Circuit Breaker Failure Relay Dynamic Threshold Adjustment

Solution Overview

Problem

Circuit breaker failure protection relays often malfunction due to erroneous detection of trip signals, leading to increased power failure areas and prolonged outages, as they struggle to distinguish between fault currents and load currents, especially during ground faults with high resistance.

Innovation Solution

A circuit breaker failure protection relay with a circuit breaker failure detection element that adjusts its setting value based on a switching signal, allowing for reliable detection of fault currents without misidentifying load currents, thereby preventing malfunctions during inspections and normal operations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the setting value of the overcurrent relay element is set low to detect fault currents smaller than load current, then the detection sensitivity is improved, but the relay malfunctions by erroneously detecting load current as fault current

Engineering Contradiction:

Improvedetection sensitivityVSAvoidrelay operation reliability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent applies dynamics by making the setting value of the overcurrent relay element changeable rather than fixed. The setting value is dynamically adjusted based on the operational state of the relay: a first setting value is used during inspection/maintenance modes when trip signals may be erroneously generated, and a second setting value is used during normal operation. This dynamic adjustment allows the relay to maintain high detection sensitivity during normal operation while preventing malfunctions during inspection modes.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent applies parameter changes by modifying the setting value parameter of the overcurrent relay element according to different operational conditions. The control unit changes the setting value between a first value (higher threshold) and a second value (lower threshold) based on whether the relay is in inspection mode or normal operation mode. This parameter change enables the relay to adapt its detection characteristics to different operational contexts, resolving the contradiction between sensitivity and reliability.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If the setting value of the overcurrent relay element is set high to prevent detection of load current, then the relay reliability is improved, but the detection capability for fault currents smaller than load current is lost

Engineering Contradiction:

Improverelay operation reliabilityVSAvoiddetection sensitivity

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The patent applies dynamics by making the setting value of the overcurrent relay element changeable rather than fixed. The setting value is dynamically adjusted based on the operational state of the relay: a first setting value is used during inspection/maintenance modes when trip signals may be erroneously generated, and a second setting value is used during normal operation. This dynamic adjustment allows the relay to maintain high detection sensitivity during normal operation while preventing malfunctions during inspection modes.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent applies parameter changes by modifying the setting value parameter of the overcurrent relay element according to different operational conditions. The control unit changes the setting value between a first value (higher threshold) and a second value (lower threshold) based on whether the relay is in inspection mode or normal operation mode. This parameter change enables the relay to adapt its detection characteristics to different operational contexts, resolving the contradiction between sensitivity and reliability.

Inventive Principle:

Principle #35Parameter changes

3Productivity

If the CBF relay outputs trip signal upon erroneous detection, then the fault removal function is activated, but the power failure area expands and outage duration increases

Engineering Contradiction:

Improvefault removal efficiencyVSAvoidpower failure impact

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent applies preliminary anti-action by implementing a verification mechanism before the CBF relay outputs a trip signal. When the overcurrent relay element detects an overcurrent condition, the control unit does not immediately output a trip signal. Instead, it first verifies whether a trip signal from the main protection relay device has been received. Only when both conditions are met does the CBF relay output the trip signal. This preliminary verification prevents erroneous trip signals from expanding power failure areas while maintaining the ability to quickly respond to genuine circuit breaker failures.

Inventive Principle:

Principle #9Preliminary anti-action

Data Source

PatentUS11050237B2Circuit breaker failure protection relay and protection relay system

Publication Date: 2021.06.29 MITSUBISHI ELECTRIC CORP

AI summary

A circuit breaker failure protection relay includes an input circuit to which an opening command from a first circuit breaker is input, and a circuit breaker failure detection element configured to compare a magnitude of a current detection signal in a power system with a setting value to make a determination about an overcurrent. The circuit breaker failure detection element is capable of changing the setting value to a first value and a second value that is larger than the first value according to a switching signal. The circuit breaker failure protection relay is configured to, when the opening command is input and when the circuit breaker failure detection element determines that an overcurrent occurs, output an opening command for the second circuit breaker in a neighborhood of the first circuit breaker.