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Hi Cranky108, for temperature rise, the diferencial in Kevin or Celsius is the same. The Celsius and Kelvin scales increase by the same increments, meaning that to increase the temperature by 1°C results in the same increase of 1 K. The major difference is that when water freezes, a Celsius...

There are difference between IEEE STD and IEC STD associated to power transformer rating as shown on the table below. For a 100MVA unit with 30 degree C average ambient temperature in 24 hrs. What should be the maximum rating if specified per IEEE or the same maximum rating if designed based on...

For lightning protection with shield wire utility use bare OHSW or OPGW (Optical Grownd Wire)

From the legal standpoint, utility prefer to call the supply of electrical energy as a service since there is legal precedents to consider the electric energy provided after the meter as a product.

Can someone advise if the electric energy provided by a utility company is a service or a product? There is any difference if is at the generator, transmission, or distribution side? What about the battery energy storage system either residential or utility scale application?

Check for harmonics and higher-frequency noise, especially at the third harmonic. Those may be present in an electrical system and appear as fault current. Electrical noise is a growing problem as more users utilize variable frequency drives, inverters, battery storage/UPS, and even LED...

In general, cable size for grounding risers should be designed to withstand the maximum full current during the clearing time of the protective device without fusing, annealing the cable or creating a fire hazard. Determine the above parameters requires a good modeling technique considering that...

For the short lead time, check if a used transformer is an acceptable option. Some companies commercialize refurbish transformer but need to check for availability in the desire size.

Does anybody has a typical pole design dimensions for 13.8 kV similar to the one show below?

Kiribanda, Temporary Overvoltage (TOV) is a typical phenomenon accounted for in insulation coordination studies and is impacted by harmonic resonance. Modern modeling guidelines recommend a frequency scans form an initial screening process to identify and select relevant/onerous system...

Crshears, there is a typo. Instead light should be high. Following ANSI C84. 1-2020 defines high voltage as 115 kV to 230 kV, extra-high voltage as 345 kV to 765 kV, and ultra-high voltage as 1,100 kV.

There are two approaches for insulation coordination studies a) The conventional deterministic approach bases on empirical formulas to calculate conservative safety margin. b) The statistical or stochastic method using smaller time frames and frequency scan during the transient phenomena. The...

Thanks Waross, good advise. There is an interesting situation on most standards construction manual using normal and compact design for overhead MV designs. The compact design, use less clearance for voltage level. I having some difficulties to find standards for 13.8 kV but hoping that the 12.5...

It is safe to use a 12.47 kV design standard for a 13.8 kV overhead distribution system considering that both are within the traditional 15 kV ANSI class The application is for selecting overhead phase-to-phase or phase-to-ground clearances using an existing 12.47 kV design standard but at...

X0=0.85*X1 are reasonable results only for Dy connections

The surge arrester insulation withstand is easily misunderstood. For seal arresters, the altitude has negligible impact on the internal BIL, However, the altitude impacts the external surge arrester housing Arrester housing withstand values are not BIL; they are the voltage withstand of the...

[highlight #FCE94F]Because it is the code[/highlight] Hi Waross, I'm not sure of the CA code, but the NEC in the US is not mandatory for voltage drop issues and electric utilities are legally exempt from following the NEC. The voltage issue is not a code violation but rather an efficiency...

Hello Parchie, we understand the operation efficiency. The one issue that I am not sure about is why to maintain 3% in a branch circuit if we meet the maximum voltage drop at the load side. Let's illustrate that with another example: - Branch circuit: from the transformer to the main...

The NEC recommends a maximum voltage drop (VD)of a total of 5% across feeders and branch circuits, and 3% across the branch circuit alone implying 2% on the load circuit. Since most loads can operate efficiently at 95% of the nominal nameplate voltage, what is the relevance of meeting the 3%...

Does any one know the typical lead time to order a large power transformer such as 1000 MVA, 500 kV?