The turbine speed measurement and control system is actually composed of an independent speed measurement and control system. This article mainly introduces the microcomputer speed measuring device used in our plant. Its structure is simple, intuitive and easy to operate. It is mainly divided into three parts: (1) microcomputer monitor; (2) gear plate; (3) probe speed sensor. Its working principle is as follows: The gear plate is installed on the slip ring at the top of the generator shaft. It has 20 teeth, a rated speed of 1200 rpm, and a center frequency of 50 Hz. The gear plate rotates with the shaft and generates speed pulses. After scanning by the probe, the speed pulse signal is transmitted to the microcomputer monitor through the sensor. When the unit speed is as low as 35%, the underfrequency protection is activated. When the speed reaches 140%, the unit overspeed protection is activated. The microcomputer measurement and control device collects the unit speed in two ways: (1) residual voltage frequency measurement, also known as electrical speed; (2) gear plate speed measurement, also known as mechanical speed. The two modes are mutually redundant. The measurement method is flexible and reliable, making the unit operation very safe. 1. Features of the gear speed measuring device (1) It has an independent power supply system, with dual power supply, i.e., AC and DC power supply at the same time, and multiple signals are input at the same time, with high reliability. (2) Sensor disconnection lockout and fault alarm. The monitor adopts the mechanical speed priority rule, and displays the mechanical speed in normal state. When the probe sensor fails and cannot transmit the signal normally, the monitor will automatically switch to electrical speed and issue an alarm signal at the same time. (3) The contacts will not malfunction when the device is powered off. (4) Dynamic data display and full digital keyboard are used for human-machine dialogue, which is simple and easy to use. (5) When the sensor fails, the system can automatically reject the fault channel. The adoption of this mechanism can effectively suppress sudden interference and eliminate fault signals, which greatly improves the fault tolerance of the monitor and thus improves the reliability of the system. (6) The unit can still detect normally and give signals under creeping conditions. 2 Problems (1) Due to the processing flow, the tooth pitch of the gear plate is uneven. The probe is a highly sensitive speed sensor. It calculates the speed by scanning the gap between the teeth. Even if the unit speed is constant, the difference in tooth pitch will cause speed changes, thus generating interference. (2) Inaccurate roundness of the gear plate will also cause interference. (3) The swing of the turbine generator shaft will cause the gear plate to deviate from the center of the speed probe, which will also cause interference. 3 Solutions (1) The vibration of the main shaft will cause the gear plate to deviate from the center of the speed probe. This relative motion will generate low-frequency oscillation. Therefore, we must install the gear plate and speed probe according to the process requirements, use a dedicated shielded wire, and minimize the deviation as much as possible to improve the measurement accuracy. (2) The swing of the main shaft will affect the reception of the pulse signal. Therefore, we should pay attention to the fact that the center of the gear plate and the axis of the unit are on the same axis 1 during the installation process. That is, the smaller the concentricity, the better. (3) The most common way to eliminate the interference signal of the gear plate speed measuring device is to use a low-pass filter. 4. Conclusion Since its installation and use in our plant, the gear disc speed monitoring system has improved the stability of the operating units and enhanced the safety, economy, and reliability of the power plant operation.