I have a customer with 480Y/277V transformer secondary and has installed Form 35S meter with 2CT's and no PT's. Meter is Elster A3 solid-state. The equipment end use is a PV inverter which is 3-wire, but the transformer is 4-wire, so I feel this should be 9S and not 35S. In addition they...
We have a 23kV 3-phase 3-wire system to be metered. The only available PT's are single bushing. Would it be accurate to install these in an un-grounded wye connection on the primary side and a grounded wye connection on the secondary side and use a three-phase 4-wire metering set-up? I know...
I have a service to a building with a conventional 120/028V, three-phase four wire service. There is a sub-panel being installed to a separate structure, and being fed overhead by quadraplex secondaries on poles (3-phase conductors and bare neutral supporting messenger).
The question is a...
I have a NEC question. We are installing a new electrical service and panel (outdoors) for a lighting project. The service is single-120/240V and is grounding at the service entrance (outdoor cabinet, panelboard, utility meter) via 2 ground rods. A grounding conductor is run with each branch...
Can anyone tell me if there is a requirement in the 2008 NEC (because I can't find one) that requires a metal chain link fence to be grounded with an intentional ground rod, etc. under the following situation. There is an existing million+ gallon municipal water storage tank on a site. There...
Is anyone well enough versed in NFPA-70E to answer this? Is it required for HRC2 (8 cal/cm2) PPE that 2 layers be worn? Can a single layer of 11 cal such as a coverall be worn, or is some type of cotton undergarment or cotton layer required. My understanding was that HRC 2 needed 2 layers to...
Can anyone point me to the calculations need to set a transformer 87G differential ground relay? I have a customer with a nuisance trip and we believe it is set too low. I'm looking for a good explaination of the calculation. It's a delta-wye substation transformer 69kv-13.8kv, 18MVA.
Does anyone have any good articles, or links to basics of cathodic protection of ductile iron water pipe running perpendicular under a 115kV transmission overhead right of way??
Can anyone point me to a good link with the formulas or a spreadsheet that would be helpful in calculating transient, subtransient, etc. generator paramenters for induction generators. I have some work for a number of generators in the 100kW range and want to verify some vendor information and...
Does anyone have a good link for a paper, article, reference giving a simple discussion of utility overhead distribution protection, particularly related to transformer and line fusing on overhead systems. I'm looking for a good reference for the technically challenged.
Here is a good one. A large warehouse had high bay 400W MH lights that randomly go out, either one row, a few fixtures, or the whole place. The problem is they take 15 minutes to cool down and restrike. None of the fluorescent lights go out, or any other equipment. There is lots of motor...
So my client wants to back-feed a 1000kVA transformer (13.8kV-480V) from the 480V side, to re-power a piece of equipment (connected off the 13.8kV side), and has asked what size circuit breaker would be needed to not trip on inrush. That transformer is about 1200A full load at 480V, and the...
Has anyone seen, or have a spreadsheet or free software to calculate ground grid resistance for a ring of ground rods around a (wind) tower foundation? I have the formulas for multiple rods in a straight line. I want to try several different configuration for a given soil resistivity and depth.
I apologize in advance if this has been answered before. I searched but did not find anything similar. I have a customer with a very old 1500kVA transformer (13.2kV-480V) delta-delta, with a true 3-wire delta service to their manufacturing facility. The transformer is being changed, but the...
So a contractor says he measured about 80V AC on the DC battery ground bus (I believe it is 48VDC battery system) for a good size college data center. I'm not sure where the reference for the measurement was made. Anyone ever heard of something similar??
I hate to ask, but I'm on short notice, does anyone have a good list of unit price line items, for typical overhead utility line construction work. I'm trying to put together a comprehensive list of unit-priced task for a distribution construction contract, and I think I'm missing some stuff...
Does anyone have or have knowledge of pdf versions of G.E. instruction books for older electro-mechanical protective relays. I'm looking for the following books:
Relay/Inst. Book
12IAC54A101A / GEH-1788
12STD15B3A / GEK-7362
12PVD11C11A / GEH-1770
Any help would be greatly appreciated.
Does anyone have experience designing wind turbine interconnections? My experience with generator step-up transformers is to have a delta-wye, with the delta on the generator side, and a wye on the utility side. One of the leading turbine manufacturers is proposing a wye-wye transformer...
I am looking for people's experience with data centers, in regards to the grounding of rack enclosure cabinets. I have a customer you has lost several power supplies. The utility service ground is fine (less than 1 ohm), as is the panelboard grounds for the circuits feeding the racks sitting...
Does anyone know of a simple, free program for calculating transmission line parameters, ampacity, etc.?? I have one that is part of a software suite, but an looking for a freeware type of program to be able to share with a client. Thanks
