INFORMATION & REQUIREMENTS ELECTRIC SERVICE - NStar

SKETCH 25
Mounting Provisions and Dimensions For Metering Current Transformers
In Service Cubicles Rated 600 Volts, 1800 Amperes or Less
MIN. MIN. MIN. MIN.
4 1"
8 1" 8 1" 4 1"
2 2 2 2
CLEARANCE TO
NEAREST OBJECT
FIGURE 1 FIGURE 2
BUS SPACING
SIDE VIEW
IN CUBICLE
OF CUBICLE
1 1"
2
1"
1"
5 7"
8
SEE FIG. 3 & 4
7"MIN.
7"MIN.
1/4"-20 TAPPED HOLES
ON LINE SIDE ONLY,
AND ON NEUTRAL BUS
11"
2
1 1"
1"
2
1
2
ALL MOUNTING HOLES 9/16" DIA.
ACCESS DOOR
OF CUBICLE
7"
APPROX.
MIN.
7"
8 1"
2
INSULATED BUS
SUPPORTS
1 3"
4
10"
1 3"
4
ALL MOUNTING HOLES 9/16" DIA.
FIGURE 3 FIGURE 4
225A-1200A
(1400A TO
SWITCH OR C/B
1800A SWITCH
(WITH 1200A
OR C/B)
FRAME MAX.)
7"
8
SKETCH 25 (NOTES)
1. It is the responsibility of the customer to contact the Company for
proper dimensions and mounting provisions for each set of metering
current transformers.
2. Current transformers are to be supplied and mounted by NSTAR
on the bus, on the load side of the service circuit breaker or switch.
3. Current transformers are to be mounted on the face of the bus
toward the access door of the cubicle. If multiple busses are used,
spacers will be furnished & installed by the manufacturer.
4. No physical supports other than the primary terminals are required
for the current transformers.
5. The access door to the current transformer compartment must be
hinged and have a locking hasp for a padlock type seal.
6. Figure 1 shows a 4 wire-3Ø installation. On 3 wire – 3Ø & 3 wire –
1Ø installations, transformers are to be mounted on outside busses
only & filler bus for the common phase or neutral will be furnished &
installed by the manufacturer.
7. The manufacturer will furnish and install hex head machine bolts 1/2
inch – 13 thread, nuts, washers for current transformer mounting,
and 1/4 inch – 20 potential screws.
8. The cubicle should be located in the switch room where there is a
minimum clearance of 3 feet from the door of the cubicle to a wall
or other obstruction.
9. Meters are to be located on the outside of the building. A 1-1/2 inch
conduit for the secondary wiring will be required from the current
transformer location to the meter location. This conduit is not to
exceed 25 feet unless written permission has been obtained. A pull
string is required for wiring installation.
10.Line side bus must be clearly identified.
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