TB
Relay test block
Multi-pole test facility between CT, VT and trip wiring and a relay, allowing safe isolation and test injection.
Schematic
Functional block · CCTB
Control-circuit continuity test boundary
Functional block · Switchgear
An independently authored application reference. The drawing shows the named function or circuit relationship; use the project legend and selected equipment documentation for its drafting form and connections.
Browse this installation focusIn plain English
What this block does
Identifies the defined terminals included in a control-path continuity check.
A simple example
In a switchgear relay panel, test links can separate a protective relay from the trip coils while maintaining the specified current-transformer secondary arrangement. For this reference, the drawing identifies “Test boundary terminals” at the input and “Observed path continuity” at the output. Continuity does not demonstrate loaded operating performance.
What the drawings help you do
Start at the named input: Test boundary terminals. Identify its source device or document and the state represented on the drawing. Follow the named output: Observed path continuity. Cross-reference its destination and separate the command from confirmation that the equipment responded.
- Input
- Test boundary terminals
- Output
- Observed path continuity
- Application reference
- An explanation of a named drawing function or circuit relationship; the project documents define the equipment and its connections.
Read the source: Masterclad medium-voltage switchgear: circuit-breaker section interlocks
Schematic · CCTB
What it represents
Identifies the defined terminals included in a control-path continuity check. A test interface separates measurement, command and indication paths so their behavior can be checked in the documented test configuration. The test boundary must show which real equipment outputs remain enabled.
In a switchgear relay panel, test links can separate a protective relay from the trip coils while maintaining the specified current-transformer secondary arrangement. For this reference, the drawing identifies “Test boundary terminals” at the input and “Observed path continuity” at the output. Continuity does not demonstrate loaded operating performance.
Trace the source and destination on each side of the test boundary. Use the selected test-device instructions for actual operations and never infer a safe current-transformer switching sequence from an educational diagram. The functional block is an independent explanation of this named application. Equipment-specific ratings, terminal connections and operating conditions must be established in the project documentation.
How to read it
- Start at the named input: Test boundary terminals. Identify its source device or document and the state represented on the drawing.
- Follow the named output: Observed path continuity. Cross-reference its destination and separate the command from confirmation that the equipment responded.
- Continuity does not demonstrate loaded operating performance.
- Trace the source and destination on each side of the test boundary. Use the selected test-device instructions for actual operations and never infer a safe current-transformer switching sequence from an educational diagram.
Information to show or reference
- Label the source and connection reference for test boundary terminals.
- Identify the destination and defined state of observed path continuity.
- Record the equipment or control-document revision supporting this functional block.
- Check this application limit in the project design: Continuity does not demonstrate loaded operating performance.
A distinction that matters
Continuity does not demonstrate loaded operating performance. 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.
Sources you can follow
These public references support the explanation and provide further detail. Their graphics and downloadable files remain with their publishers.
Masterclad medium-voltage switchgear: circuit-breaker section interlocks
Public technical context for switchgear test and commissioning interfaces. Breaker control, mechanism, position contacts, racking interlocks and test interfaces. The application text and educational graphic are independently authored; the publisher does not certify this representation.
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. Original artwork is available under CC BY 4.0. Third-party references retain their own terms.
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