# Microgrid voltage-support reserve indication

Canonical URL: https://eloragrid.ai/symbols/microgrid-voltage-support-reserve-indication
Publisher: Elora Grid
Updated: 2026-11-03
Lookup label: MVRI
Drawing use: Schematic
Reference families: Manufacturer

Representation: Functional block
Installation focus: microgrids
Input: Resource reactive capability and output
Output: Voltage-support headroom

Identifies the declared remaining resource capability for assigned voltage-support action.

## In plain English

### What this block does

Identifies the declared remaining resource capability for assigned voltage-support action.

### A simple example

In an islanded microgrid, the assigned reference source supports bus voltage while other compatible resources share reactive demand according to the selected control method. Grid-connected operation can use a different objective at the PCC. For this reference, the drawing identifies “Resource reactive capability and output” at the input and “Voltage-support headroom” at the output. Headroom is not guaranteed disturbance performance.

### What the drawings help you do

Start at the named input: Resource reactive capability and output. Identify its source device or document and the state represented on the drawing. Follow the named output: Voltage-support headroom. Cross-reference its destination and separate the command from confirmation that the equipment responded.

### Terms

- Input: Resource reactive capability and output
- Output: Voltage-support headroom
- Application reference: An explanation of a named drawing function or circuit relationship; the project documents define the equipment and its connections.

Concept diagram: Resource reactive capability and output → MVRI → Voltage-support headroom
A reading guide. The entry's original illustration and input/output facts describe this application.

- [Microgrid control systems](https://selinc.com/services/microgrids-power-management/microgrid-control-systems/)


## What it represents

Identifies the declared remaining resource capability for assigned voltage-support action. Voltage and reactive-power control coordinate the AC operating condition of the microgrid resources. A voltage target, reactive-power target and power-factor target represent different control objectives and should have explicit ownership.
In an islanded microgrid, the assigned reference source supports bus voltage while other compatible resources share reactive demand according to the selected control method. Grid-connected operation can use a different objective at the PCC. For this reference, the drawing identifies “Resource reactive capability and output” at the input and “Voltage-support headroom” at the output. Headroom is not guaranteed disturbance performance.
Show each measured quantity, target and resource capability limit. Control-loop tuning, equipment capability and parallel operation require a validated design rather than an assumed property of the symbol. 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: Resource reactive capability and output. Identify its source device or document and the state represented on the drawing.
- Follow the named output: Voltage-support headroom. Cross-reference its destination and separate the command from confirmation that the equipment responded.
- Headroom is not guaranteed disturbance performance.
- Show each measured quantity, target and resource capability limit. Control-loop tuning, equipment capability and parallel operation require a validated design rather than an assumed property of the symbol.

## Information to show or reference

- Label the source and connection reference for resource reactive capability and output.
- Identify the destination and defined state of voltage-support headroom.
- Record the equipment or control-document revision supporting this functional block.
- Check this application limit in the project design: Headroom is not guaranteed disturbance performance.

## Important distinction

Headroom is not guaranteed disturbance 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.

## Facts

- Representation: Functional block
- Installation focus: Microgrids
- Input / boundary: Resource reactive capability and output
- Output / connection: Voltage-support headroom
- Lookup label: MVRI is a library lookup label, not a standard device designation.

## Public references

- [Microgrid control systems](https://selinc.com/services/microgrids-power-management/microgrid-control-systems/) — SEL. Public technical context for microgrid voltage and reactive-power controls. Active and reactive power, generation, load control, operating reserves and system supervision. The application text and educational graphic are independently authored; the publisher does not certify this representation.

## Graphic scope

Independent original educational concept illustration by Elora Grid. Not a certified standards graphic or manufacturer footprint. Unitless; not to scale. Original artwork licence: https://creativecommons.org/licenses/by/4.0/. Publisher material is linked only.