Our electricity transmission network includes a number of special protection schemes.
Special protection schemes allow our equipment to be operated to a higher pre-event capacity limit in a secure state. They operate after an event on the power system (such as a fault) to prevent abnormal system conditions occurring, such as overload or instability. Further, special protection schemes may be used to control electricity generation, load, or other network components.
Our latest information on each special protection scheme in our network is available below. For further information or if you have questions about these, please email [email protected].
Special Protection Scheme Overviews
| Scheme name | Island | Grid Zone | Transpower region | Outage region | Normally Enabled |
|---|---|---|---|---|---|
| Hepburn Road-Mount Roskill 110kV Overload Protection Scheme | North | GZ01 - Northland | Auckland | NNI | Yes |
| Penrose Circuit Overload Protection Scheme | North | GZ02 - Auckland | Auckland | NNI | No |
| Penrose Reactor Bypass Scheme | North | GZ02 - Auckland | Auckland | NNI | Yes |
| Penrose Transformer Overload Protection Scheme | North | GZ02 - Auckland | Auckland | NNI | No |
| Arapuni North Runback Scheme | North | GZ03 - Hamilton | Waikato | NNI | Yes |
| Arapuni South Runback Scheme | North | GZ03 - Hamilton | Waikato | NNI | No |
| Arapuni-Hangatiki Circuit Overload Protection Scheme | North | GZ03 - Hamilton | Waikato | NNI | Yes |
| Arapuni-Kinleith Overload Protection Scheme | North | GZ03 - Hamilton | Waikato | NNI | No |
| Cambridge Supply Transformer Overload Protection Scheme | North | GZ03 - Hamilton | Waikato | NNI | Yes |
| Hangatiki Supply Transformer Overload Protection Scheme | North | GZ03 - Hamilton | Waikato | NNI | Yes |
| Edgecumbe-Kawerau 1-2 Overload Protection Scheme | North | GZ04 - Edgecumbe | Bay of Plenty | NNI | Yes |
| Edgecumbe-Owhata-2 110kV Overload Protection Scheme | North | GZ04 - Edgecumbe | Bay of Plenty | NNI | Yes |
| Kaitemako Intertrip Scheme | North | GZ04 - Edgecumbe | Bay of Plenty | NNI | Yes |
| Maraetai Runback Scheme | North | GZ04 - Edgecumbe | Waikato | NNI | Yes |
| Te Mihi Generation Intertrip Scheme | North | GZ04 - Edgecumbe | Central North Island | SNI | No |
| Harapaki Anti-Islanding Scheme | North | GZ05 - Hawkes Bay | Hawkes Bay | SNI | Yes |
| Redclyffe Transformer Overload Protection Scheme | North | GZ05 - Hawkes Bay | Hawkes Bay | SNI | Yes |
| Tauhara Anti-Islanding Scheme | North | GZ05 - Hawkes Bay | Hawkes Bay | SNI | Yes |
| Hawera Automatic Under-Voltage Load Shedding Scheme | North | GZ06 - Taranaki | Taranaki | SNI | No |
| Hawera Transformer Overload Protection Scheme | North | GZ06 - Taranaki | Taranaki | SNI | No |
| Bunnythorpe-Mataroa Circuit Overload Protection Scheme | North | GZ07 - Bunnythorpe | Central North Island | SNI | Yes |
| Bunnythorpe-Woodville 1 and 2 Circuit Overload Protection Scheme | North | GZ07 - Bunnythorpe | Central North Island | SNI | Yes |
| Marton-Whanganui Circuit Overload Protection Scheme | North | GZ07 - Bunnythorpe | Central North Island | SNI | Yes |
| Tokaanu Circuit Overload Protection Scheme | North | GZ07 - Bunnythorpe | Central North Island | SNI | Yes |
| Whanganui Under-Voltage Load Shedding Scheme | North | GZ07 - Bunnythorpe | Taranaki | SNI | No |
| Central Park Transformer Overload Protection Scheme | North | GZ08 - Wellington | Wellington | SNI | No |
| Mangamaire Overload Trip and Autochangeover scheme | North | GZ08 - Wellington | Central North Island | SNI | No |
| Wilton 110 kV Bus Split Scheme | North | GZ08 - Wellington | Wellington | SNI | Yes |
| Blenheim-Kikiwa 110 kV Circuit Overload Protection Scheme | South | GZ09 - Nelson | Nelson-Marlborough | SI | No |
| Kikiwa -Stoke-3 Circuit Overload Protection Scheme | South | GZ09 - Nelson | West Coast | SI | No |
| Kikiwa -Stoke 220 kV Circuit Outage Intertrip Scheme | South | GZ09 - Nelson | West Coast | SI | No |
| Timaru Supply Transformer Overload Protection Scheme | South | GZ11 - Canterbury | South Canterbury | SI | No |
| Temuka Supply Transformer Overload Protection Scheme | South | GZ11 - Canterbury | South Canterbury | SI | Yes |
| Coleridge Intertrip Scheme | South | GZ12 - West Coast | Canterbury | SI | No (Manawa scheme yes) |
| Coleridge-Hororata Circuit Overload Protection Scheme | South | GZ12 - West Coast | Canterbury | SI | Yes |
| Hororata Automatic Under-voltage Load Shedding Scheme | South | GZ12 - West Coast | Canterbury | SI | Yes |
| Aviemore-Benmore Circuit Overload Protection Scheme | South | GZ13 - Otago | South Canterbury | SI | Yes |
| Cromwell-Frankton Circuit Overload Protection Scheme | South | GZ13 - Otago | Otago-Southland | SI | Yes |
| Oamaru-Waitaki Circuit Overload Protection Schemes | South | GZ13 - Otago | South Canterbury | SI | Yes (between 1st Oct to 30th April) |
| Edendale Circuit Overload Protection Scheme | South | GZ14 - Southland | Otago-Southland | SI | Yes |
| Edendale Transformer Overload Protection Scheme | South | GZ14 - Southland | Otago-Southland | SI | Yes |
| Gore Circuit Overload Protection Scheme | South | GZ14 - Southland | Otago-Southland | SI | No |
| Halfway Bush T6 Reverse Power Protection Scheme | South | GZ14 - Southland | Otago-Southland | SI | No |
| Manapouri Generation Intertrip Scheme | South | GZ14 - Southland | Otago-Southland | SI | Yes |
| North Makarewa Capacitor Bank Intertrip Scheme | South | GZ14 - Southland | Otago-Southland | SI | No |