1–3
Introduction – 1
•
the 51 voltage control and voltage restraint
functions are disabled
•
the access code feature is disabled
•
options supplied with the equipment are noted
on the yellow or pink (50 Hz) tag. These
are:
phase directional overcurrent function
(device 67)
input voltage (120 V ac, 125 V dc,
48 V dc, 24 V dc)
neutral current input (nominal 5 A or
1 A)
•
a set of replacement fuses is attached to
one of the handles. These fuses are mounted
on the internal PC board.
1.4
Description
The M-0420 Multifunction Relay is a
microprocessor-based unit that uses digital signal
processing technology to provide 14 different
protective relaying functions (see Table 1-1) in
one compact unit. The M-0420 is designed to
provide these functions in two basic applications:
generation, and generator/system interties. Within
these basic applications, the various devices in
the M-0420 can provide protection in cases of
islanding, ferroresonance, ground or phase faults,
generator motoring, and other abnormal operating
conditions. Internal relay functions are listed in
Table 1-1. The nomenclature follows the standards
of ANSI/IEEE Std. C37.2-1979, Standard Electric
Power Systems Device Function Numbers.
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9
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1
8
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1
8
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6
n
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*
Table 1-1
M-0420 Device Functions
Summary of Contents for M-0420
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