Daily Security of Supply Updates

We have specific duties to monitor, analyse and, if required, manage dry winter situations. Dry winters are not uncommon, and are a by-product of operating a power system with such a high proportion of hydro generation.

As the System Operator, we are required to provide information, and short- to medium-term forecasting on all aspects of security of supply; and manage any supply emergencies. This means we take an active role of analysing a dry winter situation as it develops (and publish the results of our analysis), and open a dialog with key stakeholders to ensure we understand the situation from all angles.

The risk curves currently shows we are close to the 1% HRC which ‘activates’ a dry winter.  This essentially means we have been using water faster than we are receiving it (ie limited rainfall), and therefore storage has been declining.

It does not mean however that there is a shortage of hydro generation or any other generation. It means that we are increasing our programme of work to include monitoring the situation closely, reviewing our modelling assumptions, talking with analysts at major generators and initiating more detailed daily reporting.

Although we don’t expect storage to pick up in the short to medium term, we do not anticipate that any conservation campaigns, will be required. This is because we are relatively late in the year in terms of winter energy risk and it’s likely we have sufficient water in the storage lakes to make it through to spring inflows.

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

This page is updated on business days and was last updated on 24 May with data up to 23 May 2017. 

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 down on 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 down on 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.