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  1. vandax

    Sensitive ground fault

    Thanks for kind response and great input. According to bigamp' input, Most of our feeders are using the bushing CT, and GE's neutral relay set at 90-120 A as a minimum pickup setting with inverse curve. The relay is also coordinated with the recloser/sectionalizer under respective line. My...
  2. vandax

    Sensitive ground fault

    Hi Does anyone has experience with application of sensitive ground fault relay in the distribution line. We just have an experienced that the neutral relay is not detect the fault (broken of 1 phase wire and lay down on the ground) in 13.8 kV distribution line (20 ohm grounded system)...
  3. vandax

    Arrester selection for system with neutral grounding resistor

    In our 13.8 kV distibution line system with 20 Ohm NGR, we kept to use the 15 kV voltage rating, and 12.75 Maximum Continous Over Voltage. The MCOV is determined by possibility of voltage increment in unfaulted phases when single phase to ground occurred. This all is according to ANSi and...
  4. vandax

    Isolated Ground

    jghrist, Thanks for your susggestion. That's rigth, we don't concern to analysis of transient yet. The tool we have right now is ETAP only. Dandel, Actualy, this idea is come out by my collegua, and almost all of us agree to implement this immediately as current point of view/perspective. Why...
  5. vandax

    Isolated Ground

    Sorry, I still use this thread, since its relevance.. jghrist, 1). all our LA in distribution line has consider Vpp, so there would be no problem with the arrester or other eq. 2). most of our TX connection are delta wye, so it would not make voltage unbalance in load side/motor. 3). Up to...
  6. vandax

    Isolated Ground

    In response Jghrist's comment, I need to clarify that we still use the ground relay(51G), which should be set under the 51N at feeders. So, whenener single phase fault occurred at the line, the 51G will sense and initiate to open the "new additional breaker beetwen neutal Tx - ground&quot...
  7. vandax

    Isolated Ground

    I would extend Yme48 questions, the case is in 13.8 kV distribution line. There is an idea by my collegua to reduce phase to ground/temporary fault by operating the system to be isolated neutral when the fault occured, so there will no longer zero sequence flowing in the system. This idea can be...
  8. vandax

    Permissible loading for transformer

    We have been operating 90/150(FOA) MVA transformer for 230/115 kV for 3 years. I have no accurare refference, how many % the transformer can be loaded exceed its maximum capacity? The fact that..sometimes we loaded it 125% of maximum cap for a 15-20 menutes due to operation need. Present...
  9. vandax

    Impact loosing 1 phase of 3 phase to motor

    Hi. We have experienced with loose connection of 1 phase in 3 phases 13.8 kV system, and caused several motors/load damaged. Since the loose connection occurred at branch line (15-25 A) of 300 A feeder's load, the recloser/51N at feeder would not pickup & operated. I need your help on analyze...
  10. vandax

    nuisance tripping

    Beside agree with bigamp comment's, I would suggest to consider: 1.Install disturbance recorder in your system, to know what was/is happen in your system. You will reduce time & cost for investigation. 2. Re-check the relay after it has already tripped, to make sure it has worked well. 3. Check...
  11. vandax

    Asking the different of rod and pipe for grounding

    Dear friends, have you discussed the different of using ground rod & ground well/pipe for the size/diameter? I have search to standard, there is no mention the formula of using pipe, almost all of reference just mention to use cooper rod, plate, ring.. My opinition, as skin effect that the...
  12. vandax

    Earthing lightning arrester

    I mean that the bare cooper (same wire for static) is used to connect the bottom of LA to ground. For certain pole, we also ground the static in order to get lower system impedance.
  13. vandax

    Earthing lightning arrester

    Thanks friends. Actually our pole design is using pipe pole, and static wire is barecooper 35 mm. If we consider that the impedance of barecooper is lower than pipe, this method is okey, otherwise...
  14. vandax

    Earthing lightning arrester

    Dear friends, please advice regarding method of earthing LA at distribution line. In our current practice 13.8 kV line with using pipe pole, the LA is always earthed to gound via pole (brazed), but our new study shown that the earthing of LA must be via a special wire to reduce impact of surge...
  15. vandax

    Operation of Synchronous Generator as Induction Generator.

    I would suggest to apply breaker relay, in case the generator breaker woudln't operate, the time delay and relay sensing also used to operate the next level breaker. Any comment?

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