Responding to post contingency overloads, IROL’s and SOL’s Art Gardiner – CPS Energy Steve Rainwater - LCRA 1

Introduction Responding to post contingency overloads is intended to describe the options you have in response to a overload and identify and apply those options. 2

Objectives At the completion of this course of instruction you will: Identify the different type of plans used to relieve pre and post contingency overloads. Identify who has the authority to implement real time actions to ensure the stable and reliable operation of the bulk electric system? Identify the options to relieve a post contingency overload, IROL, or SOL. Identify when to use switching to relieve a post contingency overload Identify when to re dispatch generation to relieve a post contingency overload Identify when to shed load to relieve a post contingency overload 3

What are the 4 different type of plans used to relieve pre and post contingency overloads? a) TOAP, IROL, CPAP, SOL, AND MIS b) TOAP, PCAP, RAP, AND MP c) SOL, IROL, CPAP, AND PM d) NONE OF THE ABOVE Answer- B) TOAP, PCAP, RAP, AND MP Responding to post contingency overloads, IROL’s and SOL’s 4

Definitions- Ratings 1 2 Conductor/Transformer 2-Hour Rating The two-hour MVA rating of the conductor or transformer only, excluding substation terminal equipment in series with a conductor or transformer, at the applicable ambient temperature. The conductor or transformer can operate at this rating for two hours without violation of National Electrical Safety Code (NESC) clearances or equipment failure. Emergency Rating The two-hour MVA rating of a Transmission Element, including substation terminal equipment in series with a conductor or transformer, at the applicable ambient temperature. The Transmission Element can operate at this rating for two hours without violation of NESC clearances or equipment failure. 5

Definitions- Ratings 3 15-Minute Rating The 15-minute MVA rating of a Transmission Element, including substation terminal equipment in series with a conductor or transformer, at the applicable ambient temperature and with a step increase from a prior loading up to 90% of the Normal Rating. The Transmission Element can operate at this rating for 15 minutes, assuming its pre-contingency loading up to 90% of the Normal Rating limit at the applicable ambient temperature, without violation of NESC clearances or equipment failure. This rating takes advantage of the time delay associated with heating of a conductor or transformer following a sudden increase in current. 6

Definitions- Ratings 4 7 Normal Rating The continuous MVA rating of a Transmission Element, including substation terminal equipment in series with a conductor or transformer, at the applicable ambient temperature. The Transmission Element can operate at this rating indefinitely without damage, or violation of NESC clearances.

Definitions-CMP 5 Constraint Management Plan (CMP) A set of pre-defined actions executed in response to system conditions to prevent or to resolve one or more thermal or non- thermal transmission security violations or to optimize transmission. CMPs may be developed in cases where studies indicate economic dispatch alone may be unable to resolve a transmission security violation or in response to Real-Time conditions where SCED is unable to resolve a transmission security violation. ERCOT will employ CMPs to facilitate the market use of the ERCOT Transmission Grid while maintaining system security and reliability in accordance with the Protocols and NERC Reliability Standards. CMPs are intended to supplement, not to replace, the use of SCED for prevention or resolution of one or more thermal or non-thermal transmission security violations. CMPs include, but are not limited to the following: 8

Definitions- CMP 6 Mitigation Plan A set of pre-defined actions to execute post- contingency to address voltage issues or reduce overloading on one or more given, monitored Transmission Facilities to below their Emergency Rating with restoration of normal operating conditions within two hours. A Mitigation Plan must be implementable and may include transmission switching and Load shedding. Mitigation Plans shall not be used to manage constraints in SCED by either activating them or deactivating them. 9

Nodal Operating Guides Mitigation Plan (1)Mitigation Plans are defined in Protocol Section 2.1, Definitions, and shall not be used to manage constraints in Security-Constrained Economic Dispatch (SCED) by either activating them or deactivating them. Normally, it is desirable that a Transmission Service Provider (TSP) constructs Transmission Facilities adequate to eliminate the need for a Mitigation Plan; however, in some circumstances, such construction may be unachievable in the available time frame. (2)A Mitigation Plan may be proposed by any TSP, but must be approved by ERCOT and the impacted Transmission Operator (TO) prior to implementation. Mitigation Plans must: (a)Be coordinated with the TOs included in the Mitigation Plan; (b)Limited in use to the time required to construct replacement Transmission Facilities; however, the Mitigation Plan will remain in effect if ERCOT has determined the replacement Transmission Facilities to be impractical; (c)Comply with all requirements of the Protocols and applicable North American Electric Reliability Corporation (NERC) Reliability Standards;.

Nodal Operating Guides Mitigation Plan (d)Clearly define and document TO actions; (e)Be executed by TOs; (f)Be able to be implemented in a timeframe that will not result in loss of the overloaded Transmission Facility; (g)Identify the most limiting protective relay setting beyond the 15-Minute Rating when developing the Mitigation Plan in advance or as soon as practicable when developing the Mitigation Plan in Real-Time; and (h)Not subject ERCOT to unacceptable risk of widespread cascading Outages. (3)An approved Mitigation Plan may be executed immediately, post-contingency, by the TO without instruction by ERCOT or shall be executed upon direction by ERCOT. (4)Restoration of any Load shed by executing the Mitigation Plan shall be coordinated with ERCOT..

Definitions 7 Pre-Contingency Action Plan (PCAP) A set of pre-defined actions to execute pre- contingency to address voltage issues or reduce overloading on one or more given, monitored Transmission Facilities to below their Emergency Rating with restoration of normal operating conditions within two hours. A PCAP may include transmission switching and does not include Load shedding. A PCAP may also be implemented for the duration of an Outage and shall be included in the Outage Scheduler as soon as practicable. 12

Nodal Operating Guides Pre-Contingency Action Plans (1)Pre-Contingency Action Plans (PCAPs) are defined in Protocol Section 2.1, Definitions, and are implemented in anticipation of a contingency. Normally, it is desirable that a Transmission Service Provider (TSP) construct Transmission Facilities adequate to eliminate the need for any PCAP; however, in some circumstances, such construction may be unachievable in the available time frame. (2)A PCAP may be proposed by any Market Participant, but must be approved by ERCOT and the impacted Transmission Operator (TO) prior to implementation. PCAPs must: (a)Be coordinated with the TOs included in the PCAP; (b)Be limited in use to the time required to construct replacement Transmission Facilities and until such Facilities are placed in-service, or the PCAP is no longer needed; however, the PCAP will remain in effect if ERCOT has determined the replacement Transmission Facilities to be impractical;.

Nodal Operating Guides Pre-Contingency Action Plans (c)Comply with all requirements of the Protocols and applicable North American Electric Reliability Corporation (NERC) Reliability Standards; (d)Clearly define and document TO actions; (e)Be executed by TOs; and (f)Not include Load shed. (3)An approved PCAP may be executed immediately prior to a contingency by the TO without instruction by ERCOT, or shall be executed upon direction by ERCOT. (4)All proposed, approved, amended, and removed PCAPs shall be managed in accordance with paragraph (4) of Section 11.1, Introduction. (5)ERCOT may limit the quantity of PCAPs that are used..

Definitions 8 15 Remedial Action Plan (RAP) A set of pre-defined actions to execute post-contingency to address voltage issues or in order to reduce loading on one or more given, monitored Transmission Facilities to below their Emergency Rating within 15 minutes. RAPs are sufficiently dependable to assume they can be executed without loss of reliability to the interconnected network, with restoration of normal operating conditions and below Normal Rating within two hours as defined in the Network Operations Model. RAPs may be relied upon in allowing additional use of the transmission system in SCED. RAPs may not include Load shedding.

Nodal Operating Guides Remedial Action Plan (1)Remedial Action Plans (RAPs) are defined in Protocol Section 2.1, Definitions and may be relied upon in allowing additional use of the transmission system in SCED. Normally, it is desirable that a Transmission Service Provider (TSP) constructs Transmission Facilities adequate to eliminate the need for any RAP; however, in some circumstances, such construction may be unachievable in the available time frame. (2)RAPs must: (a)Be coordinated by ERCOT with all Transmission Operators (TOs) and Resource Entities included in the RAP, and approved by ERCOT; (b)Be llimited to the time required to construct replacement Transmission Facilities; however, the RAP will remain in effect if ERCOT has determined the replacement Transmission Facilities to be impractical; (c)Comply with all applicable requirements in the Protocols and applicable North American Electric Reliability Corporation (NERC) Reliability Standards; (d)Clearly define and document TOs and Resource Entities included in the RAP actions; (e)Must be able to resolve the issue for which it was designed over the range of conditions that might reasonably be experienced; (f)Be executed by the TOs and/or Resource Entities;.

Nodal Operating Guides Remedial Action Plan (g)Have a 15-minute Rating greater than the Normal and Emergency Ratings for the Transmission Facilities it intends to resolve; (h)Be defined in the Network Operations Model and considered in the Security-Constrained Economic Dispatch (SCED) and Reliability Unit Commitment (RUC). RAPs that cannot be modeled using ERCOT’s existing infrastructure shall be rejected unless the Technical Advisory Committee (TAC) approves a plan to work around the infrastructure problem; and (i)Not include Load shed.. (3)An approved RAP may be executed immediately after a contingency by the TOs and Resource Entities included in the RAP without instruction by ERCOT or shall be executed upon direction by ERCOT. (4)ERCOT shall conduct a review of each existing RAP annually or as required by changes in system conditions to ensure its continued effectiveness. Each review shall proceed according to a process and timetable documented in ERCOT Procedures. (5)ERCOT may approve the expiration of a RAP after consultation with the TOs and Resource Entities included in the RAP. ERCOT shall modify its reliability constraints to recognize the unavailability of the RAP.

Definitions 9 18 Temporary Outage Action Plan (TOAP) A temporary set of pre-defined actions to execute post- contingency, during a specified Transmission Facility or Resource Outage, in order to address voltage issues or reduce overloading on one or more given, monitored Transmission Facilities to below their Emergency Rating with restoration of normal operating conditions within two hours. A TOAP must be implementable and may include transmission switching and/or Load shedding. TOAPs shall not be used to manage constraints in SCED by either activating them or deactivating them.

Nodal Operating Guides Temporary Outage Action Plan (1)Temporary Outage Action Plans (TOAPs) are defined in Protocol Section 2.1, Definitions, and shall not be used to manage constraints in Security-Constrained Economic Dispatch (SCED) by either activating them or deactivating them. (2)A TOAP may be proposed by any Market Participant. TOAPs shall be approved by ERCOT prior to implementation. TOAPs must: (a)Be coordinated with the Transmission Operators (TOs) included in the TOAP; (b)Limit use to the duration of a specific Transmission Facility or Resource Outage; (c)Comply with all requirements of the Protocols and applicable North American Electric Reliability Corporation (NERC) Reliability Standards; (d)Clearly define and document TO actions; (e)Be executed by TOs;

Nodal Operating Guides Temporary Outage Action Plan (f)Be implemented in a timeframe that will not result in loss of the overloaded Transmission Facility; (g)Identify the most limiting protective relay setting beyond the 15-Minute Rating when developing the TOAP in advance or as soon as practicable when developing the TOAP in Real-Time; and (h)Not subject ERCOT to unacceptable risk of widespread cascading Outages. (3)An approved TOAP may be executed immediately, post-contingency, by the TO without instruction by ERCOT or shall be executed upon direction by ERCOT. (4)ERCOT may limit the quantity of TOAPs that are used. (5)Restoration of any Load shed by executing the TOAP shall be coordinated with ERCOT.

Definitions 2 21 November, 3, 2007 Implemented Temporary Outage Action Plan (TOAP) requiring 40 MW load shed at 23:10 in Corpus Christi area TOAP prepared in the event a forced outage occurs during a planned outage and the only mitigating action to preserve system security is shedding load Firm load shed at Airline, Laguna, Port Aransas, North Padre andNaval base area due to the loss of the Airline 138/69 kV Autotransformer #1 during the planned outage of the Airline 138/69 KV Autotransformer #2.

Definitions 3 4 Interconnection Reliability Operating Limit(IROL) - A System Operating Limit that, if violated, could lead to instability, uncontrolled separation, or Cascading outages that adversely impact the reliability of the Bulk Electric System. Interconnection Reliability Operating Limit Tv (IROL Tv) - The maximum time that an Interconnection Reliability Operating Limit can be violated before the risk to the interconnection or other Reliability Coordinator Area(s) becomes greater than acceptable. Each Interconnection Reliability Operating Limit’s Tv shall be less than or equal to 30 minutes. 22

Definitions 5 System Operating Limit(SOL) - 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 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) 23

As a Transmission Operator do you have the authority to implement real time actions to ensure the stable and reliable operation of the bulk electric system? a) Yes, I have the authority. b) No, only under the direction of ERCOT. c) Only ERCOT has authority to implement real time actions to ensure the stable and reliable operation of the bulk electric system. Answer- Yes, I have the authority. Responding to post contingency overloads, IROL’s and SOL’s 24

Responding to post contingency overloads, IROL’s and SOL’s ERCOT Control Area Authority (1) ERCOT, as Control Area Operator (CAO), is authorized to perform the following actions for the limited purpose of securely operating the ERCOT Transmission Grid under the standards specified in North American Electric Reliability Corporation (NERC) Standards, the Operating Guides and these Protocols, including: –(a) Direct the physical operation of the ERCOT Transmission Grid, including circuit breakers, switches, voltage control equipment, and Load-shedding equipment; –(b)Dispatch Resources that have committed to provide Ancillary Services; –© Direct changes in the operation of voltage control equipment; –(d)Direct the implementation of Reliability Must-Run (RMR) Service, Remedial Action Plans (RAPs), Special Protection Systems (SPSs), and transmission switching to prevent the violation of ERCOT Transmission Grid security limits; and –(e)Perform additional actions required to prevent an imminent Emergency Condition or to restore the ERCOT Transmission Grid to a secure state in the event of an ERCOT Transmission Grid Emergency Condition. 25

PER R1. Each Transmission Operator and Balancing Authority shall provide operating personnel with the responsibility and authority to implement real-time actions to ensure the stable and reliable operation of the Bulk Electric System. TOP CFR Responsibility Matrix 1 Jan 2014 Responding to post contingency overloads, IROL’s and SOL’s ERCOT ISO shall provide operating personnel with the responsibility and authority to implement real-time actions to ensure the stable and reliable operation of the Bulk Electric System. Each Local Control Center shall provide operating personnel with the responsibility and authority to implement real-time actions to ensure the stable and reliable operation of the Bulk Electric System. 26

What options do you have to relieve a post contingency overload? a) None. b) Shed load. c) Switch. d) Re dispatch Generation e) b,c, and d Answer E) b,c, and d Responding to post contingency overloads, IROL’s and SOL’s 27

What options do you have to relieve a post contingency overload? Re-dispatch Generation Switching Return equipment to service Close Normal opens in your system Remove the overloaded transmission line from service. Load Shed Responding to post contingency overloads, IROL’s and SOL’s 28

Control area mw load 600 mw available gen Export 1000 Scenario1 Control area 1 Control area 4 Control area 5 Control area 3 Control area mw load 500mw available gen Export 250 Control area mw load 200mw available gen Export 500 Control area mw load 0 mw available gen Importing 2000 Control area mw load 200mw available gen Export

Control area mw load 600 mw available gen Export 1000 Scenario1 Control area 1 Control area 4 Control area 5 Control area 3 Control area mw load 500mw available gen Export 250 Control area mw load 200mw available gen Export 500 Control area mw load 0 mw available gen Importing 2000 Control area mw load 200mw available gen Export 250 When the transmission line trips, voltage in control area 3 drops below.90 per unit 30

What options do you have to relieve a post contingency overload? a) Shed load in control area 3 b) Switch. c) Re dispatch Generation Answer- A) Shed load in control area 3 Scenario1 31

Blue=138kv=200 mva 1 4 Scenario 2 #1 75 mw load #2 50 mw load #4 75 mw load #3 25 mw load #5 40 mw load #6 25 mw load 290 mw generation 32

Blue=138kv=200 mva % Sta 1 75 mw load Sta 2 50 mw load Sta 3 25 mw load Sta 4 75 mw load Sta 5 40 mw load Sta 6 25 mw load Sta mw Generation Scenario2 33

What are you going to do you to relieve the post contingency overload? a) Shed load at station 1,2, 4, or 5 b) Switch. c) Re dispatch Generation d) Shed load at station 3 or 6 Answer- A) Shed load at station 1,2, 4, or 5 Scenario2 34

GG Blue=138kv=500 mva except for line btw 2 and 3 rated for 300 mva G Sta 1 175mw load Sta mw load Sta mw load Sta 4 90 mw load Sta mw load offline Gen 350 available 500 Gen 300 available 300 Scenario 3 35

GG Blue=138kv=500 mva except for line btw 2 and 3 rated for 300 mva G Sta 1 175mw load Sta mw load Sta mw load Sta 4 90 mw load Sta mw load offline Gen 650 available 150 Gen Tripped available Scenario3 36

What are you going to do you to relieve the post contingency overload? a) Shed load at station 1,2, 4, or 5 b) Close Normal open c) Re dispatch Generation Answer- B) Close Normal open Scenario3 37

13 45 City Gen 500 available 100 LD 2500Mw Gen 250 Available Gen 50 mw Available 500 Load 500 mw Gen 1250 available 1500 Gen 1500 available 0 Red=345kv=1000 mva Blue=138kv=500 mva Load 500 mw Scenario 4 38

13 45 City Gen 500 available 100 LD 2500Mw Gen 250 Available Gen 50 mw Available 500 Load 500 mw Gen 1250 available 1500 Gen 1500 available 0 Red=345kv=1000 mva Blue=138kv=500 mva Load 500 mw 120 Scenario4 39

What are you going to do you to relieve the post contingency overload? a) Shed load in the city b) Close Normal open c) Re dispatch Generation Answer- C) Re dispatch Generation Scenario 4 40

References NERC Glossary of Terms NERC Standards ERCOT Nodal Protocols ERCOT Operating Guides 41

Questions ? ? ? ? 42

1.Which one of the 4 different types of plans is enacted to relieve pre contingency overloads? a)TOAP b)PCAP c)MP d)RAP 43

2.What options do you have to relieve a post contingency overload? a)Shed load b)Remove transmission line from service c)Close normal open d)Re dispatch Generation e)All the above 44

3.Who has the authority to implement real time actions to ensure the stable and reliable operation of the bulk electric system? a)ERCOT b)Transmission Operator c)Both a and b 45

4.Select the correct definition of a Temporary Outage Action plan (TOAP): a)Actions taken to alleviate an overload on a given transmission element that would show up post-contingency b)A plan developed by the outage coordinators to alleviate an overload that is related to an outage c)Pre-determined actions to be taken associated with the occurrence of a specific contingency event if congestion management methods cannot resolve the post-contingency overload d)Automatic relay action, approved by ERCOT, employed to prevent congestion 46

5.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 is also known as: a)IROL b)Transfer Capacity Limit c)SOL d)Alarm limit 47