The objective of the transmission risks NES is to establish consistent and reasonable controls on activities that could adversely affect the transmission lines, or pose a risk to the person undertaking the activity.
Objective
Scope
The proposed standard would set controls on activities carried out in the immediate vicinity of transmission lines that could adversely affect the lines or affect public safety. The proposed standard would apply to anybody other than the line owner undertaking activities adjacent to transmission lines that are not related to transmission operation, maintenance and upgrade. Earthworks and structures adjacent to transmission lines required as part of line maintenance and enhancement and undertaken by the line owner are controlled by the proposed transmission activities NES.
How the proposals would work
Plans cannot be more lenient than the NES. However, the NES will state that plans can be more stringent. A rule in a plan which covers the same activity as the NES (eg, subdivisions) will be able to be more stringent than the NES, and the matters for consideration listed in the plan rule will apply. For example, a plan could specify that subdivision is a restricted discretionary activity, whereas the proposed NES specifies that subdivision near transmission lines is a controlled activity. Where an activity is not addressed in the NES, the district plan rules would continue to apply.
Table A8 shows the detailed proposals and their relationship between the proposals and existing NZECP 34 provisions or district plan rules. A key difference between RMA controls and NZECP 34 is that NZECP 34 gives the line owner the discretion to allow activities, whereas under the proposed NES the local authority would have the discretion to grant or decline resource consents.
The proposed controls are based on existing controls in the mandatory code of practice for electrical safe distances (NZECP 34) and existing provisions in district plans under the RMA. Controls on excavating and depositing materials and building boat ramps near transmission lines, and on buildings and structures near transmission support structures, are based on the electrical safe distances and matters set out in NZECP 34. In addition, controls are proposed for subdivision within 20 metres of transmission lines, based on section 11 of the RMA. These controls are based on the existing requirements in district plans.
Two options are presented for buildings and structures near conductors:
- one based on NZECP 34
- the other extending the radial electrical safe distances to a 20-metre ground-level zone within which resource consents would be required.
Option A (based on NZECP 34 safe distances)
- Buildings within the distances specified in schedule 3 pose electrical safety risks and are prohibited.
- Buildings outside the distances specified in Schedule 3 (as certified by a qualified electrical engineer) but within the distances specified in Schedule 2 require a resource consent.
Anyone wanting to build within the distances from the conductors specified in Schedule 2 (see below) must demonstrate that the safe distances in Schedule 3 would not be exceeded. The Schedule 3 distances take account of the feasibility of lines coming into contact with buildings, and take particular account of accessibility to people and exposure to hazards. - Buildings outside the safe distances specified in Schedule 2 are not regulated by the proposed NES. The distances set out in Schedule 2 (from NZECP 34) are vertical distances under conductors, and distances to the side of conductors. They contain a conservative margin of error to allow for possible line sag and swing, and vary according to span length (and a small amount of variation based on voltage). These are simple distances, so expert advice is not required.
Option B (based on 20-metre ‘consent required’ zone)
- Buildings within the distances specified in Schedule 3 pose electrical safety risks and are prohibited.
- Buildings within 20 metres of the centre of the transmission line but outside the distances specified in Schedule 3 (as certified by a qualified electrical engineer) require a resource consent.
- Buildings more than 20 metres from the transmission line are not regulated by the proposed NES. The 20-metre distance is measured from the centre of the transmission line.
Table A8: Proposed NES for transmission risks
- plans can be more stringent than the NES
- activities not covered by this proposed NES will continue to be subject to plan rules
- this proposed NES will not apply to the owner of the transmission line.
| Activity | Activity type | Matters discretion applies to (for restricted discretionary activities) | Comparison with |
|---|---|---|---|
| Excavation near support structures | |||
| 1. Excavation of the land adjacent to any pole or stay wire of an overhead conductor: |
|
|
|
| a. to a depth greater than 300 mm within 2.2 m, or which creates an unstable batter that is likely to endanger the structural stability of the transmission line support | Prohibited | n/a | The distances and requirements are consistent with existing requirements under NZECP 34. |
| b. to a depth greater than 750 mm, located at a distance between 2.2 m and 5 m. | Restricted discretionary |
|
|
| Exclusion: This does not apply to vertical holes not exceeding 500 mm in diameter at a distance of 1.5 m or greater from a pole or stay wire. | |||
| 2. Excavation of the land adjacent to any pylon supporting an overhead line: |
|
|
|
| a. at a depth exceeding 300 mm within 6 m of the outer edge of the visible foundation of the tower, or which creates an unstable batter that is likely to endanger the structural stability of the transmission line support | Prohibited | n/a | The distances and requirements are consistent with existing requirements under NZECP 34. |
| b. at a depth exceeding 3 m, located between 6 m and 12 m of the outer edge of the visible foundation of the tower. | Restricted discretionary |
| The distances and requirements are consistent with existing requirements under NZECP 34. |
| Exclusion: 1 and 2 do not apply to excavations undertaken as part of any transmission line maintenance or upgrading activities. | |||
| Deposition of material | |||
| 3. The deposition of material under or adjacent to a transmission line in a way that would reduce the height to the ground to less than the safe distances in Schedule 4 (Table 4 of NZECP 34) | Prohibited | n/a | This is a straight prohibition in both NZECP 34 and the NES, and the distances are the same. |
| Building near support structures | |||
| 4. The erection or placement of a building or structure closer to a transmission line support structure than the distances specified in Schedule 1 (Table 1 of NZECP 34) The distances are to be measured from the closest visible edge of the overhead conductor support foundation to the nearest part of the outermost part of the building or structure (See Glossary for definition of ‘building or structure’.) | Restricted discretionary |
| The distances in Schedule 1 are the same as the requirements of NZECP 34. |
| Building near conductors | |||
| Prohibited zone around conductors |
|
|
|
| 5. Building closer to an overhead conductor than the distances specified in Schedule 3 (Table ;3 of NZECP 34, electrical safe distances based on voltage and accessibility of building) | Prohibited | n/a | The distances are the same as NZECP 34 requirements. Buildings within the distances in Schedule 3 are prohibited in both the NES and NZECP 34 . |
| Option A: NZECP 34-based controls around conductors | |||
| 6A. Buildings or structures closer to the conductors than the distances specified in Schedule 2 and further from the conductors than the distances specified in Schedule 3 An engineering study undertaken by a suitably qualified electrical engineer is required to determine that the structure is located outside the distances specified in Schedule 3. | Restricted discretionary |
| The distances are the same as NZECP 34 requirements. |
| Option B: Controls on activities at ground level | |||
| 6B. Buildings or structures within 20 m of the centreline of the transmission line, but further from the conductors than the distances specified in Schedule 3 An engineering study undertaken by a suitably qualified electrical engineer is required to determine that the structure is located outside the distances specified in Schedule 3. | Restricted discretionary |
| This is very different from NZECP 34. In addition to the differences listed above, the distances are extended from the distances in the schedule to 20 m, and instead of being horizontal / vertical distances they extend to ground level. 15 district plans include a requirement that resource consent be obtained for buildings and structures within 20 m of a transmission line. |
| Subdivisions | |||
| 7. Subdivision within 20 metres of the centreline of a transmission line An engineering study undertaken by a suitably qualified electrical engineer may be required to determine that no buildings are likely to be located within the distances specified in Schedule 3 | Controlled |
| All district plans address subdivision, and this is treated variously as a controlled, restricted discretionary or discretionary activity. With one or two exceptions, resource consent is always required for subdivisions. 28 district plans specifically require resource consent to be obtained for subdivision within 20 m of a transmission line, and this is treated as a controlled, restricted discretionary, or discretionary activity. |
| Boat ramps | |||
| 8. Construction of a boat ramp within 9 m in any direction of a transmission line | Non-complying | n/a | This is a requirement of NZECP 34 with ‘prior written consent required’. Boat ramps are likely to be controlled in some way in regional plans as a coastal activity (not related to transmission). |
| Additional proposal: damming and diverting water | |||
| Damming or diverting any surface water within 20 m of a transmission line, or in a way that could put the structural integrity of the transmission line at risk Note: Comments are invited on whether damming and diverting water should be included in the NES, or whether it is already covered adequately by other requirements. | Restricted discretionary |
| This is not specifically covered in NZECP 34, but may be controlled in some regional plans. Further investigation will be needed to establish the degree of control in each regional plan, and whether this is covered under legislation related to dam safety. |
Schedule 1: Minimum safe distances between buildings and overhead electric line supports
| Circuit voltage | Pole | Tower (pylon) |
|---|---|---|
| 11 kV to 33 kV | 2 m | 6 m |
| Greater than 33 kV and less than 66 kV | 6 m | 9 m |
| Greater than 66 kV | 8 m | 12 m |
Schedule 2: Safe distances for buildings and structures from conductors without engineering advice (from NZECP 34)
| Circuit voltage | Maximum span length | Minimum distance beneath conductors under normal conditions | Minimum distance to the side of conductors under normal conditions |
|---|---|---|---|
| Not exceeding 33 kV AC | 125 | 7 | 8.5 |
| Exceeding 33 kV but not exceeding 110 kV AC | 125 | 7.5 | 9.5 |
| Exceeding 110 kV but not exceeding 220 kV AC | 125 | 8.5 | 11 |
| 275 kV DC and 350 kV DC | 125 | 8.5 | 7.5 |
| Not exceeding 33 kV AC | 250 | 8 | 12 |
| Exceeding 33 kV but not exceeding 110 kV AC | 250 | 8.5 | 12.5 |
| Exceeding 110 kV but not exceeding 220 kV AC | 250 | 10 | 14 |
| 275 kV DC and 350 kV DC | 250 | 10 | 11 |
| Not exceeding 33 kV AC | 375 | 9.5 | 20.5 |
| Exceeding 33 kV but not exceeding 110 kV AC | 375 | 10 | 21 |
| Exceeding 110 kV but not exceeding 220 kV AC | 375 | 11 | 22.5 |
| 275 kV DC and 350 kV DC | 375 | 10.5 | 18 |
| All other spans | Engineering advice required | ||
Notes:
Observance of potential conductor motion is required to ensure safe distances during construction.
Where supporting structures are not located on equal elevations, a specific engineering study may be required to ensure that distances are in accordance with Schedule 3.
Schedule 3: Minimum safe distances of conductors from buildings and other structures where specific calculation of conductor movement has been carried out (from NZECP 34)
| Safe distance conditions | Not exceeding 33 kV AC (bare or covered) | Exceeding 33 kV but not exceeding 110 kV AC (bare) | Exceeding 110 kV but not exceeding 220 kV AC (bare) | Exceeding 220 kV AC or DC |
|---|---|---|---|---|
| A: Vertically above those parts of any structure normally accessible to persons | 4.5 | 5 | 6.5 | 7 |
| B: Vertically above those parts of any structure not normally accessible to persons but on which a person can stand | 3.7 | 4.5 | 6 | 6.5 |
| C: In any direction (other than vertically above) from those parts of any structure normally accessible to persons, or from any part not normally accessible to persons but on which a person can stand | 2.1 | 3 | 4.5 | 5 |
| D: In any direction from those parts of any structure not normally accessible to persons | 1.5 | 2.5 | 3.5 | 4 |
| E: In any direction from the ground | Refer to Schedule 4 |
|
|
|
Schedule 4: Minimum safe distances of conductors from the ground
|
| Vertical distance to the ground (m) | Radial distance (m) | ||
|---|---|---|---|---|
| Circuit voltage | Across or along roads or driveways | Any other land traversable by vehicles | Any land not traversable by vehicles due to inaccessibility | In any direction other than vertical on all land |
| Not exceeding 33 kV AC | 6.5 | 5.5 | 4.5 | 2 |
| Exceeding 33 kV but not exceeding 110 kV AC | 6.5 | 6.5 | 5.5 | 3 |
| Exceeding 110 kV but not exceeding 220 kV | 7.5 | 7.5 | 6.0 | 4.5 |
| Exceeding 220 kV AC or DC | 8.0 | 8.0 | 6.5 | 5 |
Note: ‘Vehicles' includes mobile plant.
See more on...
Appendix 5: Proposed NES: activities that could put transmission lines at risk
October 2007
© Ministry for the Environment