{"id":497,"date":"2017-01-16T05:45:39","date_gmt":"2017-01-16T05:45:39","guid":{"rendered":"http:\/\/cselectric.co.in\/blog\/?p=497"},"modified":"2026-10-07T06:12:56","modified_gmt":"2026-10-07T06:12:56","slug":"circuit-breakers-discrimination-and-its-techniques","status":"publish","type":"post","link":"https:\/\/cselectric.co.in\/blog\/circuit-breakers-discrimination-and-its-techniques\/","title":{"rendered":"Circuit Breakers- Discrimination and Its Techniques"},"content":{"rendered":"<div id=\"ez-toc-container\" class=\"ez-toc-v2_0_88 counter-hierarchy ez-toc-counter ez-toc-custom ez-toc-container-direction\">\n<div class=\"ez-toc-title-container\">\n<p class=\"ez-toc-title\" style=\"cursor:inherit\">Table of Contents<\/p>\n<span class=\"ez-toc-title-toggle\"><a href=\"#\" class=\"ez-toc-pull-right ez-toc-btn ez-toc-btn-xs ez-toc-btn-default ez-toc-toggle\" aria-label=\"Toggle Table of Content\"><span class=\"ez-toc-js-icon-con\"><span class=\"\"><span class=\"eztoc-hide\" style=\"display:none;\">Toggle<\/span><span class=\"ez-toc-icon-toggle-span\"><svg style=\"fill: #999;color:#999\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" class=\"list-377408\" width=\"20px\" height=\"20px\" viewBox=\"0 0 24 24\" fill=\"none\"><path d=\"M6 6H4v2h2V6zm14 0H8v2h12V6zM4 11h2v2H4v-2zm16 0H8v2h12v-2zM4 16h2v2H4v-2zm16 0H8v2h12v-2z\" fill=\"currentColor\"><\/path><\/svg><svg style=\"fill: #999;color:#999\" class=\"arrow-unsorted-368013\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"10px\" height=\"10px\" viewBox=\"0 0 24 24\" version=\"1.2\" baseProfile=\"tiny\"><path d=\"M18.2 9.3l-6.2-6.3-6.2 6.3c-.2.2-.3.4-.3.7s.1.5.3.7c.2.2.4.3.7.3h11c.3 0 .5-.1.7-.3.2-.2.3-.5.3-.7s-.1-.5-.3-.7zM5.8 14.7l6.2 6.3 6.2-6.3c.2-.2.3-.5.3-.7s-.1-.5-.3-.7c-.2-.2-.4-.3-.7-.3h-11c-.3 0-.5.1-.7.3-.2.2-.3.5-.3.7s.1.5.3.7z\"\/><\/svg><\/span><\/span><\/span><\/a><\/span><\/div>\n<nav><ul class='ez-toc-list ez-toc-list-level-1 ' ><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-1\" href=\"https:\/\/cselectric.co.in\/blog\/circuit-breakers-discrimination-and-its-techniques\/#Discrimination_as_per_IEC_60947-2_can_be_defined_as_follows\" >Discrimination as per IEC 60947-2 can be defined as follows:<\/a><ul class='ez-toc-list-level-3' ><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-2\" href=\"https:\/\/cselectric.co.in\/blog\/circuit-breakers-discrimination-and-its-techniques\/#1_The_total_discrimination\" >1. The total discrimination:<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-3\" href=\"https:\/\/cselectric.co.in\/blog\/circuit-breakers-discrimination-and-its-techniques\/#2_Partial_Discrimination\" >2. Partial Discrimination:<\/a><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-4\" href=\"https:\/\/cselectric.co.in\/blog\/circuit-breakers-discrimination-and-its-techniques\/#Principles_of_discriminative_tripping_selectivity\" >Principles of discriminative tripping (selectivity)<\/a><ul class='ez-toc-list-level-3' ><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-5\" href=\"https:\/\/cselectric.co.in\/blog\/circuit-breakers-discrimination-and-its-techniques\/#1_Protection_against_overload_discrimination_based_on_current_levels\" >1. Protection against overload: discrimination based on current levels<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-6\" href=\"https:\/\/cselectric.co.in\/blog\/circuit-breakers-discrimination-and-its-techniques\/#2_Protection_against_low_level_short-circuit_currents_discrimination_based_on_stepped_time_delays\" >2. Protection against low level short-circuit currents: discrimination based on stepped time delays<\/a><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-7\" href=\"https:\/\/cselectric.co.in\/blog\/circuit-breakers-discrimination-and-its-techniques\/#Current-level_discrimination_%E2%80%93_Principle\" >Current-level discrimination &#8211; Principle<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-8\" href=\"https:\/\/cselectric.co.in\/blog\/circuit-breakers-discrimination-and-its-techniques\/#Time-based_discrimination-_Principle\" >Time-based discrimination- Principle<\/a><\/li><\/ul><\/nav><\/div>\n<div class=\"wpb-content-wrapper\" id=\"wpb-content-root\"><p>[vc_row][vc_column][vc_column_text]A circuit breaker is a switching device which can be operated manually and automatically for control and protection of electrical power circuit.<br \/>\nThe primary purpose of a <a href=\"https:\/\/cselectric.co.in\/products-solutions\/low-voltage-switchgear\/circuit-breakers\/air-circuit-breakers\/\">circuit breaker<\/a> is to protect the system from the damage in series connected equipment &amp; to minimize the area of damage and to minimum duration of power loss. However the first consideration in the discrimination is the correct circuit sizing breaker of main and branch breaker.<br \/>\nDiscrimination is the coordination between the operating characteristics of circuit breakers placed in series. When the fault occurs in system only the circuit breaker placed immediately upstream of the fault will trip.[\/vc_column_text]<aside class=\"gap cf\" style=\"height:20px;\"><\/aside>[vc_column_text]<\/p>\n<h2><span class=\"ez-toc-section\" id=\"Discrimination_as_per_IEC_60947-2_can_be_defined_as_follows\"><\/span>Discrimination as per IEC 60947-2 can be defined as follows:<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<h3><span class=\"ez-toc-section\" id=\"1_The_total_discrimination\"><\/span>1. The total discrimination:<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>This is a type of current based discrimination where in there are two circuit breakers in series, the circuit breaker on the load side effects the protection without causing the upstream circuit breaker to operate\/trip<\/p>\n<h3><span class=\"ez-toc-section\" id=\"2_Partial_Discrimination\"><\/span>2. Partial Discrimination:<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>This is a type of current based discrimination where in there are two circuit breakers in series, the circuit breaker on the load side effects the protection up to a defined level of overcurrent, without causing the upstream circuit breaker to operate\/trip.[\/vc_column_text]<aside class=\"gap cf\" style=\"height:20px;\"><\/aside>[vc_column_text]<\/p>\n<h2><span class=\"ez-toc-section\" id=\"Principles_of_discriminative_tripping_selectivity\"><\/span>Principles of discriminative tripping (selectivity)<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>Discrimination may be total or partial, and based on the principles of current levels, or time-delays, or a combination of both. A more recent development is based on the logic techniques Discrimination is achieved by automatic protective devices if a fault condition, occurring at any point in the installation, is cleared by the protective device located immediately Upstream of the fault, while all other protective devices remain unaffected.<\/p>\n<h3><span class=\"ez-toc-section\" id=\"1_Protection_against_overload_discrimination_based_on_current_levels\"><\/span>1. Protection against overload: discrimination based on current levels<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>This method is realized by setting successive tripping thresholds at stepped levels, from downstream relays (lower settings) towards the source (higher settings). Discrimination is total or partial, depending on particular conditions, as noted above.<\/p>\n<h3><span class=\"ez-toc-section\" id=\"2_Protection_against_low_level_short-circuit_currents_discrimination_based_on_stepped_time_delays\"><\/span>2. Protection against low level short-circuit currents: discrimination based on stepped time delays<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>This method is implemented by adjusting the time-delayed tripping units, such that downstream circuit breakers have the shortest operating times, with progressively longer delays towards the source.[\/vc_column_text]<aside class=\"gap cf\" style=\"height:20px;\"><\/aside>[vc_column_text]<\/p>\n<h2><span class=\"ez-toc-section\" id=\"Current-level_discrimination_%E2%80%93_Principle\"><\/span>Current-level discrimination &#8211; Principle<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>Current-level discrimination is achieved with stepped current-level settings of the instantaneous magnetic-trip elements. Current-level discrimination is achieved with circuit breakers, preferably current limiting, and stepped current-level settings of the instantaneous magnetic-trip elements.<br \/>\nThe downstream circuit-breaker is not a current-limiter device<br \/>\nTotal discrimination in this situation is practically impossible because<br \/>\nIsc A \u2248 Isc B, so that both circuit-breakers will generally trip simultaneously. In this case discrimination is partial, and limited to the Im of the upstream circuit-breaker.<br \/>\nThe downstream circuit-breaker is a current-limiting device. Improvement in discriminative tripping can be obtained by using a current limiter for circuit-breaker B. For a short-circuit downstream of B, the limited level of peak current IB would operate the (suitably adjusted) magnetic trip unit of B, but would be insufficient to cause circuit-breaker A to trip.[\/vc_column_text]<aside class=\"gap cf\" style=\"height:20px;\"><\/aside>[vc_column_text]<\/p>\n<h2><span class=\"ez-toc-section\" id=\"Time-based_discrimination-_Principle\"><\/span>Time-based discrimination- Principle<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p><strong>This technique requires:<\/strong><\/p>\n<p>The introduction of time-delays into the tripping mechanisms of circuit breakers<br \/>\nCircuit Breakers with adequate thermal and mechanical withstand capabilities at the high current levels and time delays considered Two circuit-breakers A and B in series (i.e. carrying the same current) are discriminative if the current-breaking period of downstream circuit-breaker B is less than the non-tripping time of circuit-breaker A<br \/>\nC&amp;S offers total discrimination up to fault level of 50kA. For total discrimination, the customers can select <a href=\"https:\/\/cselectric.co.in\/products-solutions\/low-voltage-switchgear\/circuit-breakers\/air-circuit-breakers\/winmaster2-power-circuit-breakers\/\">Winmaster2 Air Circuit Breakers<\/a> (ACBs) &amp; Winbreak2 Molded Case Circuit Breakers (MCCBs). Customers can refer selection of up- stream and down-steam breaker details (kA, Rating &amp; AF) from the selection tables provided by C&amp;S Electric.[\/vc_column_text][\/vc_column][\/vc_row]<\/p>\n<\/div>","protected":false},"excerpt":{"rendered":"<p>[vc_row][vc_column][vc_column_text]A circuit breaker is a switching device which can be operated manually and automatically for control and protection of electrical power circuit. The primary purpose of a circuit breaker is to protect the system from the damage in series connected equipment &amp; to minimize the area of damage and to minimum duration of power loss.&hellip;<\/p>\n","protected":false},"author":1,"featured_media":512,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[251],"tags":[],"class_list":["post-497","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-knowledge"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v28.6 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>Circuit Breaker: Techniques and its Principle - C&amp;S Electric<\/title>\n<meta name=\"description\" content=\"Learn circuit breaker discrimination, including total and partial discrimination, current-level and time-based selectivity, and fault protection techniques.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/cselectric.co.in\/blog\/circuit-breakers-discrimination-and-its-techniques\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Circuit Breaker: Techniques and its Principle - C&amp;S Electric\" \/>\n<meta property=\"og:description\" content=\"A circuit breaker stops the current flow in an electric circuit as a safety measure. Read more techniques and principles about circuit breakers at C&amp;S Electric.\" \/>\n<meta property=\"og:url\" content=\"https:\/\/cselectric.co.in\/blog\/circuit-breakers-discrimination-and-its-techniques\/\" \/>\n<meta property=\"og:site_name\" content=\"C&amp;S Electric Blog\" \/>\n<meta property=\"article:published_time\" content=\"2017-01-16T05:45:39+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2026-10-07T06:12:56+00:00\" \/>\n<meta property=\"og:image\" content=\"https:\/\/cselectric.co.in\/blog\/wp-content\/uploads\/2017\/01\/circuit_breaker.jpg\" \/>\n\t<meta property=\"og:image:width\" content=\"800\" \/>\n\t<meta property=\"og:image:height\" content=\"357\" \/>\n\t<meta property=\"og:image:type\" content=\"image\/jpeg\" \/>\n<meta name=\"author\" content=\"C&amp;S Electric\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:title\" content=\"Circuit Breaker: Techniques and its Principle - C&amp;S Electric\" \/>\n<meta name=\"twitter:description\" content=\"A circuit breaker stops the current flow in an electric circuit as a safety measure. 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