Generating simple-to-apply comprehensive engineering recommendation for earthing safety in systems with solidly earthed neutral

Generating simple-to-apply comprehensive engineering recommendation for earthing safety in systems with solidly earthed neutral

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This study presents the procedure of generating simple-to-apply engineering recommendation for earthing systems and boundaries for setting of earth faults relay protection in power systems with solidly earthed neutral. The simple rules are based on ‘the worst case analyses’. Motivation for this work was simplification of the engineering process with acceptable deviation from economic optimum. Another reason is addressing the specific problems occurring in studied arid desert terrains conditions, which are described in this study. The analyses are based on calculation of earth fault current, its distribution over multiple earthing systems along the power line connected via protective conductor, tripping time dependent on relay curve, and allowed step and touch voltages depending on tripping time and characteristics of soil and optional additional surface material. For these calculations, the Excel/VBA software tool is developed and used. Different topologies of earthing systems (with grounding contours, rods, with/without backfill materials, etc.) considering layout of equipment in substation are studied using finite-elements software in order to determine the ratio of touch and step voltages to ground potential rise – GPR. The methodology is explained through a prominent case study of overhead line with overhead ground wire and metallic poles in the rural area.


    1. 1)
      • 1. IEEE Std 80-2000: ‘IEEE guide for safety in AC substation earthing’, 2000.
    2. 2)
      • 2. EN 50522 Standard: ‘Earthing of power installations exceeding 1 kV a.c.’, 2010.
    3. 3)
      • 3. IEC Std 60909 – 0: ‘Short-circuit currents in three-phase a.c. systems – Part 0: Calculation of currents’, 2001.
    4. 4)
      • 4. IEC Std 60909 – 3: ‘Short-circuit currents in three-phase a.c. systems – Part 3: Currents during two separate simultaneous line-to-earth short circuits and partial short-circuit currents flowing through earth’, 2003.
    5. 5)
      • 5. Nahman, J.: ‘Earthing of neutral point in distribution networks’ (Naucna knjiga, 1980). (in Serbian).
    6. 6)
      • 6. Tleis, N.D.: ‘Power system modelling and fault analysis: theory and practice’ (Newnes, 2008).
    7. 7)
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    12. 12)
      • 12. IEC Std 60255 – 151 ed. 1.0: ‘Measuring relays and protection equipment – Part 151: functional requirements for over/under current protection’, 2009.
    13. 13)
    14. 14)

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