Low Energy Automated Networks - LEAN

SSEN’s LEAN project successfully met its objective to develop and apply Transformer Auto Stop Start (TASS) technology to reduce losses at 33/11kV primary substations.

The key principal of TASS is to switch off one of a number of transformers in a primary substation at times of low demand to avoid the fixed iron losses associated with that transformer – akin to a car engine turning off when the vehicle isn’t travelling.

two primary transformers at one of the project trial sites

The TASS system provides local, automated control within the substation to monitor the loading and control this switching, and to respond to SCADA alarms and status information from other network assets. In addition, commands incorporated into the Distribution Management System (DMS) provide the central network Control Room with remote supervision and management capability. The technology has been deployed in primary substations on the SEPD network since June 2018, and over the formal twelve month trial period achieved energy savings of over 67 MWh in total across the two trial sites, with full operation reducing transformer losses by ~25-30%. No impacts on asset health due to TASS operation have been identified through the suite of testing and monitoring techniques applied.

The system continues to operate as designed, demonstrating the ability to both reduce losses and respond appropriately to different network situations, and the scheme design developed through the project provides a streamlined system for integration with existing assets to deliver the TASS functionality.


We have five key reports which detail the different aspects of developing, implementing and operating TASS technology:

  • 9.4 Initial Learning from Trial Installation & Integration – comprehensive information on the technology developed, its integration with existing network assets, and the operational principles designed into the scheme
  • 9.5 Monitoring & Analysis – an appraisal of the techniques used to monitor the trial sites, and analysis of the data acquired to evaluate any potential asset health or power quality implications associated with TASS, and verify that the system operates as designed
  • 9.6 Site Performance – a full review of the losses savings achieved through TASS, and evaluation of the benefits of the technology and costs of deployment to refine the business case
  • 9.7 Network Losses Evaluation Tool – the enhanced CBA tool created to assess the benefits of TASS, with a detailed description of the substation assessment process used to assess the financial viability and technical feasibility of applying the technology on a site by site basis
  • 9.8 Knowledge & Dissemination – the project closedown report, including a detailed review of the scalability & replicability of the system as a guide for wider deployment across other network areas

Accompanying those formal reports we’ve created a suite of material which is all available to DNOs, product manufacturers and other stakeholders, including:

– guidance for considering how to implement TASS on other networks

– information on the scheme that we’ve designed and its installation & testing

– a framework for assessing the technical and financial viability of applying TASS to individual substations

– training material for operational staff, and

– all of the information relating to asset health and power quality, together with other material that may be useful for other innovation projects

Project Deliverables – Transformer Auto Stop Start


If you would like any further information on any aspect of the project, please contact the team via .