Appendix 1: Further Information on the Risks of Development near High-voltage Transmission Lines

Third-party underbuilding represents the single most significant risk to the existing line corridors. This issue underpins all other activities, because the more development and people are allowed within the corridors, the greater the frequency and consequence of accidents, faults and costs.

Examples

Multiple examples of underbuilding in urban areas in particular. Transpower can provide photos if required.

Frequency

There were estimated to be approximately 5000 encroachments of development (buildings, fences or structures) into NZECP34 areas in 2004. Most of these occurred in Auckland and other rapidly growing urban areas.

Transpower’s records show that between 2004 and 2006 there were approximately 633 new land parcels around the country (subdivisions) within a zone 25 metres either side of the line. Note: Any number of buildings may be established on these parcels, and this does not address existing land parcels and what could be built on those.

Risks to public include:

• increased risk of electrical hazards to the public from arcing, flashovers, earthing issues, and coming into direct contact with lines (eg, TV aerials or water overflow pipes inducing current under the lines)
• increased risk to the public from maintenance or acts of God (eg, a conductor may fall after a storm event, which could have significant effects if it occurred in a residential area)
• risks from loss of power supply (eg, event in October 2009 where third party activity caused power fault resulting in loss of supply to approximately 280,000

Risks to assets include:

• increased risk of contact with lines, resulting in an operational fault, or outage
• increased impediments to access to towers and poles, which can impede routine maintenance programmes, resulting in increased risks to structural integrity
• increased health and safety risks for line workers, because unsafe work places are created.

Process

Transpower reviews, weekly, all notified consents on a national basis and submits on relevant consents.

There are significant costs to Transpower to submit on resource consents, seek conditions of consent, appeal decisions, etc.

There are increased costs from requirements for line inspections and patrols, and more work for field officers. (Transpower’s contractors undertake routine sixmonthly patrols to look for encroachments or other threats to the operation of lines.)

There is increased risk of reverse sensitivity issues (eg, more people living nearby, which leads to complaints about the operation of the grid, such as objections to resource consents, requirements for electric and magnetic field (EMF) readings, or health and safety assessments).

General

This activity can result in costs due to: repair/rectification; loss of supply; effects on network operations/security of supply; increased risks to public safety; and increased risks to network operations. A recent example includes an event in October 2009 where a mobile plant carrying shipping containers came into contact with the Henderson- Otahuhu A (220kv) line in Auckland, resulting in loss of supply to approximately 280,000 customers.

Third-party activity costs relate to increases in development or activity in close proximity to line corridors.

Transpower’s records show that third-party incidents resulted in supply interruptions of 311 MWh of non-supply (1996–2006) (this relates to total interruptions caused by any third-party event).

This equates to $6.22 million (using the Electricity Commission’s value of lost load calculations of $20,000 per MWh). However, this value is contested (as being too low) by local lines distributors and will vary significantly depending on where supply is removed (eg, rural or urban, or direct industry supply).

Costs to raise conductors as the result of building occurring under lines

Options to raise conductors in order to correct a breach of NZECP34 (eg, where separation distances are reduced as a result of third-party activities) vary significantly, but can cost up to $135,000 per tower (depending on the work and type of tower, and not including Transpower staff time and other costs).

Costs of property acquisition (as an alternative to managing building within the corridor)

The cost of acquiring property rights for the existing 12,000-kilometre network has been estimated by Transpower at $7 billion. Notwithstanding the fact that Transpower already has statutory rights to operate its land, incurring this cost is not seen by Transpower as a feasible solution.

Process costs

There are the costs to Transpower from staff reviewing and responding to nationally notified consents (relating to a range of third-party activities).

All of Transpower’s processes are affected by underbuilding. For example, where a tower is located on one lot with one interested party, due to encroachment there may now be 15 landowners or affected persons who must be negotiated with to achieve access, inform about maintenance, remove or repair structures to get machinery to the site, etc. This is a substantial cost in terms of time, money and effort.

There are significant costs to address underbuilding issues (eg, going through RMA stop-works procedures). For example, in one territorial local authority in Auckland, building platforms were established within 3 m of a tower, approved by the council, despite a Land Information Memorandum (LIM) advice note referring to compliance with NZECP34.

There were significant process costs to rectify this one example of underbuilding.

Also refer to the ‘Consequences’ column for process costs.

Excavation (eg, for gravel extraction) causes destabilisation of the assets.

Deposition can create hazards by reducing safe ground-clearance distances.

Examples

In 2002 gravel extraction works on the West Coast undermined the stability of existing poles. Transpower’s involvement to rectify the situation (which involved seeking buttressing or new batters) is ongoing (five years plus). (See under ‘Costs’.)

Frequency

Excavation that destabilises assets occurs about five times per year around the country.

Material is commonly deposited under lines around the country, in breach of NZECP34.

Risks to structural integrity – the tower/pole may be destabilised, and may cause the structure failure (fall).

Costs of rectification – the tower/ pole may be removed, requiring replacement.

Deposited material presents electrical safety risks to the public.

Excavation and deposited material increase the risk of a faults or flashovers, thus posing a risk to the functioning of the network.

Risks to the public include:

• risk of injury/loss of life from faults caused by encroachment into the safe separation distance.

Risks to assets/system security include:

• the risk resulting from faults to lines, or destabilisation of towers.

There are health and safety risks to contractors because unsafe work situations are created for routine maintenance jobs (eg, road stoppages, traffic management).

General

This activity could result in costs due to: repair/rectification; loss of supply; effects on network operations/security of supply; and increased risks to public safety.

Costs to rectify (eg, raise conductors as result of building occurring under lines)

Options to raise conductors to correct a breach of ECP34 (eg, where separation distances are reduced as the result of deposition of material) vary, but can cost up to $135,000 per tower (depending on the work and type of tower, and not including Transpower staff time and other costs). For example, one landowner built up piles of rubble that have cost approximately $100,000 to remedy.

Costs are also incurred to strengthen foundations or recreate batters and/or restabilise.

Process costs

There are significant additional process costs for routine maintenance work (eg, requirements to remedy NZECP34 breaches may require inspections, surveys of breaches, road stoppages, traffic management plans, etc as a result of new earthworks or new roads being established under lines, as occurred in Auckland).

Transpower staff, contractors, consultants and lawyers are involved in processes (eg, enforcing NZECP34 requirements/remedying hazards).

Risks to grid operation

Tower destabilisation may require remediation works to the tower.

Loss of a tower may result in service disruption/line outage, which may require load shedding (ie, blackouts), which incurs significant cost to urban areas and industry.

There are process costs to obtain resource consents/property access to remedy affected towers/poles. This could vary between very low costs (eg, time, phone calls) to hundreds of thousands of dollars to resolve access or to obtain the RMA approvals required to undertake works).

Particulate discharges (dust, smoke)

Particulate matter such as dust from earthworks, emissions from industry, or burn-off from farming activities can build up on transmission equipment.

Example

In January 2007 in Auckland, sparking insulators caused a fire service call-out and evacuation of residences under lines. The line was taken out of service and the insulators were cleaned.

Frequency

This is difficult to estimate. All development, burn-off etc near lines will result in some level of deposit on equipment. This is monitored as part of maintenance (regular line inspections and condition assessments), and specific insulator washing programmes are instigated where needed.

Dust or particulate build-up from earthworks or discharges can build up and corrode equipment.

This increases the risk of circuits tripping or flashovers, resulting in loss of supply of electricity to customers.

An increased risk of electrical hazard means an increased risk to public safety, particularly where the public has located within the line corridor.

This activity requires an increase in maintenance costs (eg, through washing insulators).

Risks to public safety

Particulate build-up can result in arcing of insulators, causing sparking, resulting in increased risks to public safety. This risk is closely associated with the core issue of development occurring within the corridor.

General

This activity could result in costs due to: repair/rectification; loss of supply; effects on network operations/security of supply; increased risks to public safety; increased risks to network operations.

Risks to grid operation

Additional maintenance may be required (eg, washing of insulators), which can incur significant costs.

There is increased risk of flashovers, which can cause line faults, resulting in costs to system security.

The main areas of concern relate to plantation forestry (commercial or small-scale life-stylers) and rural areas, such as shelterbelts and bush. There are fewer concerns with landscaping planting in urban areas (although this varies from region to region).

Example

In 2004, on the Glenbrook deviation line, a shelter belt tree was growing too close to conductors, and flashover caused current to be induced along a fenceline. Around 300 m of shelterbelt burned. The fire service was called out. There was no outage on the line and no other damage to property.

Frequency

Vegetation caused an estimated 85 hours worth of equipment outages (lines and substations) over 1996–2006, resulting in supply interruptions totalling 50 MWH over that period.

Risks to the public include:

• risk of injury caused by fire or other flashover effects (including induced current)
• loss of private property (eg, shelterbelts burned)
• cost of call-out of emergency services.

Risks to assets/system include:

• faults or outages as the result of fires, flashovers, or direct contact with lines
• system security consequences where faults occur (which increases the load on alternative circuits).

Risks to processes include:

• significant costs for line patrols to inspect, maintain and trim any vegetation growing too close to lines, which is exacerbated when trees are purposely planted within the Tree Regulations zone (eg, shelterbelts).

General

Vegetation management costs are incurred across Transpower’s eight regions on an annual basis. For example, vegetation management is estimated to cost $2 million/year in the Auckland region.

In addition to ongoing management costs, vegetation can cause costs in terms of supply outages or equipment failure. Third-party vegetation-related incidents caused supply interruptions totalling 50 MWh (valued at $1 million) between 1996 and 2006. Thirdparty vegetation-related incidents also caused 85 hours of equipment unavailability, resulting in reduced security of supply over this period.

Mobile plant

The operation of mobile plant (such as crane or forklift) can cause significant risk to the safety of the public and operation of the network. This risk is closely associated with allowing development within the corridor, because mobile plant is used in association with new buildings or industry operation.

Example

In 2005, a concrete boom struck a line in Auckland, tripped the line (caused a fault), and earthed to ground, resulting in significant risk to the public and significant damage to the mobile plant itself.

Frequency

It is estimated that mobile plant operation causes approximately eight incidents/ faults per year on a national basis and results in approximately 100 enquiries (eg, process costs) a year on a national basis.

Risks to the public include:

• significant risks to safety and property
• risk of injury or loss of life
• cost of emergency services call-outs.

Risks to assets/system include:

• significant risk of damage to structures/structural integrity
• significant risk to the plant operator and the wider public, because faults can earth to ground (resulting in electrical hazard risk if nearby)
• significant risk to the security of supply, because contact with lines can disrupt or disable the transmission line.

Process costs include:

• field officers responding to public enquiries (estimated to be approximately 100 per year nationwide).

General

This activity could result in costs due to: repair/rectification; loss of supply; effects on network operations/security of supply; increased risks to public safety; and increased risks to network operations.

Process costs arise from Transpower responding to enquiries, conducting earth-conductor surveys and responding to incidents.

Costs to grid operation

Line outages may require load shedding (which has significant cost to urban areas/industry).

Transpower has recorded that third-party incidents involving cranes and machinery (including forestry machinery) between 1996 and 2006 resulted in 58 MWh not supplied, valued at $1.16 million (based on the Electricity Commission calculation of the MWH value of lost load), and 174 hours of equipment unavailability. As the majority of mobile plant use is associated with construction or the operation of industry, the risk of incurring these costs is significantly reduced if underbuilding does not occur in the first instance.

Subdivision (note that in terms of effects on the network, this activity is inextricably linked to building / development)

Frequency

Transpower’s records show that approximately 633 new land parcels (subdivisions) were established between 2004 and 2006 within a zone of 25 m either side of the line. Any number of buildings may be established on these parcels. This total does not include existing land parcels and what could be built on those. It is understood that these records are likely to be an underestimate.

Transpower estimates that new NZECP34 non-compliances may be occurring at approximately 750 per year (around the country).

Transpower lodged 79 submissions to notified subdivision consents over the 2005/06 year.

Transpower also made submissions on structure plans (private plan changes or council led) – approximately 15 in 2006.

Physical

Increased subdivision can facilitate significant building encroachment under lines, because building on a subdivision often does not require resource consent (therefore Transpower does not become aware until it is built).

Increased subdivision can result in increased safety risk to the public, violations of Tree Regulations as subdivisions are landscaped, and lower amenity outcomes (residential development under lines).

Increased subdivision and development increases the time, effort and cost of routine line patrols (eg, fences may have to be dismantled, vegetable gardens reinstated, etc).

Process

Transpower has significant involvement in the submission/council process. As a result, either development is set back to meet the conditions of consent, or those conditions are not imposed, resulting in electrical risks to the network’s operation, public well-being, and property.

There are operational implications because all future works are hampered/affected by increased activity (buildings/structures/risks) within the corridor.

General

There are Transpower staff and process costs due to involvement in resource consent, plan change and structure plan processes on a national basis.

(Note: These costs overlap with ‘building’ activity because most of the subdivision submissions raise issues to do with encroachment and managing the underbuilding issue.)

Water and other hazards (damming and diverting, swimming pools

Example

Dams are established upstream (and in the path) of assets.

Frequency

This is mainly an issue in the South Island. It has low frequency but high consequence.

Physical risk

There is the potential to damage or destroy structures if dams break.

Process risk

Reinstatement of structures involves a significant number of Transpower staff (eg, environmental, field services, legal, and associated costs).

General

This activity could result in costs due to repair/rectification; loss of supply; effects on network operations/security of supply; increased risks to public safety; and increased risks to network operations.

Fencing

Metallic fences can conduct fault currents if they are near a line support structure (tower/pole).

Frequency

There are numerous fences erected in breach of NZECP34 in rural and urban situations around the country.

Safety risks

There is a risk to the public from current being induced along fences that are located too close to towers/poles. This could cause shocks even at significant distances away from towers/ poles.

Process risks

Fences around towers or within the transmission corridor have to be removed, repaired or replaced to get machinery in to undertake routine maintenance works. This creates significant additional time and process costs.

Note: This risk is closely associated with allowing subdivision and development within the corridor, as fences are erected in association with new buildings or industry.

To grid operation

A line fault or outage reduces the security of the line, and may require load shedding (which has a significant cost to urban areas or industry).

Process costs

Fences around towers or within the transmission corridor have to be removed, repaired or replaced to get machinery in to undertake routine maintenance works. This creates significant additional time and process costs.