Sense-Wire Cable Protection for Inrush and Fault Differentiation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current fault protection systems in high power systems face challenges due to inrush current fluctuations resembling fault events, making it difficult to differentiate between inrush and actual faults, particularly in power transmission lines, and there is a need for improved fault detection and protection, especially against human touch contact.
Innovation Solution
A protection system for power transmission cables that includes a sense wire wrapped around a main conductor wire with a sense resistor, a leakage current sensor circuit, and a controller to manage fault protection by monitoring current imbalances and using switching devices to isolate faults, with inrush limiters and zero-crossing detectors for AC and DC operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If inrush limiters are used to limit inrush current, then inrush current is reduced, but fault detection precision deteriorates because inrush current fluctuations resemble fault current fluctuations
Solution Approach 1:
A sense wire wrapped around the main conductor wire acts as an intermediary sensing element. The sense wire detects current through electromagnetic induction without carrying the full load current, allowing accurate fault detection while the inrush limiter controls inrush current. The sense wire functions as a mediator between the power transmission line and the detection circuitry.
Solution Approach 2:
The patent replaces direct electrical connection-based current sensing with electromagnetic induction-based sensing. Instead of using a shunt resistor or direct contact method that would be affected by inrush current limitations, the sense wire uses electromagnetic field coupling to detect current, substituting a mechanical/electrical sensing approach with an electromagnetic field-based approach.
2Reliability
If fault protection systems monitor current continuously, then fault detection reliability is improved, but device complexity increases due to additional sensing components and control circuits
Solution Approach 1:
The sense wire serves multiple functions: it acts as both the sensing element for current detection and provides shielding for the main conductor. The controller integrates multiple detection functions (inrush detection, fault detection, human touch detection) into a single control unit that manages breaker devices and switching devices, reducing overall system complexity through functional integration.
Solution Approach 2:
The sense wire generates its own sensing signal through electromagnetic induction from the main conductor current, requiring no external power connection or additional sensing components. The system uses the existing electromagnetic field around the conductor to provide sensing, making the sensing mechanism self-powered and eliminating the need for separate excitation circuits.
3Reliability
If breaker devices are used for fault protection, then protection reliability is improved, but response speed deteriorates due to mechanical operation time
Solution Approach 1:
The system performs preliminary detection and classification of current conditions (inrush vs. fault) before activating the breaker devices. The controller continuously monitors the sense wire output and prepares the breaker devices for rapid operation by pre-charging capacitors and positioning switching devices, enabling faster response when a fault is actually detected.
Solution Approach 2:
The sense wire acts as an intermediary that provides early warning of fault conditions before they develop into dangerous levels. By detecting changes in the electromagnetic field around the conductor, the system can trigger protective actions before the fault current reaches peak levels, effectively speeding up the protection response.
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
Effectively distinguishes between inrush and fault currents, providing reliable protection against human contact and other faults by isolating the system and initiating controlled restarts, ensuring safe operation of power transmission systems.
Implementation Method 1
A sense wire is wrapped around the first wire insulator with a sense resistor in series electrically with the sense wire
Data Source
AI summary
A system includes a transmission cable with a first main conductor wire. A sense wire is wrapped around the first main conductor wire with a sense resistor in series electrically with the sense wire. The transmission cable includes one or more additional main conductor wires each including a respective conductor. A protection system is operatively connected to the transmission cable, including a leakage current sensor circuit (LCSC) operatively connected to the sense wire to provide feedback indicative of current in the sense wire. A controller is operatively connected to provide feedback based control to a plurality of switching devices for fault protection. The controller is operatively connected to receive the feedback indicative of current in the sense wire from the LCSC for feedback based control of the plurality of switching devices.