{"id":95611,"date":"2026-06-09T09:30:00","date_gmt":"2026-06-09T07:30:00","guid":{"rendered":"https:\/\/www.lecosinus.fr\/?p=95611"},"modified":"2026-09-14T11:13:26","modified_gmt":"2026-09-14T09:13:26","slug":"why-choose-a-dry-type-mv-transformer-over-an-oil-filled-transformer","status":"publish","type":"post","link":"https:\/\/www.lecosinus.fr\/en\/pourquoi-choisir-un-transformateur-mt-sec-plutot-quun-transformateur-a-huile\/","title":{"rendered":"Why choose a dry-type MV transformer over an oil transformer?"},"content":{"rendered":"<p class=\"wp-block-paragraph\">When selecting equipment for a medium-voltage substation, choosing a transformer is not simply a matter of power rating. \n\nThe installation environment, safety requirements, maintenance constraints, and operating costs all directly influence which technology is the most suitable.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The two most common solutions are <strong>cast resin dry-type transformers and liquid-immersed transformers,<\/strong> commonly referred to as <strong>oil-filled transformers.<\/strong> \n\nEach technology offers specific advantages and is suited to different applications and operational requirements.<\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"1024\" src=\"https:\/\/www.lecosinus.fr\/wp-content\/uploads\/2026\/09\/Which-transformer-should-you-choose.png\" alt=\"Diff\u00e9rence entre un transformateur sec et un transformateur \u00e0 huile\" class=\"wp-image-95627\" srcset=\"https:\/\/www.lecosinus.fr\/wp-content\/uploads\/2026\/09\/Which-transformer-should-you-choose.png 1200w, https:\/\/www.lecosinus.fr\/wp-content\/uploads\/2026\/09\/Which-transformer-should-you-choose-300x300.png 300w, https:\/\/www.lecosinus.fr\/wp-content\/uploads\/2026\/09\/Which-transformer-should-you-choose-1024x1024.png 1024w, https:\/\/www.lecosinus.fr\/wp-content\/uploads\/2026\/09\/Which-transformer-should-you-choose-150x150.png 150w, https:\/\/www.lecosinus.fr\/wp-content\/uploads\/2026\/09\/Which-transformer-should-you-choose-768x768.png 768w, https:\/\/www.lecosinus.fr\/wp-content\/uploads\/2026\/09\/Which-transformer-should-you-choose-12x12.png 12w, https:\/\/www.lecosinus.fr\/wp-content\/uploads\/2026\/09\/Which-transformer-should-you-choose-600x600.png 600w, https:\/\/www.lecosinus.fr\/wp-content\/uploads\/2026\/09\/Which-transformer-should-you-choose-100x100.png 100w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><\/figure>\n\n\n\n<h2 class=\"wp-block-heading\">Cast Resin Dry-Type Transformer: A Solution Well Suited for Indoor Installations<\/h2>\n\n\n\n<p class=\"wp-block-paragraph translation-block\">A <a href=\"https:\/\/www.lecosinus.fr\/en\/transformers\/mv-three-phase-dry-transformers\/\" data-type=\"link\" data-id=\"https:\/\/www.lecosinus.fr\/transformateurs\/mt-transformateurs-triphases-sec\/\" target=\"_self\"> dry-type transformer<\/a>  uses ambient air for cooling, and its windings are protected by an epoxy resin insulation system. This design provides several advantages, particularly when the transformer is installed inside a building.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Its main advantage is the absence of any dielectric liquid. As a result, there is no risk of oil leakage, which significantly reduces fire safety constraints and environmental protection requirements.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">This feature makes dry-type transformers suitable for installation in technical rooms integrated into buildings, public buildings <strong>(ERP \u2013 establishments open to the public)<\/strong>, high-rise buildings, as well as commercial and healthcare facilities.The transformer substation can therefore be located closer to the loads, reducing the length of low-voltage cables and limiting the associated energy losses.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Another key advantage is the relatively simple maintenance required. Apart from periodic cleaning and connection checks, maintenance operations are generally limited.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Precautions That Should Not Be Overlooked <\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Although dry-type transformers offer many advantages, they also require certain installation precautions.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The first consideration is the ventilation of the transformer room. All energy dissipated by the transformer must be evacuated through the surrounding air. Poor air circulation can quickly lead to an increase in temperature and trigger thermal protection devices.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The installation environment must also be carefully controlled. Although modern resin insulation systems provide excellent performance, factors such as constant humidity, water ingress, or conductive dust remain issues that must be monitored.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Finally, for an equivalent power rating, a dry-type transformer is generally larger than an oil-filled transformer, which may have an impact on the layout and space requirements of the electrical room.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Oil-Filled Transformer: The Preferred Solution for Demanding Environments<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">An <strong>oil-filled transformer<\/strong> uses a dielectric liquid to provide both electrical insulation and cooling for the windings.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">This technology is historically the most widely used solution in power distribution networks and high-power industrial installations. Its robustness makes it particularly suitable for outdoor applications and demanding environments.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Unlike dry-type transformers, oil-filled transformers perform very well in humid conditions, polluted atmospheres, and saline environments. This is why they are commonly found in outdoor substations, heavy industrial facilities, photovoltaic plants, and energy infrastructure.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The dielectric liquid also provides excellent cooling performance. Its thermal inertia allows the transformer to better withstand temporary overloads and helps limit temperature rise within the windings.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">From an economic perspective, oil-filled transformers are often more cost-effective for high-power applications, particularly above several <strong>megavolt-amperes (MVA).<\/strong><\/p>\n\n\n\n<h2 class=\"wp-block-heading\">A More Stringent Regulatory Framework<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">The performance advantages of oil-filled transformers are nevertheless accompanied by more demanding installation requirements.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The presence of a dielectric liquid generally requires the installation of a <strong>retention basin<\/strong> designed to collect the fluid in the event of a leak or accidental tank failure.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">When mineral oil is used, fire safety considerations must also be taken into account. Depending on the site configuration, this may require specific safety clearances or additional protection systems.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Finally, the higher weight of the equipment must be considered during the infrastructure design phase, particularly when sizing foundations and planning handling and installation operations.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><a href=\"https:\/\/www.lecosinus.fr\/en\/the-different-types-of-low-voltage-electrical-transformers-manufactured-by-le-cosinus\/\" data-type=\"link\" data-id=\"https:\/\/www.lecosinus.fr\/les-differents-types-de-transformateurs-electriques-bt-bt-produits-chez-le-cosinus\/\">Which Transformer Should You Choose? <\/a>?<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">There is no universal answer. The choice primarily depends on the installation context. \n\nA <strong>dry-type transformer<\/strong> is often preferred when fire safety, integration within a building, or ease of maintenance are key priorities.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Conversely, an <strong>oil-filled transformer<\/strong> is frequently the preferred solution for outdoor installations, harsh environments, or applications requiring high power ratings.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Beyond the transformer's technical specifications alone, the entire project must be considered, including the substation location, regulatory requirements, operating environment, installation costs, and maintenance strategy.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Comparative Summary for the Installer <\/h2>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><td><strong>Installation Criteria<\/strong><\/td><td><strong>Cast Resin Dry-Type Transformer<\/strong><\/td><td><strong>Oil-Filled Transformer<\/strong><\/td><\/tr><tr><td><strong>Ideal Location<\/strong><\/td><td>Indoor installations, public buildings (ERP), high-rise buildings (IGH)<\/td><td>Outdoor installations, heavy industry, power distribution networks<\/td><\/tr><tr><td><strong>Civil Engineering Requirements <\/strong><\/td><td>Simple installation (standard foundation slab)<\/td><td>More complex requirements (retention basin + surge protection required)<\/td><\/tr><tr><td><strong>Medium-Voltage Connection<\/strong><\/td><td>Direct connection to terminals or via separable connectors<\/td><td>Often via plug-in bushings or busbar connections<\/td><\/tr><tr><td><strong>On-Site Maintenance<\/strong><\/td><td>Dust removal and connection tightening checks<\/td><td>Oil analysis, leak monitoring, and pressure control<\/td><\/tr><tr><td><strong>Sensitivity to Overvoltages<\/strong><\/td><td>More sensitive (requires carefully selected and installed surge protection)<\/td><td>Excellent natural dielectric strength<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<div class=\"hs-cta-embed hs-cta-simple-placeholder hs-cta-embed-185420320831\" style=\"max-width:100%;max-height:100%;width:700px;height:239.53125px\" data-hubspot-wrapper-cta-id=\"185420320831\">\r\n  <a href=\"https:\/\/cta-service-cms2.hubspot.com\/web-interactives\/public\/v1\/track\/redirect?encryptedPayload=AVxigLJ%2B8uzXIlYd5F1Cg72GDEo4S1p9zzkqyLAlT3McWV%2BDNRWsrtcQFwhBihGlWDL3nSWdQscvugwJIEM%2Blo0sWyqvQjAIafWdESsEYmcGkml4PxESyXNVWWZLqCNHgrHd%2BIsg8qUJHAayrn2LojP7LZPyflwCywOPcg8taJdeZJCXxpOTHuE%3D&amp;webInteractiveContentId=185420320831&amp;portalId=48243687\" target=\"_blank\" rel=\"noopener\">\r\n    <img decoding=\"async\" alt=\"Demande de devis Saisissez votre r&eacute;f&eacute;rence produit ou indiquer les caract&eacute;ristiques du produit recherch&eacute; &nbsp;\" loading=\"lazy\" src=\"https:\/\/no-cache.hubspot.com\/cta\/default\/48243687\/interactive-185420320831.png\" style=\"height: 100%;width: 100%;object-fit: fill\" \/>\r\n  <\/a>\r\n<\/div>","protected":false},"excerpt":{"rendered":"<p>Lorsqu&rsquo;il s&rsquo;agit d&rsquo;\u00e9quiper un poste HTA, le choix du transformateur ne se r\u00e9sume pas \u00e0 une simple question de puissance. L&rsquo;environnement d&rsquo;installation, les contraintes de s\u00e9curit\u00e9, les exigences de maintenance ou encore les co\u00fbts d&rsquo;exploitation influencent directement la technologie \u00e0 privil\u00e9gier. Les deux solutions les plus r\u00e9pandues sont le transformateur sec enrob\u00e9 et le transformateur [&hellip;]<\/p>\n","protected":false},"author":4387,"featured_media":95627,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"_seopress_titles_title":"Transformateur sec ou \u00e0 huile : lequel choisir pour votre installation HTA ? %%sep%% %%sitetitle%%","_seopress_titles_desc":"Comparez les transformateurs secs et \u00e0 huile : s\u00e9curit\u00e9, maintenance, installation et performances pour vos postes HTA.","_seopress_robots_index":"","_seopress_robots_follow":"","_seopress_robots_imageindex":"","_seopress_robots_snippet":"","_seopress_robots_primary_cat":"none","_seopress_robots_breadcrumbs":"","_seopress_robots_freeze_modified_date":"","_seopress_robots_custom_modified_date":"","_seopress_robots_canonical":"","_seopress_social_fb_title":"","_seopress_social_fb_desc":"","_seopress_social_fb_img":"","_seopress_social_fb_img_attachment_id":0,"_seopress_social_fb_img_width":0,"_seopress_social_fb_img_height":0,"_seopress_social_twitter_title":"","_seopress_social_twitter_desc":"","_seopress_social_twitter_img":"","_seopress_social_twitter_img_attachment_id":0,"_seopress_social_twitter_img_width":0,"_seopress_social_twitter_img_height":0,"_seopress_redirections_value":"","_seopress_redirections_enabled":"","_seopress_redirections_enabled_regex":"","_seopress_redirections_logged_status":"both","_seopress_redirections_param":"","_seopress_redirections_type":301,"_seopress_analysis_target_kw":"transformateurs sec,transformateur MT sec,transformateur sec,transformateurs secs","_seopress_news_disabled":"","_seopress_video_disabled":"","_seopress_video":[],"_seopress_pro_schemas_manual":[],"_seopress_pro_rich_snippets_disable_all":"","_seopress_pro_rich_snippets_disable":[],"_seopress_pro_schemas":[],"content-type":"","footnotes":""},"categories":[20],"tags":[],"class_list":["post-95611","post","type-post","status-publish","format-standard","has-post-thumbnail","category-guides-conseils"],"acf":[],"_links":{"self":[{"href":"https:\/\/www.lecosinus.fr\/en\/wp-json\/wp\/v2\/posts\/95611","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.lecosinus.fr\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.lecosinus.fr\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.lecosinus.fr\/en\/wp-json\/wp\/v2\/users\/4387"}],"replies":[{"embeddable":true,"href":"https:\/\/www.lecosinus.fr\/en\/wp-json\/wp\/v2\/comments?post=95611"}],"version-history":[{"count":16,"href":"https:\/\/www.lecosinus.fr\/en\/wp-json\/wp\/v2\/posts\/95611\/revisions"}],"predecessor-version":[{"id":96216,"href":"https:\/\/www.lecosinus.fr\/en\/wp-json\/wp\/v2\/posts\/95611\/revisions\/96216"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.lecosinus.fr\/en\/wp-json\/wp\/v2\/media\/95627"}],"wp:attachment":[{"href":"https:\/\/www.lecosinus.fr\/en\/wp-json\/wp\/v2\/media?parent=95611"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.lecosinus.fr\/en\/wp-json\/wp\/v2\/categories?post=95611"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.lecosinus.fr\/en\/wp-json\/wp\/v2\/tags?post=95611"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}