# Phase-discontinuity protection

Canonical URL: https://eloragrid.ai/protection-functions/46pd-phase-discontinuity-protection
Publisher: Elora Grid
Updated: 2026-10-13
Lookup label: 46PD
Drawing use: SLD, Schematic
Reference families: IEEE / ANSI, Manufacturer

Uses current-sequence relationships to detect a phase-discontinuity condition.

## What it represents

Uses current-sequence relationships to detect a phase-discontinuity condition.
The drafting record should connect this function to the three phase CT circuits and current-unbalance ratio reference, then trace the open-phase alarm or trip logic. Keep the complete designation and equipment tag together so that the SLD, relay logic and terminal schedule describe the same implementation.
The cited mapping is a public manufacturer example (ABB Relion 620 function mapping). Suffixes are not universal equivalences across products, and this reference supplies neither a protection setting nor certification of the selected scheme.

## How to read it

- Identify the three phase CT circuits and current-unbalance ratio reference.
- Trace the open-phase alarm or trip logic.

## Information to show or reference

- Label the three phase CT circuits and current-unbalance ratio reference.
- Cross-reference the open-phase alarm or trip logic.
- Retain the complete suffix, selected device tag and manufacturer manual revision.

## Important distinction

ABB's 46PD application is phase discontinuity; a phase-order relay and an ordinary overcurrent element address different conditions.

## Facts

- Function designation: 46PD
- Base function: 46 — Current unbalance / negative sequence
- Published mapping: ABB Relion 620 function mapping
- Suffix scope: Application or manufacturer specific; check the complete drawing legend and selected device manual.

## Public references

- [Relion 620 series: published protection function and designation mappings](https://techdoc.relays.protection-control.abb/r/620-series-IEC-60870-5-103-Point-List-Manual/2.0-FP1-IEC/en-US/Functions-codes-and-symbols) — ABB. Public primary-source function or application mapping used to identify this designation; wording and drafting notes are original.
- [IEEE C37.2-2022: power-system device function numbers](https://ieeexplore.ieee.org/document/9984140) — IEEE. Device-number and suffix convention. This page is not a reproduction of the full licensed standard.

## 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.