GFM
Grid-forming inverter
An inverter controlled as a voltage source that sets its own voltage and frequency, able to energise and hold up an island.
SLD
Functional block · MFERG
Microgrid feeder energization readiness gate
Functional block · Microgrids
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
Checks the documented prerequisites before connecting the assigned feeder in a restoration stage.
A simple example
In a microgrid recovering from a blackout, an available grid-forming source can establish the assigned island reference before compatible generation and eligible load groups are introduced under the validated restoration strategy. For this reference, the drawing identifies “Feeder status and permits” at the input and “Feeder connection permission” at the output. A control permissive does not prove field isolation removed correctly.
What the drawings help you do
Start at the named input: Feeder status and permits. Identify its source device or document and the state represented on the drawing. Follow the named output: Feeder connection permission. Cross-reference its destination and separate the command from confirmation that the equipment responded.
- Input
- Feeder status and permits
- Output
- Feeder connection permission
- Application reference
- An explanation of a named drawing function or circuit relationship; the project documents define the equipment and its connections.
Read the source: Avista Shared Energy Economy microgrid protection and control case study
Schematic · MFERG
What it represents
Checks the documented prerequisites before connecting the assigned feeder in a restoration stage. Black-start and restoration control coordinates the establishment of an electrical reference and the gradual return of assigned resources and loads. A dead system, an available starting source and a successful load restoration are distinct states.
In a microgrid recovering from a blackout, an available grid-forming source can establish the assigned island reference before compatible generation and eligible load groups are introduced under the validated restoration strategy. For this reference, the drawing identifies “Feeder status and permits” at the input and “Feeder connection permission” at the output. A control permissive does not prove field isolation removed correctly.
Show the prerequisites and confirmation at each control boundary. These original explanatory blocks are not an operating procedure; energization, protection, transformer inrush and motor reacceleration require system-level validation. 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: Feeder status and permits. Identify its source device or document and the state represented on the drawing.
- Follow the named output: Feeder connection permission. Cross-reference its destination and separate the command from confirmation that the equipment responded.
- A control permissive does not prove field isolation removed correctly.
- Show the prerequisites and confirmation at each control boundary. These original explanatory blocks are not an operating procedure; energization, protection, transformer inrush and motor reacceleration require system-level validation.
Information to show or reference
- Label the source and connection reference for feeder status and permits.
- Identify the destination and defined state of feeder connection permission.
- Record the equipment or control-document revision supporting this functional block.
- Check this application limit in the project design: A control permissive does not prove field isolation removed correctly.
A distinction that matters
A control permissive does not prove field isolation removed correctly. 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.
Avista Shared Energy Economy microgrid protection and control case study
Public technical context for microgrid black-start and restoration controls. Storage, protection, black start, load restoration and coordinated island operation. 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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Microgrid controller
The supervisory controller that dispatches sources, storage and loads and manages islanding and reconnection of a microgrid.
SLD / Schematic
MCRR
Microgrid critical-load restoration request
Requests reconnection of the eligible critical load group at its assigned restoration stage.
Functional block
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