What happened

A fault was detected in the Basslink high-voltage DC submarine cable connecting Tasmania to Victoria on the afternoon of 20 December 2015, roughly 100 km off the Tasmanian coast in Bass Strait, at a depth of about 75 metres. Basslink chief executive Malcolm Eccles said the cause was unknown until a repair vessel could physically inspect the cable, and the company initially had 60 days under its licence to complete repairs, while cautioning this was not necessarily an estimate of the actual outage duration. Tasmania, which normally imported around 40% of its electricity via Basslink, became fully reliant on Hydro Tasmania's water storages, wind generation and the gas-fired Tamar Valley Power Station; a repair vessel was mobilised from New Zealand. The outage extended far beyond the initial 60-day estimate as hydro storage levels fell to record lows (reported around 27% when the cable was eventually restored) during an unusually dry period, prompting the Tasmanian government to bring in additional diesel generators and triggering a state parliamentary inquiry into the handling of the crisis. The cable's fibre-optic communications component was restored on 10 June 2016, and full power transmission resumed shortly before midday on 13 June 2016 — almost six months after the fault — initially at a reduced capacity of about 100 MW while a roughly 100-person repair and testing team completed further work. The specific technical cause of the cable fault was described as still under investigation in the reviewed reporting at the time of restoration, and the Tasmanian government later sought compensation from Basslink over the outage; that compensation dispute is a separate commercial matter and is not treated here as an admission of fault. This was an accidental submarine-cable/equipment failure, not an attack. The marker is placed at an approximate mid-point of the Basslink route in Bass Strait, not the exact fault location, which was not published in the sources reviewed.

When cited sources give different casualty, damage or spill figures for this event, they’re reported side by side above rather than merged into one number. See how confidence levels work.