{"id":4433,"date":"2025-03-05T14:48:06","date_gmt":"2025-03-05T09:18:06","guid":{"rendered":"https:\/\/study.madeeasy.in\/?p=4433"},"modified":"2025-07-16T13:32:20","modified_gmt":"2025-07-16T08:02:20","slug":"principle-circuit-breaker","status":"publish","type":"post","link":"https:\/\/www.madeeasy.in\/study\/ee\/power-generation-concepts\/principle-circuit-breaker","title":{"rendered":"Operating Principle of a Circuit Breaker (CB)"},"content":{"rendered":"<p style=\"text-align: justify;\">A circuit breaker consists of two contacts namely \u201cfixed\u201d and \u201cmoving contacts\u201d which touches each other under normal condition i.e. when circuit breaker is closed. Whenever a fault occurs, the trip coils get energized, the moving contacts get pulled by some mechanism and therefore, the circuit breaker is opened and the circuit is broken.<\/p>\n<h2 style=\"text-align: justify;\">Initiation of Arc<\/h2>\n<p style=\"text-align: justify;\">When the moving contacts of a C.B. begins to part, the heavy current passes through the gap causing a small voltage drop. A small separation of contacts does not cause immediate interruption of current because as the contact separate, the resistance between them increases and a lot of heat is produced due to the ohmic loss.<br \/>\nThis heat is sufficient to ionize the air or vaporize and ionize the oil between the contacts. The ionized air or vapour acts as a conductor and thus the current remains uninterrupted across the low resistance arc produced. The potential difference between the contacts is quite small and is just sufficient to maintain the arc.<\/p>\n<p style=\"text-align: justify;\"><strong>Note:<\/strong><\/p>\n<ul style=\"text-align: justify;\">\n<li>When the flow of charge takes place in a dielectric medium then, it is called \u201carc\u201d.<\/li>\n<li>Arc in a circuit breaker is initiated due to \u201cfield emission process\u201d and is maintained due to \u201cthermionic emission (thermal ionisation)\u201d.<\/li>\n<li>Because of the random nature of ionisation process, the voltage has high frequency components which also contribute radio frequency noise.<\/li>\n<li>The heat of the arc causes the oil in circuit breaker to decompose and liberate gases which comprises of almost 70% hydrogen, 20-25%% acetylene and 5-10% others (methane and other hydrocarbons)<\/li>\n<\/ul>\n<h3 style=\"text-align: justify;\">Comparison between Circuit Breaker and Isolator\/Disconnecting Switch:<\/h3>\n<table class=\"table table-striped table-bordered table-condensed\" style=\"margin: 0 auto; width: 99%;\">\n<tbody>\n<tr>\n<th width=\"301\">Circuit Breaker<\/th>\n<th width=\"301\">Isolator\/Disconnecting Switch<\/th>\n<\/tr>\n<tr>\n<td style=\"text-align: center;\" width=\"301\">It can operate when the supply is on that means it is a no-load device. It can also operate when the supply is off.<\/td>\n<td style=\"text-align: center;\" width=\"301\">It can operate when the supply is off that means it is a off-load device.<\/td>\n<\/tr>\n<tr>\n<td style=\"text-align: center;\" width=\"301\">It can operate automatically based on relay command.<\/td>\n<td style=\"text-align: center;\" width=\"301\">It can not operate automatically.<\/td>\n<\/tr>\n<tr>\n<td style=\"text-align: center;\" width=\"301\">It is provided with insulation medium like SF gas or oil or vacuum.<\/td>\n<td style=\"text-align: center;\" width=\"301\">It does not have any insulating medium.<\/td>\n<\/tr>\n<tr>\n<td style=\"text-align: center;\" width=\"301\">There is no earth switch provided with circuit breaker.<\/td>\n<td style=\"text-align: center;\" width=\"301\">Single or double earth switch can be provided with disconnector.<\/td>\n<\/tr>\n<tr>\n<td style=\"text-align: center;\" width=\"301\">It is used to protect circuit from the fault current.<\/td>\n<td style=\"text-align: center;\" width=\"301\">It is used to disconnect or isolate part of system for maintenance purpose.<\/td>\n<\/tr>\n<tr>\n<td style=\"text-align: center;\" width=\"301\">CB should always operate before isolator.<\/td>\n<td style=\"text-align: center;\" width=\"301\">It should always operate after CB.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p style=\"text-align: center;\"><a class=\"btn btn-danger\" role=\"button\" href=\"https:\/\/study.madeeasy.in\/ee\/power-generation-concepts\/power-system-protection\/\" target=\"_blank\" rel=\"noopener\">&lt;&lt; Previous<\/a> | <a class=\"btn btn-success\" role=\"button\" href=\"https:\/\/study.madeeasy.in\/ee\/power-generation-concepts\/types-of-circuit-breakers\/\" target=\"_blank\" rel=\"noopener\"> Next &gt;&gt;<\/a><br \/>\n<strong> Must Read: <\/strong> <a href=\"https:\/\/study.madeeasy.in\/subjects\/what-is-power-generation\/\" target=\"_blank\" rel=\"noopener\"><strong>What is Power Generation?<\/strong><\/a><\/p>\n","protected":false},"excerpt":{"rendered":"<p>A circuit breaker consists of two contacts namely \u201cfixed\u201d and \u201cmoving contacts\u201d which touches each other under normal condition i.e.<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1221,5],"tags":[1266,1277,1279,1278],"class_list":["post-4433","post","type-post","status-publish","format-standard","hentry","category-power-generation-concepts","category-ee","tag-circuit-breaker","tag-disconnecting-switch","tag-initiation-of-arc","tag-isolator"],"_links":{"self":[{"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/posts\/4433","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/comments?post=4433"}],"version-history":[{"count":0,"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/posts\/4433\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/media?parent=4433"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/categories?post=4433"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/tags?post=4433"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}