1. Equipment Operation Status Before Modification Unit 9 of Shaoguan Power Plant is a 200 MW steam turbine unit of type N200-130-535/535 manufactured by Harbin Turbine Works. The unit's regenerative cycle is equipped with 3 high-pressure heaters, 4 low-pressure heaters, and 1 deaerator. The drain valves used for the high and low-pressure heaters are electric level regulators. Their working principle is to input the signal of the change in the drain water level in the heaters into the regulating system, and after comprehensive processing, control the actuator to adjust the drain flow by opening or closing the valve channel window, thereby controlling the heater water level. Similar to the currently used traditional float-type drain valves and pneumatic level regulators, after 1-2 years of operation, the electric level regulators frequently experience problems such as jamming, leakage, no water level operation, and severe erosion of the drain pipes due to frequent operation of the mechanical transmission components and actuators. Therefore, the failure rate is high, the reliability is poor, not only resulting in a large workload for maintenance and repair, but also reducing the turbine efficiency and affecting the unit's economic performance. A malfunctioning heater condensate drain leads to prolonged low or even no water level operation, causing a series of safety and economic problems. Economically, when the heater level regulator fails, the condensate from the current heater flows by gravity to the next stage, while a large amount of steam enters and vaporizes, releasing heat. This "displaces" the regenerative extraction steam from the lower stage, reducing the extraction steam volume and consuming more high-quality regenerative steam from the higher stage. This results in insufficient utilization of the steam enthalpy, significantly reducing the overall thermal efficiency of the unit's regenerative cycle. Furthermore, a large amount of steam-water mixture enters the deaerator, making it difficult to adjust and control its temperature and pressure. Safety-wise, a malfunctioning level regulator causes the heater to operate at a low water level for extended periods. Steam enters the condensate drain pipe, creating a two-phase flow of steam and condensate (in excessively low water levels, condensate can also easily "flash" due to pressure loss, similarly creating a two-phase flow). This increases the volumetric flow rate and velocity, causing the condensate drain pipe to vibrate with steam. Our plant's 200 MW unit relies on the first-stage high-pressure heater of the deaerator. Due to the long pipeline leading to the deaerator, there was a persistent problem of significant pipeline vibration before the condensate trap was upgraded. Despite multiple modifications to the pipeline, valves, and supports, this issue remained unresolved, threatening equipment safety. Simultaneously, the heater's operation with no or low water levels caused severe erosion of the condensate pipes and bends, rapidly thinning the pipe walls and leading to bursts during operation, resulting in accidents. In early 1995, a condensate pipe bend of a 200 MW turbine's high-pressure heater experienced a sudden burst during operation due to erosion from steam and water, causing pressurized condensate to spray tens of meters away. Fortunately, there were no casualties. 2. Overview of the Principle and Characteristics of a New Type of Self-Regulating Condensate Traps for Gas-Liquid Two-Phase Flow The self-regulating condensate trap for gas-liquid two-phase flow is a new type of condensate trap designed based on fluid mechanics theory and utilizing the flow characteristics of gas-liquid two-phase flow. It requires no external force; the actuator's power source comes from the steam in the heater, requiring approximately 1% to 2% of the heater's condensate flow. The self-regulating condensate trap mainly consists of two parts: a sensor transmitter and a main controller, as shown in Figure 1. The sensor transmitter sends water level signals and transmits the amount of steam for regulation, performing the measurement, transmission, setpoint setting, deviation comparison, and amplification functions found in conventional automatic control devices. The main controller controls the outlet water flow, functioning similarly to the actuator in a conventional automatic control device. Its regulation principle is as follows: when the heater's water level rises, the water level in the sensor transmitter rises accordingly, causing a decrease in the amount of regulating steam transmitted. Consequently, the amount of steam flowing through the two-phase flow in the main controller decreases, while the amount of water increases, causing the heater's water level to drop. The reverse is also true. This achieves automatic control of the heater's water level.