ML20043F659
| ML20043F659 | |
| Person / Time | |
|---|---|
| Issue date: | 02/12/2020 |
| From: | Office of the Chief Human Capital Officer, Woodard Corp |
| To: | |
| Gary Callaway | |
| Shared Package | |
| ML20043F634 | List:
|
| References | |
| Download: ML20043F659 (39) | |
Text
Emergency Diesel Generator Diesel Engine Controls and Governing 8.0 DIESEL ENGINE CONTROLS AND 8. Understand the use of other (digital)
GOVERNING governing systems.
This chapter presents the principles of the 8.1 Control Fundamentals governing system which controls the power output by the engine. It is the electrical 8.1.1 Diesel Engine to Generator demand on the generator that sets the load Relationship demand on the engine. The governor controls the fuel to the engine to establish In the application of Emergency Diesel the speed of the engine, and thereby the Generators (EDGs), the primary objective is frequency of the generator. to provide the electricity needed to operate the plant safety-related systems, allowing Learning Objectives operators to achieve and maintain a safe reactor shutdown condition.
As a result of this lesson, you will be able to:
EDGs consist of two physically and
- 1. Describe the functional relationship functionally related components. The driven between the engine control governor and component, the electric generator, produces the fuel injection system. the power required to safely operate plant systems in the event of a loss of the plant
- 2. Explain how the engine control governor primary power sources. The driving senses changes in the generator load or component, the diesel engine, converts demand and compensates by regulating energy supplied in the form of fuel oil into the fuel delivery to the diesel engine. mechanical energy. During opera-tion of the EDG, the power (voltage and current)
- 3. Describe the primary components of the produced by the generator is regulated by governing systems, their features and the generator excitation system.
function.
As discussed in Chapter 4, power output of
- 4. Explain how the terms isochronous and the diesel engine and therefore power input droop apply to the diesel generator set to the generator is controlled by regulating engines. the quantity of fuel delivered to the engine cylinders. In turn, the regulation of the fuel
- 5. Explain how the EDG is synchronized is controlled by the engine control governor.
with the grid for periodic test loading.
The relationship between the generator
- 6. Explain rack boost and how it provides output frequency and the engine speed is for faster starts. expressed by the formula:
- 7. Describe the overspeed trip, how it =
120 operates to shut down the EDG (even during emergency loading), and how it is Where F is frequency, N is the engine speed reset (manually). in RPM, and P is the number of poles on the Rev 3 /16 8-1 of 39 USNRC HRTD
Emergency Diesel Generator Diesel Engine Controls and Governing generator. A 900 rpm engine requires an 8- equal time, meaning the speed is constant.
pole generator to produce 60 Hz power. For 'Droop' indicates something is falling off or 60 Hz, the following formulas are derived: drooping. As applied to an EDG, it means that as load is applied engine speed drops.
7200 7200 The following explains how these terms are
= and = applied to the diesel generator and why droop is required.
8.1.2 Governor Principles If the diesel generator is operating alone on Chapter 4 discussed the very basic an electrical system, not connected to other principles of the governing of the engine generators, it is most desirable to have the through a system that controls the amount generator maintain its frequency (speed) of fuel delivered to the engine cylinders regardless of the load. In other words, through the control of the fuel injection 'isochronous' operation. However, if that equipment on the engine. This section will same unit were put on a system with other expand upon the governing system aspect generators, and particularly a very large of the engine control system. The governing system like the grid (infinite bus), there is a system monitors the speed and / or load on potential problem. If the EDGs frequency the unit and regulates the fuel injection (speed) is even a little higher than system system to attempt to hold the speed of the frequency, it will attempt to bring the system unit constant. We will explain how this is up to its frequency. The only way it can do done with various governing systems used that is to attempt to carry the whole system on EDGs in nuclear power plants. load. This would result in the new unit being overloaded, and could damage it without the 8.1.2.1 Isochronous-Droop Relationship overload trip circuit breaker (Chapter 10).
The EDG governing system has to meet the If EDG frequency (speed) is just a little lower challenge of controlling the generator when than system (grid) frequency, the grid will connected into a large system with other attempt to bring EDG up to its frequency.
generators. A very large system is often The only way to do that is to drive the new referred to as an 'infinite bus' or 'the grid.' unit (i.e., motorize the generator), bringing Some means must be provided to allow the EDG up to grid frequency. The unit will control of a single EDG while paralleled with now be running faster than its governor the grid, or with other generators. speed setting, so the governor will back off the fuel and the unit will simply operate as a Two terms have come into usage for motorized unit. This is not harmful to the describing the requirements of control in a generator or the engine, provided that fuel governing system. The first is 'isochronous;' flow is maintained to the fuel injection the other is 'droop.' The word 'isochronous' components, to lubricate them. The term can be broken into two parts - 'iso' meaning 'reverse power' is applied to this condition,
'equal' and 'chronous' relating to 'time.' As and it will be discussed further in Chapter applied to an engine, isochronous means 10, "Emergency Diesel Generator Control that each revolution of the engine takes an and Monitoring."
Rev 3 /16 8-2 of 39 USNRC HRTD
Emergency Diesel Generator Diesel Engine Controls and Governing Droop in a governing system is defined as during the actual load change and the unit's the change in speed the unit makes in going subsequent recovery time).
from no load to 100%. The percentage droop can be computed as follows:. If the unit were operating alone (on an isolated system) with droop, then the
()100 operator would dial in the desired speed. As
=
the unit were loaded, the speed would drop.
To compensate for the speed drop, the One means of determining the droop is to operator would have to continuously adjust run the unit at 100% load with the speed the speed reference up in order to arrive at adjusted to 60 hertz. Trip the load breaker the rated speed at 100% load.
open, and the unit will end up at a higher speed. This is the no-load speed. Apply the Two lines are shown on the chart going formula above to compute the percent through 100% load and rated speed (60 hz) droop.
one for 3% droop (solid line) and one for 5% droop (dashed line). Note that the speed Speed droop in a simple governor can be reference is now at 61.8 Hz and 63 Hz provided by a device which consists of a respectively for the 3% and 5% conditions.
lever of suitable ratio between the actuator speeder spring and actuator output shaft.
Since the operator cannot change the system speed, his only means of loading the Droop is introduced into the governing unit against the system-maintained speed is system to prevent the EDG from being either to change the speed reference setting.
overloaded / motorized. It permits variations Another solid line for 3% droop shows the in engine speed (frequency) required due to setting for 50% load. This is what is done changes in the grid frequency.
when a unit is synchronized to the system in order to manage the loading of the unit.
To best explain how droop is used in the After synchronizing the unit and closing its system, refer to Figure 8-1. In this diagram, breaker, the operator must adjust the speed the right ordinate axis represents the grid reference input (through the motor operated frequency. The left ordinate is the reference potentiometer or other means) to have the speed input (the point to which the operator unit take on load or to decrease the load.
wants the unit to run). The abscissa is the percent loading and goes to 110% in as Once the unit is on the system and loaded much as most EDG units will have an to the desired load, the unit will not change
'overload' rating.
load unless the operator changes the speed reference input. However, if the system If the unit is running in isochronous, the frequency were to change by a small right and left ordinate values are the same amount, the load would also change by with the load line being flat and having no some small amount as shown by the two slope (parallel to the base of the graph). The lines close to, and parallel with, the 60 hertz operator sets the unit at the desired speed isochronous line.
and the unit operates at that speed for all loads (with only short durations of off speed Rev 3 /16 8-3 of 39 USNRC HRTD
Emergency Diesel Generator Diesel Engine Controls and Governing 8.1.3 Governor Classifications of a typical electric-hydraulic actuator is shown in Figure 8-4. The actuator is the 8.1.3.1 By Design and Construction interface between the electrical portion of the governing system and the engine Mechanical governors: In mechanical (mechanical portion). An example of this governors, the output or controlling force is scheme is shown in Figure 8-5.
created by centrifugal force acting on a set of rotating weights. Because the weight An electric control valve is connected to an assemblies are relatively small, the output armature in an electromagnetic field. An force is not sufficient to control the injection electric control box sends a signal to the field pumps on large engines. Mechanical which positions the armature and, therefore, governors are limited to use on small and the control valve to regulate the fuel automobile-type diesel engines. A simple delivery. When operating in the electric diagram for a mechanical governor is shown mode, the electric control overrides the in Figure 8-2. mechanical hydraulic control. In this way, the diesel engine operates in response to Mechanical-Hydraulic Governors: the demand on the emergency generator.
With mechanical-hydraulic governors, the Governor actuator and the electric governor rotating weight assemblies connect to a are explained in more detail later.
control valve rather than directly to the fuel control racks. The control valve directs 8.1.4 Principles of Operation hydraulic fluid to or away from a power piston. The power piston, in response to the The following three sections discuss the hydraulic fluid, controls the fuel racks and basic principles of governor operation.
therefore the engine power or speed. This provides greater force to move the fuel racks 8.1.4.1 Flyweight Assembly on medium and large size diesel engines.
See Figure 8-3. Virtually all governors are equipped with a rotating flyweight assembly, shown in Figure Electric-Hydraulic Governors: Electric- 8-2. Two or four individual flyweights are hydraulic governors normally utilized in mounted on the rotating ballhead, which is nuclear service have a governor actuator driven by the engine through a drive gear with two sections - a mechanical - hydraulic assembly. The speed of the ballhead is backup governor and an electric governor. directly proportional to the engine speed.
If the electric governor were to fail, it is possible to run the unit on the mechanical- As the ballhead rotates, centrifugal force hydraulic backup governor under manual acts on the flyweights forcing them outward.
control. In normal operation, the mechanical The amount of force exerted on the weights hydraulic backup governor is set at a speed is a direct function of the engine speed. The above the rated speed, and the electric higher the engine speed, the higher the governor is used to control the unit. The force exerted on the flyweights. The electric governor has control of both the load speeder spring is installed to counteract the and speed of the governor system. A view force of the flyweights.
Rev 3 /16 8-4 of 39 USNRC HRTD
Emergency Diesel Generator Diesel Engine Controls and Governing With mechanical governors, the flyweights At a constant speed and load, the control connect to a control sleeve which in turn valve is positioned to block the ports in the connects to the injector fuel control racks. valve sleeve, which creates a hydraulic lock With the engine operating at a constant to the underside of the power piston.
speed and load, the force on the flyweights is exactly balanced by the force of the An increase in load causes the engine to speeder spring. slow down. The flyweights move in when the levered force exerted by the flyweights If the load demand on the engine is falls below the force exerted by the speeder increased, the engine tends to slow down. spring. This action lowers the control valve As the engine slows, the force of the which directs the oil pressure supplied by speeder spring overcomes the force of the the gear pump through the sleeve to the flyweights and the control sleeve lowers. underside of the power piston. Upward That causes the fuel control racks to motion of the power piston moves the fuel increase fuel delivery and, therefore, the racks to increase fuel delivery and return the power developed by the engine. With the engine to its steady state rpm. As this increase in engine power, it returns to the happens, the control valve raises to again desired rpm, and the forces of the speeder take the neutral or blocking position.
spring and flyweights again balance.
The hydraulic governor acts as a If the load demand on the engine is reduced, mechanic / hydraulic amplifier. A small the engine speed tends to increase. The mechanical input can produce an output increased speed increases the force exerted force, created by hydraulic pressure, by the flyweights which now overcome the sufficient to control the fuel racks with a force of the speeder spring, raising the higher degree of sensitivity than is possible control sleeve. This control sleeve with a mechanical governor.
movement reduces fuel to the engine, causing it to return to its steady-state rpm. 8.1.4.3 Electric-Hydraulic Controls 8.1.4.2 Mechanical-Hydraulic Controls Within actuators used on EDGs with the EGA and 2301A governors, there is both a With the UG-8 mechanical-hydraulic mechanical-hydraulic governor and an governor, the fly-weights connect to a electrical-hydraulic governor control unit.
hydraulic control or spool type valve as shown in Figure 8-3. Hydraulic oil is 8.1.4.3.1 EGA Actuators (Figure 8-6A) supplied to the control valve by a small gear pump mounted in the base of the governor. Depending upon the size of the engine, the A power piston is hydraulically connected to EGA actuator will be either the EGB-10C the fuel control racks. A spring acts on the (used on the FME OP engines and ALCO power piston to oppose the hydraulic force. units), the EGB-35C, or the EGB-50C (used The bottom of the control valve sleeve is on the FME Pielstick engine units). The open to the oil sump in the bottom of the numerical value following the EGB signifies governor housing. the maximum work effort (in foot pounds)
Rev 3 /16 8-5 of 39 USNRC HRTD
Emergency Diesel Generator Diesel Engine Controls and Governing that the actuator can produce in moving the actuator to go to the mechanical hydraulic engine fuel controls. actuator higher speed setting until normal operator action is taken to reduce the speed In addition to the backup hydraulic governor setting to the desired control point. Only one with its control valve, the electric-hydraulic of the governor actuator sections may be in governors uses a second control valve control at one time; otherwise, governor connected to an armature magnet in a instability can result.
variable electro-magnetic field as shown in Figure 8-6A. A set of centering springs are 8.1.4.3.2 2301A Actuators (Figure 8-6B) used to center the armature in the field with the control valve in the blocking position. Depending upon the size of the engine, the 2301A actuator will be either the EGB-13P An electronic governor control box (EGA) (used on the FME OP engines and ALCO monitors the output of the generator for both units), the EGB-32P or the EGB-50P (used load and frequency. The control box on the FME Pielstick engine units). The 'P' generates a signal which is applied to the suffix indicates a proportional actuator field coil in the governor actuator housing. system.
An increase in load demand or decrease in speed causes the control box to generate a The actuators used with the 2301A signal which lowers the armature magnet governing system are proportional systems.
and control valve. Oil pressure is now That is, the governor output is proportional directed to the underside of the power to the electrical input from the 2301A piston, raising the power piston and control. On the EGA actuator, the output increasing the fuel delivery. The engine was only as required to close the actual returns to its steady state mode, and the speed to commanded speed loop.
control valve is returned to the blocking position. In addition to the backup hydraulic governor with its control valve, the electric-hydraulic With a decrease in load demand and/or governors use a second control valve increase in speed, the control box raises the connected to an armature magnet in a armature magnet and control valve. The oil variable electro-magnetic field as shown in under the power piston is now drained to the Figure 8-6B. However, in addition to the governor sump, and the spring pushes the centering springs is a lever system that power piston down. This reduces the fuel biases the transducer in proportion (in delivery and engine power to return the relation) to the position of the electrical engine to its steady state condition. portion power piston. This causes a feed back into the 2301A control such that it Actually, there is a small bias voltage put out knows about how much fuel is going into the by the control box when the control valve is engine for a given load and speed condition.
centered (in the blocking position). This is The output signal from the 2301A control to cause the electric governor section to go therefore becomes proportional to the load to the full fuel position in the event that the on the unit and the fuel requirement to electric control box fails. This causes the support that load or speed.
Rev 3 /16 8-6 of 39 USNRC HRTD
Emergency Diesel Generator Diesel Engine Controls and Governing Other than that difference, the remainder of The UG-8 governor is an independent, self-the 2301A actuator works essentially the contained unit. All settings, speed sensing, same as the EGA actuator, as described and control are in / on the actuator or the above. governor. The UG-8 is predominantly found on earlier EDG units supplied to the nuclear A failure of the electrical signal from the industry. Most of the later EDGs use the 2301A control causes the electric governor Electric Load Sensing governing systems.
section to go to the full output position. This The mechanical back-up governor is set at causes the actuator to go to the mechanical a slightly higher speed (frequency) than the hydraulic actuator higher speed setting until electric governor, so it does not engage in normal operator action is taken to reduce normal operation but is ready to assume the speed setting to the desired control control if the electric governor fails.
point.
Electric Speed and Load Sensing When Only one governor actuator section may be the electric governor is used, both speed in control at a time. Otherwise, governor sensing and load sensing are provided and instability can result. Therefore, governor controlled by either a separate EGA or a actuator settings must be coordinated. 2301A electric control box which provides input to the electric section of the governor 8.1.5 Nuclear Application Governors actuator. The control box senses the engine speed by either converting the generator Diesel engines used to supply Class 1E voltage signal to a voltage proportional to power to electrical loads at nuclear power the frequency or by means of a speed plants require reliable control to ensure their sensing magnetic pickup (MPU) mounted on proper operation under emergency the engine near the flywheel or other gear conditions. Governors specific to nuclear that operates in proportion to engine speed.
applications will be covered in detail below. Load is sensed by having both the current and voltage at the generator output 8.1.5.1 Types of Governors in Nuclear measured through current and potential Service transformers. A section within the control box converts these input signals to a voltage Mechanical-Hydraulic Governing - For proportional to the real load (KW) on the units equipped with only the mechanical- generator.
hydraulic governor such as the UG-8, the governor functions in response to a speed When the unit is operated in parallel with sensing flyweight assembly. Changes in the power grid, droop is introduced into the engine load / demand tend to cause a control box. Droop may be adjusted from 0 change in the engines operating speed (isochronous) to about 10% by means of the (RPM). The flyweight assembly, in "droop" potentiometer. When paralleled, response to changes in the engine speed, some droop must be present to provide for increases or decreases the fuel delivery to load sharing. When the unit is run alone, maintain the desired speed through the the droop function is normally switched off hydraulic servo system. (governor switched to isochronous).
Rev 3 /16 8-7 of 39 USNRC HRTD
Emergency Diesel Generator Diesel Engine Controls and Governing Electric Governor Backup The reverse acting actuator. That is, the signal mechanical-hydraulic governor actuator from the control to the actuator is inverse to provides backup for the electric governor. In the difference in the speed error detected by order that this mechanical backup governor the control box. The reason for this not interfere with the operation of the electric inversion is to cause the actuator to go to the governor, it is intentionally set to operate at mechanical backup governor should the a speed higher than the normal speed of the electrical signal from the control box unit. The lever system in the actuator forms disappear / fail.
a low pass OR gate such that the lowest speed input controls the unit. With the The actuator consists of two separate but mechanical backup governor set high, the interconnected governors: the mechanical electric governor then controls. Should the backup section and the electric transducer electric governor fail, the mechanical section. The mechanical-hydraulic governor backup governor will automatically take over section controls engine speed when the control, but at the higher speed setting. It is mechanical backup governor is in control necessary to manually adjust the backup (set higher than the electric governor).
governor to return to rated speed. When the electric governor is in control (set lower than the mechanical backup governor 8.2 Engine Governor Operation and receiving a signal from the electric control), the mechanical section goes to the There are several types and models of full output position so that the end of its governors used to control EDGs in nuclear floating lever becomes fixed.
plant applications. They all operate on the same basic principles. We will concentrate The actuator, mounted vertically to the our discussion on the Woodward series EG engine governor drive assembly, is driven Governor Actuator with either the EGA or directly from the engine gear train which the later model 2301A control box, as these allows it to sense engine speed. The are the most commonly used. actuator unit incorporates its own oil reservoir and pump which supplies the 8.2.1 Woodward EG Governor Actuator hydraulic pressure needed to operate the fuel control assemblies. Hydraulically, the The Woodward EG-B Governor Actuator, EGB actuators consists of three distinct but shown in Figure 8-6, is the mechanical interconnected sections:
portion of the electric governor system. The B in the designation indicates that the Mechanical Backup Section - A actuator includes the mechanical-hydraulic mechanical-hydraulic (flyweight type) backup section/function. A number governor functions to control the engine following the B indicates the work effort speed when the engine is operated at rating of the actuator in foot-pounds of speeds other than near rated speed or in the torque at stall. event the electric governor control has failed. NOTE: The mechanical Backup When the actuator is provided with the Section is the same for both the EGA system backup section, it is normally termed as a and the 2301A system.
Rev 3 /16 8-8 of 39 USNRC HRTD
Emergency Diesel Generator Diesel Engine Controls and Governing Electric Transducer Section - The second functions to position the terminal output governor is the actuator portion which works shaft of the actuator in response to changes in conjunction with the Electric Control Box in either of the first two sections.
(EGA or 2301A control). When the actuator is used with the Electric Control Box (EGA The hydraulic amplifier section, shown in or 2301A Control), the actual monitoring and Figure 8-5, consists of an oil sump, oil pump, governing takes place in the control box. accumulator assembly (pressure storage The electric control box is used to position and regulation), relay valve assembly, relay the electric pilot valve in that section. When piston and linkage to the terminal shaft.
there is no signal from the electric control, the electric power piston goes to its full The governor drive shaft causes rotation of output position, and its end of the floating the oil pump and the relay valve bushing.
lever becomes fixed. To insure this Rotation of the pump gears draws a suction happens upon failure of the EGA electric on the oil reservoir, and the oil is discharged control box signal, the center of the electric to the accumulator section.
pilot valve is intentionally offset. This causes the EGA control box to put out a The accumulator provides a reservoir of oil small signal in order to hold the electric pilot under pressure while also acting as a valve in the centered (blocked) position. pressure relief/regulating valve. Oil This EGA bias voltage is usually set at pressure from the pumps acts against the between 0.5 and 1.0 volts. The full swing of force of the accumulator springs. As the the EGA electric control box signal is from - pistons pass the bypass port, excess oil 6 to +6 volts. pressure is vented back to the sump.
Normal oil flow continues on to the top side For the 2301A system, the voltage to the of the relay servo piston and on to the relay actuator is inversely proportional to the fuel valve plunger and bushing. The relay servo required to regulate the engine speed, and piston connects to and controls the piston of there would normally be a voltage on the the terminal output shaft of the actuator.
transducer coil. If the 2301A control box fails, the voltage would go to zero (the full The relay valve plunger, which is controlled output condition) and the actuator would go by the loading piston, controls oil flow to the to the mechanical backup section control. underside of the relay servo valve. When the engine is operating in a steady state Hydraulic Amplifier Section - The third condition, the control land of the relay valve section is the hydraulic amplifier section plunger just blocks the port to the underside which provides the output force needed to of the relay servo piston. This creates a operate the fuel controls on the engine. hydraulic lock which prevent oil pressure, Again, the Hydraulic Amplifier Section is the acting against the top of the relay servo same for both the EGA system and the piston, from forcing the piston downward.
2301A system.
When there is a change in engine speed or The three sections described above are generator load, the loading piston will move connected through a loading piston which as a result of the action of the mechanical-Rev 3 /16 8-9 of 39 USNRC HRTD
Emergency Diesel Generator Diesel Engine Controls and Governing hydraulic or electric governor, depending on The control element of the electric governor which is in control. This movement of the section is the pilot valve plunger which is loading piston causes the relay valve attached to an armature magnet. A plunger to raise or lower. centering spring suspends the armature magnet and pilot valve in a transducer and When there is an increase in generator load magnet. The transducer and magnet is or a decrease in engine speed, the loading electrically connected to the EGA control piston will rise. This will, through the linkage box. A signal from the control box causes shown, cause the relay valve plunger to the armature magnet and pilot valve plunger drop, directing oil pressure to the underside to move up or down in response to changes of the relay servo piston. Since the bottom in the generator speed/load.
of the relay servo piston has a larger area than the top, the larger force of the oil acting With the unit operating at a steady state on the bottom of the piston will cause it to condition, a small signal is present in the move upward. This upward movement is transducer and magnet. As such, the pilot carried through the terminal shaft to the fuel valve and plunger are centered, blocking the control linkage causing the fuel delivery to port and creating a hydraulic lock below the the engine to increase. electric governor power piston. A change in the generator load or speed causes the During a decrease in generator load or signal to be change by the EGA control box, increase in engine speed, the loading piston which will move the pilot valve plunger up or is forced down, raising the relay valve down.
plunger and relieving oil pressure from the underside of the relay servo piston. The An increase in load or decrease in speed on reduced pressure on the underside of the the generator will result in a signal from the relay servo piston causes a net downward EGA control box causing the armature to force on the piston. The piston is forced move down. This motion allows oil to be down, reducing fuel delivery to the engine. directed to the underside of the electric power piston. The increased pressure on The relay beam, intermediate shaft, and the underside of the power piston will cause bearing transfer the movement of the relay it to rise, raising the loading piston. This servo piston back to the relay plunger valve. action, as discussed earlier, results in the This returns the relay plunger valve to the relay valve plunger directing oil to the blocking or steady state position. underside of the relay servo piston, which causes the terminal shaft to move the fuel 8.2.1.1 Electric Governor Section EGA control assemblies (racks) to the increased fuel position required to re-establish rated The electric governor section controls the speed.
position of the loading piston (as shown in Figure 8-6A) and ultimately the relay servo With a decrease in load or increase in speed piston and terminal output shaft by of the generator, the EGA control box will controlling the movement of the electric provide a signal to the transducer and governor power piston. magnet causing the pilot valve plunger to Rev 3 /16 8-10 of 39 USNRC HRTD
Emergency Diesel Generator Diesel Engine Controls and Governing move up. This upward motion of the pilot mechanical speed setting is below the valve plunger vents oil from the underside of electric control speed setting. When the the electric governor power piston. As the mechanical-hydraulic governor is in use, the electric governor power piston moves down, electric governor section is hydraulically it causes the loading piston to move down, locked with the electric governor power which raises the relay valve plunger. piston fully extended (fixed). The Upward movement of the relay valve mechanical-hydraulic governor setting is plunger vents oil from the underside of the normally slightly higher than the speed relay servo piston causing it to move down. setting used for the electric governor to This downward movement rotates the prevent the two sections from acting against terminal output shaft to the reduced fuel each other.
position required to re-establish rated speed. The pilot valve plunger of the mechanical-hydraulic governor is connected to the Operational stability is achieved by a flyweight assembly. This section also negative feedback to the compensating land includes a buffer system consisting of a of the pilot valve plunger through the buffer buffer piston, needle valve, and system. Oil from the governor oil pump is compensation land as was used with the directed to the top of the compensating land electric governor. The desired engine of the pilot valve plunger and to the left side speed (RPM) is established by setting the of the buffer piston. The right side of the force applied by the speeder spring which buffer piston is connected to the underside acts to oppose the motion of the flyweight of the compensating land of the pilot valve assembly.
plunger. This pressure creates sufficient force to move the pilot valve plunger up, With the engine operating at the desired returning it to the steady state blocking speed, the centrifugal force acting on the fly-condition. Movement of the power piston weights exactly balances the force applied ceases, and the engine accepts the by the speeder spring. This equilibrium increased load on the generator. The condition holds the pilot valve plunger in the sensitivity of the buffer system is determined blocking position, locking the mechanical by the setting of the needle valve, which governor power piston and the loading functions as an orifice between the two piston in the steady state condition.
sides of the buffer piston and compensating land. Should the mechanical load on the engine increase, the engine tends to slow down.
8.2.1.2 Mechanical-Hydraulic Governor This reduces the centrifugal force of the flyweights acting against the speeder spring Figure 8-6 shows the mechanical-hydraulic of the valve. The force of the speeder spring governor section, combined with the electric overcomes the centrifugal force and the pilot governor and the amplifier sections. The valve plunger lowers. Oil pressure is then mechanical-hydraulic governor section applied to the of the buffer piston moving it functions only when the electric governor to the right. This displaces the oil on the control box is not functioning or when the right of the buffer piston, applying its Rev 3 /16 8-11 of 39 USNRC HRTD
Emergency Diesel Generator Diesel Engine Controls and Governing pressure to the underside of the mechanical earlier, in Section 8.1.2.1, and refers to the governor power piston. The power piston difference in engine speed between no-load moves upward, repositioning the loading and full load operation. It is a key factor piston, thereby increasing the fuel delivery when operating two or more units in parallel to the engine. or when running connected to an infinite bus (electrical grid). In those situations, proper The pressure differential created is also use of the governor droop setting will help applied, via the needle valve, to the prevent unstable operation and / or possible compensating land of the pilot plunger. This damage to the engine o r generator. If this moves the pilot valve plunger upward. At very important concept is not yet clear to the same time, the upward movement of the you, review that earlier material and / or see mechanical governor power piston acts to your instructor. Proper use of the governor move the speed adjusting/speed droop droop setting is essential floating lever upward, reducing the force applied by the speeder spring on the Operationally, speed droop is a function of flyweight assembly. This allows the pilot the position of the mechanical-hydraulic valve plunger to return to the steady state power piston. Movement of the power blocking position. piston causes a proportional movement of the speed adjusting/ speed droop floating 8.2.1.3 Actuator Dial Settings lever which reduces the force on the speeder spring on the flyweight assembly.
The mechanical linkages, as shown on the Setting of the Speed Droop knob moves the left side of Figures 8-6A and 8-6B, are adjusting pin (fulcrum point) which changes connected to the three adjustment knobs on the lever ratio between the mechanical the face of the governor (see Figure 8-4). governor power piston and the speeder These adjustment knobs are to set specific spring.
operating parameters for the mechanical-hydraulic section of the governor. With the speed droop set at 0%, the full- load speed and the no-load speed would be the The "Speed Setting" knob is connected to same. This condition, called isochronous, is the speed adjust lever through a screw shaft satisfactory when the unit is powering its and clutch. This allows the operator to own isolated bus. A speed droop of about 3 manually set the desired no-load engine to 5% would be appropriate for units speed by adjusting the force of the speeder connected to the grid for surveillance or spring. In the nuclear application, this knob post-maintenance testing.
is normally set at the 'high speed stop' position. To ensure proper operation of the electric governor, the mechanical speed droop knob NOTE: The "Speed Droop" knob only should be set at Zero.
effects speed droop of the mechanical backup governor section of the Actuator. Also, the Load Limit knob should normally Electrical Droop is set in the Control Box. be set at the Max Fuel position.
"Speed Droop" was defined and discussed Rev 3 /16 8-12 of 39 USNRC HRTD
Emergency Diesel Generator Diesel Engine Controls and Governing 8.2.2 EGA Control Box sets the level of the load or speed at which the unit is to run. This is called the speed The EGA Box, as pictured in Figure 8-7, is reference.
the electrical part of an electro-mechanical servo system programmed to maintain a 8.2.2.2 Control Section preset engine speed and load sharing level in proportion to the capacity of the unit being The control section consists of a set of controlled. The EGA has three sections, as differential amplifiers and power amplifiers.
illustrated in in Figure 8-9 EGA Control An input signal is fed into these from the Block Diagram. summing junction.
8.2.2.1 Input Section The speed reference section supplies a regulated DC voltage to the speed setting The input section consists of a load sensor potentiometer (which is mounted outside the (watts transducer), a resistor box, a speed EGA Control Box). The output of this sensor, and a power supply section. During potentiometer is adjustable by the operator operation, the speed sensor receives a or by automatic control, and the output signal from one phase of the generator (proportional to the desired speed) is also output via potential transformers and put into the summing junction. The voltages converts it to a DC voltage proportional to from the speed setting potentiometer and the speed of the engine. This voltage is then the speed transducer (mentioned above) fed into the amplifier portion of the circuit at are the same value but they are of opposite the summing junction. This is called the polarity so that the resulting voltage at the speed transducer. summing junction is zero when the engine is at the desired speed.
The Load sensor receives voltage and current signals from each of the three The droop switch controls the load sensor phases of the generator output and uses output in both the droop and isochronous these signals to calculate the total electrical modes. In the isochronous mode, the output (KW) output of the generator. This of the load sensors is fed to the summing calculated total load is converted to a DC junction only if the unit is set up for voltage through a bridge of rectifiers and is isochronous load sharing with other units on fed into the summing junction if the system the same isolated bus. In the droop mode, is set up for droop or load sharing operation. however, the output of the load sensor is fed This section includes a potentiometer that to the droop control and then into the allows this watts transducer to be calibrated summing junction. The droop control is to the specific unit rating, etc. Another used to adjust the percent droop (1 to 10%)
potentiometer allows the amount of droop by applying a variable portion of the load desired to be set into the system if the unit sensor output to the summing junction.
is in the droop mode of operation.
The summing junction calculates the Another input is from a potentiometer or algebraic sum of the input signals from the another electrical / electronic device that load sensor, the speed sensor, and the Rev 3 /16 8-13 of 39 USNRC HRTD
Emergency Diesel Generator Diesel Engine Controls and Governing speed setting potentiometer. This summed 8.3 The 2301A Governing System signal becomes the input signal to the amplifier section. The 2301A Governing System is a more recent development. Several of the EGA Operational stability is achieved by systems have been replaced with the 2301A regulating the rate of change of the actuator system.
from one level to another during load or speed changes. This dampens out 8.3.1 2301A Actuator transients and oscillations in the control of the engine. The actuator used with the 2301A control system looks similar to the discontinued 8.2.2.3 EGA Output to Actuator EGA actuator on the outside. The actuator type number ends with the letter 'C' for The output of the EGA Control Box is fed to compensated and with the letter 'P' for the actuator. The magnitude and polarity of proportional actuator. The differences inside the signal determines the movement of the are not great. The mechanical-hydraulic armature and pilot valve plunger. section is identical as is the amplifier section. The only difference is in the electric During steady state conditions, the armature section. The 2301A compensated actuator is centered in the actuator electric does not have the buffer section and the transducer and magnet. With only the bias needle valve because the compensation is voltage applied to the coils, the pilot valve all done electronically in the control box. For plunger takes the neutral or blocking the proportional actuator, the transducer has position. a system of levers that feed the electric power piston position back to the transducer Under conditions of increasing load, the to bias it in a position between its centering output signal for the amplifier is applied to springs that are proportional to power the coils of the transducer and magnet. The output.
polarity of the signal causes the armature to move downward, increasing the fuel delivery On the actuators with backup sections, the to the engine. When the engine reaches the transducer and 2301A are set up for reverse desired operating conditions, the signal action operation. That is, the voltage to the ceases and the pilot valve plunger returns to actuator is low for increased fuel and higher the steady state position. for idle or no fuel.
With a decrease in load or increase in In all other respects and settings, actuators engine speed, the polarity of the signal is used with the 2301A actuator are identical reversed. The armature now moves with those used in the EGA box.
upward, allowing the oil pressure under the electric power piston to return to the sump. 8.3.2 2301A Control Box This lowers the loading piston, leading to a reduction in fuel delivery to the engine. The 2301A control box is shown in Figures 8-8 and 8-10. This control has the same Rev 3 /16 8-14 of 39 USNRC HRTD
Emergency Diesel Generator Diesel Engine Controls and Governing basic connections as the EGA control. It has 8.3.3 Speed Reference Input load sensor connections from the generator terminals through potential and current The speed reference (the speed at which transformers so the units KW load can be the operator wants the unit to run) can be measured. Its used primarily to set droop input from a number of sources. To make mode (the voltage connections are not used the system as flexible as possible, including for governor power or sensing unit speed). changing speed setting rapidly and Figure 8-10 shows the external connections automatically, the Digital Reference Unit to be made to the 2301A control box. (DRU) is preferred. Figure 8-14 shows the DRU unit and its inputs and connections are It is necessary to provide power to operate shown on Figure 8-15.
the governor, from either a DC supply at 20-40 volts, or an AC or DC supply providing The DRU allows one to set an idle speed, a 88-132VAC or 90-145VDC. For Nuclear maximum speed, and set point speed. The EDGs, the input voltage it typically 125VDC. set point speed would normally be the rated speed of the unit. The operator can also Like the EGA, there are terminals for the raise and lower the speed for manual control signal going to the actuator. There are also of the speed during engine maintenance or terminals for input of the speed reference for loading the unit once synchronized to the signal, either from a motor operated offsite power system.
potentiometer (like the EGA control) or from a Digital Reference Unit (DRU) or other The DRU has two possible ramp rates such voltage reference signal. that on one ramp rate, the rate of changing the speed can be slow so that operators feel Unlike the EGA, the 2301A requires a speed comfortable when making speed or load signal supplied from a Magnetic Pickup adjustments. By closing a contact, a fast (MPU). This pickup is usually mounted next ramp rate can be selected for use in getting to a gear (e.g., the flywheel / coupling ring) the unit up to rated speed rapidly in the that rotates in proportion to engine speed. event a start signal is received while the Figure 8-11 shows a typical MPU unit. This unit is at idle or some other intermediate is an assembly of a fine coil of wire wound speed condition. On units converted to over a permanent magnet, housed within a date, much flexibility is evident as systems magnetic material body. Metallic material have been developed to meet different (particularly if magnetic) moving by the tip of operation / plant desires for control.
the pickup will influence the magnetic field and cause the MPU to put out a pulse. This Some earlier 2301A applications used the signal is used to count gear teeth passing same Motor Operated Potentiometer (MOP) by, which is converted to engine RPM. the EGA system used, to provide a speed reference signal. With MOPs now obsolete Like the EGA, the 2301A can be used in and new spares unavailable, the DRU is a isochronous mode or in droop mode. In the viable replacement for them and can be case of the 2301A, only one switch contact applied to both EGA systems and those is necessary to control the operating mode. earlier model 2301A systems with MOPs.
Rev 3 /16 8-15 of 39 USNRC HRTD
Emergency Diesel Generator Diesel Engine Controls and Governing Figure 8-12 shows a typical 125VDC Motor
- Will respond to ESF signals to meet all Operated Potentiometer, with its internal technical specifications.
circuitry shown in Figure 8-13.
- Anticipates engine speed changes by sensing generator load, allowing the 8.4 Nuclear Plant Governors governor to adjust fuel more quickly than otherwise, thereby improving EDG 8.4.1 Advantages and Disadvantages of response to load changes.
Governor Models Now in Nuclear Service
- All governor control settings are in the EDG control box.
UG-8 Mechanical-Hydraulic Governor Advantages: EGA Electric-Hydraulic Governor
- Independent, self-contained, simple Disadvantages:
settings are on the face of the governor.
- Starting, governing are on mechanical
- MOP on the governor provides for backup governor until generator output control of speed from local and control voltage and current are available.
room panels.
- Part of the compensation is hydraulic
- Will respond for ESF to meet all technical within the actuator, subject to oil specification requirements for fast start, temperature and condition.
sequential and manual loading, steady
- Complexities of the electric and state operation at 60 Hz +/- 1.2 Hz, and mechanical actuators and the control engine shutdown. boxes are not easily understood by
- Proven reliability in both nuclear and operators and maintenance personnel.
commercial applications. In marine
- Set point drift problems.
service, engines run most of the time and
- Woodward has discontinued production UG-8 governors operate reliably for of this governor. The 2301A has been thousands of hours, until moving parts accepted as a qualified replacement begin to wear out. Analysis of governor governor.
oil for wear metals provides for rebuilding or replacement, well before failure. 2301A Electric-Hydraulic Governor Advantages:
UG-8 Mechanical-Hydraulic Governor
- Control at all conditions (not dependent Disadvantages:
on generator voltage)
- Early models provided only enough
- With a DRU, can automatically respond actuator power to operate fuel racks on to an emergency signal with the engine the smaller EDG engines in nuclear at standby, idle, .or running on the grid service including the EMD, OP, and for a surveillance test.
ALCO. Later models provided enough
- All of the compensation is electronic power (torque) to control larger engines.
(tuned for best performance)
EGA Electric-Hydraulic Governor
- Can control at idle or rated speed equally Advantages: well
- Powered from Generator Voltage
- Use of the DRU with the 2301A provides (No separate power supply needed) more operating flexibility and capability.
Rev 3 /16 8-16 of 39 USNRC HRTD
Emergency Diesel Generator Diesel Engine Controls and Governing 2301A Electric-Hydraulic Governor seconds) upon receipt of an ESF signal.
Disadvantages:
- Requires external power supply to 8.5 Other Possible Governor Systems operate (125VDC source typically used)
- Requires Magnetic Pickup (MPU) for In recent years, additional types of speed input governing systems have been developed.
- Complexities of the electric and Most involve digitizing the governor control mechanical actuators and the control algorithms used. One such governor boxes are not easily understood by system provided by Woodward Governor operators and maintenance personnel. Company would be the 2301D, a Digital version of the 2301A (an Analog system).
- The large number of component parts, mechanical / hydraulic interconnections Another is the 700 series, specifically the between the electric and mechanical 723PLUS. These governor packages have backup governors, and the sharing of a many, many features that, while ideal for common load output piston all contribute specific application requirements, are not to governor unreliability.
needed or appropriate for nuclear plants.
Most failures, on either system, result in Both the 2301D and the 723 series can be engine operation on the backup governor at provided with dual dynamics, allowing the a higher speed (often set to be 61.2 Hz).
same governor, by closure of switch / relay contacts, to operate a diesel fuel burning 8.4.2 Fast Start Problem unit, or a gaseous fueled or dual fuel unit equally well. Engines that run on gaseous In terms of engine wear and life, a ten-fuels (natural gas / propane) require a much second start is estimated to be equivalent to slower responding governor in that mode in 3550 hours0.0411 days <br />0.986 hours <br />0.00587 weeks <br />0.00135 months <br /> of engine operation at rated order to keep the air to fuel ratio under tight load. Fast starts ultimately reduce EDG life control. That is not applicable to straight and reliability. Fast stars with fast generator diesel engines in nuclear service.
loading stress both engine and generator.
Another problem with using these units in NRC Generic Letter 84-15 authorized plants nuclear service is that their power supplies to make slow starts. However, units with the are limited to 1840VDC, while most nuclear EGA governing system cannot make a slow plant station battery power systems are at start on the electric governor. It is necessary 125VDC. To apply these digital governors to use the mechanical back-up governor (on in nuclear plant service would require:
the actuator). In this state, the unit cannot respond to an ESF signal, so the EDG is
- A separate battery power supply, or
'inoperable' when on mechanical governor!
- A DC-to-DC converter power supply to produce 1840VDC from the 125VDC The 2301A governor, when applied with the station battery system. These introduce DRU, can be operated at idle speed under potential reliability issues and may have electronic governor control and CAN electrical noise. The latter can affect immediately go to rated speed (within 5 governor stability.
Rev 3 /16 8-17 of 39 USNRC HRTD
Emergency Diesel Generator Diesel Engine Controls and Governing A voltage divider circuit could be used with 8.6 Governor-Linkage Relationship the 125VDC system but that may not work well due to the wide operating range of the Regardless of the type of governor used, Station Battery system (90140VDC) plus there has to be a relationship between the the fact the governor load current can vary a governor output and the fuel injection lot. Simply taping the battery system would system components the fuel racks. This is not be appropriate, as that could result in normally provided by some sort of linkage very unequal charge condition (voltage) for consisting of levers and links. Most the battery cells connected to power the governors used in nuclear plant EDGs have digital governor system. a rotary output, referred to as a 'terminal shaft.' Some may have a linear output and For generator applications, the 723 series require a 'J' bar linkage system. Figure 8-16 comes in two parts the 723 unit to control shows the relationship normally set up the speed and the DSLC (Digital between a governor with a rotary output (45 Synchronizer and Load Control) unit for degrees of rotation typical of the EGB input of the generator parameters in order to actuator) and the engine fuel requirements.
have the system operating in the droop mode for surveillance testing. Or, the 723 Figure 8-16 shows that the linkage unit would need a GLC (Generator Loading relationship establishes certain key Control) in order to simulate a load control conditions to allow for engine operation signal. The combination of these units under a range of conditions, as follows:
requires much more space in the generator control panel than the 2301A or the 2301D. When the governor is at the minimum (no)
Therefore, its very likely that simple space fuel position, the engine must also be at the considerations would rule out retrofit of a 'no fuel' condition; otherwise, the governor 723 series digital governor in most existing may not be able to shut the engine down. In nuclear power plants. fact, the governor is usually set up such that there is a slightly negative fuel rack position Nuclear power plant governor applications when the governor is at minimum fuel just to are really quite simple: to provide good ensure that the governor can shut down the stability and the ability to respond rapidly to engine. Many governors contain a sudden and large load changes (such as shutdown solenoid that when operated, puts starting large pump motors) and to provide the governor terminal shaft at minimum fuel a means of controlling the loading on the unit in order to shut down the engine from a during monthly surveillance testing. The remote location.
2301A can operate just as well for these simple tasks as the more sophisticated The engine requires some fuel to operate digital units. The primary limitation for large when it is idling. The typical position is as load pickup is not the governor, which shown on the diagram. The engine also has always acts fast enough, but the engine to occasionally run at an overload.
itself. (Refer to the discussion at the end of Therefore, the linkage must ensure that the Chapter 10.) governor can move the fuel racks to at least that position plus some margin. The Rev 3 /16 8-18 of 39 USNRC HRTD
Emergency Diesel Generator Diesel Engine Controls and Governing full / rated load position is somewhat less During an overspeed condition, the than the overload position as shown. centrifugal force acting on the flyweight is Typically, the governor linkage is set up to sufficient to overcome the force of the use about 60 to 70% of the governor travel spring. This allows the flyweight to move in getting the engine from idle to full rated outward. The flyweight makes contact with fuel as shown. the trip pawl, unlatching it from the trip shaft.
The trip shaft, which is spring loaded, 8.7 Engine Overspeed Governor / Trip rotates as shown to activate the trip mechanisms, which by its spring force, Mechanically, diesel engines must operate returns all of the injectors to the no-fuel within a specific speed (RPM) range. In position. With no fuel going to the engine order to maintain the proper frequency, cylinders, the engine coasts to a stop. If the EDGs have a set RPM which is maintained engine is still loaded, it stops rapidly. With by the engine control governor. Should the this system, fuel to the engine is shutoff in governor fail to maintain the proper engine less than one engine revolution.
speed or should there be a failure in the fuel injection system which prevents control of Whether the engine overspeed trip device is the engine, the engine could increase in a separate governor or like the one in Figure speed to an unsafe level. 8-17, once tripped the engine cannot run until it has been reset manually. Of course, Such overspeed conditions, which could plant personnel must first determine the result in severe engine and / or generator cause of engine overspeed and take damage and hazards to nearby personnel, corrective action to prevent it from recurring.
are not uncommon with diesel engines. To prevent that from occurring, a redundant These devices are normally set to activate speed monitoring and overspeed trip device at 110 to 115% of the engines rated speed is required. It may be a separate governor and are active under all engine operating driven by the engine gear train, or (most conditions and modes. The also serve to often) an independent, mechanical trip protect the connected generator from being mechanism such as the simple device damaged. The NEMA 1 Standard to which shown in Figure 8-17. generators are qualified specifies they must withstand 125% of rated speed, thereby The overspeed trip illustrated is mounted providing an inherent safety factor with the directly to the end of the engine camshaft. engine limited to no more than 115%.
Since camshaft speed is either equal to or one half the engine crankshaft speed, this is Engine overspeed is one of two conditions an ideal location for such a device. The trip allowed (and required) to shut the engine shaft and trip pawl are mounted directly to down even if the unit is supplying power to the engine while the flyweight and spring emergency loads. Protective trips of various assembly rotate with the engine camshaft. types will be discussed in Chapter 10.
During engine operation at normal speeds the force of the spring is just sufficient to keep the flyweight clear of the trip pawl.
Rev 3 /16 8-19 of 39 USNRC HRTD
Emergency Diesel Generator Diesel Engine Controls and Governing Figure 8-1 Droop-Isochronous Relationship Rev 3 /16 8-20 of 39 USNRC HRTD
Emergency Diesel Generator Diesel Engine Controls and Governing Figure 8-2 Basic Mechanical Governor Rev 3 /16 8-21 of 39 USNRC HRTD
Emergency Diesel Generator Diesel Engine Controls and Governing Figure 8-3 Basic Governor with Hydraulic Power Piston Rev 3 /16 8-22 of 39 USNRC HRTD
Emergency Diesel Generator Diesel Engine Controls and Governing Figure 8-4 Electronic Governor Hydraulic Actuator Rev 3 /16 8-23 of 39 USNRC HRTD
Emergency Diesel Generator Diesel Engine Controls and Governing Figure 8-5 Governor Fuel Control Linkage Rev 3 /16 8-24 of 39 USNRC HRTD
Emergency Diesel Generator Diesel Engine Controls and Governing Figure 8-6A EGB-10C Actuator Schematic Rev 3 /16 8-25 of 39 USNRC HRTD
Emergency Diesel Generator Diesel Engine Controls and Governing Figure 8-6B EGB-13P Actuator Schematic Rev 3 /16 8-26 of 39 USNRC HRTD
Emergency Diesel Generator Diesel Engine Controls and Governing Figure 8-6A-B Major Differences Between EGB-10C and EGB-13P Actuators EGB-13P EGB-10C Rev 3 /16 8-27 of 39 USNRC HRTD
Emergency Diesel Generator Diesel Engine Controls and Governing Figure 8-7 EGA Governor Control Box Rev 3 /16 8-28 of 39 USNRC HRTD
Emergency Diesel Generator Diesel Engine Controls and Governing Figure 8-8 2310A Control Box Rev 3 /16 8-29 of 39 USNRC HRTD
Emergency Diesel Generator Diesel Engine Controls and Governing Figure 8-9 EGA Control Block Diagram Rev 3 /16 8-30 of 39 USNRC HRTD
Emergency Diesel Generator Diesel Engine Controls and Governing Figure 8-10 2301A Control Block Diagram Rev 3 /16 8-31 of 39 USNRC HRTD
Emergency Diesel Generator Diesel Engine Controls and Governing Figure 8-11 Typical Magnet Pickup Rev 3 /16 8-32 of 39 USNRC HRTD
Emergency Diesel Generator Diesel Engine Controls and Governing Figure 8-12 MOP for 125VDC Motor Rev 3 /16 8-33 of 39 USNRC HRTD
Emergency Diesel Generator Diesel Engine Controls and Governing Figure 8-13 Schematic of MOP Unit Rev 3 /16 8-34 of 39 USNRC HRTD
Emergency Diesel Generator Diesel Engine Controls and Governing Figure 8-14 Digital Reference Unit (DRU)
Rev 3 /16 8-35 of 39 USNRC HRTD
Emergency Diesel Generator Diesel Engine Controls and Governing Figure 8-15 DRU Connections Rev 3 /16 8-36 of 39 USNRC HRTD
Emergency Diesel Generator Diesel Engine Controls and Governing Figure 8-16 Relationship Between Governor Output & Fuel Control (Rack)
Rev 3 /16 8-37 of 39 USNRC HRTD
Emergency Diesel Generator Diesel Engine Controls and Governing Figure 8-17 Overspeed Trip (Governor) Mechanism Rev 3 /16 8-38 of 39 USNRC HRTD
Emergency Diesel Generator Diesel Engine Controls and Governing WALKAROUND SESSION 8 Using the electric / hydraulic governor and its components on the test floor, the instructor 8.0 DIESEL ENGINE CONTROLS AND will conduct the following training:
GOVERNING
- Illustrate the governor housing / case Purpose with its oil reservoir and pressurizing oil pumps.
The purpose of this session is to
- Illustrate the magnetic null balance complement Chapter 8.
control with its off-null output for control to the loading piston.
Learning Objectives
- Illustrate the loading piston with its Upon completion of this lesson you will be pressurized oil input port and power able to understand the following: output to the governor output shaft.
- Illustrate the EGA, 2301A, DRU
- 1. Basic Woodward mechanical / hydraulic control boxes with their adjustments governor for EDG units. and how they control the electric / hydraulic governor.
- 2. Basic Woodward electric / hydraulic governor with the mechanical / hydraulic
- Illustrate the mechanical / hydraulic governor as a backup governor or vice and electric / hydraulic governors in versa. the same case. Illustrate how either can control the governor output shaft
- 3. Governor-to-fuel-rack linkages. depending on the position of the floating lever connection between them and their differences in speed 8.1 The Mechanical/Hydraulic Governor settings.
Using the mechanical / hydraulic governor
- Illustrate the controls on the front of and its components on the test floor, the the governor case.
instructor will conduct the following training:
8.3 Governor Output Power Linkage
- Illustrate the rotating flyball governor operation and its output. Using an engine on the test floor with fuel-rack linkage, the instructor will conduct the
- Illustrate the power piston with its following training:
pressurized oil input port with opening amount controlled by the
- Illustrate the governor-to-fuel-rack flyball governor output.
linkage with its many angular joints
- Illustrate the power piston output with their potential for binding, and shaft through linkage to the governor the need for periodic testing and output shaft. lubrication.
8.2 The Electric/Hydraulic Governor Rev 3 /16 8-39 of 39 USNRC HRTD