# Time-distribution redundant-path interface

Canonical URL: https://eloragrid.ai/symbols/time-distribution-redundant-path-interface
Publisher: Elora Grid
Updated: 2026-11-03
Lookup label: TRI
Drawing use: Schematic
Reference families: Manufacturer

Representation: Functional block
Installation focus: substations
Input: Alternative timing paths
Output: Available client time reference

Identifies the independently documented timing paths serving the selected client equipment.

## In plain English

### What this block does

Identifies the independently documented timing paths serving the selected client equipment.

### A simple example

In a substation, a station clock can provide precision timing to process equipment and another timing interface to event recorders. The alarm system should distinguish loss of a distribution path from loss of the external time source. For this reference, the drawing identifies “Alternative timing paths” at the input and “Available client time reference” at the output. Shared clock dependencies must remain visible.

### What the drawings help you do

Start at the named input: Alternative timing paths. Identify its source device or document and the state represented on the drawing. Follow the named output: Available client time reference. Cross-reference its destination and separate the command from confirmation that the equipment responded.

### Terms

- Input: Alternative timing paths
- Output: Available client time reference
- Application reference: An explanation of a named drawing function or circuit relationship; the project documents define the equipment and its connections.

Concept diagram: Alternative timing paths → TRI → Available client time reference
A reading guide. The entry's original illustration and input/output facts describe this application.

- [SEL-2488 satellite-synchronised network clock](https://selinc.com/products/2488/)


## What it represents

Identifies the independently documented timing paths serving the selected client equipment. A station time system provides a shared time reference for protection records, measurements and automation. Different devices can use different timing protocols, so the time source, distribution path and quality information must remain identifiable.
In a substation, a station clock can provide precision timing to process equipment and another timing interface to event recorders. The alarm system should distinguish loss of a distribution path from loss of the external time source. For this reference, the drawing identifies “Alternative timing paths” at the input and “Available client time reference” at the output. Shared clock dependencies must remain visible.
Show the source and client of each time connection. Required accuracy, holdover, protocol profile and loss-of-time behavior follow the selected application; a common timestamp format does not guarantee synchronized events. 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: Alternative timing paths. Identify its source device or document and the state represented on the drawing.
- Follow the named output: Available client time reference. Cross-reference its destination and separate the command from confirmation that the equipment responded.
- Shared clock dependencies must remain visible.
- Show the source and client of each time connection. Required accuracy, holdover, protocol profile and loss-of-time behavior follow the selected application; a common timestamp format does not guarantee synchronized events.

## Information to show or reference

- Label the source and connection reference for alternative timing paths.
- Identify the destination and defined state of available client time reference.
- Record the equipment or control-document revision supporting this functional block.
- Check this application limit in the project design: Shared clock dependencies must remain visible.

## Important distinction

Shared clock dependencies must remain visible. 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: Alternative timing paths
- Output / connection: Available client time reference
- Lookup label: TRI is a library lookup label, not a standard device designation.

## Public references

- [SEL-2488 satellite-synchronised network clock](https://selinc.com/products/2488/) — SEL. Public technical context for substation timing and event interfaces. PTP, NTP, IRIG-B, pulse distribution, reference failover and timing quality. 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.