Augmentation capex regulatory tool

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”

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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

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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%

=

𝑢𝑛𝑐𝑜𝑛𝑑𝑖𝑡𝑖𝑜𝑛𝑎𝑙 𝑝𝑟𝑜𝑏𝑎𝑏𝑖𝑙𝑖𝑡𝑦 𝑓𝑜𝑟 𝑎𝑢𝑔𝑚𝑒𝑛𝑡𝑖𝑛𝑔 𝑎𝑡 𝑢𝑡𝑖𝑙𝑖𝑠𝑎𝑡𝑖𝑜𝑛, 𝑢 𝑢𝑛𝑐𝑜𝑛𝑑𝑖𝑡𝑖𝑜𝑛𝑎𝑙 𝑝𝑟𝑜𝑏𝑎𝑏𝑖𝑙𝑖𝑡𝑦 𝑓𝑜𝑟 𝑎𝑢𝑔𝑚𝑒𝑛𝑡𝑖𝑛𝑔 𝑤ℎ𝑒𝑛 𝑢𝑡𝑖𝑙𝑖𝑠𝑒𝑑 𝑎𝑏𝑜𝑣𝑒 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