Understand the difference.

Compare the meaning, drawing context and source references of two entries. A similar graphic or shared abbreviation does not establish equivalence.

SPRI

Symbols

Summated phase-current relay input

Connects the assigned phase-current quantities to the selected summation measurement function. A current-transformer secondary arrangement carries a measuring current from a defined primary location to metering or protection inputs. Core identity, polarity and the connected circuit determine the measurement's meaning.

Drawing use

Schematic

Application

Metering & protection

Reference family

Manufacturer

A distinction that matters

Calculated summation differs from a separate sensor. This reference describes the named application; it does not establish a new IEC graphical symbol, an ANSI device-function number or an exact manufacturer connection diagram.

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CT

Symbols

Current transformer

A current transformer produces a secondary current related to the current in its primary conductor. A drawing uses the CT representation to show where current is measured and which metering or protection circuit receives that measurement. It does not, by itself, specify the CT ratio, accuracy class, burden or secondary connection.

Drawing use

SLD / Schematic

Application

Metering & protection

Reference family

IEC / IEEE / ANSI

A distinction that matters

A CT measures current. A VT measures voltage. Their secondary circuits and isolation/testing arrangements are different.

Full referenceAdd to legend

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