4. Tap ratings may vary from those indicated,
especially in lower kVA ratings.
5. Energy efficient transformers usually have
impedance values in the range of 2.95 to 5.75
percent. Perform fault current calculations to
determine minimum acceptable transformer impedance.
Be sure that specified impedance is available in the
size and type transformer required.
6.
Delete inapplicable sound levels.
7. Delete last sentence, referring to removable
ground strap, if transformer secondary winding is
delta type.
**************************************************************************
IEEE C57.12.00. [Oil-insulated][Less-flammable liquid-insulated], two
winding, 60 hertz, 65 degrees C rise above a 30 degrees C average ambient,
self-cooled type.
2.2.3.1
Transformer Ratings
a.
Transformer shall be rated [_____] kVA, [_____] kV BIL primary, [____]
kV BIL secondary.
b.
Transformer voltage ratings: [_____] V - [_____] V.[ For GrdY - GrdY
transformers, provide transformer with five-legged core design for
third harmonic suppression.]
c.
Provide four 2.5 percent full capacity taps, two above and two below
rated primary voltage. Provide tap changer, with external,
pad-lockable, manual type operating handle, for changing tap setting
when the transformer is de-energized.
**************************************************************************
NOTE: Change 85 degrees C to 75 degrees C when
transformers are specifically rated for 55/65
degrees C rise.
**************************************************************************
d.
Minimum tested impedance shall not be less than [_____] percent at 85
degrees C.
e.
Audible sound levels shall comply with the following:
kVA
DECIBELS (MAX)
225
55
300
55
500
56
750
58
1000
58
1500
60
2000
61
2500
62
5000
65
7500
67
10000
68
SECTION 16361N
Page 18
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