Switchgear Parts FAT/SAT Acceptance Checklist

A switchgear parts FAT/SAT acceptance checklist is a structured, sequential verification document used to confirm that individual switchgear components – including contact boxes, bushings, insulators, and interlocks – meet defined electrical, mechanical, and dimensional tolerances before energization. FAT (Factory Acceptance Test) is performed at the manufacturer’s facility against the purchase specification and applicable standards such as IEC 62271 or IEEE C37. SAT (Site Acceptance Test) is performed after delivery and installation to confirm that transport, handling, and field assembly have not introduced faults or deviations.

This guide focuses on troubleshooting failed results, diagnosing root causes, and completing acceptance records that will hold up under audit or incident review.

Quick Diagnosis Table

Before opening a component or escalating an NCR, run through the table below. It maps the most common failure symptoms to a first test, probable root cause, and next action.

Tools and Acceptance-Source Reference Table

Test results are only as defensible as the instruments and standards behind them. The table below identifies each required tool, its measurement function, and the authority source used to set acceptance criteria.

Contact Box Acceptance Inspection: FAT and SAT Procedure

The contact box is the load-bearing heart of any switchgear assembly. Failures here – burned contact fingers, loose spring clusters, misaligned entry guides – produce resistive heating that cascades into insulation breakdown and eventual busbar faults.

Pre-Inspection Conditions

Contact Spring Force Acceptance Limits

Contact Resistance Measurement

Thermal Imaging at SAT

FAT vs. SAT Decision Matrix for Contact Box

Bushing and Insulator Acceptance Tests: Criteria and Standards

Bushings and insulators are dielectric components under continuous mechanical and electrical stress. Failures in this group are typically silent until flashover or tracking causes a forced outage.

Insulation Resistance and Polarization Index

Power Factor / Tan Delta Limits

Hi-Pot Withstand Voltage Reference

Partial Discharge Limits

Corrective Action Decision Logic for Bushings and Insulators

• Low IR only (PI acceptable): Clean and dry external surface; retest after 2 h. If IR recovers, the failure mode was surface contamination; document and accept conditionally in a controlled environment.
• Low IR with low PI: Internal moisture or aging; no field remedy. Replace and raise an NCR.

Interlock System Verification: Mechanical and Electrical Acceptance Testing

Interlock failures are disproportionately responsible for maintenance incidents because the fault often stays latent – appearing functional under routine observation but failing precisely when a protection sequence is triggered under load or fault conditions.

Interlock Test Matrix

Interlock Failure-Mode Checklist

Mechanical interlock does not block unauthorized operation: Measure blocking pin engagement depth against the type-test drawing; replace worn blocking element and verify the part number against the cubicle serial drawing before installation.
Interlock blocks authorized operation (false inhibit): Check actuator arm travel against nominal and verify the position switch trip point with a feeler gauge or dial indicator; realign, clean, and re-lubricate before retesting the full sequence.

FAT vs. SAT Decision Criteria for Interlocks

Field Service Scenario: Contact Resistance Failure During SAT

Background: During SAT on a 24 kV draw-out switchgear panel at a new industrial substation, the commissioning team measured contact resistance on the three-phase plug-in contact assemblies of one circuit breaker. Ambient temperature was 28 deg C and relative humidity was 62%.
Measured evidence:

Diagnosis: The disproportionate delta on L2 only, with no temperature-correction factor large enough to explain a 71 micro-ohm shift at 28 deg C, pointed to a localized condition. Visual inspection under 10x magnification revealed a thin layer of metallic powder on the fixed contact pin of the L2 tulip cluster, consistent with corrosion product from a corroded transit bracket stored adjacent to the contact pin in the shipping crate. The contact surface showed no pitting or arc erosion.

Acceptance Checklist Template, NCR Disposition, and Documentation

Core Column Structure

Every row in the checklist should represent one discrete test or inspection activity.

NCR Disposition Classifications

Use as Is (UAI): Applicable only when the deviation is quantified, an engineering analysis confirms it does not affect safety or rated performance, and the owner’s engineer provides written concurrence.
Rework: Applicable when the failure mode is surface-level, the corrective action is defined and reversible, and the reworked parameter can be fully retested. The original failed record is retained and cross-referenced to the new test record.

Mandatory Hold Points

Documentation Retention

Specifying and Sourcing Verified Switchgear Components Before You Order

Procurement failures that surface during FAT or SAT – wrong creepage distance, mismatched contact rating, undocumented insulator material – cost more to fix in the field than they would have cost to specify correctly at the order stage.

Supplier Capability Criteria

Pre-Order Hold Points

Creepage or BIL mismatch: If the supplier datasheet creepage distance or BIL rating does not match the site specification, request a revised datasheet with correct values or order from a different supplier. Do not accept verbal assurance.
Missing or unverifiable test certificates: If per-unit test data cannot be traced to the specific serial numbers being shipped, arrange third-party inspection at the factory or reject and reorder.

Related XBRELE Engineering References

Use these XBRELE references to connect the field decision to the correct product, test, and procurement workflow: XBRELE product page, XBRELE vacuum circuit breaker range, VCB ratings guide, VCB FAT/SAT acceptance checklist, XBRELE switchgear parts range.

Standards Context

For external method context, compare the site procedure with the public IEEE C37.09 standards page and then apply the exact OEM manual and project specification for the supplied equipment.

Field Example

Field example: during a service inspection, one phase measured outside its commissioning baseline while the other two phases remained stable. The team repeated the measurement with verified leads, checked timing and contact travel, and used the measured divergence to separate a contact-pressure problem from a generic surface-cleaning issue.

Frequently Asked Questions

What is the difference between FAT and SAT for switchgear parts?

FAT (Factory Acceptance Test) is performed at the manufacturer’s facility and verifies that the component meets the purchase specification, applicable standards, and type-test compliance under controlled conditions. SAT (Site Acceptance Test) is performed after delivery and installation to confirm that transport, handling, and field assembly have not introduced faults.

What contact resistance values should trigger rejection during SAT?

For plug-in contacts rated up to 1600 A, the SAT pass limit is <= 75 micro-ohm. For draw-out contacts rated 1600 A–4000 A, the SAT pass limit is <= 45 micro-ohm.

Can a bushing or insulator that fails an IR test be cleaned and re-accepted?

Yes, under specific conditions. A bushing that fails IR on first test but passes after surface cleaning and a 24 h drying period has a contamination failure mode, not a materials failure; document the cleaning procedure, re-run the full IR and withstand sequence, and record both results.

What does a rising tan delta tip-up indicate and why does it cause rejection?

How many times should an interlock sequence be exercised during acceptance testing?

What is a Polarization Index (PI) and what values are acceptable?

What records must be retained after a failed test is corrected and retested?