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

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Symbols

Neutral-unbalance relay between two polyphase systems

This form shows a current relay in the conductor that joins the neutral points of two star-connected polyphase systems. A familiar application is the double-star capacitor bank, where a CT in the link between the two star points detects unbalance caused by failed capacitor units.

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

A distinction that matters

This relay measures the link between two star points; a neutral-current relay measures one neutral path to earth or to the supply.

Full reference

Symbols

Neutral-current measuring relay

This relay form is used where a CT is installed in a neutral conductor or in the earthing connection of a transformer or generator star point. Current there indicates earth faults or, in four-wire systems, heavy unbalance and triplen harmonic loading, depending on where the CT sits.

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

A distinction that matters

A neutral-current relay measures one neutral path; a residual connection sums the three phase CTs to derive the same quantity.

Full reference

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