U W U Flashcards
U W U
Who is our regional entity?
WECC
What AGC do? 3 things
- auto adjusts generation from a central location
- uses computer to maintain load/gen balance
- uses error signal called “area control error” to function
3 modes of AGC
- tie line
- flat frequency
- flat tie line
What does a fault recorder do?
Logs critical current and voltage at time of fault
On what principle does a transformer operate
Magnetic induction
Do both reactors and capacitors absorb vars?
NO
Capacitors add vars, reactors absorb
Which has higher resistance, copper or aluminum
Aluminum
Definition of charging current (write it out)
Current that flows due to alternate charge and discharge of the line due to alternating voltage,
regardless of whether the circuit is closed or open-ended
List 5 wecc areas
- northwest
- rocky mountain
- great basin
- southwest
- california
Define power factor
Pf= true power
—————–
apparent power
Do transformers make electricity
No
List 3 losses in a transformer
Hysteresis, eddy, copper I2R
What is an autotransformer
Single winding transformer that divides into 2 sections
What is an Instrument transformer
Steps down values to be read by meters
Power transformer
Transfers power w/voltages over 69kV
How do differential relays operate
Observes the incoming and outgoing currents and compares the differences
Does a bird landing on a wire cause a fault
No
4 transformer connection types, which types have phase shift and which don’t?
Delta-delta, wye-wye have no phase shift
Delta-wye or wye-delta have 30 degree phase shift
What do differential relays protect, list 3
- generators
- transformers
- bus sections
What happens to frequency if a system is overgenerating
Frequency increases
What is unit capability
Maz megawatts a generator can produce safely
What is response rate
Rate of load change a generating unit can achieve for normal operating purposes
What is heat rate
Amount of heat in BTUs required to produce 1 kwH of electrical output
What is efficiency
Measure of how much output is received for a given input
What is minimum load
Minimum amount of generation a generator can produce
Function of RAS (list 4)
- tripping selected generator units
- shedding load
- insetting capacitor or dynamic braking resistors
- tripping selected transmission lines
What is loop flow synonymous with
Parallel flow
What type of equipment os included in BES (List 4)
- individual generation resources over 20 mVA, or plant greater than 75mVA connected via a step up transformer to facilities operated 100kV or higher
- lines operated at 100kV+
- transformers w/ 100kv+ (primary and secondary)
- associated equipment that could automatically trip a BES facility
Solve for an unknown using Ohms law
Remember E = I x R
What part of a generator is stationary
Stator
Solve for an unknown using transformer turns ratios
Remember voltage proportional to turns
Difference between switchyard and substation
Switchyard doesn’t have transformers
Do capacitors increase or decrease indictive reactance
Decrease
List 4 sources of reactive power
- shunt capacitor
- overexcited generators
- line capacitance
- synchronous condensors
Operating principles
Which one measures distance from relay to location of fault
(Impedance)
Distance relays
Operating principles
At each terminal; trips their associated circuit breaker unless a blocking signal is received
Directional comparison relay
Operating principles
When relays at one end detect a fault, the pilot channel is turned on to signal to the other end that a fault has occured
Transfer trip
Operating principle
Uses overcurrent fault detecting relays to compare the relative phase angles
Phase comparison
