The rules and procedures that govern how equipment is isolated
-used at all integrated generating stations
How are PSSP/WPP boundaries identified
On the station one line diagram with a dotted line
in the Joint Local Operating Order
Who holds O/A for PSSP equipment at generating stations
BCH FVO T&D Control Centre
Who holds O/A for WPP equipment at generating stations
Generation staff at site
What is the procedure for establishing work protection for equipment located on the WPP side of the WPP/PSSP boundary
The PO assigns O/R UTAI the appropriate one-line perimeter isolating device to a WPP Cat D worker
The WPP worker then performs his Isolation and LockOut
What are 2 methods of isolation for work on equipment in WPP area that requires isolation in PSSP area
GOI Procedures
-the FVO PIC can issue a GOI
-the isolating device is located in a distant remote location
Transfer of O/A Procedures
-The isolating device is located in the same station/switchyard(PSSP side)
What are 2 methods of isolation for work on equipment in PSSP area that requires isolation in WPP area
PSSP Procedures
-The WPP PIC can issue a GOI
-the isolating device is located in switchyard(WPP side), but PSSP work site is in a distant remote location
WPP Procedures
-transfer of O/A to a WPP Cat D worker
-isolating device is located in switchyard(PSSP side), but PSSP work site is in distant remote location
What Operating Order defines O/A and O/R of NPRF facilities
1J-11
Who retains O/A of station service at generating stations
The Generation Region
Who retains O/R on the WPP side at generating stations
T&D FVO Control Centre (PO)
What is procedure for assigning O/R of station service facilities
PO assigns O/R UTAI appropriate one-line perimeter device to a WPP Cat D worker
What is purpose of protection
To remove a fault before it takes down the entire system
It is able to detect the fault and clear it through fault clearing devices (CBs)
What is difference between a protection system and a protection scheme
Protection System is each individual protective arrangement
Protection Scheme is the whole co-ordinated combination of each individual protection arrangement
What is Selectivity(pertaining to protective relaying)
Only a minimum portion of the power system should be disconnected to isolate a fault
What is Security(pertaining to protective relaying)
Schemes must be able to discrimminate between signals which require action, and those that do not
What is Reliability(pertaining to protective relaying)
Ability to operate without failure whenever a fault or abnormal condition exists
What is Coordination(pertaining to protective relaying)
Schemes must relate to each other so they operate in the right order
What are 2 types of redundant protection?Why
Primary Protection and Standby Protection(backup)
-increased dependability
-one protection may be removed for maintenance and the equipment reamain protected
What happens to current and voltage in a fault condition
Current will rise
Voltage will fall
What are two reasons for utilizing instrument transformers
Provides useable quantities of voltage and current for:
metering and control
protective relays
What is a VT
Voltage Transformer: provides low value of voltage proportional to system voltage(120v)
What is a CT
Current Transformer: provides low value of current proportional to system current(5 A)
With respect to a CT, what is burden
The amount of load connected to the secondary of the CT (ohmic value)
How does exceeding burden impact a CT
Could saturate the CT, no longer accurately reflect system current
Can VT secondaries be opened when they are energized
Yes. But the concern is what relays use this information and what impact that would have on the system
Can CT secondaries be opened when they are energized
No. Dangerous voltages could occur damaging equipment and/or workers
What is a Protection Zone
The section of power system that a particular protection covers
defined by the system they protect
boundaries determined by the location of CTs
What is a Tripping Zone
The section of power system that is tripped by protection
boundaries determined by the CB locations
What is overlap(pertaining to protection)
Protection zones are typically 'overlapped' to prevent the possibility of unprotected areas
What is breaker fail protection
A generator zone protection senses a generator fault and initiates protection operation. If the CB fails to open, 'Breaker Fail' protection operates to trip the adjacent zone
Breaker fail monitors for fault current flow through the CB that failed to open
What is purpose of relay targets
Provide a record of the relay's operation
Electromechanical relay targets = 'flag' drops down
Digital relays = LED lights indicate operation
What are symmetrical components
Used for analysis of 3 phase electrical power systems using vectors for the three phase quantities
What is meant by Positive Sequence
Generators produce positive sequence voltage and current
Currents and voltages have a positive phase rotation
Each phase is equal in magnitude
Under balanced conditions only positive sequence exists
What is meant by Negative Sequence
May exist in addition to positive sequence if conditions become unbalanced due to unbalanced loads or a fault
Unbalanced currents and voltages between phases result in Negative Sequence (negative phase rotation)
What is meant by Zero Sequence
When conditions are unbalanced and there is a path to ground, positive, negative, and Zero Sequence quantities will exist
For zero sequence, phase quantities are equal in magnitude and in phase
What 2 relays are used to detect stator phase to ground faults
Zero Sequence Overvoltage Relay
Third Harmonic Voltage Differential Relay
What relay is used to detect stator phase to phase faults
Differential Relays(87)
How is a generator protected from overspeed
The governor will respond to limit overspeed
Overspeed Tripping Relay(12) will operate if the governor fails
How is a generator protected from motoring
Reverse Power Relay(32) protects the unit(detects power flow INTO the generator)
This Relay is blocked when the unit is in Sync/Cond
What electrical protective relays are in place on a generating step-up transformer
Differential protection(87):
Current Differential
Ground Differential
What non-electrical protective relays are in place on a generating step-up transformer
Gas Relays(63)
Sudden Pressure Relays(63)
Conservator low oil device
Oil Temperature
Winding Temperature
Pressure Releif devices
Why is it important to detect a field ground on a synchronous generator? Which relay
A loss of symmetrical magnetic flux will result(shaft vibration and overheating of windings)
2 field grounds will cause a short circuit unbalance on field windings
Ground Detector relay(64)
What is meant by 'loss of field'? Which relay
A loss of excitation
Leads to a decrease in terminal voltage, loss of field strength, loss of electrical synchronization
A generator with loss of excitation will draw MVARs (motoring)
Field Relay(40)
Describe importance of detecting 'loss of field'
What helps protect against this
Prevents generator from losing synchronism to system and tripping off
Magnetic field around field windings becomes too weak from under-excitation to maintain electrical synchronization
Possibly lead to pole slip
Resultant loss of MW could lead to system breakup and major outage