Hi Rockman, in your initial post you mentioned that the electricity is a flow of electrons, but in reality is not the case.
The electron drift velocity in a conductor is very slow where the average speed at which electrons travel in a conductor when subjected to an electric field, is about 1mm...
The optimal approach in the ideal world is to have a dedicated unigrounded system. Most distribution systems in the USA are arranged as a multi-grounded system similar to the picture below where not only the equipment (transformers, surge arrester, etc) are grounded but also the neutral is...
Hi Gr8blu,
Thanks for your input. Regarding the transformer design, both of us share the same idea that the one built per IEC need to be derated for operating average temperature above 20 oC that impact the hot spot limit of 98 oC by the standard while the one built per IEEE STD are more robust...
To facilitate the discussion of this interesting topic, enclosed is a graph with our interpretation of the transformer loading capability for normal operating conditions ONAN
& ONAF. The IEEE data is based on the reference in the curves and the IEC data is based on the table provided in the...
How it can be explained that transformers built per IEEE can be overloaded up to 200% and the one built per IEC only 150% as indicated in the table below. Considering this data along, we can infer that IEEE is built somehow stronger than the IEC and for the same price y will be incline to...
Hi PRC, I hearing what you said and thanks for your input. We are investigating the actual net rating of Power transformer operating in a tropical country with a fairly stable hot temperature with an average of 32 degree Celsius in contras with countries with cold winters and summers with...
Yes, we can agree to disagree. Still, no response to the original question of whether or not a transformer built per IEC should be derated if operated above 20 C.
Several researcher consider that a transformer built per IEC should be derated if the transformer operate at ambient temperature...
Thanks, prc. I found another link that provides a dereating curve per the IEC Standard practice. The example shows that a 30 MVA transformer built per IEC an operated at a 30 ambient temperature is equivalent to a 27 MVA unit. Therefore, appears that the transformer built per the IEEE standard...
The IEEE C57.12.00-2000 standard, power transformers are rated at the average ambient temperature not to exceed 30 degrees Celsius in any 24 hours.
The IEC standard 60076-2 specifies 20 oC for the average annual temperature and 30 oC for the average monthly hottest temperature.
Both standards...
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...
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.
