacity = demand associated with CAR / (CAR + capacity added) = (7.7 x 61.2%) / (7.7 +3.9) = 41% utilisation Return to step 1 to calculate any later augmentation associated with this augmented capacity. Nuttall Consulting Nuttall Consulting Common issues raised Anomaly for high growth rates More detail in manual HV trunk feeder model Use of N-1 rating rather than N for utilisation Sensitivity to utilisation threshold Including LV segments Clarifications on modelling certain circumstances Cross feeder ties Non-trunk HV feeder augmentations Projects with long lead times Meshed networks Preparing $/MVA for different projects Weather correcting utilisation Augmenting one segment to address constraints on other segments Nuttall Consulting Nuttall Consulting