Adaptive Differential Protection for Multi-Terminal T-Connected Lines
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Solution Overview
Problem
Current differential protection methods for multi-terminal T-connected electricity transmission lines face challenges in sensitivity and reliability due to fixed resistive coefficients, which are not adaptable to fault conditions, affecting the speed and selectivity of fault detection.
Innovation Solution
A method that automatically selects a resistive coefficient K based on fault conditions by sampling phase currents, calculating fault component currents, and determining a suitable coefficient value for differential protection, improving sensitivity within the fault area and reliability outside the area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed resistive coefficient is used in differential protection calculation, then the protection method is simple and easy to implement, but the sensitivity within the fault area and reliability outside the fault area cannot be improved simultaneously
Solution Approach 1:
The patent transforms the fixed resistive coefficient into a dynamic, adaptive coefficient that changes based on fault conditions. The resistive coefficient is no longer a static value but is automatically adjusted according to the measured current characteristics and fault location, thereby improving both sensitivity and reliability without requiring complex manual configuration.
Solution Approach 2:
The protection system performs self-determination of the resistive coefficient by automatically analyzing the current phasor characteristics and fault conditions. The system independently calculates and adjusts the coefficient based on the measured electrical parameters, eliminating the need for external manual intervention or complex preset configurations while enhancing protection performance.
2Measurement precision
If the resistive coefficient is fixed, then the calculation method is simple, but the sensitivity for detecting faults in multi-terminal T-connected lines is insufficient
Solution Approach 1:
The patent changes the resistive coefficient parameter dynamically based on fault conditions rather than using a fixed value. By adjusting this critical parameter according to the specific fault scenario, the system achieves higher measurement precision and sensitivity for detecting faults in multi-terminal T-connected lines while maintaining adaptability to various fault types and locations.
Solution Approach 2:
The patent applies different resistive coefficient values tailored to specific fault locations and conditions. Instead of using a uniform coefficient throughout the system, the method determines locally optimized coefficients based on the particular fault scenario, thereby enhancing detection sensitivity for each specific case while maintaining overall system versatility.
Data Source
AI summary
Provided is a determination method of differential protection suitable for an electricity transmission line with multi-terminal T-connection. The determination method includes: sampling and calculating all phase currents, and calculating a maximum fault component current Δİmax in phase current amplitudes of each phase current, a differential current Icd in the each phase current, a resistive current Ires in the each phase current and a vector sum ΔİΣ of fault component currents except Δİmax in the phase current amplitudes of the each phase current; and comparing the maximum fault component current Δİmax in phase current amplitudes of each phase current and a threshold setting value Imax0, determining a value of a resistive coefficient K corresponding to the phase current amplitudes of the each phase current according to a comparison result, and performing differential determination on the differential current Icd and the resistive current Ires in phase current amplitudes of the each phase current according to a differential determination formula: if the differential current Icd of the target phase satisfies the above differential determination formula, it is determined that a fault occurs in an area of the target phase.