Dynamic voltage stability of auckland metropolitan load area

The upper North Island (UNI) region of New Zealand is connected by long 220 kV transmission lines to generation centers in the south. Analysis shows that power transmission to the UNI will shortly become constrained by voltage stability problems. Dynamic voltage simulations are performed to calculate the transfer limits. The paper describes the modeling assumptions and the performance criteria used for establishing the dynamic voltage stability limit. The distribution system and the loads connected to each grid exit point are represented by a reduced equivalent network containing aggregated models of motor loads, capacitors, and static loads. When a severe contingency occurs a certain percentage of the load will unavoidably disconnected. The proposed performance criteria ensure that the avoidable loss of load is minimized and cascade failure is prevented. Dynamic voltage stability limits are calculated based on the modeling assumptions and the performance criteria. The voltage recovery performance is particularly sensitive to load modeling assumptions.