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Ronald... I also want to alert you to another phenomenon that could result in low-magnitude ground-current. It can occur if the resistive effect of the generator’s NGT method results in a resistor too small to fully negate the effect of a large MV system’s Ground-Capacitance! High...

Ronald... I believe your 'incident' was the classic arcing-ground fault! Such faults produce current-magnitudes well below Phase-to-Ground expected Irms values. Several facts lead to my conclusion: A) The current-magnitude (or duration) was sufficient to produce the conditions observed...

Broner... one last question: 11) I presume that all amp readings you provided are based on primary currents... not CT secondary currents. If the latter, then I need CT ratios! Phil

Asif... repeating an earlier Caveat, "I don’t accept anonymous requests for information; something to do with the fact that anonymity breeds boorishness!" Therefore, as a common courtesy I ask you provide your company affiliation, title or job function, and your location! I will...

Asif... since Bruce's Referenced Document also uses the SB Griscom Model, contact me for a copy! Regards Phil Corso [ [email protected] ]

Ronald... You said the neutral was solidly-grounded, but I believe you were referring to the Wye or 230kV-side of the GSU. Additional questions: 8) Is the 15kV system grounded via the Generator-neutral? If so, how... NGR, NGT, other? 9) Although no current-related relays operated, do...

Bruce... if you want the Westinghouse T&D version contact me at: [email protected] Phil.

Bruce... The Mechanical Analogy you alluded to was devised by Prof S.B. Griscom in 1926. A description can be found in the Westinghouse Transmission and Distribution Reference Book, ca 1950! It's discussed in: http://www.control.com/thread/1259307998

Adel... A transformer's required rating is always given in MVA, never in MW. Also, Power Factor is never listed in the xfmr's Nameplate as a design rating! As an example, consider the two operating conditions you cited: a) For a contracted capacity of 500MW @ 0.80 PF, the xfmr's capacity...

Adel... I’ve interpreted your query as two-fold: 1) Why is the Point-of-Delivery (PoD) on the Utility side of the GSU Xfmr, and not on the Supplier side; and 2) How does a change of Power-Factor impact the situation? The answer to the first question has to do with ownership of GSU power...

Ronald... if you prefer you can Off-Forum at: [email protected] Furthermore, if you agree, I will furnish details of any findings/conclusions, to this forum! Regards, Phil

Ronald... 7) What was the minimum current and time-setting of any of the current-sensing relays, i.e., the 51, 51G, 87B, 87T? Phil

Ronald... 5) What prompted the operator to trip the CB manually? Had he/she noted smoke, arcing noise, loud hum? 6) Was damage evident to any wheel or rail? Phil

Broner... thanks for info. Now can you provide some detail: 1) Which Protective device cleared the fault? 2) Was breaker "bottle" compromised? 3) Do you have photographs of the damage? 4) Is the breaker-enclosure mounted on a 'Roll-out' frame? Phil

Fluoronator... 1) Are the receptacles mounted in/on the truck powered by only the on-board generator? 2) Are the receptacles mounted in/on the truck powered by EITHER the on-board generator OR another-source remote to the truck? 3) Are you in a country complying with NEC or CSA...

Broner... it is apparent that only one of the three phases has faulted. Can you describe how the system-neutral is grounded? Regards, Phil Corso

Paru... do you know the sequence of tests? 1) Were the DBSD and CCD tests taken at the same? 2) Did both Contract Labs carry out the two tests at the same time? 3) Is it possible that an attempt was made to mitigate the condition between tests? 4) Have the same tests been carried out...

Scientif... to begin discussion: 1) Does "Island Operation" mean only combustion-EG's as power source? 2) Worst-case; Ball-Mill start with 7MW on-line, including SAG-Mill? 3) Is B-M an Induction mtr, with liq-starter connected to stator? 4) Is B-M a Wound-Rotor mtr, with liq-starter...

Paru... did both firms reach the same result, i.e., copper corrosion confirmed with DBDS test, but none using CCD test? Phil

Paru... you probably know that high oil or winding temperature is a precursor to evidence of DBDS! Was the high temp condition noted in the DGA test that preceded the DBDS test? Phil