1 Reliability Guideline - nerc.com Guideline... · 1 2 Reliability Guideline: 3 Generating Unit Operations During Complete Loss of Communications 4 5 Preamble: 6 7 It is in the public

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Reliability Guideline: 2

Generating Unit Operations During Complete Loss of Communications 3

4 Preamble: 5 6 It is in the public interest for the North American Electric Reliability Corporation (NERC) to develop 7 guidelines that are useful for maintaining or enhancing the reliability of the Bulk Electric System (BES). The 8 Technical Committees of NERC; Operating Committee (OC), Planning Committee (PC) and the Critical 9 Infrastructure Protection Committee (CIPC) per their charters are authorized by the NERC Board of Trustees 10 (Board) to develop Reliability (OC and PC) and Security Guidelines (CIPC). These guidelines establish a 11 voluntary code of practice on a particular topic for consideration and use by BES users, owners, and 12 operators. These guidelines are coordinated by the technical committees and include the collective 13 experience, expertise and judgment of the industry. The objective of this reliability guideline is to distribute 14 key practices and information on specific issues critical to maintaining the highest levels of BES reliability. 15 Reliability guidelines are not to be used to provide binding norms or create parameters by which compliance 16 to standards is monitored or enforced. While the incorporation of guideline practices are strictly voluntary, 17 reviewing, revising, or developing a program using these practices is highly encouraged to promote and 18 achieve the highest levels of reliability for the BES. 19 20 Purpose: 21 22 This Reliability Guideline provides a strategy for power plant operations in the case of complete loss of 23 communications (both data and voice) between on-site generating unit(s) operator and the System 24 Operator for the Balancing Area, Transmission Operator and Reliability Coordinator. 25 26 This Reliability Guideline was developed as requested by the NERC OC as part of our industry’s response to 27 the Severe Impact Resilience Task Force (SIRTF) Recommendations. 28 29 The Reliability Guideline applies primarily to Balancing Authorities and to Generator Operators. The 30 applicability of this document to Balancing Authorities is to provide a resource for coordination and training 31 guidelines for generators operators should all communications be interrupted, particularly during a severe 32 impact event. See Appendix (Training) below. 33 34 The Reliability Guideline outlines a coordinated operations strategy for generating units to stabilize system 35 frequency when centralized guidance is not possible. It is designed to keep frequency within allowable 36 limits and continued safe operation of generators while maintaining acceptable frequency control. 37 38 The Reliability Guideline is not meant to prevent generating unit operators from taking actions necessary 39 to protect the equipment under their supervision from permanent damage. Protective equipment should 40 not be bypassed or rendered inoperable in order to follow this guide. Safety of personnel and prevention 41 of permanent damage to system equipment are the first responsibilities of electric system operators at all 42

http://www.nerc.com/comm/OC/Pages/SIRTF/Severe-Impact-Resilience-Task-Force.aspx

Reliability Guideline: Generating Unit Operations During Complete Loss of Communications 2

levels. Short term instabilities and power grid outages can only be made worse if permanent damage is 1 allowed to occur to system equipment. 2 3 Assumptions: 4 5 The basic assumptions made in the development of this guide are as follows: 6

A. Loss of Communications – all data and voice communications, both primary and backup, are lost 7 between the on-site generating unit(s) operator and the System Operator for the Balancing Area, 8 Transmission Operator and Reliability Coordinator. 9

B. Generating Unit Status – some generating capacity remains in service or can be brought into service 10 locally at the plant operator’s discretion, to serve the load over the period of lost communications. 11 (This does not imply that steam units not already in service should be brought into service.) 12

C. Instrumentation – Generating units are equipped with frequency metering devices capable of 13 displaying (and optionally recording) system frequency on both narrow (roughly 59.95 Hz to 60.05 14 Hz) and wide (roughly 58.0 Hz to 62.0 Hz) ranges. Alternatively, nomograms or other job aids that 15 convert generator speed to frequency can be used. 16

D. Situation Awareness – The on-site generating unit(s) operator recognize that frequency is abnormal 17 and a unique situation is occurring. 18

19 Guideline Details: 20 21 If communications between the on-site generating unit(s) operator and the System Operator is lost, the primary 22 system information available to the on-site generating unit(s) operator will be frequency as measured locally by 23 plant instrumentation. It may not be possible for the on-site generating unit(s) operator to determine if the grid 24 remains intact or if the plant is operating as part of a local island. There may be clues that a disturbance has 25 occurred. Still, any constant frequency operations strategy must function equally well with an intact grid or 26 under island conditions. 27 28 In order to maintain stable system operations with either an intact grid or as part of an island, it is necessary to 29 maneuver generation output to match changes in system demand. Without communications from the System 30 Operator, this can only be done by the on-site generating unit(s) operator controlling to frequency. This guide 31 proposes the following structure to achieve frequency control for the following Interconnections: 32 33

Eastern Interconnection 34

35 Deadband (Green Zone) – as long as frequency stays reasonably close to 60.00 Hz, no control actions should 36 be taken by generating units. This deadband should be +/- 50 milliHertz (59.95 Hz to 60.05 Hz - See Chart 37 1 below). 38 39 Selective Response (Yellow Zone) – as frequency moves outside the deadband boundaries but remains 40 within reasonable operational limits it should be corrected by maneuvering generating units in a gradual 41 manner. For the Eastern Interconnection, the Selective Response band should be beyond +/- 50 milliHertz 42


but less than +/- 200 milliHertz (59.80 Hz to 60.20 Hz). The generation ramp rate recommended for 1 Selective Response is roughly one percent of the unit rating per minute. On-site generating unit(s) operator 2 should carefully observe frequency during Selective Response and cease maneuvering their units when 3 frequency enters the deadband. It should be noted that a sustained frequency less than 59.90 Hz or greater 4 than 60.10 Hz in the Eastern Interconnection is an indication that a disturbance has occurred. 5 6 Full Response (Red Zone) – when frequency exceeds reasonable operational limits all units capable of 7 responding should rapidly maneuver to balance load with generation. Full Response should be triggered 8 when frequency is less than 59.80 Hz or greater than 60.20 Hz. If frequency continues to exceed the Full 9 Response limits, all available generation at the plant should be maneuvered to the appropriate unit 10 operating limits (i.e. fully loaded in the case of low frequency or at minimum load in the case of high 11 frequency). In particular, all available generating capacity at the plant should be deployed to halt frequency 12 decline when the frequency drops below the Full Response limit. On-site generating unit(s) operator should 13 carefully observe frequency during Full Response operation and reduce the ramp rate of their units when 14 frequency reaches the Selective Response region. 15 16 Emergency Response – if frequency continues to deteriorate, then emergency measures will be required. 17

High Frequency – high frequency Emergency Response will consist of maneuvering all available 18 generation to its lowest stable operating point, followed by tripping of selected units. 19

Low Minimums – all generation should be maneuvered to its lowest stable minimum load 20 operating point (with auxiliary fuel firing, if required) when frequency increases to 60.30 Hz. 21

Unit Tripping – when frequency increases to 60.50 Hz, plants with multiple units should trip 22 generation offline. Generally, smaller units with minimal impacts to transmission should be 23 taken offline first, so that as much capacity as possible remains online. Use operational 24 judgment to minimize any adverse impacts. Subsequent generation should be taken offline as 25 needed. 26

Low Frequency – Emergency Response will consist of loading all available hydro generation, 27 followed by commitment of quick start generating units (primarily combustion turbines) and, finally, 28 under frequency load shedding. 29

Hydro – all hydro generation should be loaded when frequency declines to 59.70 Hz 30

Quick Start – all quick start generation resources should be committed when frequency drops 31 below 59.60 Hz 32

33 For information, under frequency load shed relays start to operate automatically when frequency declines 34 to 59.50 Hz. Roughly ten percent of system load is typically shed at this point (note that specific frequencies 35 and load percentages vary depending upon specific regional requirements). Additional load is typically shed 36 as frequency continues to decline. The amount of load actually shed in any particular island will vary. 37 38 Blackout Conditions – if conditions continue to deteriorate, it will be necessary for on-site generating unit(s) 39 operator to separate from the synchronized grid in order to protect generating unit equipment. This 40


typically takes place at roughly 58.00 Hz. (Note that this is based on turbine manufacturer’s 1 recommendations that operation below this frequency can result in significant fatigue failure of the turbine 2 blades and may vary with specific turbine design). 3 4 While it is desirable to maintain service continuity, it is unacceptable to allow generating unit equipment to 5 suffer major damage that would impede the restoration of service after a major disturbance. However, it 6 is important that units not be prematurely tripped when frequency is declining, since such action will cause 7 system frequency to decline further and adversely affect other generators in the island. It is recommended 8 that unless frequency is declining rapidly, units should remain connected to the system until the operation 9 of automatic under frequency load shedding relays is completed at roughly 58.00 Hz. 10 11 If possible, a unit removed from the transmission system by the on-site generating unit(s) operator should 12 continue operation on a self-supporting basis carrying its own station service. Such Operation should be 13 continued until a request to re-synchronize the generating unit to the transmission system can be 14 communicated to and approved by the System Operator. Maintaining generating units in hot standby mode 15 will reduce the time required to restore the electrical system to normal operation. 16 17 The on-site generating unit(s) operator should make regular attempts to reestablish communications with 18 the System Operator to convey the status of their generating units and always follow their Black Start Plans. 19 This should include attempts to contact the Balancing Authority, Transmission Operator and/or Reliability 20 Coordinator. 21


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Chart 1 – Eastern Interconnection Generator Frequency Operating Guide 2 3 Notes: 4

1. Nuclear generating plants are expected to stay on line at a sustainable, stable output level as long 5 as possible. Under no circumstances should this Reliability Guideline be interpreted as requiring 6 nuclear generating plants to operate in a manner that will violate their regulatory requirements, 7 endanger public safety or adversely impact the integrity of plant equipment. 8

2. It is recommended that generating units calibrate plant frequency equipment on an annual basis. 9 10


ERCOT Interconnection 1

2 Deadband (Green Zone) – as long as frequency stays reasonably close to 60.00 Hz, no control actions should 3 be taken by generating units. This deadband should be +/- 70 milliHertz (59.93 Hz to 60.07 Hz - See Chart 4 2 below). This dead-band is the “Secondary Control” dead-band and should not be confused with governor 5 dead-band of the turbine governor. Turbine governor dead-bands are as required by ERCOT. 6 7 Selective Response (Yellow Zone) – as frequency moves outside the dead-band boundaries but remains 8 within reasonable operational limits it should be corrected by maneuvering generating units in a gradual 9 manner. For the ERCOT Interconnection, the Selective Response band should be +/- 200 milliHertz (59.80 10 Hz to 60.20 Hz). The generation ramp rate recommended for Selective Response is roughly one percent of 11 the unit rating per minute. On-site generating unit(s) operator should carefully observe frequency during 12 Selective Response and cease maneuvering their units when frequency enters the dead-band. 13 14 Full Response (Red Zone) – when frequency exceeds reasonable operational limits all units capable of 15 responding should rapidly maneuver to balance load with generation. Full Response should be triggered 16 when frequency is less than 59.80 Hz or greater than 60.20 Hz. If frequency continues to exceed the Full 17 Response limits, all available generation at the plant should be maneuvered to the appropriate unit 18 operating limits (i.e. fully loaded in the case of low frequency or at minimum load in the case of high 19 frequency). In particular, all available generating capacity at the plant should be deployed to halt frequency 20 decline when the frequency drops below the Full Response limit. On-site generating unit(s) operator s 21 should carefully observe frequency during Full Response operation and reduce the ramp rate of their units 22 when frequency reaches the Selective Response region. 23 24 Emergency Response – if frequency continues to deteriorate, then emergency measures will be required. 25



Unit Tripping – when frequency increases to 62.50 Hz, plants with multiple units should trip 30 generation offline. Generally, smaller units with minimal impacts to transmission should be 31 taken offline first, so that as much capacity as possible remains online. Use operational 32 judgment to minimize any adverse impacts. Subsequent generation should be taken offline as 33 needed. Note that turbine overspeed trips typically engage at 63.00 Hz with auxiliary governor 34 action beginning at 61.80 Hz. 35

Low Frequency – Emergency Response will consist of loading all available hydro generation, 36 followed by commitment of quick start generating units (primarily combustion turbines) and, finally, 37 under frequency load shedding. 38

Hydro – all hydro generation should be loaded when frequency decreases to 59.50 Hz 39


Quick Start – all quick start generation resources should be committed when frequency drops 1 below 59.50 Hz. 2

3 For information, under frequency load shed relays start to operate automatically when frequency declines 4 to 59.30 Hz roughly five percent of system load is typically shed at this point. An additional 10% of system 5 load is shed if frequency continues to decline and declines to 58.90 Hz with a final system load shedding of 6 10 percent when frequency declines to 58.50 Hz. The amount of load actually shed in any particular island 7 will vary. 8 9 Blackout Conditions – if conditions continue to deteriorate, it will be necessary for on-site generating unit(s) 10 operators to separate from the synchronized grid in order to protect generating unit equipment. This 11 typically takes place at roughly 58.00 Hz. (Note that this is based on turbine manufacturer’s 12 recommendations that operation below this frequency can result in significant fatigue failure of the turbine 13 blades and may vary with specific turbine design). 14 15 While it is desirable to maintain service continuity, it is unacceptable to allow generating unit equipment to 16 suffer major damage that would impede the restoration of service after a major disturbance. However, it 17 is important that units not be prematurely tripped when frequency is declining, since such action will cause 18 system frequency to decline further. It is recommended that unless frequency is declining rapidly, units 19 should remain connected to the system until the operation of automatic under frequency load shedding 20 relays is completed at roughly 58.40 Hz. Off frequency operations of steam turbines should be limited to 9 21 minutes below 59.40 Hz. Thirty seconds below 58.40 Hz and two seconds below 58.00 Hz. 22 23 If possible, a unit removed from the transmission system by the on-site generating unit(s) operator should 24 continue operation on a self-supporting basis carrying its own station service. Such operation should be 25 continued until a request to re-synchronize the generating unit to the transmission system can be 26 communicated to and approved by the System Operator. Maintaining generating units in hot standby mode 27 will reduce the time required to restore the electrical system to normal operation. 28 29 On-site generating unit(s) operator should make regular attempts to reestablish communications with the 30 System Operator to convey the status of their generating units and always follow their Black Start Plans. 31 This should include attempts to contact the Balancing Authority, Transmission Operator and/or Reliability 32 Coordinator. 33 34


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Chart 2 – ERCOT Interconnection Generator Frequency Operating Guide 3 4 Notes: 5

1. Nuclear generating plants are expected to stay on line at a sustainable, stable output level as long 6 as possible. Under no circumstances should this Reliability Guideline be interpreted as requiring 7 nuclear generating plants to operate in a manner that will violate their regulatory requirements, 8 endanger public safety or adversely impact the integrity of plant equipment. 9



Western Interconnection 1

2 Deadband (Green Zone) – as long as frequency stays reasonably close to 60.00 Hz, no control actions should 3 be taken by generating units. This deadband should be +/- 50 milliHertz (59.95 Hz to 60.05 Hz- See Chart 3 4 below). This deadband is the “Secondary Control” deadband and should not be confused with governor 5 deadband of the turbine governor. 6 7 Selective Response (Yellow Zone) – as frequency moves outside the deadband boundaries but remains 8 within reasonable operational limits it should be corrected by maneuvering generating units in a gradual 9 manner. For the Western Interconnection, the Selective Response band should be +/- 200 milliHertz (59.80 10 Hz to 60.20 Hz). The generation ramp rate recommended for Selective Response is roughly one percent of 11 the unit rating per minute. On-site generating unit(s) operator should carefully observe frequency during 12 Selective Response and cease maneuvering their units when frequency enters the deadband. 13 14 Full Response (Red Zone) – when frequency exceeds reasonable operational limits all units capable of 15 responding should rapidly maneuver to balance load with generation. Full Response should be triggered 16 when frequency is less than 59.80 Hz or greater than 60.20 Hz. If frequency continues to exceed the Full 17 Response limits, all available generation at the plant should be maneuvered to the appropriate unit 18 operating limits (i.e. fully loaded in the case of low frequency or at minimum load in the case of high 19 frequency). In particular, all available generating capacity at the plant should be deployed to halt frequency 20 decline when the frequency drops below the Full Response limit. On-site generating unit(s) operator should 21 carefully observe frequency during Full Response operation and reduce the ramp rate of their units when 22 frequency reaches the Selective Response region. 23 24 Emergency Response – if frequency continues to deteriorate, then emergency measures will be required. 25



Unit Tripping – when frequency increases to 60.60 Hz, plants with multiple units should trip 30 generation offline. Generally, smaller units with minimal impacts to transmission should be 31 taken offline first, so that as much capacity as possible remains online. Use operational 32 judgment to minimize any adverse impacts. Subsequent generation should be taken offline as 33 needed. Note that turbine overspeed trips typically engage at 61.20 Hz. 34

Low Frequency – Emergency Response will consist of loading all available hydro and pumped 35 storage hydro generation, followed by commitment of quick start generating units (primarily 36 combustion turbines) and, finally, under frequency load shedding. 37

Hydro – all hydro and pumped storage hydro generation should be loaded when frequency 38 declines to 59.70 Hz. 39



3 For information, under frequency load shed relays start to operate automatically when frequency reaches 4 59.50 Hz. Roughly 4,200 MW of system load is shed at this point (note that specific frequencies and load 5 percentages vary depending upon specific regional requirements). Additional load is shed as frequency 6 continues to decline. The amount of load actually shed in any particular island is per the May 24, 2011 7 WECC Off-Nominal Frequency Load Shedding Plan. 8 9 It is preferred that online generators that protect for off-nominal frequency operation should have relaying 10 protection that accommodates, at a minimum, underfrequency and overfrequency operation for the time 11 frames specified in the following table: 12 13 Underfrequency Limit Overfrequency Limit Minimum TimeNOTE 1 14 15

>59.4 Hz < 60.6 Hz N/A (continuous operation) 16 ≤59.4 Hz ≥60.6 Hz 3 minutes 17 ≤58.4 Hz ≥61.6 Hz 30 seconds 18 ≤57.8 Hz 7.5 seconds 19 ≤57.3 Hz 45 cycles 20 ≤57.0 Hz ≥61.7 Hz Instantaneous trip 21 22

Note 1: Minimum Time is the time the generator should stay interconnected and producing power. 23 24 Blackout Conditions – if conditions continue to deteriorate, it will be necessary for the on-site generating 25 unit(s) operator to separate from the synchronized grid in order to protect generating unit equipment. This 26 typically takes place at roughly <58.00 Hz. (Note that this is based on turbine manufacturer’s 27 recommendations that operation below this frequency can result in significant fatigue failure of the turbine 28 blades and may vary with specific turbine design). 29 30 While it is desirable to maintain service continuity, it is unacceptable to allow generating unit equipment to 31 suffer major damage that would impede the restoration of service after a major disturbance. However, it 32 is important that units not be prematurely tripped when frequency is declining, since such action will cause 33 system frequency to decline further. It is recommended that unless frequency is declining rapidly, units 34 should remain connected to the system until the operation of automatic under frequency load shedding 35 relays is completed at roughly 58.30 Hz. 36 37 If possible, a unit removed from the transmission system by the on-site generating unit(s) operator should 38 continue operation on a self-supporting basis carrying its own station service. Such operation should be 39 continued until a request to re-synchronize the generating unit to the transmission system can be 40 communicated to and approved by the System Operator. Maintaining generating units in hot standby mode 41 will reduce the time required to restore the electrical system to normal operation. 42 43


On-site generating unit(s) operator should make regular attempts to reestablish communications with the 1 System Operator to convey the status of their generating units and always follow their Black Start Plans as 2 necessary. This should include attempts to contact the Balancing Authority, Transmission Operator and/or 3 Reliability Coordinator. 4 5

6

Chart 3 – Western Interconnection Generator Frequency Operating Guide 7 8 Notes: 9

1. Nuclear generating plants are expected to stay on line at a sustainable, stable output level as long as possible. 10 Under no circumstances should this Reliability Guideline be interpreted as requiring nuclear generating plants 11 to operate in a manner that will violate their regulatory requirements, endanger public safety or adversely 12 impact the integrity of plant equipment. 13

2. It is recommended that generating units calibrate plant frequency equipment on an annual basis. 14

15


Quebec Interconnection 1

2 Deadband (Green Zone) – as long as frequency stays reasonably close to 60.00 Hz, no control actions should 3 be taken by generating units. This deadband should be +/- 50 milliHertz (59.95 Hz to 60.05 Hz - See Chart 4 4 below). 5 6 Selective Response (Yellow Zone) – as frequency moves outside the deadband boundaries but remains 7 within reasonable operational limits it should be corrected by maneuvering generating units in a gradual 8 manner. For the Quebec Interconnection, the Selective Response band should be +/- 300 milliHertz (59.70 9 Hz to 60.3 Hz). The generation ramp rate recommended for Selective Response is roughly one percent of 10 the unit rating per minute. On-site generating unit(s) operator should carefully observe frequency during 11 Selective Response and cease maneuvering their units when frequency enters the deadband. 12 13 Full Response (Red Zone) – when frequency exceeds reasonable operational limits all units capable of 14 responding should rapidly maneuver to balance load with generation. Full Response should be triggered 15 when frequency is less than 59.70 Hz or greater than 60.30 Hz. If frequency continues to exceed the Full 16 Response limits, all available generation at the plant should be maneuvered to the appropriate unit 17 operating limits (i.e. fully loaded in the case of low frequency or at minimum load in the case of high 18 frequency). In particular, all available generating capacity at the plant should be deployed to halt frequency 19 decline when the frequency drops below the Full Response limit. On-site generating unit(s) operator should 20 carefully observe frequency during Full Response operation and reduce the ramp rate of their units when 21 frequency reaches the Selective Response region. 22 23 Emergency Response – if frequency continues to deteriorate, then emergency measures will be required. 24 25


Low Minimums – all variable hydro generation should be maneuvered to its lowest stable 28 minimum load operating point when increase to 60.30 Hz. 29

Unit Tripping – when frequency increases to 60.50 Hz, plants with multiple units should trip 30 generation offline. Variable hydro generation should be taken offline first and run-off-the-river 31 units second. Use operational judgment to minimize any adverse impacts and to adequately 32 manage hydraulic resource. Subsequent generation should be taken offline as needed. Note 33 that over frequency generation tripping engages roughly at 60.5 Hz. 34

Low Frequency –Emergency Response will consist of loading all available hydro and pumped storage 35 hydro generation, followed by commitment of quick start generating units (primarily combustion 36 turbines) and, finally, under frequency load shedding. 37

Variable Hydro – all variable hydro generation should be loaded when frequency declines to 38 59.70 Hz. 39



Run-of-the-river Hydro – all run of the river hydro generation should be loaded at maximum 3 when frequency drops below 59.60 Hz. 4

5 For information, under frequency load shed relays start to operate automatically when frequency reaches 6 59.00 Hz. Roughly, 500 MW of load is typically shed at this point (based on peak load conditions). An 7 additional 800 MW of load is typically shed as frequency continues to decline by 500 millihertz thresholds 8 until it reaches the last step at 57.00 Hz. 9

10 Blackout Conditions – if conditions continue to deteriorate, it will be necessary for the on-site generating 11 unit(s) operator to separate from the synchronized grid in order to protect generating unit equipment. 12 13 While it is desirable to maintain service continuity, it is unacceptable to allow generating unit equipment to 14 suffer major damage that would impede the restoration of service after a major disturbance. However, it 15 is important that units not be prematurely tripped when frequency is declining, since such action will cause 16 system frequency to decline further. It is recommended that unless frequency is declining rapidly, units 17 should remain connected to the system until the operation of automatic under frequency load shedding 18 relays is completed at roughly 57.00 Hz. 19 20 If possible, a unit removed from the transmission system by the on-site generating unit(s) operator should 21 continue operation on a self-supporting basis carrying its own station service. Such operation should be 22 continued until a request to re-synchronize the generating unit to the transmission system can be 23 communicated to and approved by the System Operator. 24 25 On-site generating unit(s) operator should make regular attempts to reestablish communications with the 26 System Operator to convey the status of their generating units and always follow their Black Start Plans as 27 necessary. This should include attempts to contact the Balancing Authority, Transmission Operator and/or 28 Reliability Coordinator. 29 30


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Chart 4 – Quebec Interconnection Generator Frequency Operating Guide 2 3 Notes 4


Related Documents and Links: 7 EPRI Power System Dynamics Tutorial 8 9 Revision History: 10

Date

Version Number

Reason/Comments

11/19/2013

1.0

Initial Version – “Generating Unit Operations During Complete Loss of Communications”

11 12

http://www.epri.com/abstracts/Pages/ProductAbstract.aspx?ProductId=000000000001016042


Appendix (Training) 1 2 Introduction - This appendix outlines suggested additional reading as well as provides a set of tasks the on-3 site generating unit(s) operator could consider as part of ongoing training and for participation in area 4 restoration drills and seminars. On-site generator unit(s) operators are encouraged to consult with their 5 Balancing Authority in reference to this guideline and training. 6 7 Send comments and suggestions to [email protected]. 8 9 Additional Reading - A valuable resource available for training is the EPRI Power System Dynamics Tutorial. 10 The tutorial can be downloaded for free at the link above. The parts of the tutorial that deal most directly 11 to frequency control are: 12

Section 4 13

Section 8 14

Section 11.3 15 16 Scenario - The tasks that follow are suggested as part of initial “emergency” training for the on-site 17 generating unit(s) operator as well as refresher training during restoration drills. The tasks were developed 18 after reviewing a few actual scenarios where generators found themselves in an island following a 19 disturbance. While communications were still available to the Balancing Authority, the scenario still 20 demonstrates the dynamics that can be observed following a disturbance. Since the most likely situation 21 where an on-site generating unit(s) operator would need to take action and not have communications is 22 following a disturbance or coordinated attack, the situation below is valid for comparison. 23 24

25 26

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The frequency graph from a storm-created island in 2010 shows what took place within about 30 seconds. 1 The storm left approximately 55 MWs of load in the area connected to 45 MWs of generation. This caused 2 frequency to decline to 59Hz, which was the first step of under frequency load shedding (UFLS) in this area. 3 The UFLS caused frequency to overshoot to approximately 61.5Hz. Unfortunately, 18 MW of hydro 4 generation tripped automatically at 61.5 Hz. This left an insufficient amount of generation in the area that 5 caused a more rapid decline in frequency, which the next step of UFLS was unable to arrest. 6 7 The reality is that in some cases as outlined above, there is little for the on-site generating unit(s) operator 8 to do. Knowing and coordinating the UFLS and generator trip setpoints in the area can help generators ride 9 through local disturbances. For islands caused by major events, the islands will be larger and changes in 10 frequency will be slower. The tasks below are intended to help the on-site generating unit(s) operator 11 prepare for such events. It is suggested the tasks should be reviewed annually. 12 13 Tasks 14

Discuss training activities and the guideline with your Balancing Authority. 15

Identify your local Load Serving Entity’s Under-Frequency Load Shedding trip points. 16

Identify your generator(s) over-frequency trip settings. 17

Identify and test your generator’(s) most frequency responsive control modes. 18

Identify the ratings of the transmission lines emanating from your station and the plant limitations 19 if one or more lines are out of service. 20

List and discuss the symptoms of possible islanding. 21

Identify and test possible alternate communication paths with your Balancing Authority, 22 Transmission Operator and Reliability Coordinator (to include communications through other 23 entities). 24

If at a multi-unit station, discuss the frequency control strategy to be followed during islanding, 25 restoration or total loss of communications. 26

Walk through the steps needed to isolate a generator from the grid while supplying its own 27 auxiliaries. 28