EV charging depot: load study, smart charging and transformer sizing

Severn Parcel Logistics runs 60 diesel vans from its Avonmouth depot and has ordered electric replacements: 3.5-tonne vans with 75 kWh usable batteries. Vans come back between 18:30 and 20:30 and leave again between 06:00 and 07:30. Daily routes run from 90 to 160 km, and winter consumption with cab heating is about 0.30 kWh per km.

The depot has its own 11 kV/400 V 800 kVA transformer, but the agreed import capacity with the distribution network operator is 500 kVA. The warehouse already peaks at about 280 kVA in the morning and sits around 90 kVA overnight. The fleet manager's supplier has proposed 60 × 22 kW chargers plus 4 × 50 kW rapid chargers, and has warned that a capacity increase could cost upwards of £250,000 and take 18 months.

The operations director wants an engineer's answer to three questions: 1. If every van plugs in at 19:00 and charges flat out, what happens to site demand? 2. Can a smart-charging schedule get every van to the state of charge its next route needs, inside 500 kVA, with a 10% safety margin? 3. What LV electrical works are needed, and does the transformer cope?

You will generate a realistic half-hourly site baseline, simulate unmanaged and managed charging in Python, size the switchboard, feeders and protection, and compare options on cost. No hardware is needed; everything is calculation and simulation.

Done looks like a study the director can take to the DNO and the board: demand plots for each scenario, a charging schedule that meets every van's need, the electrical design, and a costed recommendation. If the honest answer is that rapid chargers break the limit at midday, say so.