Scope of work

GTS was invited to provide the engineering, detailed design, procurement and supply of equipment, inspection and testing, installation, commissioning and handover of the design for the replacement of the obsolete generator protection relays on Alinta Energy's TG103 Gas Turbine unit located at the Port Hedland Power Station. GTS carried out the construction, relay programming and FAT of the replacement protection panels in its Canning Vale workshop facility.

Once this was complete the new panels were transported to Alinta Energy's PHPS where the old generator protection panel for the unit was removed and the new panel installed. GTS completed the interface wiring and carried out the pre-commissioning works as per the Commissioning Test Procedure.

Project Challenges

During the online commissioning phase, several protection element operations were observed. These included the 11kV Bus Earth Fault protection on both relays and the Generator Reverse Power protection on one of the relays. Because of this Alinta Energy decided that further investigation and testing was necessary to try and determine the cause of the protection operations. GTS was engaged to carry out a suite of primary testing on the 11kV Bus cabling, 66/11kV Generator Transformer, 11/0.44kV Auxiliary Transformer, Generator current transformers, Generator voltage transformers and 11kV Bus voltage transformer to try and determine if there were genuine faults in the system.

The outcome of the testing did not reveal any issues with the 11kV Bus cabling, the 66/11kV Generator Transformer or the 11/0.44kV Auxiliary Transformer. The testing of the Generator and Star Point CTs revealed that the secondary wiring of these CT inputs into one of the protection relays had been crossed which would have caused the reverse power element to pick-up once current exceeded the pickup threshold of the element.

This error was a result of the CT secondary wiring being identified with the same numbering on both the Generator line side and Star Point side. The wiring was corrected, and the numbering was modified to rectify the issue. Once the primary testing was complete the online protection commissioning continued in conjunction with the commissioning of the new Generator Turbine Control system and AVR. During this phase of the commissioning there were another two protection element operations, these being Overvoltage and Loss of Excitation.

Both operations were proved to be genuine faults brought about by issues with the new Generator Turbine Control system and AVR. The online protection commissioning was completed on the 24th August 2018.

Zero Harm

All works were conducted without safety or environmental incident. The client was very happy with the excellent performance of the GTS crew on site.