Daily Security of Supply Updates

We have specific duties to monitor, analyse and, if required, manage dry winter situations.

We will keep reporting on this webpage and continue to update commentary as we progress through the winter months. 

The hydro risk curves and simulated storage trajectories were updated on 30 May.

This page is updated on business days and was last updated on 28 June with data up to midnight 27 June 2017. 

Storage levels

The following graph shows change in controlled hydro storage since 1 May 2017.  North and South Island have been separated so that change in each island can be shown against total change for the country. Further details on storage levels can be found on our Hydro Risk Curve page that is also updated on business days.  

Thermal generation

The chart above shows the recent thermal generation quantities versus the nameplate capacity (excluding Whirinaki generation). The red bars show the weekly average thermal generation from 2 and 3 weeks ago, the green bar shows the average thermal generation this time last week and the blue bars show average thermal generation over the past week, with the shaded area showing this week’s average generation for comparative purposes.

Thermal generation is up from last week.

Hydro generation

The chart above shows the recent hydro generation quantities versus the nameplate capacity (includes only Waikato, Waitaki, Clutha and Manapouri hydro schemes). The red bars show the weekly average hydro generation from 2 and 3 weeks ago, the green bar shows the average hydro generation this time last week and the blue bars show average hydro generation over the past week, with the shaded area showing this week’s average generation for comparative purposes.

Hydro generation is about the same as last week.

North Island wind generation

The chart above shows the recent North Island wind generation quantities versus the nameplate capacity. The red bars show the weekly average NI wind generation from 2 and 3 weeks ago, the green bar shows the average NI wind generation this time last week and the blue bars show average NI wind generation over the past week, with the shaded area showing this week’s average generation for comparative purposes.

North Island wind generation is up from last week.

South flow constraints

The chart above shows information on the main constraints that affect the ability of the system to transfer power south, and the magnitude of the price separation between islands; daily data is shown for the week ending yesterday. The HVDC south constraint is simply a measure of HVDC south flow compared to the maximum capacity of 850 MW (sent). 
The LNI (lower North Island) TX (transmission) constraint is the Wellington Stability constraint versus the constraint maximum of 1047 MW. Price separation is the difference in price between the North Island and South Island during south flow (north flow price separation is not shown). Note, HVDC south transfer can also be limited by reserve constraints. However, we are assessing how to best present reserve constraints as these changed with the implementation of NMIR. We will add this information to the chart soon.

The chart above shows information on the main constraints that affect the ability of the system to transfer power south, and the magnitude of the price separation between islands; data shown is for yesterday by trading period. The HVDC south constraint is simply a measure of HVDC south flow compared to the maximum capacity of 850 MW (sent). 
The LNI (lower North Island) TX (transmission) constraint is the Wellington Stability constraint versus the constraint maximum of 1047 MW. Price separation is the difference in price between the North Island and South Island during south flow (north flow price separation is not shown). Note, HVDC south transfer can also be limited by reserve constraints. However, we are assessing how to best present reserve constraints as these changed with the implementation of NMIR. We will add this information to the chart soon.

Inflows

The above charts shows the most recent inflows the North Island (Taupo), and the South Island (Waitaki, Clutha and Manapouri) catchments, respectively and compares them to the distribution of historical inflows.