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Thanks wcarter,waross & Scotty Uk for your replies, As mentioned previously for the case of the (Batch Plant) older Vacuum Circuit Breakers they can be replaced with a higher fault rating e,g, 26-> 31.5kA, the problem is with the switchgear busbar assembley supports etc.The original switchgear...

Thanks for your input, I presume the 65kA rated SWGR is the Symmetrical SC Current rating typically 1sec- designed to withstand that value for that period (without damage) and not the peak ? My interest is in the 1st cycle peak and subsequent 6cycles (US 6x0.016 approx=0.1sec)with motor fault...

Hi Waross, A good point. For the Batch plant all the large loads (<100kW) were modelled with cables.The smaller drives were "lumped" and the ratio of locked rotor current/FLC reduced from typically x8 to x5 - inline with the UK G74 recommendation for the estimation of m.f.c.including...

Thanks to both for the last comments; My reference to the peak load was relating to the estimated % maximum of connected motors at any one time rather than the base load + the largest motor(s) starting,but I take your point. For the batch plant,part of the process is considered "new" re...

Hi jghrist, Thanks for your input Its probably unlikely in this case that 65% of the motors will be running this would be considered as conservative, more likely to be 50%.If it was possible to say what the peak load was and base the analysis that a fault developed upstream simultaneously...

Hi waross, Thanks again for taking the time to reply and nicely explained. In general,two examples I have considered to obtain a realistic order of magnitude for motor fault contribution are: a) Batch Plant: Where the motor fault contribution is calculated using the guidelines of the UK G74...

waross, Thanks for the comments, much appreciated. We have included the impedance of the cables,typically 11kV,400sqm sc, 1.5kM long between substations.Although as this is so close re: 8% over, as you indicated, its worth an accurate measurement on length and perhaps increase the lengths to...

I would be most grateful for the forums comments on the following: a) Has anyone approached an MV switchgear manufacturer for an opinion on whether an MV busbar will withstand approx the first 6 cycle and ½ cycle peak when a short circuit study indicates that the infeed short circuit...

prc- This has come up on Eng-Tips before re: ScottyUK & RalphChristie Went under the name of AREVA PRAG (Network Protection & Automation Guide) If you google AREVA T & D website (2011) this now comes up as AREVA T & D joins Alstom and Schneider .........I gather the GEC Althstom protective...

You may find this extract from the AREVA T & D PRAG guide usefulhttp://files.engineering.com/getfile.aspx?folder=82bac60e-d394-490a-b928-5ce75ed98a8c&file=AREVA_PRAG_GUIDE_-Extract_-Transformer_Parameters.docx

I have found in the past that if you contact the manufacturer of the cable they will advise you on the appropriate test voltages & time period.Also speak to a recognised good MV cable test engineer(s). The values I have used for 6.35/11kV Cu/XLPE/SWA/PVC cables in practice has been: 5kV...

Thank you Discop, Have now found a .pdf brochure on this relay on the Areva T & D website.

Does anyone have any information or a web site where I might obtain information on this protection relay? I have tried the Areva site with no success. There are 2 such relays each installed on dual 11kV feeders to two main 11kV ABB switchboards,for o/c & e/f protection.

ScottyUK/UKEng, I have been predominatly working in the UK/Europe Paper & Pulp Industry over the last 10-15years,but only came into contact with Arc Flash Studies early last year. The studies I have conducted are based on using SKM Power Tools software - CAPTOR & DAPPER incorporating IEC60909...

Hi Scotty UK, Sorry not replied sooner,have you been able to establish whether ERA's ERACS software has an Arc Flash Evaluation software module?. Your comments suggest you have accurate site data re:protection device"As Found" settings,transformer details etc.I appreciate to remodel on SKM...

Hi Scotty UK, I have conducted a number of Arc Flash studies in the UK in the past year,using SKM Power Tools software,for a USA based client.The calculation of the 3 phase fault levels were made using the IEC 60909 and the G74-Engineering recommendations.We used the IEEE 1584 although the same...