31.07.15
Nexus criticised for ‘ineffective’ power supply risk management
The Rail Accident Investigation Branch (RAIB) has criticised Nexus and DB Regio Tyne & Wear (DBTW) for “ineffectively” managing risks associated with its power supply components, after a live overhead wire parted at Walkergate station last year.
On Monday 11 August 2014, a fault on a Metro train caused a live wire to part, and loose ends of it to flail around the train roof, showering sparks, with one end falling on to the station’s platform.
The train had developed an electrical fault in equipment under the rear car, which tripped the power supply to the overhead wire. About a minute later, the power was remotely restored by a power controller and a fire started in the faulty equipment. The fault drew a high current from the overhead wire through the car’s pantograph and overheated and, after about 18 seconds, the wire parted.
A second power controller happened to see what was happening on station CCTV and the power to the overhead line was disconnected. The parted overhead wire had remained live for about 14 seconds.
Fortunately, at the time of the accident, the train doors were closed for departure and there were no passengers on the platform. There were no reported injuries.
RAIB stated that a sustained high current was drawn because the electrical fault occurred in a part of the train’s power circuit that was not protected by on-train equipment and that could only be detected by the overhead power supply protection equipment. However, because of the way that the power was switched back on, the level of current drawn by the fault was not sufficient to immediately activate that protection.
Following its investigation, RAIB has recommended that Nexus seeks improvements in its safety management system to provide a more effective framework for the management of its shared risks.
Secondly, Nexus together with DBTW should identify and assess jointly created risks that occur at all interfaces between the infrastructure, power operations and trains. This should include the use of suitable risk assessment methodologies appropriate for identifying potential failure modes and their consequences, and a recognised technique for assessing the extent to which additional mitigations are required to reduce the risk as low as reasonably practicable.
RAIB added that Nexus and DBTW should together complete the on-going review of procedures and practices followed by power controllers, with a view to providing a codified set of procedures that have been appropriately risk assessed.
Raymond Johnstone, director of Rail and Infrastructure at Nexus, which owns and manages Metro, told RTM: “This was a serious and highly unusual incident which we have responded to quickly with accident investigators and our train operator DB Regio. I’m sorry for any distress caused to people who were on the train at the time.
“We have learnt from what happened and accept the key findings and recommendations from the accident report. We are investing almost £1m now to design and install digital multi-functional relays within all our Metro sub-stations. This will provide an extra level of protection to power supplies of a type found in new rail systems being built today.
“Nexus and DB Regio work very closely to manage safety issues and invest in improvements and our passengers should be assured that Metro continues to be a safe way to travel.”
UPDATE
Sharon Kelly, managing director for DB Regio Tyne and Wear, stated that safety of its customers and employees is “our top priority” and “I’m very sorry for those people on board the train who suffered any distress”.
She reiterated that this was an “exceptional incident” which “we have all learnt from”.
Kelly added that DB Regio Tyne and Wear accept the report’s findings and key recommendations and have put in place additional measures to manage risk and build resilience in our operating procedures.
“Working closely with Nexus we will continue to deliver a safe journey for all our customers,” she said.