UFC 3 -520-01
June 10, 2002
9-2.6.6 Evaluate the results to verify that the selected settings are acceptable.
Review the GFP and its coordination with other devices. Refer to ANSI/IEEE 242 for a
detailed discussion of GFP coordination.
Coordination Study Report.
9-2.7.1 The coordination study report demonstrates that the maximum possible
degree of selectivity has been obtained between specified devices, consistent with
protection of equipment and conductors from damage from overloads and fault
Include the following in the coordination study report:
A narrative describing the analyses performed, the bases and methods used, and
the desired method of coordinated protection of the power system.
Descriptive and technical data for existing devices and new protective devices
proposed. Include the manufacturers published data, nameplate data, and definition
of the fixed or adjustable features of the existing or new protective devices.
Documentation of the utility company data including system voltages, fault MVA,
system X/R ratio, time-current characteristic curve s, current transformer ratios, and
relay device curves and protective device ratings and settings.
Fully coordinated composite time-current characteristic curves for each bus in the
system, as required to ensure coordinated power system protection between
protective devices or equipment. Include recommended ratings and settings of all
protective devices in tabulated form.
The calculations performed for the analyses, including computer analysis programs
utilized. Include the name of the software package, developer, and version number.
PROTECTIVE RELAYS .
Protective relays are designed to provide various types of electrical
protection. Protective relays detect abnormal conditions and isolate these conditions
from the rest of the electrical system by initiating circuit breaker operation. If used,
protective relays will usually be located at the service entrance or at major load centers
in applications 480 volts and above. Relays are often provided as part of standby
Protective relaying is an integral part of electrical power system design. The
fundamental objective of system protection is to quickly isolate a problem so that the
unaffected portions of the system can continue to function, but also should not interrupt
power for acceptable operating conditions, including tolerable transients.