State o f the Infrastructure Report 2016/17 - Western Power
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State of the Infrastructure Report 2016/17
An appropriate citation for this paper is:
State of the Infrastructure Report 2016/17
Western Power
363 Wellington Street
Perth WA 6000
GPO Box L921 Perth WA 6842
T: 13 10 87 | Fax: 08 9225 2660
TTY 1800 13 13 51 | TIS 13 14 50
Electricity Networks Corporation
ABN 18 540 492 861
enquiry@westernpower.com.au
westernpower.com.au
Enquiries about this report should be directed to:
www.westernpower.com.au
Telephone: 13 10 87
Email: enquiry@westernpower.com.au
Page ii
I N TR OD C TI O N
Contents
Introduction .................................................................................................................................................5
1. Executive summary ..............................................................................................................................6
1.1 Public safety perfor ance..........................................................................................................6
1.2 Environ ental perfor ance ......................................................................................................7
1.3 Reliability of supply perfor ance ...............................................................................................8
1.4 Power quality perfor ance......................................................................................................10
1.5 Asset state ...............................................................................................................................11
1.6 Network capacity .....................................................................................................................12
1.7 Year-on-year co parisons........................................................................................................12
2. Public sa ety per ormance .................................................................................................................13
2.1 Public I pact Perfor ance ......................................................................................................14
3. Environmental per ormance ..............................................................................................................15
4. Reliability, security o supply, and power quality per ormance .........................................................16
4.1 Reliability perfor ance ............................................................................................................16
4.2 AA3 Trans ission Service Standard Bench arks ......................................................................20
4.3 Power quality perfor ance......................................................................................................22
5. State o Network assets .....................................................................................................................23
5.1 Introduction.............................................................................................................................23
5.2 Structures ................................................................................................................................25
5.3 Conductors ..............................................................................................................................34
5.4 Distribution plant and equip ent ............................................................................................42
5.5 Trans ission plant and equip ent ..........................................................................................52
5.6 Secondary Syste s ..................................................................................................................64
6. Capacity .............................................................................................................................................66
6.1 Constrained zone and ter inal substations..............................................................................66
6.2 Trans ission network constraints ............................................................................................67
6.3 Constraints i pacting block loads ............................................................................................70
6.4 Constraints i pacting generation.............................................................................................72
6.5 Constrained distribution feeders ..............................................................................................73
6.6 Constrained distribution transfor ers .....................................................................................75
Page iii
I N TR OD C TI O N
A.1 Sa ety reporting de initions .................................................................................................................77
A.2 Network asset risk rating approach .....................................................................................................79
A.3 List o abbreviations.............................................................................................................................81
Page iv
I N TR OD C TI O N
Introduction
Purpos
The pri ary purpose of Western Power's State of the Infrastructure Report ("the Report") is to provide
stakeholders with infor ation about the perfor ance and state of the Western Power Network1 ("the Network").
This supports i prove ents in the quality, transparency and align ent of decision- aking by all stakeholders.
Western Power first published annual perfor ance and asset data in this for at for the year 2011/12, in
response to one of the reco endations of the Parlia entary Standing Co ittee on Public Ad inistration
(Report 14 - Unassisted Failure) in January 2012. The Report is updated and published annually, during Access
Arrange ent 3 (AA3) period, aintaining a consistent and independently-verifiable approach to the anner in
which perfor ance data is sourced, analysed and reported.
Scop
The Report covers key trans ission and distribution Network assets for the period 1 July 2016 to 30 June 2017
("the reporting period") and provides:
• an overview of the perfor ance of the Network with respect to public safety, the environ ent, supply
reliability and power quality over the reporting period
• a forecast of the capacity of the Network to supply future de and
• a snapshot of the age profile, condition and risk of key Network assets as at 30 June 2017, with a
co parison of the sa e data fro previous years, where available.2
The Report does not present infor ation on strategies, treat ent plans or network invest ent progra s; these
are detailed in a range of other docu ents prepared by Western Power.
Cont xt
Western Power's objective is to provide its custo ers with safe, reliable and efficient access to its electricity
network. It focuses on providing agreed levels of service at the lowest practical cost, while ini ising har to the
public, our workforce and the environ ent, and da age to property.
Western Power anage its electricity network in line with an asset anage ent syste . The syste eets the
require ents of Australian Standard for Electricity Network Safety Manage ent Syste (AS5577). The asset
anage ent syste is aligned with the require ents of Econo ic Regulation Authority of Western Australia
(ERA), and is recognised for its aturity as a “leading practice” as assessed by independent auditors. The ix of
asset anage ent capability, technological capability, and a culture of innovation and continual i prove ent
positions Western Power to deliver on its business objectives.
An integral part of providing electricity network service is the invest ent on asset treat ent progra (inspection,
repair, aintenance and replace ent) centred around identifying and itigating safety risks on the network asset
including poles, towers, conductors and substations. This risk based approach co plies with AS5577 and includes
consideration of the asset condition and the potential of the asset to cause a safety or reliability consequence if
failure occurs. Under this approach, it is i portant to note that the nu ber of failures of a particular asset ay
vary significantly without a change in the underlying risk and this is an i portant consideration when interpreting
this report.
1
Western Power Network is a part of the network co ponent of the South West Interconnected Syste (SWIS) – The SWIS is the entire
interconnected syste , including all the generators and s all pockets of privately owned networks. (Reference Electricity Access code 2004
clause 1.3, page 31.)
2
Historical values are reproduced fro previous Reports.
5 S TATE O F TH E I N FR AS TR U C TURE REP OR T 20 16 / 17
EX EC T I V E S M M AR Y
1. Executive summary
The State of the Infrastructure Report focuses on five key areas:
1. public safety perfor ance
2. environ ental perfor ance
3. reliability of supply and power quality perfor ance
4. asset state (age and condition)
5. capacity of the Network to supply future de and.
Perfor ance in 2016/17 in each of these areas (including overall asset state) was aterially consistent with that
reported for the previous year, in the context of nor al year-on-year variability arising fro external factors.
Western Power's public safety, environ ental and reliability perfor ance is influenced by factors such as:
• the condition of the Network
• the operating conditions and practices of the Network
• interaction with the Network by e bers of the public
• interaction with the Network by flora and fauna
• work practices and the actions undertaken by its workforce
• external environ ental conditions.
This Report presents infor ation only on those assets assessed as presenting the highest levels of risk to:
• people and property due to injury or da age
• the environ ent
• custo er reliability and quality of supply.
1.1 Public sa ety per ormance
Western Power reports on public safety perfor ance using a range of easures agreed with its safety regulator
EnergySafety, including the frequency of public safety incidents.
6 S TATE O F TH E I N FR AS TR U C TURE REP OR T 20 16 / 17
EX EC T I V E S M M AR Y
As su arised in Table 1, 577 public safety incidents were recorded during the reporting period, with no
fatalities.
The increase in the nu ber of public safety incidents recorded (with specific focus on third party contacts) is
attributed to ongoing i prove ents to the way that data is captured by the organisation. This has resulted in
i proved visibility and increased the nu ber of incidents being recorded. Historical figures have not been
recalculated.
Table 1: Public sa ety incidents by type
Public sa ety incident type 2012/13 2013/14 2014/15 2015/16 2016/17
Fire / da age caused by Western Power assets or inadvertent external contact with 79 118 149 108 144
the electricity network
Vehicle, plant or equip ent contact by public with the electricity network not resulting 47 75 76 257 428
in fire, da age or injury
Injury (requiring edical treat ent) or death to a person or ani al fro inadvertent 12 6 4 2 3
contact with the electricity network
Injury (requiring edical treat ent) or death to a person fro electric shock where 3 0 0 2 2
the shock was caused by the electricity network
EnergySafety order or reported defect 6 2 0 0 0
Total 147 201 229 369 577
1.2 Environmental per ormance
Western Power reports on environ ental perfor ance using a range of easures. These include the frequency of
hydrocarbon leaks fro Western Power's network assets and vehicle fleet, as su arised in Table 2. During the
reporting period, 713 such incidents were recorded.
Western Power is also required to report significant environ ental incidents to its regulators. During the 2016/17
financial year Western Power reported two environ ental incidents. The first was an oil spill fro a transfor er
after pole failure, which was successfully re ediated. The second was unauthorised clearing and drilling ud
discharges during the installation of an underground cable. Re ediation and rehabilitation of the area will be
undertaken in liaison with environ ental regulators.
Table 2: Environmental hydrocarbon leak incidents by cause
2012/133 2013/14 2014/15 2015/16 2016/17
Network asset failure N/A 459 798 847 674
Vehicle fleet N/A 86 71 25 20
Hu an factors N/A 27 20 14 6
Other (includes weather, fauna and third-party i pacts) N/A 46 33 22 13
Total N/A 618 922 908 713
3
Environ ental perfor ance reporting was introduced in the 2013/14 State of the Infrastructure Report and is not available for
2012/13.
7 S TATE O F TH E I N FR AS TR U C TURE REP OR T 20 16 / 17
EX EC T I V E S M M AR Y
1.3 Reliability o supply per ormance
Western Power easures reliability of supply perfor ance through:
1. corporate indicators of overall network perfor ance
2. Service Standard Bench arks defined by the AA3 regulatory contract in accordance with section 11.2 of
the lectricity Networks Access Code 2004
3. prescribed perfor ance levels in accordance with the lectricity Industry Act 2004 - lectricity Industry
(Network Quality and Reliability of Supply) Code 2005 ("NQRS Code").
1.3.1 Corporate indicators o overall network per ormance
Two easures easure the frequency and duration of power supply interruptions:
1. Number o interruptions (frequency) - the total nu ber of custo er interruptions lasting ore than
one inute on the Western Power Network after exclusions, divided by the total nu ber of connected
custo ers (averaged over the reporting period).
2. Supply unavailability (duration) - the annual su of the duration of each custo er interruption lasting
ore than one inute (custo er inutes interrupted) on the Western Power Network after exclusions,
divided by the total nu ber of connected custo ers (averaged over the reporting period).
These are reported at the level of the entire Western Power Network and exclude interruptions that are:
• less than one inute in duration
• caused by generation outages and other third-party influences.
Table 3 su arises the nu ber of interruptions and inutes of supply unavailability recorded in this and the
preceding reporting periods.
Table 3: Power supply interruptions - requency and duration
2012/13 2013/14 2014/15 2015/16 2016/17
Nu ber of interruptions 2.5 2.5 2.4 2.11 2.14
Minutes of supply unavailability 345 386 340 351 338
The largest i pact to supply unavailability was an interruption due to a bird strike in Albany substation resulting
in al ost 23,000 custo ers to be without power for around two and a half hours.
1.3.2 AA3 Service Standard Benchmarks
Under the AA3 regulatory contract, Western Power is required to:
1. aintain service levels consistent with historical averages of the three years up to 30 June 2012 for
distribution reliability easures and five years up to 30 June 2012 for all other service standard
easures
2. i prove service levels only where this is of value to the custo er and can be done efficiently.
8 S TATE O F TH E I N FR AS TR U C TURE REP OR T 20 16 / 17
EX EC T I V E S M M AR Y
AA3 defines 14 Service Standard Bench arks relating to the levels of service for distribution and trans ission
reliability of supply and security of supply. Of these, eight easure the frequency and duration of interruptions
and ini u levels of service on the distribution network, in a anner consistent with national and international
industry practice. These are based on the following etrics, categorised by area (CBD, urban, rural short, and
rural long):
1. System Average Interruption Frequency Index (SAIFI) - the average nu ber of interruptions to a
custo er's supply in a year
2. System Average Interruption Duration Index (SAIDI) - the average total duration (in inutes) of
interruptions to a custo er's supply in a year.
The bench arks exclude interruptions lasting less than one inute and those caused by generation and other
third-party influences, planned interruptions, ajor event days and force majeure events.
As su arised in Table 4, all eight distribution network Service Standard Bench arks were achieved during the
reporting period.
Table 4: Reliability per ormance - distribution network Service Standard Benchmarks
2012/13 2013/14 2014/15 2015/16 2016/17
Distribution Service Standard Benchmarks achieved 7o 8 7o 8 8o 8 8o 8 8o 8
The reliability and security of supply perfor ance of Western Power's trans ission network is easured against
the following service standard bench arks as per the AA3 regulatory contract:
• Circuit Availability - the actual circuit hours available for trans ission circuits, easured as a
percentage of total possible circuit hours. This is a security of supply perfor ance easure.
• System Minutes Interrupted - the su ation of egawatt inutes of unserved energy at the
substation resulting fro outages on trans ission circuits, which is connected to the trans ission
network, divided by the syste peak in egawatts. This is easured for:
– the eshed trans ission network
– the radial trans ission network
• Loss o Supply Events - the annual nu ber of loss of supply events whose duration is:
– greater than 0.1 syste inute and less than or equal to 1.0 syste inute
– greater than 1.0 syste inute
• Average Outage Duration - the annual average nu ber of inutes of all unplanned trans ission plant
outages.
As su arised in Table 5, all six trans ission Service Standard Bench arks were achieved during the reporting
period.
Table 5: Reliability per ormance - transmission network Service Standard Benchmarks
2012/13 2013/14 2014/15 2015/16 2016/17
Transmission Service Standard Benchmarks achieved 6o 6 6o 6 6o 6 5o 6 6o 6
9 S TATE O F TH E I N FR AS TR U C TURE REP OR T 20 16 / 17
EX EC T I V E S M M AR Y
1.3.3 NQRS Code per ormance metrics
The NQRS Code perfor ance etrics easure the frequency and duration of all interruptions exceeding one
inute in duration experienced by custo ers, regardless of cause, categorised by geographic area ("Perth CBD",
"urban areas excluding Perth CBD" and "other areas of the state").
In accordance with the NQRS Code, Western Power reports the nu ber of s all-use custo ers experiencing
interruptions exceeding 12 hours continuous duration, as shown in Table 6.
Table 6: Small-use customers experiencing outages exceeding 12 hours continuous duration
Measure 2012/13 2013/14 2014/15 2015/16 2016/17
Small-use customers experiencing at least one outage exceeding 12 hours 38,820 43,750 37,280 39,495 43,794
continuous duration
The custo er interruptions exceeding 12 hours for the 2016/17 period were predo inantly during significant
weather events resulting in pole top fires in January 2017 and a ajor stor in October 2016.
Western Power also easures the nu ber of s all-use custo ers experiencing interruptions in excess of the
axi u frequency per itted under the NQRS Code (9 interruptions in urban and CBD areas; 16 in all other
areas), as su arised in Table 7.
Table 7: Small-use customers experiencing interruptions in excess o maximum requency permitted
Measure 2012/13 2013/14 2014/15 2015/16 2016/17
Urban areas (including CBD) - s all-use custo ers interrupted ore than 9 ti es 8,702 12,326 4,755 3,529 7,166
Other areas (including rural) - s all-use custo ers interrupted ore than 16 2,341 5,154 3,912 3,204 3,344
ti es
Total 11,043 17,480 8,667 6,733 10,510
Custo ers in Urban areas who experienced ore than nine interruptions for the 2016/17 period were
predo inantly within the Bunbury and Perth etropolitan regions. The increased nu ber of custo ers i pacted
was ainly the result of a larger a ount of planned work focussing on replace ent of overhead conductors.
Custo ers in Other areas who experienced ore than 16 interruptions during the 2016/17 period were
predo inantly located in the rural South West region.
1.4 Power quality per ormance
To ensure the correct and safe operation of network and custo er equip ent, Western Power onitors power
quality para eters4 on the low voltage (LV) distribution network5.
Table 8 su arises a key power quality perfor ance para eter.
Table 8: Power quality per ormance6
2012/13 2013/14 2014/15 2015/16 2016/17
Proportion of networks operating below 6 kV exceeding allowable range 11.7% 13.5% 13.1% 12.4% 8.6%
4
The range of para eters onitored is in accordance with the require ents of the NQRS Code and the Technical Rules.
5
The Annual Reliability and Power Quality Report 2016/17 presents further infor ation on power quality perfor ance during the reporting
period.
6
Previous versions of the State of the Infrastructure Report have included the easure titled “proportion of the year in which custo er
voltage was potentially non-co pliant”. This easure is no longer reported because the proportion of the year will vary fro site to site.
10 S TATE O F TH E I N FR AS TR U C TURE REP OR T 20 16 / 17EX EC T I V E S M M AR Y
1.5 Asset state
The Network includes both overhead and underground construction and co prises illions of diverse individual
assets, such as poles, towers, overhead wires, underground cables, switchgear, transfor ers, protection
equip ent and security fencing. These are of various ages and at different stages of their lifecycles, and subject to
a broad range of environ ental and operating conditions. A sound understanding of the state (or health) of an
asset provides insight into its likelihood of failure in the future, per itting an assess ent of the risk it poses. This,
in turn, infor s strategies and plans for aintenance and renewal activities.
Western Power classifies and reports the state of Network assets using a range of para eters, including age,
condition, expected service life and risk7.
While the state of assets varies significantly with type and location, the overall position at the Network level is
aterially unchanged fro that reported in the 2015/16 State of the Infrastructure Report. Table 9 provides the
su ary view for 2016/17.
Table 9: Summary o asset class risk ratings
Number o asset classes with rating
Risk area Risk rating
2016/17
Sa ety Extre e 0
High 8
Mediu 10
Low 3
Service Extre e 0
High 0
Mediu 12
Low 5
Environmental Extre e 0
High 2
Mediu 0
Low 0
A significant co ponent of the Report is dedicated to providing an overview of the assessed state of the key
classes of Network assets, as well as the associated high-level risk assess ent.
7
See Appendix A.2 for network asset risk rating approach
11 S TATE O F TH E I N FR AS TR U C TURE REP OR T 20 16 / 17EX EC T I V E S M M AR Y
1.6 Network capacity
The Network generally has sufficient capacity to eet short-ter forecast load growth. A nu ber of Network
ele ents are currently experiencing capacity li itations or are projected to do so in 2017/18. Those capacity
shortfalls that do not co ply with planning standards will be addressed by projects planned during AA4 and the
next regulatory period.
Existing and e erging capacity constraints increase the likelihood of long duration custo er supply interruptions
following contingency events, such as the unplanned outage of a substation transfor er or trans ission line
circuit, particularly when they coincide with adverse loading conditions, such as su er peak load days. These
constraints do not represent an i ediate inability to supply custo ers, due to the low probability of these
circu stances occurring concurrently.
Table 10: Network elements orecast to exceed capacity targets (percent)
Network element 2014/15 2015/16 2016/17 2017/18
Zone substations 5.4 3.9 3.9 3.1
Ter inal substations 0.0 0.0 0.0 0.0
Metropolitan feeders 26.0 16.0 11.0 21.1
Rural feeders 2.4 2.0 2.0 2.6
Trans ission lines 2.3 2.0 2.0 3.7
Distribution transfor ers 8 0.1 0.1 0.1 0.1
1.7 Year-on-year comparisons
Explanatory co entary is only provided where there is significant variance between the current year and
previous years.
In co paring year-on-year perfor ance, it is i portant to note that there can be significant variability for a
nu ber of reasons, including:
• the general state of assets, which influences failure rates and the frequency with which defects are
found
• the geographic diversity of the Network, which influences whether a failure results in an incident
• year-on-year variability in environ ental factors (e.g. the frequency and intensity of stor s and
lightning events, fuel loads and su er weather conditions) and public interference with the Network
• Previous year’s perfor ance data in the Report reflects the data collection, investigation and
classification ethods available at the ti e unless specifically noted.
8
Analysis perfor ed based on nu ber of transfor ers with a capacity of 100kVA or greater.
12 S TATE O F TH E I N FR AS TR U C TURE REP OR T 20 16 / 17P B L I C S AF E TY PERF OR M AN CE
2. Public sa ety per ormance
Western Power reports on public safety perfor ance using a range of easures agreed with its safety regulator
EnergySafety, including the frequency of public safety incidents.9
As su arised in Table 11, 577 public safety incidents were recorded during the reporting period, with no
fatalities. This equates to a rolling 12- onth average of 48.1 incidents per onth. There was no target for public
safety incidents as it was replaced by the public i pact perfor ance target in July 2015.
The increase in the nu ber of public safety incidents recorded (with specific focus on third party contacts) is
attributed to ongoing i prove ents to the way that data is captured by the organisation. This has resulted in
i proved visibility and increased the nu ber of incidents being recorded. Historical figures have not been
recalculated.
Table 11: Public sa ety incidents by type
Public sa ety incident type 2012/13 2013/14 2014/15 2015/16 2016/17
Fire / da age caused by Western Power assets or inadvertent external contact with 79 118 149 108 144
the electricity network
Vehicle, plant or equip ent contact by public with the electricity network not resulting 47 75 76 257 428
in fire, da age or injury
Injury (requiring edical treat ent) or death to a person or ani al fro inadvertent 12 6 4 2 3
contact with the electricity network
Injury (requiring edical treat ent) or death to a person fro electric shock where 3 0 0 2 2
the shock was caused by the electricity network
EnergySafety order or reported defect 6 2 0 0 0
Total 147 201 229 369 577
Table 12 su arises public safety perfor ance against other key indicators.
Table 12: Sa ety per ormance indicators
Sa ety per ormance indicator 2012/13 2013/14 2014/15 2015/16 2016/17
Notifiable incidents 61 43 28 58 60
Electric shocks that do not require edical treat ent, relating to Western Power 238 227 239 229 157
assets or activity
Unassisted wood pole failures (Distribution)10 378 220 308 305 327
Unassisted wood pole failures (Trans ission) 23 12 4 10 6
Unassisted ains conductor failures (Distribution)11 383 643 264 302 298
Unassisted conductor failures (Trans ission) 0 2 0 3 0
Ground fire incidents 80 118 145 114 128
Western Power reviews all reported electric shock and ground fire events and reviews its asset strategies
appropriately to reduce public safety risk.
9
See Appendix A.1 for safety reporting definitions.
10
Section 5.2.1
11
Sections 5.3.1
13 S TATE O F TH E I N FR AS TR U C TURE REP OR T 20 16 / 17P B L I C S AF E TY PERF OR M AN CE
2.1 Public Impact Per ormance
The 12- onth rolling average for Public I pact Incidents for the 2016/17 reporting period, was 0.3 against a
corporate target of 0.4 and is su arised in Table 13.
Table 13: Public Impact per ormance indicators - number o incidents
Public Impact 2015/16 2016/17
Public Injury 0 3
Property Da age 3 1
Note:
• The Public I pact indicator provides a reflection of the i pact of the Western Power Network on
e bers of the public, by reporting the public injury (requiring edical treat ent) and public property
da age incidents (greater than $20,000 da age) arising fro :
• Western Power Network assets (including al-operation)
• actions by Western Power's workforce
• third-party actions in which substandard Western Power Network assets were a contributing factor.
14 S TATE O F TH E I N FR AS TR U C TURE REP OR T 20 16 / 17E NV I RO NM E NT AL P ER FO RM A NC E
3. Environmental per ormance
Western Power reports on environ ental perfor ance using a range of easures. These include the frequency of
hydrocarbon leaks fro Western Power's network assets and vehicle fleet, as su arised in Table 2. During the
reporting period, 713 such incidents were recorded.
Western Power is also required to report significant environ ental incidents to its regulators. During the 2016/17
financial year Western Power reported two environ ental incidents. The first was an oil spill fro a transfor er
after pole failure, which was successfully re ediated. The second was unauthorised clearing and drilling ud
discharges during the installation of an underground cable. Re ediation and rehabilitation of the area will be
undertaken in liaison with environ ental regulators.
Table 14: Environmental hydrocarbon leak incidents by cause
2012/1312 2013/14 2014/15 2015/16 2016/17
Network asset failure N/A 459 798 847 674
Vehicle fleet N/A 86 71 25 20
Hu an factors N/A 27 20 14 6
Other (includes weather, fauna and third-party i pacts) N/A 46 33 22 13
Total N/A 618 922 908 713
To ini ise the risk of soil and ground water pollution fro incidents, Western Power installs sealed bunds under
trans ission transfor ers. Table 15 su arises the status of trans ission transfor er bunds, which are
progressively upgraded to the current standard to continually reduce the risk of a ajor incident.
Table 15: Status o transmission trans ormer bunds
2012/13 2013/14 2014/15 2015/16 2016/17
Bund draining to a holding tank, poly er filter or interceptor N/A 202 216 220 227
Contain ent bund draining to soil N/A 141 136 135 128
No bund N/A 11 14 13 13
Total N/A 354 366 368 368
12
Environ ental perfor ance reporting was introduced in the 2013/14 State of the Infrastructure Report and is not available for
2012/13.
15 S TATE O F TH E I N FR AS TR U C TURE REP OR T 20 16 / 17R EL I A BI L I T Y, SEC RI TY OF S P PL Y, AN D P OW E R Q AL I TY P ER FORM A NCE
4. Reliability, security o supply, and power quality per ormance
4.1 Reliability per ormance
Reliability of supply is funda entally i portant to our custo ers and is reflected as a key objective for Western
Power.
Reliability is easured by custo ers' felt experience of the Western Power Network with regards to the nu ber
of sustained interruptions custo ers have experienced.13 The nu ber of interruptions and supply unavailability
are both easured over a rolling 12- onth period.
Western Power easures reliability of supply perfor ance through:
1. corporate indicators of overall network perfor ance
2. Service Standard Bench arks defined by the AA314 regulatory contract in accordance with section 11.2
of the lectricity Networks Access Code 2004
3. prescribed perfor ance levels in accordance with the lectricity Industry Act 2004 - lectricity Industry
(Network Quality and Reliability of Supply) Code 2005 ("NQRS Code").
4.1.1 Corporate indicators o overall network per ormance
There are two easures of power supply interruptions:15
1. Number o interruptions (frequency) - the total nu ber of custo er interruptions lasting ore than
one inute on the Western Power Network after exclusions, divided by the total nu ber of connected
custo ers (averaged over the reporting period).
2. Supply unavailability (duration) - the annual su of the duration of each custo er interruption lasting
ore than one inute (custo er inutes interrupted) on the Western Power Network after exclusions,
divided by the total nu ber of connected custo ers (averaged over the reporting period).
These are reported at the level of the entire Western Power Network and exclude interruptions that are:
• less than one inute in duration and/or;
• caused by generation outages and other third-party influences.
Table 16 su arises the nu ber of interruptions and inutes of supply unavailability recorded in this and the
preceding three reporting periods.
Table 16: Power supply interruptions - requency and duration
2012/13 2013/14 2014/15 2015/16 2016/17
Nu ber of interruptions 2.5 2.5 2.4 2.11 2.14
Minutes of supply unavailability 345 386 340 351 338
The largest i pact to supply unavailability was an interruption due to a bird strike in Albany substation resulting
in al ost 23,000 custo ers to be without power for around 2 and a half hours.
13
Further infor ation on reliability perfor ance is published in the Annual Reliability and Power Quality Report 2016/17.
14
Western Power's current Access Arrange ent (AA3) for 1 July 2012 to 30 June 2017.
15
These easures were introduced during the reporting period ending 30 June 2013.
16 S TATE O F TH E I N FR AS TR U C TURE REP OR T 20 16 / 17R EL I A BI L I T Y, SEC RI TY OF S P PL Y, AN D P OW E R Q AL I TY P ER FORM A NCE
4.1.2 AA3 Distribution Service Standard Benchmarks
Under the AA3 regulatory contract, Western Power is required to:
1. aintain service levels consistent with historical averages of the three years up to 30 June 2012 for
distribution reliability easures and five years up to 30 June 2012 for all other service standard
easures
2. i prove service levels only where this is of value to the custo er and can be done efficiently.
AA3 defines 14 Service Standard Bench arks16 relating to the levels of service for distribution and trans ission
reliability of supply and security of supply. Of these, eight easure the frequency and duration of interruptions
and ini u levels of service on the distribution network, in a anner consistent with national and international
industry practice. These are based on the following etrics, categorised by area (CBD, urban, rural short, and
rural long):
1. System Average Interruption Frequency Index (SAIFI) - the average nu ber of interruptions to a
custo er's supply in a year
2. System Average Interruption Duration Index (SAIDI) - the average total duration (in inutes) of
interruptions to a custo er's supply in a year.
The bench arks exclude interruptions lasting less than one inute and those caused by generation and other
third-party influences, planned interruptions, ajor event days and force majeure events.
As su arised in Table 17, all eight distribution network Service Standard Bench arks were achieved during the
reporting period.
Table 17: Reliability per ormance - distribution network Service Standard Benchmarks
2012/13 2013/14 2014/15 2015/16 2016/17
Distribution Service Standard Bench arks achieved 7 of 8 7 of 8 8 of 8 8 of 8 8 of 8
Figure 1 and Figure 2 provide a co parison of distribution reliability perfor ance of the Western Power Network
perfor ance over ti e.17 For the distribution network, the duration of outages increased arginally in 2016/17
as did the frequency of interruptions.
16
A further three Distribution Service Standard Bench arks report street lighting repair ti es (for etropolitan and regional areas) and call
centre perfor ance.
17
As per the Service Standard Perfor ance Report for the year ending June 2017
17 S TATE O F TH E I N FR AS TR U C TURE REP OR T 20 16 / 17R EL I A BI L I T Y, SEC RI TY OF S P PL Y, AN D P OW E R Q AL I TY P ER FORM A NCE
Figure 1: Reliability per ormance (SAIDI)
180
175
175 172
169
170
Minutes per year
164
165
160
155 152
150
145
140
2012/13 2013/14 2014/15 2015/16 2016/17
Figure 2: Reliability per ormance (SAIFI)
2.00
1.75
1.80 1.62 1.56
Interruptions per year
1.60 1.43
1.37
1.40
1.20
1.00
0.80
0.60
0.40
0.20
0.00
2012/13 2013/14 2014/15 2015/16 2016/17
Figure 3 and Figure 4 show actual perfor ance of the CBD, Urban, Rural Short and Rural Long feeder categories
against the Service Standard Bench arks.
18 S TATE O F TH E I N FR AS TR U C TURE REP OR T 20 16 / 17R EL I A BI L I T Y, SEC RI TY OF S P PL Y, AN D P OW E R Q AL I TY P ER FORM A NCE
Figure 3: Reliability per ormance by eeder category (SAIDI)
800
700
600
500
Minutes
400
300
200
100
0
CBD Urban Rural Short Rural Long
Actual 2016/17 Perfor ance 2016/17 Service Standard Bench arks
Figure 4: Reliability per ormance by eeder category (SAIFI)
5.0
4.0
Nu ber of interruptions
3.0
2.0
1.0
0.0
CBD Urban Rural Short Rural Long
Actual 2016/17 Perfor ance 2016/17 Service Standard Bench arks
4.1.3 NQRS Code per ormance metrics
The NQRS Code perfor ance etrics easure the frequency and duration of all interruptions exceeding one
inute in duration experienced by custo ers, regardless of cause, categorised by geographic area (“Perth CBD”,
“urban areas excluding Perth CBD”, and “other areas of the state”).
In accordance with the NQRS Code, Western Power reports the nu ber of s all-use18 custo ers experiencing
interruptions exceeding 12 hours continuous duration, as shown in Table 18.
Table 18: Small-use customers experiencing outages exceeding 12 hours continuous duration
Measure 2012/13 2013/14 2014/15 2015/16 2016/1719
S all-use custo ers experiencing at least one outage exceeding 12 hours 38,820 43,750 37,280 39,495 43,794
continuous duration
18
The NQRS Code defines s all-use custo ers as those whose annual electricity consu ption does not exceed 160 MWh.
19
Annual Reliability and Power Quality Report 2016/17
19 S TATE O F TH E I N FR AS TR U C TURE REP OR T 20 16 / 17R EL I A BI L I T Y, SEC RI TY OF S P PL Y, AN D P OW E R Q ALI TY P ERF ORM A NCE
The custo er interruptions exceeding 12 hours for the 2016/17 period predo inantly during significant weather
events resulting in pole top fires in January 2017 and a ajor stor in October 2016.
Western Power also easures the nu ber of s all-use custo ers experiencing interruptions in excess of the
axi u frequency per itted under the NQRS Code (9 interruptions in urban and CBD areas; 16 in all other
areas), as su arised in Table 19.
Table 19: Small-use customers experiencing interruptions in excess o maximum requency permitted
Measure 2012/13 2013/14 2014/15 2015/16 2016/1720
Urban areas (including CBD) - s all-use custo ers interrupted ore than 9 ti es 8,702 12,326 4,755 3,529 7,166
Other areas (including rural) - s all-use custo ers interrupted ore than 16 2,341 5,154 3,912 3,204 3,344
ti es
Total 11,043 17,480 8,667 6,733 10,510
Custo ers in Urban areas who experienced ore than nine interruptions for the 2016/17 period were
predo inantly within the Bunbury and Perth etropolitan regions. The increased nu ber of custo ers i pacted
was ainly the result of a larger a ount of planned work focussing on replace ent of overhead conductors.
Custo ers in Other areas who experienced ore than 16 interruptions during the 2016/17 period were
predo inantly located in the rural South West region.
4.2 AA3 Transmission Service Standard Benchmarks
The reliability and security of supply perfor ance of Western Power's trans ission network is easured against
the following service standard bench arks as per the AA3 regulatory contract referred to in section 4.1.2:
• Circuit Availability - the actual circuit hours available for trans ission circuits, easured as a
percentage of total possible circuit hours. This is a security of supply perfor ance easure.
• System Minutes Interrupted - the su ation of egawatt inutes of unserved energy at the
substation resulting fro outages on trans ission circuits, which is connected to the trans ission
network, divided by the syste peak in egawatts. This is easured for:
– the eshed trans ission network
– the radial trans ission network
• Loss o Supply Events - the annual nu ber of loss of supply events whose duration is:
– greater than 0.1 syste inute and less than or equal to 1.0 syste inute
– greater than 1.0 syste inute
• Average Outage Duration - the annual average nu ber of inutes of all unplanned trans ission plant
outages.
20
Annual Reliability and Power Quality Report 2016/17
20 S TATE O F TH E I N FR AS TR U C TURE REP OR T 20 16 / 17R EL I A BI L I T Y, SEC RI TY OF S P PL Y, AN D P OW E R Q AL I TY P ER FORM A NCE
As su arised in Table 20, all six trans ission Service Standard Bench arks were achieved during the reporting
period.
Table 20: Reliability per ormance - transmission network Service Standard Benchmarks21
Benchmark 2012/13 2013/14 2014/15 2015/16 2016/17
Circuit Availability ≥ 97.7% 98.4% 98.0% 98.5% 98.7% 98.9%
Syste Minutes Interrupted
Meshed network ≤ 12.50 4.50 4.82 6.6 6.8 8.2
Radial network ≤ 5.0 1.2 3.7 1.6 0.5 0.7
Loss of Supply Events
> 0.1 and ≤ 1 system minute ≤ 33 11 17 24 15 16
> 1 system minute ≤4 1 1 0 1 2
Average Outage Duration ≤ 886 866 795 720 1265 653
The following exclusions and assu ptions apply to these bench arks (as per the AA3 regulatory contract):
All Excludes interruptions caused by generation and other third-party influences, and force majeure events.
Circuit Availability Includes outages on trans ission circuits only. A trans ission circuit is a pri ary trans ission plant or equip ent that is
overhead lines, underground cables and bulk trans ission power transfor ers used to transport electricity.
Syste Minutes Assu es a axi u duration of 14 days for planned outages for ajor construction works (including periods in which
Interrupted availability is te porarily restored).
Excludes planned interruptions and o entary interruptions (less than one inute in duration).
Loss of Supply Events Excludes planned interruptions and o entary interruptions (less than one inute in duration).
Average Outage Excludes planned interruptions, o entary interruptions (less than one inute in duration), zone substation power
Duration transfor ers and reactive co pensation plant
Assu es a axi u duration of any contributing event is li ited to 14 days.
21
Perfor ance is reported as per the 2016/17 Service Standard Perfor ance Report sub itted to the ERA in accordance with the AA3
regulatory contract.
21 S TATE O F TH E I N FR AS TR U C TURE REP OR T 20 16 / 17R EL I A BI L I T Y, SEC RI TY OF S P PL Y, AN D P OW E R Q ALI TY P ERF ORM A NCE
4.3 Power quality per ormance
To ensure the correct and safe operation of network and custo er equip ent, Western Power onitors power
quality para eters22 on the low voltage (LV) distribution network. 23
The no inal network voltage of 240 V (single-phase) has an operating range of 28 V (equivalent to ±6%)24. Of the
19,764 networks operating below 6 kV, around 1,700 (8.6%) exceed the 28 V allowable range. These occur
predo inantly in older, overhead network areas installed pre-1990s that have s aller size conductors. The
s aller conductor size eans that when the load shifts fro low to full, the voltage change exceeds the allowable
28 V range.
Table 21 su arises a key power quality perfor ance para eter.
Table 21: Power quality per ormance25
2012/13 2013/14 2014/15 2015/16 2016/17
Proportion of networks operating below 6 kV exceeding allowable range 11.7% 13.5% 13.1% 12.4% 8.6%
22
The range of para eters onitored is in accordance with the require ents of the NQRS Code and the Technical Rules.
23
The Annual Reliability and Power Quality Report 2016/17 presents further infor ation on power quality perfor ance during the
reporting period.
24
Pre 1990 supply voltage level to custo ers in Western Australia was 254V +/-6%
25
Previous versions of the State of the Infrastructure Report have included the easure titled “proportion of the year in which custo er
voltage was potentially non-co pliant”. This easure is no longer reported because the proportion of the year will vary fro site to site.
22 S TATE O F TH E I N FR AS TR U C TURE REP OR T 20 16 / 17ST A TE OF N ET W ORK A SS ET S
5. State o Network assets
5.1 Introduction
The Network includes both overhead and underground construction and co prises illions of diverse individual
assets, such as poles, towers, overhead wires, underground cables, switchgear, transfor ers, protection
equip ent and security fencing. These are of various ages and at different stages of their lifecycle, and are
subjected to a broad range of operating conditions (including varying environ ental exposure).
A sound understanding of the state (or health) of an asset provides insight into its likelihood of failure of the
asset. This knowledge along with consideration of the potential consequences of failure, per its an assess ent
of the risk that asset poses. This, in turn, infor s strategies and plans for aintenance and renewal activities.
A su ary of Western Power’s aintenance and renewal strategies for its assets is available in its Network
Manage ent Plan.
Western Power classifies and reports the state of Network assets using a range of para eters, including age,
condition, expected service life and risk.
While the state of assets varies significantly with type and location, the overall position at the Network level is
aterially unchanged fro that reported in the 2015/16 State of the Infrastructure Report. Table 22 provides the
su ary view for 2016/17.
Table 22: Summary o asset class risk ratings
Number o asset classes with rating
Risk area Risk rating
2016/17
Sa ety Extre e 0
High 8
Mediu 10
Low 3
Service Extre e 0
High 0
Mediu 12
Low 5
Environmental Extre e 0
High 2
Mediu 0
Low 0
A significant co ponent of the Report is dedicated to providing an overview of the assessed state of the key
classes of Network assets, as well as their associated high-level risk assess ent.
23 S TATE O F TH E I N FR AS TR U C TURE REP OR T 20 16 / 17ST A TE OF N ET W ORK A SS ET S
5.1.1 Network elements
Western Power holds trans ission and distribution licences for the construction, anage ent and operation of
the two distinct Networks:
1. the distribution network, which transports electricity fro zone substations to individual custo ers
2. the transmission network, which transports electricity fro generators to trans ission ter inal
stations and then to zone substations.
These ele ents are ade up of any different types of assets. For the purposes of reporting the state of network
assets, these are grouped into five broad classes:
• structures (distribution & trans ission)
• conductors (distribution & trans ission)
• distribution plant and equip ent
• trans ission plant and equip ent
• secondary syste s.
5.1.2 Assessment o asset state
In the Report, assess ent of the state of an asset is based upon:
1. Condition - defects, attributes and characteristics i pacting the asset's serviceability.
2. Age - as an asset ages, the frequency and severity of defects tend to increase, progressively reducing its
serviceability until intervention (repair or replace ent) is required.
3. Design li e - this is the asset's originally designed functional lifespan independent of condition. It reflects
Western Power's engineering judge ent, e pirical evidence and data supplied by the anufacturer.
4. Expected service li e - this is the period over which the asset is expected to serve its intended functional
purpose safely, with an appropriate level of aintenance, repair or refurbish ent (that is not
disproportionate to the replace ent cost). It takes into consideration the actual perfor ance of the
asset and the cu ulative deterioration of the asset over ti e. The expected service life of an asset
typically exceeds its design life. Exceeding expected service life does not ean an asset is likely to fail
i ediately, however the frequency and severity of defects and the likelihood of in-service failure are
expected to increase.
5. Risk - risk assess ent is conducted using the enterprise risk assess ent criteria and considers both
consequence and likelihood of failure.
5.1.3 Data quality
The Network asset data used to support decisions has been collected over any decades. Although its quality and
co pleteness varies across assets classes due to historical variability in type and ethod of collection, it is
considered adequate for assessing risk and prioritising invest ent.
Western Power seeks to continually i prove the quality and co pleteness of this data through i prove ents in
technology and collection, storage and validation processes.
Previous year’s perfor ance data in the Report reflects the data collection, investigation and classification
ethods available at the ti e unless specifically noted.
24 S TATE O F TH E I N FR AS TR U C TURE REP OR T 20 16 / 17ST A TE OF N ET W ORK A SS ET S
5.1.4 Risk management
As electricity is inherently hazardous, addressing the risk associated with the Network is a core focus of Western
Power, particularly public safety risk.
Assessing the risks associated with Network assets is essential for their anage ent, as well as infor ing asset
anage ent strategies and prioritising invest ent.26 This assess ent considers both the likelihood and
consequence of asset failures, which are influenced by factors such as:
• asset condition
• how assets are operated
• the nu ber of custo ers they supply
• failure odes
• their proxi ity to the public
• exposure to stresses in service
• the characteristics of its surrounding environ ent / location.
In anaging public safety risk, the areas of particular focus are electric shock, initiation o ires and physical
impact.
Western Power's ability to address all Network risks in the short ter is constrained by a range of factors, such as
the volu e and geographic dispersion of assets, funding and its works delivery capacity. The risk-based
prioritisation of network invest ent is therefore critical to opti ising risk outco es within these constraints.
Western Power's approach to asset anage ent is aturing continuously to support risk-based prioritisation
that is ore robust, defensible and transparent. It aintains a continuous dialogue with key external
stakeholders to build understanding and confidence in the asset knowledge, tools and syste s used to develop
and support Western Power's invest ent decisions.
5.2 Structures
This asset class includes:
• poles
• towers
• dedicated streetlight etal poles27
• stays
• cross-ar s
• foundations
• earthing related to poles and towers.
Of these assets, poles, towers, dedicated streetlight etal poles and cross-ar s are identified as having the
greatest potential to adversely i pact public safety or reliability of the Network.
Note: Co unications structures are not discussed in this section. These structures do not carry live electrical
conductors.
26
See Appedix A.2 Network asset risk rating approach
27
This asset type was included within "other poles" in previous Reports, but is now reported separately due to its assessed risk level.
25 S TATE O F TH E I N FR AS TR U C TURE REP OR T 20 16 / 17ST A TE OF N ET W ORK A SS ET S
5.2.1 Poles and towers
Poles and towers support overhead lines and equip ent in the trans ission and distribution networks. Poles are
categorised and anaged according to their aterial type (wood, concrete or etal) and network type
(trans ission or distribution). Towers are only installed in the trans ission network.
Ass t conditions
A range of conditions affect the expected service life of poles and towers:
• conditions affecting all structures:
– fire da age
– da age fro cars and other objects
– cracks
• conditions affecting wood poles:
– splits
– rot
– insect da age (pri arily ter ites)
• conditions affecting etal or concrete structures:
– rust
– etal fatigue
– concrete cancer.
Poles and towers are regularly inspected to assess their condition. Based on AS/NZS 7000 (Table D4) untreated
unreinforced hardwood poles have a service life expectancy of 15-25 years and softwood poles have an expected
service life of 45-55 years.
It should be noted that the service life expectancy varies depending on installation conditions, aintenance over
pole life cycle and the other treat ents, such as reinforce ent, that ay be applied to the wood poles.
Exceeding service life expectancy does not ean that the pole will fail i ediately, however it can be expected
that the pole strength will reduce over ti e and should the pole be subject to its design loads it will fail.
In deter ining and prioritising the required asset treat ent, Western Power takes into consideration the life
expectancy of wood poles, past asset failure perfor ance and knowledge of asset condition.
Ass t ag profil
The age profile of the Network's 778,561 distribution poles is shown in Figure 5. Of these, 623,366 are wood
poles, of which 250,088 require treat ent (replace ent, reinforce ent, re-reinforce ent or re oval), in
accordance with Western Power's Wood Pole Strategy.
26 S TATE O F TH E I N FR AS TR U C TURE REP OR T 20 16 / 17ST A TE OF N ET W ORK A SS ET S
Figure 5: Age pro ile - distribution poles
250000
200000
150000
Quantity
100000
50000
0
41+
0-5
6-10
11-15
16-20
21-25
26-30
31-35
36-40
Age (years)
2014/15 Wood Pole Population 2014/15 Other Pole Population
2015/16 Wood Pole Population 2015/16 Other Pole Population
2016/17 Wood Pole Population 2016/17 Other Pole Population
In addition, 173 etal poles and 5 concrete poles have been assessed as having conditions requiring replace ent.
Figure 6 shows the volu es of distribution wood poles that do and do not require treat ent.
Figure 6: Serviceability pro ile by age - distribution wood poles
200000
180000
160000
140000
120000
Quantity
100000
80000
60000
40000
20000
0
41+
0-5
6-10
11-15
16-20
21-25
26-30
31-35
36-40
Age (years)
Serviceable Treat ent Required
Figure 7 shows the age profile of the total population of 39,981 trans ission structures at the end of the
reporting period. A total of 26,292 are wood poles (including auspoles), of which 7,295 require treat ent
(re oval, replace ent or reinforce ent).
27 S TATE O F TH E I N FR AS TR U C TURE REP OR T 20 16 / 17ST A TE OF N ET W ORK A SS ET S
Figure 7: Age pro ile - transmission structures
16000
14000
12000
10000
Quantity
8000
6000
4000
2000
0
41+
0-5
6-10
11-15
16-20
21-25
26-30
31-35
36-40
Age (years)
2014/15 Wood Pole Population 2014/15 Other Pole Population 2015/16 Wood Pole Population
2015/16 Other Pole Population 2016/17 Wood Pole Population 2016/17 Other Pole Population
Failur mod s and cons qu nc s
The failure of a wood pole generally results in the pole breaking or snapping. The consequences of highest i pact
are:
• i pact injury caused by a falling pole
• electric shocks resulting fro contact with fallen conductors
• fire caused by fallen conductors touching other aterial
• network outages.
Towers and etal poles can also fail, particularly if corroded.
Table 23 su arises unassisted wood pole failures recorded in this and the preceding reporting periods.
Table 23: Unassisted ailures - wood poles (quantity, percentage o total population)
2012/13 2013/14 2014/15 2015/16 2016/17
Qty % Qty % Qty % Qty % Qty %
Unassisted failures - distribution wood poles 378 0.06 220 0.03 308 0.05 305 0.05 327 0.05
Unassisted failures - trans ission wood 23 0.08 12 0.04 4 0.02 10 0.04 6 0.02
poles
28 S TATE O F TH E I N FR AS TR U C TURE REP OR T 20 16 / 17ST A TE OF N ET W ORK A SS ET S
Risk ass ssm nt
Table 24: Risk assessment - poles and towers
Risk area Rating Comment
Safety High 152,211 (24%) of distribution wood poles are situated in areas classified as Extre e or High bushfire risk zones; in these
areas, asset failure increases the risk of fire.
Distribution wood pole failures in densely populated areas increase the likelihood of injury and da age due to physical
i pact and electric shock resulting fro contact with fallen conductors.
Distribution wood poles are assessed as presenting a High public safety risk because of the relatively large population
requiring replace ent, reinforce ent, re-reinforce ent or re oval in accordance with Western Power's Wood Pole
Asset Manage ent Strategy.
Service Mediu The service i pact of the failure of a distribution pole is dependant of the position of the pole in the supply circuit and
can i pact any nu ber of custo ers.
Failure of trans ission structures is less co on and the level of redundancy in the trans ission syste serves to li it
the i pact of their failure on reliability.
5.2.2 Dedicated streetlight metal poles
Dedicated streetlight etal poles provide structural support for lu inaires and a conduit for conductors supplying
the lu inaire. They illu inate roads and public areas to enhance public safety and are generally present in areas
with underground LV distribution networks.
Ass t conditions
The key conditions affecting the expected service life of dedicated streetlight etal poles are:
• corrosion resulting fro exposure to varying ground and weather conditions
• structural da age caused by physical i pact (usually otor vehicle)
• deterioration of electrical co ponents.
These assets are designed in accordance with the structural strength and frangibility28 require ents of standards
AS/NZS 4676 and AS/NZS 1158. The ajority have a design such that the energy of a collision i pact is dispersed
to the upper half of the pole, ini ising injury risk to vehicle occupants. Such require ents li it the nu ber of
design easures that can be applied to ini ise the i pacts of corrosion.
Dedicated streetlight etal poles have an expected service life of 45 years.
Ass t profil
The age profile of the Network's 142,524 Dedicated Streetlight Metal Poles is shown in Figure 8 of those, 5,826
Dedicated Streetlight Metal Poles have been identified as requiring treat ent (re oval, replace ent or
reinforce ent), in accordance with Western Power's strategy for anaging assets of this type.
The network's population of these assets is increasing due to continued "gifting" of assets by Local Govern ent
Authority and developers and the replace ent of overhead conductor (and the wood poles supporting the )
under the State Underground Power Project.
28
This refers to an object's propensity to break into frag ents in the event of i pact, rather than defor ing elastically and retaining its
integrity as a single object.
29 S TATE O F TH E I N FR AS TR U C TURE REP OR T 20 16 / 17You can also read
