The Application of Electrical Vehicle Supply Equipment (EVSE) - Impact on the Electrical Power Infrastructure for Parking Stations

Plug-in electric vehicles (PEVs) are now available for the driving public. General Motors has released the Chevrolet Volt and Nissan has released the Nissan Leaf. These vehicles are manufactured in USA and Japan. Over time, the penetrations of PEVs into the market is forecast to increase.

PEVs have two classes of charging methods. These methods have been defined by SAE J1772-2010.

The first charge method is AC Level 1, which has a rating of 120 Vac, single phase at the maximum current of 12 A.  The second charge method is AC Level 2, which has a rating of 208-240 Vac, single phase at a maximum current of 80 A.

The charging method which is likely to be applicable in Australia is the second charge method. A typical charging station is the GE DuraStation. 

http://www.geindustrial.com/cwc/Dispatcher?REQUEST=PRODUCTS&pnlid=8&famid=9404&catid=6062&id=Elec-evcs

This station provides fast level 2 charging in 4-8 hours for a full cycle charge. The most commonly available models have a maximum continuous current rating of 30 A. This represents a continuous load of 7.2 kVA at 240 Vac. 

This means that the station will need to be supplied by a dedicated circuit, protected by a 40 A circuit breaker. In the USA, the NEC does recognise that any diversity should be included in determining the maximum demand. 

The impact of the addition of EVSE to parking stations is that a relatively significant load will have to be serviced in areas that are traditionally have very minimal loads. 
For instance, a multilevel car park in the city will have a typical load of lighting and perhaps a lift.  If 300 charging stations were to be installed, the total installed capacity would be 2,160 kVA. It is likely to require a complete overhaul of the LV electrical installation. 

The installation of EVSE may also impact the electrical load for houses and car parks such as:

• Shopping Centres
• Park and ride for train stations and bus stations 
• Apartments 
• Office and commercial buildings

There will also be an impact on the distribution network, which will have to support the additional load.  The additional load at the  point of connection may require the distribution company to upgrade the consumer mains and install additional transformers. 

Furthermore, there will be an impact of the load profile.  For example, the cars used to commuting will be charge overnight and during the day.

Reference
http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=6507645&sortType%3Dasc_p_Sequence%26filter%3DAND%28p_IS_Number%3A6523193%29

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