{"id":2881,"date":"2018-06-06T22:20:18","date_gmt":"2018-06-06T20:20:18","guid":{"rendered":"https:\/\/onload.reinhausen.com\/de\/?p=2815"},"modified":"2023-06-02T09:14:01","modified_gmt":"2023-06-02T07:14:01","slug":"keep-calm","status":"publish","type":"post","link":"https:\/\/onload.reinhausen.com\/en\/07-2018\/keep-calm\/","title":{"rendered":"Keep calm"},"content":{"rendered":"
\n

U<\/span>nless zad\u00addi\u00adtion\u00adal mea\u00adsures are in place, switch\u00ading on trans\u00adform\u00aders with\u00adout tim\u00ading con\u00adtrol always leads to prob\u00adlems, which can even be felt on a phys\u00adi\u00adcal level\u2014the air vibrates, ele\u00admen\u00adtary par\u00adti\u00adcles align, and a loud buzz can be heard. For the sup\u00adply grid, the con\u00adnect\u00aded equip\u00adment, and the trans\u00adformer itself, switch ing on is an ordeal. Con\u00adtrollers indi\u00adcate faults, lights flick\u00ader, pro\u00adtec\u00adtive relays trip in error, and entire process\u00ades are affect\u00aded, putting them at risk of break\u00ading down. The term for this is \u201cinrush\u201d or the \u201crush effect\u201d.<\/p>\n\n

TEN TO FIFTEEN TIMES THE NOMINAL CURRENT<\/h2>\n

The surge of inrush cur\u00adrent is caused by the iron core becom\u00ading elec\u00adtro\u00admag\u00adnet\u00adi\u00adcal\u00adly sat\u00adu\u00adrat\u00aded when the trans\u00adformer is switched on. The induc\u00adtive resis\u00adtance goes towards zero. This means that only the effec\u00adtive resis\u00adtance of the trans\u00adformer and the line imped\u00adance are avail\u00adable to lim\u00adit the inrush cur\u00adrent. The rea\u00adson for this is the non\u00adlin\u00adear mag\u00adne\u00adtiz\u00ading imped\u00adance of the trans\u00adformer. The lev\u00adel of inrush cur\u00adrent depends on the switch\u00ading time, the line imped\u00adance (short-cir\u00adcuit capac\u00adi\u00adty), the trans\u00adformer rema\u00adnence (resid\u00adual mag\u00adnet\u00adism), and the con\u00adnect\u00aded load.<\/p>\n

Inrush cur\u00adrents of 10 to 15 times the nom\u00adi\u00adnal cur\u00adrent are not uncom\u00admon. Loads con\u00adnect\u00aded to the trans\u00adformer can reduce inrush cur\u00adrent, but it depends on the type of loads. Some loads can even con\u00adsid\u00ader\u00adably increase the inrush cur\u00adrent; for exam\u00adple, in sit\u00adu\u00ada\u00adtions that use a con\u00adnect\u00aded fre\u00adquen\u00adcy con\u00advert\u00ader with an inter\u00adme\u00addi\u00adate volt\u00adage cir\u00adcuit and a line-side diode con\u00advert\u00ader. In this case, when the trans\u00adformer is switched on with\u00adout a precharg\u00ading unit for the inter\u00adme\u00addi\u00adate cir\u00adcuit, the inter\u00adme\u00addi\u00adate cir\u00adcuit capac\u00adi\u00adtors are also charged. This effec\u00adtive\u00adly results in a high\u00ader inrush cur\u00adrent.<\/p>\n

\n
\n
LIMIT VALUES FOR ACCEPTABLE VOLTAGE DROPS<\/h5>\n
\n

In line with the applic\u00ada\u00adble stan\u00addards, there are a num\u00adber of dif\u00adfer\u00adent require\u00adments and rec\u00adom\u00admen\u00adda\u00adtions for accept\u00adable volt\u00adage drops in the grid depend\u00ading on the con\u00adnec\u00adtion grid lev\u00adel and the con\u00adnec\u00adtion points. In accor\u00addance with the tech\u00adni\u00adcal reg\u00adu\u00adla\u00adtions on assess\u00ading grid feed\u00adback effects (in Ger\u00admany, Aus\u00adtria, Switzer\u00adland, and the Czech Repub\u00adlic), the volt\u00adage drop must not exceed 2 per\u00adcent or 3 per\u00adcent, depend\u00ading on the rep\u00ade\u00adti\u00adtion rate for medi\u00adum-volt\u00adage grids. The tech\u00adni\u00adcal con\u00adnec\u00adtion con\u00addi\u00adtions, which are soon to be estab\u00adlished as tech\u00adni\u00adcal con\u00adnec\u00adtion reg\u00adu\u00adla\u00adtions, spec\u00adi\u00adfy rel\u00ada\u00adtive volt\u00adage changes with a max\u00adi\u00admum of 2 per\u00adcent to 5 per\u00adcent depend\u00ading on the rep\u00ade\u00adti\u00adtion rate for medi\u00adum-volt\u00adage grids and 0.5 per\u00adcent to 2 per\u00adcent for high-volt\u00adage grids.<\/p>\n<\/div>\n<\/div>\n

NEW REGULATIONS EXACERBATE THE PROBLEM<\/h2>\n

The con\u00adse\u00adquences of the inrush effect can be severe, as it caus\u00ades a cor\u00adre\u00adspond\u00ading tem\u00adpo\u00adrary volt\u00adage drop in the grid. This can lead to faults for par\u00adal\u00adlel-con\u00adnect\u00aded con\u00adsumers. In addi\u00adtion, the inrush cur\u00adrent is asym\u00admet\u00adri\u00adcal and con\u00adtains har\u00admon\u00adics that degrade the volt\u00adage qual\u00adi\u00adty fur\u00adther. The time tak\u00aden for the inrush cur\u00adrent to dis\u00adsi\u00adpate increas\u00ades in pro\u00adpor\u00adtion to the size of the trans\u00adformer and ranges from 100 mil\u00adlisec\u00adonds to sev\u00ader\u00adal min\u00adutes. With the new Ecode\u00adsign Direc\u00adtive in place, the need to find effec\u00adtive ways of com\u00adbat\u00ading the inrush effect has become even more press\u00ading. This is because low-loss trans\u00adform\u00aders of the kind spec\u00adi\u00adfied in the Direc\u00adtive have low\u00ader effec\u00adtive resis\u00adtance result\u00ading in cor\u00adre\u00adspond\u00ading\u00adly high\u00ader inrush cur\u00adrents. This makes the trans\u00adform\u00aders par\u00adtic\u00adu\u00adlar\u00adly sus\u00adcep\u00adti\u00adble to the prob\u00adlem\u00adat\u00adic rush effect.<\/p>\n

\n
\n
EMT sim\u00adu\u00adla\u00adtion of the pri\u00adma\u00adry-side inrush cur\u00adrent with and with\u00adout inrush resis\u00adtor. On top: Clear\u00adly vis\u00adi\u00adble inrush cur\u00adrent when switch\u00ading on a trans\u00adformer. Right: Switch\u00ading on the same trans\u00adformer, but with an inrush resis\u00adtor fit\u00adted. The inrush effect has prac\u00adti\u00adcal\u00adly dis\u00adap\u00adpeared.<\/figcaption><\/figure>\n<\/div>\n<\/div>\n

TWO FEASIBLE SOLUTIONS<\/h2>\n

How can we tack\u00adle the prob\u00adlem and reduce inrush cur\u00adrent? The\u00ado\u00adret\u00adi\u00adcal\u00adly, the obvi\u00adous approach would be to switch on the phas\u00ades in a con\u00adtrolled man\u00adner, but this fails in prac\u00adtice, nor\u00admal\u00adly because the asso\u00adci\u00adat\u00aded expense is too great or because the tech\u00adni\u00adcal con\u00addi\u00adtions of the spe\u00adcif\u00adic instal\u00adla\u00adtion would ren\u00adder it impos\u00adsi\u00adble. There are, how\u00adev\u00ader, two oth\u00ader solu\u00adtions which are more prac\u00adti\u00adcal and effec\u00adtive. First solu\u00adtion: Short-term series resis\u00adtance. This involves increas\u00ading the effec\u00adtive resis\u00adtance when start\u00ading the trans\u00adformer; for exam\u00adple, by using an inrush resis\u00adtor that sig\u00adnif\u00adi\u00adcant\u00adly lim\u00adits the inrush cur\u00adrent. Sec\u00adond solu\u00adtion: Pre\u00admag\u00adne\u00adti\u00adza\u00adtion on the low-volt\u00adage side.<\/p>\n

The pre\u00admag\u00adne\u00adti\u00adza\u00adtion unit is con\u00adnect\u00aded to the sec\u00adondary or ter\u00adtiary wind\u00ading of the trans\u00adformer and mag\u00adne\u00adtizes the trans\u00adformer before start-up. This reduces the inrush cur\u00adrent con\u00adsid\u00ader\u00adably so that it is around the range of the mag\u00adne\u00adti\u00adza\u00adtion cur\u00adrent (approx\u00adi\u00admate\u00adly 0.1\u20130.5 per\u00adcent of the nom\u00adi\u00adnal cur\u00adrent). This also prac\u00adti\u00adcal\u00adly elim\u00adi\u00adnates the occur\u00adrence of volt\u00adage drops. How\u00adev\u00ader, pre\u00admag\u00adne\u00adti\u00adza\u00adtion can only be used for trans\u00adform\u00aders that are free from load.<\/p>\n

SOLUTION IN THE PLANNING PHASE<\/h2>\n

The best approach is to devel\u00adop appro\u00adpri\u00adate solu\u00adtions for coun\u00adter\u00ading the inrush effect in the ini\u00adtial plan\u00adning phase. The grid engi\u00adneers from MR Pow\u00ader Qual\u00adi\u00adty (PQ) con\u00adduct grid stud\u00adies that show the reper\u00adcus\u00adsions on a grid when a trans\u00adformer is switched on\u2014including exist\u00ading grids. The experts at MR then use these stud\u00adies to design sys\u00adtems such as inrush resis\u00adtors or pre\u00admag\u00adne\u00adti\u00adza\u00adtion units and car\u00adry out sim\u00adu\u00adla\u00adtions. Once this is com\u00adplete, the results are shared with the cus\u00adtomer.<\/p>\n

\n
\n
The Power Quality division<\/h5>\n
\n

The Pow\u00ader Qual\u00adi\u00adty (PQ) divi\u00adsion at MR has been pro\u00advid\u00ading fil\u00adter and com\u00adpen\u00adsa\u00adtion sys\u00adtems for clean low-volt\u00adage and medi\u00adum-volt\u00adage grids around the world for 20 years. The division\u2019s work focus\u00ades on reduc\u00ading har\u00admon\u00adics and com\u00adpen\u00adsat\u00ading for reac\u00adtive pow\u00ader in pub\u00adlic and indus\u00adtri\u00adal dis\u00adtri\u00adb\u00adu\u00adtion grids.<\/p>\n

<\/i> Find out more about Pow\u00ader Qual\u00adi\u00adty (PQ) divi\u00adsion<\/strong><\/a><\/p>\n<\/div>\n<\/div>\n

When an order has been placed, PQ arranges for the in-house designs to be man\u00adu\u00adfac\u00adtured to MR spec\u00adi\u00adfi\u00adca\u00adtions at QA-cer\u00adti\u00adfied pro\u00adduc\u00adtion sites, after which the com\u00adpo\u00adnents are installed at the des\u00adig\u00adnat\u00aded site. The inrush resis\u00adtors with inte\u00adgrat\u00aded bypass cir\u00adcuit break\u00aders and\/or pre\u00admag\u00adne\u00adti\u00adza\u00adtion units then con\u00adtain the inrush cur\u00adrent when the trans\u00adformer is switched on. The PQ spe\u00adcial\u00adists have demon\u00adstrat\u00aded the effec\u00adtive\u00adness of both sys\u00adtems by deliv\u00ader\u00ading them to var\u00adi\u00adous grids around the world, pro\u00advid\u00ading solu\u00adtions for trans\u00adform\u00aders with out\u00adputs rang\u00ading from 1 to 100 MVA and nom\u00adi\u00adnal volt\u00adages between 6 kV and 230 kV.<\/p>\n

\n

YOUR CONTACT <\/h2>\n

Would you like to pre\u00adpare for inrush effects? <\/strong>Thomas Br\u00fcck\u00adn\u00ader of the Pow\u00ader Qual\u00adi\u00adty divi\u00adsion is here to help:
\n<\/i> t.brueckner@reinhausen.com<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

Switch\u00ading on a pow\u00ader\u00adful trans\u00adformer is a crit\u00adi\u00adcal moment for the sup\u00adply grid and all con\u00adnect\u00aded con\u00adsumers. For\u00adtu\u00adnate\u00adly, there are two tech\u00adniques for effec\u00adtive\u00adly damp\u00aden\u00ading the inrush cur\u00adrent.<\/p>\n","protected":false},"author":4,"featured_media":3287,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"wp_typography_post_enhancements_disabled":false,"footnotes":""},"categories":[4],"tags":[],"class_list":["post-2881","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-07-2018"],"acf":[],"_links":{"self":[{"href":"https:\/\/onload.reinhausen.com\/en\/wp-json\/wp\/v2\/posts\/2881","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/onload.reinhausen.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/onload.reinhausen.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/onload.reinhausen.com\/en\/wp-json\/wp\/v2\/users\/4"}],"replies":[{"embeddable":true,"href":"https:\/\/onload.reinhausen.com\/en\/wp-json\/wp\/v2\/comments?post=2881"}],"version-history":[{"count":2,"href":"https:\/\/onload.reinhausen.com\/en\/wp-json\/wp\/v2\/posts\/2881\/revisions"}],"predecessor-version":[{"id":8521,"href":"https:\/\/onload.reinhausen.com\/en\/wp-json\/wp\/v2\/posts\/2881\/revisions\/8521"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/onload.reinhausen.com\/en\/wp-json\/wp\/v2\/media\/3287"}],"wp:attachment":[{"href":"https:\/\/onload.reinhausen.com\/en\/wp-json\/wp\/v2\/media?parent=2881"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/onload.reinhausen.com\/en\/wp-json\/wp\/v2\/categories?post=2881"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/onload.reinhausen.com\/en\/wp-json\/wp\/v2\/tags?post=2881"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}