Shoulder Rating
Transpower will be implementing a new season (Shoulder Season) to its line rating methodology on 15 March 2010. We will apply the Shoulder Season to all transmission circuits. We will not apply the Shoulder Season to transformers or other primary plant ratings.
NB - Shoulder Season is in addition to the existing winter and summer seasons.
The ratings are based on the Transpower standard circuit rating methodology, which assumes an ambient temperature of 30°C during the summer period, 25°C during the shoulder period and 20°C during the winter period.
The new ratings periods are as follows:-
- shoulder ratings apply from 07:00 on 15 Mar to 06:59 on 10 May
- winter ratings apply from 07:00 on 10 May to 06:59 on 20 Oct
- shoulder ratings apply from 07:00 on 20 Oct to 06:59 on 01 Dec
- summer ratings apply from 07:00 on 1 Dec to 06:59 on 15 Mar
| Season | Day (07:00 - 20:59) | Night (21:00 - 06:59) |
|---|---|---|
| Summer | Summer (30°C) | Winter (20°C) |
| Shoulder | Shoulder (25°C) | Winter (20°C) |
| Winter | Winter (20°C) | Winter (20°C) |