and Haywards Switching the number 5 Cook Strait cable from Pole 2 back to the Pole 1/3. New 220 kV filters on the 220 kV buses at both Benmore and Haywards New transformers connecting the four synchronous condensers C7 to C10 to the 110 kV bus at Haywards New 5th and 7th harmonic filters connecting to the 110 kV bus at Haywards. Removal of the existing converter transformers connecting the Pole 1 mercury arc valves and two of the synchronous condensers to the 110 kV bus at Haywards. Removal of all remaining mercury arc valve Pole 1 equipment at both Benmore and Haywards. The decommissioning of Pole 1 was scheduled for July 2012, allowing works to switch the existing lines over Pole 3 to occur, and to allow testing of the new pole to occur during the summer months where electricity demand and therefore inter-island electricity transfer is low. The new Pole 3 was able to operate at 700 MW from commissioning, but due to inadequate voltage support at the Haywards end of the link, Pole 2 and 3 combined transfer was limited to 1000 MW. After the commissioning of a new static synchronous compensator (STATCOM) at Haywards in January 2014, Pole 3 was able to operate at its full capacity with Pole 2 in operation (1200 MW total transfer). Pole 2 control system replacement Pole 2 was commissioned in 1992 with HVDC control systems using late 1980s technology. After 20 years in service, the control systems are nearing the end of their useful life, are technologically obsolete, and are incompatible with the new Pole 3 control systems, making bipole control impossible. In late 2013, Transpower took Pole 2 out of service for four weeks to allow the control systems to be replaced with new systems identical to those used in Pole 3, and to install a new bipole control system to control both poles. This was followed by three months of testing the new control systems. Pole 3 continued to operate during the outage and most of the testing in a monopolar configuration with the earth electrodes. Other associated works Line maintenance During the time that Pole 1 was removed from service for replacement with Pole 3, maintenance and remedial work was undertaken on some sections of the transmission line. Work included: Replacing around 100 transmission towers in the South Island to fix clearance issues Replacing some conductor lengths