Fault Location in Ring Supply Networks Using Negative Sequence Components
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Solution Overview
Problem
Conventional protection systems in electrical networks with a ring structure struggle to accurately determine fault locations, especially when decentralized energy conversion systems are connected, leading to delayed error rectification and increased operational challenges.
Innovation Solution
A method using symmetrical components to divide an asymmetrical multi-phase system into a symmetrical positive, negative, and zero system, calculating total residual currents and pre-fault impedance to determine fault locations based on negative system resistance or reactance, which is implemented in conventional protection devices as a computer program.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the ring structure is closed to increase capacity for decentralized energy conversion systems, then the network capacity increases, but conventional protection systems no longer work correctly leading to inaccurate fault location determination
Solution Approach 1:
The patent changes the measurement parameters from conventional single-frequency voltage and current measurements to negative sequence component measurements. This parameter transformation allows the protection system to operate correctly in ring structures with decentralized energy conversion systems, as negative sequence components are uniquely generated by asymmetrical faults and are not affected by the bidirectional power flow or variable impedance characteristics introduced by DEA systems.
2Adaptability or versatility
If decentralized energy conversion systems are connected to increase renewable energy integration, then energy conversion capacity increases, but the blinding effect and opposite feed cause measurement errors
Solution Approach 1:
The patent extracts the negative sequence components from the complex electrical signals containing both fundamental frequency components and harmonics. By separating and analyzing only the negative sequence components, the method eliminates the blinding effect caused by decentralized energy conversion systems and the opposite feed, as these phenomena do not generate negative sequence components under normal operating conditions.
3Reliability
If non-directional short-circuit indicators are used for fault detection, then the protection coverage is provided, but the faulty line section cannot be isolated due to fault supply on both sides
Solution Approach 1:
The patent utilizes the asymmetrical nature of negative sequence components that are generated only by asymmetrical faults. By measuring negative sequence currents and voltages, the system can determine the direction and location of faults even in ring structures with bidirectional power flow, enabling precise fault isolation while maintaining comprehensive protection coverage.
Data Source
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AI summary
The invention relates to a method for determining the site of a fault in a supply network with a ring topology (R), wherein the ring topology comprises at least two outgoing circuits (A, B) each connected to a busbar (S) via a protective device (SR1, SR2) and a connection connecting the at least two outgoing circuits, wherein a dependency of a ring topology location on a negative sequence resistance and/or negative sequence reactance of the ring topology is specified, wherein a length of a fault path is defined by the distance between a fault site (F) and a protective device, the symmetrical components method being used to carry out the method in which an asymmetric multi-phase system of phasors is divided into a symmetrical positive sequence component, a negative sequence component and a zero sequence component and wherein, if a counter-current excitation on a protective device exceeds a defined threshold value, the following steps are executed: calculating a total fault current flowing into the negative sequence, measuring a partial fault current flowing in the fault path by means of at least one of the protective devices connected to the fault path and calculating a resulting pre-fault impedance, calculating a partial negative sequence resistance or partial negative sequence reactance of the fault path using the pre-fault impedance, and determining the site of the fault from the partial negative sequence resistance or from the partial negative sequence reactance.