2.13.2.5
Voltage Transformers
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NOTE: See TM 5-811-1 for guidance regarding voltage
transformer accuracies for metal-clad switchgear are
not listed in ANSI C37.20.2. Accuracy classes as
listed in IEEE C57.13 are 0.3, 0.6, and 1.2.
Standard burdens for each accuracy class are W, X,
Y, Z, ZZ, and M. The designer should check the
burdens connected to determine the actual accuracy
class and burden required. In general, ANSI C12.11
requires 0.3 accuracy class for up to Y burdens,
except for voltages of 5 kV and below. Where
metering potential transformers are provided, a 0.3
accuracy class should be specified, if available for
the voltage rating and burden needed.
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Voltage transformers shall have indicated ratios. Units shall have an
accuracy rating of [_____]. Voltage transformers shall be of the drawout
type having current-limiting fuses in both primary and secondary circuits.
Mechanical interlocks shall prevent removal of fuses, unless the associated
voltage transformer is in a drawout position. Voltage transformer
compartments shall have hinged doors.
2.14
COORDINATED POWER SYSTEM PROTECTION
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NOTE: The requirements for the studies in these
paragraphs depend on the complexity and extent of
the power system. Delete these requirements for:
projects of limited scope; projects having
which coordination is not possible (standard molded
extension of 600 volt level service to a building or
facility from an existing transformer (750 kVA or
less); or projects involving simple extension of 600
volt level service to a building or facility from a
The designer will be responsible for showing and
specifying the requirements for fuses, circuit
breakers, protective relays, or other protective
devices associated with the project. The protective
devices should be selected and specified to protect
electrical power system conductors or equipment
against sustained overloads, in-rush conditions,
electrical faults, or other abnormal power system or
equipment operating conditions, in accordance with
TM 5-811-14, IEEE Std 242, and IEEE Std 141.
The complexity and extent of coordinated power
system protection depends on the type of buildings
or facilities required, on the load demand of
facilities, and on the quantity and types of
facilities to be constructed. Facilities having a
relatively-low power demand (e.g., 2500 kVA or less)
SECTION 16475A
Page 27