{"id":515,"date":"2020-03-09T22:00:12","date_gmt":"2020-03-09T14:00:12","guid":{"rendered":"http:\/\/powerquality.sg\/wordpress\/?p=515"},"modified":"2020-03-09T23:45:52","modified_gmt":"2020-03-09T15:45:52","slug":"mr-harmonics-ii","status":"publish","type":"post","link":"https:\/\/powerquality.sg\/wordpress\/?p=515","title":{"rendered":"Mr. Harmonics II"},"content":{"rendered":"\n<p>Harmonics gets people confused all the time. Some typical remarks will be like; <em>&#8220;the neutral current harmonics are extremely high&#8221; <\/em>or <em>&#8220;burnt marks on the isolator were caused by harmonics&#8221;.<\/em><\/p>\n\n\n\n<p>Here are 3 simple guidelines for harmonics in general LV applications.<\/p>\n\n\n\n<ol><li><strong>Keep Voltage THD% below &lt;5%<\/strong>. While there has been revisions in standards like IEEE-519 (revising upward from 5% to 8% for LV), trust me, keeping VTHD &lt; 5% will make life easier for everyone (utility, facilities dept and end-users).<\/li><li><strong>&#8220;Total harmonic content of the load current not exceeding 5% of rated current.&#8221;  <\/strong>This is stated as one of the normal service conditions for a standard distribution transformer. Thus, it is a good practice to keep the total current harmonics &lt; 5% of the transformer&#8217;s rated current (eg. 1MVA 22kV\/0.433kV TF &#8211; rated current 1333A; total harmonic current shall be less than 67A).<\/li><li><strong>Current THD% may gives you misleading results<\/strong> (see my other post &#8211; <a href=\"http:\/\/powerquality.sg\/wordpress\/?p=290\">Mr. Harmonics I<\/a>). One needs to see the actual current harmonics in absolute terms (amperes), total RMS current and make reference to the corresponding cable \/ circuit breaker sizes, before deciding on the next course of action.<\/li><\/ol>\n\n\n\n<p><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Harmonics gets people confused all the time. Some typical remarks will be like; &#8220;the neutral current harmonics are extremely high&#8221; or &#8220;burnt marks on the isolator were caused by harmonics&#8221;. Here are 3 simple guidelines for harmonics in general LV applications. Keep Voltage THD% below &lt;5%. While there has been revisions in standards like IEEE-519 [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":522,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_newsletter_tier_id":0,"jetpack_publicize_message":"","jetpack_is_tweetstorm":false,"jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","enabled":false}}},"categories":[5],"tags":[],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"https:\/\/powerquality.sg\/wordpress\/wp-content\/uploads\/2020\/03\/harmonics2.png","jetpack_shortlink":"https:\/\/wp.me\/p41TEZ-8j","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/powerquality.sg\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/515"}],"collection":[{"href":"https:\/\/powerquality.sg\/wordpress\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/powerquality.sg\/wordpress\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/powerquality.sg\/wordpress\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/powerquality.sg\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=515"}],"version-history":[{"count":6,"href":"https:\/\/powerquality.sg\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/515\/revisions"}],"predecessor-version":[{"id":524,"href":"https:\/\/powerquality.sg\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/515\/revisions\/524"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/powerquality.sg\/wordpress\/index.php?rest_route=\/wp\/v2\/media\/522"}],"wp:attachment":[{"href":"https:\/\/powerquality.sg\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=515"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/powerquality.sg\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=515"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/powerquality.sg\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=515"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}