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Testing and adjustment of the turbine control system 1. What is the purpose of testing the control system? (1) To determine the static characteristics, speed response time, delay rate, and dynamic characteristics of the control system, thereby assessing its overall performance； (2) Defects that are difficult to detect during normal operation are identified through testing, and their causes are analyzed accurately, providing necessary and reliable evidence for eliminating these defects. 2. What is a static test of the control system? A static test of the control system is conducted by starting the high-pressure auxiliary oil pump while the turbine is at rest, in order to test the control system. Since the turbine is at rest, there are few interfering factors during testing, allowing for relatively accurate results to be obtained. For newly installed and overhauled units, static tests can be used to adjust the relationships between various components to meet design requirements, thereby providing the necessary conditions for safe and reliable startup and operation. For defective or improved units, the interrelationships among various components are measured through static tests, and these values are compared with the design data in order to identify the causes of the defects or assess the effectiveness of the improvements. 3. What parameters can be measured in a static test? (1) The relationship between the governor signal (sliding sleeve displacement or primary pulse oil pressure) and the travel of the hydraulic actuator, as well as the secondary pulse oil pressure ； (2) Relationship between the oil actuator stroke and the opening degrees of various control steam valves ； (3) Operating stroke of the governor sleeve and hydraulic actuator ； (4) Operating range of the synchronizer ； (5) The delay rate of the transmission amplification mechanism. The items recorded in the static test mainly include: governor sleeve travel (or primary pulse oil pressure), hydraulic actuator travel, opening degrees of various control valves, synchronizer travel, and secondary pulse oil pressure. 4. How is the static test conducted? During the static test, the turbine is not yet running; therefore, the main oil pump does not operate. The pressure oil is supplied by a high-pressure auxiliary oil pump, and the speed signal is generated manually. For units equipped with low-speed centrifugal governors, remove the main spring of the governor and install a special tool to move the position of the sliding sleeve ； For high-speed reed governor systems, a synchronizer can be used to move the position of the governor’s throttle piston ； For the hydraulic governor, the original primary pulse oil circuit is disconnected, and an artificially generated adjustable oil pressure is used in its place. To make the test reflect operating conditions, the oil temperature should be maintained within the range of 45°C ± 5°C. During the test, move the governor sleeve or change the pulse oil pressure; make the first recording when the hydraulic actuator begins to close. Record once after each movement until the hydraulic actuator is completely closed, with a total of no less than 8 recording points. Conduct the opening direction test after the oil actuator is fully closed. It must be noted that when conducting the direction-of-shutdown or startup test, it can only be carried out in one direction; back-and-forth movement is not allowed, otherwise the delay rate cannot be determined. After the test, the test records are compiled, the errors in the instrument readings are corrected, and curves are plotted. 5. What are the contents of the tests for the automatic main steam valve and the control steam valve? The contents of these tests are: (1) Integrity tests for the automatic main steam valve and the control steam valve ； (2) Shutdown time test. 6. What is the purpose of the tightness test? How is it carried out? The purpose of the tightness test is to check the degree of tightness with which the automatic main steam valve and the control steam valves close. (1) For the tightness test of the automatic main steam valve, under the rated parameters for fresh steam, exhaust pressure, and rotational speed, the steam valve is adjusted to be in the fully open position; the automatic main steam valve is then closed, and simultaneously the variation of the turbine’s rotational speed over time is recorded. It is generally required that after the automatic main steam valve is closed, the turbine’s rotational speed drops rapidly to below 1000 rpm. (2) The tightness test of the control steam valve is conducted under the rated parameters for fresh steam, exhaust pressure, and rotational speed, with the main steam valve in its fully open position; the control steam valve is then closed, and the variation of the turbine’s rotational speed over time is simultaneously recorded. This relationship should be essentially consistent with the curve obtained when shutting down under the same conditions. 7. What is the purpose of the closing time test? How is it conducted? The closing time test is used to measure the closing time of the automatic main steam valve control devices, as well as those of the oil-driven mechanisms that are used to close the valves, in order to determine whether their response speed meets the required standards. The tests were conducted in both stationary and no-load conditions (with steam parameters at rated values). The test method is: (1) Use a chronometer for measurement; the wiring requirement for the chronometer is that it should be activated when the automatic main steam valve and the control steam valve begin to close ； The electric stopwatch stops when the steam valve is completely closed. Before the test, both the automatic main steam valve and the control steam valve are in the fully open position (when testing under no-load conditions, the control steam valve can be kept fully open by reducing the opening degree of the electric main steam valve bypass). During the test, manually operate the emergency cut-off switch and record the closing times of the automatic main steam valve and the control steam valve. (2) Measurement using a data recorder: Recording the closing process with a data recorder allows for more accurate determination of the closing time and facilitates analysis. Stroke signal transmitters are installed on the automatic main steam valve and the hydraulic actuator to convert displacement signals into electrical signals, which are sent to the recorder; at the same time, these signals also serve as the tripping signals for the emergency shutdown device (indicating the time when tripping begins). During the test, the manual emergency cut-off switch is activated, and the recorder automatically records the closing process of the main steam valve and the control steam valve. 8. What tests should be conducted on the overspeed protection device? How are they carried out? To ensure the reliability of the overspeed protection device during the operation of the turbine, it is necessary to conduct tests on this device in accordance with relevant regulations after the turbine is installed, after each major overhaul, or after 2000 hours of operation. These tests include: (1) Manual test: The purpose of this test is to check whether the emergency shutdown valve, the automatic main steam valve, and the control valves function properly. The tests are conducted with the turbine at rest and under no-load conditions, and can be carried out simultaneously with the tightness tests and closing time tests of the automatic main steam valve and the control steam valve. (2) Oil injection test: Large steam turbine units are equipped with oil injection test devices for emergency safety valves, which allow tests to be conducted either under no-load conditions or under load. The no-load oil injection test can determine the oil injection kick-out speed of the emergency safety device. The load-bearing oil injection test is a test to verify the operation of the emergency safety device while the system is operating under normal load conditions. During the test, the trip device of the safety device under test is disconnected from the normal operating system (at this time, the other safety device and its trip device remain in normal operation and can still provide protection), and it is connected to the testing system. After the test is completed, it is returned to normal operating status, after which the test is carried out on the other safety device. (3) Over-speed test: The purpose is to determine the actual operating speed of the emergency safety device. The test was conducted under no-load conditions. During the test, the speed is raised to its maximum using a synchronizer, and then the speed is increased slowly with an overspeed testing device in order to trigger the emergency shutdown device, with the speed at which this occurs being recorded. 9. What issues should be considered when conducting an overspeed test? The following points should be taken into account when performing an overspeed test: (1) The test should be carried out twice under identical conditions, and the difference between the rotational speeds during these two tests should not exceed 0.6% of the rated speed. For newly installed or overhauled units, a second test should be conducted; the difference between the speed at which it operates during this second test and the average of the speeds at which it operated in the previous two tests should not exceed 1% of the rated speed. (2) If the unit has two emergency safety devices, an no-load test is conducted first to determine which one operates at a lower speed. Using the oil injection test apparatus, switch the test handwheel to the emergency shutdown device with a lower operating speed, so that the operating speeds of both emergency shutdown devices can be measured simultaneously in a single test. (3) For high-power units, sufficient warm-up time should be available before the overspeed test to prevent the rotor metal temperature from dropping below the brittle transition temperature, which could affect the safety of the unit; this is particularly important for units that start under sliding parameter conditions. 10. When the operating speed of the emergency safety device does not meet the requirements, how should the adjustment be made? If the manufacturer provides values indicating how many turns the adjustment nut needs to be turned in order to change the operating speed, then the number of turns required can be calculated using the following formula: L0 = (n – n0) / nm. Here, L0 represents the number of turns the adjustment nut needs to be turned ； nm: The value specified by the manufacturer for the change in speed of the movement per rotation of the adjustment nut, in rpm ； n: Operating speed of the emergency safety device before order adjustment, rpm ； n0: The specified operating speed at which the emergency safety device activates, in rpm. If the nm values provided by the manufacturer are not available, the following method can be used to determine the number of turns required for adjustment: If the speed at which the emergency safety device activates is measured as n1 for the first time, turn the adjustment nut L1 by L1 turns (usually L10); the adjustment should be made in the direction that increases the speed ； If L0