HVDC Faulted Conductor Detection Using Current Change Ratios
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In high voltage direct current (HVDC) transmission systems, particularly in VSC-based bipole MT-HVDC systems, there is a challenge in rapidly identifying the faulty conductors and distinguishing between different types of faults, such as pole-to-pole, pole-to-ground, and pole-to-DMR faults, due to electromagnetic coupling and similar electrical characteristics.
Innovation Solution
A method involving monitoring current signals in HVDC transmission systems, filtering these signals, determining the maximum rate of change of current, calculating ratios of these rates of change, and comparing these ratios against discrimination factors to identify faulted conductors and determine fault types.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pole-by-pole fault detection schemes are used based on high frequency current components or voltage derivatives, then fault detection capability is improved, but false operation increases due to electromagnetic coupling between conductors
Solution Approach 1:
The patent introduces an intermediary processing stage that transforms the raw high-frequency current components and voltage derivatives into a new set of variables through mathematical operations. This intermediary transformation allows the system to retain the sensitivity of high-frequency methods while eliminating the false operations caused by electromagnetic coupling, as the transformed variables are designed to be immune to coupling effects.
Solution Approach 2:
The patent changes the parameters being monitored from direct high-frequency current components and voltage derivatives to transformed variables that combine these measurements in specific ways. By changing the parameter representation through mathematical transformation, the system maintains fault detection sensitivity while removing the susceptibility to electromagnetic coupling that causes false operations.
2Reliability
If higher thresholds are used to prevent false operations, then reliability is improved, but sensitivity and selectivity decrease
Solution Approach 1:
The patent uses an intermediary mathematical transformation to create new variables that inherently separate fault signals from coupling interference. This allows the use of optimal threshold values without the compromise normally required, as the transformed variables provide both high sensitivity to actual faults and immunity to false triggering from electromagnetic coupling.
3Reliability
If additional filtering, modal transformation, and supervisory logic are used to improve robustness, then false operation resistance is improved, but device complexity increases
Solution Approach 1:
The patent merges multiple protection functions into a single unified mathematical transformation framework. Instead of separately implementing filtering, modal transformation, and supervisory logic as distinct complex subsystems, the invention combines these functions into one integrated mathematical operation that achieves the same robustness with simpler overall system architecture.
4Productivity
If fault identification speed is increased to clear faults within milliseconds, then productivity is improved, but measurement and detection difficulty increases due to rapidly rising fault currents
Solution Approach 1:
The patent prepares the measurement system in advance by continuously monitoring and preprocessing the high-frequency current components and voltage derivatives even before faults occur. This preliminary action ensures that when a fault happens, the transformed variables are already available and properly conditioned, enabling immediate fault type identification without additional processing delay.
Solution Approach 2:
The patent replaces complex mechanical or electronic filtering and processing mechanisms with mathematical transformations of the measured signals. This substitution allows for extremely fast processing of fault information using digital computation, achieving millisecond-level fault clearance speeds while simplifying the detection system architecture.
Data Source
AI summary
One or more faulted conductors are identified in a power transmission system having at least two power-transmitting conductors and a fault location is determined. The methods for identifying faulted connectors and determining fault location include steps of monitoring current signals which are representative of currents in the conductors at a generally common location within the power transmission system; filtering the current signals; determining a maximum rate of change of each filtered current signal within a predetermined time interval after the fault event has commenced; and calculating a ratio of a pair of the maximum rates of change of the filtered current signals. For fault classification, the ratio is compared against a discrimination factor to identify the one or more faulted conductors. For fault location, the calculated ratio is compared against the calibration data to determine the distance from the connection terminal of the faulted conductor to the fault location.