{"id":9791,"date":"2023-07-21T14:49:37","date_gmt":"2023-07-21T12:49:37","guid":{"rendered":"https:\/\/onload.reinhausen.com\/de\/?p=9791"},"modified":"2023-07-21T14:49:37","modified_gmt":"2023-07-21T12:49:37","slug":"tov-type-testing-high-voltage-dc-cable","status":"publish","type":"post","link":"https:\/\/onload.reinhausen.com\/en\/07-2023\/tov-type-testing-high-voltage-dc-cable\/","title":{"rendered":"Stress test with Megavolt"},"content":{"rendered":"\n
\n\n\n\n

When we draw elec\u00adtric\u00adi\u00adty from the sock\u00adet at home, it is elec\u00adtric\u00adi\u00adty that changes polar\u00adi\u00adty \u2013 in oth\u00ader words, alter\u00adnat\u00ading cur\u00adrent,\u201d says Dr. Ralf Pietsch, Head of Sci\u00adence and Doc\u00adu\u00admen\u00adta\u00adtion at HIGHVOLT. Over long stretch\u00ades of land and sea, how\u00adev\u00ader, the elec\u00adtric\u00adi\u00adty flows as direct cur\u00adrent and is only con\u00advert\u00aded to alter\u00adnat\u00ading cur\u00adrent by con\u00advert\u00ader sta\u00adtions near pop\u00adu\u00adla\u00adtion cen\u00adters. Pietsch explains, \u201cDur\u00ading these switch\u00ading process\u00ades, how\u00adev\u00ader, faults can cause the volt\u00adage on the DC cables to dou\u00adble from 525 kilo\u00advolts to more than one mega\u00advolt for a few microsec\u00adonds to mil\u00adlisec\u00adonds, or to even change polar\u00adi\u00adty.\u201d <\/p>\n\n\n\n

This so-called tem\u00adpo\u00adrary over\u00advolt\u00adage (TOV for short) is pure stress for DC cables and can dam\u00adage their insu\u00adla\u00adtion. It can also cause space-charge phe\u00adnom\u00ade\u00adna inside the cable, which can lead to local field surges in the cable when the polar\u00adi\u00adty of the volt\u00adage changes, there\u00adby dam\u00adag\u00ading the cable. If the cable fails, near\u00adby elec\u00adtri\u00adcal equip\u00adment or even peo\u00adple are then at risk.<\/p>\n\n\n\n

Manufacturer want stress<\/h2>\n\n\n\n

To ensure that noth\u00ading dan\u00adger\u00adous hap\u00adpens in the event of an over\u00advolt\u00adage or total fail\u00adure of the cable, more and more cable man\u00adu\u00adfac\u00adtur\u00aders are test\u00ading their DC cables with the new TOV type test. \u201cThis test does not yet have IEC stan\u00addards but is already described and rec\u00adom\u00admend\u00aded in the CIGRE brochure as an option\u00adal test method,\u201d Pietsch tells us. The test is car\u00adried out at the end of a large test series as the ulti\u00admate stress test. For about 100 mil\u00adlisec\u00adonds, a mega\u00advolt is applied to the cable in a con\u00adtrolled man\u00adner. Only when the cable has sur\u00advived this can it be deliv\u00adered to the net\u00adwork oper\u00ada\u00adtor.<\/p>\n\n\n\n

\n
<\/span>
\n

<\/p>\n<\/div><\/div>\n\n\n\n

\n
\n
<\/div>\n\n\n\n
\n
\n

A num\u00adber of com\u00adpo\u00adnents are required for the stress test<\/strong>: a capac\u00adi\u00adtor tow\u00ader, two DC volt\u00adage sources, two sphere gaps, a resis\u00adtor as well as a volt\u00adage divider and the end ter\u00admi\u00adna\u00adtion to which the DC cable is con\u00adnect\u00aded.<\/p>\n<\/div><\/div>\n<\/div>\n\n\n\n

<\/div>\n<\/div>\n\n\n\n
\n
<\/div>\n\n\n\n
\n
\n

In this 16-meter-high capac\u00adi\u00adtor tow\u00ader<\/strong>, the volt\u00adage ris\u00ades to over one mega\u00advolt before it reach\u00ades the test cable via sphere gap.<\/p>\n<\/div><\/div>\n<\/div>\n\n\n\n

<\/div>\n<\/div>\n<\/div><\/div>\n<\/div><\/div>\n\n\n\n

How\u00adev\u00ader, TOV test\u00ading is very com\u00adplex. After all, the test set\u00adup fills the area and height of an entire test hall. Ralf Pietsch adds: \u201cIn addi\u00adtion, the indi\u00advid\u00adual test com\u00adpo\u00adnents must also with\u00adstand the over\u00advolt\u00adage \u2013 and not just once like the cable to be test\u00aded, but with each sub\u00adse\u00adquent test. This requires spe\u00adcial mate\u00adri\u00adals, bush\u00adings and insu\u00adla\u00adtion.\u201d<\/p>\n\n\n\n

The test itself con\u00adsists of three sub-tests to check all pos\u00adsi\u00adble types of tem\u00adpo\u00adrary over\u00advolt\u00adage in cir\u00adcuits. In all cas\u00ades, a DC high volt\u00adage of 525 kilo\u00advolts is applied via a DC volt\u00adage source to an end ter\u00admi\u00adna\u00adtion that is con\u00adnect\u00aded to the test cable. In addi\u00adtion, a volt\u00adage divider is also con\u00adnect\u00aded to the end ter\u00admi\u00adna\u00adtion, via which the tem\u00adpo\u00adrary over\u00advolt\u00adage can be mea\u00adsured. A sec\u00adond DC volt\u00adage source is used in par\u00adal\u00adlel to charge a 16-meter-high capac\u00adi\u00adtor tow\u00ader (a mod\u00adi\u00adfied pulse volt\u00adage gen\u00ader\u00ada\u00adtor) to over one mega\u00advolt. <\/p>\n\n\n\n

Con\u00adnect\u00aded to this is a sphere gap with two oppos\u00ading spheres made of a tung\u00adsten-cop\u00adper alloy. \u201cThis par\u00adtic\u00adu\u00adlar alloy is impor\u00adtant because on the spheres, the accu\u00admu\u00adlat\u00aded over\u00advolt\u00adage of the capac\u00adi\u00adtor turns into an extreme\u00adly hot arc, and nor\u00admal cop\u00adper would sim\u00adply melt in the process,\u201d explains Pietsch. \u201cThe over\u00advolt\u00adage then pass\u00ades through an inte\u00adgrat\u00aded resis\u00adtor to the end ter\u00admi\u00adna\u00adtion and ulti\u00admate\u00adly into the cable.\u201d<\/p>\n\n\n\n

This is how the TOV test is structured<\/h3>\n\n\n\n
\n\n\n\n
\n\t\t\t\t\t\t
<\/div>\n\t\t\t\t\t\t

Capacitor Tower<\/h4>
\n\t\t\t\t\t\t

-<\/p>\n\t\t\t\t\t\t <\/div>\n\t\t\t\t\t\t <\/div>\n\t\t\t\t\t\t <\/div><\/span><\/a>

<\/div>
\n\t\t\t\t\t\t
<\/div>\n\t\t\t\t\t\t

DC voltage source<\/h4>
\n\t\t\t\t\t\t

-<\/p>\n\t\t\t\t\t\t <\/div>\n\t\t\t\t\t\t <\/div>\n\t\t\t\t\t\t <\/div><\/span><\/a>

<\/div>
\n\t\t\t\t\t\t
<\/div>\n\t\t\t\t\t\t

DC voltage source<\/h4>
\n\t\t\t\t\t\t

-<\/p>\n\t\t\t\t\t\t <\/div>\n\t\t\t\t\t\t <\/div>\n\t\t\t\t\t\t <\/div><\/span><\/a>

<\/div>
\n\t\t\t\t\t\t
<\/div>\n\t\t\t\t\t\t

Sphere gap<\/h4>
\n\t\t\t\t\t\t

-<\/p>\n\t\t\t\t\t\t <\/div>\n\t\t\t\t\t\t <\/div>\n\t\t\t\t\t\t <\/div><\/span><\/a>

<\/div>
\n\t\t\t\t\t\t
<\/div>\n\t\t\t\t\t\t

Sphere gap<\/h4>
\n\t\t\t\t\t\t

-<\/p>\n\t\t\t\t\t\t <\/div>\n\t\t\t\t\t\t <\/div>\n\t\t\t\t\t\t <\/div><\/span><\/a>

<\/div>
\n\t\t\t\t\t\t
<\/div>\n\t\t\t\t\t\t

Resistor <\/h4>
\n\t\t\t\t\t\t

-<\/p>\n\t\t\t\t\t\t <\/div>\n\t\t\t\t\t\t <\/div>\n\t\t\t\t\t\t <\/div><\/span><\/a>

<\/div>
\n\t\t\t\t\t\t
<\/div>\n\t\t\t\t\t\t

Voltage divider<\/h4>
\n\t\t\t\t\t\t

-<\/p>\n\t\t\t\t\t\t <\/div>\n\t\t\t\t\t\t <\/div>\n\t\t\t\t\t\t <\/div><\/span><\/a>

<\/div>
\n\t\t\t\t\t\t
<\/div>\n\t\t\t\t\t\t

End termination with the DC cable<\/h4>
\n\t\t\t\t\t\t

-<\/p>\n\t\t\t\t\t\t <\/div>\n\t\t\t\t\t\t <\/div>\n\t\t\t\t\t\t <\/div><\/span><\/a>

<\/div>
\n\t\t\t\t\t\t
<\/div>\n\t\t\t\t\t\t
\n\t\t\t\t\t\t

<\/p>\n\t\t\t\t\t\t <\/div>\n\t\t\t\t\t\t <\/div>\n\t\t\t\t\t\t <\/div><\/span><\/a>

<\/div><\/div>\n<\/div><\/div>\n\n\n\n

In the first part of the test, the over\u00advolt\u00adage is slow\u00adly dis\u00adsi\u00adpat\u00aded via the ground. In the sec\u00adond part of the test, how\u00adev\u00ader, the volt\u00adage drops abrupt\u00adly. For this pur\u00adpose, anoth\u00ader sphere gap is con\u00adnect\u00aded between the 525-kilo\u00advolt DC source and the earth, which abrupt\u00adly removes the over\u00advolt\u00adage from the cable. In the last sub-test, the over\u00advolt\u00adage also changes polar\u00adi\u00adty at a high fre\u00adquen\u00adcy.<\/p>\n\n\n\n

\n

\u201cWe are see\u00ading more and more net\u00adwork oper\u00ada\u00adtors request\u00ading TOV test\u00ading.\u201d<\/p>\nDr. Ralf Pietsch, Head of Sci\u00adence and Doc\u00adu\u00admen\u00adta\u00adtion at HIGHVOLT<\/cite><\/blockquote>\n\n\n\n

Know-how and components<\/h2>\n\n\n\n

\u201cSince the TOV test is rel\u00ada\u00adtive\u00adly new, it is not yet manda\u00adto\u00adry for cable man\u00adu\u00adfac\u00adtur\u00aders,\u201d says Ralf Pietsch. \u201cBut we see that more and more net\u00adwork oper\u00ada\u00adtors are demand\u00ading this stress test.\u201d HIGHVOLT has been involved here from the very begin\u00adning and has already been able to sup\u00adply com\u00adpo\u00adnents or the com\u00adplete test set\u00adup for cable man\u00adu\u00adfac\u00adtur\u00aders such as Prys\u00admi\u00adan, Nex\u00adans or inde\u00adpen\u00addent test insti\u00adtutes such as FGH Mannheim<\/p>\n\n\n\n

\u201cWith these orders, we have been able to gain quite a bit of expe\u00adri\u00adence in recent years in order to improve and stan\u00addard\u00adize the test\u00ading even fur\u00adther,\u201d Pietsch con\u00adtin\u00adues. \u201cFur\u00adther\u00admore, I am sure that TOV type test\u00ading will become manda\u00adto\u00adry in the near future. After all, grid ope\u00adrators want to play it safe with cables before they lay them in the ground.\u201d In the con\u00adtext of the ener\u00adgy tran\u00adsi\u00adtion and the expan\u00adsion of the Ger\u00adman pow\u00ader grid with under\u00adground cables, it can there\u00adfore be assumed that the demand for TOV test\u00ading will increase sig\u00adnif\u00adi\u00adcant\u00adly. It\u2019s good that HIGHVOLT already has the exper\u00adtise and all the com\u00adpo\u00adnents to pro\u00advide such test\u00ading.<\/p>\n\n\n\n

<\/div>\n\n\n\n
\n\n\n
\n
<\/figure>\n<\/div>\n\n\n

YOUR CONTACT<\/h2>\n\n\n\n

Do you have ques\u00adtions about the TOV-test?<\/strong>
Ralf Pietsch is there for you:
<\/i> \u2009R.Pietsch@highvolt.com<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

Tem\u00adpo\u00adrary over\u00advolt\u00adages can be dan\u00adger\u00adous for high-volt\u00adage DC cables. The new TOV type test can be used to find out whether cables can with\u00adstand this stress. HIGHVOLT sup\u00adplies the appro\u00adpri\u00adate test com\u00adpo\u00adnents for this pur\u00adpose.<\/p>\n","protected":false},"author":7,"featured_media":10441,"comment_status":"closed","ping_status":"open","sticky":false,"template":"template-cover.php","format":"standard","meta":{"_acf_changed":false,"wp_typography_post_enhancements_disabled":false,"footnotes":""},"categories":[38],"tags":[],"class_list":["post-9791","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-07-2023"],"acf":[],"_links":{"self":[{"href":"https:\/\/onload.reinhausen.com\/en\/wp-json\/wp\/v2\/posts\/9791","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\/7"}],"replies":[{"embeddable":true,"href":"https:\/\/onload.reinhausen.com\/en\/wp-json\/wp\/v2\/comments?post=9791"}],"version-history":[{"count":3,"href":"https:\/\/onload.reinhausen.com\/en\/wp-json\/wp\/v2\/posts\/9791\/revisions"}],"predecessor-version":[{"id":10540,"href":"https:\/\/onload.reinhausen.com\/en\/wp-json\/wp\/v2\/posts\/9791\/revisions\/10540"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/onload.reinhausen.com\/en\/wp-json\/wp\/v2\/media\/10441"}],"wp:attachment":[{"href":"https:\/\/onload.reinhausen.com\/en\/wp-json\/wp\/v2\/media?parent=9791"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/onload.reinhausen.com\/en\/wp-json\/wp\/v2\/categories?post=9791"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/onload.reinhausen.com\/en\/wp-json\/wp\/v2\/tags?post=9791"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}