{"id":138,"date":"2013-10-31T23:56:48","date_gmt":"2013-10-31T15:56:48","guid":{"rendered":"http:\/\/powerquality.sg\/wordpress\/?p=138"},"modified":"2014-11-09T14:20:45","modified_gmt":"2014-11-09T06:20:45","slug":"back-to-basics-what-is-voltage-dip","status":"publish","type":"post","link":"https:\/\/powerquality.sg\/wordpress\/?p=138","title":{"rendered":"Back to Basics – What is Voltage Dip?"},"content":{"rendered":"

Definition: Temporary reduction of the r.m.s voltage at a point in the electrical system below 90% threshold of the declared nominal voltage, between 10ms and up to a minute.<\/p>\n

\"Voltage<\/a>
Voltage Dip (RMS Trend)<\/figcaption><\/figure>\n

Simply speaking, a sudden voltage drop of more than 10% of the declared nominal voltage. The utility in Singapore has in place a Power Quality Monitoring System (PQMS) from 22kV voltage level upwards (all the way to 400kV). These are three-wire three phase systems; and hence line to line voltages are used in defining a dip.<\/p>\n

There is a significance of such definition being used in the 66kV and 22kV networks, whereby it is a resistively earthed grounded system (thru the neutral ground resistor). Here, a single phase fault will not be a registered as a voltage dip as the other two non-faulted phases will swell; ‘compensating’ the faulted phase. This will result in a drop of voltage (line to line) of usually less than 10% (hence not a dip). The utility here described such events as ‘Voltage variation’.<\/p>\n

Two things matter when it comes to describing a voltage dip.
\n1) Magnitude of the dip<\/strong>
\nThis typically reflects the fault severity and also the proximity of the monitoring point to the fault location.
\n2) Duration
\n<\/strong>The timer starts when the voltage falls below the 90% threshold and ends when all voltages are equal to or above the 90% threshold. This is very much dependent on the time taken to isolate the fault and the nature of loads connected.<\/p>\n

Normally a voltage dip here in Singapore will lasts less than 200ms (10 cycles). This is about the average time the primary protection takes to isolate the fault from the network.
\nUsually a longer duration will suggest a somewhat sluggish protection relay operation.<\/p>\n

Typical causes of a voltage dip in Singapore:
\n1) Equipment \/ cable faults in the utility network.
\n2) Equipment \/ transmission line faults in Tenaga Nasional Berhad (TNB) network (Singapore is connected to Malaysia at 230kV).
\n3) Customer Installation faults.
\n4) Cable damage by earthworks.
\n5) And to a very small extent, load switching like motor starting.<\/p>\n

Singapore’s electricity regulator, the Energy Market Authority (EMA) publishes cases of voltage dips on its website.<\/a><\/p>\n

\"Dip<\/a>
Dip due to a customer installation fault<\/figcaption><\/figure>\n","protected":false},"excerpt":{"rendered":"

Definition: Temporary reduction of the r.m.s voltage at a point in the electrical system below 90% threshold of the declared nominal voltage, between 10ms and up to a minute. Simply speaking, a sudden voltage drop of more than 10% of the declared nominal voltage. The utility in Singapore has in place a Power Quality Monitoring […]<\/p>\n","protected":false},"author":1,"featured_media":0,"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":[9,10],"tags":[],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_shortlink":"https:\/\/wp.me\/p41TEZ-2e","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/powerquality.sg\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/138"}],"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=138"}],"version-history":[{"count":10,"href":"https:\/\/powerquality.sg\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/138\/revisions"}],"predecessor-version":[{"id":288,"href":"https:\/\/powerquality.sg\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/138\/revisions\/288"}],"wp:attachment":[{"href":"https:\/\/powerquality.sg\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=138"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/powerquality.sg\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=138"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/powerquality.sg\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=138"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}