# Station DC insulation-monitor interface

Canonical URL: https://eloragrid.ai/symbols/station-dc-insulation-monitor-interface
Publisher: Elora Grid
Updated: 2026-11-03
Lookup label: SDII
Drawing use: Schematic
Reference families: Manufacturer

Representation: Functional block
Installation focus: substations
Input: DC insulation measurement
Output: Insulation-condition alarm

Connects the selected insulation-monitoring device to the station DC system and alarm paths.

## In plain English

### What this block does

Connects the selected insulation-monitoring device to the station DC system and alarm paths.

### A simple example

In a substation control building, the battery can support breaker trip circuits while the charger AC supply is unavailable. Supervision must identify whether the charger, battery or a downstream feeder is affected. For this reference, the drawing identifies “DC insulation measurement” at the input and “Insulation-condition alarm” at the output. The monitored system and method must be identified.

### What the drawings help you do

Start at the named input: DC insulation measurement. Identify its source device or document and the state represented on the drawing. Follow the named output: Insulation-condition alarm. Cross-reference its destination and separate the command from confirmation that the equipment responded.

### Terms

- Input: DC insulation measurement
- Output: Insulation-condition alarm
- Application reference: An explanation of a named drawing function or circuit relationship; the project documents define the equipment and its connections.

Concept diagram: DC insulation measurement → SDII → Insulation-condition alarm
A reading guide. The entry's original illustration and input/output facts describe this application.

- [MicroGenius S2/S4 battery charger technical manual](https://www.sens-usa.com/hubfs/Controlled%20Files/Manuals/101330_MGS_User_Manual.pdf)


## What it represents

Connects the selected insulation-monitoring device to the station DC system and alarm paths. A station battery system supplies protection, control and other assigned DC loads through a documented charger and distribution arrangement. Charger output, battery contribution and load distribution are related but separately monitored paths.
In a substation control building, the battery can support breaker trip circuits while the charger AC supply is unavailable. Supervision must identify whether the charger, battery or a downstream feeder is affected. For this reference, the drawing identifies “DC insulation measurement” at the input and “Insulation-condition alarm” at the output. The monitored system and method must be identified.
Identify every source, protective device, isolation boundary and return. Battery capacity, DC fault duty, charging settings and ventilation require the selected battery-system design; illustrative circuits do not establish autonomy. 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: DC insulation measurement. Identify its source device or document and the state represented on the drawing.
- Follow the named output: Insulation-condition alarm. Cross-reference its destination and separate the command from confirmation that the equipment responded.
- The monitored system and method must be identified.
- Identify every source, protective device, isolation boundary and return. Battery capacity, DC fault duty, charging settings and ventilation require the selected battery-system design; illustrative circuits do not establish autonomy.

## Information to show or reference

- Label the source and connection reference for dc insulation measurement.
- Identify the destination and defined state of insulation-condition alarm.
- Record the equipment or control-document revision supporting this functional block.
- Check this application limit in the project design: The monitored system and method must be identified.

## Important distinction

The monitored system and method must be identified. 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: Substations
- Input / boundary: DC insulation measurement
- Output / connection: Insulation-condition alarm
- Lookup label: SDII is a library lookup label, not a standard device designation.

## Public references

- [MicroGenius S2/S4 battery charger technical manual](https://www.sens-usa.com/hubfs/Controlled%20Files/Manuals/101330_MGS_User_Manual.pdf) — SENS. Public technical context for station battery and charger distribution. Battery charging modes, DC distribution interfaces and charger alarms. 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.