2. The Problems with Development near High-voltage Transmission Lines

2.1 What are the risks created by development and activities near the transmission network?

The need to manage development that poses a risk to, or is at risk from, the efficient operation of the transmission network was given significant consideration by the Ministry for the Environment and Board of Inquiry on the proposed National Policy Statement on Electricity Transmission during the development of the NPSET.¹ These two concepts were carried through to the development of Policy 10.

The main areas of risk arising from incompatible development and activities near the transmission network are:

• risks to the health, safety and well-being of persons and property
• risks to the operation of the transmission network
• risks to amenity.

Transpower itself has recognised these risks and has consistently opposed development occurring in close proximity to the network for these reasons. It also undertakes routine line inspection and maintenance to prevent and manage risks. Nevertheless, the encroachment of development into the line corridor remains a significant issue – with corresponding risks.

2.2 Risks to persons and property: health, safety and well-being

NPSET Policy 11 requires the use of a buffer corridor to manage the issue of sensitive activities being established too close to the existing transmission network. The risks posed by the network, and by the effects of others’ activities on the network, are articulated in the Ministry of Economic Development’s Reference Group report² and are summarised below.

2.2.1 Risk of electrical hazard or injury

The main risk from development occurring too close to the transmission network is the creation of electrical hazard, due to either direct contact with lines or electricity arcing to contact structures, leading to injury to persons or damage to property. Risk of electricity earthing around transmission towers is a particular concern, as electricity can earth via support structures (towers or poles) or other objects coming into contact with the lines, or via ‘flashover’,³ where electricity leaps to a structure such as a building. The risk of loss of life or injury therefore increases where buildings and other development or activities are located close to conductors or towers. An additional risk is from equipment or line components falling while in operation or when work is being undertaken.

Following are some examples of where these risks have been realised.

• In 2005, a concrete boom controlled by a mobile plant operator, working in an industrial area in Auckland, came into contact with the conductors of a line. This contact caused the line to trip, earthing via the mobile plant to ground, thus creating an extremely dangerous situation around that ground area, which included a school crossing. Had the development of the land under the lines been better managed this risk could have been minimised.
• In 2008, an incident occurred resulting in loss of life when an irrigator came into contact with live overhead lines. Had adequate separation distances been in place this death would have been avoided.
• In February 2009, a joint failure on the Otahuhu-Whakamaru-A (220kV) line resulted in a length of line falling on a residential area in Auckland, affecting 16 houses and causing damage to property (but with very real risk to public health and safety). Had there been a buffer or setback in place preventing residential development from occurring beneath the transmission lines this risk would have been eliminated, or at least significantly reduced.
• In October 2009, a mobile plant (forklift) carrying shipping containers within an industrial site under the Henderson-Otahuhu A (220kv) line in Auckland, came into contact with the line resulting in loss of supply to approximately 280,000 customers. The risk of line contact and service failure was directly related to the establishment of the industrial use under the line in the first instance.
• Other incidents have included tools or equipment falling during the routine maintenance of overhead lines.

The risk of injury or electrical hazard from such events increases significantly with increased development or activity within the corridor. Transpower considers this risk to persons and property unacceptable, and incompatible with the safe and efficient operation of the transmission network. Transpower believes its rigorous maintenance and safety standards are being undermined by ongoing development under, and close to, transmission lines. The prime intention of the NPSET is to prevent the exacerbation of these risks.

2.3 Risks to the transmission network

The national benefits of transmission are specifically recognised by the NPSET, in particular in Policy 1. Risks to the transmission network pose a threat to the environment that must be managed as part of promoting the sustainable management purpose of the RMA, and more specifically by the dual purpose of Policy 10 of the NPSET. Risks to the transmission network can occur as a result of failing to provide for maintenance, and by failing to prevent certain activities from locating in a position where they present a threat to the line.

2.3.1 Risks associated with ‘reverse sensitivity’

The term ‘reverse sensitivity’ was defined by the Environment Court in Auckland RC v Auckland CC⁴ as “the effects of the existence of sensitive activities on other activities in their vicinity, particularly when they lead to restraints in the carrying on of those other activities”. That case also confirmed that it was legitimate to make rules to restrict the location of activities sensitive to low air quality, in or adjacent to areas where air quality was low (ie, that in principle, it was acceptable to introduce rules to address reverse sensitivity issues). This principle has subsequently been confirmed by a number of Environment Court decisions.

In relation to the transmission network, allowing development near or under existing transmission lines may introduce a more sensitive activity (eg, residential use) to the area. This may result in actual or perceived health, safety and operational risks. Encroachment may also lead to restrictions being placed on the continuation or upgrading of existing infrastructure due to concerns about health and safety, such as electromagnetic health effects, noise nuisance (eg, from substations or lines), or amenity concerns. These may, in turn, create an undue restriction on the ability for the assets to be used to meet forecast demand.

2.3.2 Risks of disruption to transmission, and effects on security of supply

NPSET Policy 10 requires that activities be managed to ensure that (among other things) the operation of the transmission network is not compromised. Just as the transmission network can pose a risk to the health and safety of people and property, so third-party activities and development can pose a significant risk to the operation of the network, which risks security of supply. Faults or outages on a line may be caused by physical contact with or proximity to conductors from other objects (trees, buildings, mobile plant), or the deposition of material (such as dust) that causes a line to flashover/fault. This may cause a fault or outage, and will have flow-on effects for system security, because taking a line out of service overloads the rest of the network.

Transpower’s records show that third-party incidents were responsible for supply interruptions of 311 megawatt hours of non-supply over the period 1996–2006 (this relates to total interruptions caused by any third-party event). This equates to a cost of $6.22 million, using the Electricity Commission’s value of lost load calculations, $20,000 per megawatt hour. A recent example is the power outage in October 2009 caused by a forklift carrying a container coming into contact with the 220 kilovolt transmission line between Otahuhu and Henderson. The incident resulted in the loss of electricity supply to North Auckland and Northland (about 280,000 customers). (For other specific examples, refer to appendix 1.)

The implications of a network fault include potentially hours of loss of electricity supply while faults are corrected. An asset fault could also cause an increase in the price of electricity. Depending on the location of the fault and the affected equipment, more pressure is placed on the remaining in-service transmission system. A reduction in the level of transmission equipment available to the electricity market could result in binding transmission constraints and, consequently, increased electricity prices.

Transpower (as the system operator) responds to and manages asset faults in its role as a reasonable and prudent operator. The system operator manages the security impacts of the fault in real time to ensure the security of scheduling and dispatch is not compromised. Time is also taken to reassess the security of planned outage and commissioning work in light of the fault. Afterwards, the system operator reviews the circumstances surrounding events that have had a material impact on its operations to determine appropriate process improvements and other actions to reduce the likelihood and impact of a recurrence.

However, despite Transpower’s best efforts, faults continue to occur as a result of third-party encroachment in the transmission corridor.

2.3.3 Risks to structural integrity

NPSET Policy 10 requires that activities be managed to ensure that (among other things) the operation of the transmission network is not compromised. Development under, or too close to, transmission lines can also affect the structural integrity of transmission network components. Examples include the physical undermining of poles, towers or conductors by excavation of earth or scouring through the diversion of water; particulate build-up from smoke, or direct risks from fires, causing electrical hazard risks due to fires being too close to lines; or direct contact with conductors. For example, in 2003 excavation as part of construction at a site on the HENROS line (Auckland) extended to 3 metres below a tower grillage and 2 metres from a tower leg. This excavation put at risk the structure and security of the line, and had operational implications in terms of security of supply to Auckland. This incident incurred significant cost, time and effort to rectify, including engineers’ site assessments, site visits, infill and replacement of necessary earthworks. Supply to significant areas of Auckland was also at risk.

More detailed examples of this type of risk are provided in appendix 1.

2.3.4 Risks to the ability to inspect and maintain lines (conductors) and support structures

NPSET Policy 10 requires that activities be managed to ensure that (among other things) the operation and maintenance of the transmission network are not compromised. The encroachment of building and development within the line corridor can create a physical barrier to the network, preventing, for example, machinery from accessing towers, foundations or conductors along the line route. This can make vital ongoing maintenance and repair difficult or impossible. As well as creating hazardous situations for those under the lines, physical constraints along the line route can have significant time implications for routine line inspections, routine maintenance, and undertaking line upgrades. Preventing or inappropriately constraining the inspection and maintenance of existing lines does not promote the sustainable management of this important physical resource and is contrary to the NPSET, in particular Policies 1, 2 and 10.

2.3.5 Risks to the ability to undertake line upgrades

NPSET Policy 10 requires that activities be managed to ensure that (among other things) the development of the transmission network is not compromised. The encroachment of development into the transmission corridor can at worst foreclose, and at best significantly constrain, opportunities to upgrade those assets to meet future demand. The alternative to upgrading existing lines is to build new lines. However, these lines would still have to link the point of supply (generation) to demand nodes (substations or major users), which introduces a new set of adverse environmental effects. The inability to upgrade within the existing line corridor does not provide for the sustainable management of the resource (confirmed by the NPSET as being of national importance).

2.4 Amenity risks

Encroachment of development into the transmission corridor does not provide a good level of amenity generally, and this is the case for residential development in particular. Submissions from local authorities at the NPSET hearings commonly referred to a desire to prevent residential development from being established too close to lines on grounds of quality of amenity, as well as health and safety concerns.

Transpower’s Guide for Development near High-voltage Transmission Lineshttp://www.transpower.co.nz/landowner-guides was developed to provide design solutions and encourage higher levels of amenity for compatible development near transmission lines. Minimising the potential for adverse effects on amenity, including appropriate design, is one means of addressing potential adverse effects under the RMA.

2.5 Summary

Policies 10 and 11 require that activities be managed, including through the use of a buffer zone, to avoid reverse sensitivity effects and ensure the transmission network is not compromised. The management of the effects of third-party activities on the national grid is necessary to ensure that:

• the public and property are reasonably protected from live transmission lines
• integrity of supply is maintained by ensuring that no activities that may affect or damage the line are located beneath, or in too close proximity to, the line
• existing lines can be operated, which includes a requirement for assets to be routinely inspected and maintained
• the option of upgrading existing lines, rather than building additional lines, to meet increased electricity demand is not precluded by the development of buildings under or immediately adjacent to existing lines
• a minimum level of amenity is retained for those living in close proximity to lines by not being located directly underneath lines.

The appropriate management of development and activities in close proximity to the transmission network would achieve these outcomes, thus giving effect to NPSET Policies 10 and 11. In this way, when promoting the sustainable management of natural and physical resources in resource management decisions, people and communities can provide for their social, economic and cultural well-being and for their health and safety, while providing for the reasonably foreseeable needs of future generations and avoiding, remedying or mitigating adverse effects. Conversely, if third-party effects are not appropriately managed, then the purpose of the RMA will not be met.