Side-by-side reference

Understand the difference.

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

First referenceCompare with

ΣCT

Symbols

Summation current transformer

A summation CT has several primary windings, each fed from the secondary of a main CT, and one secondary winding that carries their sum. It lets one meter or relay see the total current of several feeders, or in some relay designs combines three phase currents into a single weighted quantity.

Drawing use: Schematic / SLD
Application: Metering & protection
Reference family: IEC / Manufacturer

A distinction that matters

A summation CT adds currents before measurement; a summation energy meter adds energy after measurement.

Full reference

Σ kWh

Symbols

Summation energy meter

A summation meter totalises energy from more than one circuit. It may count pulses from several transmitting meters or, in older schemes, be fed by a summation CT, and it appears where several incomers or feeders must be billed or monitored as one supply.

Drawing use: SLD / Schematic
Application: Metering & protection
Reference family: IEC / Manufacturer

A distinction that matters

A summation meter totals several circuits; a summation CT adds currents before measurement.

Full reference

Original educational previews. Follow the source references on each full entry for the appropriate standard or selected product.