Grounding Measurement

Grounding Measurement Periodic Inspection is mandated under Article 10(a) of the Regulation on Grounding in Electrical Installations, which states that every grounding system must be inspected during installation and periodically throughout its operation. These inspections include:

• Visual examination
• Measurement and verification of continuity of protective conductors, main and supplementary equipotential bonding conductors
• Measurement of soil resistivity
• Measurement of grounding (dispersal) resistance
• Verification of automatic disconnection of supply
• Loop impedance testing
• Testing of Residual Current Devices (RCDs)

It is recommended to use the forms provided in Annex-P of the Regulation during inspections. The same annex specifies inspection intervals.

Inspection Periods for Various Grounding Systems

• Electrical generation, transmission, and distribution facilities (excluding overhead lines): Every 2 years
• Transmission and distribution overhead lines: Every 5 years
• Industrial facilities and commercial centers: Every 1 year
• Measurement of grounding resistance: Every 1 year
• Other grounding-related inspections: Every 2 years

For Non-Permanent Installations

• Fixed equipment: Every 1 year
• Mobile or portable equipment: Every 6 months

Purpose of Grounding System Inspection

1. To verify the structural integrity of the grounding system
2. To ensure that touch voltage remains within allowable safety limits

The structural integrity of the system can be assessed by measuring the grounding (earth) resistance. However, determining whether the grounding system is safe in terms of touch voltage cannot be based solely on grounding resistance values.

Different types of grounding electrodes and grounding arrangements may have the same resistance values yet behave differently regarding touch voltage or step voltage.

When current flows through grounding electrodes, the potential distribution within the soil determines the resulting touch voltage.