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Magnum PXR applications
MAGNUM PXR PRODUCT GUIDE
PA013006EN September 2022 www.eaton.com
5
Low voltage high resistance ground
fault sensing
Where continuity of service is a high priority, high resis-
tance grounding can add the safety of a grounded system
while minimizing the risk of service interruptions due to
grounds. The concept is a simple one: provide a path for
ground current via a resistance that limits the current
magnitude and monitor to determine when an abnormal
condition exists. This provides for maximum continuity
of service, because no tripping occurs for the resistance
limited ground fault.
The flexibility of the Magnum PXR circuit breaker is the
right product to provide the protection and coordination
that is required for maximum uptime. The Main breaker
in the scheme below can be equipped with a Source
Ground sensing scheme using an external CT around the
grounding rod from the high resistance grounding resistor.
The Magnum PXR trip unit ground fault settings capabil-
ity include pickup levels and time delays up to 1 second
that allow downstream feeder devices to isolate the fault
and allow continuity of service to the other feeders. The
Magnum PXR trip units also have the capability to provide
Zone Selective Interlocking on ground fault protection. This
allows the branches to restrain the upstream feeders or
mains when a ground fault is detected. Alternatively, all
the ground fault protection trip units can be configured for
alarming only on ground faults. This allows for the continu-
ity of service while a HRG pulse module can be used to
locate the source of the ground current path.
Ground fault provisions and protective schemes
Ground fault sensing options and zone selective
interlocking schemes relative to PXR trip units are
offered here as a general introduction. For more detailed
information and applicable wiring diagrams, refer to trip
unit manual MN013015EN.
As a standard feature, Magnum circuit breakers are inter-
nally wired with provisions for ground fault protection. If
ground fault is ordered on the breaker the desired opera-
tion can be field selected. It can be set to alarm or trip in
the presence of a ground fault condition, or it can be shut
off.
Ground fault protection can be added to breakers not
originally equipped with a ground fault trip unit. This can
be accomplished by simply replacing the existing trip unit
with a like model trip unit that has LSIG protection and
additional sensors as required for the application.
To provide for maximum application flexibility, breaker
ground fault provisions are wired out to the breaker
secondary terminals for external use. The secondary
terminals can be easily configured to accommodate the
most common ground fault schemes.
Figure 79. Different ground fault sensing techniques
for a typical 4 wire power system
Figure 78. Low voltage high resistance ground fault
sensing diagram