MA/MB/NA - Main Generation to 13.8kV Flashcards
Purpose and Operation of the main generation, excitation/regulation, and non-class 13.8 kV
What is the purpose of the Main Generation system?
-Converts mechanical energy into electrical energy.
-House loads through the Aux transformer
-To the grid from the Unit transformers
What are the main components of the Main Generation system?
Main Generator, Isolated Phase (isophase ducts), Main Transformer Bank, Aux Transformer
Describe the generator
turbine driven, four pole, synchronous, alternating current generator
What are the major components for the main generator?
Generator Casing, Stator, Rotor, and the Collector
What are the end shields?
They are on both ends of the generator and contain the bearings (journal) that hold up the rotor and are split horizontally proving a path for seal flow
What components are a part of the generator casing?
Stator Frame, End shields, Excitation dome, and Lower frame extension
What makes up the components of the excitation dome?
Generator Hydrogen Distribution tubes and the hydrogen coolers
What is the purpose pf the Lower Frame Extension?
has the mounts for the High Voltage Bushings to the isophase Buses
What is the purpose of the stator?
It generates the voltage ( 24kV) that is supplied to the Main, Auxiliary, and Power Potential Transformers
Describe the Stator
-The stator is a winding of insulated copper bars that form a ring.
-It interacts with the rotating magnetic field from the rotor windings and supplies voltage to the High voltage Bushings
How is the stator cooled?
The stator bars are hollow to allow deionized water to flow through them from inlet and outlet headers/hoses
What is the purpose of the rotor?
Produces the required magnetic flux to interact with the Armature (stator) windings to make voltage & current
What are the major components of the rotor?
Field Windings, Retaining rings, slip ring Bearing journal (drive end & collector end), and the rotor field winding cooling fans
What is the purpose of the collector?
It applies the DC voltage to the rotor field windings to induce the magnetic field
How does the collector operate?
It applies the DC voltage through its carbon brushes to the rotor’s slip rings
How is the collector housing cooled?
A cooler fan that Normal Chilled Water (WC) flows through
What is the purpose of the isolated phase bus?
Conducts power from the main generator to the Main & Auxiliary Transformers
How do the isophase buses operate?
They are isolated from each other & the environment. It is an aluminum conductor supported by porcelain insulators within a dust/water tight enclosure
How are the Isophase ducts cooled?
Cooled by forced air from the Isophase Bus Duct Cooling system (CE)
What provides cooling for the Isophase Bus Duct Cooling system (CE)?
Turbine Cooling
What is the purpose of the Main Transformers?
Steps up the 24kV from the main generator to the grid @ 525kV
How is the main generator isolated?
The primary windings are directly connected to the Main Gen.
Secondary windings: 2 output breakers “8” & “5”, a motor operated disconnect
Explain the difference between disconnects and breakers
Disconnects are only for isolation
Breakers can be used for isolation but also have protection features
High Voltage Bushings
Connect the secondary windings of the Main Transformers to the SRP switchyard
Neutral Bushing
Connects the transformer to ground to minimize fault currents
Low Voltage Bushing
Connects the 24kV output from the generator to the primary winding of the Main Transformer
Bushing Potential Device
Steals a small amount of 60 Hz 115 Volt power through the Condenser Bushing to power transformer auxiliary equipment
(heaters)
Electronic Temperature Monitor (ETM)
Each Main Transformer has one to monitor winding temperature & Top Oil Temperature.
Also controls the operation of the transformer’s cooling banks
How do you read the Electronic Temperature Monitor (ETM)?
The display scrolls through channels every 2 sec. for the values.
red LED indicated a set value has been exceeded
What are the set points for the phases of cooling for the main transformers?
When the transformer get power “flash-the-field”
Between 70-75 degrees Celsius temp
Over 75 degrees Celsius Winding temp
For the Main Transformers, when does each group of fans and pumps turn on?
First group turns on at “flash-the-field” / when it first gets power
winding temp 70-75 Celsius the second group turns on
Over 75 Celsius 3rd group turns on
Constant Oil Pressure System (COPS)
-Tank mounted to the top of the transformer which allows for the volume changes due to temperature with the oil.
-Desiccant breather and vents air
How does the conservator tank work?
It acts as a surge tank for the oil within the transformer, while keeping the oil isolated from atmosphere
- Tank level is measured by a float, positioned below the bladder, that is attached to a gauge near the tank
- There is a pressure gauge which shouldn’t move under normal conditions
-The desiccant keep air going into the bladder moisture free
Describe the purpose and function of the Mechanical Pressure Relief Device.
- A spring loaded valve that will actuate to relieve excess pressure that may build inside the transformer.
- Actuates and raises the mechanical flag. Sends an alarm to the CR and will reseat
Describe the purpose and function of the Sudden Fault Pressure Monitor.
- Monitors for any pressure surges due to internal faults. Has 3 channels
- Power status light, fast pressure light, and reset switch (one per channel)
- Reset switch and Alarm Kill switch ( panel common)
- one channel will cause an alarm in the CR
- two of three channels will trip that transformer’s isolation breakers
Describe the purpose and function of the Gas Accumulation Detector.
- Will detect accumulations of gas within the oil of the transformer from oil deterioration or oil hot spot heating
- Normal value is zero
-Will alarm the Control Room
Describe the purpose and function of the Serveron Gas Analyzer.
- not connected to any other system only indication is local & is monitored through a remote website. needs helium gas cylinder
- Green light for power
- Blue light is for service, needs to be checked on the site
- Red, Alarm. Let CR know and check site
Describe the purpose and function of the Control Cabinet.
- Norm & Alt power supplies. Lights will indicated what supplies are available ABT
- Contains switches to control cooling banks and heaters
- An Alarm panel
- Main & Startup Transformers gets its supply from 480VAC Load Centers
-Site Power & Unit Aux gets theirs from 480 VAC MCC - Overload devices
Describe the purpose and function of the transformer Alarm Panel.
- All transformer alarm panels get their supply power from Non-class 125 VDC Control Power NK
- lamps for 12 different alarms
- CR gets a generic alarm panel alarm, AO needed to verify cause
-Startup Alarm panel testing will alarm ALL 3 Control Room - Testing switches in the units send no alarm to CR
Describe the purpose of the main generator output breakers.
-2 breakers that provide protection trips for faults on the main generator or the grid
- Ability too sync, connect, or disconnect each unit’s generator to/from the grid
- to sync closed “8” to parallel to grid then close “5”
Describe the purpose of the motor operated disconnects.
- Will isolate main gen, transformers from the grid for maintenance
Describe the setpoints for cooling for the unit Aux Transformer
-Top oil < 60C & Windings <70C, “All natural” no pumps or fans
- Oil 60-65 C & Winding 70-75 C All 14 fans stagger start no pumps
- Oil >65 C & Winding >75 C All pumps
Describe the Main Generations (MA) on plant start up.
- Pressurize gen with Hydrogen, start stator cooling (CE), turbine up to speed, & apply excitation
- Field is flashed, Main & Aux Trans get power and systems start cooling them
- Close “8” increase load to 65 Mw then close “5”
- Following plant stabilization, main Gen. load is increased & 13.8 kV loads are switch from offsite to Aux Transformer
Describe a Load Rejection
- Sudden Loss of load on the Main Generator
- Partial: load drops but Generator stays online
- Total: Rejection that causes Gen. to trip
What might happen in the case of a load rejection?
Some automatic plant functions include:
- Reactor Power cutback (RPCB) in which certain CEDM groups will drop, reducing power to ~60%
- Steam Bypass Control System (SBCS) by pass the turbine and allowing for steaming to continue to cool the core
What would cause a a Fast-Bus Transfer?
- Main Generator Trips
- Aux Transformer Trip
- Main Transformer Trip
NAN-S01/2 should switch to off-site power to maintain power to RCPs
Describe the purpose of non-class 480 LC (NG) to support the MA system
Describe the purpose of Non-class 480 MCC (NH) to support the MA system
Describe the purpose of non-class 125 VDC control Power (NK) to support the MA system
Describe the purpose of non-class 120 VAC instrument power (NN) to support the MA system
Describe the purpose of Uninterruptable Power (NQ) to support the MA system
Describe the purpose of Normal Lighting (QA) in supporting the MA system
Describe the impact of losing non-class 120VDC Control Power (NK) to MA
What is the impact to MA if MB is lost?
Main generator trips
What is the impact to MA if Stator Cooling (CE) is lost?
Main Generator Trip after 70 sec delay
What is the purpose of the of Main Generator Excitation and Regulation (MB) system?
-supplies the DC current to the rotor for its magnetic field
- Monitors generator output voltage/current & regulated the DC current to the rotor
What are the main components of the MB system?
-power potential transformers
-Power Conversion room
-EX2100e Control system
-MARK Vle BoP Control System
-HVAC & Fire protection
Describe Power Potential Transformer (PPT) cooling
ALL NATURAL
- all passive cooling, ambient air cools the radiator fins
Describe the PPT functions
Taps off between the generator and the Aux Transformer.
-24kV to 1050kV to the AC cabinet
Describe purpose and operation of the EX2100e Control System
provides DC voltage and current to maintain the rotor’s magnetic field
Describe the EX2100e 2 modes of operations
Automatic: voltage sensed & the regulator automatically controls the DC Field current to maintain the Generator output voltage
Manual: set to a specific DC field voltage. Will stay constant no matter what the generator output voltage is
Describe the Rectifiers
- there are 4 rectifiers. 3 are needed to be in-service, 1 for standby or maintenance
Convert AC to DC
Describe the cooling for the cabinets
All cabinets have 2 cooling fans. one in use and one in standby.
- If one is lost the other will automatically start
-if both fans are lost for a rectifier, that power bridge will shutdown and the one on standby will assume the load
Where does power for cooling in the power room come from?
- The 2 supplies are non-class 480 VAC LCs and power is routed to a transformer and distribution panel within the PCR. ABT
What makes up fire protection for MB?
VESDA Fire Detection Systems
&
STAT-X Fire Suppression system
How does the VESDA Fire detection system work?
will alert CR board 6, trouble alarm, HMI alarm viewer, and a alarm on the Plant Fire Protection System in the SSR
- Indv detectors and air sampling piping in the overhead of each room
How does the STAT-X Fire Suppression System work?
self-contained canisters in each room.
-system does NOT auto disperse
- extinguishing agent MUST be manually activated by AO or Fire Dept by the stair cases for the emergency exits
What is the purpose of the non-class 13.8 kV (NA) system?
takes 525kV off-site power and steps down to 13.8 kv to distribute to WRF, to the class 4,16kV buses
Main Generator 24kV to 13.8kV to supply power to the “house loads”
What are the major components of the NA system?
3 Start up Transformers
AE-NAN-X01/X02/X03
13.8kV Switchgears
NAN-S01-S07
Site Power Transformer and switchgear
AE-ZYN-X05 & AE-ZYN-S08
What is Unit 1 Specific for the NA system?
Supplies power to WRF, TSC, & 480 VAC Load Centers in the Switchyard
What is Station Blackout Configuration?
SBOG > NAN-S07 to a unit’s NAN-S03
- This will have power going up to NAN-S05
-Use the FBT path to power NAN-S01
-Go through the ESF transformer powering one class bus
What is the purpose of the start-up transformers?
Step down off-site 525kV to 13.8 kV for use by the NA system
Describe the SRP (upstream) isolations for the startup transformers.
-525kV Motor operated Disconnect Switch, operated at the SRP Control Room verified by AO & SRO
vert to horiz disconnect
- Two 525kV breakers, normally operated by SRP operators. “5” / “8”
-In an emergency an AO may operate supervised by a CRS,SRO, or SM
Describe the PVGS Startup Switchyard (downstream) isloations.
-13.8 kV breakers located at each NAN-S05/6
- Manually operated disconnect switches @ the Transformers (turn & raise)
Describe the bushings for the Start-up Transformers
- 3 High Voltage bushings connected to the primary winding
- low voltage bushings connect the secondary windings to the low voltage lines
Describe the Windings for the Start-up Transformers
-One Primary winding (H) where all 3 high V phases comes in
- Two 13.8 kV Secondary Windings (Y & Z)
- One 13.8 kV tertiary winding that dampens harmonics & reduces the severity of ground faults
What is the downstream output of the start-up transformers?
Each Start-up transformer has TWO 3-phase 13.8 kV outputs
Describe the setpoints and cooling for the startup transformers.
Winding <70 C All Natty pumps/fans secured
winding 70-75 C 1 fan bank & 1 pump starts
Winding >75 C 2nd fan bank & 2nd pump starts
POWERED FROM SY 480 LC NGNL43 & NGNL44
What is different with the alarm panel @ the startup transformer vs the PA transformers?
The Alarm panel on the startup transformers will alarm ALL 3 CRS when the switch is put into the ‘TEST’ position
What is and what are the consequences of an Open Phase Condition?
-When one or two phases of three become disconnected
-*****
What could cause an Open Phase Condition (OPC)?
-Breaker Poles failing to open or close
- Failing Transformer bushings
-Line insulators breaking
- Improperly connected conductors
What equipment is used for Open Phase Protection?
What is the purpose of the 13.8 kV non-class Switchgear?
-buses NAN-S01-S07
- distributes power to non-safety loads, non-class 4.16 kV (NB), and WRF
What is the difference between NAN-S01-S06 and NAN-S07?
NAN-S07: only operated locally
-their handswitch flag MATCHES the position of the breaker
- SBOG output breakers are operated from SBOG Control Panels
- the tie breakers to each unit are located on S07
NAN-S01-6: Normally operated from the Control Room
- Can be operated in the event of an emergency
-Handswitch flags indicate the last position the handswitch was taken to during TESTING.
What is a 86 lockout indicated by?
- An orange flag on the 86 lockout handswitch
-86 lockout Handswitch turned 45 degrees - breaker’s whitelight is out
- green light is brighter than normal
What is the breaker labelled ‘DA’ for inside the breaker panel?
Opening the ‘DA’ breaker will remove control power from the entire circuit, and all indicating lights will go out
What are each of the following fuses for:
UC / UT / UA / UL
-UC ‘Closing’ supplies the power to the closing circuit and the green/clear lights
-UT ‘Tripping’ power to the tripping circuit Red/White lights
-UA ‘Remote’ or ‘UX’ connects breakers control circuit to the CR and supplies power to the CR breakers indicating lights
-UL ‘lifting’ power to the connector for the breaker for the racking motor
What must happen in order for a Fast-bus Transfer to occur on NAN-S01 & NAN-S02?
- Either of the initiating events for a FBT:
-Trip the Main Gen. or Unit Aux T.
-Switch in the CR must be in ‘AUTO’
-neither NA bus can have an 86 lockout - sync check
-crosstie breaker closes before the breaker between the bus and transformer opens
