Helping Bendigo Trams beat nuisance tripping

Bendigo Tramways in Victoria is Australia’s oldest operating tram depot and one of the oldest urban tram networks in continuous operation in the world. The trust running the operation owns 45 trams, of which 15 are in the operational fleet.  The system welcomes more than 40,000 visitors a year – but with that popularity came a drawback.  Increasing demand for tram services had seen more trams on the line at once, drawing more power, and this culminated one day in a system overload that brought all the trams to a halt.

Keen to avoid a repeat of this nuisance tripping, electrical engineer Norm Grady, a 45-year veteran of the rail industry, (pictured) approached Middleton Group to review the existing protection settings and propose new settings under which the network could safely and reliably operate.

The Middleton Group team, Eric Bendtsen (Project Lead and Lead Engineer), Dr Stephen Goh (Technical Director) and Andrew Russack (Job Director), needed to model the network, which posed a challenge as the network impedance was unknown.

Carefully planned on-site testing helped solve this problem. The team then used MATLAB Simulink software for network simulations to identify maximum and minimum fault levels and the rate of change of the fault current.

The team also carried out network simulations to identify maximum current draw and rate of change of the current under reasonable worst-case operating scenarios. The DC protection settings the team then recommended balanced the risk of nuisance tripping while protecting the network against faults.

With the recommendations implemented, the tramways are now running safely to maximum capacity and there has been no more nuisance tripping. Bendigo Tramways engineer Norm Grady is delighted with the outcome, and says he valued Middleton Group’s technical accuracy.

• This work was carried out at no cost to the trust under Middleton Group’s community engagement programme.  Every year, the company provides 1000 hours of pro-bono work for community-based projects.