**Turbine Unit Bearing Temperature False Tripping: Causes and Solutions** Home > Bearing Knowledge > Water Turbine Unit Bearing Temperature False Tripping Causes and Solutions /*728*90 created on 2018/5/16*/ var cpro_id = "u3440131";

Turbine Unit Bearing Temperature False Tripping: Causes and Solutions

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**1. Introduction** Bikou Hydropower Station is equipped with three mixed-flow hydroelectric generating units, each with a capacity of 100MW, manufactured by Harbin Electric Machinery Factory. The original temperature measurement system used ratiometric equipment with reed switch contacts, which had low reliability and affected the monitoring of unit temperatures and normal readings by operators. In response to the need for computerized monitoring, the temperature circuits were upgraded in late 1996 using the DAS-IA/B series multi-function inspection instrument from Hefei University of Technology High Technology Industrial Company. However, this system suffered from poor anti-interference capability, unstable connections, and frequent communication issues, especially due to the strong electromagnetic environment around the generator. These problems often led to false high-limit alarms, overloading the monitoring system and even causing server crashes. **2. Analysis of False Tripping Due to Bearing Temperature** On August 30, 2001, during operation at full load (100MW), the 1# unit experienced an abnormal temperature reading. After checking, it was found that the common terminal of the temperature circuit was loose. When maintenance personnel tested the resistance using a multimeter, the loose connection caused a sudden increase in the measured resistance, triggering a high-limit alarm and leading to the unit's emergency shutdown. Further simulations confirmed that a loose common terminal could cause false temperature readings, as the resistance value increased due to the open circuit. This result matched the incident, confirming that the loose terminal was the root cause. In the microcomputer monitoring system, the bearing temperature trip logic relied on data from the temperature inspection instrument. However, the system had several operational defects: (1) The temperature data collected was highly susceptible to interference from the generator’s magnetic field, leading to drift and false alarms. (2) The system lacked robustness in distinguishing between real and false signals, making it difficult to handle disturbances effectively. (3) If the temperature inspection instrument failed, all temperature protection systems would be disabled, increasing the risk of serious incidents. **3. Renovation Plan for the Temperature Trip Circuit** To address these issues, the following improvements were implemented: - **3.1** A temperature control cabinet was installed near each unit, separating the original temperature control loops for water guide, thrust, and upper bearings from the inspection instrument. - **3.2** XMT-800 digital controllers were added to each unit to independently collect and process temperature data, reducing reliance on the previous system. - **3.3** Dual temperature measurement components were used for critical points, with one input going to the microcomputer controller and the other to the local control unit (LCU). A time delay was added to the logic loop to differentiate between true and false signals, significantly improving the system's reliability. **4. Key Considerations During the Renovation** - **4.1** The temperature trip circuit was redesigned to use an independent control loop, with separate connections for each bearing. This allowed maintenance personnel to inspect individual thermometers without affecting other measurements. - **4.2** Thermometer leads were made of oil-resistant, temperature-resistant twisted-pair shielded cables, with grounded shielding layers to reduce interference. - **4.3** All resistance thermometers were thoroughly checked for open or short circuits after installation. - **4.4** Thermometers were placed as close as possible to the tile surface to minimize hysteresis and temperature decay. - **4.5** The temperature trip circuit upgrade was carried out during the unit’s overhaul to ensure minimal disruption. **5. Conclusion** After implementing the above improvements, the 2# unit was officially put into operation on February 6, 2002, and operated safely for more than two years until July 31, 2004. The transformation successfully resolved the issue of false tripping, ensuring reliable and safe operation of the turbine units. --- **Related Bearing Knowledge** Preparation for the installation of NSK rolling bearings. Locking method for two bearings. Strategies for reducing bearing noise. Detailed discussion on the repair of centrifugal compressor thrust bearings and pump shaft bearings. This article is linked to http:// Please indicate the bearing network: http:// Previous: Analysis of the Application of SKF Bearings Next: Development and Classification of Spherical Roller Bearings

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