Fault Current Limiting Circuit for Low-Impedance Power Networks

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Electrical power systems with high energy delivery capacity and low source impedance face damage from extremely sharp fault currents, which existing thermal fuses cannot effectively manage without frequent replacement.

Innovation Solution

An electrical power system incorporating a current limiting diode and a controllable circuit interruption device, which synergistically reduce fault currents to allow for a lower current rating in the circuit interruption device, thereby reducing system mass and enabling effective fault protection without the need for frequent replacements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a controllable circuit interruption device is used to protect against fault current in a high energy delivery capacity system with low source impedance, then fault protection is provided, but the device must be significantly overrated compared to the power source rating due to extremely sharp fault current rises

Engineering Contradiction:

Improvefault protectionVSAvoidcurrent rating of circuit interruption device

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The current limiting diode is placed in series with the power source to proactively limit fault current before it reaches the circuit interruption device. This preliminary current limitation action prevents the extremely sharp current rise that would otherwise require the circuit interruption device to be significantly overrated, allowing it to be properly sized for normal operation plus a reasonable safety margin.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If the current rating of the controllable circuit interruption device is increased to handle extreme fault currents, then fault protection capability is improved, but the mass of the electrical power system increases significantly

Engineering Contradiction:

Improvefault protection capabilityVSAvoidsystem mass

Core Design Contradiction:

ReliabilityVSWeight of moving object

Solution Approach 1:

By implementing current limiting action through the diode before the fault current reaches the circuit interruption device, the system prevents the need for an oversized interruption device. This allows the circuit breaker to be rated appropriately for normal operation with a reasonable safety margin, dramatically reducing its mass while maintaining adequate fault protection capability.

Inventive Principle:

Principle #10Preliminary action

3Object-affected harmful factors

If thermal fuses are used to protect against fault current, then damage from fault current is avoided, but the protective component must be replaced after every fault occurrence

Engineering Contradiction:

Improvefault current damageVSAvoidreplacement frequency

Core Design Contradiction:

Object-affected harmful factorsVSEase of repair

Solution Approach 1:

The patent replaces the purely thermal, non-resettable fuse mechanism with an electronic current limiting diode combined with a controllable circuit interruption device. This electronic substitution allows for rapid electronic detection and controlled interruption of fault currents, providing protection that is both effective and resettable, eliminating the need for component replacement after each fault.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The combination of a current limiting diode and a controllable circuit interruption device reduces fault current levels, allowing for a lower current rating in the circuit interruption device, enhancing system safety and reducing mass, particularly beneficial in aircraft systems, while providing a resettable protection against fault currents.

Implementation Method 1

a current limiting diode which is configured to limit a fault current passing between the electrical power source and the electrical network in a fault condition

Methodology Applied

Scientific EffectDiode current limiting: Diode

Implementation Method 2

a controllable circuit interruption device which is configured to interrupt the fault current in response to a determination that the electrical power system is in the fault condition

Methodology Applied

Scientific EffectCircuit interruption: Electric Arc

Implementation Method 3

The heat sink provided to the current limiting diode may comprise a phase-change material configured to absorb heat from the current limiting diode in the fault condition

Methodology Applied

Scientific EffectPhase change heat absorption: Phase Change

Data Source

PatentUS11837894B2Electrical power system

Publication Date: 2023.12.05 ROLLS ROYCE PLC

AI summary

An electrical power system including: an electrical power source, a power electronics converter, an electrical network, a current limiting diode and a controllable circuit interruption device, wherein: the current limiting diode is configured to limit a fault current passing between the electrical power source and the electrical network in a fault condition; and the controllable circuit interruption device is configured to interrupt the fault current in response to a determination that the electrical power system is in the fault condition.