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PIS-CS-020/Earthing & bonding

Duplicate neutral-to-earth bonding

Two neutral-earth bonds turned one system into several unintended return paths.

Water facilityEnergy3 min read
An unintended N–PE link at a downstream boardEngineered approach for PIS-CS-020. Retain the intentional source bond for the actual system. Remove duplicate N–PE links and preserve PE continuity. Verify current paths, protection and accessible potentials. Conceptual teaching detail, not an as-built drawing or construction instruction. © PIS Engineering Academy · All rights reserved.PIS ENGINEERING / CASE 020An unintended N–PE link at a downstream boardENGINEERED APPROACHDISTRIBUTIONLNPEN AND PE REMAIN SEPARATESOURCE BOND / DOWNSTREAM N–PE INTERFACEActual source arrangement and protection govern the intended bond.1231Retain the intentional sourcebond for the actual system.2Remove duplicate N–PE linksand preserve PE continuity.3Verify current paths,protection and accessiblepotentials.READ THE DETAILEquipment, joints and current-path interfaces are shown in context.Conceptual teaching plate · no project dimensions or acceptance limits impliedPIS / REV 03© PIS Engineering Academy · All rights reserved

Engineering concept / vector field note

01

The field problem

Distribution Transformer near Water Facility

Protection malfunction, high step-voltage concerns and abnormal current/harmonic symptoms were reported.

why the obvious answer can be misleading

Investigation found duplicate transformer neutral/earthing connections. These can create parallel return paths and circulating neutral/zero-sequence currents and can distort protection behaviour.

02

Why it failed

Investigation found duplicate transformer neutral/earthing connections.

These can create parallel return paths and circulating neutral/zero-sequence currents and can distort protection behaviour.

03

Follow the engineering

Switch between the field condition and the engineering concept. Trace the path and examine what changes.

Inspect the engineering detail

An unintended N–PE link at a downstream boardEngineered approach for PIS-CS-020. Retain the intentional source bond for the actual system. Remove duplicate N–PE links and preserve PE continuity. Verify current paths, protection and accessible potentials. Conceptual teaching detail, not an as-built drawing or construction instruction. © PIS Engineering Academy · All rights reserved.PIS ENGINEERING / CASE 020An unintended N–PE link at a downstream boardENGINEERED APPROACHDISTRIBUTIONLNPEN AND PE REMAIN SEPARATESOURCE BOND / DOWNSTREAM N–PE INTERFACEActual source arrangement and protection govern the intended bond.1231Retain the intentional sourcebond for the actual system.2Remove duplicate N–PE linksand preserve PE continuity.3Verify current paths,protection and accessiblepotentials.READ THE DETAILEquipment, joints and current-path interfaces are shown in context.Conceptual teaching plate · no project dimensions or acceptance limits impliedPIS / REV 03© PIS Engineering Academy · All rights reserved

Case 020 · Engineered approach

100%
An unintended N–PE link at a downstream boardEngineered approach for PIS-CS-020. Retain the intentional source bond for the actual system. Remove duplicate N–PE links and preserve PE continuity. Verify current paths, protection and accessible potentials. Conceptual teaching detail, not an as-built drawing or construction instruction. © PIS Engineering Academy · All rights reserved.PIS ENGINEERING / CASE 020An unintended N–PE link at a downstream boardENGINEERED APPROACHDISTRIBUTIONLNPEN AND PE REMAIN SEPARATESOURCE BOND / DOWNSTREAM N–PE INTERFACEActual source arrangement and protection govern the intended bond.1231Retain the intentional sourcebond for the actual system.2Remove duplicate N–PE linksand preserve PE continuity.3Verify current paths,protection and accessiblepotentials.READ THE DETAILEquipment, joints and current-path interfaces are shown in context.Conceptual teaching plate · no project dimensions or acceptance limits impliedPIS / REV 03© PIS Engineering Academy · All rights reserved

Scroll to inspect. Numbered details match the notes below the drawing. Conceptual geometry; use the case text for the engineering requirements.

What changes

Remove unintended duplicate bonding, define the single intentional neutral-earth point according to the system design, then re-check protection and earth-potential behaviour.

Teaching schematic · not to scale© PIS Engineering Academy · All rights reserved
04

Correction & verification

Remove unintended duplicate bonding, define the single intentional neutral-earth point according to the system design, then re-check protection and earth-potential behaviour.

Verification recorded in the case

  • Measure currents and protection operation after correction; do not infer harmonic causation without power-quality 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 60364 system-earthing principles; project protection study.

PIS reviewed field handbook · PIS-CS-020

View the original social card
05

The engineering lesson

Before changing protection settings, prove that the current is returning through the intended path.

Take the lesson into your next design review.

Keep exploring

Connected lessons.

All cases
One transformer, unintended neutral-earth linksEngineered approach for PIS-CS-015. Define the intentional source bond for the actual earthing arrangement. Remove unintended duplicate links while retaining protective bonding. Verify neutral/PE current and protective-device operation. Conceptual teaching detail, not an as-built drawing or construction instruction. © PIS Engineering Academy · All rights reserved.PIS ENGINEERING / CASE 015One transformer, unintended neutral-earth linksENGINEERED APPROACHREMOTE BOARDLNPEN AND PE REMAIN SEPARATEONE SOURCE / CONTROLLED NEUTRAL REFERENCEActual source arrangement and protection govern the intended bond.1231Define the intentional sourcebond for the actual earthingarrangement.2Remove unintended duplicatelinks while retainingprotective bonding.3Verify neutral/PE current andprotective-device operation.READ THE DETAILEquipment, joints and current-path interfaces are shown in context.Conceptual teaching plate · no project dimensions or acceptance limits impliedPIS / REV 03© PIS Engineering Academy · All rights reserved
15

Earthing & bonding

One transformer. Too many return paths.

One transformer. More than one neutral-earth point. Too many current paths.

Sharqia3 min
System characteristics determine applicable provisionsEngineered approach for PIS-CS-033. Establish the actual 22 kV system, hazards and governing requirements. Select provisions applicable to this station and operating conditions. Document the step/touch methodology and engineering judgement. Conceptual teaching detail, not an as-built drawing or construction instruction. © PIS Engineering Academy · All rights reserved.PIS ENGINEERING / CASE 033System characteristics determine applicable provisionsENGINEERED APPROACH22 kV STATIONAPPLICABILITYSYSTEM / VOLTAGEHAZARDS / DUTYGOVERNING SCOPESTEP / TOUCH REVIEWThe reviewed case concerns a 22 kV station; criteria need an applicabilityreview.1231Establish the actual 22 kVsystem, hazards and governingrequirements.2Select provisions applicableto this station and operatingconditions.3Document the step/touchmethodology and engineeringjudgement.READ THE DETAILEquipment, joints and current-path interfaces are shown in context.Conceptual teaching plate · no project dimensions or acceptance limits impliedPIS / REV 03© PIS Engineering Academy · All rights reserved
33

Earthing & bonding

Applying the standard to the actual system

Using the Correct Standard Incorrectly Can Be as Problematic as Using the Wrong Standard.

MV renewable substation3 min
Independent drawings, interconnected real equipmentEngineered approach for PIS-CS-008. Create an intentional equipotential architecture. Size and coordinate the common bonding path for its actual duty. Verify continuity, potential differences and functional requirements. Conceptual teaching detail, not an as-built drawing or construction instruction. © PIS Engineering Academy · All rights reserved.PIS ENGINEERING / CASE 008Independent drawings, interconnected real equipmentENGINEERED APPROACHPOWERLIGHTNINGICTINTENTIONAL EQUIPOTENTIAL ARCHITECTUREVerify the coordinated network and its functional requirements.1231Create an intentionalequipotential architecture.2Size and coordinate thecommon bonding path for itsactual duty.3Verify continuity, potentialdifferences and functionalrequirements.READ THE DETAILEquipment, joints and current-path interfaces are shown in context.Conceptual teaching plate · no project dimensions or acceptance limits impliedPIS / REV 03© PIS Engineering Academy · All rights reserved
08

Earthing & bonding

Separate earths. Different potentials.

Separate earths created separate potentials.

New Administrative Capital3 min
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