SAGE Second Interim Assessment

cover of second SAGE reportSAGE is the UK's Stakeholder Advisory Group on ELF EMFs.  More on SAGE generally.  Its First Interim Assessment in 2007 covered possible precautionary measures for house wiring, appliances, and power lines and property.  The Government responded in 2009.  SAGE has now (2010) published its Second Interim Assessment, covering, principally, low-voltage distribution networks.

Download the Second Interim Assessment


 SAGE considers numerous different possible precautionary measures and for each one makes one of three types of recommendation:


  • existing best practice which should continue with a recognition that EMFs are an extra reason for doing them
  • new measures that should be introduced


  • further investigation needed before a recommendation is made
  • "consumer choice": not recommended generally but available if an interested party does not mind bearing the cost


  • because the option is not effective
  • because the cost would be disproportionate
  • because there would be adverse safety consequences

It groups the options by the different parts of the distribution system and we summarise the recommendations here.  See also a full list of recommendations.

Options relating to net currents in distribution circuits

more on what net currents are and how they arise in the UK

  • Exposures from distribution circuits arise from net currents.  In turn, net currents arise from either multiple earthing or from interconnected neutrals.  Both of these have safety benefits and SAGE decided it was not justified to remove them.  But SAGE does recommend measures, mainly existing best practice anyway, to reduce net currents: e.g. balancing loads across phases and using plastic gas and water pipes. 
  • One particular feature - broken neutral conductors - can produce high magnetic fields, and SAGE is keen that DNOs investigate and repair these. 
  • There are ways, in principle, of reducing net currents using inductors.  SAGE decided further investigation was needed of the practicality and, particularly, the safety of these on the UK system
  • Similarly, broken neutrals could be detected in principle by routine measurements, but SAGE decided further investigation was needed of the practicability of this.

Option relating to wiring in multi-occupancy buildings

SAGE endorsed existing best practice to site plant rooms away from occupied areas and to use low-field arrangements for risers, but decided that retrofitting these would have to be a matter of consumer choice and cost.

Options relating to intermediate-voltage circuits

Options relating to final distribution substations

more on substations and the fields they produce

  • On siting of substations, SAGE says reasonably practicable efforts should be made to site them away from homes etc, but further investigation is needed before introducing any limits on field or distance
  • On the design of substations, SAGE endorses the use of compact designs for new and refurbished substations, but says that retrofiting or screening existing substations is a matter of consumer choice and cost
  • For instances where substations do produce high exposures, SAGE recommends two new measures.  One is that Distribution companies should always be willing to investigate and offer the consumer options for reducing the field (at the consumer's cost).  The other is that DNOs should these instances so that EMF issues can be factored into future refurbishment decisions.

Options relating to training and response

SAGE recommends more information for the public, and that DNOs should always be willing to investigate EMF issues when reported to them, and should train their staff to recognise how EMF issues can sometimes be an indication of system problems.

What happened next?

In June 2011, the Government issued their response.  This led to an Engineering Recommendation published in March 2013 that implements the SAGE recommendations applying to low-voltage distribution networks.

Reducing your own exposure

If you decide for yourself that you want to reduce your exposure to EMFs, we provide a page with a discussion of the main options.