# Diesel generator set

Canonical URL: https://eloragrid.ai/symbols/diesel-generator-set
Publisher: Elora Grid
Updated: 2026-10-28
Lookup label: DG
Drawing use: SLD
Reference families: IEC, IEEE / ANSI, Manufacturer

A compression-ignition engine coupled to an alternator, shown as a source on microgrid and standby power single-line diagrams.

## In plain English

### What does Diesel generator set mean?

A diesel generator set combines a diesel engine, an alternator, a controller and usually a generator breaker into one package. On a microgrid single-line diagram it is the dispatchable source that sets voltage and frequency when the utility is absent, or that supports the battery during long periods of low renewable output.

### A simple example

It is commonly drawn as a generator circle with an engine box or the letters DG or D beside the mechanical coupling, followed by the generator breaker and its protection relay. Ratings are often written as prime, continuous or standby, because the same set can carry different loads under each duty definition.

### What the drawings help you do

The symbol does not tell you minimum loading limits, fuel autonomy or the governor and regulator settings needed to share load with other sources. Light loading of diesel engines causes wet stacking, so microgrid controls often maintain a minimum genset load that the diagram does not show.

### This particular reference

A compression-ignition engine coupled to an alternator, shown as a source on microgrid and standby power single-line diagrams. A diesel set uses compression ignition and liquid fuel; a gas engine set uses spark ignition and gaseous fuel with different load-acceptance behaviour.

### Terms

- 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.

Concept diagram: Identify the device and form → Read the connections and state → Check the equipment reference
A guide to reading this reference. The original symbol illustration and its drawing notes appear below; these boxes are not a wiring diagram.

- [T-030 liquid-cooled generator set application manual](https://www.cummins.com/sites/default/files/2024-08/t030-Liquid-cooled-gen-set-application-manual.pdf)
- [Generator switchgear and paralleling controls](https://www.cummins.com/en-na/generators/products/switchgear)


## What it represents

A diesel generator set combines a diesel engine, an alternator, a controller and usually a generator breaker into one package. On a microgrid single-line diagram it is the dispatchable source that sets voltage and frequency when the utility is absent, or that supports the battery during long periods of low renewable output.
It is commonly drawn as a generator circle with an engine box or the letters DG or D beside the mechanical coupling, followed by the generator breaker and its protection relay. Ratings are often written as prime, continuous or standby, because the same set can carry different loads under each duty definition.
The symbol does not tell you minimum loading limits, fuel autonomy or the governor and regulator settings needed to share load with other sources. Light loading of diesel engines causes wet stacking, so microgrid controls often maintain a minimum genset load that the diagram does not show.

## How to read it

- Check whether the rating shown is standby, prime or continuous.
- Follow the controller connections to see whether the set can parallel with other sources.

## Information to show or reference

- State kVA, kW, power factor and duty rating.
- Show generator breaker and neutral earthing.
- Reference controller and fuel system drawings.

## Important distinction

A diesel set uses compression ignition and liquid fuel; a gas engine set uses spark ignition and gaseous fuel with different load-acceptance behaviour.

## Facts

- Prime mover: Diesel reciprocating engine
- Typical role: Standby or grid-forming backup source
- Duty ratings: Standby, prime, continuous
- Preview: Independent educational illustration; not a manufacturer outline

## Public references

- [T-030 liquid-cooled generator set application manual](https://www.cummins.com/sites/default/files/2024-08/t030-Liquid-cooled-gen-set-application-manual.pdf) — Cummins. Public generator-set application manual for ratings and installation context.
- [Generator switchgear and paralleling controls](https://www.cummins.com/en-na/generators/products/switchgear) — Cummins. Public generator switchgear and paralleling control context.

## 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.