CT
Current transformer
A current-measurement transformer used with metering and protection equipment.
SLD / Schematic
Protection functions · 21
Distance protection
Uses measured voltage and current to assess an electrical distance or impedance characteristic.
SLD / Schematic · 21
What it represents
Uses measured voltage and current to assess an electrical distance or impedance characteristic.
In a drafting package, connect this reference to the protected line CT and VT circuits. The associated drawing should trace the distance zones and associated breaker trip paths; the number identifies the role and does not specify the terminal arrangement, ratings or operating settings.
How to read it
- Identify the protected line CT and VT circuits.
- Trace the distance zones and associated breaker trip paths.
Information to show or reference
- Label the protected line CT and VT circuits.
- Cross-reference the distance zones and associated breaker trip paths.
- Identify the device tag, manual revision and logic drawing that define this implementation.
A distinction that matters
Distance protection uses impedance-related criteria; directional overcurrent 67 uses current and directional supervision.
Sources you can follow
These public references support the explanation and provide further detail. Their graphics and downloadable files remain with their publishers.
ANSI device-number and suffix reference table
Public manufacturer number/name association. Drafting explanations are independently written.
IEEE C37.2-2022: power-system device function numbers
Normative device-number publication; exact edition wording and compliance require the licensed standard.
About this graphic
This illustration was authored independently by Elora Grid to explain the concept. It is not reproduced from a customer drawing, an official standard graphic or a manufacturer CAD file. Its correspondence to an exact IEC or IEEE symbol identifier has not been certified.
SVG and DXF downloads contain this original artwork. DXF uses unscaled drawing units; a GA envelope supplies no product dimensions, clearances or fabrication information. Original artwork is available under CC BY 4.0. Third-party references retain their own terms.
Explore related references
Put the reference into a drawing workflow.
Elora Grid helps electrical teams work with drawings, specifications and equipment information. Explore the drafting workflow or join the early-access waitlist.