Sydney Airport, also known as Kingsford Smith Airport, is located next to Botany Bay about 15km south of Sydney city centre and it is the major hub for Qantas and Virgin Blue airlines. Sydney Airport handled 31.9 million passengers and 290,346 aircraft movements in the year 2007 and it was the 28th busiest airport in the world in 2003.
Therefore with such a critical facility in operation, equipment reliability is one of the major requirements to its power supply network. There are three identical 19 MVA, 33/11 kV transformers (2 mains and 1 spare) in this network each equipped with a Reinhausen OILTAP® V powering the International Terminal and the main transformers always run in parallel. In addition, Sydney Airport also had three unnamed automatic voltage regulator units regulating the 11kV voltage that is being supplied by the transformers.
But recently the unnamed voltage regulator units, which supposed to regulate the voltage level as well as align the tap changers on the same tap position, started to mysteriously control the tap changers to drift away from one another in opposite tap directions. This so called “Out of Step” occurrence induced undesirable circulating currents within the network and generated overheating which would deteriorate the life expectancy of the transformers and might even potentially overload the equipment downstream. Moreover, the unnamed voltage regulator units were initiating unnecessary tap operations throughout the night which shortens the service interval of the corresponding tap changers.
With these issues at hand, Sydney Airport insist to tackle the problem as soon as possible and after a few meetings with them, Reinhausen Australia agreed to their requirements of setting up a design scheme for the TAPCON 240® voltage regulating system to enable Master or Follower selection with automatic detection of Parallel Groups for the three transformers in the network by means of a simple 3-position switch. The special safety function to disable all tap changer motor drive operations during a paralleling “Out of Step” fault was also to be implemented.
After the TAPCON 240® units are installed and operational, Sydney Airport immediately reports of far fewer tap changer operations and less voltage fluctuations in the network, which means it is a success story for both Reinhausen Australia and Sydney Airport.