Forensic Investigation

of Power Asset Failures

Investigation : Causes : Evidence : Prevention

OVERVIEW

EA Technology has been supplying forensic investigation, failure analysis and accident investigation services for more than 40 years. We cover every industry, in any country, from EHV transmission and distribution, to low voltage controls and components.

Our forensic investigators provide rapid site investigation services, anywhere in the world. We do this to ensure that on-the-scene examinations are completed before any disturbance of vital evidence occurs.

Failures of medium and high voltage electrical assets often make headline news, such as the underground cable failure, which resulted in 20,000 Liverpool homes being without power, or the transformer failure that left 250,000 Madrid residents in darkness. Similar outages have hit New York, London and Birmingham.

Forensic science is increasingly recognised as the key to enhancing the safety and reliability of electrical assets, by enabling us to understand the sequence of events leading to failure. Expert examination of failed assets is vital to improving equipment design and maintenance procedures. It also enables operators to make informed decisions on asset management, including investment and replacement. Lessons learnt from failure investigations will reduce the occurrence of expensive and dangerous failures and ultimately lead to an increase in the safety and reliability of assets.

Making sense of the often charred and twisted results of an equipment failure relies on two approaches, used in tandem: sophisticated laboratory techniques and expertise in interpreting evidence and patterns of events, based on nearly 40 years of similar investigations. Our collective know how is supported by a database that contains records of how thousands of assets have deteriorated and failed in the past.

In order to obtain maximum benefit from a failure investigation it is essential that correct procedures and methods are adopted and that appropriate analytical techniques are used.

Basic Causes of Failure

The majority of failures are as a result of one or more of the following factors:

• Design
• Materials Selection
• Fabrication and Processing
• Operating and Service Conditions
• Human Error
• Vandalism and Illegal Activity

Objectives of a Failure Investigation

In all failure investigations and subsequent analysis whether the failure is a minor one or a major catastrophic one the two following objectives should be satisfied.

• Identify and determine the primary cause of the failure
• Identification and provision of data to seek the best solution to prevent similar failures in the future.

General Procedures and Stages of an Analysis

In all forensic investigations it is critical good procedures and methods are employed during each stage of the investigation and the subsequent analysis.

Although the sequences listed below are subject to variation depending on the nature of a specific failure, the principal stages that comprise the investigation and analysis of a failure are as follows:

• Collection of Background Data and Selection of Samples
• Preliminary Examination of the Failed Parts
• Non-destructive Testing
• Specimen Preparation
• Macroscopic/microscopic Examination
• Electrical testing
• Mechanical Testing
• Chemical Analysis
• Testing under Simulated Service Conditions
• Determination of Failure Mechanism
• Decision/Action following Failure Analysis

Benefits

• Improvements in engineering design, materials and maintenance practices
• Condition assessment techniques
• Reduction in failure rate
• Increase in reliability and safety
• Significant cost savings
• Reduction in environmental impact
• Data to support asset management policies
• Evidence in liability and legal cases
• Increased sales and competitiveness

Case Studies

To view more information on any of the case studies below please select the corresponding title.

	EA Technology investigates ‘catastrophic power failure’ in Bermuda EA Technology has completed its report on the causes of the fire which cut electrical power in Bermuda on July 14...
	Oil Filled RMU: Contact overheating due to design A Ring Main Unit (RMU) was found to have been operating at a high temperature. The high operating temperature of the unit was due to thermal runaway at all six of the circuit contacts...
	Failure of an OHL shackle due to metallurgical defect An overhead line (OHL) shackle had fractured in two places and the overhead line had consequently become detached. This type of assembly is in widespread use within the DNO. The fracture surfaces were examined using...
	RMU Indicator plate: Failure due to imprecise tooling/poor quality control During a ‘dead’ operation of an RMU the ON/OFF indicator plate became detached and fell into the bottom of the switchgear tank. The evidence suggested that the indicator failed due to poor quality metallic-arc welds...
	Isolator springs: Failure due to fatigue A number of isolators were found open circuit. With the failure of each unit a significant amount of production was lost for the company involved. The front panel of the isolator was removed in order to examine internal components...
	630A Fuse Isolator: Failure due to Sulphur Contamination The visual examination of 630A fuse isolator found that all the exposed silver plated contacts had significantly degraded due to airborne sulphur. Relatively high concentrations of airborne sulphur can occur due to...
	Copper conductor: Exhibiting pitting corrosion One selective form of corrosion is known as pitting corrosion because it is highly localised...
	Circuit Breaker Spouts: Partial Discharge activity resulting in surface tracking The first solid insulation used for electrical applications was porcelain. Such ceramic materials are very good insulators and are largely immune to electrical degradation...
	Circuit breaker failure: Catastrophic failure due to human error Following maintenance a fitter left the test probe across two phases of the busbar conductors. The incident occurred when the moving portion...
	Failure due to illegal activity Failures due to illegal activity and vandalism are difficult to legislate against. Illegal activity such as the theft of copper busbars...