Project: Upper Island Reactive Power Study

Service: HVAC

Client: Transpower

Country: New Zealand

Year: September 2012 - January 2013


Transpower is planning to install a Reactive Power Controller (RPC) in their Upper North Island (UNI), with the goal of maintaining steady state 220kV and 110kV voltages according to setpoints, as well as sufficient reactive power reserves in the area.  A similar such RPC exists in the Southern Island near Christchurch. The purpose of the RPC studies was to see if this RPC design could work in such a tightly coupled system, and if so, how it would be best configured with the equipment available to be controlled, including generators, several STATCOMs, switched capacitors and transformers with on-load tap-changers.

TGS study services:

  • Reactive Power Studies — performed using DIgSILENT Powerfactory
    • To determine the robustness of the RPC design, and to determine how the RPC should be configured with the available static and dynamic reactive power sources in the system
    • Developed a quasi-steady state simulator in Powerfactory to run the Upper North Island power system through several typical 24 hour day load cycles, with the RPC modeled to control the 220 kV and 110 kV voltages as well as the area reactive power reserves


This was a very technically challenging (and interesting) project. It was not a simple task to get the quasi-steady state simulator to work well with the RPC, and then to come up with a design and suggestions as to how to ensure the RPC properly utilized all of the available reactive power sources, while maintaining system voltages within limits and while maintaining reactive power reserves within limits. But in the end, the project was a success, and everyone involved in the project learned a lot.