25
Synchronism check
Checks documented synchronising conditions before a permitted connection.
Protection functions
The electrical reference
Read the protection code.
Understand ANSI/IEEE device-function numbers and common manufacturer suffixes for protection, switching and control. Find definitions, practical distinctions and supporting public references.
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1095 entries · Original illustrations
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
52
AC circuit breaker
The device-function number identifying an AC circuit breaker.
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
81
Frequency protection
A function responding to a documented frequency condition.
Protection functions
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Read the drawing, not just the mark
Small details. Different meanings.
Understand symbols, equipment tags and function numbers—and know when a generic object needs a manufacturer drawing.