In a single phase power supply system, if I measure the earth to neutral voltage, can I use it to indicate the health or status of the earth resistance i.e. if E-N voltage is high, is it due to earth resistance being high?

Is my following understanding correct:

  1. In single phase electrical system, if earth resistance is high, earth to neutral voltage will be high.

  2. Corollary- High earth resistance is the ONLY reason for high earth to neutral voltage in single phase electrical system.

  • 1
    \$\begingroup\$ 1)Not necessarily. It might be high neutral resistance. Either way something is wrong and needs professional attention. 2) Not necessarily. Earth current may (and normally should) be low. High earth resistance may be undetected until another fault occurs. 3) See 1 and 2) \$\endgroup\$
    – user16324
    Commented Sep 27, 2020 at 11:02
  • \$\begingroup\$ Which earthing system you mean? Isn't earth bonded to neutral at least at some point? So neutral to earth voltage should be quite low, unless that bond is broken at some point or huge currents flow either on neutral or earth. \$\endgroup\$
    – Justme
    Commented Sep 27, 2020 at 11:04
  • \$\begingroup\$ @Justme earth bonded to neutral at generators / transformers plus at every house / load in low-voltage systems. \$\endgroup\$
    – schnedan
    Commented Sep 27, 2020 at 11:13
  • \$\begingroup\$ @schnedan you got to pick a mains earthing system like TT or TN-C-S or whatever based on regulations where you live and go by it. So the earthing system depends on which places it is allowed and forbidden to bond neutral and earth. \$\endgroup\$
    – Justme
    Commented Sep 27, 2020 at 11:41
  • \$\begingroup\$ really? as a electrical engineer that's totally new to me. \$\endgroup\$
    – schnedan
    Commented Sep 27, 2020 at 11:47

1 Answer 1


first check the earthing system in use.. if you have TN-S , TN-C or TN-C-S then you have a bad earth connection. On the other hand if you have an IT mains which happens when you have 2 phases in stead of phase and neutral... in the last case its normaal to measure high Earth - Neutral( or maybe other phase .. hope this helps


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