Abstract:
A generator is installed on and provides electrical power from a turbine by converting the turbine&#39;s mechanical energy to electricity. The generated electrical power is used to power controls of the turbine so that the turbine can remain in use through its own energy. The turbine can be a safety-related turbine in a nuclear power plant, such that, through the generator, loss of plant power will not result in loss of use of the turbine and safety-related functions powered by the same. Appropriate circuitry and electrical connections condition the generator to work in tandem with any other power sources present, while providing electrical power with properties required to safely power the controls.

Description:
BACKGROUND 
       [0001]      FIG. 1  is a schematic diagram of a conventional turbine control system in commercial nuclear power stations. As shown in  FIG. 1 , a turbine  100  receives source steam  101 , extracts thermodynamic energy from the source steam  101 , and outputs lower-pressure, saturated steam  102 . Source steam  101  may be from a nuclear reactor, a heat exchanger, a steam generator, a higher-pressure turbine etc. Turbine  101  may be any turbine found in nuclear power plants, including a lower-output Reactor Core Isolation Cooling (RCIC) turbine or higher-output High Pressure Injection Cooling (HPIC) turbine, for example. The extracted energy  105  is used to power desired components; for example, in the case of an RCIC and HPIC, extracted energy  105  provides power to associated RCIC and HPIC cooling pumps that maintain flow and water levels in a reactor. 
         [0002]    When a turbine  100  is used to run cooling systems to maintain reactor coolant levels and remove decay heat from the plant, such as in a transient scenario, turbine  100  is controlled by a speed controller  60 . Turbine  100  generates speed information based on load and output and transmits the speed information  61  to speed controller  60 . Speed controller generates speed control signals  62  based on the received speed information  61  to be transmitted back to turbine  100 . Speed information  61  permits turbine  100  to operate at specified speeds and loads to avoid tripping and provide adequate power  105  to desired destinations. Speed controller  60  is conventionally networked with a flow controller  55  in the plant control room, which exchanges flow control signals  56  with the speed controller  60 . In this way, plant operators may monitor and input speed commands through the control room flow controller  55  that are translated into speed control signals  62  by speed controller  60  and ultimately control turbine  100  to perform in accordance with control room commands. 
         [0003]    Control room flow controller  55  and speed controller  60 , and data and signals generated thereby, are conventionally powered by offsite or plant power. As shown in  FIG. 1 , when such power is unavailable, such as during a station blackout event, a plant emergency power distribution source  50 , such as a local diesel generator or battery, may provide power  51  to control room flow controller  55  and speed controller  60 . By offering local power, emergency power distribution source  50  may permit operators to continuously control a speed of and use turbine  100  to manage the transient and/or provide power to safety systems, including Core Isolation and High Pressure Injection Cooling pumps. 
       SUMMARY 
       [0004]    Example embodiments include methods and systems for controlling turbine speed using the turbine&#39;s own power such that offsite power or local emergency power are not required to operate the turbine. Example systems include a generator connected to the turbine and generating power therefrom and connected to a controller for the turbine, such as a speed controller or control room flow controller governing turbine behavior. The generator may be of any appropriate power, voltage, frequency, etc. to power the controller and any other desired system. Example embodiments may further include circuitry connecting the generator, controller, and plant emergency power with isolation diodes between each power source and a filter to provide electrical power having properties required to power the controller. 
         [0005]    By installing and using a generator on a turbine in a nuclear power plant to power turbine controllers, the turbine may be operated and controlled through its own power without concern for offsite or local power. If the turbine drives safety-related pumps like RCIC or HPIC, at least the turbine may be operated and controlled through example embodiments and methods by plant operators to provide emergency cooling to a reactor that has lost offsite and onsite emergency power, as long as the turbine can be driven by decay heat or other steam sources. This may greatly extend core cooling capacity in some accident scenarios while eliminating any need for manual intervention to operate safety-related turbines. 
     
    
     
       BRIEF DESCRIPTIONS OF THE DRAWINGS 
         [0006]    Example embodiments will become more apparent by describing, in detail, the attached drawings, wherein like elements are represented by like reference numerals, which are given by way of illustration only and thus do not limit the terms which they depict. 
           [0007]      FIG. 1  is a schematic diagram of a conventional commercial nuclear reactor turbine flow control system. 
           [0008]      FIG. 2  is a schematic diagram of an example embodiment fault tolerant turbine speed control system. 
       
    
    
     DETAILED DESCRIPTION 
       [0009]    This is a patent document, and general broad rules of construction should be applied when reading and understanding it. Everything described and shown in this document is an example of subject matter falling within the scope of the appended claims. Any specific structural and functional details disclosed herein are merely for purposes of describing how to make and use example embodiments. Several different embodiments not specifically disclosed herein fall within the claim scope; as such, the claims may be embodied in many alternate forms and should not be construed as limited to only example embodiments set forth herein. 
         [0010]    It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of example embodiments. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
         [0011]    It will be understood that when an element is referred to as being “connected,” “coupled,” “mated,” “attached,” or “fixed” to another element, it can be directly connected or coupled to the other element or intervening elements may be present. In contrast, when an element is referred to as being “directly connected” or “directly coupled” to another element, there are no intervening elements present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between”, “adjacent” versus “directly adjacent”, etc.). Similarly, a term such as “communicatively connected” includes all variations of information exchange routes between two devices, including intermediary devices, networks, etc., connected wirelessly or not. 
         [0012]    As used herein, the singular forms “a”, “an” and “the” are intended to include both the singular and plural forms, unless the language explicitly indicates otherwise with words like “only,” “single,” and/or “one.” It will be further understood that the terms “comprises”, “comprising,”, “includes” and/or “including”, when used herein, specify the presence of stated features, steps, operations, elements, ideas, and/or components, but do not themselves preclude the presence or addition of one or more other features, steps, operations, elements, components, ideas, and/or groups thereof. 
         [0013]    It should also be noted that the structures and operations discussed below may occur out of the order described and/or noted in the figures. For example, two operations and/or figures shown in succession may in fact be executed concurrently or may sometimes be executed in the reverse order, depending upon the functionality/acts involved. Similarly, individual operations within example methods described below may be executed repetitively, individually or sequentially, so as to provide looping or other series of operations aside from the single operations described below. It should be presumed that any embodiment having features and functionality described below, in any workable combination, falls within the scope of example embodiments. 
         [0014]    Applicants have recognized plant emergency power distribution system  50  may become unavailable during plant transients. Indeed, it may be possible that the same transient event that cuts offsite power may render unusable emergency power distribution system  50 . In such a situation, turbine  100  may not be monitored, controlled, or potentially even used by plant operators in the control room to provide power output  105  to emergency systems or otherwise, because turbine speed controller  60  and/or control room flow controller  55  lack emergency power. Applicants have further recognized that turbine  100  itself may provide emergency electrical output if all other offsite and onsite power are lost, and that such power, if properly diverted, may be used to power speed controller  60  and control room flow controller  55 , such that operators may use turbine  100  to manage a plant transient even in the event of loss of all other power. Example embodiments and methods discussed below enable these and other advantages and solutions to situations appreciated by Applicants. 
         [0015]      FIG. 2  is a schematic drawing of an example embodiment fault tolerant turbine speed control system  1000 . As shown in  FIG. 2 , an electrical generator  500  is installed on turbine  100  and electrically connected to speed controller  60  and control room flow controller  55 . Generator  500  may be any type of generator, including AC or DC power generators, capable of generating voltage from mechanical energy  515  of turbine  100 . Generator  500  may be installed along a turbine shaft of turbine  100  and generate electrical power  551  from mechanical energy  515  output on the shaft. Existing mechanical output  105  may still be produced by turbine  100  in example embodiments. 
         [0016]    Generator  500  may be capable of delivering any amount of electrical power  551  that is sufficient to power connected systems, such as speed controller  60  and/or control room flow controller  55 . For example, generator  500  may be a 200 W DC generator that can power both speed controller  60  and control room flow controller  55  conventionally installed in nuclear power plants. Of course, generator  500  may have a much larger or smaller wattage, depending on need and mechanical power output of turbine  100 . If functionality of turbine  100  is desired for other components, such as coolant pumps powered by turbine output  105 , generator  500  may be rated at an electric power less than a difference between turbine  100 &#39;s capacity and required output  105 . For example, a 1 kW DC generator may power additional systems while not interfering with operations of a larger turbine  100 . 
         [0017]    As shown in  FIG. 2 , generator  500  is electrically connected to turbine controllers, such that if electrical output  51  from emergency power distribution system  50  becomes unreliable or unavailable (as indicated by “X” in  FIG. 2 ), electrical output  551  from generator  500  may supplement or replace electrical output  51  from emergency systems. Generator  500  may be electrically connected to a plant power network and thus electrically power plant components by installing an electrical connection or circuit between generator  500  and the network. 
         [0018]    Isolation diodes  505  and/or filter  501  may be installed or configured as desired to provide effective electrical current, voltage, power, frequency, timing, etc. to all components connected to the network. Isolation diodes  505  and/or filter  501  may ensure that such electrical power supplementing or replacing power from emergency power distribution system  50  matches voltage and power characteristics required to safely run emergency systems like generator  500 , speed controller  60 , control room flow controller  55 , and/or any other plant component that can be powered by electricity from generator  500 . Isolation diodes  505  may also ensure that power from generator  500  can reach consuming components on the electrical network regardless of malfunction or complete loss of emergency power distribution system  50 . For example, isolation diodes  505  may prevent or reduce reverse current surges to generator  500  and/or emergency power distribution system  50  so as to prevent damage or ineffectiveness in those components. Filter  501 , which may be a capacitor or battery, for example, may be grounded and smooth current and voltages applied to speed controller  50 , control room flow controller  60 , and any other component being powered by generator  500 . 
         [0019]    Alternatively, generator  500  may be directly electrically connected to desired components such as speed controller  60  and/or control room flow controller  55  so that those components may themselves switch to generator  500  electrical power  551  in the instance of failure of plant emergency power distribution system  50 . 
         [0020]    As shown in  FIG. 2 , when speed controller  60  and/or control room flow controller  55  are powered by turbine  100  through generator  500 , plant operators may continuously operate turbine  100  by monitoring and controlling the speed of the same from the control room via signals  61 ,  62 , and/or  56 . In this way, turbine  100 , and its output  105 , may be used even with a total failure of plant emergency power distribution system  50 . If turbine  100  is an RCIC, HPIC, or other transient- or safety-related turbine, mechanical power output  105  may be maintained to emergency systems, such as an RCIC or HPIC pump, through example systems using generator  500 . As long as a steam source  101  is available, such as from decay heat from a reactor or other source, turbine  100  may operate and be controllable in example systems, regardless of complete loss of station power and emergency electrical backups. As such, example system  1000  may permit prolonged use and control of turbine  100  to power other emergency systems that preserve reactor or plant integrity during a transient event. 
         [0021]    Example embodiments and methods thus being described, it will be appreciated by one skilled in the art that example embodiments may be varied and substituted through routine experimentation while still falling within the scope of the following claims. For example, although example embodiments are described in connection with RCIC or HPIC turbines in nuclear power plants, it is understood that example embodiments and methods can be used in connection with any turbine where loss of power affects the ability to control and/or use the turbine. Such variations are not to be regarded as departure from the scope of the following claims.