Surge Arrester Common Faults, Cause Analysis & Handling Principles

Learn common surge arrester faults, their causes, and handling principles – a practical guide for reliable overvoltage protection.

Rockwill

Field: Manufacturing

10Year<

China

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This document primarily addresses common metal-oxide surge arresters (MOA), while also covering typical fault characteristics of valve-type and gapped arresters.

Fault characteristics, test items, and judgement criteria may vary across different structural types, voltage levels, and manufacturers. In practice, reference shall be made to equipment technical documentation, site operating procedures, and relevant standards.

Safety Notice: This document is for knowledge learning and O&M reference only and does not constitute on-site operating instructions. When de-energisation, isolation, maintenance, testing, or fault handling are involved, the site procedures, safety measures, and approval processes of the responsible unit must be strictly followed.

Surge Arresters

1. Abnormal Leakage Current

Leakage current is the core indicator reflecting the internal valve disc condition. Under normal operation, the arrester passes only microampere-level leakage current at power frequency. Abnormal changes in leakage current often indicate internal defects.

Fault Manifestations

Online monitor indicates abnormal increase, full-scale deflection, decrease, or zero reading of leakage current
Three-phase values unbalanced, or monitor issues data over-limit alarm

Possible Causes

Severe contamination of external insulation, causing increased surface leakage current
Internal valve disc ageing, degraded non-linear characteristics, increased power loss
Seal failure leading to internal moisture ingress, reduced insulation performance
Grading ring tilt causing equivalent capacitance change, increased capacitive current
Monitoring instrument fault, shield wire shorted, or connection wire broken
Base insulation degradation causing current diversion abnormality

Judgement Methods

Cross-verify with clamp-on ammeter to rule out instrument fault
Use dedicated tester to measure total current and resistive current; compare three-phase deviation and change from previous values
Combine with infrared thermal imaging to comprehensively analyse thermal field distribution and temperature trend
Check discharge counter operation to determine if abnormal operation occurred

Criteria & Handling Principles

Leakage current criteria are classified into three severity levels with corresponding handling requirements:

Abnormal Warning (attention required if any condition occurs):

Online monitoring data change exceeds 10%
Total current sudden change exceeds 20% of initial value
Three-phase leakage current unbalance exceeds 15%

→ Action: Strengthen monitoring, shorten patrol interval, arrange offline test if necessary

Serious Defect:

Leakage current reading exceeds 1.2× initial value
Resistive current component exceeds 30% (specific criteria per equipment technical documentation and Technical Specification for Live-Line Inspection of Electric Equipment)

→ Action: Register as serious defect, report to dispatch and maintenance, arrange offline inspection ASAP

Critical Defect:

Leakage current reading exceeds 1.4× initial value

→ Action: Immediately report to dispatch, apply for out-of-service handling

Absolute Value Criteria (for offline testing):

At 0.75× DC reference voltage: total current < 1 mA, resistive component ≤ 30%

Other Handling Requirements:

Zero reading: tap meter gently to check if stuck; if unrecoverable, register defect and replace monitoring device
Specific criteria shall follow equipment technical documentation, site operating procedures, and relevant standards

2. Abnormal Body Heating

Under normal operation arrester heating is minimal. When internal valve discs age or become damp, power loss increases significantly, manifesting as abnormal temperature rise.

Fault Manifestations

Overall or local temperature rise; hotspots generally near upper part with uneven distribution
Multi-unit arresters show abnormal temperature gradient from top to bottom

Possible Causes

Internal valve disc ageing → degraded non-linear characteristics, increased power loss, uneven voltage distribution
Internal moisture ingress → increased surface leakage current → additional heating

Judgement Methods

Periodic detection with infrared thermal imager; prefer stable ambient conditions without strong solar interference
Combine with historical temperature maps and comparison with similar equipment
Do not judge internal defects from a single infrared result alone; combine with offline testing for comprehensive judgement

Criteria & Handling Principles

Infrared detection criteria in three severity levels:

General Defect:

Temperature difference > 0.5 K
→ Action: Register defect, strengthen monitoring

Serious Defect:

Temperature difference > 1 K
Phase-to-phase temperature difference > 1 K (judged as internal abnormality)
Infrared relative temperature difference ΔTmax ≥ 30%
→ Action: Register serious defect, report to dispatch and maintenance, arrange offline inspection ASAP

Critical Defect:

Local temperature rise > 5 °C above ambient
Temperature difference with surrounding equipment > 10 °C
→ Action: Immediate disassembly inspection; immediately report to dispatch, apply for out-of-service handling

Other Handling Requirements:

Report abnormal heating to dispatch and maintenance immediately; apply for offline inspection if necessary
Maintain adequate safety distance when approaching arrester; prioritise remote infrared observation
Infrared detection cycle per site operating procedures and infrared detection technical specifications

3. External Insulation & Appearance Faults

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External insulation is the first line of defence against environmental attack; damage directly affects safe operation.

Fault Manifestations

Porcelain housing or composite housing: cracks, fractures, damage, missing sheds, electrical erosion traces
External insulation surface: discharge traces, sparks, night-visible discharge
Silicone rubber sheds: damage, deformation, ageing cracks
Pollution flashover or ice flashover phenomena

Possible Causes

Severe weather (lightning, hail, ice accretion) causing mechanical damage
Severe surface contamination → uneven voltage distribution → local discharge
Ice accretion or icicle bridging → reduced insulation strength

Handling Principles

Classified by crack severity:

Minor cracks, no discharge: register defect, strengthen patrol monitoring
Large cracks or discharge present: immediately report to dispatch, apply for outage and replacement
Cracks found during thunderstorm: maintain operation if possible; handle after thunderstorm passes

Other Requirements:

If replacement not immediately possible: apply paint or epoxy resin as temporary moisture barrier at cracks
Clean surface contamination promptly; severe flashover → apply for outage handling
Post-ice-weather special patrol: check external insulation ice accretion and icicle bridging
Maintain safety distance during patrol

4. Arrester Explosion or Rupture

Most severe fault form; often accompanied by system protection operation; requires emergency handling.

Fault Manifestations

Arrester body explosion, smoke, fire
Monitoring system issues protection action, breaker trip signals
Adjacent equipment external insulation possibly damaged

Possible Causes

Neutral-ungrounded system single-phase earth fault → healthy-phase voltage rises to line voltage for prolonged period → arrester sustained overvoltage → thermal breakdown
System ferroresonance overvoltage → arrester discharge burns internal elements
Poor spark gap extinguishing performance → re-ignition after operation burns valve discs
Poor sealing → internal moisture → degraded electrical characteristics → thermal breakdown

Handling Principles

Record monitoring system alarms and protection actions; inspect equipment damage on site
Permanent earth fault caused: Prohibit use of isolator to remove faulty arrester
No permanent earth fault: After thunderstorm, open faulty-phase isolator to remove and replace
Pulverising explosion: also inspect adjacent equipment external insulation damage
All operations per dispatch instructions; no unauthorised operations

5. Internal Moisture Ingress

Seal failure is the primary cause of internal moisture; insulation performance and electrical characteristics severely degrade after moisture ingress.

Fault Manifestations

Insulation resistance drops significantly
Power frequency discharge voltage decreases
Conductive current significantly increases or shows significant increase vs. previous
Dielectric loss factor tanδ increases (should be < 0.05)
Upon disassembly: core insulation aged to brown-yellow, oily deposits; valve disc side glaze appears matte, loses lustre

Possible Causes

Top tightening nuts loose, sealing gasket aged/cracked
Porcelain housing cracks or sand holes
Bottom test hole not welded securely
Flange connection sealant ineffective
Water accumulation at base → moisture ingress

Handling Principles

Replace aged sealing gaskets; ensure seal structure correctly seated during reassembly
Securely weld bottom sealing holes; seal porcelain cracks
Add drainage holes if base water accumulation occurs
Use high-quality waterproof sealant
Post-repair insulation testing to confirm performance meets standard

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6. Earthing & Connection Faults

Earthing system reliability directly affects arrester protection effectiveness and personnel safety.

Fault Manifestations

Earthing downlead: corrosion, fracture, loosening, detachment
Lead joints: loosening, heating, discolouration
Downlead: broken strands, over-tight or over-slack
Grading ring: displacement, deformation, corrosion, discharge traces

Handling Principles

Connection points: use welding or compression; avoid wrapping/binding
Earthing lead overlap length: 2× flat steel width or 6× round steel diameter
Earthing terminal to protected equipment earthing terminal: short, straight connection → earthing rod & grid
Arrester to main earthing grid: shortest possible downlead; install concentrated earthing nearby
Earthing resistance qualification per relevant technical specifications and site procedures (varies by voltage level, equipment type, station conditions)
Report broken/detached leads to dispatch immediately; handle per procedures

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7. Internal Abnormal Sounds

Arresters should have no abnormal sounds under normal power frequency voltage; any abnormal sound indicates possible serious internal defect.

Fault Manifestations

Internal abnormal sounds, discharge sounds, or irregular sounds
Abnormal odour or burning smell from equipment

Possible Causes

Internal component damage, valve disc breakdown, or internal discharge

Handling Principles

Immediately report to dispatch; take out-of-service measures per procedures; notify maintenance
Under power frequency voltage, arrester internal should have no abnormal sound; occurrence indicates possible damage; principle: should not continue operation
Strictly prohibit unauthorised close approach for inspection

8. Preventive Maintenance Requirements

Patrol Inspection

Patrol Type	Main Content
Routine patrol	Check leads, joints, grading rings, porcelain, seals, earthing downleads, monitoring devices, discharge counters
Post-thunderstorm special patrol	Check counter operation records, surface discharge/flashover traces, lead connections
Post-high-wind/sandstorm	Check lead connections, vertical arrester sway
Fog/haze weather	Focus on porcelain contamination and corona discharge
Ice accretion weather	Check external insulation ice accretion and icicle bridging
Heavy snow	Promptly clear lead snow accumulation and icicles

Discharge Counter Abnormality Criteria:

Operation without system overvoltage: check system records, judge if false operation
Frequent operation: check if arrester has sustained abnormality
No operation at all: check if counter stuck or damaged
Counter interior burnt/blackened: register defect, replace counter, check arrester condition

UV Detection:

UV imager detects external insulation surface partial discharge; best at night or dark environment
Abnormal discharge found: combine with infrared and offline testing for comprehensive judgement

Preventive Testing

Test Item	Applicable Type	Criteria
Insulation Resistance	≥ 35 kV arresters	General: < 2500 MΩ = abnormal; absorption ratio K = R60s/R15s < 1.3 = abnormal. DFS type etc. with special requirements: per equipment technical documentation
Leakage Current	FZ type	Conductive current > 0.6 mA or significant increase vs. previous = abnormal
Leakage Current	Other types	Per equipment technical documentation and test procedures
Reference Voltage	≥ 110 kV	Drop > 10% vs. initial/specified value; if confirmed ageing → recommend retirement
DC Reference Voltage Deviation	All types	Deviation within ±5%
Reference Voltage	All types	Power frequency & DC reference voltages per product technical conditions; allowable deviation vs. manufacturer measured values per relevant standards
Dielectric Loss Factor	All types	tanδ < 0.05; increases significantly when damp
Test Cycle	All types	Per site operating procedures and preventive test procedures

Infrared Detection

Voltage Level	Detection Cycle
All voltage levels	Per site operating procedures and infrared detection technical specifications
Newly installed & after A/B class overhaul re-energisation	Per relevant procedures within specified time for precise measurement

Detection Notes:

Detect preferably on clear nights; avoid solar reflection interference
Data analysis: longitudinal comparison — compare temperature map trends of same equipment across different periods
Do not judge internal defects from single infrared result alone; combine with offline testing for comprehensive judgement

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9. Basic Fault Judgement Flow

Upon discovering abnormality, first judge whether safety is endangered:

Safety endangered (e.g., explosion, fire, internal discharge sound, leakage current > 1.4×): Immediately report to dispatch, take out-of-service measures
Safety not endangered: Record phenomenon → Cross-check monitoring data → Visual inspection → Infrared detection → Offline test if necessary → Register and handle per defect level (General / Serious / Critical)

Edited From：Noah

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Surge Arrester

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Surge Arrester Common Faults, Cause Analysis & Handling Principles

1. Abnormal Leakage Current

Fault Manifestations

Possible Causes

Judgement Methods

Criteria & Handling Principles

Abnormal Warning (attention required if any condition occurs):

Serious Defect:

Critical Defect:

Absolute Value Criteria (for offline testing):

Other Handling Requirements:

2. Abnormal Body Heating

Fault Manifestations

Possible Causes

Judgement Methods

Criteria & Handling Principles

General Defect:

Serious Defect:

Critical Defect:

Other Handling Requirements:

3. External Insulation & Appearance Faults

Fault Manifestations

Possible Causes

Handling Principles

Other Requirements:

4. Arrester Explosion or Rupture

Fault Manifestations

Possible Causes

Handling Principles

5. Internal Moisture Ingress

Fault Manifestations

Possible Causes

Handling Principles

6. Earthing & Connection Faults

Fault Manifestations

Handling Principles

7. Internal Abnormal Sounds

Fault Manifestations

Possible Causes

Handling Principles

8. Preventive Maintenance Requirements

Patrol Inspection

Discharge Counter Abnormality Criteria:

UV Detection:

Preventive Testing

Infrared Detection

9. Basic Fault Judgement Flow

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