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Severity Risk Index (SRI) is a **daily metric** where transmission loss, generation loss, and load loss events aggregate into a single value that indicates performance of the BES.
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The SRI values range from zero to 1000.
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Zero is a theoretical condition where no transmission, generation or load loss occurred during the entire day.
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To the corollary, a value of 1000 would represent a situation where every transmission, generation and load was lost during the entire day.
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The SRI was designed to be usable for the entirety of NERC as well as applied more granularly, such as at an interconnection level.
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Source: <d-citekey="nerc2020sri"></d-cite> p5
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**SRI**<d-citekey="nerc2024sor"></d-cite> (p12)
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> Severity Risk Index (SRI) is a **daily metric**where transmission loss, generation loss, and load loss events aggregate into a single value that indicates performance of the BES. The SRI values range from zero to 1000. Zero is a theoretical condition where no transmission, generation or load loss occurred during the entire day. To the corollary, a value of 1000 would represent a situation where every transmission, generation and load was lost during the entire day. The SRI was designed to be usable for the entirety of NERC as well as applied more granularly, such as at an interconnection level.
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The SRI provides a quantitative measure that assesses the relative severity of the combined impact of load, generation, and transmission loss on the BPS daily and offers a comprehensive picture of the performance of the BPS, allowing NERC to assess year-on-year reliability trends.
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### Elaboration by NERC
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Source: <d-citekey="nerc2024sor"></d-cite> p12
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> The SRI provides a quantitative measure that assesses the relative severity of the combined impact of load, generation, and transmission loss on the BPS daily and offers a comprehensive picture of the performance of the BPS, allowing NERC to assess year-on-year reliability trends.
Copy file name to clipboardExpand all lines: _wiki/small-signal-stability.md
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tags: stability
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category: wiki
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bibliography: papers.bib
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authors:
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- name: Jinning Wang
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url: https://jinningwang.github.io
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date: 2025-03-15
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last_update: 2025-06-19
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---
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**Small-Signal Stability** <d-citekey="kundur1994Power"></d-cite> (p699, first edition)
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### Definition in a Textbook
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Small-signal stability, as defined in Chapter 2, is the ability of the power system to maintain synchronism when subjected to **small disturbances**.
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In this context, a disturbance is considered to be **small** if the equations that describe the resulting response of the system may be **linearized** for the purpose of analysis.
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Instability that may result can be of two forms:
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(i) steady increase in generator rotor angle due to lack of synchronizing torque, or
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(ii) rotor oscillations of increasing amplitude due to lack of sufficient damping torque.
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In today’s practical power systems, the small-signal stability problem is usually one of insufficient damping of system oscillations.
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Small-signal analysis using linear techniques provides valuable information about the inherent dynamic characteristics of the power system and assists in its design.
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Source: <d-citekey="kundur1994Power"></d-cite> p699, first edition
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_Jinning's Note: The term "small-signal stability" is sometimes used interchangeably with "small-disturbance stability" in the context of power system stability._
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> Small-signal stability, as defined in Chapter 2, is the ability of the power system to maintain synchronism when subjected to **small disturbances**. In this context, a disturbance is considered to be **small** if the equations that describe the resulting response of the system may be **linearized** for the purpose of analysis. Instability that may result can be of two forms:
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> (i) steady increase in generator rotor angle due to lack of synchronizing torque, or
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> (ii) rotor oscillations of increasing amplitude due to lack of sufficient damping torque.
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> In today’s practical power systems, the small-signal stability problem is usually one of insufficient damping of system oscillations.
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> Small-signal analysis using linear techniques provides valuable information about the inherent dynamic characteristics of the power system and assists in its design.
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The term "small-signal stability" is sometimes used interchangeably with "small-disturbance stability" in the context of power system stability.
Synchronized Reserve is reserve capability that can be converted fully into energy or load that can be removed from the system within 10 minutes of the request from the PJM dispatcher and must be provided by equipment electrically synchronized to the system. Resources committed to the Synchronized Reserve product can meet the Synchronized Reserve, Contingency (Primary) Reserve Service and the 30-Minute Reserve Service simultaneously.
> Synchronized Reserve is reserve capability that can be converted fully into energy or load that can be removed from the system within 10 minutes of the request from the PJM dispatcher and must be provided by equipment electrically synchronized to the system. Resources committed to the Synchronized Reserve product can meet the Synchronized Reserve, Contingency (Primary) Reserve Service and the 30-Minute Reserve Service simultaneously.
Copy file name to clipboardExpand all lines: _wiki/spot-market.md
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tags: market, trading, FERC
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category: wiki
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bibliography: papers.bib
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authors:
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- name: Jinning Wang
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url: https://jinningwang.github.io
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date: 2025-03-15
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last_update: 2025-06-19
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---
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**Spot Market** <d-citekey="ferc2020glossary"></d-cite> by FERC
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### Definition by FERC
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The natural gas market for contractual commitments that are short term (usually a month or less) and that begin in the near future (often the next day, or within days).
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Source: <d-citekey="ferc2020glossary"></d-cite>
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In electricity, spot markets are usually organized markets for [day-ahead](/wiki/day-ahead-markets) and real-time electricity run by an independent system operator or regional transmission organization.
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> The natural gas market for contractual commitments that are short term (usually a month or less) and that begin in the near future (often the next day, or within days).
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>
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> In electricity, spot markets are usually organized markets for [day-ahead](/wiki/day-ahead-markets) and real-time electricity run by an independent system operator or regional transmission organization.
The maximum power flow possible through some particular point in the system while maintaining stability in the entire system or the part of the system to which the stability limit refers.
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Source: <d-citekey="nerc2024glossary"></d-cite>
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> The maximum power flow possible through some particular point in the system while maintaining stability in the entire system or the part of the system to which the stability limit refers.
Copy file name to clipboardExpand all lines: _wiki/stability-limits.md
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tags: transmission-operation, PJM, ISO
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category: wiki
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bibliography: papers.bib
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authors:
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- name: Jinning Wang
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url: https://jinningwang.github.io
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date: 2025-03-15
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last_update: 2025-06-19
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**Stability Limits** by PJM <d-citekey="pjm2024m3"></d-cite> (p60, Revision 67)
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### Definition by PJM
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The PJM RTO established stability limits for preventing electrical separation of a generating unit or a portion of the PJM RTO. PJM recognizes three types of stability:
- Steady State Stability - A gradual slow change to generation that is balanced by load.
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- Transient Stability - The ability of a generating unit or a group of generating units to maintain synchronism following a relatively severe and sudden system disturbance. The first few cycles are the most critical time period.
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- Dynamic Stability - The ability of a generating unit or a group of generating units to damp oscillations caused by relatively minor disturbances through the action of properly tuned control systems.
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> The PJM RTO established stability limits for preventing electrical separation of a generating unit or a portion of the PJM RTO. PJM recognizes three types of stability:
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>
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> - Steady State Stability - A gradual slow change to generation that is balanced by load.
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> - Transient Stability - The ability of a generating unit or a group of generating units to maintain synchronism following a relatively severe and sudden system disturbance. The first few cycles are the most critical time period.
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> - Dynamic Stability - The ability of a generating unit or a group of generating units to damp oscillations caused by relatively minor disturbances through the action of properly tuned control systems.
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>
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> PJM will operate the facilities that are under PJM operational control such that the PJM system will maintain angular and voltage stability following any single facility malfunction or failure.
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>
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> In general, stability is not a limiting constraint on the PJM RTO.
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PJM will operate the facilities that are under PJM operational control such that the PJM system will maintain angular and voltage stability following any single facility malfunction or failure.
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### Another Definition by PJM
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In general, stability is not a limiting constraint on the PJM RTO.
**Stability Related Transmission Limits** by PJM <d-citekey="pjm2024m3"></d-cite> (p40, Revision 67)
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> The ability of a generating unit or a group of generating units to maintain synchronism following a system disturbance can be identified using real time and study applications such as the PJM Transient Stability Analysis (TSA) tool. Based on results from TSA, stability limits will be established and logged within PJM’s TO Connection. For real power (MW) stability limits only, TO Connection **stability limits will be translated into a corresponding generator output constraint** (in MW) for a single generator or a group of generators.
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In addition to the thermal limits referenced in Section 2, PJM operates the PJM RTO considering voltage and stability related transmission limits as follows:
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### Stability Related Transmission Limits by PJM
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- Voltage Limits – High, Low, and Load Dump actual voltage limits, High and Low emergency voltage limits for contingency simulation, and voltage drop limits for wide area transfer simulations to protect against wide area voltage collapse.
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- Transfer Limits – The MW flow limitation across an interface to protect the system from large voltage drops or collapse caused by any viable contingency.
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- Stability Limits – limit based on **voltage phase angle difference** to protect portions of the PJM RTO from separation or unstable operation.
**Stability Limits** by PJM <d-citekey="pjm2024m11"></d-cite> (p82, Revision 133)
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The ability of a generating unit or a group of generating units to maintain synchronism following a system disturbance can be identified using real time and study applications such as the PJM Transient Stability Analysis (TSA) tool.
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Based on results from TSA, stability limits will be established and logged within PJM’s TO Connection.
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For real power (MW) stability limits only, TO Connection **stability limits will be translated into a corresponding generator output constraint**(in MW) for a single generator or a group of generators.
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> In addition to the thermal limits referenced in Section 2, PJM operates the PJM RTO considering voltage and stability related transmission limits as follows:
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>
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> - Voltage Limits – High, Low, and Load Dump actual voltage limits, High and Low emergency voltage limits for contingency simulation, and voltage drop limits for wide area transfer simulations to protect against wide area voltage collapse.
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> - Transfer Limits – The MW flow limitation across an interface to protect the system from large voltage drops or collapse caused by any viable contingency.
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> - Stability Limits – limit based on **voltage phase angle difference**to protect portions of the PJM RTO from separation or unstable operation.
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