{"id":3950,"date":"2026-07-01T09:00:00","date_gmt":"2026-07-01T09:00:00","guid":{"rendered":"https:\/\/xbrele.com\/?p=3950"},"modified":"2026-06-09T15:27:00","modified_gmt":"2026-06-09T15:27:00","slug":"switchgear-parts-fat-sat-acceptance-checklist","status":"publish","type":"post","link":"https:\/\/xbrele.com\/ta\/switchgear-parts-fat-sat-acceptance-checklist\/","title":{"rendered":"\u0b9a\u0bc1\u0bb5\u0bbf\u0b9f\u0bcd\u0b9a\u0bcd \u0b95\u0bbf\u0baf\u0bb0\u0bcd \u0baa\u0bbe\u0b95\u0b99\u0bcd\u0b95\u0bb3\u0bcd FAT\/SAT \u0b8f\u0bb1\u0bcd\u0baa\u0bc1 \u0b9a\u0bb0\u0bbf\u0baa\u0bbe\u0bb0\u0bcd\u0baa\u0bcd\u0baa\u0bc1\u0baa\u0bcd \u0baa\u0b9f\u0bcd\u0b9f\u0bbf\u0baf\u0bb2\u0bcd"},"content":{"rendered":"

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.<\/p>\n

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

\"Switchgear
Quick diagnosis flow for failed switchgear part acceptance results.<\/figcaption><\/figure>\n
\n

Quick Diagnosis Table<\/h2>\n

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.<\/p>\n\n\n\n\n\n\n\n\n\n\n\n\n\n
Symptom<\/th>\nFirst Test<\/th>\nLikely Root Cause<\/th>\nNext Action<\/th>\n<\/tr>\n<\/thead>\n
Contact resistance above FAT limit<\/td>\nRe-measure with clean probe tips; verify 100 A DC injection<\/td>\nOxidized or pitted contact surface; loose bolted joint<\/td>\nVisual inspection at 10x; clean, re-torque, retest<\/td>\n<\/tr>\n
Insulation resistance below 1000 Mohm in dry environment<\/td>\nRetest after 2 h surface drying; record humidity<\/td>\nInternal void, crack, or resin delamination<\/td>\nPD test or hi-pot; escalate to manufacturer if confirmed<\/td>\n<\/tr>\n
Insulation resistance below 1000 Mohm in humid environment<\/td>\nClean surface, dry 24 h at ambient, retest<\/td>\nSurface contamination or moisture absorption<\/td>\nRetest within 24 h before re-contamination<\/td>\n<\/tr>\n
Tan delta above alarm threshold<\/td>\nRepeat at 0.5 U0 and U0; check tip-up effect<\/td>\nInternal moisture ingress or voids in cast resin<\/td>\nPD measurement; reject if tip-up > 0.1%<\/td>\n<\/tr>\n
Mechanical interlock does not block unauthorized sequence<\/td>\nMeasure blocking pin engagement depth vs. drawing<\/td>\nWorn cam or pin below minimum engagement<\/td>\nReplace blocking element; retest 5 sequences<\/td>\n<\/tr>\n
Interlock blocks authorized operation (false inhibit)<\/td>\nCheck actuator arm travel; feeler-gauge switch trip point<\/td>\nMisaligned position switch; stiction from dry lubricant<\/td>\nRealign switch; lubricate; retest full sequence<\/td>\n<\/tr>\n
Thermal camera shows > 15 deg C phase differential at SAT<\/td>\nMeasure contact resistance on hot phase before next shift<\/td>\nHigh-resistance joint at contact box<\/td>\nDe-energize; inspect and clean contact; retest<\/td>\n<\/tr>\n
Anti-pumping relay fails – CB re-closes on sustained close<\/td>\nEnergize anti-pump coil manually; verify NC contact opens<\/td>\nWelded contact or coil failure<\/td>\nReplace relay; rewire check; retest per C37.09<\/td>\n<\/tr>\n
Hi-pot leakage current steps during 60 s withstand<\/td>\nDo not re-apply voltage; note step magnitude and time<\/td>\nDielectric breakdown initiation<\/td>\nReplace component unconditionally; raise NCR<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
\n

Tools and Acceptance-Source Reference Table<\/h2>\n

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.<\/p>\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n
Instrument \/ Source<\/th>\nFunction<\/th>\nAcceptance Authority<\/th>\n<\/tr>\n<\/thead>\n
Micro-ohmmeter (100 A DC rated)<\/td>\nContact resistance in micro-ohm<\/td>\nIEC 62271-200; OEM contact resistance datasheet<\/td>\n<\/tr>\n
5 kV or 10 kV megohmmeter<\/td>\nInsulation resistance (IR) and Polarization Index<\/td>\nIEC 60052; IEEE 43<\/td>\n<\/tr>\n
Capacitance and power factor test set<\/td>\nTan delta \/ dissipation factor<\/td>\nIEC 60137; IEEE C57.19.01<\/td>\n<\/tr>\n
AC or DC hi-pot test set (rated to voltage class)<\/td>\nPower-frequency withstand; leakage current monitoring<\/td>\nIEC 62271-1 Clause 7; IEC 60060-1; ANSI\/IEEE C37.09<\/td>\n<\/tr>\n
PD measuring system (IEC 60270 calibrated, in pC)<\/td>\nPartial discharge inception and level<\/td>\nIEC 60270; IEC 60137; IEC 62271-203<\/td>\n<\/tr>\n
Calibrated push-pull gauge<\/td>\nContact spring force; interlock blocking force<\/td>\nOEM type-test drawing; IEC 62271-200<\/td>\n<\/tr>\n
Thermal imaging camera<\/td>\nPhase-to-phase temperature differential at SAT<\/td>\nNFPA 70B (maintenance reference); IEC 60076-7 analogy<\/td>\n<\/tr>\n
Digital timer or oscilloscope<\/td>\nInterlock signal response time<\/td>\nScheme logic specification; IEC 62271-100<\/td>\n<\/tr>\n
Insulation resistance tester (secondary injection)<\/td>\nAuxiliary contact chain continuity and open-circuit state<\/td>\nAs-built wiring diagram; OEM control schematic<\/td>\n<\/tr>\n
Calibration certificates (all instruments)<\/td>\nTraceability of measured values<\/td>\nISO\/IEC 17025 accredited calibration body<\/td>\n<\/tr>\n
OEM assembly drawing and maintenance manual<\/td>\nDimensional tolerances; torque values; lube specifications<\/td>\nOEM document; contract purchase specification<\/td>\n<\/tr>\n
IEC 62271 series \/ ANSI\/IEEE C37 series<\/td>\nElectrical acceptance criteria<\/td>\nIEC, IEEE (external authority)<\/td>\n<\/tr>\n
Project specification and single-line diagram<\/td>\nSite-specific derating, altitude correction, pollution class<\/td>\nOwner’s engineer; EPC contract<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
\n

Contact Box Acceptance Inspection: FAT and SAT Procedure<\/h2>\n

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.<\/p>\n

Pre-Inspection Conditions<\/h3>\n

Contact Spring Force Acceptance Limits<\/h3>\n\n\n\n\n\n\n\n
Contact Rating<\/th>\nMinimum Spring Force<\/th>\nMaximum Spring Force<\/th>\n<\/tr>\n<\/thead>\n
Up to 630 A<\/td>\n18 N per finger<\/td>\n28 N per finger<\/td>\n<\/tr>\n
630 A – 1600 A<\/td>\n25 N per finger<\/td>\n40 N per finger<\/td>\n<\/tr>\n
1600 A – 4000 A<\/td>\n35 N per finger<\/td>\n55 N per finger<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Contact Resistance Measurement<\/h3>\n\n\n\n\n\n\n\n
Contact Assembly Type<\/th>\nFAT Pass Limit<\/th>\nSAT Pass Limit<\/th>\nFlag for Investigation<\/th>\n<\/tr>\n<\/thead>\n
Plug-in contact (up to 1600 A)<\/td>\n<= 50 micro-ohm<\/td>\n<= 75 micro-ohm<\/td>\n> 100 micro-ohm<\/td>\n<\/tr>\n
Draw-out contact (1600 A – 4000 A)<\/td>\n<= 30 micro-ohm<\/td>\n<= 45 micro-ohm<\/td>\n> 60 micro-ohm<\/td>\n<\/tr>\n
Bolted contact<\/td>\n<= 10 micro-ohm<\/td>\n<= 15 micro-ohm<\/td>\n> 20 micro-ohm<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Thermal Imaging at SAT<\/h3>\n\n\n\n\n\n\n\n
Phase-to-Phase Differential<\/th>\nInterpretation<\/th>\nAction<\/th>\n<\/tr>\n<\/thead>\n
< 5 deg C<\/td>\nNormal<\/td>\nDocument and archive<\/td>\n<\/tr>\n
5 deg C – 15 deg C<\/td>\nMarginal<\/td>\nSchedule inspection at first maintenance window<\/td>\n<\/tr>\n
> 15 deg C<\/td>\nAbnormal<\/td>\nDe-energize and inspect contact resistance; do not defer<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

FAT vs. SAT Decision Matrix for Contact Box<\/h3>\n\n\n\n\n\n\n\n\n\n
Inspection Item<\/th>\nFAT Required<\/th>\nSAT Required<\/th>\nFailure at FAT<\/th>\nFailure at SAT<\/th>\n<\/tr>\n<\/thead>\n
Visual – contact fingers<\/td>\nYes<\/td>\nYes<\/td>\nHold shipment<\/td>\nDe-energize; rectify<\/td>\n<\/tr>\n
Spring force<\/td>\nYes<\/td>\nSpot-check (20%)<\/td>\nReject assembly<\/td>\nReplace springs before energizing<\/td>\n<\/tr>\n
Contact resistance<\/td>\nYes<\/td>\nYes<\/td>\nReject assembly<\/td>\nDo not energize<\/td>\n<\/tr>\n
Draw-out alignment<\/td>\nYes<\/td>\nYes<\/td>\nAdjust at factory<\/td>\nAdjust on site<\/td>\n<\/tr>\n
Thermal scan<\/td>\nNo<\/td>\nYes<\/td>\nN\/A<\/td>\nDe-energize if > 15 deg C delta<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
\"Technical
Contact box acceptance checks for resistance, spring force, alignment, and thermal performance.<\/figcaption><\/figure>\n
\n

Bushing and Insulator Acceptance Tests: Criteria and Standards<\/h2>\n

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.<\/p>\n

Insulation Resistance and Polarization Index<\/h3>\n\n\n\n\n\n\n\n\n
Condition<\/th>\nPI Value<\/th>\nInterpretation<\/th>\nAction<\/th>\n<\/tr>\n<\/thead>\n
Dry and clean insulation<\/td>\n>= 4.0<\/td>\nGood dielectric condition<\/td>\nAccept<\/td>\n<\/tr>\n
Marginal (possibly damp or aged)<\/td>\n2.0 – 3.9<\/td>\nMonitor; retest after drying<\/td>\nConditional accept at FAT; retest at SAT<\/td>\n<\/tr>\n
Contaminated or degraded<\/td>\n1.0 – 1.9<\/td>\nSurface leakage or internal moisture<\/td>\nReject; investigate and replace<\/td>\n<\/tr>\n
Severe degradation<\/td>\n< 1.0<\/td>\nActive fault path<\/td>\nReject unconditionally<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Power Factor \/ Tan Delta Limits<\/h3>\n\n\n\n\n\n\n\n\n\n
Bushing\/Insulator Type<\/th>\nMaximum Tan delta at 20 deg C<\/th>\nAlarm Threshold<\/th>\nReject Threshold<\/th>\n<\/tr>\n<\/thead>\n
Oil-impregnated paper (OIP) bushing<\/td>\n<= 0.5%<\/td>\n0.5 – 0.7%<\/td>\n> 0.7%<\/td>\n<\/tr>\n
Resin-bonded paper (RBP) bushing<\/td>\n<= 0.8%<\/td>\n0.8 – 1.2%<\/td>\n> 1.2%<\/td>\n<\/tr>\n
Cast resin \/ epoxy insulator<\/td>\n<= 1.0%<\/td>\n1.0 – 1.5%<\/td>\n> 1.5%<\/td>\n<\/tr>\n
Porcelain insulator (dry)<\/td>\n<= 0.5%<\/td>\n0.5 – 0.8%<\/td>\n> 0.8%<\/td>\n<\/tr>\n
Silicone composite insulator<\/td>\n<= 0.3%<\/td>\n0.3 – 0.5%<\/td>\n> 0.5%<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Hi-Pot Withstand Voltage Reference<\/h3>\n\n\n\n\n\n\n\n\n\n
Voltage Class (kV rated)<\/th>\nIEC PFWV (kV rms)<\/th>\nSAT Applied Voltage (80%)<\/th>\nDC Equivalent (x1.414)<\/th>\n<\/tr>\n<\/thead>\n
7.2 kV<\/td>\n20 kV<\/td>\n16 kV<\/td>\n22.6 kV DC<\/td>\n<\/tr>\n
12 kV<\/td>\n28 kV<\/td>\n22.4 kV<\/td>\n31.7 kV DC<\/td>\n<\/tr>\n
24 kV<\/td>\n50 kV<\/td>\n40 kV<\/td>\n56.6 kV DC<\/td>\n<\/tr>\n
36 kV<\/td>\n70 kV<\/td>\n56 kV<\/td>\n79.2 kV DC<\/td>\n<\/tr>\n
52 kV<\/td>\n95 kV<\/td>\n76 kV<\/td>\n107.5 kV DC<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Partial Discharge Limits<\/h3>\n\n\n\n\n\n\n\n\n
Component<\/th>\nPD Inception Voltage (minimum)<\/th>\nMaximum Permissible PD Level<\/th>\n<\/tr>\n<\/thead>\n
GIS spacer insulator<\/td>\n>= 1.2 x U0<\/td>\n<= 5 pC at 1.1 x U0<\/td>\n<\/tr>\n
Epoxy cast bushing >= 12 kV<\/td>\n>= 1.1 x U0<\/td>\n<= 10 pC at U0<\/td>\n<\/tr>\n
OIP condenser bushing<\/td>\n>= 1.1 x U0<\/td>\n<= 10 pC at U0<\/td>\n<\/tr>\n
Composite hollow insulator<\/td>\n>= 1.0 x U0<\/td>\n<= 20 pC at U0<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Corrective Action Decision Logic for Bushings and Insulators<\/h3>\n