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  • Users: Kiribanda
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  1. Kiribanda

    GF Current Coordination of a HRG System

    During NGR sizing we estimate the total capacitance current and we set NGR current rating slightly above the estimated system total charging current. During feeder GF settings what is the industry practiced percentage that the feeder GF setting should have above its own feeder charging current?
  2. Kiribanda

    Mitigation of Transferred Potential

    Hello members, It is an industry practice to separate two ground rods by 2 times the rod length so that one is not influenced by the other. Similarly, to mitigate the transfer of GPR as a transferred potential from SUB A to SUB B, instead of sharing a single ground grid for both subs, is it...
  3. Kiribanda

    Grounding of Skid Mounted Substaions

    Hi, In an outdoor air insulated substation where an overhead transmission line is terminated, the underground ground grid (mesh)consists of bare copper conductors and rods. This design ensures that during a ground fault when the ground fault current is flowing back to the remote neutral through...
  4. Kiribanda

    Bonding of Steel Suport Structures to Copper Ground Grid

    Hello members, I had raised this question in electrical forum but was not lucky enough to get a solid answer. In outdoor electrical substations the steel support structures (hot dipped galvanized) are bonded to the underground Copper ground grid (designed for safety & protection) using copper...
  5. Kiribanda

    Plate vs Rod Electrodes

    Gentlemen, I have seen some engineers and electricians specially who are working in the IEC world,prefer to use plate electrodes than rod electrodes.Most of these copper plates are avaialble in 36"x36"xGauge 20 which is about 1.5 mm thick.I strongly feel that it will get deformed after sometime...
  6. Kiribanda

    How to Wire a FT Switch in a Delta Connected CTs?

    Gentlemen, Appreciate inputs on the following CT isolation issue. During electromechanical relay time, the CTs in the wye side of any Dyn transformer were connected in delta (delta side wye connected) and wired to the interposing CTs. Since there is no common wire available for this delta...
  7. Kiribanda

    RCVT to Relay Connection

    Gentlemen, Recently I read a paper on RCVTs and came to know that they have an A/D converter and can operate on a very broad frequency band.As a result,not like a CCVT or EMVT,a RCVT gives a true image of the frequency variations of the HV line if someone is interested in harmonic measurements...
  8. Kiribanda

    CORONA Voltages

    Gentlemen, Can anybody post up the two equations used to calculate 1)Corona inception voltage 2)Distruptive Critical voltage when conductor size and ambient conditions are given for an HV outdoor substation? Thanks in advance for your time.
  9. Kiribanda

    Bonding Copper to Galvanized Steel

    Gentlemen, I have a question on bonding copper to galvanized steel. In all electrical outdoor substations, usually the ground grid buried is COPPER. The substation fence is usually HOT DIP GALVANIZED STEEL. Normally this fence is bonded to the grid using thick COPPER wire to avoid any shock...
  10. Kiribanda

    Lightning Shielding Software

    Hi, Can any member please throw some light on few leading software program(s) used for "Designing Lightning Shielding Systems for Outdoor Substations". Thnaks in advance
  11. Kiribanda

    Suspension Insulator Strings

    Gentlemen, For Station Post Insulators the deciding parameter is always the applicable BIL value. But for Suspension type insulators (Specially for polymer insulator strings) manufacturers specify various parameters such as Dry/ Wet flash over and Critical Impulse Flash Over (CIFO-Pos & Neg)...
  12. Kiribanda

    Sync. Generator Data

    Gentlemen, Could anybody please help me to get typical values of 1)Xd", Xd', Xs, X2, X0 and X/R ratio 2)Tdo", Tdo', TdO of a 12 kV, 5-10 MVA sync. generator (hydro)? Kiri
  13. Kiribanda

    FT Switches for Dual Protection Scheme

    Gentlemen, Could anybody please upload a correct three line diagram showing how four FT switches (two for each relay) are used with one CT in a dual protective relay scheme (Make A & B) for a simple 50/51 function? Thanks in advance Kiri
  14. Kiribanda

    Voltage Factor of PTs for Extended Periods

    Gentlemen, On a 15 kV ungrounded system,it is normal to use STAR GROUNDED-OPEN DELTA VTs to obtain 59N function.During a ground fault the STAR winding is subjected to full line to line voltage (in the worst case) and continue to operate till the fault is found and cleared. The time taken to...
  15. Kiribanda

    Surge Arresters and Surge Capacitors

    Hi all, In most generator installations, we can see that both surge arresters and surge capacitors had been installed. Could any body throw some light about the application of these two different equipment in generator installations? (Any text book or IEEE technical paper to read?) Thanks in...
  16. Kiribanda

    CP for Copper Ground Grid

    Gentlemen, As far as I understand (please correct me if I am wrong), the protective levels required for the following underground structures protected by an Impressed current system are, 1) Steel = -0.85 V dc 2) Copper = -0.20 V dc with respect to a Cu/ CUSO4 half cell. Now if we bond an...
  17. Kiribanda

    Can we use on HRG/ Ungrounded systems?

    Gentlemen, It is a common practice to specify and install circuit breakers rated & tested per ANSI C37.06/ C37.09/ IEC 62271-100 on High Resistance Grounded (HRG) or DELTA-DELTA ungrounded networks, specially in industrial applications on 5-38 kV range. But the application of these HV/ MV...
  18. Kiribanda

    To Handle 100% Reactive Load

    Gentlemen, A spec of a 50 MVA, 230-13.8 kV stepdown power transformer associated with a Staic Var Control (SVC) system specifies "This Power Transformer shall be designed to handle 100% Reactive Load". 1)Could any member please explain about the special features of such a transformer? 2)Is it...
  19. Kiribanda

    Short Circuit Current at Half Rated Voltage

    Gentlemen, I have got a question on secondary short circuit currents of a centre tapped single phase transformer. The name plate of a single phase transformer is as follows. 37.5 kVA, Primary: 600 V, Secondary: 120/ 240 V, Z = 5.3 %. Primary FLC= 62.5 A,Secondary FLC=156.25 A. Therefore...
  20. Kiribanda

    TVSS Specification

    Gentlemen, This question is about TVSS/ SPD (Transient Voltage Surge Suppressors/ Surge Protective Devices) mainly used in LV (600, 208 V 3-ph) industrial installations where sensitive electronic load centers (e.g. Work stations, Servers etc) are served. Most of the TVSS units available in...

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