Square D Current Transformer (CT) Installation Information
Issue
Customer needs basic installation and safety guidance for Square D / Schneider Electric current transformers (CTs), including polarity/orientation and safe handling of CT secondary wiring.
Product Line
Current Transformers (Square D / Schneider Electric)
Environment
Metering / Power Monitoring
Current Transformer (CT) installed on conductors/bus for metering or monitoring
Cause
Incorrect CT orientation (polarity), loose connections, or unsafe handling of the CT secondary (especially leaving the secondary open while primary current is flowing) can cause incorrect readings, equipment damage, and hazardous voltage conditions.
Resolution
Warning: Installation and maintenance of CTs and associated metering equipment must be performed only by qualified, competent personnel trained on electrical hazards and safe work practices. Failure to follow applicable instructions and warnings can result in equipment damage, severe injury, or death. Since these are broad instructions, please refer to the appropriate CT installation guide for your specific application.
- Verify CT polarity/orientation before energizing:
- For window-type CTs, install the CT so the marked polarity/source side (for example H1 or equivalent marking) faces the current source (line side), and the opposite side faces the load.
- Use the CT’s polarity markings on the secondary (for example X1 polarity terminal) to maintain correct metering polarity when landing secondary wiring.
- Do NOT open-circuit the CT secondary while primary current is flowing:
- Never disconnect the CT secondary leads (or leave them loose/unlanded) while the CT primary conductor is energized.
- If wiring changes are required, short the CT secondary first (using an approved shorting device/block) before disconnecting meter-side wiring.
- Check workmanship and connection integrity:
- Confirm all secondary wiring terminations are secure and tight.
- Confirm the CT is properly seated/closed (split-core) or properly installed (solid-core) and is mechanically secure per the CT style/mounting method.
- Post-install verification:
- After installation, verify readings are reasonable and consistent (for example, compare phases; confirm the expected direction/sign of power where applicable).
- If measurements appear incorrect, re-check CT orientation and secondary polarity wiring before assuming a device or meter failure.
- See the attached image for additional CT installation notes, polarity/orientation examples, and safety reminders.
- Complementary link: FA203850
See attached file for more details. (The file needs to be downloaded to open)