Synchronous Generator Inter-Turn Fault Detection via Sequence Components
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Solution Overview
Problem
Existing methods for detecting inter-turn faults in synchronous generators, such as transverse differential protection and harmonic signature analysis, face challenges like high costs due to the need for numerous current transformers and reduced reliability due to external grid disturbances, making them impractical for high-power generators.
Innovation Solution
A method and system that utilize terminal-side measurements of voltage and current to transform into symmetric sequence components, monitoring negative and zero sequence residual voltages and coupling impedances to detect inter-turn faults without requiring additional dedicated measurement devices, allowing for reliable fault detection and protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If transverse differential protection is used to detect inter-turn faults, then detection sensitivity and reliability are improved, but the number of current transformers required increases, leading to higher costs and increased device complexity
Solution Approach 1:
The patent combines multiple measurement functions into existing terminal voltage and current measurements. Instead of using separate current transformers for each winding branch, the method utilizes standard terminal measurements combined with sequence component transformation to achieve fault detection, thereby merging multiple functions into existing measurement infrastructure.
Solution Approach 2:
The patent makes existing terminal measurements serve multiple purposes: normal power monitoring, fault detection, and diagnostic analysis. By using sequence component transformation on standard terminal measurements, the system achieves inter-turn fault detection without requiring dedicated measurement devices, thus giving universal use to existing measurements.
2Measurement precision
If current transformers are installed on each winding branch for transverse differential protection, then fault detection accuracy is improved, but installation difficulty increases when windings are inside the machine
Solution Approach 1:
The patent extracts the fault detection capability from the physical location of the windings and relocates it to the terminal side. By performing sequence component transformation on terminal measurements, the method brings the detection function to where measurements are already accessible, eliminating the need to access internal windings for installing measurement devices.
3Reliability
If harmonic signature analysis is used to detect inter-turn faults, then detection capability is improved, but reliability is reduced due to external grid disturbances and power electronic devices
Solution Approach 1:
The patent converts the harmful effect of grid disturbances and harmonics into a beneficial diagnostic tool. By analyzing the sequence components of terminal measurements, the method can distinguish between external disturbances and internal faults, effectively using the measurement data to identify true fault conditions while filtering out external noise.
Data Source
Figure 1a~1b
Figure 2~3
Figure 4
AI summary
A system, method and computer program product for monitoring including detecting internal faults especially inter-turn faults of a synchronous generator (1) and thus protecting the synchronous generator (1). The synchronous generator (1) comprises a winding (20, 23, 26) for each phase (a-c) of a power network (3), a terminal (5a-c) for each phase (a-c) arranged on a terminal side (4) of the synchronous generator (1), and connected to the respective winding, the terminals (5a-c) on the terminal side (4) is connected to an electrical power network (3), and the synchronous generator (1) is arranged to input power to the electrical power network (3) by means of the terminals (5). The method comprises measuring (301, 501) the voltage (Va, Vb, Vc) of each phase at the at least one each terminal and the current (Ia, Ib, Ic) of each phase at the terminal, determining (302, 305, 306, 502-506) whether the synchronous generator suffers from an internal fault in any of its phases. The determining includes transforming (302, 502) the measured phase currents (Ia, Ib, Ic) and the measured phase voltages (Va, Vb, Vc) into symmetric sequence currents (I1, I2, I0) and symmetric sequence voltages (V1, V2, V0), respectively. The method further includes monitoring (305, 505) at least one of the following variables: a negative sequence residual voltage (ΔV2); a zero sequence residual voltage (ΔV0); a negative sequence coupling impedance (Z2C); a zero sequence coupling impedance (Z0C); wherein each of the variables is calculated from symmetric sequence components (I1, I2, I0, V2, V0) and at least one generator specific impedance (Z00, Z22), and determining (306, 504, 506) whether the synchronous generator suffers from a winding fault, or not, from the calculated at least one residual voltage (ΔV0, ΔV2) or coupling impedance (Z0C, Z2C). The detecting system comprises a measurement circuit (40) arranged for measuring terminal phase voltages (Va, Vb, Vc) and terminal phase currents (Ia, Ib, Ic) measurements; a mathematical transformation provider (42) for transforming each phase voltages (Va, Vb, Vc) into symmetrical sequence voltage components (U1, U2, U0) and each phase currents (Ia, Ib, Ic) into symmetrical sequence current components (I1, I2, I0), and a winding fault determiner (44) adapted to detect internal winding faults in the synchronous generator from the negative sequence components (U2, I2), or the zero sequence components (U0, I0), of the voltages and currents.