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HI all, I have been a very good reader of a lot of post here and would like to extend my appreciation and thanks. I have been using IEEE 519 limits on the true PCC and we have always been compliant with it fortunately. However, I have also been trying my best to understand and been looking for...

HI all, I would like to obtain valuable inputs to my question and hope I am asking a generic one for my understanding. A three winding transformer have primary delta, secondary delta and tertiary wye-solidly grounded connected. Primary and secondary winding terminals are connected to separate...

HI all, I have been designing several industrial substations in the past and I always design the substation grounding mesh grid per IEEE 80 and as a "stand-alone" grounding grid. This means, I do not consider any bonding to the overall plant grid and design to be inherently safe and not rely to...

LionelHutz, can I compare to the total RMS Current (fundamental + harmonics) against derated cable ampacity (from temp, grouping plus 125% contingency) and breaker AT? Gr8blu, Will the specification of equipment or devices specify what or how much harmonic voltage and current they can...

Is it correct to make the following assumptions: 1. An 8.5% THD (volts) would mean 1.85% fundamental nominal voltage? 2. A 8.5% TDD (or THD (current) would mean 1.6% total maximum fundamental demand current Will the distribution equipment(say the MCC) pass rated maximum voltage and continuous...

Hi Kiribanda, thank you for your prompt response. I was referring to THD but will also consider TDD. ETAP have THD(I) which they have not changed by definition to TDD. I agree with you on the reference PCC. Based on my understanding, I am aligned with you on the premise that the TDD and THD...

Hi all, I have 5 VFDs each with manufacturer test reported %THD content of 4.3% at 88% loading. IEEE std 519 requires total harmonic distortion of 8% and I am getting 8.6% THD at 80% VFD loading and 11% at 100% loading at the 600V MCC bus where all these VFDs are connected and this is the...

Hi all, We are extending an existing transformer yard which is going into the 3.0 PSIG blast radius from a nearby plant (200 ft). We are looking into placing blast walls but am curious if the post insulators, disconnect switches, liquid immersed power transformers can withstand that pressure...

Hi all, We have a strange condition wherein, our 600V switchgear power circuit breaker is tripping at no fault condition. Here is the current case: The switchgear is a main-tie-main with N.O. bus tie circuit breaker. The breaker is an 1600A K-Line breaker with solid state trip unit. The relay...

Kiribanda, its not HRG, its a resistance grounded system with an NGR rating of 200A

Installation and Maintenance Manual SSVT (IPC)https://files.engineering.com/getfile.aspx?folder=b279dca0-16f0-4b8d-b05c-c3aa82c907d4&file=SSVT.pdf

The design proposed to use 3 x ABB SSVT-350 (IPC) Voltage Station Transformers. A wye-neutral solidly grounded secondary winding is made by interconnecting the X2 terminals to ground and using the X1 terminals for the line conductors (see attached image). Each primary H1 terminals are connected...

I would like to know if I can operate the input of my VFD at 5~7.5% voltage drop. We have an electric dredge rated for 13.8 kV. The dredge has a small electrical room with 13.8 kV switchgear feeding a 13.8-4.16 kV VFD and a 13.8-0.6 kV stepdown auxiliary distribution transformer within the 13.8...

Hi all, We have a Siemens Perfect Harmony VFD feeding three motors rated 3 x 4,000 HP, 6.9 kV. The VFD is having isolation transformer with 12.5 MVA primary wye winding and 13 MVA secondary delta winding (18 x windings connected to individual power cells (6 windings per phase). The VFD...

Hi all, I would like to obtain technical opinion from folks here about the fact of installing TECK 90 power cables in cable cones normally used for portable trailing cables (used in mines). TECK 90 is an armored cable also suitable for direct burial and have sufficient strength to exposed...

I am actually speculating that the Low, Medium and High curves for induction motors to be as below: LOW - >50 HP but less than 250 HP MEDIUM - > 250 HP but less than 1000 HP HIGH - > 1000 HP But I do not have any standards reference for it so I am guessing

Thank you and the part on the transformer is clear to me now. This leaves my query on the X/R curves of the induction motors (and synchronous machines)...WHAT DO THE LOW, MEDIUM AND HIGH curves mean?

Hi all, In ANSI C37.010-2016, typical X/R ratios for transformers, motors and generators, are indicated in Figure 30, Figure 31 and Figure 32 respectively Pages 89-90. However the curves indicates "High, Medium and Low" and the standard did not specify what are the bases for using these curve...

Hi all, I would like to request any comments, experience or IEEE transaction paper title which help explain how to apply short circuit calculations using ANSI/IEEE (symmetrical, Peak, asymmetrical RMS) in terms of applying them to specify or review IEC make and breaking short circuit current...

Or probably the dynamic stability is needed between the two or three generators in parallel?