On Tuesday we experienced significantly high temperatures in the Wellington region which caused major issues to the infrastructure on the Wellington Rail Network.
Photo: RNZ / Kate Gudsell
There is permanent temperature monitoring equipment on the rails across the network. Precautionary speed restrictions are applied to any stretch of line when the rail temperature reaches 40 degrees, which causes delays to train services. If the temperature exceeds this then a visual inspection may also be required.
Due to the older overhead traction system on the Johnsonville and Hutt Valley lines visual inspections are needed to monitor any sag in the overhead.
The Hutt Valley Line was initially impacted due to a metal trackside box containing components of the signalling system overheating in the 30 degree plus temperatures. This caused the points and signal outage at Petone, which suspended train services on the Hutt and Melling lines. Following this the excessive heat then caused the overhead wiring to expand and sag meaning trains were unable to run along the line. We immediately contacted all bus operators in the Greater Wellington region to request buses, but were only able to source a small number and they took up to 45 minutes to reach a train station due to traffic and their location.
The Johnsonville Line experienced similar issues with the temperature of electrical equipment on the line rising to excessive temperatures causing outages. The overhead wiring also experienced the same issue as the Hutt Valley Line where it expanded in the heat resulting in the sagging of the overhead wires.
The expanding wires on the overhead power supply only impacted the Hutt Valley and Johnsonville lines and not the Kapiti line because they have the old type of fixed tensioning which has very little give in hot temperatures and to adjust the wires the power needs to be turned off resulting in no train services. Kapiti Line is Auto tensioned which uses a weight mechanism to automatically adjust the tension of the overhead wires accordingly thus not impacting services on that line . As part of the traction upgrade project auto tensioning is one of the upgrades happening on the Hutt Valley Line.
For more information about this project visit The Hutt Valley Traction Upgrade Project page.