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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...

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...

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...

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...

Hi all, If our plant is only 600V and is off-grid and supplied solely by 3 x 1200 kW Natural Gas Turbine Driven Generators at 600 V operating at 2 out of three at normal operations, do we need to perform dynamic or transient stability? All our motor loads are induction motors and large ones...

I would like to throw this question as all single phasing literature I read always presents blown primary fuses. What if: I have step-down transformer 69-13.8 kV and primary is DELTA protected by primary fuses and secondary WYE-Solidly grounded and is also protected by fuses (typical in a...

Hi all, One of distribution utility have a 115-69 kV three phase, wye (grounded) primary and wye (grounded) secondary step-down transformer with one 69 kV feeder line dedicated feeder connected to a nearby 69-13.8 kV delta primary-solid grounded secondary substation with further 13.8 kV feeder...

HI all, In one the facilities of our system, I can help notice this and took a photo. All three generators are running under-loaded and the power factor is 1.09 of one and around 0.50~0.51 on the other two. If these generators are running in load sharing mode, why are their kvars or kVA not...

In Canada wherein our area is subjected to -40 to -50 Deg C, The insulated single core GREEN earthing conductors from the transformer surge arresters to earth are installed hanging from top bracket to the surge counters with insulator support in between. I am wondering if this is in violation...

Hi all, I have this dilemma of a system for a 575 V, 3 phase pump motor with starter fed directly from a 600 V, 3 phase generator. The generator is rated 56 kW, 3 phase, 60 Hz but the generator circuit breaker is 200 AT MCCB, Square D type JD. The power cable between the generator and the...

HI all, We experienced two 600V ZCTs cracks which we strongly believe caused by freezing temperature (Canada). There were no evidence of human causes to them and we have coordinated with the transformer vendor to replace them with suitable ones for the application and conduct root-cause-failure...

We have a 200 A, 10 Seconds NGR applied into the 13.8/7.96 kV secondary wye transformer neutral. The CEC 2018 rule 10-308.1).e says that it will "BE SIZED TO CONDUCT THE RATED CURRENT OF THE IMPEDANCE GRODUNING DEVICE..." Does this mean that we would treat 200 A as continuous if the NGR is...