In-phase Motor Bus Transfer via Intelligent Electronic Device

Solution Overview

Problem

Existing electric power distribution systems face challenges in determining the optimal time to transfer power from one feeder to another without causing mechanical stress to equipment like motors, due to phase and frequency differences, and also account for the uncertainty in breaker close times.

Innovation Solution

The implementation of an intelligent electronic device (IED) that monitors voltage and frequency differences between feeders and the load bus, calculates the appropriate close time for the breaker, and considers the breaker close time delay and uncertainty to ensure in-phase transfer, thereby reducing equipment stress.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If breaker close time is not accounted for in transfer timing, then transfer operation is simpler, but phase difference between feeders causes mechanical stress on equipment

Engineering Contradiction:

Improvetransfer operation simplicityVSAvoidmechanical stress on equipment

Core Design Contradiction:

Ease of operationVSObject-affected harmful factors

Solution Approach 1:

The system performs preliminary calculation of the optimal close time by considering the breaker's close time characteristic before issuing the close command. This ensures that when the breaker actually closes, the phase difference between feeders is minimized, preventing mechanical stress on equipment while maintaining operational simplicity.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system incorporates feedback by using the breaker's actual close time characteristic (measured or specified) to adjust the timing of the close command. This closed-loop approach ensures accurate synchronization despite variations in breaker operation, eliminating mechanical stress without complicating the transfer operation.

Inventive Principle:

Principle #23Feedback

2Device complexity

If breaker close time uncertainty is not considered, then transfer timing is more straightforward, but phase synchronization accuracy deteriorates

Engineering Contradiction:

Improvetransfer timing complexityVSAvoidphase synchronization accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The system performs preliminary calculation of the optimal close time by considering the breaker's close time characteristic before issuing the close command. This ensures that when the breaker actually closes, the phase difference between feeders is minimized, preventing mechanical stress on equipment while maintaining operational simplicity.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system incorporates feedback by using the breaker's actual close time characteristic (measured or specified) to adjust the timing of the close command. This closed-loop approach ensures accurate synchronization despite variations in breaker operation, eliminating mechanical stress without complicating the transfer operation.

Inventive Principle:

Principle #23Feedback

3Speed

If transfer is performed without accounting for breaker close time delay, then operational response is faster, but phase difference exceeds acceptable margins at connection

Engineering Contradiction:

Improveoperational response speedVSAvoidphase alignment precision

Core Design Contradiction:

SpeedVSManufacturing precision

Solution Approach 1:

The system performs preliminary calculation of the optimal close time by considering the breaker's close time characteristic before issuing the close command. This ensures that when the breaker actually closes, the phase difference between feeders is minimized, preventing mechanical stress on equipment while maintaining operational simplicity.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS11018497B2In-phase motor bus transfer

Publication Date: 2021.05.25 SCHWEITZER ENGINEERING LABORATORIES INC

AI summary

In-phase transfer of an electric power source to a load bus from a first feeder to a second feeder is disclosed herein. Voltage phase difference, voltage frequency difference, and voltage rate-of-change of frequency difference, between the second feeder and the load bus are used along with a breaker delay time to determine whether the breaker will close while the phase of the second feeder and the load bus are within an acceptable range. One or more breaker close time checks may be performed, including a breaker close time consistency check and a breaker close time uncertainty check.