Electrical FailuresNot related To Weather

IMIA 51st Conference

1st – 5th September 2018

Singapore

Working Group

Name Company ExperienceMamoon Alyah (Chair) CEERISK Consulting Forensic EngineeringOliver Thoma Advanta Global Loss AdjustingJeff Ashman Advanta Global Loss AdjustingBrendan Reed Codan UnderwritingTom Kristiansen Codan UnderwritingMilind Bhatawadekar Bhatawadekar Loss Surveys Loss AdjustingMichael Shehan Qatar General Claims Mike Robertson Liberty Specialty UnderwritingPaul Lowrie Clyde & Co SolicitorSimon Dejung Scor Global UnderwritingBen Adams Charles Taylor Risk Engineering

What is an electrical failure?

• Collins dictionary: “Electrical failure is an instance when an electricity supply stops working”

• IEC: “failure: the termination of the ability of an item to perform a required function”

Why should insurers car?

• Defining electrical failure as loss of power provides the general perspective of utilities and IPP’s that view reliability of the power system in terms of availability of supply, rather than specific incidents that are caused to or can lead to physical damage to property. • For instance, operator error that

results in interruption of power supply, through it does not involve any physical damage, is considered an electrical failure.

• This broad definition may prove to be irrelevant to insurers who are mainly concerned about events that involve physical damage to property.

Electrical failure v.

Electrical fault

• Electrical System fault as:“a condition in the electrical system that causes failure of the electrical equipment in the circuit such as: Generators, Transformers, Busbars, Cables and all other equipment in the system that operate at given voltage level”

• OEM’s define faults as:A fault in electrical equipment or apparatus is as an imperfection in the electrical circuit due to which current is deflected from the intended path. In other words, the fault is the abnormal condition of the electrical system which damages the electrical equipment and disturbs the normal flow of the electric current.

How should insurers define

“Electrical Failure”?

• When considering the definition from an insurance perspective, we relied on definition of two elements: “accident” and “object” when considering electrical failures/faults• “Accident”: means an unforeseen

breakdown of an “object” resulting in physical damage to the object, that requires that the “object” be either repaired or replaced before normal operations can be resumed. It is becoming more common for policies to no longer require the accident to be SUDDEN, as long as it is fortuitous and unforeseen

• “Electrical Objects”: Electrical equipment or apparatus used for the generation, transmission, Distribution or utilization of electrical power.

Our definition of Electrical

Failures (or is it faults?)

• We limit the scope of our paper to electrical faults and not electrical failures.

• We define electrical faults, as:any unforeseen abnormal condition (imperfection) in the electrical circuit which causes deflection of current flow from intended path that leads to physical damage to equipment.

Our Scope

• The scope of this paper is limited to:• Unforeseen abnormal conditions• Causes electric current to flow outside its

intended path, which can be caused by a breach of containment system (insulation breakdown) used to manage the flow of electrical current

• As a result, the fault causes physical damage to equipment which necessitates repair or replacement before it can be returned to normal operations

• Electrical faults are caused by • equipment failures (transformers, rotating

machines, cables, bus bars, switchgear assemblies …etc),

• human errors (manufacturing, commissioning and testing, operation …etc.) and

Examples of Electrical Faults

Electrical Failures in Transformers

Electrical Failures in Switchgear

Electrical Failures in Transformers

Electrical Failures in Substations

Devastating impact of a fault

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Paper Structure

• Electrical System Components

• Types of electrical faults

• Common failure modes, causes and impact

• Insurance consideration• Risk assessment

• Loss prevention• Inspection and

condition monitoring• Maintenance and

inspection programmes• Underwriting• Claims

• Investigation of cause• Application of

exclusions and warranties

• Loss examples• EHV Bushing failure• Transformer fire• Switchgear fault• Fault in MCC• Cable Fault

Paper Focus

Accident Object

Electric Fault in MCC Cabinets

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Loss Circumstances

• The loss occurred in the electric room in the concrete plant and involved a MCC (Motor Control Centre) used to operate several pieces of equipment in the plant.

• Fire broke out in the electric room

• PD was limited to contents of the electric room $230,000

• BI resulting from shut down as a result of the loss was in the $millions

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Cause of Loss

• Electric fault occurred at the back of one of the switches (buckets) in the MCC

• The fault led to significant heat damage to the metal enclosure and everything around it

• A fire ensued when wire insulation was burned

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Electric switches

• Each switch plugged into the busbar inside the cabinet

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Connection Clasps

• Each control bucket was plugged into the cabinet where the busbars locked into location using pressure clasps

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Busbars

Bus bars ran up and down the cabinet and switches plugged into them

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Cause

• After sometime, the mechanical clasps start losing tension

• This creates a high resistance contact

• Heat starts building up around the contact point

• Heat causes oxidation of the contact surface which generates further heat

• Eventually, insulating barriers breakdown and an electrical fault occurs

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Transformer Failure

• It was claimed that two power transformers located in the basement of a building, were damaged due to 10 week dormancy imposed during power outage related to a covered flooding loss

• There was no flooding from the loss to the basement where the transformers were located. • The humidity levels were reported to

be high due to weather conditions. • Weather condition changed to colder

temperatures over the period when the transformer was de-energized.

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Background information of the transformers

• The two transformers were approximately 25 years old.

• Both transformers were periodically maintained.

• The transformers were tested and cleaned approximately four (4) years prior to the loss.

• The windings were inspected

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Windings

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Insulation Breakdown

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Cause

• Damaged as a result of electrical fault consistent with insulation breakdown.

• Insulation breakdown was caused by condensation and moisture penetration due to prolonged shut down and improper re-energizing procedure.

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Reactor

• ABB 90 kV 3-ph reactor, failed.• The reactor was in service at the time

and had been installed as a replacement for another reactor, which experienced similar failure at an earlier date.

• Both failures occurred during a thunderstorm

• It was claimed that lightning is the cause

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Inspection & Testing

• Testing indicated there was an electrical sort in one of the three windings

• Inspection of leads and connection showed them to be free of any damage

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Windings

• Excessive discolouration on the windings• Discolouration was wide spread

throughout the reactor

• Small particles from the electric short were found in other windings suggesting particles floated in the oil

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Electric Fault

• Electric short occurred internally between windings

• Energy from the fault caused parts of the winding to disintegrate

• Beads floated in eth oil

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Cause

• 1. The failure of the reactor was caused by electrical short between inner windings on phase A.

• 2. The electric short was caused by failure of the winding insulation. The root cause of the failure is consistent with normal wear and tear conditions.

• 3. The reactor exhibits signs of age related deterioration of the insulation on all different parts of the windings.

• 4. No signs of external causes of failure were observed on any of the winding leads or connections.

• 5. Review of inspection and cause analysis reports issued by the manufacturer and independent engineering investigator indicate that the failure in Reactor#1 was also due to age related deterioration and no signs of external causes were identified.

Case Study 500MW H2/Water cooled Generator.

Station Commissioned in Late 60sPlant Life Extension program mid-2000s• FGD• Steam Turbine Retrofit• Generator Stator Replacement• Generator rotor rewinds.

Case Study 500MW H2/Water cooled Generator.

18th May 2009 17:22 – Stator Water Pumps stopped.18:00 – Unit Tripped on Stator

Earth Fault• Stator Scrapped• Rotor required a full forging re-validation and rewind• 4 month outage.

Burn Damage to Generator Casing

Damaged Windings

Fault on NDE Slot Exit

Fault at DE End windings

Stator water Pump

ChangeoverStator heating

Alarm

GCMx

Stator Water Pump Stops

Dead

GeneratorStator Water

Flow Fail Protection

GCM activity vs Average Slot Temperature

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17:16:48 17:24:00 17:31:12 17:38:24 17:45:36 17:52:48 18:00:00 18:07:12 18:14:24 18:21:36

Time

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Stat

or B

ar T

emp

Stator Earth Fault 18:00Stator water pump off (17:22)- Flow Failure Alarm

38minutes

GCM Verified

14

Stator Temp High Alarm (17:30)

30minutes

Between Top and Btm

Learning Points

• Protection Testing (ideally directly from plant)

• Flow switches – Replace old technology (pressure switches across an orifice)

• Control room alarm rate• Saunders Valve (correct grades and

lifetimes)• Remove the risk (Engineer out the risk

of water systems)

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High Voltage Transformer Explosion

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The Loss

• Transmission substation in California, USA

• 374 MVA Single Phase Transformer

• Explosion occurs at 18:30 on July 7, 2003

Damage to the Transformer

Damage to The Substation

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HV Bushing

• Traces of PD and HV fault

Tear Down

Internal Inspection of the Tank

LV Leads Intact

Coil Disassembly

Observations: Static Discharge

Observation: Arc Tracking

Analysis

Signs of electrostatic discharge

Signs of arc tracking

Signs of gradual damage to insulation

Conclusion

Electrostatic Discharge caused by circulation of the oil during cool temperatures

Static electricity starts arcing in the oil with HV leads and conductors

Arc tracking causes stress to the insulation around the HV lead

Conclusions

Process goes undetected for sometime

The HV lead insulation fails and causes massive electric fault

Electric fault causes explosion of the oil, which in turn pushes the bushing and start the fire

Root Cause Cool Temperature

01Oil Circulation

02Electrostatic Discharge

03

Renewable Energy

The Equipment

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Inside the Container

• Two rooms:• Power room: used to

house the power modules and high frequency filters

• Control room: used to house the PLC control cabinets as well as the air conditioning controls.

The Loss

• Two weeks after commissioning, a fire broke out in a container that houses control equipment and power filters designed to supply VARS to the grid

Burn patterns

Point of origin

Electric Fault

Analysis

There were no signs of burning outside of the container

Extensive burn damage in the power control room

The burn patterns in the power room of the container show heavier burning on the side of the room closest to the control section.

Closer examination of the cable connections indicated that there was significant electrical arcing in that area which resulted in significant damage to the cable connections, the brackets and the container walls.

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Root Cause

• Cause of the fire incident is an improper cable connection causing a high resistance contact at the cable connection plate behind the charging transformer located in the corner of the power room

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Lessons Learned

• Electric failures typically have devastating results

• Damage is rarely contained and limited to the part that fails

• Financial consequences can be severe:• Physical damage – PD• Business Interruption – BI• ICOW (Increased Cost of Working)• Liability • Punitive Damages

• Good (thorough and comprehensive) analysis is imperative to assess the risk

• Loss Prevention requires:• Early detection • Quick release and shut down of

electrical equipment, • Fast extinguishing of a short circuit/fire

• Claims handling should cover:• RCA: Root Cause Analysis• Subrogation/Recovery

Is electricity dangerous?