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  1. xabproject

    Line Protection Relays for HV and EHV

    There is one way of getting it from ABB itself. Ask for "reference list" for the 670 series relay of your interest complete with authentic "customer feedback" from utilities already using them. There are some relays supplied to the 400kV and 132kV networks in UAE for utilities such as FEWA...
  2. xabproject

    SM symbol

    TM is a trade mark that is not yet registered. R in a circle denotes a registered trade mark. A service mark is a trademark applied to a service, whereas a trademark is applied to a product. And a C in a circle means that it is copyrighted, and cannot be used without permission from the owner...
  3. xabproject

    Maintenance on station class surge arrestors.

    Electic, SA are replaced based on following criteria in most networks: 1. When the Continuous / Steady State Leakage current as measured in the leakage current meter is 4/6/8/10 times the value at commissioning instant 2. More than twice the number of discharges in any specific period, as per...
  4. xabproject

    CT Accuracy Class

    Hi, Found on the nameplate of a CT (Gas Insulated Switchgear of Japanese make): CT Ratio – 2500/1 A Turns ratio – 1/2500 Accuracy class – 0.03X700R6 Can you please explain this accuracy class? I guess, CT class is X and 0.03A is mag current at knee point voltage 700V and winding resistance...
  5. xabproject

    Soil Resistivity Measurement

    Client's specification calls for soil resistivity to be measured before and after backfilling if the thickness of back-fill exceeds 1m. Wonder why this should be done!? [ponder] Does this have any reference to IEEE 80 / 81? I am working is IEC area. Thanks in advance! If there is a separate...
  6. xabproject

    ZnO Elements in Regulating Windings of Transformers

    Dear All, Any information on the use of ZnO Elements in the Regulating Windings of Transformer will be a great help.[bigears] Thanks!
  7. xabproject

    Transmission line conductor current rating vis-a-vis the wind velocity

    Dear RRN, One particular Client's specification calls for the use of 0.609m/sec! Let us know what was finally accepted in your case. best regards,
  8. xabproject

    Transmission line conductor current rating vis-a-vis the wind velocity

    Dear RRN, Free convection air current is taken as 0.2-0.5ft/sec. All formulae for Convectively dissipated Watts are applicable only above "these" air current values (- look for specific formula for application). Standstill air cannot dissipate convective heat, by logic! Your Wc will be zero, if...
  9. xabproject

    MV Sw Gr - Wiping Contact/Momentary contact

    Client's specification calls for two (2nos) Wiping Contacts as part of the Auxiliary Switch Contacts of a 11kV Sw Gr Breaker. It also calls for "slow closing device". Can some one help me with what purpose do these serve? thanks in anticipation!
  10. xabproject

    CBEMA / ITIC curve (50 Hz)

    Dear MissMe, Hers is a brief on the curve. See the reference to one mains cycle of 20ms meaning the graph is equally applicable to 50Hz systems! best regards, The Information Technology Industry Council (ITIC) curve, formerly known as the Computer and Business Equipment manufacturers...
  11. xabproject

    Restricted Earth Fault Protection

    Dear electromott, I meant distribution level 'voltage', typically the 433V. best regards,
  12. xabproject

    Restricted Earth Fault Protection

    Dear electromott, REF is about balancing the residual current of the phase CTs against the current of neutral CT. As one approaches the distribution level, the current transformer ratios become 'numerically' higher leading to 'less effective' translation of current changes/unbalances. At the...
  13. xabproject

    Transformer reliability data

    Dear PowerfulStuff, Following extract from an article makes a point - Determination of the probable condition of today’s operating, and somewhat aged, power transformers is a complex and arduous exercise. This requires a rigorous methodology in order to benchmark and rank the units on any...
  14. xabproject

    Transformer reliability data

    Dear PowerfulStuff, Are you looking for data in the form of <<Unit Size-No of Units-Forced Outage Rate-MTTF-MTTR-Scheduled Maintenance wks/year-Loading pattern(daily/weekly/yearly)>>? MTTF: Mean Time To Failure MTTR: Mean Time To Repair FOR: (MTTR)/(MTTR+MTTF) Not that I have the figures readily...
  15. xabproject

    Contact Rating?

    Dear Kiribanda, Suggested reading - Article 2.6.3(c) from Van Warrington's Volume 2: Protective Relays - Their Theory and Practice. For a project in the erstwhile SCECO(E) - Saudi Consolidated Electric Company in the Eastern Province, I was asked to do a complete application check on the usage...
  16. xabproject

    CT secondary earthing

    Dear Salem, Here is an extract: IEEE standard C57.13.3 serves as the ANSI guide to standardize instrument transformer grounding practices. The grounding of CTs is important to both safety and the correct operation of protective relays. To assure safe and reliable operation, the neutral of the...
  17. xabproject

    Transformer Oil IFT vs NN - which is early indicator (SDMyers)

    Dear electricpete, Thanks for the enticing and memorable "conversation". I too go by your decision to include IFT based on #1 and #2 of your last reply. Something equally interesting follows - about your question "why IFT is important enough for transformers but not for rotating machines?" The...
  18. xabproject

    Transformer Oil IFT vs NN - which is early indicator (SDMyers)

    Also, please see 'ntt' links under thread242-116334 under the forum IEEE Code issues Best regards
  19. xabproject

    Transformer Oil IFT vs NN - which is early indicator (SDMyers)

    Dear electricpete, Please see whether the following would suffice: 1. IFT is classified, along with tests for color, flash point,viscocity, RI, etc., under the PHYSICAL TESTS whereas the NN test is a CHEMICAL TEST, classified so along with Test for corrosive sulfur, water content, etc. 2...
  20. xabproject

    Protection Relays Testers

    Dear robb1, Please, can I have details of your order/ordering information for the cofiguration+accessories that you have. I presume you have tested satisfactorily T/L Protection relays of all the popular makes/vendors. We are in the process of finalizing an order for the same Omicron CMC256 with...

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