charts or access to the recorder mechanism. The chart drive motor shall
drive the chart through suitable reduction gearing and shall have
sufficient torque to start the chart when operating on 80 percent of its
rated voltage. The motor control switch shall be located [within the case
so that it can be conveniently reached to start or stop the motor] [_____].
A recorder operation selector switch shall be interlocked with its
associated medium-voltage circuit breaker to allow either continuous
operation of the instrument or automatic isolation of the instrument when
the circuit breaker is in the tripped or test position.
2.7.8.4
Transducers
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NOTE: Transducers will be specified only when
remote metering is required.
Watthour, varhour, watt, and varmeters and
transducers will be specified as 2, 2-1/2, or 3
element devices as follows:
a. Two element if used on a 3-phase, 3-wire system
serving only balanced 3-phase load (requires 2-VTs).
b. Two and one-half element if used on a 3-phase,
3-wire system serving single-phase-to-phase loads
(requires 2-VTs)
c. Three element if used on a 3-phase, 4-wire
system (requires 3-VTs).
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Transducers may be integral with an instrument or may be a separate unit
and shall be of the [unidirectional] [bidirectional] constant-current type
providing an analog signal directly proportional to the instantaneous
quantity measured. Ratings at 60 Hz shall be for a 120-volt nominal input
voltage, a 150-volt overload voltage, a 5-ampere nominal input current, a
10-ampere continuous overload current, a 250-ampere 1-second instantaneous
overload current, and provide an accuracy of plus or minus 0.5 percent.
The maximum individual instrument transformer burden shall not exceed 4
volt amperes. Output at full scale shall not exceed one mA.
2.7.9
Accumulative Meters
Accumulative type meters shall be provided as shown to measure real [and
reactive] power consumed, and shall be rated for use with instrument
transformers shown. [Meters shall be equipped with demand pointers.]
[Compensators or phase-shifting transformers shall be provided for
instruments used to measure reactive power.] [Meters shall be equipped
with detents to prevent negative registration.]
2.7.9.1
Construction
Meters shall be of the semiflush, back-connected, dustproof, drawout
switchboard type. Cases shall have black finish and window-type removable
covers capable of being sealed against tampering. Meters shall be of a
type that can be withdrawn, through approved sliding contacts, from fronts
of panels or doors without opening current-transformer secondary circuits,
disturbing external circuits, or requiring disconnection of any meter
leads. Necessary test devices shall be incorporated within each meter and
SECTION 16311A
Page 49
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