Generator Ground Brush Lift Detection via Rotor Shaft Voltage
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Solution Overview
Problem
In wind turbines, the lifting of the ground brush can lead to undesirable rotor shaft voltage discharges, causing bearing failure due to the lowest impedance path through the bearing housing, which is not effectively detected by existing technologies.
Innovation Solution
A method and system that monitor the rotor shaft voltage using sensors to detect characteristics such as amplitude and frequency, determining if they exceed predetermined thresholds, indicating a lifted ground brush, and implementing control actions to prevent damage, such as opening a normally closed contact to alert operators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ground brush lifting is not detected, then bearing damage occurs due to voltage discharge, but adding detection systems increases device complexity
Solution Approach 1:
The patent replaces complex mechanical detection systems with electrical measurement. Instead of using mechanical sensors or physical inspection methods to detect ground brush lifting, the system monitors rotor shaft voltage characteristics electrically. This substitution reduces device complexity while maintaining reliable detection capability, directly resolving the contradiction between bearing reliability and detection system complexity.
Solution Approach 2:
The system uses the existing rotor shaft voltage signal that is already present in the generator system to detect ground brush lifting. Rather than adding separate detection hardware, the invention utilizes the electrical parameters already inherent in the system's operation. This self-service approach minimizes additional device complexity while ensuring reliable bearing protection through continuous monitoring.
2Reliability
If voltage discharge through bearing housing is prevented, then bearing failure is avoided, but ground brush lifting remains undetected without monitoring
Solution Approach 1:
The patent implements a feedback mechanism by continuously monitoring rotor shaft voltage characteristics and comparing them against expected values. When ground brush lifting occurs, the voltage characteristics change, and the system detects these changes through ongoing measurement and analysis. This feedback loop enables real-time detection of ground brush lifting, resolving the difficulty of detecting and measuring this condition while simultaneously protecting bearing reliability.
Solution Approach 2:
The invention replaces difficult mechanical detection of ground brush lifting with electrical measurement of rotor shaft voltage. Instead of attempting to physically detect brush contact status, the system measures electrical parameters that change when lifting occurs. This substitution makes detection feasible and reliable, directly addressing the difficulty of detecting and measuring ground brush lifting while maintaining bearing reliability.
3Loss of time
If rotor shaft voltage is monitored continuously, then ground brush lifting is detected timely, but energy consumption increases
Solution Approach 1:
The patent applies partial monitoring by focusing measurement efforts on specific voltage characteristics that indicate ground brush lifting, rather than continuously analyzing all voltage parameters. The system monitors for specific threshold conditions or characteristic patterns in the rotor shaft voltage, enabling timely detection of ground brush lifting while reducing overall energy consumption compared to exhaustive continuous monitoring of all electrical parameters.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively reduces the occurrence of generator bearing failures, allowing for timely intervention and reducing maintenance costs, while also being applicable for testing and retrofitting existing units without disassembly.
Implementation Method 1
a rotating magnetic field may be induced by the generator rotor and a voltage may be induced within a generator stator. Rotational energy is converted into electrical energy through electromagnetic fields coupling the rotor and the stator
Implementation Method 2
Capacitive coupling between the rotor and the stator, though not the main contributor to the generated power, can induce an undesirable rotor shaft voltage in the rotor
Data Source
AI summary
The present subject matter is directed to a system and method for detecting lifting of a ground brush of a generator of an electrical power system connected to a power grid so as to prevent damage to the electrical power system (e.g. bearing failure). The method includes monitoring, via at least one sensor, a voltage signal of a rotor shaft of the generator. The method also includes determining at least one characteristic (e.g. amplitude and/or frequency) of the voltage signal for a predetermined time period. Further, the method includes determining whether the at least one characteristic of the voltage signal is above a predetermined threshold, wherein the at least one characteristic of the voltage signal being above the predetermined threshold is indicative of the ground brush being lifted.