An improved combined cycle power plant and overspeed protection system of the type having a reheat stem turbine including a high pressure steam turbine section with at least one control valve, and a lower pressure steam turbine section. Overspeed testing to prove the actual value of trip setpoint of overspeed protection systems is an essential subsidiary function of governing systems. Overspeed protection for turbines cto a reliable overspeed protection system is indispensible for turbomachinery. The system must be based on three independent measuring circuits and twooutofthree voting logic. Seven papers react to the present demands of a changing electricity market by discussing such topics as electrohydraulic governors, the impact of market changes upon plant control, digital control for steam turbines, and steam turbine overspeed protection. The real values of critical speeds should be measured at. Turbine speed governing system plz use speakers youtube.
Interactions between turbine and boiler for large disturbances, the change in steam ow d hp results in an opposite change in steam pressure p c taking this into account requires to model the boiler and its controllers we only mention the boiler. We offer an inventory of specialty spare parts and short cycle delivery. Pdf power plant lecture notes chapter4 steam turbine. Electronic overspeed protection systems provide safe, simple, and reliable testing. The maximum output power of a wind turbine is also. Field adjustment of a mechanical overspeed governor can be a risky and costly exercise. For gas and steam turbines, this means reliable detection of overspeed and immediate closing of the trip valve in response.
The testing is carried out on an unsynchronised turbine. To regulate the speed of the turbine at various loads in a isolating set to regulate the load as per the frequency demand when working in a grid network. State a typical ilulge ofnmbackrates expressed as a per centageoffull powerper second. The overspeed resulted in severe damage to the low pressure turbine, the generator exciter unit, the condenser, and associated support structures, systems, and components. Operating experience feedback report turbinegenerator.
Turbine overspeed events lead to the most dangerous and costly of catastrophic turbine failures. Pitch systems, stall systems and brake systems all function to reduce net shaft torque and power at high wind speeds and rates of rotation. It includes an indepth examination of the turbine overspeed event which occurred on november 9, 1991, at the salem. The design provides protection from nuisance trips. Protection on the unit failed leading to rupture a fire broke out and it was rapidly brought under control. Power engineering 4th class ch 69 flashcards quizlet. It safely shuts down any plant process equipment, engine, or steam, gas, or hydro turbine upon sensing a safety event. Overspeed protection it is essential that wind turbines stop automatically in case of malfunction of a critical component. A protection system for a steam turbine generating plant for preventing excessive turbine speeds due to a partial loss of the electrical load, the generating plant comprising at least one highpressure and at least one lower pressure turbine, a generator rotated by said turbines, means for reheating steam passing between the high and.
The dynamic response of the steam turbine is influenced, mainly, by the entrained steam into high pressure turbine section and the storage action in the reheater. How steam turbine protection system works turbomachinery. Understanding and preventing steam turbine overspeeds by. Background rotating equipment, particularly steam turbines, generally employ control systems that perform a variety of functions, including tripping.
Intelligent solutions for hydro governors asme ptc 292005 speedgoverning systems for hydraulic turbinegenerator units iec 308 international code for testing of speed governing systems for hydraulic turbines iec 662 guide to specification of hydraulic turbine control systems iec 611 programming industrial automation systems. Three speed signals are process ed and interrogated on separate speed detector io modules. Cam type of control valvecams mounted on a shaft are another lifting. In a practical situation the load frequently varies from the designed or economic load and thus there always exists a. As discussed in the section on high vs low rpm units, there are limits to how fast motors and rotors can operate. Above 600 rpm rotor relative vibrations should be monitored. In a steam turbine control system three overspeed protection circuits opc are provided, each one being identical to the others and each having a programmable digital computer in twoway data communication with a master controller, as well as with the other opcs. Course 234 turbine and auxiliaries module seven approval issue pagel8 7. A multivalve, multistage turbine protection system. If a steam turbine has an electronic overspeed protection system, that system is typically designed to be tested while the turbine is in normal operation by electronically sending an overspeed signal to the system.
This system is completely independent of the turbine speed governor. Introduction if the overspeed trip protection of a steam turbine fails to function at the design set speed, turbine buckets or a section of a wheel can break free of the rotor and, in a worst case scenario, penetrate the turbine casing. Additionally, an overspeed may be caused by a governor failure on an unsynchronised turbine causing an excessive steam demand. There is some overlap between control and overspeed protection. Steam turbine mechanical overspeed trip devices aig. New method for the protection of gas turbines against.
Understanding and preventing steam turbine overspeeds by william e. The protection system operates only when any of the control system set point parameters are exceeded, and the steam turbine will be damaged if it continues to operate. The function of the steam turbine protection system is often confused with the control system, but in fact the two systems are entirely separate. The modern digital turbine control system tcs is designed to control the main steam flow to the steam turbine in all operational conditions by means of the turbine throttle, governor, admission. Api 670 overspeed protection discussion updated 92008. Operators observed increasing noise and vibration from the turbine and a fire at the generator.
Governing and protection system linkedin slideshare. This standalone safety device accepts 10 discrete or analog inputs per module 30 total and one speed mpu or proximity probe input 3 total. A speed sensing device, usually a centrifugal flyweight type governor driven through worm and bevel gearing from the turbine shaft. This turbine is equipped with an overspeed trip to protect. The variation in load during the operation of a steam turbine can have a significant impact on its performance. Steam turbine governing and overspeed protection imeche seminar publications pep professional engineering publishers on.
Examined more closely herein are the characteristics of a steam turbines components and evaluation as to possible involvement in loss of control of a machine. When a turbineload unit is connected and synchronized to the grid, the speed cannot. The governing systems for thermal and hydro generating plants are different in nature since the inertia of water that flows into the turbine presents additional constraints which are not present. Overspeed protection for a gas turbinesteam turbine. Electronic overspeed systems are very reliable, and come with modern features such as a testable set point and speed rate of change detection. Speed transducers adjacent the turbine shaft provide speed indicative signals to the respective opcs which. A turbine unit is built to safely operate up to a specific speed.
Steam turbine governing and overspeed protection imeche seminar publications. The voith cto overspeed protection system provides both functions in a single device. Learn vocabulary, terms, and more with flashcards, games, and other study tools. To prevent and protect the turbine from over speeding. If a steam turbine has a mechanical overspeed trip device, it should be tested at least annually. Friction losses, leakage losses, external losses, turbine governing and control. The overspeed trip is the final protection against catastrophic failure of the turbine following a load rejection, causing the unit to become disconnected from the power system. Power generation hydro power intelligent solutions for. State thedifference between latchedand unlatchedronbacks. In the simplest form the overspeed protection system must detect when operating speed is exceeded. Approaches that the specialists of the zao ural turbine works use in constructing and organizing the steam turbine protection system as part of the electrohydraulic control system are presented. The woodward tg series, constant speed, oil relay governor is standard equipment for.
Turbine failure during overspeed testing statutory turbine testing later reported as an overspeed test ended in severe mechanical damage performed wednesday night 9 february 2011 the unit was not on load. Us20080284a1 gas turbine overspeed protection system. An overspeed protection system for a gas turbine engine comprises. Steam turbine governing and overspeed protection imeche. The great majority of steam turbine governing systems utilize the a hydraulic system principle b pneumatic system principle. Wind turbine safety amirkabir university of technology. Vop 03 data sheet description the vop 03 triple voting overspeed protection unit is a two out of three voting system to protect turbo machinery from overspeed. He retired fro m amoco oil company, after more than 36 years in. Most overspeed trip mechanisms are set to trip the unit at 110% of rated speed, but most turbinegenerators are designed to temporarily operate at up to 120% of rated speed. Steam turbine over speed trip systems prem baboo sr. Nelson turbomachinery consultant dickinson, texas and perryc. The modern overspeed protection system for steam turbines. One the threshold is exceeded, automatic trip of turbine takes place.
Summary gasturbine generator sets, in particular with aeroderivative gas turbines, are sensitive to electrical fault events that can damage the gasturbine. Utility steam turbine controls industrial steam turbine controls hydro turbine controls. A wind turbine is a device designed to utilize the kinetic energy of wind and convert it to electrical energy. The trip speed setting will vary with the class of governor see 3. In the simplest form the overspeed protection system must detect when operating speed is exceeded by a designated percentage often 10% to % and must initiate successful closure of all valves to isolate any and all potential steam energy sources. Below are excerpts from the paper, turbine overspeed systems and required response times by scott l taylor of. Turbine governing system an overview linkedin slideshare.
The ability to test the correct functioning of each turbine steam valve is necessary for both onload operation and also prior to run. Electronic turbine overspeed protection data sheet page 2 overspeed protection is achieved by using a two out of three voting trip system. Traditionally, overspeed protection systems were designed and provided by the original equipment manufacturers oemsfew options were available either in terms of testing or modifying these systems. The tps detects undesirable operating conditions and initiates trips to avoid damaging the steam turbine. Steam turbine governing and overspeed protection book. Online redundancy in a hot standby arrangement for turbine governor processors. Steam turbine governing and overspeed protection pep. Mechanical overspeed testing of nuclear safetyrelated turbines without driving steam little j. Turbine overspeed events lead to costly and dangerous catastrophic failures. Over speed protection mechanisms for wind turbines.
The low pressure turbine blades penetrated the turbine shroud. In addition to the constant speed governor an overspeed governor or emergency trip is also fitted. For example, some machines use passive pitch systems to moderate power levels with furling for overspeed protection, e. On the second test, the mechanical shutoff valve did not function properly and allowed the turbine to reach an overspeed condition. If a steam turbine has an electronic overspeed protection system, that system is typically designed to be tested while the turbine is in normal operation by electronically sending an.
Elec0047 power system dynamics, control and stability. The tutorial concentrates on the appropriate complete control system, including overspeed protection systems that will be required to operate a steam turbine in. A typical wind turbine starts generating electricity when the wind speed is 24 ms, otherwise known as cutin wind speed and achieves its maximum output power at rated wind speed which is generally 1217 ms. Mechanical governors are sensitive to ambient conditions and have components.
Oil refineries have a lot of rotating machinery, including turbines, so they have taken the lead in developing standards for turbine protection. Us4635209a overspeed protection control arrangement for. The turbine protection system tps provides an additional independent protection function for the steam turbine and generator. Steam turbine governing is the procedure of controlling the flow rate of steam to a steam turbine so as to maintain its speed of rotation as constant. Protection of gas turbines against overload and overspeed generator gear box gas turbine 1. Data and experiences of one insurance company in several areas failure for steam turbines were presented by clark 1. Proceedings of the may 1998 seminar held in may 1998 and organized by the steam plant committee of imeche. Therefore the overspeed system has to be periodically tested to ensure the system has the adequate response time to protect the turbines, plants and personnel. If there is a glitch on one of the three channels only that individual channel will trip. The overspeed trip test consisted of allowing the turbine to accelerate to a particular rpm speed to test a mechanical shutoff valve that would prevent the turbine from accelerating to a dangerous speed. Speedgoverning system speed governing systems consist of three main elements.