{"id":127,"date":"2013-10-30T18:35:56","date_gmt":"2013-10-30T10:35:56","guid":{"rendered":"http:\/\/powerquality.sg\/wordpress\/?p=127"},"modified":"2014-01-02T10:12:51","modified_gmt":"2014-01-02T02:12:51","slug":"voltage-dip-30-october-2013-1418hrs","status":"publish","type":"post","link":"http:\/\/powerquality.sg\/wordpress\/?p=127","title":{"rendered":"Voltage Dip 30 October 2013 @ 1418hrs"},"content":{"rendered":"

Earlier today, at about 2 plus in the afternoon, you might have noticed your office lights flickered, the escalators came to a standstill or that the chillers had tripped.
\nEnough clues to guess what could have been the cause?<\/p>\n

Yes, you guessed it right. There was a transmission level fault, hence causing an islandwide voltage dip.<\/p>\n

Here, in Singapore. a voltage dip is defined as a drop of more than 10% of the nominal voltage (Line voltage). It typically lasts around 200ms.<\/p>\n

In Singapore, the transmission network consists of a 400kV network, overlayed onto 4 x 230kV blocks. The 230kV blocks were split up in the mid 2000s, for controlling of fault level.
\nIt has inherently brought an advantage: Minimize the impact of a voltage dip due to a 230kV transmission fault to just that particular block.<\/p>\n

Hence in a 230kV fault, only connected customers in that particular block which the fault occurred will ‘see’ severe dip values (in the ranges of 40-50% dip by magnitude); Customers in the lower voltage levels (66kV, 22kV etc) of that block will see similar (as seen at 230kV) dip severity or less (slightly). The other 3 blocks will see significantly less severe voltage dip or just a slight variation of the nominal voltage.<\/p>\n

This is what happened earlier. Below is the 22kV (Line to Line) voltage dip snapshot, captured from one of the monitoring sites in the western part of Singapore.<\/p>\n

\"22kV<\/a>
22kV Voltage Dip Waveform 30-10-2013 1413hrs<\/figcaption><\/figure>\n

Monitoring sites in other parts of Singapore also registered similar dip patterns, suggesting a transmission level fault.
\nThis brings me to the conclusion that<\/p>\n

1) This was a 230kV single phase fault on the L3 (Blue phase) in the western part of Singapore.
\nUPDATE 31\/10: Official Letter from SP PowerAssets: 230kV Cable damage – between Tuas Substation and Jurong Pier Substation at about 2:13 PM, 30\/10\/2013.<\/strong><\/span><\/p>\n

2) An L3 fault occurred. This affected V23 and V31 significantly. Hence you can notice both V23 and V31 ‘dropped’.<\/p>\n

Singapore’s 230kv\u00a0 network is solidly grounded; hence any single phase fault will cause the other two non-faulted phases to ‘drop’ slightly too. This is unlike in a resistive earthed grounded system, (thru the Neutral Ground resistor) where the other two non-faulted phases will swell.<\/p>\n

Here it also shows the advantages of having a power quality monitoring system installed. With both voltage and current waveforms recorded during a dip, it will assist the experienced engineer in analyzing whether the drop in voltage was caused by a fault downstream (internal fault) or originated from the grid (external fault); and hence assist him in quicken the restoration time for equipment that could have tripped due to the voltage dip.<\/p>\n","protected":false},"excerpt":{"rendered":"

Earlier today, at about 2 plus in the afternoon, you might have noticed your office lights flickered, the escalators came to a standstill or that the chillers had tripped. Enough clues to guess what could have been the cause? Yes, you guessed it right. There was a transmission level fault, hence causing an islandwide voltage […]<\/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":[10],"tags":[],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_shortlink":"https:\/\/wp.me\/p41TEZ-23","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"http:\/\/powerquality.sg\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/127"}],"collection":[{"href":"http:\/\/powerquality.sg\/wordpress\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/powerquality.sg\/wordpress\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/powerquality.sg\/wordpress\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/powerquality.sg\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=127"}],"version-history":[{"count":12,"href":"http:\/\/powerquality.sg\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/127\/revisions"}],"predecessor-version":[{"id":134,"href":"http:\/\/powerquality.sg\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/127\/revisions\/134"}],"wp:attachment":[{"href":"http:\/\/powerquality.sg\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=127"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/powerquality.sg\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=127"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/powerquality.sg\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=127"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}