ARUP and MITSUI are leading a joint-venture to determine the technical and commercial feasibility of decarbonising an existing public transport route around Milton Keynes with the introduction of a number of pure electric buses. The conventional diesel powered buses currently servicing this route will be entirely replaced by an electric bus fleet developed by Wright Bus and will be operated by Arriva. This will be the first scheme in the UK to replace an existing fleet with electric multi-passenger vehicles.

A capacity of 120kVA is required to deliver sufficient charge to the bus within the short window of time it will be waiting at a bus-stop. A linear load of this size should be able to be supplied by the low voltage system in most cases without thermal ratings being exceeded, however the non-linear equipment used in the IPT system is likely to cause high levels of harmonic voltage distortion.

Engineering Recommendation G5/4 sets the planning levels for harmonic voltage distortion to be used in the process for the connection of non-linear equipment and LV equipment creating disturbance levels outside of this would need to be connected at HV, increasing the cost and acting as barrier to uptake.

Objectives

The project has defined the following objectives:

• Infrastructure will be installed to provide connection to three IPT chargers in the Milton Keynes area using a number of different arrangements

• HV and LV monitoring will be installed before and after IPT charger commissioning in order to determine the change in harmonic levels

• A smart wired charging system will be created to return the vehicles to a full state of charge overnight whilst ensuring the network is operating within its rated capacity.