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31
Installation
01.4IB.51000C
Figure 23 Bar-Type Current Transformer Joint
Insulation
Pre-Insulation Epoxy insulation
Thermoplastic Sleeving or
Tape Insulation
“D”
“A”
“B”
1/2 LAP
“C”
.50 (12.7)
Min
.75 (19.11)
Min
RB Putty *
C.T.
Table J Bar-Type Current Transformer
Joint Insulation
Insulation
Level
(kV)
Inner
Filler
“A”
Outer
Wrap “B”
“C”
(inches)
“D”
(inches)
Approx. No. of Rolls
per Joint of HV
Tape ∆
2” or 3”
Bars
4” or 6”
Bars
5 or 15
3 Layers
HV Tape
∆
2 Layers
HV Tape
∆
3
3
‡
1/2 Roll HV
Tape
∆
11/2
Roll HV
Tape
∆
Note:
* Electrical grade rubber base putty
0282A3529P008 in roll form will be
used to grade voids and smooth out
sharp edges of joints. This putty has
no insulation value.
1 roll is 1/8” x 1½” x 5’ long.
‡ Insulate as far as possible. Do not
cover polarity marks.
∆ HV Tape 0282A3529P004 roll is
.030” x 2” x 30’ long. Apply with
mastic side down.
n. G
rounD
f
Ault
c
urrent
t
rAnSformerS
(W
InDoW
-t
ype
)
Window-type current transformers are
furnished where specified for sensitive
protection against ground faults. These
transformers are normally installed in a
horizontal position directly above or below the
primary cable terminals, so that the primary
cable or cables can pass through them. One
transformer is required for each three-phase
circuit.
Where armored cable is used, the armor must
be terminated and grounded before the cable
passes through the transformer. Armor clamps
are furnished for this purpose when specified.
When lead or other conducting sheath cable,
or cable with shielding tape or braid is used,
it is recommended that the sheath or shield
be grounded solidly to the switchgear ground
bus. The ground lead should be bonded
to the sheath or shield on the side of the
current transformer away from the primary
terminals. In cases where the ground cannot
be applied before the cable passes through
the transformer, bond the lead to the sheath
or shield between the transformer and the
primary terminals. The ground conductor
must then be passed back along the cable path
through the current transformer before being
connected to the ground bus.
Where potheads are used in units provided
with ground fault current transformers, the
pothead mountings must be insulated from
ground.