Short circuit ratio (electrical grid)

<h2 id="grid-strength">Grid strength</h2>
The term grid strength (also system strength) is used to describe the resiliency of the grid to the small changes in the vicinity of the grid location (“grid stiffness”).<a class="footnote-ref" id="fnref:5" href="#fn:5">5</a> From the side of an electrical generator, the system strength is related to the changes of voltage the generator encounters on its <a href="/facts/Terminal_(electronics)/CwbKGSuB">terminals</a> as the generator's current injection varies. Therefore, the quantification of the system strength can be done through finding the equivalent (<a href="/facts/Th%25C3%25A9venin%2527s_theorem/rwYa905x">Thévenin</a>) <a href="/facts/Electrical_impedance/I06NSXtN">electrical impedance</a> of the system as observed from these terminals (the strength is inversely proportional to the resistance). SCR and its variations provide a convenient way to calculate this impedance under normal or <a href="/facts/Contingency_(electrical_grid)/GI2Ap0HI">contingency</a> conditions (these estimates are not intended for the actual short-circuit state).<a class="footnote-ref" id="fnref:6" href="#fn:6">6</a>
Strong grids provide a reliable reference for power sources to synchronize.<a class="footnote-ref" id="fnref:7" href="#fn:7">7</a> In a very stiff system the voltage does not change with variations of the power injected by a particular generator, making its control simpler. In a traditional grid dominated by <a href="/facts/Synchronous_generator/NY4NsL9n">synchronous generators</a>, a strong grid with SCR greater than 3.0 will have the desired voltage stability and active power reserves.<a class="footnote-ref" id="fnref:8" href="#fn:8">8</a> A weak grid (with SCR values between 2.0 and 3.0<a class="footnote-ref" id="fnref:9" href="#fn:9">9</a>) can exhibit <a href="/facts/Voltage_control/kjmn9HsY">voltage instability</a> and control problems.<a class="footnote-ref" id="fnref:10" href="#fn:10">10</a> A grid with SCR below 2.0 is very weak.<a class="footnote-ref" id="fnref:11" href="#fn:11">11</a>

<h3>Importance of overcurrent</h3>
Grid strength is also important for its <a href="/facts/Overcurrent/Sx9FXrUI">overcurrent</a> capabilities that are essential for the <a href="/facts/Power_system_operations/R9mKeJL2">power system operations</a>. Lack of overcurrent capability (low SCR) in a weak grid creates a multitude of problems, including:<a class="footnote-ref" id="fnref:12" href="#fn:12">12</a> 

<ul><li>transients during the large load changes will cause large variations of the grid voltage, causing problems with the loads (e.g., some motors might not be able to start in the <a href="/facts/Undervoltage/DS6bH6Nh">undervoltage</a> condition);</li>
<li>the grid protection devices are designed to be triggered by a sufficient level of overcurrent. In a weak system the short circuit current might be hard to distinguish from a normal transient overcurrent encountered during the load changes;</li>
<li>during a <a href="/facts/Black_start/c9gASxr6">black start</a> operation after a <a href="/facts/Power_outage/CBp7xY9w">power outage</a>, large <a href="/facts/Inrush_current/0qg0rKmL">inrush current</a> might be needed to energize the system components. For example, if some loads in a weak system remain connected, an <a href="/facts/Inverter-based_resource/asTJDPGs">inverter-based resource</a> might not be able to start.</li></ul>
<h3>Presence of inverter-based resources</h3>
Large penetration of the <a href="/facts/Inverter-based_resource/asTJDPGs">inverter-based resources</a> (IBRs) reduces the short circuit level: a typical synchronous generator can deliver a significant <a href="/facts/Overcurrent/Sx9FXrUI">overcurrent</a>, 2-5<a class="footnote-ref" id="fnref:13" href="#fn:13">13</a> <a href="/facts/Per-unit_system/XY8XPoKG">p.u.</a>, for a relatively long time (minutes), while the component limitations of the IBRs result in overcurrent limits of less than 2<a class="footnote-ref" id="fnref:14" href="#fn:14">14</a> p.u. (usually 1.1-1.2 p.u.).<a class="footnote-ref" id="fnref:15" href="#fn:15">15</a>
The original SCR definition above was intended for a system with predominantly synchronous generation,<a class="footnote-ref" id="fnref:16" href="#fn:16">16</a> so multiple alternative metrics, including weighted short circuit ratio (WSCR), composite short circuit ratio (CSCR), equivalent circuit short circuit ratio (ESCR), and short circuit ratio with interaction factors (SCRIF), have been proposed for the grids with multiple adjacent IBRs to avoid an overestimation of the grid strength<a class="footnote-ref" id="fnref:17" href="#fn:17">17</a><a class="footnote-ref" id="fnref:18" href="#fn:18">18</a> (an IBR relies on grid strength to synchronize its operation and does not have much overcurrent capacity<a class="footnote-ref" id="fnref:19" href="#fn:19">19</a>). 
Henderson et al. argue that in case of IBRs the SCR and system strength are in fact decoupled and propose a new metric, grid strength impedance.<a class="footnote-ref" id="fnref:20" href="#fn:20">20</a>
Integrating renewable energy sources often raises concerns about the system's strength. The ability of different components in a <a href="/facts/Power_system/ruyJzGVv">power system</a> to perform effectively depends on the system's strength, which measures the system variables' sensitivity to disturbances. The short circuit ratio (SCR) is an indicator of the strength of a network bus about the rated power of a device and is frequently used as a measure of system strength. A higher SCR value indicates a stronger system, meaning that the impact of disturbances on voltage and other variables will be minimized. A strong system is defined as having an SCR above three, and the SCRs of weak and very weak systems range between three and two and below two, respectively.<a class="footnote-ref" id="fnref:21" href="#fn:21">21</a>
<a href="/facts/Power_electronic_applications/8BAQ3jDP">Power electronic applications</a> often encounter issues related to SCR, particularly in renewable energy systems that use power converters to connect to power grids. When connecting HVDC/FACTs devices based on <a href="/facts/Current_source_converters/L8cJc3Hu">current source converters</a> to <a href="/facts/Weak_AC_systems/HTCMnJwo">weak AC systems</a>, particular technologies must be employed to overcome SCR of less than three. For <a href="/facts/HVDC/FDIob86A">HVDC</a>, voltage-source-based converters or capacitor-commutated converters are utilized in applications with SCR near one. Failing to use these technologies will require special studies to determine the impact and take measures to prevent or minimize the adverse effects, as low levels of SCR can cause problems such as high over-voltages, low-frequency resonances, and instability in <a href="/facts/Control_systems/8CEjIDlS">control systems</a>.
<a href="/facts/Wind_farms/geQfaAFu">Wind farms</a> are commonly linked to less robust network sections away from the main power consumption areas. Problems with voltage stability that arise from incorporating large-scale wind power into vulnerable systems are crucial issues that require attention. Some wind turbines have specific minimum system strength criteria. GE indicates that the standard parameters of their wind turbine model are appropriate for systems with a Short Circuit Ratio (SCR) of five or higher. However, if connecting to weaker systems, it is necessary to carry out further analysis to guarantee that the model parameters are adequately adjusted. Specifically designed control methods for wind turbines or dynamic reactive compensation devices, such as <a href="/facts/STATCOM/1qXf8gW8">STATCOM</a>, are required to ensure optimal performance.<a class="footnote-ref" id="fnref:22" href="#fn:22">22</a>

<h4>Example</h4>
An experience at <a href="/facts/ERCOT/ePpTbHzB">ERCOT</a> in early 21st century provides a prime example of how the wind turbine's performance is affected by a weak system strength. The wind power plant, linked to the ERCOT grid through two 69kV transmission lines, worked efficiently when the SCR was around 4 during normal operations. However, when one of the 69kV lines was disconnected, the SCR dropped to 2 or less, leading to unfavorable, poorly damped, or un-damped voltage oscillations that were documented by PMUs at the Point of Interconnection (POI) of the wind plant. After a thorough investigation, it was determined that the aggressive voltage control used by the WPP was not appropriate for a weak grid environment and was the primary cause of the oscillatory response. Due to the low short circuit level detected by the wind generator voltage controller and the high voltage control gain, the oscillation occurred. When compared to the normal grid with high SCR, the closed loop voltage control would have a faster response under weak grid conditions. To replicate the oscillatory response, the event was simulated using a detailed dynamic model representing the WPP.<a class="footnote-ref" id="fnref:23" href="#fn:23">23</a>

<h2 id="impact-on-grid">Impact on grid</h2>
The SCR can be calculated for each point on an <a href="/facts/Electrical_grid/RkWPqjmG">electrical grid</a>. A point on a grid having a number of machines with an SCR above a number between 1 and 1.5 has less vulnerability to voltage instability. Hence, such a grid is known strong grid or power system. A power system (grid) having a lower SCR has more vulnerability to grid voltage instability. Hence such a grid or system is known as a weak grid or a weak power system.
Grid strength can be increased by installing <a href="/facts/Synchronous_condenser/2WsKtzgu">synchronous condensers</a>.<a class="footnote-ref" id="fnref:24" href="#fn:24">24</a> Condenser can act as a synchronous voltage source to support transient reactance and sub-transient reactance, also providing the <a href="/facts/Inertial_response/1P9fI8kL">inertial response</a> and fault current contribution. 
<a href="/facts/Static_synchronous_compensator/1qXf8gW8">Static synchronous compensators</a> may also be used to improve the SCR ratio, being the current source limited by storage discharge and thermal condition.

<h2 id="sources">Sources</h2>
<ul><li>Kundur, P.; Balu, N.J.; Lauby, M.G. (1994). <a href="https://books.google.com/books?id=wOlSAAAAMAAJ">Power System Stability and Control</a>. EPRI power system engineering series. McGraw-Hill Education. <a href="/facts/ISBN_(identifier)/15AdSPa9">ISBN</a> 978-0-07-035958-1. Retrieved 2023-06-12.</li>
<li>NERC (February 2018). <a href="https://www.nerc.com/pa/RAPA/ra/Reliability%20Assessments%20DL/Short_Circuit_whitepaper_Final_1_26_18.pdf">Short-Circuit Modeling and System Strength</a> (PDF). Atlanta, GA.{{cite book}}: CS1 maint: location missing publisher (link)</li>
<li>NERC (December 2017). <a href="https://www.nerc.com/pa/RAPA/ra/Reliability%20Assessments%20DL/Short_Circuit_whitepaper_Final_1_26_18.pdf">Integrating Inverter-Based Resources into Low Short Circuit Strength Systems</a> (PDF). Atlanta, GA.{{cite book}}: CS1 maint: location missing publisher (link)</li>
<li>Henderson, Callum; Egea-Alvarez, Agusti; Kneuppel, Thyge; Yang, Guangya; Xu, Lie (2023). <a href="https://backend.orbit.dtu.dk/ws/portalfiles/portal/304326476/BERAT_Grid_Strength_Impedance_Metric_An_Alternative_to_SCR_for_Evaluating_System_Strength_in_Converter_Dominated_Systems.pdf">"Grid Strength Impedance Metric: An Alternative to SCR for Evaluating System Strength in Converter Dominated Systems"</a> (PDF). IEEE Transactions on Power Delivery. 39. Institute of Electrical and Electronics Engineers (IEEE): 386–396. <a href="/facts/Doi_(identifier)/muM9Etpq">doi</a>:<a href="https://doi.org/10.1109%2Ftpwrd.2022.3233455">10.1109/tpwrd.2022.3233455</a>. <a href="/facts/ISSN_(identifier)/DPAflDvU">ISSN</a> <a href="https://search.worldcat.org/issn/0885-8977">0885-8977</a>. <a href="/facts/S2CID_(identifier)/ldJsHa2Y">S2CID</a> <a href="https://api.semanticscholar.org/CorpusID:255660560">255660560</a>.</li>
<li>Burton, T.; Sharpe, D.; Jenkins, N.; Bossanyi, E. (2001). <a href="https://books.google.com/books?id=4UYm893y-34C&pg=PA572">Wind Energy Handbook</a>. John Wiley & Sons. <a href="/facts/ISBN_(identifier)/15AdSPa9">ISBN</a> 978-0-471-48997-9. Retrieved 2023-06-30.</li>
<li>Zhang, Yang; Huang, Shun-Hsien Fred; Schmall, John; Conto, Jose; Billo, Jeffrey; Rehman, Ehsan (2014). <a href="https://www.researchgate.net/publication/290732425">"Evaluating system strength for large-scale wind plant integration"</a>. 2014 IEEE PES General Meeting | Conference & Exposition. IEEE. pp. 1–5. <a href="/facts/Doi_(identifier)/muM9Etpq">doi</a>:<a href="https://doi.org/10.1109%2Fpesgm.2014.6939043">10.1109/pesgm.2014.6939043</a>. <a href="/facts/ISBN_(identifier)/15AdSPa9">ISBN</a> 978-1-4799-6415-4.</li>
<li>Li, Haiguo; Nie, Cheng; Wang, Fred (2022). <a href="https://doi.org/10.1109%2Fojpel.2022.3194849">"Grid Strengthening IBR: An Inverter-Based Resource Enhanced by a Co-Located Synchronous Condenser for High Overcurrent Capability"</a>. IEEE Open Journal of Power Electronics. 3. Institute of Electrical and Electronics Engineers (IEEE): 535–548. <a href="/facts/Doi_(identifier)/muM9Etpq">doi</a>:<a href="https://doi.org/10.1109%2Fojpel.2022.3194849">10.1109/ojpel.2022.3194849</a>. <a href="/facts/ISSN_(identifier)/DPAflDvU">ISSN</a> <a href="https://search.worldcat.org/issn/2644-1314">2644-1314</a>. <a href="/facts/S2CID_(identifier)/ldJsHa2Y">S2CID</a> <a href="https://api.semanticscholar.org/CorpusID:251194445">251194445</a>.</li>
<li>Ramasubramanian, Deepak (November 8, 2019). <a href="https://cigre-usnc.org/wp-content/uploads/2019/11/Deepak_Ramasubramanian_presentation.pdf">"Challenges and Possible Solutions for the Power System of the Future"</a> (PDF). cigre-usnc.org. <a href="/facts/CIGRE/IHNruqsB">CIGRE</a>. Retrieved 9 July 2023.</li></ul>

<h2 id="references">References</h2>

<ol>
<li id="fn:1">NERC 2017, p. 1. - NERC (December 2017). Integrating Inverter-Based Resources into Low Short Circuit Strength Systems (PDF). Atlanta, GA. <a href="https://www.nerc.com/pa/RAPA/ra/Reliability%20Assessments%20DL/Short_Circuit_whitepaper_Final_1_26_18.pdf" target="_blank">https://www.nerc.com/pa/RAPA/ra/Reliability%20Assessments%20DL/Short_Circuit_whitepaper_Final_1_26_18.pdf</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></li>
<li id="fn:2">Ramasubramanian 2019, p. 6. - Ramasubramanian, Deepak (November 8, 2019). "Challenges and Possible Solutions for the Power System of the Future" (PDF). cigre-usnc.org. CIGRE. Retrieved 9 July 2023. <a href="https://cigre-usnc.org/wp-content/uploads/2019/11/Deepak_Ramasubramanian_presentation.pdf" target="_blank">https://cigre-usnc.org/wp-content/uploads/2019/11/Deepak_Ramasubramanian_presentation.pdf</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></li>
<li id="fn:3">Burton et al. 2001, p. 572. - Burton, T.; Sharpe, D.; Jenkins, N.; Bossanyi, E. (2001). Wind Energy Handbook. John Wiley & Sons. ISBN 978-0-471-48997-9. Retrieved 2023-06-30. <a href="https://books.google.com/books?id=4UYm893y-34C&pg=PA572" target="_blank">https://books.google.com/books?id=4UYm893y-34C&pg=PA572</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></li>
<li id="fn:4">Henderson et al. 2023, p. 1. - Henderson, Callum; Egea-Alvarez, Agusti; Kneuppel, Thyge; Yang, Guangya; Xu, Lie (2023). "Grid Strength Impedance Metric: An Alternative to SCR for Evaluating System Strength in Converter Dominated Systems" (PDF). IEEE Transactions on Power Delivery. 39. Institute of Electrical and Electronics Engineers (IEEE): 386–396. doi:10.1109/tpwrd.2022.3233455. ISSN 0885-8977. S2CID 255660560. <a href="https://backend.orbit.dtu.dk/ws/portalfiles/portal/304326476/BERAT_Grid_Strength_Impedance_Metric_An_Alternative_to_SCR_for_Evaluating_System_Strength_in_Converter_Dominated_Systems.pdf" target="_blank">https://backend.orbit.dtu.dk/ws/portalfiles/portal/304326476/BERAT_Grid_Strength_Impedance_Metric_An_Alternative_to_SCR_for_Evaluating_System_Strength_in_Converter_Dominated_Systems.pdf</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></li>
<li id="fn:5">NERC 2017, p. vii. - NERC (December 2017). Integrating Inverter-Based Resources into Low Short Circuit Strength Systems (PDF). Atlanta, GA. <a href="https://www.nerc.com/pa/RAPA/ra/Reliability%20Assessments%20DL/Short_Circuit_whitepaper_Final_1_26_18.pdf" target="_blank">https://www.nerc.com/pa/RAPA/ra/Reliability%20Assessments%20DL/Short_Circuit_whitepaper_Final_1_26_18.pdf</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></li>
<li id="fn:6">NERC 2017, p. 1. - NERC (December 2017). Integrating Inverter-Based Resources into Low Short Circuit Strength Systems (PDF). Atlanta, GA. <a href="https://www.nerc.com/pa/RAPA/ra/Reliability%20Assessments%20DL/Short_Circuit_whitepaper_Final_1_26_18.pdf" target="_blank">https://www.nerc.com/pa/RAPA/ra/Reliability%20Assessments%20DL/Short_Circuit_whitepaper_Final_1_26_18.pdf</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></li>
<li id="fn:7">NERC 2017, p. vii. - NERC (December 2017). Integrating Inverter-Based Resources into Low Short Circuit Strength Systems (PDF). Atlanta, GA. <a href="https://www.nerc.com/pa/RAPA/ra/Reliability%20Assessments%20DL/Short_Circuit_whitepaper_Final_1_26_18.pdf" target="_blank">https://www.nerc.com/pa/RAPA/ra/Reliability%20Assessments%20DL/Short_Circuit_whitepaper_Final_1_26_18.pdf</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></li>
<li id="fn:8">Henderson et al. 2023, p. 1. - Henderson, Callum; Egea-Alvarez, Agusti; Kneuppel, Thyge; Yang, Guangya; Xu, Lie (2023). "Grid Strength Impedance Metric: An Alternative to SCR for Evaluating System Strength in Converter Dominated Systems" (PDF). IEEE Transactions on Power Delivery. 39. Institute of Electrical and Electronics Engineers (IEEE): 386–396. doi:10.1109/tpwrd.2022.3233455. ISSN 0885-8977. S2CID 255660560. <a href="https://backend.orbit.dtu.dk/ws/portalfiles/portal/304326476/BERAT_Grid_Strength_Impedance_Metric_An_Alternative_to_SCR_for_Evaluating_System_Strength_in_Converter_Dominated_Systems.pdf" target="_blank">https://backend.orbit.dtu.dk/ws/portalfiles/portal/304326476/BERAT_Grid_Strength_Impedance_Metric_An_Alternative_to_SCR_for_Evaluating_System_Strength_in_Converter_Dominated_Systems.pdf</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></li>
<li id="fn:9">Zhang et al. 2014, p. 1. - Zhang, Yang; Huang, Shun-Hsien Fred; Schmall, John; Conto, Jose; Billo, Jeffrey; Rehman, Ehsan (2014). "Evaluating system strength for large-scale wind plant integration". 2014 IEEE PES General Meeting | Conference & Exposition. IEEE. pp. 1–5. doi:10.1109/pesgm.2014.6939043. ISBN 978-1-4799-6415-4. <a href="https://www.researchgate.net/publication/290732425" target="_blank">https://www.researchgate.net/publication/290732425</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></li>
<li id="fn:10">NERC 2017, p. vii. - NERC (December 2017). Integrating Inverter-Based Resources into Low Short Circuit Strength Systems (PDF). Atlanta, GA. <a href="https://www.nerc.com/pa/RAPA/ra/Reliability%20Assessments%20DL/Short_Circuit_whitepaper_Final_1_26_18.pdf" target="_blank">https://www.nerc.com/pa/RAPA/ra/Reliability%20Assessments%20DL/Short_Circuit_whitepaper_Final_1_26_18.pdf</a> <a href="#fnref:10" class="footnote-back-ref">↩</a></li>
<li id="fn:11">Zhang et al. 2014, p. 1. - Zhang, Yang; Huang, Shun-Hsien Fred; Schmall, John; Conto, Jose; Billo, Jeffrey; Rehman, Ehsan (2014). "Evaluating system strength for large-scale wind plant integration". 2014 IEEE PES General Meeting | Conference & Exposition. IEEE. pp. 1–5. doi:10.1109/pesgm.2014.6939043. ISBN 978-1-4799-6415-4. <a href="https://www.researchgate.net/publication/290732425" target="_blank">https://www.researchgate.net/publication/290732425</a> <a href="#fnref:11" class="footnote-back-ref">↩</a></li>
<li id="fn:12">Li, Nie & Wang 2022, p. 536. - Li, Haiguo; Nie, Cheng; Wang, Fred (2022). "Grid Strengthening IBR: An Inverter-Based Resource Enhanced by a Co-Located Synchronous Condenser for High Overcurrent Capability". IEEE Open Journal of Power Electronics. 3. Institute of Electrical and Electronics Engineers (IEEE): 535–548. doi:10.1109/ojpel.2022.3194849. ISSN 2644-1314. S2CID 251194445. <a href="https://doi.org/10.1109%2Fojpel.2022.3194849" target="_blank">https://doi.org/10.1109%2Fojpel.2022.3194849</a> <a href="#fnref:12" class="footnote-back-ref">↩</a></li>
<li id="fn:13">Li, Nie & Wang 2022, p. 536. - Li, Haiguo; Nie, Cheng; Wang, Fred (2022). "Grid Strengthening IBR: An Inverter-Based Resource Enhanced by a Co-Located Synchronous Condenser for High Overcurrent Capability". IEEE Open Journal of Power Electronics. 3. Institute of Electrical and Electronics Engineers (IEEE): 535–548. doi:10.1109/ojpel.2022.3194849. ISSN 2644-1314. S2CID 251194445. <a href="https://doi.org/10.1109%2Fojpel.2022.3194849" target="_blank">https://doi.org/10.1109%2Fojpel.2022.3194849</a> <a href="#fnref:13" class="footnote-back-ref">↩</a></li>
<li id="fn:14">Li, Nie & Wang 2022, p. 536. - Li, Haiguo; Nie, Cheng; Wang, Fred (2022). "Grid Strengthening IBR: An Inverter-Based Resource Enhanced by a Co-Located Synchronous Condenser for High Overcurrent Capability". IEEE Open Journal of Power Electronics. 3. Institute of Electrical and Electronics Engineers (IEEE): 535–548. doi:10.1109/ojpel.2022.3194849. ISSN 2644-1314. S2CID 251194445. <a href="https://doi.org/10.1109%2Fojpel.2022.3194849" target="_blank">https://doi.org/10.1109%2Fojpel.2022.3194849</a> <a href="#fnref:14" class="footnote-back-ref">↩</a></li>
<li id="fn:15">Henderson et al. 2023, p. 1. - Henderson, Callum; Egea-Alvarez, Agusti; Kneuppel, Thyge; Yang, Guangya; Xu, Lie (2023). "Grid Strength Impedance Metric: An Alternative to SCR for Evaluating System Strength in Converter Dominated Systems" (PDF). IEEE Transactions on Power Delivery. 39. Institute of Electrical and Electronics Engineers (IEEE): 386–396. doi:10.1109/tpwrd.2022.3233455. ISSN 0885-8977. S2CID 255660560. <a href="https://backend.orbit.dtu.dk/ws/portalfiles/portal/304326476/BERAT_Grid_Strength_Impedance_Metric_An_Alternative_to_SCR_for_Evaluating_System_Strength_in_Converter_Dominated_Systems.pdf" target="_blank">https://backend.orbit.dtu.dk/ws/portalfiles/portal/304326476/BERAT_Grid_Strength_Impedance_Metric_An_Alternative_to_SCR_for_Evaluating_System_Strength_in_Converter_Dominated_Systems.pdf</a> <a href="#fnref:15" class="footnote-back-ref">↩</a></li>
<li id="fn:16">NERC 2017, p. 1. - NERC (December 2017). Integrating Inverter-Based Resources into Low Short Circuit Strength Systems (PDF). Atlanta, GA. <a href="https://www.nerc.com/pa/RAPA/ra/Reliability%20Assessments%20DL/Short_Circuit_whitepaper_Final_1_26_18.pdf" target="_blank">https://www.nerc.com/pa/RAPA/ra/Reliability%20Assessments%20DL/Short_Circuit_whitepaper_Final_1_26_18.pdf</a> <a href="#fnref:16" class="footnote-back-ref">↩</a></li>
<li id="fn:17">NERC 2017, p. 2. - NERC (December 2017). Integrating Inverter-Based Resources into Low Short Circuit Strength Systems (PDF). Atlanta, GA. <a href="https://www.nerc.com/pa/RAPA/ra/Reliability%20Assessments%20DL/Short_Circuit_whitepaper_Final_1_26_18.pdf" target="_blank">https://www.nerc.com/pa/RAPA/ra/Reliability%20Assessments%20DL/Short_Circuit_whitepaper_Final_1_26_18.pdf</a> <a href="#fnref:17" class="footnote-back-ref">↩</a></li>
<li id="fn:18">Henderson et al. 2023, p. 1. - Henderson, Callum; Egea-Alvarez, Agusti; Kneuppel, Thyge; Yang, Guangya; Xu, Lie (2023). "Grid Strength Impedance Metric: An Alternative to SCR for Evaluating System Strength in Converter Dominated Systems" (PDF). IEEE Transactions on Power Delivery. 39. Institute of Electrical and Electronics Engineers (IEEE): 386–396. doi:10.1109/tpwrd.2022.3233455. ISSN 0885-8977. S2CID 255660560. <a href="https://backend.orbit.dtu.dk/ws/portalfiles/portal/304326476/BERAT_Grid_Strength_Impedance_Metric_An_Alternative_to_SCR_for_Evaluating_System_Strength_in_Converter_Dominated_Systems.pdf" target="_blank">https://backend.orbit.dtu.dk/ws/portalfiles/portal/304326476/BERAT_Grid_Strength_Impedance_Metric_An_Alternative_to_SCR_for_Evaluating_System_Strength_in_Converter_Dominated_Systems.pdf</a> <a href="#fnref:18" class="footnote-back-ref">↩</a></li>
<li id="fn:19">NERC 2017, p. vii. - NERC (December 2017). Integrating Inverter-Based Resources into Low Short Circuit Strength Systems (PDF). Atlanta, GA. <a href="https://www.nerc.com/pa/RAPA/ra/Reliability%20Assessments%20DL/Short_Circuit_whitepaper_Final_1_26_18.pdf" target="_blank">https://www.nerc.com/pa/RAPA/ra/Reliability%20Assessments%20DL/Short_Circuit_whitepaper_Final_1_26_18.pdf</a> <a href="#fnref:19" class="footnote-back-ref">↩</a></li>
<li id="fn:20">Henderson et al. 2023, p. 1. - Henderson, Callum; Egea-Alvarez, Agusti; Kneuppel, Thyge; Yang, Guangya; Xu, Lie (2023). "Grid Strength Impedance Metric: An Alternative to SCR for Evaluating System Strength in Converter Dominated Systems" (PDF). IEEE Transactions on Power Delivery. 39. Institute of Electrical and Electronics Engineers (IEEE): 386–396. doi:10.1109/tpwrd.2022.3233455. ISSN 0885-8977. S2CID 255660560. <a href="https://backend.orbit.dtu.dk/ws/portalfiles/portal/304326476/BERAT_Grid_Strength_Impedance_Metric_An_Alternative_to_SCR_for_Evaluating_System_Strength_in_Converter_Dominated_Systems.pdf" target="_blank">https://backend.orbit.dtu.dk/ws/portalfiles/portal/304326476/BERAT_Grid_Strength_Impedance_Metric_An_Alternative_to_SCR_for_Evaluating_System_Strength_in_Converter_Dominated_Systems.pdf</a> <a href="#fnref:20" class="footnote-back-ref">↩</a></li>
<li id="fn:21">Zhang et al. 2014. - Zhang, Yang; Huang, Shun-Hsien Fred; Schmall, John; Conto, Jose; Billo, Jeffrey; Rehman, Ehsan (2014). "Evaluating system strength for large-scale wind plant integration". 2014 IEEE PES General Meeting | Conference & Exposition. IEEE. pp. 1–5. doi:10.1109/pesgm.2014.6939043. ISBN 978-1-4799-6415-4. <a href="https://www.researchgate.net/publication/290732425" target="_blank">https://www.researchgate.net/publication/290732425</a> <a href="#fnref:21" class="footnote-back-ref">↩</a></li>
<li id="fn:22">Zhang et al. 2014. - Zhang, Yang; Huang, Shun-Hsien Fred; Schmall, John; Conto, Jose; Billo, Jeffrey; Rehman, Ehsan (2014). "Evaluating system strength for large-scale wind plant integration". 2014 IEEE PES General Meeting | Conference & Exposition. IEEE. pp. 1–5. doi:10.1109/pesgm.2014.6939043. ISBN 978-1-4799-6415-4. <a href="https://www.researchgate.net/publication/290732425" target="_blank">https://www.researchgate.net/publication/290732425</a> <a href="#fnref:22" class="footnote-back-ref">↩</a></li>
<li id="fn:23">Zhang et al. 2014, p. 1. - Zhang, Yang; Huang, Shun-Hsien Fred; Schmall, John; Conto, Jose; Billo, Jeffrey; Rehman, Ehsan (2014). "Evaluating system strength for large-scale wind plant integration". 2014 IEEE PES General Meeting | Conference & Exposition. IEEE. pp. 1–5. doi:10.1109/pesgm.2014.6939043. ISBN 978-1-4799-6415-4. <a href="https://www.researchgate.net/publication/290732425" target="_blank">https://www.researchgate.net/publication/290732425</a> <a href="#fnref:23" class="footnote-back-ref">↩</a></li>
<li id="fn:24">Jang, Gilsoo (2019-11-18). HVDC for Grid Services in Electric Power Systems. MDPI. ISBN 978-3-03921-762-5. <a href="978-3-03921-762-5" target="_blank">978-3-03921-762-5</a> <a href="#fnref:24" class="footnote-back-ref">↩</a></li>
</ol>

Short circuit ratio (electrical grid) open-in-new

Short circuit ratio (electrical grid)