{"id":6120,"date":"2026-09-06T13:56:02","date_gmt":"2026-09-06T10:56:02","guid":{"rendered":"https:\/\/aesinn.com\/trafo-ve-guc-sistemleri\/ieee-c57-referansli-guc-trafosu-elektriksel-test-protokolu-donusturme-orani-sargi-direnci-tan-delta-ve-sfra\/"},"modified":"2026-09-06T13:57:15","modified_gmt":"2026-09-06T10:57:15","slug":"ieee-c57-referansli-guc-trafosu-elektriksel-test-protokolu-donusturme-orani-sargi-direnci-tan-delta-ve-sfra","status":"publish","type":"page","link":"https:\/\/aesinn.com\/en\/trafo-ve-guc-sistemleri\/ieee-c57-referansli-guc-trafosu-elektriksel-test-protokolu-donusturme-orani-sargi-direnci-tan-delta-ve-sfra\/","title":{"rendered":"IEEE C57 Electrical Test Protocol for Power Transformers: Transform Ratio, Winding Resistance, Tan Delta, and SFRA"},"content":{"rendered":"<h2 class=\"wp-block-heading\">What is the IEEE C57 Standard Family?<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">IEEE C57 is an internationally recognized family of standards developed for the design, manufacture, acceptance, and field testing of power and distribution transformers. Within the family, different documents serve different purposes; two stand out in terms of transformer testing.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">IEEE C57.12.90 defines the test methods (test code) applied during the factory and acceptance phases for liquid-insulated distribution and power transformers. IEEE C57.152-2013 is a guide for diagnostic testing performed in the field throughout the service life; it covers the measurements and interpretation approaches applied to liquid-filled power transformers, regulators, and reactors.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">These two documents complement each other: C57.12.90 standardizes test procedures, while C57.152 describes how the same tests can be applied in the field for diagnostic purposes and how the results should be evaluated together. The guidance emphasizes that acceptance criteria should not be interpreted in isolation, but rather the tests as a whole.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Transformer Electrical Test Protocol<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">The following tests are electrical evaluations of the transformer&#039;s active part (core and windings) and winding insulation. This page addresses the electrical\/mechanical integrity of the transformer, distinct from transformer oil analysis; oil and dissolved gas analysis is a separate and complementary topic (see our Transformer Oil Test page).<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n\n<li>Turns ratio test (TTR): Measures the actual winding ratio between the primary and secondary windings and compares it to the label value. Deviation may indicate a short circuit winding, open circuit, or tap problem.<\/li>\n\n\n<li>Winding resistance measurement: Measures the DC resistance of each winding with high accuracy. Imbalances between windings or deviations from the expected value can reveal loose connections, tap changer contact problems, or conductor damage.<\/li>\n\n\n<li>Insulation resistance and polarization index: Measures the resistance of insulation between windings and ground, and between windings. The polarization index evaluates the moisture and contamination status of the insulation based on the resistance ratio over specific periods.<\/li>\n\n\n<li>Power factor\/tan delta (insulation loss angle) test: Measures the dielectric losses of insulation. Increasing values are an early indicator of moisture, aging, contamination, or insulation degradation. Bushing (bust insulator) power factor can also be evaluated within this scope.<\/li>\n\n\n<li>Leakage reactance\/short-circuit impedance: Sensitive to winding geometry. Deviation of the measured value from the reference may indicate winding deformation or displacement.<\/li>\n\n\n<li>Magnetization (excitation) current test: The current drawn is measured by applying a low voltage. Phase-to-phase abnormalities may indicate core problems, short-circuited windings, or tap changer problems.<\/li>\n\n\n<li>SFRA (Sweep Frequency Response Analysis): By applying low-voltage signals at different frequencies to the windings, the transfer function (frequency fingerprint) is obtained. By comparing this to a reference curve, winding deformation, displacement, short-circuit winding, core movement, and mechanical loosening can be detected before the transformer is switched on.<\/li>\n\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\">Which test detects which fault?<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">The power of electrical tests becomes apparent when they are interpreted together. No single test provides a definitive diagnosis; cross-referencing the results increases reliability.<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n\n<li>Coil deformation\/displacement: Primarily detected by SFRA and leakage reactance tests; deviations in both tests strengthen the diagnosis.<\/li>\n\n\n<li>Shorted turns: Can be seen together in conversion ratio, magnetization current, and SFRA results.<\/li>\n\n\n<li>Connection and contact problems (including tap changer): These are clearly revealed by winding resistance measurement.<\/li>\n\n\n<li>Insulation degradation, moisture, and aging: Evaluated using power factor\/tan delta, insulation resistance, and polarization index.<\/li>\n\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\">Commissioning and Periodic Testing Context<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">These tests are applied in two main contexts. During the commissioning phase, the initial condition is recorded before the transformer is energized; these values form a reference (fingerprint) for future comparisons. In tests such as SFRA, the existence of a reference curve directly determines the accuracy of subsequent evaluations.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">In the context of periodic testing, measurements are repeated at specific intervals throughout the transformer&#039;s service life, and the change (trend) of the values over time is monitored. Verification tests can also be performed after a sudden event (e.g., a near-miss short circuit, after transport). Trend tracking is often more informative than one-time absolute values.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Legislative Context in T\u00fcrkiye<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">In T\u00fcrkiye, the safe operation and periodic inspection of equipment used in high-voltage electrical installations are regulated by legislation. The High-Voltage Electrical Installations Regulation sets out the principles for the installation and operation of these installations.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">According to the Regulation on Health and Safety Requirements in the Use of Work Equipment (first published in the Official Gazette dated 25.04.2013 and numbered 28628; updated in the Official Gazette dated 23.12.2025 and numbered 33116), periodic inspections of work equipment are mandatory. Within this framework, transformers can also be considered among the equipment subject to periodic inspection.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">IEEE C57 is an international technical reference for measurement and evaluation methods, not a replacement for legislation. The legal obligation for periodic inspections and the technical test information referenced in IEEE C57 are different matters; which inspection falls under which legislation and the authorization status should always be confirmed through the relevant legislation and the competent authority.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">The Relationship Between Oil Testing and Holistic Transformer Health<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Electrical tests reveal the mechanical\/electrical condition of the transformer&#039;s active part and winding insulation. Transformer oil and dissolved gas analysis (DGA), along with moisture and dielectric oil measurements, offer a different perspective through the insulating fluid; they look for signs of phenomena such as internal heating, arcing, and partial discharge in the oil.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The two approaches complement each other: evaluating electrical tests and oil\/DGA results together provides a more complete picture of the transformer&#039;s health. This page only covers the electrical testing protocol; for oil and DGA issues, please see our Transformer Oil Test page, and for field inspections, please see our Transformer and Power Systems Inspections page. Thermography (thermal imaging) is also covered under a separate heading.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Information Note<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">This page is for informational purposes only and aims to provide a general overview of the electrical test methods for power transformers in the IEEE C57 family. The scope of testing, methodology, and interpretation of results for any transformer should be evaluated by a qualified engineer (electrical engineer) based on the equipment type, manufacturer data, and site conditions.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">AES Innovation can provide authorized engineer technical reports with IEEE C57 referenced technical evaluation and test information within the scope of its electrical expertise. AES&#039;s T\u00dcRKAK accreditation scope only covers the 6.1 Electrical Installation area; specific transformer electrical tests under IEEE C57 are not included in this accreditation. There is no claim of accreditation, certification, or accreditation in this area; the exact scope and authorization status must be confirmed separately upon request.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Related Services<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n\n<li><a href=\"https:\/\/aesinn.com\/en\/hesaplama-araclari\/trafo-sogutma-yag-degerlendirme\/\">Transformer Oil Test \/ Thermography Evaluation<\/a><\/li>\n\n\n<li><a href=\"https:\/\/aesinn.com\/en\/test-ve-olcum-hizmetleri\/termografik-kamera-ile-sicaklik-olcumu\/\">Temperature Measurement with a Thermographic Camera<\/a><\/li>\n\n\n<li><a href=\"https:\/\/aesinn.com\/en\/trafo-ve-guc-sistemleri\/orta-ve-yuksek-gerilim-salt-tesisi-hucre-periyodik-kontrolu\/\">Periodic Inspection of Medium and High Voltage Switchgear<\/a><\/li>\n\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\">Frequently Asked Questions<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\">What is IEEE C57?<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">IEEE C57 is an international family of standards for power and distribution transformers. IEEE C57.12.90 defines the factory\/acceptance test code, while IEEE C57.152-2013 defines the diagnostic test guide applied in the field. It is widely referenced in transformer electrical testing.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">What is the purpose of the SFRA test?<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">SFRA (sweep frequency response analysis) extracts a frequency fingerprint of a transformer by applying low-voltage signals at different frequencies to the windings. By comparing this to a reference curve, mechanical problems such as winding deformation, displacement, short-circuiting, and core movement can be detected before the transformer is switched on.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">How do these tests differ from transformer oil tests?<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Electrical tests measure the electrical\/mechanical condition of the transformer&#039;s active section and winding insulation (e.g., transformation ratio, winding resistance, tan delta, SFRA). Oil testing and DGA offer a different diagnostic window through the insulating oil. The two complement each other and together provide a more holistic picture of the transformer&#039;s health.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">When are these tests performed?<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">This is typically done during the commissioning phase to record initial reference values, and then periodically throughout the service life to monitor trends. It can also be applied for verification purposes after events such as near-misses or transportation incidents.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Are periodic transformer inspections mandatory in T\u00fcrkiye?<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">The Regulation on Health and Safety Requirements in the Use of Work Equipment mandates periodic inspections of work equipment, and transformers can be evaluated within this framework. The Regulation on High Voltage Electrical Installations also sets out the relevant principles. IEEE C57 is an international technical reference for measurement methods that does not replace legal obligations; its scope should always be confirmed with current legislation.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Does AES conduct these tests?<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">AES Innovation can provide IEEE C57 referenced technical evaluation, test information, and authorized engineer technical reports within the scope of its electrical expertise. However, AES&#039;s T\u00dcRKAK accreditation is only for the 6.1 Electrical Installation category; IEEE C57 specific transformer electrical tests are not covered by this accreditation.<\/p>","protected":false},"excerpt":{"rendered":"<p>G\u00fc\u00e7 trafolar\u0131n\u0131n aktif k\u0131sm\u0131 ve sarg\u0131 yal\u0131t\u0131m\u0131n\u0131n sa\u011fl\u0131\u011f\u0131n\u0131 de\u011ferlendiren elektriksel test protokol\u00fc; d\u00f6n\u00fc\u015ft\u00fcrme oran\u0131 (TTR), sarg\u0131 direnci, tan delta ve sweep frekans yan\u0131t analizi (SFRA) testlerinin ne i\u015fe yarad\u0131\u011f\u0131na dair IEEE C57 referansl\u0131 bilgilendirici bir rehber.<\/p>","protected":false},"author":1,"featured_media":6124,"parent":2527,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_acf_changed":false,"_kad_blocks_custom_css":"","_kad_blocks_head_custom_js":"","_kad_blocks_body_custom_js":"","_kad_blocks_footer_custom_js":"","_kadence_starter_templates_imported_post":false,"_kad_post_transparent":"","_kad_post_title":"","_kad_post_layout":"","_kad_post_sidebar_id":"","_kad_post_content_style":"","_kad_post_vertical_padding":"","_kad_post_feature":"","_kad_post_feature_position":"","_kad_post_header":false,"_kad_post_footer":false,"_kad_post_classname":"","slim_seo":{"title":"IEEE C57 Power Transformer Electrical Test Protocol","description":"IEEE C57 reference power transformer electrical tests: transformation ratio, winding resistance, tan delta, and SFRA. Informative technical guide."},"_pplb_hide_from_list":false,"footnotes":""},"class_list":["post-6120","page","type-page","status-publish","has-post-thumbnail","hentry"],"acf":[],"taxonomy_info":[],"featured_image_src_large":["https:\/\/aesinn.com\/wp-content\/uploads\/aes-ieee-c57-2026-1024x1024.png",1024,1024,true],"author_info":{"display_name":"Emre Metin","author_link":"https:\/\/aesinn.com\/en\/author\/yonetim\/"},"comment_info":"","_hostinger_reach_plugin_has_subscription_block":false,"_hostinger_reach_plugin_is_elementor":false,"_links":{"self":[{"href":"https:\/\/aesinn.com\/en\/wp-json\/wp\/v2\/pages\/6120","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/aesinn.com\/en\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/aesinn.com\/en\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/aesinn.com\/en\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/aesinn.com\/en\/wp-json\/wp\/v2\/comments?post=6120"}],"version-history":[{"count":2,"href":"https:\/\/aesinn.com\/en\/wp-json\/wp\/v2\/pages\/6120\/revisions"}],"predecessor-version":[{"id":6129,"href":"https:\/\/aesinn.com\/en\/wp-json\/wp\/v2\/pages\/6120\/revisions\/6129"}],"up":[{"embeddable":true,"href":"https:\/\/aesinn.com\/en\/wp-json\/wp\/v2\/pages\/2527"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/aesinn.com\/en\/wp-json\/wp\/v2\/media\/6124"}],"wp:attachment":[{"href":"https:\/\/aesinn.com\/en\/wp-json\/wp\/v2\/media?parent=6120"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}