shall provide means for testing either from an external source of electric
power or from associated instrument transformers.
2.7.9.2
Ratings
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NOTE: Coordinate with paragraph Transducers.
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Meters shall be [_____]-stator, three-phase, [_____]-wire, [_____] element
rated for 120-volt, 2.5 ampere, 60 Hz ac operation calibrated for use with
associated instrument transformers. Meters shall have primary-rated,
direct-reading registers with not less than four dials. The register
multiplying factor shall be [_____]. Demand meters shall have [15-minute]
[[_____]-minute] demand registers.
2.7.9.3
Adjustments, Registration Errors, and Other Requirements
Calibrating adjustments for light load and for full load shall be of the
micrometer type, and adjustable from the front of the meter. Adjustments
shall be provided for power factor and torque balance. The periphery of
the discs shall be provided with standard notching to permit direct
comparison with a stroboscopic type standard meter. Potential indicating
lamps shall be provided in the potential coil circuits. The current coils
shall be capable of withstanding the mechanical and thermal stresses
imposed by a current 35 times normal applied for at least 0.5 second. The
registration errors of a meter for both unity and 50 percent lagging power
factor shall not exceed those listed below when tested at rated voltage,
frequency, temperature, and full load current, except as otherwise stated.
a.
Errors due to applied current shall be not more than 1 percent at
10 percent to 50 percent of the rated current and 0.5 percent at
50 percent to 150 percent of the rated current.
b.
Errors due to applied potential shall be no more than 0.5 percent
over a range of plus or minus 10 percent of the rated voltage.
c.
Errors due to applied frequency shall be no more than 0.004
percent between 59 and 61 Hz.
d.
Errors due to a change in ambient temperature shall be no more
than 0.5 percent over a range of 20 to 40 degrees C 64 to 104
degrees F.
2.7.10
Test Blocks and Accessories
Test blocks and their associated testing accessories shall be provided for
testing of instruments and protective relays that require periodic testing
or calibration in-place, but which are not equipped with integral testing
features. Test blocks with covers shall be mounted near the base of the
switchgear unit beneath the devices to be tested, and shall be provided
with a nameplate engraved to identify individual current or potential test
blocks, or a combination current/potential test block, as applicable.
Combination test blocks shall not exceed 10 poles. Current test blocks
shall be the short-circuiting type. Test devices shall be provided for
insertion into the associated test block to permit application of the
proper current or potential source for testing and calibration. Test
devices shall be rated not less than 20 amperes and 125 volts dc.
SECTION 16311A
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