is liable for fines up to $100,000 and forfeiture of their vessel – more if a cable is subsequently damaged. HVDC transmission line The transmission line was designed and built by the New Zealand Electricity Department, and was completed in January 1965. The original construction of the line included the erection of 1623 steel lattice towers. In some South Island sections, the line reaches an altitude of 1280 metres. The longest span is 1119 m, near Port Underwood, close to the Fighting Bay cable terminal station. The line was originally designed for operation at ±250 kV. During the DC Hybrid link project of 1989 to 1992, the transmission line was reinsulated with DC fog type porcelain insulator units, to enable operation at 350 kV. There are 15 units per insulator string in the inland parts of the route, and 33 units per insulator string in the coastal parts of the route that are exposed to salt condensation. The insulator strings in the coastal portions are around 5 m long. The transmission line insulators support a pair of ACSR conductors on each side of the towers. The conductors are each 39.4 mm in diameter, and are spaced 432 mm apart. The HVDC line has a continuous overhead earthwire for lightning protection, except for a 21 km section at the Haywards end, where the line is shielded by the electrode line conductors. A 13 km section of the North Island HVDC line uses an overhead earthwire containing a fibre optic core (OPGW), and a further 169 km section of OPGW is installed the South Island line. About 20 new towers were constructed in 1992 to reroute the HVDC line north of Johnsonville to make way for new residential development. This was known as the Churton Park deviation. Around 92.5 percent (1503) of the towers on the line in 2010 were identified as being original, with the remaining towers having been replaced due to line deviations, collapse, or corrosion. Following the DC Hybrid Link project, the line was rated to carry 2000 amperes continuously on each pole, at an operating voltage of 350 kV HVDC. Earth electrode stations The connection between the North Island converter station and earth uses a shore electrode station located at Te Hikowhenua, approximately 25 km from Haywards. Following upgrades carried out during the DC Hybrid Link project, the electrode station is capable of carrying 2400 A continuously. Forty