Product Overview 1-15
Ground Fault
In isolated or high impedance-grounded systems, core-balanced
current sensors are typically used to detect low level ground faults
caused by insulation breakdowns or entry of foreign objects.
Detection of such ground faults can be used to interrupt the system to
prevent further damage, or to alert the appropriate personnel to
perform timely maintenance.
The SMC-Flex’s ground fault detection capabilities require the use of
external sensor. Installation of this sensor allows the option of
enabling Ground Fault Trip, Ground Fault Alarm, or both.
For the 5…480 Amp devices, the recommended sensor is a Cat. No.
825-CBCT core balance current transformer for 1…5 A core-
balanced ground fault protection.
For the 625…1250 A devices, the recommended sensor is shown
below and provides 5…25 A core-balanced ground fault protection.
• Manufacturer: Allen-Bradley
• Description: 600 Volt-Rated Current Transformer
• Catalog Number: 1411-126-252
• Ratio: 2500:5
Figure 1.17
➀ Customer supplied.
➁ Cat. No. 825-CBCT or Flex-Core Cat. No. 126-252
Note: When connecting the ground fault sensors, the secondary of
the CT should be shorted until the connection to the Flex
control module is completed.
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