Many companies wish to use accurate data to make informed decisions about installation and operation of underground and submarine cable systems. To support this approach, CIGRE has been gathering population and failure data from cable systems in service since at least 1977 and an update of the failure statistics has been published approximately every 10 years since then. In 2020, the results of the latest survey were published in Technical Brochure TB 815 covering land and submarine cable systems for the years 2006 to 2015.
However, recently there has been a demand from the industry for more frequent updates of these statistics as well as to provide more up-to-date information. A process time of almost 5 years to collect, analyse and publish the results from the survey is no longer satisfactory for the users of the cable statistics.
Therefore, CIGRE Study Committee B1 on Insulated Cables (SC B1) launched a Task Force (TF B1.81) at its annual meeting in August 2020 to look into the possibility of producing updates of the population and failure statistics for cables every 2nd year.
TF B1.81 completed its work at the Paris CIGRE Session in August 2022 and confirmed its feasibility. The most important outcomes from the work of this task force are the following:
- A Protocol that describes:
- The process to deliver updates of the population and failure statistics on cables every second year starting from 2024
- The developed questionnaire to collect the required service data from the cable owners
- A brief instruction on how to fill in the questionnaire
- An explanation of terms and definitions used in the questionnaire
- How data will be handled to ensure confidentiality for the respondents of the questionnaire
- The expected results that will be published in 2024 – and going forward
- A questionnaire ready to be used to collect the service data for the first update of the population and failure statistics during the fourth quarter of 2022
- A list of contact persons from the cable owners around the world who will receive the questionnaire. This list has been set up with the help of the SC B1 national members.
The continued work (after August 2022) to deliver the first population and failure statistics in 2024 and going forward will be done by a new Advisory Group set up for this purpose under CIGRE SC B1.
Purpose of failure statistics
Failure statistics can be used for several things, but maybe the most important purpose is to assist in making good decisions by using information based on past events, so that uncertainties can be handled and reduced.
Service experience of high voltage cable systems adds value for cable manufacturers who can improve their products, and for cable owners in several stages of the asset's life cycle. It aids in the planning of the system and preparation phases when defining technical solutions, designing the cable system and when purchasing equipment. In the operation phase service experience and equipment reliability are required for asset management: for defining maintenance plans and spare part policies, for lifetime assessment and for the estimation of remaining life.
Reliability is a crucial input for risk management and economic analyses, for both investment decisions and asset management during the life cycle of the asset.
Target Groups for the cable failure statistics
The failure statistics published by SC B1 serves a wide variety of different target groups. The users can be separated into two major groups:
- The first major target group is considered as Experts, where the following stakeholders are included: utilities, cable manufacturers, consultants and advisors, and universities and research institutes, other CIGRE working bodies like SCs and Working Groups. Commonly, these groups or entities are participants within CIGRE. There are also other technical associations - like IEEE, ICC, CEA, ESCA, AWEA, EWEA, ICPC and others - that can be considered to be within this target group of Experts.
- Another large target group - less related to the technical field - but with high interests in the statistics and reliability data of these assets, are governments, regulators, insurance companies, media, project developers and investors such as banks, investment companies etc. These stakeholders who are usually outside the CIGRE community are all included in the second target group.
Scope of the reporting scheme
The complete reporting scheme on service performance for cable systems and the new Advisory Group under CIGRE SC B1 has the following scope/target:
To deliver an update of the population and failure statistics on cables every 2nd year starting from 2024. The results will be published in a paper at the Paris CIGRE Session every second year. The results will cover AC and DC land and submarine cables on voltage levels above 36 kV (Um).
The first update will cover service experience collected from the 10 years 2012 to 2021.
The success of the work is completely dependent on the support and active attendance from the cable owners around the world.
Without any service data reported through the questionnaire there will be no statistics published!
The results from the cable survey will be presented in two sections in the published Session paper. The two sections include the following results:
- Population data: This section presents the population reported for the survey. The population include both cable lengths and number of cable accessories (joints and terminations).
- Service experience: This section presents the calculated failure rates for cables and accessories, the average repair times, and average unavailability time for the cable systems due to failures in service.
Additional information may be published depending on the analysis of the data collected and its relevance for the cable community.
The published statistics on Insulated Cables will be based on the information provided by the Cable Owners who respond to the questionnaire sent by CIGRE SC B1. Therefore, the statistics and its published results cannot be considered as absolute certainties.
The CIGRE rules of confidentiality will be fully respected during the collection of data from the Cable Owners. As a consequence, CIGRE SC B1 will only provide the results in aggregate form so that data concerning a particular owner, or a contributing country cannot be extracted from the results displayed. Where this is not possible, the results will not be displayed. Similarly, the names of cable owners will never be mentioned or disclosed.
The choice of cables studied, the analyses made, and the results published are the responsibility of CIGRE SC B1. Consequently, the statistics will not include all possible criteria, nor will the statistics represent the totality of the existing underground and submarine cables in the world.
The information coming from the respondents will be received by a limited number of persons to ensure the confidentiality of the answers. These persons will have a specific mandate from the Study Committee B1 Chair to hold this position.
On receipt of the questionnaire, the file will be anonymized with an identifier given by the receiver. The file will be renamed with this identifier and the front sheet removed from the file prior to its circulation among the Advisory Group members in charge of preparing the Statistics.
The process to collect service data from the cable owners will be kicked off during the 4th quarter 2022 where the questionnaire will be sent to the contact persons on the list that has been set up with the help of the national members of CIGRE SC B1.
However, it is very important to underline that all cable owners are invited to participate in the survey – and that any data contribution to the cable failure statistics is highly appreciated. Without the active help of the cable owners, it will be impossible to publish the reliable cable failure statistics which is so highly requested from the whole industry. The protocol and questionnaire will be available on the SC B1 page: https://b1.cigre.org/
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