# Optical current measurement processing interface Canonical URL: https://eloragrid.ai/symbols/optical-current-measurement-processing-interface Publisher: Elora Grid Updated: 2026-11-03 Lookup label: OCMPI Drawing use: Schematic Reference families: Manufacturer Representation: Functional block Installation focus: substations Input: Optical sensing information Output: Processed current measurement Shows the processing boundary between an optical current sensor and its downstream measurement output. ## In plain English ### What this block does Shows the processing boundary between an optical current sensor and its downstream measurement output. ### A simple example In a substation protection panel, separate CT cores can supply metering and protection circuits with different duties. A test boundary must preserve the secondary arrangement required by the selected CT and test device. For this reference, the drawing identifies “Optical sensing information” at the input and “Processed current measurement” at the output. Output format depends on the selected sensing system. ### What the drawings help you do Start at the named input: Optical sensing information. Identify its source device or document and the state represented on the drawing. Follow the named output: Processed current measurement. Cross-reference its destination and separate the command from confirmation that the equipment responded. ### Terms - Input: Optical sensing information - Output: Processed current measurement - Application reference: An explanation of a named drawing function or circuit relationship; the project documents define the equipment and its connections. Concept diagram: Optical sensing information → OCMPI → Processed current measurement A reading guide. The entry's original illustration and input/output facts describe this application. - [Indoor current and voltage transformers](https://www.abb.com/gb/en/areas/electrification/medium-voltage/grid-components/core-components/indoor-instrument-transformers) ## What it represents Shows the processing boundary between an optical current sensor and its downstream measurement output. A current-transformer secondary arrangement carries a measuring current from a defined primary location to metering or protection inputs. Core identity, polarity and the connected circuit determine the measurement's meaning. In a substation protection panel, separate CT cores can supply metering and protection circuits with different duties. A test boundary must preserve the secondary arrangement required by the selected CT and test device. For this reference, the drawing identifies “Optical sensing information” at the input and “Processed current measurement” at the output. Output format depends on the selected sensing system. Trace every secondary connection and the assigned earthing point against the actual connection diagram. These illustrations explain circuit roles and never prescribe a live CT switching or disconnection procedure. 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: Optical sensing information. Identify its source device or document and the state represented on the drawing. - Follow the named output: Processed current measurement. Cross-reference its destination and separate the command from confirmation that the equipment responded. - Output format depends on the selected sensing system. - Trace every secondary connection and the assigned earthing point against the actual connection diagram. These illustrations explain circuit roles and never prescribe a live CT switching or disconnection procedure. ## Information to show or reference - Label the source and connection reference for optical sensing information. - Identify the destination and defined state of processed current measurement. - Record the equipment or control-document revision supporting this functional block. - Check this application limit in the project design: Output format depends on the selected sensing system. ## Important distinction Output format depends on the selected sensing system. 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: Optical sensing information - Output / connection: Processed current measurement - Lookup label: OCMPI is a library lookup label, not a standard device designation. ## Public references - [Indoor current and voltage transformers](https://www.abb.com/gb/en/areas/electrification/medium-voltage/grid-components/core-components/indoor-instrument-transformers) — ABB. Public technical context for current-transformer secondary arrangements. Current and voltage measurement transformers and their secondary interfaces. 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.