The 2006 Auckland Blackout was a major electrical blackout in Auckland, the largest city in New Zealand, on 12 June 2006. It started at 08:30 local time, with most areas of Auckland regaining power by 14:45 local time. It affected some 230,000 customers and at least 700,000 people in and around the city. Immediate effect Power went off at around 8:30 am local time on 12 June 2006 over half of Auckland in New Zealand. Most of southern and central Auckland, including the central city were without power. Cause The cause of the blackout was traced back to the Otahuhu sub-station, the city's main transmission switching station. A corroded shackle connecting the Otahuhu to Penrose 220 kV line's earth wire had broken in winds, letting the earth wire fall across the 220 kV line and the 110 kV busbar below it, tripping both the line and three sections of the busbar, disconnecting lines to Mount Roskill, Penrose and Pakuranga. The trip also disconnected Otahuhu B and Southdown power stations from the national grid. The trip left only one line, the now-dismantled Arapuni to Pakuranga 110 kV line, supplying Pakuranga, Penrose, and the central city. Eight seconds after the failure, this line tripped from overloading, leaving Penrose, Pakuranga, and central city substations without power, as well as parts of Otahuhu and Mount Roskill substations. Investigation of this incident found that maintenance of the electricity transmission system was not adequate and that this substation had major and minor design deficiencies. Effects Due to the power outage, many public services and business operations were disrupted: suburban commuter railway services were suspended over 300 groups of traffic lights were off some hospitals were closed and left only emergency services in operations radio station transmitters located in the Sky Tower were also taken offline for a period of time mobile phone and telephone service failures people stuck in lifts in office buildings end of semester exams due to be held that day at local universities were postponed. Since the central city was without power from the morning rush hours, business operations and traffic were disrupted severely. Many businesses sent their staff home. Restoration of service Power was restored to Auckland central at 12:40 local time, 12 June 2006. It was estimated that all affected areas would have their power restored by 16:30 local time. At approximately 14:45, power was restored to most of Auckland, except