CT
Current transformer
A current-measurement transformer used with metering and protection equipment.
SLD / Schematic
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Symbols, protection codes and equipment references for switchgear, switchboards, switchrooms and microgrids.
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1095 entries · Original illustrations
Metering & protection
VT / PT
Voltage transformer
A transformer providing a voltage signal for metering or protection.
SLD / Schematic
25
Synchronism check
Checks documented synchronising conditions before a permitted connection.
Protection functions
27
Undervoltage
A function responding to voltage below its configured operating criteria.
Protection functions
32
Directional power
A function responding to power with a specified direction and operating condition.
Protection functions
46
Current unbalance / negative sequence
A current phase-balance or reverse-phase function used in documented protection applications.
Protection functions
49
Thermal protection
A thermal protection function for a documented machine or transformer application.
Protection functions
50
Instantaneous overcurrent
An overcurrent function without an intentional operating time delay in its instantaneous application.
Protection functions
51
Time overcurrent
An overcurrent function with a documented time characteristic.
Protection functions
59
Overvoltage
A function responding to voltage above its configured operating criteria.
Protection functions
67
Directional overcurrent
An overcurrent function with a documented direction criterion.
Protection functions
79
AC autoreclosing
A function coordinating a documented automatic reclosing sequence.
Protection functions
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