3 August 2011

Successful Commissioning and Compliance Testing of Guthega Unit 1 Excitation System and Power System Stabiliser

The Guthega Power Station is located in the Snowy Mountains, NSW, and consists of two 42.5 MVA hydro generating units, each unit connected to the TransGrid 132kV network. Snowy Hydro has recently replaced the excitation system of Unit 1 at Guthega Power Station. The new excitation system is an Alstom CONTROGEN digital automatic voltage regulator supplied by Alstom Pacific. DIgSILENT Pacific was engaged by Alstom to perform the compliance testing of the new excitation system in June of this year.

Guthega Power Station Site Testing was performed to confirm compliance with different aspects of the Performance Standards for Guthega Power Station. The tests were performed with the unit at standstill, at speed but unsynchronised to the grid, and finally with the unit synchronised and generating power. A series of frequency and time domain tests were executed to verify the models of the new excitation system and power system stabiliser, and to confirm the performance of the new system meets the agreed Performance Standards for the Station.

The aspects of testing which are required to demonstrate compliance are as follows:

1. R2 testing of the new excitation system and power system stabiliser to verify the model and settings are correct;

2. Unsynchronised settling time to a voltage step response equivalent to 5%;

3. Synchronised settling time to a voltage step response equivalent to 5%;

4. Performance of excitation limiters;

5. Active power damping and the effectiveness of the power system stabiliser; and

6. Ceiling capability of the new excitation system.

The tests were executed in coordination with the Alstom commissioning engineers and the Snowy Hydro operators and local engineers. As the excitation system is the system being tested, the recording system is required to be independent of it. Therefore the DIgSILENT PowerFactory Monitor was used for high speed data acquisition and real time monitoring. The test recordings demonstrated excellent alignment with the modelled response which allowed for AEMO approval at each stage during testing. This assisted and complimented the commissioning engineers to ensure a quick and efficient hot commissioning schedule.

Voltage Comparison

PQ Comparison