Battery Energy Storage System (BESS) 33kV Substation & Contestable Connection & full EPC


JSM supplied and installed a DNO 2-panel 33kV substation and associated contestable works and associated cabling.




10 Months

Date Completed

March 2023

JSM was appointed Principal Contractor for the Design & Build of a Battery Storage Development inclusive of the design, procurement, site clearance, levelling, construction, of all civils and electrical works.

JSM supplied and installed a DNO 2-panel 33kV substation and associated contestable works and associated cabling.


Delivery and Approach 

The works required to position the client’s free issued equipment including 6no battery containers, 3no dual secondary wound 33/0.48kV transformers, client’s switch room complete with internal apparatus.

JSM completed the standard contestable design and the overall site design and engineering for all disciplines within the site compound inclusive of:

  • Detailed civil design for complete compound
  • Detailed electrical design and drawings including all calcs for the project inclusive of Cable calculations and route design, control / SCADA cable schedule
  • Flame Detection and CCTV design
  • Earthing study
  • Lightning Protection RA and subsequent design
  • Lighting Design
  • Protection & Co-ordination study
  • Short circuit study


Challenges and Solutions


The site is connected through Over Head Line (OHL) connection due to which the entire earth fault had to be considered for earthing design study. Also, the site was to be supplied with an 11kV connection in the future which had to be considered for calculation purposes alongside the difference of fault clearance’s times for both voltage levels.

With 100% ground return for both 33kV and 11kV faults and limited area of site, JSM’s solution was to provide  an earthing design that resulted in ‘safe’ and ‘Hot’ site. Along with proving safe potentials, various consideration based on ENA E.R S36 were followed to ensure safety on the  site  and  also  adjacent establishment.


Another challenge included lifting the batteries  into their final position on site.  Each battery weighted 32 tons. To ensure the ground was able to support  the 300t crane and list 32tons, JSM carried out  a temporary works design and implemented the required temporary reinforcement as specified in the  design.