fault capacity at the power source or provide a
fault capacity on which he is to base his analysis.
Delete the unused option.
**************************************************************************
The time-current characteristics, features, and nameplate data for each
existing protective device shall be determined and documented. [The
Contractor shall coordinate with the [commercial power company] [_____] for
fault current availability at the site.] [The Contractor shall utilize the
fault current availability indicated as a basis for fault current studies.]
2.14.3
Single Line Diagram
A single line diagram shall be prepared to show the electrical system
buses, devices, transformation points, and all sources of fault current
(including generator and motor contributions). A fault-impedance diagram
or a computer analysis diagram may be provided. Each bus, device, or
transformation point shall have a unique identifier. If a fault-impedance
diagram is provided, impedance data shall be shown. Locations of switches,
breakers, and circuit interrupting devices shall be shown on the diagram
together with available fault data, and the device interrupting rating.
2.14.4
Fault Current Analysis
2.14.4.1
Method
The fault current analysis shall be performed in accordance with methods
described in IEEE Std 242, and IEEE Std 399.
2.14.4.2
Data
Actual data shall be utilized in fault calculations. Bus characteristics
and transformer impedances shall be those proposed. Data shall be
documented in the report.
2.14.4.3
Fault Current Availability
Balanced three-phase fault, bolted line-to-line, and line-to-ground fault
current values shall be provided at each voltage transformation point and
at each power distribution bus. The maximum and minimum values of fault
available at each location shall be shown in tabular form on the diagram or
in the report.
2.14.5
Coordination Study
The study shall demonstrate that the maximum possible degree of selectivity
has been obtained between devices specified, consistent with protection of
equipment and conductors from damage from overloads and fault conditions.
The study shall include a description of the coordination of the protective
devices in this project. Provide a written narrative that describes: which
devices may operate in the event of a fault at each bus; the logic used to
arrive at device ratings and settings; situations where system coordination
is not achievable due to device limitations (an analysis of any device
curves which overlap); coordination between upstream and downstream
devices; and relay settings. Recommendations to improve or enhance system
reliability, and detail where such changes would involve additions or
modifications to the contract and cost changes (addition or reduction)
shall be provided. Composite coordination plots shall be provided on
log-log graph paper.
SECTION 16311A
Page 66
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