Root Cause Analysis (RCA) is a sophisticated iterative process, designed to investigate and categorize the root causes of events or failures that may have catastrophic impacts to the overall performance of the system. RCA as an engineering problem solving-tool uses a comprehensive collection of systematic approaches to reveal the causes of failures and establish a flexible and effective framework for the necessary corrective and preventive actions.

In wind energy, RCA is one of the most important and valuable tools to ensure system's reliability and eliminate the recurrence of adverse events or potential failures in the near future. The failure symptoms can be used to identify the causal factors that not only may influence the performance of the energy plant itself, but as well availability, stability, economic viability and quality of the system as a whole. The analytic investigation of the adverse effects reveals new methods and mechanisms for the mitigation of hazardous phenomena and sentinel events that may influence wind energy plants performance and last but not least, to prevent ecosystem and ensure human health and safety.

When is RCA necessary?

Generally speaking, there are a number of reasons for every equipment failure, but there is also a definite synergistic relationship between the events and consequences that may lead to that failure. An RCA investigation, deciphers the effects, symptoms and causes from the final failure, back to the root failure-cause factor. Thus, we can say that the main purpose of RCA is to solve these problems that affect project's performance that, in turn to improve the reliability and performance stability of the energy plant. The main scope of this process is to offer a better and comprehensive understanding why these events and sectoral impacts have been occurred in order to formulate a preventive action, rather than, to incriminate the problematic part or component responsible for the accident or failure.

The root cause analyst should answer a sequence of critical questions: What it happened, How it happened, Why it happened and How to eliminate it so it will not happen again. The very first step to identify the cause of the failure-incident, is the information availability from different sources. These could include:

1	Witness statements or interviews from the staff involved
2	The incident's environment or place
3	The equipment or mechanism involved in the event
4	The manifacturer documentation or available standards

Hypotheses, assumptions and personal perceptions which cannot necessarily establish root cause objectivity have to be ignored or even rejected. The RCA conclusions should be based on discipline approaches and scientific methods which have been prooved and verified by thorough investigation.

Cause and Effect Relationship

When analyzing cause-and-effect relationships we need to think back and forth. General speaking, causation is the fundamental relationship between cause and event. The synergistic interactions between events and causes are non-linear and non-unidirectional. This amphidromic relationship could be lead to erroneous assumptions. Identifying and grouping logically failure related factors and parameters, is the only way to synthesize the key contributors to the incident with main scope to mitigate the severity of the consequnces and implement effective corrective actions.

Root Cause Analysis Tools and Methodologies

Nowadays, there are a plethrora of root cause analysis methods and tools that could be used to investigate the incident-failure and promote effective solutions or corrective actions to prevent reoccurrence. There is a well-defined distinction between an RCA method and a tool. A tool is distinguished by its limited use, while a method may involve many different steps and processes to identify the problem and has wide usage. Below are just some of the most common RCA tools and methods:

1	Events and Causal Factors Charting (Method)
2	Barrier Analysis (Tool)
3	Tree Diagrams (Method)
3	Pareto Analysis (Tool)
4	Why-Why Chart (Method)
3	Change Analysis (Tool)
2	Storytelling Method (Method)
3	Failure Modes and Effect Analysis (Tool)
3	Fault Tree Analysis (Method)
4	Realitycharting (Method)
3	Brain Storming (Method)
3	Nominal Group Technique (Method)
3	Fish Bone Diagrams/Cause and Effect Charts (Tool)

The following flow diagram illustrates a Fault Tree (a systematic approach) as a paradigm of this "polyphonism". Starting with an initiating undesirable event (Top Event) and flowing backward through the system, we can identify all the potential successive failure events (Basic Events) that could cause that top event to occur.