Reducing the Risk and Impact of Substation Fires
Although good asset management practices and monitoring solutions allow transformer owners to carefully manage these critical assets, a zero-failure rate is as yet not possible. The risk of a transformer fault causing a fire is low, but not negligible and the consequences can be very severe if it does occur. According to CIGRE Technical Brochure 537, “Guide for Transformer Fire Safety Practices,” the risk of a transformer causing a fire is on average 4% over a typical 40-year service life. If not properly contained, a transformer fire can quickly disable an entire substation, causing major service interruptions for customers. Understandably, transformer owners try to reduce both the causes of fire, and the consequences, through appropriate specifications, design and mitigation measures.
However, when a fire occurs, given the significant cost in terms of lost assets and service to customers, many organizations take the opportunity to learn from the event. The following is a real-world example of how a client of Doble Engineering Company responded to a substation fire.
Moving beyond a root cause investigation
After a substation fire consumed two large power transformers and caused significant damage to cables, gas insulated bus and adjacent infrastructure, a utility engaged consultants to conduct a root cause analysis of the fire. Although the cause was identified, the utility asked Doble for help understanding how the fire spread so quickly and caused a great deal of damage. The company also wanted to review mitigation measures that could be implemented to reduce the likelihood of a similar event in the future.
The utility outlined the following objectives:
- Gain an understanding of how the fire spread so rapidly.
- Identify policies and procedures to reduce the risk of another fire event.
- Suggest practical measures that could be implemented at existing substations to mitigate damage in the event of a future fire.
- Provide design recommendations which could be applied to future substations.
To meet these aims, Doble assembled an experienced team of specialists to take a wide-ranging, holistic evaluation based on international best practices and years of practical experience in the power sector. The team took the following steps:
- Conducted face-to-face interviews with key utility staff and management.
- Examined internal specifications, maintenance procedures and engineering documents.
- Reviewed the existing condition assessment program (inspection, testing, lab reports, maintenance activities, etc.).
- Studied the failure investigation reports.
- Visited the location for a first-hand view of the damage.
- Inspected other substations to gain a complete picture of day-to-day operations.
Doble provides immediate and long-term recommendations to mitigate risk
The investigation uncovered several areas of improvement ranging from simple changes to specifications and better training of personnel, to larger undertakings, such as implementing transformer asset health reviews and international benchmarking of failure statistics. The team also recommended the introduction of key performance indicators (KPIs) for management to track improvements across the organization as the findings were implemented.
Doble presented the study results using a modified version of the common risk hierarchy framework.
In this case, the hierarchy can be reimagined as progressively reducing the risk of:
- Tank rupture
- Localized fire
- Fire spreading
Consequently, some of the recommendations within the risk hierarchy framework were:
- Elimination: Changes to transformer design/specification and civil design.
- Substitution: Use of alternative lower flammability dielectric liquids.
- Engineering controls: Improved maintenance routines, testing and follow-up.
- Administrative controls: Generation of KPIs and other measures to ensure work and remedial actions are completed.
Adopting new processes to reduce risk of fire
As with any study commissioned by an asset owner, there is a need to balance factors such as the cost effectiveness and practicality of the recommendations in the context of its wider corporate governance framework. Other factors become important when it comes to prioritizing investment, for example, the loads supplied or the impact of a fire on surrounding infrastructure from a specific substation. Although the risk of fire can never be eliminated entirely, all asset owners may benefit from three simple principles:
- Learn from past issues and improve your specifications. Keep abreast of changes to IEC/IEEE standards and update your specifications appropriately.
- Monitor internal management processes for effectiveness. Periodically stress test procedures and conduct scenario exercises.
- Ensure you have access to quality data on your assets and know the failure rates. Consider international benchmarking studies to understand how your performance compares to your peers.
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