HVDC Fault Detection via AC Quantity Analysis
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Solution Overview
Problem
High-voltage direct current (HVDC) transmission systems face challenges in detecting and isolating faults, particularly distinguishing between internal and external faults, leading to unnecessary system shutdowns and inability to continue power transmission during faults.
Innovation Solution
A method and device for detecting faults in a DC power transmission system by analyzing AC electrical quantities across conductors, using Clarke transformations and pulse width modulation to differentiate between internal and external faults, allowing selective activation of protective functions and continued power transmission from unaffected components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the entire HVDC transmission system is shut down in the event of an intersystem fault, then system safety is ensured, but power transmission capability is lost
Solution Approach 1:
The HVDC transmission system is divided into independent poles (first pole and second pole), allowing selective shutdown of only the affected pole during an intersystem fault while the other pole continues to transmit power, thus maintaining partial productivity while ensuring safety
Solution Approach 2:
The fault detection and protective function activation is localized to specific conductors and poles based on precise fault identification, allowing unaffected parts of the system to continue operating normally while only the affected components are isolated
2Speed
If fault detection methods are simplified, then response speed is improved, but fault location precision deteriorates
Solution Approach 1:
The patent replaces complex mechanical analysis methods with electrical signal analysis by evaluating AC electrical quantities and their relationships during fault conditions, enabling rapid and precise fault detection through electrical measurements rather than mechanical inspection
Solution Approach 2:
The patent changes the evaluation parameters from simple presence/absence detection to quantitative analysis of AC electrical quantity relationships (comparing measured values against expected relationships), enabling both rapid detection and precise fault location identification through parameter comparison
3Reliability
If protective functions are activated for all conductors during a fault, then system protection is ensured, but unnecessary shutdowns occur
Solution Approach 1:
The protective function activation is made local and selective, applying protection only to the specific conductor or pole where the intersystem fault is detected, while leaving other conductors and poles operational to maintain power transmission continuity
Solution Approach 2:
The system is segmented into independent protective zones for each pole and conductor, allowing the protective function to be activated only in the affected zone while other zones continue to operate normally, thus ensuring protection where needed without causing unnecessary shutdowns
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
Enables precise fault detection and isolation, preventing unnecessary system shutdowns and allowing continued energy transfer by distinguishing between internal and external faults, thereby maintaining power transmission through unaffected parts of the system.
Implementation Method 1
determining respective values of an AC electrical quantity associated with the first conductor, the neutral conductor and the associated with the second conductor
Data Source
Figure 1
Figure 2
AI summary
Described is a method for detecting a fault (63, 65) in a direct current transmission system (1) with a first conductor (3), a neutral conductor (5) and a second conductor (7), comprising: determining respective values (67, 69, 71, 45, 47, 49) of an alternating current quantity (I, V) that are assigned to the first conductor (3), the neutral conductor (5) and the second conductor (7), respectively; analyzing the values (67, 69, 71, 45, 47, 49); and determining whether and, if so, which conductor of the first, second and neutral conductors is affected by the fault from a result (83) of the analysis.