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 · PTCB
Portable test-supply connection 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
Shows the assigned connection point for a separately controlled temporary test supply.
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 “Temporary test supply” at the input and “Defined test circuit feed” at the output. Backfeed prevention belongs to the test design.
What the drawings help you do
Start at the named input: Temporary test supply. Identify its source device or document and the state represented on the drawing. Follow the named output: Defined test circuit feed. Cross-reference its destination and separate the command from confirmation that the equipment responded.
- Input
- Temporary test supply
- Output
- Defined test circuit feed
- 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 · PTCB
What it represents
Shows the assigned connection point for a separately controlled temporary test supply. 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 “Temporary test supply” at the input and “Defined test circuit feed” at the output. Backfeed prevention belongs to the test design.
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: Temporary test supply. Identify its source device or document and the state represented on the drawing.
- Follow the named output: Defined test circuit feed. Cross-reference its destination and separate the command from confirmation that the equipment responded.
- Backfeed prevention belongs to the test design.
- 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 temporary test supply.
- Identify the destination and defined state of defined test circuit feed.
- Record the equipment or control-document revision supporting this functional block.
- Check this application limit in the project design: Backfeed prevention belongs to the test design.
A distinction that matters
Backfeed prevention belongs to the test design. 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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