Power vs Distribution transformer 1

[Inspector4EI]

According to the NETA standards, the allowable power factor for a power transformer is .5% and 1.0% on a distribution transformer. What is the differance between power and distribution? Is a power transformer anything over 5000kva or is it the shape of the transformer?

 

[electricpete]

Most standards distinguish based on KVA rating with 500 kva being the cutoff as you suspected.

There are some who prefer to interpret it based on the function. A transformer in the generation or transmission system would be a power transformer and a transformer in the distribution system would be a distribution transformer.

Some excerpts from ELECTRIC POWER TRANSFORMER ENGINEERING, published by CRC press 2004 follow:

2.2.1.3 What Is a Distribution Transformer?
Just like the transformers in the Great Barrington system, any transformer that takes voltage from a
primary distribution circuit and “steps down” or reduces it to a secondary distribution circuit or a
consumer’s service circuit is a distribution transformer. Although many industry standards tend to limit
this definition by kVA rating (e.g., 5 to 500 kVA), distribution transformers can have lower ratings and
can have ratings of 5000 kVA or even higher, so the use of kVA ratings to define transformer types is
being discouraged (IEEE, 2002b).

2.1.1 Introduction
ANSI/IEEE defines a transformer as a static electrical device, involving no continuously moving parts,
used in electric power systems to transfer power between circuits through the use of electromagnetic
induction. The term power transformer is used to refer to those transformers used between the generator
and the distribution circuits, and these are usually rated at 500 kVA and above. Power systems typically
consist of a large number of generation locations, distribution points, and interconnections within the
system or with nearby systems, such as a neighboring utility. The complexity of the system leads to a
variety of transmission and distribution voltages. Power transformers must be used at each of these points
where there is a transition between voltage levels.

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[AusLee]

From the same book, Point 9 of paragraph 3.10 "... High-BIL(basic insulation level) transformers require low winding power factors (<0.5%), while low-BIL transformers can tolerate higher winding power factors (<1.5%)."

 

[Zogzog]

If you look at the NETA spec (ATS or MTS) it defines the difference betwwen power and distribution xfers