Contingency Analysis and Reliability
Four parallel lines are loaded as indicated below. Line C has an OTDF of 0.3 for the loss of line D. A 50 MWB 200 MWC 200 MWD 200 MWIf line D trips what will the loading be on line C?
260 MW
No IROL can have an IROL TV that exceeds __________?
30 minutes
The Reliability Coordinator shall initiate control actions or emergency procedures to relieve an IROL exceedance without delay and within which time limit?
30 minutes
Unless it's an emergency, Transmission Operators should not remove Bulk Electric System facilities from service until which of the following actions is completed?
A Real-time assessment of the transmission facility outage is completed
What is a Transmission Loading Relief?
A process identified by each interconnection to relieve loading on the transmission system caused by power transfers across areas
Operational Planning Analysis such as next day studies are performed by the Reliability Coordinator for its Reliability Coordinator Area. Next-day reliability studies ensure that the bulk power system can be operated reliably under which conditions?
Anticipated and potential conditions
How often is a Reliability Coordinator required to perform a Real-time Assessment of its Reliability Coordinator Area?
At least once every 30 minutes
Reliability Coordinators and Transmission Operators are required to perform Real-time Assessments to ensure their system is being operated in an N-1 reliable state. How often must they perform a Real-time Assessment?
At least once every 30 minutes
A 500 kV tie-line between two Transmission Operators also crosses the boundary between two Reliability Coordinators. The substation at one end of the line is just within Reliability Coordinator A's area, while the other end is well within Reliability Coordinator B's area. This line often has voltage problems due to heavy unscheduled flow. Which of the following statements is most correct?
Both reliability coordinators should have operating procedures, processes, or plans to address voltage control issues on the line
Balancing Authority ABC has a transaction to receive 200 MW flowing from Balancing Authority XY. The Reliability Coordinator for XY has ordered a Transmission Loading Relief procedure that would reduce the scheduled Interchange to 100 MW. What should Balancing Authority ABC do?
Comply with request
After a disturbance on the system, a Balancing Authority Area experiences a tie-line loading up. What action should the Balancing Authority take?
Contact their reliability coordinator and discuss mitigation options
What tool relies on the State Estimator?
Contingency Analysis
Each Reliability Coordinator shall have adequate analysis tools to monitor the Bulk Electric system, such as wide area overview displays, state estimation, and which other capabilities?
Contingency analysis capabilities
A Balancing Authority is meeting their Balancing Authority Area's load demand with generation operated within their Balancing Authority Area. They have enough Operating Reserves for the most severe single contingency. Interchange transactions are being curtailed for schedules Sourcing and Sinking outside of their Balancing Authority area through the Transmission Loading Relief Procedures. What is this Balancing Authority response to the TLR issued?
Curtail Interchange as requested and no further action is needed
If an Operational Planning Analysis or a Real-time assessment indicates a potential emergency, what is the system operator's first action?
Develop an operating plan to mitigate the emergency
Reliability Analysis studies conducted by Reliability Coordinators should include planned outages. If a previously planned outage causes an issue for a neighboring Reliability Coordinator. What should the RC do?
Discuss with impacted RC and postpone outage
What is utilized in calculating the distribution of Interchange Transactions and determining curtailment of Interchange to relieve transmission loading?
Distribution Factors
Power flow studies conducted by a Reliability Coordinator identifies a planned and approved outage scheduled for later today will possibly cause a SOL violation. What action should the Reliability Coordinator take?
Do not allow the outage to proceed
In which order would the following actions most likely be considered by a Reliability Coordinator to help maintain transmission loading within acceptable limits?
Generation re-dispatch Reconfiguration of the transmission system Curtail Interchange Transactions Load Shed
Transmission overloads are often due to unscheduled flow. Balancing Authority areas are buying and selling energy to meet load demand economically. Which is the most accurate description of this market activity?
Generation sourcing from other areas are traveling to the demand (sink) through the path of least resistance
Reliability Coordinator A anticipates an overload of a high voltage transmission line that interconnects with Reliability Coordinator B's region. Reliability Coordinator A has a procedure on file that calls for Reliability Coordinator A to reduce Interchange Transactions to relieve the issue if it cannot be resolved within 15 minutes. What should Reliability Coordinator A do?
Immediately contact Reliability Coordinator B to discuss options
Reliability Coordinator A has determined there is a problem in his area which requires action by Reliability Coordinator B. Both A and B have agreed upon the problem and solution. What should the Reliability Coordinators do next?
Implement the agreed upon solution and notify the involved Reliability Coordinators
A transmission line trip results in a SOL exceedance and the Transmission Operator implements the Operating Plan for the SOL. What should the Transmission Operator do next?
Inform the reliability coordinator of actions taken
A Transmission Operator performs a Real-time Assessment that identifies a SOL exceedance. What should the Transmission Operator do next?
Initiate its operating plan to mitigate the SOL exceedance
A transmission system must be operated so that which of the following will not occur as a result of a single contingency?
Instability, uncontrolled separation, or cascading outages
A contingency results in the exceedance of an IROL. What could be the result if the IROL is allowed to be exceeded longer than its Tv?
Interruption of power to a large part of the BES
A disturbance on the system has resulted in the exceedance of an IROL with a Tv of 30 minutes. After 15 minutes, re-dispatch and reconfiguration options have been implemented but the IROL violation has not cleared. Which of the following actions from the Reliability Coordinator would be appropriate?
Issue a directive to shed load to return to within the IROL limit
An Operating Procedure has been written to mitigate potential System Operating Limit violation on Sunflower 500 kV line. Real-time contingency analysis indicates that Sunflower line will exceed its SOL if the Seed line trips. Which of the below is the most appropriate next step for a Reliability Coordinator of Sunflower 500 kV line?
Issuing an operating instruction per the operating procedure
A Generator Operator receives an Operating Instruction from its Transmission Operator to bring on additional generation to mitigate a low voltage situation. The Generator Operator must comply with the Operating Instruction unless:
It results in safety concerns or environmental violations
Following a contingency or other event resulting in an Interconnection Reliability Operating Limit (IROL) violation, the Transmission Operator shall return to within the IROL as soon as possible, but no longer than ______.
Its IROL TV
If a portion of a Reliability Coordinator Area is experiencing low voltage, which is an Operating Instruction the Reliability Coordinator may issue in this situation?
Lower transfers across area and increase generation in area with low voltage
Which of the following are tasks of the Reliability Coordinator for its Reliability Coordinator Area?
Monitor system facilities it its RC area and determine any SOL or IROL violations
It is a hot summer day which results in higher than expected loads. Reliability Coordinator A performs a Real-time assessment that shows a potential SOL violation based on contingency. The study determines actions are required by a Transmission Operator in Reliability Coordinator B's area. The Reliability Coordinators communicate, and actions are taken by the appropriate Transmission Operator. Reliability Coordinator A determines the potential SOL condition is resolved/mitigated. What must Reliability Coordinator A do next?
Notify Reliability Coordinator B and any impacted Transmission Operators or Balancing Authorities in Reliability Coordinator A's area that the SOL has been resolved
It is a hot summer day which results in higher than expected loads. Reliability Coordinator A performs a Real-time assessment that shows a potential SOL violation based on a contingency. The study determines actions are required by Transmission Operator in RC Area A and in RC Area B. What should the Reliability Coordinator do?
Notify Reliability Coordinator B and the Transmission Operator in Reliability Coordinator A's area to discuss actions to take
A Transmission Operator has scheduled a short, temporary outage of the SCADA system for a software update at 22:00 tonight. Which of the following actions is required of the Transmission Operator?
Notify the Reliability Coordinator and known impacted entities of the outage
Studies show there will be an overloaded line on the transmission system in Reliability Coordinator A's area. Reliability Coordinator A has determined that the solution is for Reliability Coordinator B to open a low voltage transmission line in his area. Although Reliability Coordinator B shows that opening the low voltage line will not cause any other issues, he states that his preferred solution is for Reliability Coordinator A to remove the 345 kV transmission line from service. What is the best solution?
Open the low voltage transmission line If the involved RCs cannot agree on the solution, the more conservative solution shall be implemented
Reliability Coordinator X and Reliability Coordinator Y are connected by two 500 kV transmission lines. Studies indicate that loss of one of the lines will result in an IROL.. Reliability Coordinator X determines the Tv as 30 minutes and Reliability Coordinator Y determines it to be 20 minutes. What should the Reliability Coordinators do?
Operate to the 20 minute time limit
A high voltage tie-line between Reliability Coordinators would exceed its limit in a contingent condition as indicated by the analysis of one of the Reliability Coordinators. The other Reliability Coordinator does not have that alarm indication due to a difference in derived operating limits. How should this discrepancy be handled between the two Reliability Coordinators?
Operate to the most limiting parameter
A Transmission Operator notified the Generator Operator to change the MW output of their hydro plant to relieve an overloaded transmission line. That is an example of which of the following?
Operating Instruction
Which of the following is an evaluation of projected system conditions to assess anticipated (pre-Contingency) and potential (post-Contingency) conditions for next-day operations, sometimes called a next-day study.
Operational Planning Analysis
What is Power Transfer Distribution Factor?
Percentage change of electrical loading on a line due to a change in power transfers from one area to another
What is Outage Transfer Distribution Factor?
Percentage change of electrical power transfer when a facility is removed from service
What is generation shift factor?
Percentage change of loading on transmission due to generator output changes
If the power flow on the transmission system exceeds acceptable limits, which corrective action(s) can the Reliability Coordinator instruct a Balancing Authority to take?
Re-dispatch generation, reduce interchange, or shed load
An operational analysis indicates a line will overload if another line becomes de-energized. When developing the Operating Plan which actions should a system operator consider?
Re-dispatch, reconfigure, reduce
What is an Operating Instruction?
Real-time Operating personnel command to change or preserve the state of an element of the BES
System operators are responsible for actual and expected system conditions. This responsibility is accomplished by performing which of the following?
Real-time assessments Real-time contingency analysis Communication with reliability coordinator
Which of the following actions would a Transmission Operator be expected to take, or direct others to take, to mitigate SOL and IROL violations?
Reduce Interchange, change the output of generators, and shed load
The Reliability Coordinator receives a real-time contingency analysis (RTCA) alarm indicating a potential overload on a high voltage tie-line. The Reliability Coordinators will communicate and coordinate mitigating actions. Which actions are likely to be taken?
Reducing Interchange Transactions
Which entity initiates an Interconnection-wide Transmission Loading Procedure or authorizes a transmission relief process.
Reliability Coordinator
Reliability Coordinator A receives a TLR request issued by Reliability Coordinator B in the Eastern Interconnection due to serious congestion in Reliability Coordinator B's area. Which of the following actions would be acceptable?
Reliability Coordinator A informs Reliability Coordinator B that complying would cause a reliability issue
Which functional entity provides a big picture view of the power system and acts to address reliability in its area via direct action or by issuing commands?
Reliability coordinator
To ensure reliability of the system and prevent a SOL exceedance, a generator is set to quickly and automatically reduce its output upon receiving indication of a transmission line trip. This would be an example of which of the following?
Remedial Action Scheme (RAS)
A Reliability Coordinator performs an Operational Planning Analysis for the next day, and studies indicate a scheduled outage will cause an SOL violation. What is the best course of action for the system operator?
Reschedule the outage for a later date
Transmission Operators, Balancing Authorities, Generator Operators, Distribution Providers, shall comply with Reliability Coordinator Operating Instructions unless such actions would violate which of the following?
Safety, equipment, regulatory requirements
Which of the following is one thing a Balancing Authority must monitor to maintain balance within its area and support Interconnection frequency?
Status of remedial action schemes that impact generator or load
Which of the following must a Transmission Operator monitor to determine SOL exceedances within its area?
Status, voltage, and flow data outside its TOP area identified as necessary Non-BES facilities within its TOP area identified as necessary BES facilities within its TOP area Status of Remedial Action Schemes it its TOP area
The Transmission Operator experiences an unexpected line outage which results in the subsequent loading of a parallel line at 101% of its SOL, what action should the Transmission Operator take?
Take the appropriate action to return the system to within normal limits Inform the reliability coordinator
Why is it necessary to report SOL and IROL exceedances to the Reliability Coordinator?
The reliability coordinator will then evaluate actions being taken and direct additional corrective actions as needed
When another Transmission Operator requests emergency actions to be implemented in your area, what is the expectation?
The requesting TOP has also implemented emergency actions
Which are the three types of limits to consider when determining system limits?
Thermal Angle Stability Voltage
Curtailing an Interchange Transaction that crosses an Interconnection boundary can be accomplished through this process:
Transmission Loading Relief (TLR)
What is a contingency?
Unexpected failure of a system component
A Transmission Operator conducts a study that shows the power flow limit for Line Bravo is 450 MVA. The Reliability Coordinator's study shows that the line's limit is 480 MVA. What should the Transmission Operator do?
Use the transmission operator's limit and conduct another study
Maintenance personnel inform you that insulator maintenance must be performed on a 230 kV line and the line must be deenergized to perform the maintenance. In the past, outages of this line on high load days have resulted in a SOL violation on your system. Whom must be informed of this outage?
Your reliability coordinator and any transmission operators or balancing authorities that may be impacted by the outage
