Generator Disconnection Timing Control for Out-of-Step Protection

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Current methods for disconnecting a generator from a power system during an out-of-step condition expose both the generator and circuit breakers to high electrical and mechanical stress due to delayed disconnection.

Innovation Solution

A method and system that predict and disconnect the generator when the minimum amplitude of an electrical parameter associated with the generator is reached, reducing stress by using a measuring unit and processing unit to determine synchronization loss and generate a command signal for disconnection at the parameter's minimum amplitude.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If the generator is disconnected after a predetermined number of torque pulses, then the disconnection decision is simple to implement, but the generator and circuit breakers are exposed to high electrical and mechanical stress

Engineering Contradiction:

Improvedisconnection control complexityVSAvoidelectrical and mechanical stress on generator and circuit breakers

Core Design Contradiction:

Device complexityVSObject-affected harmful factors

Solution Approach 1:

The system performs preliminary action by predicting the future minimum amplitude of the electrical parameter before it occurs. The processing unit calculates when the minimum will happen and sends a command signal in advance to the circuit breakers, allowing them to prepare for disconnection at the optimal moment rather than using a simple predetermined pulse count.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system uses feedback by continuously monitoring the electrical parameter (current or voltage) and using this information to determine when the minimum amplitude will occur. The processing unit analyzes the parameter's behavior and adjusts the disconnection timing based on real-time measurements, creating a closed-loop control system that optimizes the disconnection moment.

Inventive Principle:

Principle #23Feedback

2Object-affected harmful factors

If the generator is disconnected at the minimum amplitude of the electrical parameter, then the stress on generator and circuit breakers is minimized, but the disconnection timing requires complex prediction and measurement

Engineering Contradiction:

Improveelectrical and mechanical stress on generator and circuit breakersVSAvoiddisconnection control complexity

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The processing unit performs preliminary calculation to predict when the minimum amplitude will occur before it actually happens. By computing the future minimum point based on current parameter trends and sending a command signal in advance, the system prepares for optimal disconnection timing without waiting for the minimum to naturally occur first.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system replaces simple mechanical timing (predetermined pulse counting) with an intelligent control system that uses electrical measurements and processing. The processing unit substitutes basic mechanical countdown logic with electrical parameter monitoring, mathematical prediction, and automated command generation, achieving superior results through electrical intelligence rather than mechanical simplicity.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Speed

If circuit breakers disconnect the generator during high current conditions, then the disconnection response is immediate, but the circuit breakers and generator suffer severe electrical and mechanical stress

Engineering Contradiction:

Improvedisconnection response speedVSAvoidelectrical and mechanical stress on circuit breakers and generator

Core Design Contradiction:

SpeedVSObject-affected harmful factors

Solution Approach 1:

The system takes preliminary action by predicting the upcoming minimum amplitude and sending the disconnection command before the minimum occurs. This allows the circuit breakers to begin their operation in advance, timing their actual disconnection to coincide with the minimum current moment rather than responding reactively to high current conditions.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system skips through the high-stress period by strategically timing the disconnection to occur at the minimum amplitude point. Rather than attempting to interrupt during the peak current (which would cause severe stress), the system allows the current to naturally pass through its cycle and executes disconnection at the safest moment, effectively skipping over the harmful high-stress phase.

Inventive Principle:

Principle #21Skipping (Rushing through)

Data Source

PatentUS8970071B2Method and system for disconnecting a generator from a power system

Publication Date: 2015.03.03 HITACHI ENERGY LTD

AI summary

A method for disconnecting a generator from a power system when the generator and the thereto connected power system are non-synchronized. The method includes the steps of: determining that there is a loss of synchronization between the generator and the power system, which loss of synchronization provides an amplitude variation of an electrical parameter associated with the generator. The method further includes determining when a minimum amplitude of the electrical parameter will occur, wherein when the occurrence of the minimum amplitude has been predicted, providing a command signal for disconnecting the generator from the power system, wherein the command signal is provided prior to the minimum amplitude of the electrical parameter is attained, and disconnecting the generator from the power system approximately when the determined minimum amplitude of the electrical parameter occurs. It is also presented a protection system for a generator in a power system.