with both time-delay and nontime-delay. RK5
provides moderate current limitation, time-delay
option.
**************************************************************************
Cartridge fuses, current-limiting type, Class [G] [J] [K] [L] [RK1] [RK5]
[RK9] [T] [CC] shall have tested interrupting capacity not less than
[100,000] [200,000] amperes. Fuse holders shall be the type that will
reject Class H fuses.
a.
Class [G] [J] [L] [CC] fuses shall conform to UL 198C.
b.
Class K fuses shall conform to UL 198D.
c.
Class R fuses shall conform to UL 198E.
d.
Class T fuses shall conform to UL 198H.
2.10.3.2
Transformer Circuit Fuses
Transformer circuit fuses shall be Class RK1 or RK5, current-limiting,
time-delay with 200,000 amperes interrupting capacity.
2.10.4
Instrument Transformers
2.10.4.1
General
Instrument transformers shall comply with ANSI C12.11 and IEEE C57.13.
Instrument transformers shall be configured for mounting in/on the device
to which they are applied. Polarity marks on instrument transformers shall
be visually evident and shown on drawings.
2.10.4.2
Current Transformers
**************************************************************************
NOTE: See TM 5-811-1/AF AFJMAN 32-1080 regarding
guidance on current transformers. Accuracy class
ratings of current transformers (CTs) at standard
burdens are listed in IEEE C57.13. The minimum
standard current transformer accuracies for
metal-clad switchgear are listed in ANSI C37.20.2.
In general, ANSI C12.11 requires a 0.3 accuracy
class for up to a B-0.5 burden, except for some 200
and 400 ampere units. Where metering current
transformers are provided, this accuracy class
should be specified, if available for the ampere
rating and burden needed. A "C" classification
means the ratio error can be calculated, whereas a
"T" classification is one which has to be derived by
testing. IEEE C37.20.2 permits either
classification up to the indicated ratings.
**************************************************************************
Unless otherwise indicated, bar, wound, or window-type transformers are
acceptable; and except for window-type units installed over insulated
buses, transformers shall have a BIL rating consistent with the rated BIL
of the associated switchgear or electric power apparatus bushings, buses or
conductors. Current transformers shall have the indicated ratios. The
continuous thermal-current rating factor shall not be less than [1.0] [1.2]
SECTION 16375A
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