{"id":502,"date":"2026-10-08T15:29:57","date_gmt":"2026-10-08T07:29:57","guid":{"rendered":"http:\/\/www.ongnau.com\/blog\/?p=502"},"modified":"2026-10-08T15:29:57","modified_gmt":"2026-10-08T07:29:57","slug":"what-are-the-maintenance-records-of-transformer-bushings-4f54-562387","status":"publish","type":"post","link":"http:\/\/www.ongnau.com\/blog\/2026\/10\/08\/what-are-the-maintenance-records-of-transformer-bushings-4f54-562387\/","title":{"rendered":"What are the maintenance records of Transformer Bushings?"},"content":{"rendered":"

Hey everyone, it\u2019s Mia here from the transformer bushing team \u2013 I get questions about maintenance records all the time, mostly from new substation technicians or plant managers who\u2019re still figuring out how to keep their gear running. A lot of folks don\u2019t realize that solid, up-to-date maintenance records for bushings aren\u2019t just paperwork; they\u2019re your first line of defense against unexpected outages, and honestly, they save you way more money than they cost to keep track of. Let\u2019s break this down like we chat on our weekly tech calls, no stuffy engineering jargon that makes your eyes cross. Transformer Bushing<\/a><\/p>\n

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First off, what even counts as a \u201cmaintenance record\u201d for bushings? I\u2019ve had customers come at me asking for \u201cbasic paper logs\u201d and then realize they miss super critical stuff that could\u2019ve prevented a blown transformer last month. Let\u2019s start with the non-negotiables that every single bushing should have, no exceptions. When we ship a bushing out, we hand over a starter record (I call it the birth certificate for the part, helps me track back if there\u2019s ever a batch issue) \u2013 that has the serial number, model specs, test results from our factory floor, and the date it was installed. But maintenance records aren\u2019t one-and-done; they\u2019re a running thread from install all the way to retirement.<\/p>\n

Let\u2019s start with the first big section: pre-emptive, scheduled maintenance logs. This is the stuff you do every few years, not when there\u2019s a problem, and it\u2019s the bulk of your record. For our standard composite bushings (the ones that don\u2019t use oil, super popular now because they\u2019re low-maintenance), the schedule is usually every 3 to 5 years, depending on the environment. If your substation\u2019s in a coastal area with salt air or an industrial zone with soot, you bump that down to every 2 years \u2013 that\u2019s a huge mistake I see people make, they copy the schedule from a rural substation and wonder why their bushings get corroded. What do you log during these checks? First, visual inspections \u2013 note any cracks on the silicone sheds, dust or dirt buildup that could mess with insulation, rust on the mounting flanges (super common in humid places), or any signs of leakage (for oil-impregnated paper, or OIP, bushings). Then there\u2019s the electrical testing, which is non-negotiable. You need to log the tan delta (dielectric loss) test, capacitance test, and partial discharge (PD) readings every time. I\u2019ve got a customer who refused to do annual PD tests, and their bushing had a tiny internal defect that popped into a full failure right during a storm \u2013 the records would\u2019ve caught that PD spike 2 years prior.<\/p>\n

Next up, corrective maintenance records. This is when something breaks or acts weird, and you fix it. For example, if you notice a small crack on a silicone shed, you log when you fixed it, what you used (we sell specialty repair kits for small cracks, just saying), the pre-and-post-test results to make sure it\u2019s insulated properly. If you had to replace a bushing, you log the serial number of the old one, why it failed, when you installed the new one, and any compatibility checks you did to make sure it works with your transformer. A lot of people skip logging why a bushing failed, but that\u2019s how you end up with the same issue again \u2013 like if your old bushing failed because of salt corrosion, you can upgrade to a salt-resistant coating or composite sheds for the new one, that\u2019s only possible if you have the old failure record.<\/p>\n

Wait, and don\u2019t forget thermal imaging checks! That\u2019s a super easy, low-cost thing that most techs skip, but it\u2019s gold. Every year, you should do a thermographic scan of the bushing top (where the conductor connects) and the bottom flange. If the temperature difference is more than 10 degrees Celsius, that\u2019s a red flag \u2013 could be a loose connection, which will cause overheating and eventually melt the bushing. Logging thermal readings every year lets you track that temperature creep before it becomes a disaster. I had a tech tell me last month that they caught a loose connection on their main transformer bushing because of a 7-degree temp spike, fixed it during a routine outage, and avoided a $50k emergency repair. That\u2019s exactly what records are for.<\/p>\n

Now, what about special cases? Like if your substation is in a seismic zone, or you had a flood or lightning strike last year \u2013 those events need their own entry in the maintenance records. Lightning strikes can cause internal PD even if you don\u2019t see external damage, so you need to do a full set of tests right after, and log that the strike happened. Same with a flood \u2013 if water gets into the bushing base, you need to dry it out, test it, and note that flood event so future techs know to check that area next time. I worked with a utility in Texas after their 2021 winter storm \u2013 they pulled up their bushing records, and noticed that 3 of their OIP bushings had water intrusion after the flood, so they upgraded to composite ones the next year. Saved them from having to replace 5 more during the 2022 heatwave.<\/p>\n

A common question I get is: how long do I need to keep these records? Honestly, at least until the bushing is retired, and even a year or two after that. Our team had a case where a 10-year-old bushing failed, and the utility had the old records showing that the tan delta was slowly increasing every test \u2013 that let us confirm the failure wasn\u2019t a manufacturing defect (it was a salt buildup issue from their location) and they didn\u2019t waste time filing a warranty claim that wouldn\u2019t have stuck. If they\u2019d lost the records, they would\u2019ve been out the full cost of the bushing and downtime.<\/p>\n

Wait, let\u2019s talk about common mistakes people make with maintenance records, because I\u2019ve seen these so many times. First, they write everything on random paper scraps, then lose them when a tech quits. Or they take photos, but don\u2019t label the serial number, date, or test result \u2013 so a photo of a crack is useless if you don\u2019t know which bushing it\u2019s on. Another big one: they only log the good results, not the small issues. Like, if a tan delta is slightly above the threshold, they just ignore it instead of logging it and planning for a recheck in 6 months. That\u2019s how small issues turn into big failures fast. Also, a lot of people forget to include the environmental conditions during testing \u2013 like if it\u2019s raining when you do the tan delta test, that can throw the number off, so you need to note that, and the next test will be more accurate.<\/p>\n

Now, how should you actually organize these records? It doesn\u2019t have to be a fancy, expensive software (though there are good ones, I won\u2019t plug a specific one), but it should be easy to access for every tech on the team. A spreadsheet works if you have a small substation, but for larger utilities, a cloud-based system where you can attach photos, test PDFs, and event notes is way better \u2013 you can pull it up on your phone during an outage, no need to carry a huge binder. Our team actually helps customers set up a basic template if they want, no charge \u2013 just send us a note, we\u2019ll share a sample that has all the fields we mentioned: serial number, install date, visual check notes, test results, repair\/change logs, event notes.<\/p>\n

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At the end of the day, good maintenance records for transformer bushings aren\u2019t just a regulatory thing (though some areas require them for safety inspections) \u2013 they\u2019re your peace of mind. They let you plan out maintenance costs, avoid unexpected outages, and make sure your transformer is running at peak efficiency for as long as possible. If you\u2019re struggling to keep up with your records, or you need help interpreting any test results, or you\u2019re looking to upgrade to lower-maintenance composite bushings for your facility, our team is here to help. We work with utilities, industrial plants, and substation operators all over, and we\u2019re happy to walk you through how to set up your records, or replace old bushings with more reliable ones that fit your needs. Just reach out to our team to chat through your specific setup, no obligation.<\/p>\n

Pressure Relief Valve<\/a> References<\/p>\n

    \n
  1. IEEE Std C57.19.00-2018, Standard for General Requirements for Bushings for Liquid-Immersed Transformers and Reactors<\/li>\n
  2. North American Electric Reliability Corporation (NERC) Transformer Maintenance Guidelines, 2020 Edition<\/li>\n
  3. International Council on Large Electric Systems (CIGRE) Technical Brochure 765: Maintenance of High-Voltage Transformer Bushings, 2019<\/li>\n<\/ol>\n
    \n

    Hebei Anmei Electrical Equipment Co., Ltd.<\/a>
    Hebei Anmei Electrical Equipment Co., Ltd. is one of the most professional transformer bushing manufacturers and suppliers in China, specialized in providing high quality products and service. Please feel free to buy customized transformer bushing made in China here from our factory. Contact us for quotation.
    Address: Hejian Yingzhou Economic Development Zone, Cangzhou City, Hebei Province
    E-mail: sales@anmeielec.com
    WebSite:     https:\/\/www.anmeibushing.com\/<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

    Hey everyone, it\u2019s Mia here from the transformer bushing team \u2013 I get questions about maintenance … What are the maintenance records of Transformer Bushings?<\/span>Read more<\/a><\/p>\n","protected":false},"author":43,"featured_media":502,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[465],"class_list":["post-502","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-industry","tag-transformer-bushing-4395-565422"],"_links":{"self":[{"href":"http:\/\/www.ongnau.com\/blog\/wp-json\/wp\/v2\/posts\/502","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/www.ongnau.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/www.ongnau.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/www.ongnau.com\/blog\/wp-json\/wp\/v2\/users\/43"}],"replies":[{"embeddable":true,"href":"http:\/\/www.ongnau.com\/blog\/wp-json\/wp\/v2\/comments?post=502"}],"version-history":[{"count":0,"href":"http:\/\/www.ongnau.com\/blog\/wp-json\/wp\/v2\/posts\/502\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"http:\/\/www.ongnau.com\/blog\/wp-json\/wp\/v2\/posts\/502"}],"wp:attachment":[{"href":"http:\/\/www.ongnau.com\/blog\/wp-json\/wp\/v2\/media?parent=502"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/www.ongnau.com\/blog\/wp-json\/wp\/v2\/categories?post=502"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/www.ongnau.com\/blog\/wp-json\/wp\/v2\/tags?post=502"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}