In a feature for Professional Electrician published on 8 October 2026, Bob Preston explains the risks of diverted neutral current (DNC) and introduces Tradefox’s new DNC test simulator. Bob is a MEICA engineer with 28 years in the electrical industry who helped develop the City & Guilds 2366 Diploma, and he now works with Tradefox.
Why DNC matters
When a neutral breaks on a PME network, an installation’s earthing can become a return path for current from neighbouring properties, and bonded metalwork can carry that current. Bob makes the point that a low voltage reading is not proof of low risk, and that voltage pens and non-contact testers cannot detect diverted current, so current needs measuring too.
The new simulator
The original Safe Isolation Simulator assumed that switching off at the main switch removed the danger. The new simulator models PME network failures, taking learners through proving a socket live, proving a voltage indicator, and clamp-testing the main earthing conductor for current. Tradefox is also running an electrical safety campaign on the dangers of PEN faults: PENfault.
Read the full feature on Professional Electrician.
