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NERC Study Guide > Transmission > Flashcards

Transmission Flashcards

1
Q

What kind of Switchyard Scheme

A

Breaker & Half

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2
Q

What kind of Switchyard Scheme?

A

Double Bus, Single Breaker

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3
Q

What kind of Switchyard Scheme?

A

Double Bus, Double Breaker

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4
Q

What kind of Switchyard Scheme?

A

Double Bus, Double Breaker

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5
Q

What kind of Switchyard Scheme?

A

Main & Transfer

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6
Q

What kind of Switchyard Scheme?

A

Ring

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7
Q

What device has the IEEE device number of 21?

A

Distance Relay

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8
Q

What device has the IEEE Device number of 27?

A

Under Voltage Relay

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9
Q

What device has IEEE device number of 52?

A

AC Circuit Breaker

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10
Q

What device has the IEEE device number 50?

A

Instantaneous Over Current Relay

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11
Q

What device has the IEEE device number of 51?

A

AC Inverse Time Over Current Relay

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12
Q

What device has the IEEE device number 87

A

Differential Relay

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13
Q

What is a major reason for identifying the transfer capabilities of the transmission system?

  • Mitigate transmission constraints in real-time
  • Proactively avoid system problems
  • Identify all bottled generators
  • Maximize income of the company
A

Proactively avoid system problems

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14
Q

Automatic load shedding schemes should consider all of the following except?

  • Power flow levels
  • Rate of voltage decay
  • Voltage
  • Generator MW output
A

Generator MW Output

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15
Q

Your system planning group has determined that the Total Transfer Capability is 475 MW, but the posted Available Transfer Capability is 425 MW. If current transmission reservations total 375, how much capacity is available for reserving?

A

50 MW - must hold to posted limit

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16
Q

What does TLR stand for?

A

Transmission Loading Relief
-Multi-step procedure that guides action of Reliability Entities when taking steps to manage transmission system congestion

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17
Q

What would be the expected impact on a line’s operating capacity for the next day if the current temperature is 83F and the forecasted temperature is 98F?

  • Capacity would increase
  • Capacity would double
  • Capacity would not change
  • Capacity would decrease
A

Capacity would not change

18
Q

If a transmission operator has to remove a transmission facility from service, which of the following do they have to provide notification to?

  • All TOPs in interconnection
  • Distribution providers
  • All PSEs w/transmission service
  • Potentially affected TOPs
A

Potentially affected TOPS

19
Q

IROL stands for?

A

Interconnection Reliability Operating Limit
-If violated could lead to instability, uncontrolled separation , or Cascading outages that adversely could impact reliability of BES

20
Q

SOL stands for?

A

System Operating Limit

-Value such as MW, MVAr, Amperes, Frequency or Volts

21
Q

When utilizing psuedo-tie, time varying component is added to what portion of BA’s tie-line bias ACE equation?

  • Actual Interchange component
  • Scheduled interchange component
  • Actual Frequency component
  • Scheduled frequency component
A
  • Actual Interchange component
22
Q

Which of the following substation bus arrangements often initially designed to be later expanded to breaker & a half arrangement?

  • Main & Transfer
  • Ring
  • Double-bus-double-breaker
  • Single-bus
A

Ring

23
Q

System voltage has dropped below nominal. You decide to place a capacitor bank on service. What do you expect?
A. The capacitor bank’s output will be greater than nominal due to needs of the system.
B. This is a bad decision as the capacitor bank will cause voltage to drop further.
C. The capacitor bank’s output will be less than nominal due to system conditions.
D. This is a bad decision as the capacitor bank will not provide the necessary MVARs.

A

C. The capacitor bank’s output will be less than nominal due to system conditions.

24
Q

Why are SVCs often placed near windfarms?
A. To compensate for the variable MW output of the windfarm.
B. To absorb the excess reactive power produced by the windfarm.
C. To compensate for the sub-synchronous resonation produced by the windfarm.
D. To provide dynamic reactive power the wind turbines cannot provide.

A

D. To provide dynamic reactive power the wind turbines cannot provide.

25
Q

A given hydropower generator is in synchronous condenser mode, therefore…
A. It can provide dynamic reactive power but cannot ramp to provide MWs.
B. It cannot provide reactive power, but can ramp to provide MWs.
C. It can provide dynamic reactive power, and could also ramp to provide MWs.
D. It essentially acts like a reactor or capacitor bank.

A

C. It can provide dynamic reactive power, and could also ramp to provide MWs.
In synchronous condenser mode, a hydro unit is synchronously connected to the grid, and it’s AVR is able to provide reactive power, but it isn’t generating any MW. However, it is in a position to ramp to provide MWs (usually if frequency drops below a given value). Remember, hydro units generally ramp very quickly.

26
Q

A large industrial park is drawing a large amount of MVARs over long, high voltage transmission lines causing the lines to approach their MVA limit. Assuming all of the following options are available, what course of action could the system operator take?
A. Place a capacitor bank on service close to the industrial park.
B. Place a reactor bank on service close to the industrial park.
C. Increase the transmission lines MVA ratings.
D. Place a capacitor bank on service close to the generators serving the load.

A

A. Place a capacitor bank on service close to the industrial park.
This will free up the MVARS crossing the long transmission lines. Remember, MVARs don’t like flowing long distances!

27
Q 
Which of the following would be the largest value in magnitude for a given transmission path?
A.	Available Transfer Capacity
B.	Transmission Reliability Margin
C.	Capacity Benefit Margin
D.	Total Transfer Capability
A

D. Total Transfer Capability

ATC = TTC – Transmission commitments – CBM – Transmission Reliability Margin

28
Q

What is a concern with higher than nominal voltage with an open ended line?
A. Excessive MW flows
B. Phase-to-Phase faults and/or damage to equipment.
C. Line overheating and/or sagging conductors
D. Over-voltage is not a major concern.

A

B. Phase-to-Phase faults and/or damage to equipment.

29
Q

What are dynamic ratings?
A. Line ratings which can change in real-time based on system condition—including temperature.
B. Line ratings which can change based on economics.
C. Line ratings which as set day-ahead by engineers.
D. Line ratings which are only used in emergencies.

A

A. Line ratings which can change in real-time based on system condition—including temperature.

30
Q

The capacity benefit margin is best explained as ____.
A. The amount of transmission capacity set aside for energy sales.
B. The amount of transmission capacity left after current transmission commitments.
C. The amount of transmission capacity set aside for LSE use in emergency situations for generation.
D. The total amount of transmission capacity of a transmission path.

A

C. The amount of transmission capacity set aside for LSE use in emergency situations for generation.

31
Q 
Power systems that have very long transmission lines with generation located far away from load centers are most likely to have \_\_\_\_\_\_\_\_ be the limiting factor.
A.	Thermal Limits
B.	Voltage Limits
C.	Phase Angle Limits
D.	Contingency Reserve Limitations
A

C. Phase Angle Limits
Having generation far away from load, and transmission branching far out to accomplish this is more likely to cause larger phase angles. The farther the branch, the “weaker” the busses will be and the more the phase angle will lag the generator’s angle.

32
Q

Angle instability is caused by
A. A loss of magnetic bonds
B. Overheating of transmission lines
C. Generator field current being overexcited
D. A shortage of dynamic reactive capability

A

A. A loss of magnetic bonds

33
Q

Which of the following is not usually associated with a potential voltage collapse scenario?
A. Large phase angles
B. Low reactive power reserves
C. High MVAR flows
D. The Most Severe Sigle Contingency just occurred

A

D. The Most Severe Sigle Contingency just occurred

34
Q

When would it be acceptable to remove transmission lines from service for voltage control?
A. After studies indicate N-1 security is met
B. Removing transmission lines from service for voltage is forbidden by NERC standards except for real-time thermal overloads.
C. If the lines are not considered EHV
D. Only if no energy sales are scheduled across the line.

A

When would it be acceptable to remove transmission lines from service for voltage control?
A. After studies indicate N-1 security is met
B. Removing transmission lines from service for voltage is forbidden by NERC standards except for real-time thermal overloads.
C. If the lines are not considered EHV
D. Only if no energy sales are scheduled across the line.

35
Q 
A given SOL has an angle stability limit of 400MVA, a thermal limit f 450MVA, and a voltage limit of 475MVA.  What must the operator operate to?
A.	475MVA
B.	400MVA               
C.	450MVA
D.	425MVA
A

B. 400MVA the most limiting

36
Q 
The transfer capability that is usable for further commercial activity over and above already committed uses is called \_\_\_\_\_\_\_\_.
A.	Total Transfer Capability
B.	Capacity Benefit Margin
C.	Available transfer capability
D.	Commercial Transfer Capacity
A

C. Available transfer capability

37
Q 
The amount of firm transmission transfer capability preserved by the transmission provider for LSEs, whose loads are located on that TSP’s system, to enable access by the LSEs to generation from interconnected systems to meet generation reliability requirements refers to \_\_\_\_\_\_\_\_.
A.	Total Transfer Capability
B.	Capacity Benefit Margin
C.	Available transfer capability
D.	Commercial Transfer Capacity
A

B. Capacity Benefit Margin

38
Q 
A given TTC is 800 mw.  The CBM is 100 mw.  Existing transmission commitments are 200 mw.  The Transmission Reliability Margin is 50 mw.  What is the ATC?
A.	550 mw
B.	450 mw
C.	350 mw
D.	700 mw
A

B. 450 mw

39
Q 
A given tie line has a phase angle difference of 25 degrees between the sending end and the receiving end.  If load is increased at the receiving end, what will be the effect on the phase angle?
A.	Increase
B.	Decrease
C.	Stay the same
D.	No way to know
A

A. Increase
Remember the power flow equation (don’t worry about memorizing it) But do understand that the angle difference is what drives power flow on a line. So if you increase load on the receiving end, obviously more power will flow across it. That means the angle is increasing.

40
Q

True/False: UFLS and UVLS are IROLs if utilized?

A

TRUE

NERC Study Guide (6 decks)

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