Communication Link Supervision for Power Line Channel Asymmetry
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Solution Overview
Problem
Existing methods for detecting channel asymmetry in power transmission systems are not reliable due to the complexity of the transmission line, which includes various sections such as cable and overhead lines, leading to false fault indications and improper breaker operation.
Innovation Solution
A method involving local and remote IEDs that determine and compare phase angles and magnitudes of positive sequence currents in phasor notation to identify channel asymmetry, using matrix calculations and adaptive thresholds to prevent false fault indications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If prior art methods are used to identify channel asymmetry, then the system can detect communication link issues, but the reliability is insufficient due to the complexity of the power transmission line
Solution Approach 1:
The patent segments the complex power transmission line into distinct sections (cable sections and overhead line sections) with different characteristics. By treating each section separately with its own propagation velocity and impedance parameters, the system can accurately model the entire line despite its complexity, enabling reliable channel asymmetry detection.
Solution Approach 2:
The patent changes the approach by using multiple propagation velocity parameters (v1 for cable sections, v2 for overhead line sections) instead of a single velocity parameter. This parameter adaptation allows the system to account for different physical characteristics of various line sections, improving detection reliability while managing complexity through parameterization.
2Loss of information
If the communication link uses wired fiber optic cable network with multiplexers, then data transmission is established, but channel asymmetry occurs causing false fault indications
Solution Approach 1:
The patent implements a feedback mechanism where the system continuously monitors the communication link for asymmetry conditions and uses this information to adjust or block protection operations. By feeding back the asymmetry detection results to the protection logic, the system prevents false fault indications while maintaining accurate data transmission through the fiber optic network.
Solution Approach 2:
The patent introduces an intermediary supervision function that sits between the communication link and the protection operation. This intermediary layer detects channel asymmetry and mediates by blocking or allowing protection operations accordingly, preventing harmful false indications while preserving the underlying data transmission capability.
3Measurement precision
If protection operations are performed based on local and remote measurements, then fault detection capability is improved, but false indications occur due to channel asymmetry
Solution Approach 1:
The patent performs preliminary detection of channel asymmetry before executing protection operations. By checking for asymmetry conditions in advance and blocking operations when asymmetry is detected, the system prevents false fault indications while maintaining the ability to perform accurate protection operations under normal conditions.
Data Source
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AI summary
A method of supervising a communication link (115) of a power transmission system (100) having a power transmission line (101), comprising: - determining, at a local position, measured local current values and measured local voltage values; - receiving, at the local position, via the communication link, data relating to remote phase currents, and determining a measured remote positive sequence current on basis thereof; - estimating a remote positive sequence current on basis of the measured local current values, the measured local voltage values, and properties of the power transmission line and associated devices, which properties comprise series parameters, shunt parameters, and the distance from the local position to the remote position, - comparing a first phase angle and a first magnitude of the estimated remote positive sequence current, with a second phase angle and a second magnitude of the measured remote positive sequence current, and - determining, on basis of the comparison, whether there is a channel asymmetry on the communication link.