Transmission Test Bank
What is a thermal rating? Maximum amount of current before overheating damage occurs Maximum load that can be transformed Heat Source Transmission line sagging capability
Maximum amount of current before overheating damage occurs.
During a system emergency, the System Operator can direct other Transmission Operators and Balancing Authorities to violate which limit? None. Equipment parameters should be maintained within their established limits Available Transfer Capacity Interconnection Reliability Operating Limit System Operating Limit
None. Equipment parameters should be maintained within their established limits. Throughout the NERC Standards requirements state that System Operating Limits must be respected. To ensure a reliable power system, established limits can not be violated.
What is used for the instantaneous protection of system equipment? Operators Relays Schemes SCADA Alarms
Relays.
Preparations are being made to tie two islands together during restoration. Island "A" has a frequency of 58.95 Hz and Island "B" has a frequency of 59.97 Hz. What action should be taken to synchronize the two islands? Increase generation in Island "B". Shed load in Island "B" Disable the Synch Check Relay. Shed load in Island "A".
Shed load in Island "A". EPRI 2009 Power System Dynamics Tutorial, Section 11.6.
The maximum and minimum voltage, current, frequency, real and reactive power flows on individual equipment under steady state, short-circuit and transient conditions, as permitted by the equipment owner is ____________. Equipment Rating The System Operating Limit The point of collapse Always changing.
Equipment Rating. NERC Glossary: Equipment Rating - The maximum and minimum voltage, current, frequency, real and reactive power flows on individual equipment under steady state, short-circuit and transient conditions, as permitted or assigned by the equipment owner. This is not necessarily the System Operating Limit. System Operating Limits are based upon certain operating criteria. These include, but are not limited to: • Facility Ratings (Applicable pre- and post-Contingency equipment or facility ratings) • Transient Stability Ratings (Applicable pre- and post-Contingency Stability Limits) • Voltage Stability Ratings (Applicable pre- and post-Contingency Voltage Stability) • System Voltage Limits (Applicable pre- and post-Contingency Voltage Limits)
When coordinating under frequency load shedding and under frequency generator tripping the _____________________________. generators should trip after the UFLS breakers should open at the same time as the UFLS load should not be shed during the process generators should trip before the UFLS
Generators should trip after the UFLS. EOP-011, Emergency Operations - The Transmission Operator and the Balancing Authority shall have Operating Plans with provisions for operator-controlled manual Load shedding that minimizes implemented in a timeframe adequate for mitigating the Emergency. Under frequency load shedding, or UFLS, is designed to drop load to match generation. Under frequency generator relays are designed to protect generators from operating at low frequencies for an extended period of time. These generator relays should be set to trip to protect the generators if UFLS is unable to return the frequency to an acceptable value within a set period of time. The first trip of under frequency generator relays should be AFTER the last trip of UFLS relays.
A generator is connected to the bulk electric system through three transmission lines (A, B & C) all rated at 340 MVA. Line A is loaded to 300 MVA, Line B is loaded at 200 MVA and Line C is loaded at 100 MVA. Following the loss of Line C, 40% of the flow will shift to Line A. Field personnel request an emergency outage on Line C for repair. Which of the following is the best course of action? Grant the outage request and redispatch generation as necessary. Grant the outage request. Deny the outage request. Delay the request until system conditions are more favorable.
Grant the outage request and redispatch generation as necessary. Field personnel have requested an emergency outage on Line C so the request should be granted if possible. System Operators must always be prepared to respond to unscheduled changes in system configuration, therefore the operator would be expected to grant the emergency outage and change system configuration and generation dispatch as necessary to accommodate the outage.
Which of the following actions is used to prevent voltage collapse when reactive resources are insufficient? Lower transmission voltage regulator settings. Offset scheduled frequency. Implement load reduction. Reduce generator output.
Implement load reduction. NERC Standard VAR-001 states, "Each Transmission Operator shall operate or direct the operation of capacitive and inductive reactive resources within its area; including, reactive generation scheduling; transmission line and reactive resource switching and; if necessary, load shedding - to maintain system and interconnection voltages within established limits." Of the options specified in the standard, "implement load reduction" is the only one listed as one of the choices in this question.
If a Transmission Operator or Balancing Authority is unable to restore Real and/or Reactive Power Balance, they must request emergency assistance from the Reliability Coordinator. If operating reserves are not available, corrective action need to include: Implement manual load shedding. Reduce voltage on the distribution system. Notify the RRO. Reduce interchange between systems
Implement manual load shedding. Implementing manual load shed is included as part of an Operating Plan to mitigate operating emergencies, such as, low voltage due to insufficient reactive resources, or imbalance due to real power resources deficiency.
You are a Reliability Coordinator experiencing a flow gate that has become overloaded because a parallel 345 kV line has relayed out causing an SOL violation and possible IROL violation. What would you do to relieve this violation? Order the line be placed back in service within 30 minutes. Notify the affected Reliability Coordinator and ask them to resolve this issue Implement the appropriate transmission loading relief procedures Issue a warning to the Transmission Operators that lost the 345 kV line.
Implement the appropriate transmission loading relief procedures. Megawatts flow on the path of lowest impedance. When the 345 kV line relayed out, the path of lowest impedance is the flow gate that has now become in violation of an SOL and IROL. The Reliability Coordinator has the authority to relieve any transmission facility that is an actual or potential reliability concern. One of the options available is to use transmission loading relief procedures which curtails interchange that contribute to the line overload.
If you remove a parallel transmission line from service to relieve an IROL or SOL violation, what will happen to the loading on the remaining transmission facilities? Voltage will increase on these lines Increase Decrease Probably stay the same
Increase. Transmission application: If you remove a parallel transmission line from service for any reason, the loading on the remaining transmission facilities will increase. The load/demand for electricity will cause the power to flow from source to sink through multiple paths. Equipment outage will cause power flow to shift to other transmission lines.
A Transmission line is overloaded by 25% above its SOL. A parallel line is out for routine maintenance and can be placed in service in 10 minutes. What is the first step the Operator should take to reduce the line loading? Initiate the restoration of the parallel line. Open the line. Shed load at the downstream bus. Re-Dispatch Generation.
Initiate the restoration of the parallel line. Contacting the field crew to re-energize the line is the first step to relieve the overload condition.
When an area of the transmission system separates from the remainder of the Interconnection, this is referred to as ________________. Brownout Blackout islanding instability
Islanding. EPRI 4.8.1: Islanding refers to the complete separation of areas of the system from the remainder of the interconnected system. Unmitigated SOL or IROL violations may lead to system instability, voltage collapse, and cascading outages and result in system separations.
A Transmission Operator is implementing their system restoration plan after a major system disturbance. When they are ready to energize a blacked out area, the system operator must _________________. Increase blackstart generator to maximum output Turn all voltage regulators to the manual position Close any capacitor banks which are open Isolate the load
Isolate the load. EPRI 2009 Power System Dynamics Tutorial, Chapter 11.
The Transmission Operator must inform which entity when an SOL has been exceeded and the actions being taken to return the system to within limits? Its Balancing Authority Neighboring Transmission Operators Its Reliability Coordinator Its Supervisor
Its Reliability Coordinator. Each Transmission Operator shall inform its Reliability Coordinator of actions taken to return the System to within limits when an IROL or SOL has been exceeded (NERC Standard TOP-001). The Transmission Operator and the Reliability Coordinator work closely together to resolve transmission loading issues.
Which of the following is NOT a correct action a Transmission Operator would consider when reactive resources are limited? When conditions get critical, consider reducing MEGAWATT transfers to limit reactive power losses. To prevent a loss of synchronism type of voltage collapse, maintain system transfer limits to safe limits. Ensure that sufficient dynamic and static Megavar sources are available. Keep voltage schedules as low as the schedules will allow.
Keep voltage schedules as low as the schedules will allow. When reactive resources are limited, to prevent voltage collapse, the System Operator should maintain system transfer limits to safe limits to reduce the power angle increase following a disturbance. Keep voltage schedules as high as the schedules will allow. The higher the voltage the lower the power angles necessary to transmit a given amount of power. When conditions get critical, consider reducing MW transfers to limit reactive power losses. Ensure that sufficient dynamic and static MVAR sources are available.
Which of the following best describes the Load/Frequency Relationship? Load magnitude is independent of the system frequency. Only non-motor loads are affected by a change in system frequency. Load magnitude varies with system frequency. As frequency increases, load decreases.
Load magnitude varies with system frequency. As a rule of thumb, a 1% drop in frequency will result in a 2% drop in load. - EPRI Power System Tutorial
System Restoration plans should establish the transmission system backbone using the highest voltage line available because of the ________ impedance of the ____________voltage lines. power flow; reactive capacitance; higher lower; higher higher: lower
Lower; higher. Higher voltage lines will have lower impedance and higher capacity. They should be used for initial system restoration and to re-synchronize the system if possible. - NERC Standard EOP-005
Two lines of the same construction are both connected to Bus A and are both open at the other end. Line #2 is twice as long as Line #1. The voltage at the open end of Line #1 is 3% higher than the voltage at Bus A. What can you conclude about the voltage at the open end of Line #2? More than 3% higher than Bus A. More than 3% lower than Bus A. 3% higher than Bus A. 3% lower than Bus A.
More than 3% higher than Bus A. Voltage at the open end of a transmission line will increase due to an effect called Ferranti Rise. If two lines have the same construction but different lengths, the longer line will produce a higher voltage at the open end compared to the shorter line. The Ferranti rise effect is a long term overvoltage condition that is associated with high voltage lines that have their receiving ends open. Overvoltages greater than 10% above nominal can easily occur. The magnitude of the overvoltage depends on the length of the open-ended line and the strength of the system tied to the closed-end of the line. EPRI 5.3.2.
The Transmission Operator that you work for is installing new relays on some of their major transmission tie lines using newer technology. Who should your company notify before the work is begun? The Reliability Coordinator only. Adjacent transmission operators NERC Operating Committee. Neighboring Transmission Operators, Balancing Authorities, and Generator Operators.
Neighboring Transmission Operators, Balancing Authorities, and Generator Operators. NERC Standard PRC-001 R4: Each Transmission Operator shall coordinate protection systems on major transmission lines and interconnections with neighboring Generator Operators, Transmission Operators, and Balancing Authorities. - NERC Standard PRC-001
Your system is on the verge of a voltage collapse and all reactive resources are at maximum output. You have determined that shedding firm load will alleviate the problem. Before shedding the load, with whom must you confirm the action? The Reliability Coordinator Other affected Transmission Operators No one The Load Serving Entity
No one. TOP-001 Transmission Operations Each Transmission Operator shall act to maintain the reliability of its Transmission Operator Area via its own actions or by issuing Operating Instructions. Although no longer explicitly stated in TOP-001, the System Operator does have the authority to shed load to maintain reliability and because of the dynamic nature of power flow, there may not be time to consult about load shed to mitigate an emergency.
A Balancing Authority is experiencing a potential capacity or energy emergency and communicates its current and expected future system conditions to its Reliability Coordinator. What would likely be the Reliability Coordinator's first action? Notify the deficient BA marketers Notify all Reliability Coordinators Order Load Shed Notify other Balancing Authorities and Transmission Operators in its Reliability Coordinator Area
Notify other Balancing Authorities and Transmission Operators in its Reliability Coordinator Area. EOP-011 - Each Reliability Coordinator that has a Balancing Authority experiencing a potential or actual Energy Emergency within its Reliability Coordinator Area shall declare an Energy Emergency Alert, per Attachment 1. In addition, each Reliability Coordinator that receives an Emergency notification from a Transmission Operator or Balancing Authority within its Reliability Coordinator Area shall notify, within 30 minutes from the time of receiving notification, other Balancing Authorities and Transmission Operators in its Reliability Coordinator Area, and neighboring Reliability Coordinators.
A severe lightning storm has hit your transmission system. Two 345 kV lines have been damaged and are unable to be re-energized. Two large generators of 500 MW and 700 MW have tripped off line. No additional generators are available to bring on line. The parallel 230 kV and 138 kV lines are loaded at their emergency limits. What should a power System Operator do? Place all the shunt reactors and capacitors in service. Wait for a generator to get back on line. Shed load Remove the relay protection from the over loaded transmission lines to prevent them from tripping.
Shed load. Transmission Operator shall shed customer load rather than risk an uncontrolled failure of components or cascading outages of the Interconnection. The loss of the 345 kV lines and generators has pushed the transmission system into an SOL violation. The system operator has to shed load in these emergency conditions. Without load shedding, the overloaded lines could also trip and cause cascading outages.
If an unscheduled transmission bus outage results in transmission lines becoming overloaded, the system operator should use generation re-dispatch to relieve the overloaded line conditions. If generation re-dispatch does not relieve the problem, the system operator should consider which actions? Requesting additional Interchange Shedding load in an area that would relieve the line-loading problem. Opening the line breakers to the overloaded lines. Contacting the field personnel to check on the bus outage duration.
Shedding load in an area that would relieve the line-loading problem. EOP-011 states Each Transmission Operator shall develop, maintain, and implement one or more Reliability Coordinator-reviewed Operating Plan(s) to mitigate operating Emergencies in its Transmission Operator Area. If a bus outage results in an overload, an Operating Plan should have been developed to mitigate. One of the options the system operator has if generation redispatch does not relief an overload is to shed load.
A Generator Operator has determined that one of its generators cannot meet its maximum rated reactive power due to bearing vibration. Which of the following actions should the Generator Operator take? Should place the AVR in manual and increase MVARs to maximum. Should take the generator off line until problem can be fixed. No action is required. Should notify its Transmission Operator of the new limit.
Should notify its Transmission Operator of the new limit. It is vital for the Transmission Operator to know how much reactive power is available. The Transmission Operator must have sufficient reactive reserves in case of an emergency such as the loss of a major transmission line or generating unit. NERC specifically says that the Generator Operator shall inform the Transmission Operator when reactive resources are limited or unavailable as the result of mechanical or electrical problems. - NERC Standard VAR-001
Which of the following would you expect to experience during a Geo-Magnetic disturbance? System voltages increase beyond safe operating levels. Requiring the operator to take action to absorb VARs from the system or decrease voltage schedules. Significant low frequency induced currents enter the system through the grounded transformer neutrals, causing system overloads and harmful system wide harmonics. System frequency declines below an acceptable operating level, and generator governors are required to take action to arrest the frequency decline. Significant high frequency induced currents enter the system through the grounded transformer neutrals, causing system overloads and harmful system wide harmonics.
Significant low frequency induced currents enter the system through the grounded transformer neutrals, causing system overloads and harmful system wide harmonics. EPRI 2009 Power System Dynamics Tutorial, Chapter 9 & 11: The major harm from GMDs results from low frequency GICs (geomagnetic induced currents) entering the power system via the transformer grounded neutrals. These currents can be so large that the transformers are damaged and severe harmonics are produced.
When a system is in an island, how much load needs to be shed to compensate for a 1 Hz deviation in frequency? Three to Five percent Six to Ten percent One to Two percent Ten to Twelve percent
Six to Ten percent. EOP-011 requires Balancing Authorities and Transmission Operators to develop Operating Plans, that include load shed. The NERC Electric System Restoration Reference Document states, "In an islanded area, generation and load should be adjusted in small increments to minimize the impact on frequency. As a general rule, shed 6 to ten percent of load to restore the frequency approximately 1 Hz."
Re-synchronization with the Interconnection should only be attempted at a _____________. Generating plant with an auto-synchronization relay Substation with an auto-synchronization relay Substation with a synchroscope Substation with auto re-closing relays
Substation with a synchroscope. EPRI 11.6.4 When a restoration plan is first developed, the plan's developers must determine where synchronizing equipment is located within the power system and whether the equipment is at the correct locations. The most likely place for restoration is at a substation equipped with the sync scope.
The Disturbance Control Standard measures a Balancing Authority's response to a rapid loss of _____________. interchange. demand for energy. supply of energy. ACE.
Supply of energy. Because generator failures are far more common than significant losses of load, and because Contingency Reserve activation does not typically apply to the loss of load, the application of the Disturbance Control Standard is limited to the loss of supply and does not apply to the loss of load. NERC Standard BAL-002
The Disturbance Control Standard (DCS) specifies that the ACE must return to zero or its pre-disturbance level within how much time following the start of a disturbance. five minutes fifteen minutes ten minutes twenty minutes
The Disturbance Control Standard (DCS) specifies that the ACE must return to zero if its ACE just prior to the Reportable Disturbance was positive, or equal to zero, or if the ACE was negative just prior to the Disturbance, the Balancing Authority shall return ACE to its pre-disturbance level within fifteen minutes following the start of a disturbance. - NERC Standard BAL-002 Disturbance Control Performance
As a Generator Operator, you realize that your generator voltage is swinging wildly. You place your generator voltage regulator on manual, and adjust the voltage and reactive levels on the generator. Who do you contact and inform about the status of your generator voltage regulator? The Balancing Authority. The Generator Operator. The Reliability Coordinator. The Transmission Operator for the area the generator is located.
The Transmission Operator for the area the generator is located. Each Generator Operator shall provide information to its Transmission Operator on the status of all generation reactive power resources, including the status of voltage regulators and power system stabilizers. It is vitally important for the Generator Operator to inform the host Transmission Operator. The Transmission Operator has to know what reactive reserves, static and dynamic, will be available in the event of an emergency. - NERC Standard VAR-001
Which of the following conditions could lead to or hasten a cascading system disturbance that may have been triggered by a lightning storm? Having high speed tripping (3 cycles or less) on several major high voltage transmission lines. The incorrect setting of synch-check relays, (narrow range), having high speed tripping (3 cycles or less) removed from several major high voltage transmission lines and removing high speed reclosing on transmission line relays. Removing high speed reclosing on transmission line relays. The incorrect setting of synch-check relays, (large range).
The incorrect setting of synch-check relays, (narrow range), having high speed tripping (3 cycles or less) removed from several major high voltage transmission lines and removing high speed reclosing on transmission line relays. Relay protection is an important part in preventing wide spread separation and cascading outages. Having the synch-check relays set so narrow that they do not allow the circuit breakers to reclose following a line fault can result in large power angles due to loading on the remaining facilities. Not having high speed tripping on the lines close to the generators may cause tripping of generators by allowing them to accelerate longer while feeding the fault. The lack of high speed reclosing increases the impedance on the system by having the lines separated longer than necessary. This will increase the possibility of having power angles increase, which could lead to instability.
If a line is loaded above its SIL, how does that affect the line and the voltage? The line becomes more inductive and the voltage drops. The line becomes less inductive and the voltage increases. The line becomes less inductive and the voltage in constant. The line becomes more inductive and the voltage increases.
The line becomes more inductive and the voltage drops. The Surge Impedance Loading, or SIL, is the MW loading on a transmission line at which the line's natural reactive power production equals its reactive power usage. If the MW loading exceeds the SIL, the transmission line will consume more MVAR than it is producing causing voltage to decline. EPRI Figure 5-8
The system operator notices that a transmission line has a net VAR flow of 25 MVAR's into the line. Which of the statements is true under this condition? The line is capacitive. The line is transferring the optimum load. The line is nearing voltage collapse. The line is inductive.
The line is inductive. When a transmission line is using VAR's from the system, it is considered to be inductive and acts more reactive than capacitive.
The largest single contingency for Balancing Authority A is a unit rated at 900 MW. Which of the following disturbances would constitute a reportable disturbance for DCS evaluation based on the NERC DCS criteria? The loss of two 400 MW units 30 seconds apart. The loss of the 900 MW generating unit at 60% output. The loss of a 700 MW generating unit at 100% output. The loss of 750 MW of firm load.
The loss of two 400 MW units 30 seconds apart. BAL-002, Reportable Balancing Contingency Event (NERC Glossary) is Any Balancing Contingency Event occurring within a one-minute interval of an initial sudden decline in ACE based on EMS scan rate data that results in a loss of MW output less than or equal to the Most Severe Single Contingency, and greater than or equal to the lesser amount of: (i) 80% of the Most Severe Single Contingency, or (ii) the amount listed for the applicable Interconnection. Eastern Interconnection - 900 MW, Western Interconnection - 500 MW, ERCOT - 800 MW, Quebec - 500 MW
A System Operator must operate the transmission system so that instability, uncontrolled separation, or cascading outages will not occur as a result of _________. Any unplanned outage Normal operations The most severe single contingency External disturbances
The most severe single contingency. TOP-001, To prevent instability, uncontrolled separation, or Cascading outages that adversely impact the reliability of the Interconnection by ensuring prompt action to prevent or mitigate such occurrences. Real-time Assessment (NERC Glossary) is an evaluation of system conditions using Real-time data to assess existing (pre-Contingency) and potential (post-Contingency) operating conditions. The assessment shall reflect applicable inputs including, but not limited to: load, generation output levels, known Protection System and Special Protection System status or degradation, Transmission outages, generator outages, Interchange, Facility Ratings, and identified phase angle and equipment limitations. Real-time assessments must be performed at least every 30 minutes.
If the frequency on both sides of an open breaker are exactly matched, which of the following statements is true? The phase angle across the breaker is zero. The phase angle across the breaker is constant. The voltage magnitude across the breaker is matched. The phase angle across the breaker is 180 degrees.
The phase angle across the breaker is constant. Frequencies being matched does not necessarily mean that the phase angle is zero. The two voltage wave forms could be at the same frequency, but not in phase, meaning the wave forms reach their peak at different times. However, if the frequencies are matched exactly, the phase angle difference will remain constant.
Which of the following describes Power Factor? The ratio of real power and apparent power Difference between real and reactive power Factors of magnetic strength Equation to determine real power
The ratio of real power and apparent power. Power Factor is MW/MVA. For example, a 50 MVA Generator that is producing 40 MW and 30 MVAR. 40/50 = 0.80 80%
As system loads increase, how should the System Operator respond to the impact of load increase on the power system? Tap changing transformers should be turned to manual; capacitor banks should be removed from service. Capacitor banks should be removed from service; generator should be operating a maximum reactive output. The reactive requirements will increase; the operator must ensure voltage levels and reactive resources are controlled. The reactive requirements will decrease and the operator should reduce voltage.
The reactive requirements will increase; the operator must ensure voltage levels and reactive resources are controlled. NERC Standard VAR-001 Purpose is to ensure that voltage levels, reactive flows, and reactive resources are monitored, controlled, and maintained within limits in Real-time to protect equipment and the reliable operation of the Interconnection. Transmission Operators shall have sufficient resources to regulate voltage levels under normal and Contingency conditions. As powerflows increase due to system demand/loads, Transmission lines will require more reactive power support. Heavily loaded transmission lines will become more inductive.
Two adjacent lines exist in a Balancing Area that are the same length and have the same ratings. One line is overhead and the other is underground. How do these two lines respond as load picks up through the day? The load increase will be distributed evenly over the two lines. The overhead line will carry more of the load increase. The line with the higher impedance will carry more of the load. The underground line will carry more of the load increase.
The underground line will carry more of the load increase. EPRI 2009 Power System Dynamics Tutorial, Section 3.3.2
System Operators monitor system conditions closely so that: They can determine market participation They can identify maintenance plans They can keep busy They can identify changes that may signal a problem
They can identify changes that may signal a problem. A Power System is monitored in real-time by personnel trained to recognized actual or potential problems. Many parameters and data points are monitored as stated in TOP and IRO standards.
System Operators performing real-time, reliability related tasks on the BES must be certified as a System Operator and which of the following? Experienced in real time Trained using a Systematic approach CIP certified Willing to make hard decisions
Trained using a Systematic approach. To ensure that personnel performing or supporting Real-time operations on the Bulk Electric System are trained using a systematic approach. NERC PER-005 Purpose
Who must have plans for operator controlled manual load shedding to respond to real-time emergencies? Transmission Owner All Balancing Authorities Reliability Coordinator Transmission Operator or Balancing Authority
Transmission Operator or Balancing Authority. EOP-011, Emergency Operations. Each Transmission Operator and Balancing Authority shall have Operating Plans that include provisions for operator controlled manual load shedding to respond to real-time emergencies.
A Generator Operator has some vibration problems with a 500MW coal fired steam generator. As the result of the vibration problems the Generator Operator has to set the maximum reactive power production for that unit at 25 Megavar instead of the normal 200 Megavar. Who should the generator operator notify as the result of this problem? Regional Reliability Organization System Coordinator Transmission Operator Department of Energy (DOE)
Transmission Operator. It is vital for the Transmission Operator to know how much reactive power is available. The Transmission Operator must have sufficient reactive reserves in case of an emergency such as the loss of a major transmission line or generating unit. NERC specifically says that the Generator Operator shall inform the Transmission Operator when reactive resources are limited or unavailable as the result of mechanical or electrical problems. - NERC Standard VAR-001.
What is the most important information for forecasting load? Weather forecast Load history Planned transmission outages Planned generation outages
Weather forecast. Weather forecast is the most important information for a load forecast. Load history is important as well, but without weather forecast it is useless.
When or under what condition should the Transmission Operator disconnect from the interconnection? When the frequency is below 57 Hz. Only if directed by the Reliability Coordinator When ordered to by the NERC. When their system is in severe violation of an IROL or SOL
When their system is in severe violation of an IROL or SOL. Application of this is extremely rare and likely prior to a Blackout event. However, if a Transmission operator is experience severe loading an is in imminent danger of tripping and damaging equipment then a controlled separation is more desirable.
A 100 mile transmission line from Substation A to Substation B trips. The field crew reports a Zone 1 target at Substation A and a Zone 2 target at Substation B. The fault is anticipated to be _________. within 10 miles of B outside of the line segment midway between A and B within 10 miles of A
Within 10 miles of A. Zone 1 of a distance relay can detect a fault within approximately 90% of the line. Zone 2 will reach out past the other end of the line. The Zone 2 from Bus B means that the fault is past the 90% reach of Zone 1 or 90 miles from Bus B, or within 10 miles of Bus A.
A Balancing Authority has a 200 MW/0.1 Hz frequency bias with zero schedules. Frequency is 60.00 Hz and ACE is 0, what should the sum of all the Balancing Authorities Interconnection ties equal? Total Generation Small MW amount out of the BA Zero System Load
Zero. Assuming frequency schedule is 60.00 Hz since it is not stated otherwise, the frequency portion of the ACE equation is zero. Since ACE is zero, the Interchange portion of the equation must also be zero. Since there Scheduled Net Interchange is zero, the Net Actual Interchange must also be zero, which is the sum of the Interconnection ties.
Bulk Electric System facilities shall not be removed from service by a System Operator if removing those facilities would burden neighboring systems unless: 1) the Generator Operator coordinates with the Transmission Operator 2) the Transmission Operator coordinates with the Reliability Coordinator 3) the market is making money 4) The Generator Operator gets permission from its Purchase-Selling Entity 3 and 4 2 and 3 1 and 2 2 and 4
1 and 2. TOP-003, Operational Reliability Data - Transmission Operators maintain specification for the data necessary to perform Operational Planning Analyses, Real-time Monitoring and Real-time Assessments. IRO-010, RC Data Specification also states the Reliability Coordinator shall specify the data to perform its Operational Planning Analyses, Real-time Monitoring and Real-time Assessments. Prior to taking equipment outage, a Real-time Assessment (Contingency Analysis) should be performed to ensure that not overloads would burden your system or neighboring systems.
Which of the following is considered to be a reliability event? 1) Low voltage 2) Loss of a small generator 3) SOL or IROL exceeded 4) Loss of Energy Management System 3 and 4 1 and 2 2 and 3 1 and 3
1 and 3. Reliability event is referred to as an event that affects or may potentially affect the reliability of the Bulk Electric System, such as loss of generation, transmission or load or violations or potential violations of operating limits.
A Balancing Authority anticipating an operating capacity or energy emergency shall perform all actions necessary including 1) bringing on all available generation 2) postponing equipment return 3) scheduling interchange sales 4) being prepared to reduce firm load. 1 and 4 3 and 4 1 and 2 2 and 3
1 and 4. EOP-011, Emergency Operations, Each Balancing Authority shall develop, maintain, and implement one or more Reliability Coordinator-reviewed Operating Plans to mitigate Capacity Emergencies and Energy Emergencies with its Balancing Authority Area. The Operating Plan should include, notification, Energy Emergency Alert request, manage generating resources, and reduction of loads.
Which of the following Transmission lines would be the best choice to energize a generating facility during system restoration? 25 mile, overhead TX line 25 mile, underground TX line 10 mile, underground TX line 10 mile, overhead TX line
10 mile, overhead TX line. EPRI 2009 Power System Dynamics Tutorial, Chapter 11.
Which entity shall develop and maintain an Operating Plan for current-day and next-day operations and provide their Operating Plan to its Reliability Coordinator? 1. Reliability Coordinators 2. Transmission Operators 3. Balancing Authorities 4. Transmission Planners 1 and 2 3 and 4 2 and 4 2 and 3
2 and 3. TOP-002, Each Transmission Operator and Balancing Authority shall develop Operating Plans and provide those plans to the Reliability Coordinator.
What type of relays would you most likely find on each end of a 75 mile 230KV transmission line? 87 Differentials 21 Distance and a 64 Ground or 67 Directional Overcurrent 49 Thermals 27 Voltage or 25 Synchronous check
21 Distance and a 64 Ground or 67 Directional Overcurrent. Transmission lines are usually protected by distance relays and ground overcurrent relays. Whether the relays are electromechanical, solid state, or computer type relays does not matter when it comes to the numbering for the distance relays. That number will usually be a 21 set by IEEE. The ground relay may have a different number. For example, if the ground relay is an older electromechanical directional ground relay, there might be a 64. If the relay is the newer computerized relay, there will be a 67, which represents a directional overcurrent type relay. Whatever the case, lines are usually protected by 21 distance and 64 or 67 directional ground or directional overcurrent relays. - NERC Standard PRC-001 Requirements R1, Page 1 of 2
Substation transformer 100/44 rated at 50 MVA has 30 MW entering the primary side. What is the power output at the secondary side? 44 MW 300 MW 40 MVAR 30 MW
30 MW. Power = Voltage x Current In this example the transformer will step down the voltage from 100 kV to 44 kV and the current will increase but the power will remain the same (assuming losses are zero)
A Transmission Operator area has an instantaneous automatic Under-Frequency Load Shed Scheme segmented into a sequence of 4 Steps: Step 1 = 59.500Hz. removes 25MW; Step 2 = 59.300Hz. removes 20MW; Step 3 = 59.100Hz. removes 20MW; Step 4 = 58.900Hz. removes an additional 15MW. Step 3 & 4 will automatically reset and re-close restoring load when the frequency returns to 60.00 Hz. A large event occurs causing the system frequency to fall to 59.000Hz. and returns to 60.00Hz after 12 minutes. Assuming a constant load factor, what is the total load the TOP must restore manually once the frequency has recovered to 60.000Hz.? 65 MW 25 MW 45 MW 80 MW
45 MW. The frequency falls to 59.000Hz and according to the UFLS Scheme Steps 1, 2 & 3 will operate instantly removing a total of 65 MW. The Step 3 UFLS Scheme will automatically reset and reclose once the system frequency returns to 60Hz therefore the 20 MW of Step 3 load has been restored automatically. The remaining Step 1- 25MW & 2- 20MW loads must be manually reset and closed; total 45MW.
A major disturbance occurs with substantial loss of load. The disturbance report states that the cause of the disturbance was angle instability. Angle instability is the result of: Exceeding voltage limits. A loss of generator excitation. A shortage of reactive reserve. A loss of magnetic bonds.
A loss of magnetic bonds. Angle instability refers to the inability of the system to maintain magnetic bonds from one area to another due to large power angles. Angle instability occurs when generators lose their magnetic bond. Angle stability is chiefly a function of generator stability. When torque /power angles are too large, and disturbances occur, magnetic bonds may be lost. When a power system experiences angle instability, system voltages will likely collapse due to excessive voltage phase angles. EPRI Chapter 7
What is a Power Transfer Distribution Factor (PTDF)? Congestion management solutions to the most severe single contingency A measure of the responsiveness or change in electrical loading used for pre-contingency analysis Post contingency results and configuration of a system under study Outage results that measures the electrical loading of transmission area based on system loading and generation
A measure of the responsiveness or change in electrical loading used for pre-contingency analysis. NERC Glossary: In the pre-contingency configuration of a system under study, a measure of the responsiveness or change in electrical loadings on transmission system Facilities due to a change in electric power transfer from one area to another, expressed in percent (up to 100%) of the change in power transfer
How is the reactive power - MVAR output of a generator increased? By increasing the generator rotor DC field current. By increasing the MW output of the generator. By increasing the generator stator DC current. By increasing the input to the prime mover (steam to turbine).
By increasing the generator rotor DC field current. The DC current flowing through the rotor windings determines the field strength which in turn determines the VAR output and generator terminal voltage. By increasing this DC current, the VAR production goes up.
When performing system restoration, a Transmission Operator should be concerned with line __________. Capacitance Inductance Resistance Impedance
Capacitance. In restoration conditions, transmission lines and transformers are often initially loaded at very low levels. The initial voltage control concern is therefore high voltage. Sufficient Mvar absorption capability must be located close to the areas where the higher voltages are expected to occur. EPRI 11.2.1
Line sagging occurs during high load conditions which cause extreme amounts of current to flow on the transmission lines, thereby: Causing surge impedance loading Causing high power losses, need for reactive power and heating of the line Causing high voltage that weighs down the line Causing tripping when reaching 100% of limit
Causing high power losses, need for reactive power and heating of the line.
The Transmission Operator Area is All equipment in the Balancing Authority area Substation and transmission lines 100 kV or above The control room where the Transmission Operator resides. Collection of Transmission assets that the TO is responsible for operating
Collection of Transmission assets that the TO is responsible for operating.
In an island, what is the most appropriate AGC mode of operation? Off Constant or Flat Frequency Constant Interchange or Flat Tie Tie-line bias control
Constant or Flat Frequency. Normally, the Tie Line Bias control mode, which compares the Net Actual Interchange to the Net Scheduled Interchange plus the Balancing Authority's frequency bias obligation, should be used. However, if a Balancing Authority is operating asynchronously (separated from the Interconnection), it should switch to Flat Frequency Control since its tie lines are no longer connected to the Interconnection. It is important for the Balancing Authority to maintain 60 Hz. In the Flat Frequency control mode, ACE is looking only at the system frequency, not the Interchange portion of the ACE equation.
When evaluating a line outage request, you must show that your transmission system can handle the outage without violating IROL or SOL due to which of the following? Extra High Voltage Tie-line outages Protection Systems misoperations Large Generator failures Contingencies
Contingencies. Several NERC Standards address this concept of planning for contigencies Each Transmission Operator shall ensure that an Operational Planning Analysis and Real-time Assessments are performed. Also each Transmission Operator shall initiate its Operating Plan to mitigate a SOL exceedance identified as part of its Real-time monitoring or Real-time Assessment. NERC Standard TOP-001 Operational Planning Analysis includes defined contingencies. It is an evaluation of projected system conditions to assess anticipated (pre-Contingency) and potential (post-Contingency) conditions for next-day operations. The evaluation shall reflect applicable inputs including, but not limited to, load forecasts; generation output levels; Interchange; known Protection System and Special Protection System status or degradation; Transmission outages; generator outages; Facility Ratings; and identified phase angle and equipment limitations. NERC Glossary
When the frequency of an Interconnection decreases due to the loss of a large generator, what will frequency do until generator governors respond and load decreases? hold steady at a lower amount continue to raise generator AVR response overload the power system continue to drop
Continue to drop. Application: When Interconnection frequency suddenly decreases due to the loss of a large generator, the frequency will continue to drop until the combination of synchronized generator governor response and the decrease in load due to the lower frequency results in a re-balancing of Generation/Load at that lower frequency. The output of the lost generator must then be replaced in order to get Interconnection Frequency back to normal range - 60.00 Hz.
Transmission line AB has a SOL of 375 is currently loaded at 450. Generator A has a shift factor of (- .50) and Generator B has a shift factor of (.25) related to this line. If these are the only units available to relieve the overload, what would be the re-dispatch order to relieve the overloaded line? Increase Gen B by 25 and decrease Gen A 50. Decrease Gen A 100 and increase Gen B 100. Decrease Gen B 100 and increase Gen A 100. Decrease Gen A 50 and decrease Gen B 25.
Decrease Gen B 100 and increase Gen A 100. 75 divided by (Sfa - SFb) = 75 / -.75 = -100 change in Gen B and +100 change for Gen A.
When a Balancing Authority has exhausted all other options and can no longer provide its customers' expected energy requirements, what can be used to obtain needed capacity and energy? Capacity Warning Imbalance Event Energy Emergency Alerts Demand Alert
Energy Emergency Alerts. EOP-011 Emergency Operations, Energy Emergency Alert (EEA) process.
150 MW is flowing into the high side of a 200 MVA transformer. If the transformer windings have a 2 to 1 ratio what MW value is flowing out of the low side winding of the transformer? 150 MW 75 MW 250 MW 200 MW
150 MW. Power flow through a transformer is constant. The transformer steps up or down the voltage, but power flow does not change.
How many MVARs does a 50 MVAR capacitor bank provide at 90% of nominal voltage? 50 MVAR 45 MVAR 35 MVAR 40 MVAR
40 MVAR. Application: As the system voltage decreases, the capacitor bank MVAR output decreases in proportion to the square of the voltage. Remember the formula is MVAR output = MVAR rating x (Voltage actual/Voltage rating)2. Therefore, the MVAR output = 50 x (.90)2 MVAR output = 50 x .81, which equals 40.5.
A transformer rated at 50 MVA is currently carrying 30 MW of load. At this load, what is the maximum allowable MVAR flow through the transformer? 40 MVAR 0 MVAR 50 MVAR 30 MVAR
40 MVAR. Using the power triangle, this is a 3-4-5 case, or 30-40-50. Therefore 40 MVAR is the limit with the 30 MW flow.
A 345 kV line has a MW flow of 400 and a Mvar flow of 300. The thermal limit of the line is 600 MVA. Assuming the line voltage is 352 kv, what is the MVA loading on the line and is the line within its thermal limits? 500 MVA/Yes 700 MVA/Yes 700 MVA/No 500 MVA/No
500 MVA/Yes. 400 MW's and 300 MVAR's = 500 MVA. A2 + B2 = C2
You are ready to restore power to a generator facility. Which of the following Transmission lines would be the best choice to energize the facility? 10 mile, overhead transmission line. 10 mile, underground transmission cable. 25 mile, overhead transmission line. 25 mile, underground transmission cable.
10 mile, overhead transmission line. The best choice for system restoration is an overhead line because it is less capacitive than underground lines. The shortest line is best due to less exposure to a fault and less Ferranti effect. Knowledge of transmission line differences and energizing effects. EPRI Power System Tutorial
A report shall be submitted to NERC following the shedding of a least how much firm load? 300 MW 100 MW 200 MW 50 MW
100 MW. EOP-004 states, Firm load shedding of 100 MW or more to maintain the continuity of the bulk electric system." Firm load shedding of 100 MW or more to maintain the continuity of the bulk electric system also requires a report to DOE. NERC will accept the same report.
Frequency and voltage magnitude on each side of the breaker and the power angle across the breaker must be within proper limits when synchronizing transmission systems that have separated or islanded. If not within proper limits, the system operator should: Adjust the tap changer on the nearest transformer Adjust the power angle on one side of the breaker to 90 degrees Adjust area generation levels Open additional lines until the voltage is matched
Adjust area generation levels. By adjusting generation to load balance in one or both areas, the frequencies can be adjusted until within limits of the synchronizing relay.
The algebraic sum of active power (MW) and reactive power (MVAR) is: Watts (W) Volt-Amp-Reactive (VAR) Apparent Power (MVA) Current (I)
Apparent Power (MVA)
Which entity shall have an Operating Plan for next-day operations? Bulk Electric System Balancing Authority and Transmission Operators All Reliability Coordinators System Planners
Balancing Authority and Transmission Operators. (NERC TOP-002) The Transmission Operator should perform Operational Planning Analysis and have next-day Operating Plans to address potential SOL. The Balancing Authority should also have next-day plans to address generation-interchange-load balance.
If a real-time control center becomes non-operational for whatever reason, the real-time system operators are expected to _________________. read the Operating Plan for backup functionality for the first time change to automatic control and leave for the day continue to meet its functional obligations with regard to the reliable operations of the BES notify its Regional Reliability Organization
Continue to meet its functional obligations with regard to the reliable operations of the BES. Each Reliability Coordinator, Balancing Authority, and Transmission Operator shall have a current Operating Plan describing the manner in which it continues to meet its functional obligations with regard to the reliable operations of the BES in the event that its primary control center functionality is lost. - NERC Standard EOP-008
Relays that are used primarily for power system equipment protection and not line protection are defined as __________. Overcurrent Relays Pilot Relays Distance Relays Differential Relays
Differential Relays. Differential Relays: Relays that are used primarily for power system equipment protection and not line protection. Differential Relays detect if the currents entering and leaving a device are balanced or unbalanced. If the currents are not within a certain range of each other then the differential relay will operate isolating the electrical equipment such as a generator, bus, or transformer from any further source of energy. EPRI Glossary and 2.5.6
If firm Load shed is imminent or in progress, what level Energy Emergency Alert is required? EEA 0 EEA 1 EEA 3 EEA 2
EEA 3. EOP-011 Emergency Operations, Attachment 1-EOP-011-1 Energy Emergency Alerts Level 3 is Firm load interruption imminent or in progress.
Which type of emergency condition is due to not being able to meet the load requirements of an entities retail customers? Capacity Emergency Load Shed System Operating Limit Energy Emergency
Energy Emergency.
A long transmission line is placed in service with the other end of the line open, what would be the result at the closed end? Bus voltage would increase. Nothing. Bus voltage will decrease. MVARs would begin flowing into the open ended line.
Bus voltage would increase. When you have a transmission line closed at one-end and open at the other end, voltage at the open end of a transmission line will increase due to an effect called Ferranti Rise. The transmission line would act similar to a shunt capacitor and this would most likely result in an increase in the bus voltage.
When synchronizing sections of the transmission system that have separated or islanded, frequency and voltage magnitude on each side of the breaker and the power angle across the breaker must be within proper limits. In order to bring these values within proper limits, the system operator should _____________________. Adjust the tap changer on the nearest transformer. Adjust the power angle on one side of the breaker to 90 degrees. Adjust generator MW and MVAR output in one of the areas. Open additional lines until the voltage is matched.
Adjust generator MW and MVAR output in one of the areas. EPRI 2.5.7 Power flows from areas of more positive to less positive voltage angles, and reactive power flows from areas of higher voltage to areas of lower voltage. Therefore, to minimize flows across the breaker as it is being closed, these values must be within acceptable ranges on each side of the breaker before closing is attempted. Power flow can be manipulated by adjusting generation on one side of the open breaker. Generation can be raised or lowered to adjust the speed of one section of the system with respect to the other. The power angle is the difference in voltage angles at two points on the system. In this case, when we are discussing the power angle across the breaker we are referencing the difference in voltage angles of the two busses which are connected by a transmission lines that we are trying to synchronize. Most technical references, such at the EPRI Interconnected Power System Dynamics Tutorial, on which the NERC exams are partially based, stress the importance of minimizing power angle across the breaker.
A Balancing Authority anticipating a capacity or energy deficiency emergency shall perform which of the actions? transmission line switching all necessary actions voltage reduction load shedding
All necessary actions. EOP-011, Emergency Operations - A Balancing Authority is responsible for Load-Interchange-Generation balance. If a Balancing Authority foresees an imbalance, they should postpone maintenance, schedule interchange purchases, and bring on available generation. If those actions are not enough the BA will enter the EEA process and be prepared to shed firm load.
Intentional human actions, previously known as acts of sabotage have to be reported to government agencies, law enforcement and regulatory bodies. Which events are considered reportable? Threats to a control center Damage or destruction of a Facility All of the above Physical threat of a Facility
All of the above. EOP-004 Event Reporting. The term sabotage has been replaced by intentional human action since it was difficult to differentiate between sabotage and vandalism. Responsible Entities must have an event reporting Operating Plan. Responsible Entities are the same entities that the EOP-004 apply to: Reliability Coordinator, Balancing Authority, Transmission Operator, Transmission Owner, Generator Owner, Distribution Provider
A system operator is anticipating a heavy load day. Which of the following would alert a system operator to a potential voltage collapse? System voltages are low ULTC adjustments fail to change the voltage Reactive power outputs approaching maximum All the Above
All the Above.
What is the purpose of a Transformer? Changing the voltage levels of electricity Allows for efficient long-distance transfer of electricity Minimize losses in the power system All the Above
All the Above.
All real-time system operators must monitor ________. power flow within the system status of generation and transmission system Voltage All the Above
All the Above. (NERC TOP-003) The Standard states that the TOP and BA shall distribute its data specification to entities that have data required for Real-Time Monitoring and Real-Time Assessment. A System Operator needs to know power flowing on tie-line and internal transmission lines, status of generation and transmission, as well System Voltages for adequate Real-Time Monitoring and reliability.
When energy demand and operating reserves require all resources dedicated to firm load and maintaining regulating reserves, what action(s) should be taken? Issue NERC EEA1 Request local Balancing Authorities to start off-line generating resources. Request generation output at maximum levels All the Above
All the Above. EOP-011 Emergency Operations, Attachment 1-EOP-011 Energy Emergency Alerts Level 1 is when The Balancing Authority is experiencing conditions where all available generation resources are committed to meet firm Load, firm transactions, and reserve commitments, and is concerned about sustaining its required Contingency Reserves. The BA would ensure that all on-line generation is a maximum output and available generation on-line.
A power system with long transmission lines that connect remote generation to load centers is more likely to have SOLs or IROLs determined by: Transmission thermal limitations Angle stability limitations Generator thermal limitations Generator voltage limitation
Angle stability limitations. Each Transmission Operator shall operate within the Interconnection Reliability Operating Limits (IROLs) and System Operating Limits (SOLs) to maintain reliability. When generators are connected to load centers using long transmission lines, large power angles are often required to move power to the load center. This results in angle stability limitations being the most likely factor in when evaluating (contingency analysis) the loss of other elements in the Power System.
How often should the Transmission Operator and Balancing Authority review and update their Loss of Control Room Functionality Operating Plan? Annually Every two years Every three years As needed
Annually. EOP-008, Each Reliability Coordinator, Balancing Authority, and Transmission Operator shall annually review and approve its Operating Plan for backup functionality.
You experience a full system shutdown. You are in the process of restoring load and you are concerned about re-collapsing the system. Which is the best approach in the restoration process that will help ensure your system will be restored successfully? If the system has stabilized at below 60 HZ, shed 15% - 20% of the load to raise the frequency to 61 HZ. Operating reserves should be maintained to cover the largest generator currently in service. Maintain frequency between 59.5 HZ and 60.5 HZ. Avoid energizing loads in excess of 5% of the online generation capacity of the system.
Avoid energizing loads in excess of 5% of the online generation capacity of the system. Increasing load too rapidly could result in a re-shutdown of the system. The thumb rule for load restoration is blocks of load not to exceed 5% of the online generation capacity of the system.
There is a high voltage alarm on a 500 MW generator. The generator operator notices that the overvoltage relay repeatedly attempts to lower the generator voltage but can't. The generator operator quickly switches the generator voltage regulator from automatic to manual and manually adjusts the voltage of the generator back down to a normal voltage level. After inspection, the test engineers indicate that the voltage regulator is broken, and will be out for several hours. At what reactive level should the generator operator have on the generator while the voltage regulator is out of service for repairs? Take the generator off line immediately . Operate the generator voltage within its safe limits at a level to maintain the voltage schedule at the interconnection of the generator facility and the transmission operators common point. Operate the generator at just under the high voltage alarm point to make sure the generator does not slip a pole in case of a voltage emergency on the transmission system. Keep the generator at the lowest voltage level as possible to keep from damaging it from unexpected high voltage levels.
Operate the generator voltage within its safe limits at a level to maintain the voltage schedule at the interconnection of the generator facility and the transmission operators common point. NERC Standard VAR-002: To ensure generators provide reactive support and voltage control, within generating Facility capabilities, in order to protect equipment and maintain reliable operation of the Interconnection. Generator Operators shall operate each generator connected to the interconnected transmission system in the automatic voltage control mode (with its automatic voltage regulator (AVR) in service and controlling voltage) or in a different control mode as instructed by the Transmission Operator.
Several lines in your area are out of service for routine relay maintenance. Severe thunderstorms are expected during peak demand later in the day. What action should the System Operator take? Place additional generation on line. Place lines back in service with normal protection. Place lines back in service without normal protection. No action is necessary.
Place lines back in service with normal protection. TOP-001 Transmission Operations, to prevent instability, uncontrolled separation, or Cascading outages that adversely impact the reliability of the Interconnection by ensuring prompt action to prevent or mitigate such occurrences.
Which of the following would not be considered in determining ratings on transmission facilities? Power Transfer Distribution Factor Short-term loading limits Voltage limits Thermal limits
Power Transfer Distribution Factor. Facilty Ratings are based upon equipment ratings. System Operating Limits (SOL) are the value (such as MW, Mvar, amperes, frequency or volts) that satisfies the most limiting of the prescribed operating criteria for a specified system configuration to ensure operation within acceptable reliability criteria. System Operating Limits are based upon certain operating criteria. These include, but are not limited to: • Facility Ratings (applicable pre- and post-Contingency Equipment Ratings or Facility Ratings) • transient stability ratings (applicable pre- and post- Contingency stability limits) • voltage stability ratings (applicable pre- and post-Contingency voltage stability) • system voltage limits (applicable pre- and post-Contingency voltage limits) NERC Glossary
The daily plan is usually generated using Unit Commitment and ________ software. OASIS IDC emergency scenario power flow simulation
Power flow simulation. Operational Planning Analysis (OPA) is required for daily planning. OPA is an evaluation of projected system conditions to assess anticipated (pre-Contingency) and potential (post-Contingency) conditions for next-day operations. The evaluation shall reflect applicable inputs including, but not limited to, load forecasts; generation output levels; Interchange; known Protection System and Special Protection System status or degradation; Transmission outages; generator outages; Facility Ratings; and identified phase angle and equipment limitations. NERC Glossary
UVLS schemes are designed to drop load in__________. pre-selected blocks industrial load areas high load areas low load areas
Pre-selected blocks. Under Voltage Load Shed (UVLS) schemes are designed to drop load in pre-selected blocks. Each Load Shed block should help increase voltage. If voltage continues to decline another block of load will be shed.
Which of the following actions is appropriate for preserving the reliability of the Interconnection during a low voltage emergency? Switch in reactors Arrange for interchange sales during high price periods Raise generator voltages Removing key transmission lines from service
Raise generator voltages. Generators can produce dynamic reactive resources which are critical in controlling voltages. When voltages are low raising generator voltages in unison will increase system voltages.
Which of the following would be techniques in managing an approaching System Operating Limit violation or IROL violation? Replace transmission lines Removing overloaded transmission facilities Reduce power flow by denying market activity Re-dispatch, Reduce Interchange or Load Shed
Re-dispatch, Reduce Interchange or Load Shed. An analysis results in an awareness of an approaching System Operating Limit Violation. To mitigate the situation powerflow must be reduced on the transmission element, the best options are re-dispatch, reduce interchange or shedding load if urgent.
In a power system, which type of power provides indication of voltage problems, is critical for support of heavily loaded transmission lines, and is necessary to have sufficient dynamic reserves in preparation for a contingency? Solar Power Reactive Power Real Power Apparent Power
Reactive Power. VAR-001: Several of the Requirements in this standard pertain to maintaining sufficient reactive resources.
A radial transmission line feeding a load is overloaded. The Transmission Operator must do which of the following to unload the line? Raise interchange schedule Re-dispatch generation Shed load at the end of the line Lower interchange schedule
Shed load at the end of the line. The word radial in this question is key. Shedding load is the only possible action to reduce loading on the line.
