TB
Relay test block
Multi-pole test facility between CT, VT and trip wiring and a relay, allowing safe isolation and test injection.
Schematic
Symbols · TP
Test plug
Plug inserted into a test block or switch to connect test equipment to the relay side while isolating the plant side.
In plain English
What does Test plug mean?
A test plug fits into a test block or test switch and brings each pole out to test leads. Depending on its design it can connect test equipment to the relay side only, or link plant and relay sides through an ammeter for in-service current measurement.
A simple example
Different plug types for the same block do different things, so the procedure must name the plug variant. The symbol shows the plug's poles but not its internal links, and using the wrong plug can open a live CT circuit or leave a trip output connected.
What the drawings help you do
Check which plug variant the procedure requires. Read the internal links of each pole. A test plug is the removable part; the test block or switch is the fixed part wired into the circuit.
This particular reference
Plug inserted into a test block or switch to connect test equipment to the relay side while isolating the plant side. A test plug is the removable part; the test block or switch is the fixed part wired into the circuit.
- Coil
- A wound conductor that can produce a magnetic field when energised.
- Signal
- Electrical information passed between devices, rather than necessarily the main power supply.
- Rating
- A value stating the conditions for which equipment is specified.
Read the source: Transformer terminals for measuring and test circuits
Schematic · TP
What it represents
A test plug fits into a test block or test switch and brings each pole out to test leads. Depending on its design it can connect test equipment to the relay side only, or link plant and relay sides through an ammeter for in-service current measurement.
Different plug types for the same block do different things, so the procedure must name the plug variant. The symbol shows the plug's poles but not its internal links, and using the wrong plug can open a live CT circuit or leave a trip output connected.
How to read it
- Check which plug variant the procedure requires.
- Read the internal links of each pole.
Information to show or reference
- Name plug variant
- Show internal links
- Match pole numbers to the block
A distinction that matters
A test plug is the removable part; the test block or switch is the fixed part wired into the circuit.
Sources you can follow
These public references support the explanation and provide further detail. Their graphics and downloadable files remain with their publishers.
Transformer terminals for measuring and test circuits
Public manufacturer range of transformer and test terminals for measuring and protection circuits.
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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