Subcommittee SC36A (Insulated Bushings) is part of Technical Committee TC36 – Insulators and its scope is “standardization of insulated bushings and of couplings of these insulators”. Composed of 15 Participating Members and 23 Observers, SC36A deals with all aspects of AC and DC bushings. Even if small by comparison with other Subcommittees, this one has recently been especially active because some Standards within its scope are now in revision status while others will shortly be revised. Moreover, new not yet existing items are in preparation, an important one of which is dimensional standardization.
Below is a brief summary of the Standards as well as their present or future status along with the Working Groups (WG) and Maintenance Teams (MT) involved.
• MT5 – Maintenance of IEC 60137 – Ed. 7 – 2017 – Insulated bushings for alternating voltages above 1kV
The revision of this Standard, the most important of the Subcommittee, is planned to start in Jan. 2025, after closure of the revision of the Standard for DC bushings. The call for experts to reinforce MT5 is scheduled in Sept-2024.
• MT6 – Maintenance of IEC TS 61463 – Ed. 2 – 2016 – Bushings, seismic qualification
The revision of this Technical Specification will start in Jan 2025; a document containing the main topics that are the objectives of this revision will be circulated in mid-2024; a call for experts to reinforce MT6 is scheduled in Oct-2024.
• JWG7 is the Joint Working Group between SC36A and TC14 – Power Transformers for preparation of a new Technical Report (TR) for dimensional standardization of bushings
The objective this paper will be presented during the upcoming 2023 INMR WORLD CONGRESS in Bangkok.
• JAHG8 is the Joint Ad Hoc Group between SC36A and TC14 for preparation of a Preliminary Working Item (PWI 36A-2) of an Application Guide for Bushings above 1kV – something that does not yet exist
The decision during the last 36A General Meeting in Milan in June was to consider splitting the document into several parts dealing with the various main topics, which are wide in scope. The NP (New Proposal) procedure will start after this step, thereby transforming the Ad Hoc Group into a new Working Group, JWG8, and a call for new experts to reinforce this team.
• JMT9 – Maintenance of Standard IEC/IEEE 65700-19-03 – Ed. 1 – 2014 – Bushings for DC Application
The Joint Working Group between SC36A and TC14 of IEC and IEEE Transformer committee, bushings subgroup produced a Committee Draft (CD) in May-2023. National Committees (NC) comments are in the consideration phase by the JMT9.
Bushings Dimensional Standardization
During the 36A Subcommittee General Meeting held in Busan, Korea in 2018, following the proposal of TC 14, it was decided to evaluate a possible standardization of transformer bushings in their three categories: LV, MV and HV.
Standardization of bushings would bring benefits to both users and producers, including:
• decreasing the number of products to be developed, tested and maintained;
• leveraging economies of scale with an overall positive impact on cost and quality;
• reducing inventories as well as lead times;
• simplifying the purchasing process;
• enabling interchangeability of bushings produced by different manufacturers;
• facilitating retrofit of old products with new ones based on more advanced technologies.
Plan to attend the 2023 INMR WORLD CONGRESS, where an assembly of industry experts will review the latest developments when it comes to bushing standards, applications and technologies, including:
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