Earthing design for EHV / HV substations including LV and ELV systems

Earthing design

 

Effective earthing is necessary for safety and functionality of every electrical and electronic system. Earthing designs of LPCI include global earthing system for industrial and commercial premises, where EHV / HV / LV and ELV systems are in close proximity. LPCI earthing design comply IEC 61936, EN 50522 and IEEE80 requirements.

Global Earthing System (GES)


GES is an earthing system created by interconnecting local earthing systems to minimise dangerous touch voltages. GES permits the division of the earth fault current in a way that reduces the earth potential rise at the local earthing system. Such system could be said to form a quasi-equipotential surface. Exposed and extraneous conductive parts are bonded together with a sufficiently dense interconnection (following the rules of main and supplementary bonding) that the rise in potential “together” ensuring NIL/MINIMUM potential difference between each item under fault conditions. No true earth reference exists and therefore safety voltages are limited.

Typical applications of GES are

  • Substation surrounded by buildings with foundation earth electrode and earthing system interconnected by low voltage protective earth conductors;

  • Substation feeding densely built up areas;

  • Substation feeding suburban area with many distributed earth electrodes interconnected by low voltage protective earth conductors;

  • Substation with given number of nearby substations;

  • Substations connected via cables with earth electrode effect;

  • Substation feeding extended industrial area;

  • Substations that are part of system with multi earthed high voltage neural conductors.

 

For installations where high-voltage equipment is not located in closed electrical operating areas, e.g. in an industrial environment, GES prevent touch voltages resulting from HV faults in a LV system.

The subject is now in Indian market due to the following facts

  1. Verification system consisting of inspection and testing as per IEC 60364-6 do not exist in India;

  2. Fault loop impedances and touch voltages are rarely calculated in design;

  3. Recommended measures in IEC standards are rarely followed due to reasons including misinterpretation;

  4. Recommended tests could not pass due to several reasons including measures against EMI.


In order to fulfil the complete requirements of GES, the service provided by CAPE include

 

  1. Design support for the fulfilment of technical requirements as per the standard;

  2. Training for all engineers involved including management, operations, maintenance etc;

  3. Verification of basic electrical drawings;

  4. Support during erection;

  5. Complete testing and commissioning;

  6. Long term contract for periodical verification;

  7. Record maintenance for future reference