Distance Protection Using Zero-Sequence Impedance for Asynchronous Generators
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Solution Overview
Problem
Existing distance protection methods for transmission lines, particularly those involving asynchronous generators, suffer from significant errors due to differences in electrical characteristics between synchronous and asynchronous generators, leading to inaccurate fault location determination.
Innovation Solution
The method involves calculating apparent impedance by incorporating zero-sequence components, which are not restricted by converter control systems in inverter-based resources, thereby improving accuracy in distance protection for transmission lines with asynchronous generators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional distance protection methods are used for transmission lines with asynchronous generators, then the protection system can operate, but significant errors occur in fault location determination due to differences in electrical characteristics between synchronous and asynchronous generators
Solution Approach 1:
The patent changes the calculation parameters by incorporating zero-sequence components into the apparent impedance calculation. This modifies the traditional impedance-based distance protection method to account for the different electrical characteristics of asynchronous generators, thereby improving measurement precision without sacrificing adaptability to different generator types.
Solution Approach 2:
The patent introduces zero-sequence components as an intermediary element in the impedance calculation. These components act as a mediator that bridges the gap between the traditional protection method designed for synchronous generators and the actual electrical characteristics of asynchronous generators, enabling accurate fault location determination across different generator types.
2Measurement precision
If the apparent impedance calculation is performed using traditional methods, then the calculation is simple, but reactance shifts occur leading to inaccurate fault location
Solution Approach 1:
The patent modifies the calculation parameters by adding zero-sequence current components to the apparent impedance formula. This parameter change improves measurement precision by accounting for reactance shifts, while the mathematical formulation remains relatively straightforward, avoiding excessive complexity in the calculation method.
Data Source
AI summary
The present disclosure relates to a method for distance protection of a transmission line carrying a plurality of phases for a phase-to-phase-to-ground fault comprising a first phase and a second phase of the plurality of phases as faulted phases in the phase-to-phase-to-ground fault, wherein the first phase is different from the second phase, the method comprising: obtaining a first impedance of a first electrical loop formed by a first phase carried on the transmission line and a ground potential based on a zero-sequence current (S601); obtaining a second impedance of a second electrical loop formed by a second phase carried on the transmission line and a ground potential based on the zero-sequence current (S602); computing an apparent impedance of the transmission line and a ground potential based on the transmission line seen at a first terminal based on the first impedance and the second impedance (S603); and performing the distance protection based on the apparent impedance (S604). The present disclosure also relates to a respective device, computer-readable medium, and system.