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Anonymity is nothing that one should be berated or chastised about. I am quite sure that few of you "SIS Listers" know that the IEEE Standard 500-1981 (not sure of the date) related to the gathering of failure-rate data for the nuclear industry, was developed anonymously. BTW, I agree with Mr...

Responding to Hakan Ozevin's comments on the subject: Of course there are many variables to consider, but the following illustrates that the comparable losses of both the 10 and 60 hp motors are NOT "almost the same". Neglecting your reasoning for using the larger motor, and assuming you are...

We've proceeded far beyond the original query. However, Vitor Finkel's response reminded me of a study I once conducted years ago. It was for an LV distribution system major-size oil refinery of the future. I chose 831Y/480 Volts based on what was then available as 'optional' equipment in the...

Correction to my Fri, Mar 16, 3:44pm response to Bill Mostia: Third paragraph, last (long) sentence: Change "the LLG is more... to "the SLG is more..." Regards, Phil Corso, PE (Boca Raton, FL)

Responding to Bill Mostia's Thu, Mar 15,1:34pm requesting additional detail. We're getting well beyond "Elecricity for the Uninitiated", but I'll try. There are many types of electrical failures in a 3-phase system: SLG (single-line to ground); LLG (double-line to ground); LLS (line-to-line...

Responding to Steve. Myres, PE, Thu, Mar 15, 4:57pm message: Although the merits of higher voltage AC systems have been covered, there is a more insidious side... AC devices are not very forgiving of momentary power supply interruptions. Looking at it from a susceptibility standpoint: DC...

In response to Bill Mostia's Tue, Mar 13, 10:32am comments on the subject: Your scenario describing a double line to ground (LLG) fault is based on two assumptions: a) ground capacitance is zero; and b) the MOV''s are triggered into conduction at the phase to phase voltage value. Consider, as...

Further to my earlier dissertation on the scenario presented by Ken Brown, i.e., 'MOV destruction in a VSD system'. I neglected to explain the part that the MOV's play. Triggered by the blown fuse, overvoltage causes the phase to ground MOV's to conduct. Essentially, they try to discharge the...

In response to Gerald Beaudoin's comment about ground fault detection (GFD) on plant's service: Tripping of the service GFD should only occur for two "ifs": a) If the fault occurs between the service and a downstream branch circuit or feeder GFD. b) If it provides backup for faults that the...

In response to Christian Felde's first question: Left-side driving is related to the location of the sword carried by the knights of old. Got the above from a book about "imponderables!" Regards, Phil Corso, PE Trip-A-Larm Corp (Deerfield Beach, FL)

The Physics of... Power Semiconductor Protection Additional information related to the recent failure described by Gerald Beaudoin has prompted me to provide this update. The drive was not running. In other words, only the AC to DC rectifier section of the VSD was energized. Essentially...

Some additional tips/comments regarding seemingly "unrelated" or "head scratching" types of electrical failures: The third most costly (and most common) type of electrical failure involves premature operation of low-voltage fuses. This can occur in either the distribution feeder (G. Beaudin's...

Further to my earlier response on the subject: 8) It is unlikely that operation of both intact-phase fuses was due to overload. Fuse clearing-time for an overload of the magnitude noted earlier (1.73 x ) is in the order of seconds. Furthermore, the "band" related to clearing time would preclude...

Responding to G. Beaudin's plight: You experienced the "classic" case of single-phase operation on a bank of three-phase electrical loads, all supplied from the same feeder. Each drive (as seen from the protective fuses downstream from the trough) is considered as an "equivalent" three-phase...

Post-fault (single-phasing) performance is dependent on pre-fault operating conditions. Please provide some detail so that a meaningful answer can be provided. Regards, Phil Corso, PE Trip-A-Larm Corp (Deerfield Beach, FL)

This thread subject is similar to those about politics and religion... I seldom "mix in!" However, you've hooked me. In my opinion, nay, experience... Legal ethics is an oxymoron. The litigation process is intended to fill, or keeps filled, the pockets of the 5th estate, ie, the legal beagles...

An aside to the legal discussion in this thread. Who gets sued has nothing, repeat NOTHING, to do with who is responsible? And yes, I'm screaming! Regards, Phil Corso, PE Trip-A-Larm Corp (Deerfield Beach, FL)

Eric, I may be stepping on someone trademark toe, but have you looked into 3M's "Twist & Flat" cable. It is installed as any round-type cable. However, at each connector location the insulation can be removed and the cable untwisted. At that point it becomes a flatribbon-type cable. Then...

Anyone believing that because it hasn't happened thus far, it won't happen at all, is making a serious error. I recall several mAjor catastrophes (by anyone's definition) caused by Radio Frequency Interference (RFI). Both AM and FM type transceivers were involved. The now defunct...