The field problem
Benban Solar Plant — Aswan
The site had extremely high and vertically variable soil resistivity, non-achieving grounding values, return-current concerns and tracker-control failures.
Previous testing relied heavily on clamp-on measurements.
why the obvious answer can be misleading
Clamp-on earth testing depends on a closed return loop and cannot replace Fall-of-Potential testing for isolated/open electrodes. Short auxiliary spikes can also be inadequate when the near-surface layer is not representative of deeper geology. The measurement plan therefore had to match the topology and soil model.
Why it failed
Clamp-on earth testing depends on a closed return loop and cannot replace Fall-of-Potential testing for isolated/open electrodes.
Short auxiliary spikes can also be inadequate when the near-surface layer is not representative of deeper geology.
The measurement plan therefore had to match the topology and soil model.
Follow the engineering
Switch between the field condition and the engineering concept. Trace the path and examine what changes.
Inspect the engineering detail
What changes
Separate the problem into soil-resistivity characterization, isolated-electrode/grid resistance, on-grid loop checks, continuity, current-path investigation and control/EMC checks.
Correction & verification
Separate the problem into soil-resistivity characterization, isolated-electrode/grid resistance, on-grid loop checks, continuity, current-path investigation and control/EMC checks.
Use appropriate probe geometry and electrode lengths for the actual geology.
Verification recorded in the case
- Correlate corrected measurements with network modifications and tracker/control behaviour. Do not attribute all control failure to earthing without evidence.
- Record as-built topology and connection points.
- Repeat the measurement or functional test under a defined condition.
- Confirm continuity and mechanical integrity of the corrected path.
- Document instrument/setup, environmental condition and test method.
- Close the NCR/case only when evidence supports the conclusion.
References & project context
References are reproduced from the PIS casebook. Select the governing edition and project acceptance criteria before using them for a design. The diagrams explain the concept, rather than define construction dimensions.
IEC 61557-5; IEC 60364 earthing/bonding principles; project-specific renewable-energy grounding and EMC requirements.
PIS reviewed field handbook · PIS-CS-006
View the original social cardThe engineering lesson
Choose the test method from the electrical topology and geology — not from the instrument available in the technician’s bag.
Take the lesson into your next design review.