Executive summary
Electric multiple unit passenger Train 6294 was stationary but attempting to depart from Mana station when an electrical fault on one of the traction motors caused a short circuit and fire in the train’s main electrical equipment case. High current being drawn by the short circuit caused the overhead traction lines to part and fall onto the train.
The train was travelling between Paremata and Mana stations on the North Island Main Trunk, en route from Wellington to Paraparaumu, when the driver experienced problems with the traction motors. The train was a 2-car train set with one motor car and one trailer car and was being driven in the reverse direction from the trailer cab. After passenger exchange at Mana, the driver attempted to depart the platform but the train did not move. Each attempt to move the train resulted in an immediate traction motor overload. The driver was leaving the train to walk along the platform to the rear motor car when there was a brilliant flash above his head. The overhead traction lines parted and the loose ends dropped onto the train and the platform. The electrical equipment cabinet, just below the level of the platform on the motor car, was on fire.
Train 6294 was evacuated and the public were cleared from the area while the potentially live overhead lines were isolated and made safe. There were no injuries and the fire was extinguished before the Fire Service arrived at the scene.
The fault in the traction motor had been developing throughout the previous week, yet weaknesses in the fault-reporting system meant the developing fault went unnoticed, and frequent re-setting of the circuit breaker eventually resulted in it, together with the then-unprotected electrical line contactors, failing.
With no electrical protection between the fault in the traction motor and the power supply, a very high electrical current passed between the overhead traction line and the train’s pantograph, causing the line to melt and part.
(Note this executive summary condenses content to highlight key points to readers and does so in simpler language and with less technical precision than the remainder of the report for the benefit of a non-expert reader. Expert readers should refer to and rely on the body of the full report.)
Related Recommendations
The current performance standard for train event recorders (or data loggers) as described in the National Rail System Standard NRSS/6 needs to be updated to include safety-critical equipment on electric traction trains and technical standards for how such information is recorded.
The automatic train status information presented to drivers in the driving cabs of Tranz Metro trains did not give the drivers adequate information about the status of critical on-board systems.
The system for recording faults on Tranz Metro trains was not user-friendly, was not being followed all of the time and did not achieve its purpose of reporting faults and informing drivers.
The Tranz Metro maintenance policy was biased towards being reactive rather than proactive and did not include identifying and monitoring the performance of safety-critical components such as high-speed circuit breakers.