K
Neutral-current measuring relay
Measuring relay fed from a CT in a neutral conductor or star-point connection, responding to neutral current.
Schematic / SLD
Symbols · K
Neutral-unbalance relay between two polyphase systems
Relay form measuring current in a link joining the star points of two polyphase systems, such as split capacitor banks.
In plain English
What does Neutral-unbalance relay between two polyphase systems mean?
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.
A simple example
In a healthy balanced arrangement the link carries little current, so the relay setting is a small fraction of phase current and must allow for natural unbalance. The symbol does not tell you the alarm and trip stages or the compensation for inherent unbalance; those are in the bank protection settings.
What the drawings help you do
Identify the two star points joined by the measured link. Look for separate alarm and trip stages. This relay measures the link between two star points; a neutral-current relay measures one neutral path to earth or to the supply.
This particular reference
Relay form measuring current in a link joining the star points of two polyphase systems, such as split capacitor banks. This relay measures the link between two star points; a neutral-current relay measures one neutral path to earth or to the supply.
- Coil
- A wound conductor that can produce a magnetic field when energised.
- Phase
- One of the related AC waveforms in a power system.
- Rating
- A value stating the conditions for which equipment is specified.
Read the source: AutoCAD Electrical: Current monitoring relays · IEC graphical symbols for diagrams
Schematic / SLD · K
What it represents
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.
In a healthy balanced arrangement the link carries little current, so the relay setting is a small fraction of phase current and must allow for natural unbalance. The symbol does not tell you the alarm and trip stages or the compensation for inherent unbalance; those are in the bank protection settings.
How to read it
- Identify the two star points joined by the measured link.
- Look for separate alarm and trip stages.
Information to show or reference
- Show the interconnecting link and CT
- State alarm and trip settings
- Note inherent unbalance compensation
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.
Sources you can follow
These public references support the explanation and provide further detail. Their graphics and downloadable files remain with their publishers.
AutoCAD Electrical: Current monitoring relays
Public AutoCAD Electrical relay listing that names the In Neutral between 2 Multi-Phase Systems block; the illustration is independently drawn.
IEC graphical symbols for diagrams
IEC context for graphical symbols used in diagrams; no IEC graphic is reproduced.
About this graphic
This illustration was authored independently by Elora Grid to explain the concept. It is not reproduced from a customer drawing, an official standard graphic or a manufacturer CAD file. Its correspondence to an exact IEC or IEEE symbol identifier has not been certified.
SVG and DXF downloads contain this original artwork. DXF uses unscaled drawing units; a GA envelope supplies no product dimensions, clearances or fabrication information. Original artwork is available under CC BY 4.0. Third-party references retain their own terms.
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