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Voltage sag
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<h2 id="voltage-sag-in-large-power-system">Voltage sag in large power system</h2> <p>The main goal of the <a href="/facts/Power_system/ruyJzGVv">power system</a> is to provide reliable and high-quality electricity for its customers. One of the main measures of <a href="/facts/Power_quality/DS6bH6Nh">power quality</a> is the voltage magnitude. Therefore, Monitoring the power system to ensure its performance is one of the highest priorities.<a class="footnote-ref" id="fnref:10" href="#fn:10"><sup>10</sup></a> However, since power systems are usually grids including hundreds of <a href="/facts/Busbar/Mdm9AF1S">buses</a>, installing measuring instruments at every single <a href="/facts/Busbar/Mdm9AF1S">busbar</a> of the system is not cost-efficient. In this regard, various approaches have been suggested to estimate the voltage of different buses merely based on the measured voltage on a few buses.<a class="footnote-ref" id="fnref:11" href="#fn:11"><sup>11</sup></a> </p> <h2 id="related-concepts">Related concepts</h2> <p>The term <i>sag</i> should not be confused with a <a href="/facts/Brownout_(electricity)/EWdljcgw">brownout</a>, which is the reduction of voltage for minutes or hours.<a class="footnote-ref" id="fnref:12" href="#fn:12"><sup>12</sup></a> </p><p>The term <i>transient</i>, as used in <a href="/facts/Power_quality/DS6bH6Nh">power quality</a>, is an <a href="/facts/Umbrella_term/bjxUuoRb">umbrella term</a> and can refer to sags, swells, dropouts, etc.<a class="footnote-ref" id="fnref:13" href="#fn:13"><sup>13</sup></a> </p> <h2 id="swell">Swell</h2> <p class="note">See also: <a href="/facts/Voltage_spike/XYdAJkje">Voltage spike</a></p> <p>Voltage swell is the opposite of voltage sag. Voltage swell, which is a momentary increase in voltage, happens when a heavy load turns off in a power system.<a class="footnote-ref" id="fnref:14" href="#fn:14"><sup>14</sup></a> </p> <h2 id="causes">Causes</h2> <p>Several factors can cause a voltage sag: </p> <ul><li>Some electric motors draw much more current when they are starting than when they are running at their rated speed.<a class="footnote-ref" id="fnref:15" href="#fn:15"><sup>15</sup></a><a class="footnote-ref" id="fnref:16" href="#fn:16"><sup>16</sup></a></li> <li>A line-to-ground fault will cause a voltage sag until the protective <a href="/facts/Switchgear/Yuxo2FIW">switchgear</a> (<a href="/facts/Fuse_(electrical)/xN78ylMS">fuse</a> or <a href="/facts/Circuit_breaker/vbw6cWSe">circuit breaker</a>) operates.<a class="footnote-ref" id="fnref:17" href="#fn:17"><sup>17</sup></a><a class="footnote-ref" id="fnref:18" href="#fn:18"><sup>18</sup></a></li> <li>Some accidents in <a href="/facts/Power_line/jULhrQNv">power lines</a> such as <a href="/facts/Lightning/dLTuxz8n">lightning</a> or a falling object can cause a line-to-ground fault.<a class="footnote-ref" id="fnref:19" href="#fn:19"><sup>19</sup></a></li> <li>Sudden load changes or excessive loads<a class="footnote-ref" id="fnref:20" href="#fn:20"><sup>20</sup></a></li> <li>Depending on the <a href="/facts/Transformer/EYYfXWrF">transformer</a> connections, transformers energizing<a class="footnote-ref" id="fnref:21" href="#fn:21"><sup>21</sup></a></li> <li>Voltage sags can arrive from the power utility, but most are caused by local in-building equipment. In residential homes, voltage sags are sometimes seen when refrigerators, air-conditioners, or furnace fans start up.</li></ul> <p>Factors that affect the magnitude of sag caused by faults: </p> <ul><li>The distance between the victim and the fault source <a class="footnote-ref" id="fnref:22" href="#fn:22"><sup>22</sup></a></li> <li>The fault impedance<a class="footnote-ref" id="fnref:23" href="#fn:23"><sup>23</sup></a></li> <li>Type of fault<a class="footnote-ref" id="fnref:24" href="#fn:24"><sup>24</sup></a></li> <li>The voltage before the sag occurs<a class="footnote-ref" id="fnref:25" href="#fn:25"><sup>25</sup></a></li> <li>System configuration, e.g. system impedance and transformer connections<a class="footnote-ref" id="fnref:26" href="#fn:26"><sup>26</sup></a></li></ul> <h2 id="see-also">See also</h2> <ul><li><a href="/facts/Low_voltage_ride_through/5LUBLc3D">Low voltage ride through</a> – Electric generator function (LVRT)</li> <li><a href="/facts/Supply_voltage_sag/DENdhdUJ">Supply voltage sag</a> – the gate voltage appearing less than ground during transistor switchingPages displaying wikidata descriptions as a fallback</li> <li><a href="/facts/Voltage_spike/XYdAJkje">Voltage spike</a> – Short duration voltage transient in an electrical circuit</li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>"IEEE 493-2007 - IEEE Recommended Practice for the Design of Reliable Industrial and Commercial Power Systems". The IEEE Standards Association. 2007-02-12. Archived from the original on March 25, 2022. Retrieved 2018-01-09. <a href="https://web.archive.org/web/20220325112732/https://standards.ieee.org/ieee/493/3402/" target="_blank">https://web.archive.org/web/20220325112732/https://standards.ieee.org/ieee/493/3402/</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>Bollen, Math H.J. (1999). Solving power quality problems: voltage sags and interruptions. New York: IEEE Press. p. 139. ISBN 978-0-7803-4713-7. <a href="978-0-7803-4713-7" target="_blank">978-0-7803-4713-7</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>Karady, George. "Effect of voltage sags on loads in a distribution system" (PDF). <a href="https://pserc.wisc.edu/wp-content/uploads/sites/755/2018/08/T-16_Final-Report_Oct-2005.pdf" target="_blank">https://pserc.wisc.edu/wp-content/uploads/sites/755/2018/08/T-16_Final-Report_Oct-2005.pdf</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>Bollen, Math H.J. (1999). Solving power quality problems: voltage sags and interruptions. New York: IEEE Press. p. 139. ISBN 978-0-7803-4713-7. <a href="978-0-7803-4713-7" target="_blank">978-0-7803-4713-7</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>"Industrial Voltage Regulator Power Conditioner". Utility Systems Technologies. Retrieved 25 September 2013. <a href="http://www.ustpower.com/Support/SupportKnowledgeBase/KnowledgeBasePowerQualityProblems/Sag_Dip.aspx" target="_blank">http://www.ustpower.com/Support/SupportKnowledgeBase/KnowledgeBasePowerQualityProblems/Sag_Dip.aspx</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> <li id="fn:6"><p>Vijayaraghavan, G, Mark Brown, and Malcolm Barnes (2004). Practical grounding, bonding, shielding and surge protection. Oxford: Newnes. p. 134. ISBN 978-0-08-048018-3.{{cite book}}: CS1 maint: multiple names: authors list (link) <a href="978-0-08-048018-3" target="_blank">978-0-08-048018-3</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li> <li id="fn:7"><p>Remus Teodorescu; Marco Liserre; Pedro Rodríguez (2011). Grid Converters for Photovoltaic and Wind Power Systems. Wiley-IEEE Press. ISBN 978-1-119-95720-1. <a href="978-1-119-95720-1" target="_blank">978-1-119-95720-1</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li> <li id="fn:8"><p>Vijayaraghavan, G, Mark Brown, and Malcolm Barnes (2004). Practical grounding, bonding, shielding and surge protection. Oxford: Newnes. p. 134. ISBN 978-0-08-048018-3.{{cite book}}: CS1 maint: multiple names: authors list (link) <a href="978-0-08-048018-3" target="_blank">978-0-08-048018-3</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></p></li> <li id="fn:9"><p>Karady, George. "Effect of voltage sags on loads in a distribution system" (PDF). <a href="https://pserc.wisc.edu/wp-content/uploads/sites/755/2018/08/T-16_Final-Report_Oct-2005.pdf" target="_blank">https://pserc.wisc.edu/wp-content/uploads/sites/755/2018/08/T-16_Final-Report_Oct-2005.pdf</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></p></li> <li id="fn:10"><p>Association IS (2014) IEEE trial-use recommended practice for voltage sag and short interruption ride-through testing for end-use electrical equipment rated less than 1000V. Standard P1668-2014 <a href="#fnref:10" class="footnote-back-ref">↩</a></p></li> <li id="fn:11"><p>Jalalat, Hamed; Liasi, Sahand (2022-11-16). "Optimal location of voltage sags monitoring buses, based on the correlation rate between network buses with considering the probability distribution of variables". Electrical Engineering. 105. Springer Science and Business Media LLC: 509–518. doi:10.1007/s00202-022-01674-6. ISSN 0948-7921. S2CID 253619994. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:11" class="footnote-back-ref">↩</a></p></li> <li id="fn:12"><p>Standler, Ronald B. (1989). Protection of electronic circuits from overvoltages. New York: Wiley. p. 40. ISBN 9780471611219. <a href="9780471611219" target="_blank">9780471611219</a> <a href="#fnref:12" class="footnote-back-ref">↩</a></p></li> <li id="fn:13"><p>R. Sastry Vedam; Mulukutla S. Sarma (2008). Power Quality: VAR Compensation in Power Systems. CRC Press. pp. 4–5 and 23. ISBN 978-1-4200-6482-7. <a href="978-1-4200-6482-7" target="_blank">978-1-4200-6482-7</a> <a href="#fnref:13" class="footnote-back-ref">↩</a></p></li> <li id="fn:14"><p>Kazibwe, Wilson E.; Sendaula, Musoke H. (1993). Electric power quality control techniques. New York: Van Nostrand Reinhold. p. 11. ISBN 978-0-442-01093-5. <a href="978-0-442-01093-5" target="_blank">978-0-442-01093-5</a> <a href="#fnref:14" class="footnote-back-ref">↩</a></p></li> <li id="fn:15"><p>Bollen, Math H.J. (1999). Solving power quality problems: voltage sags and interruptions. New York: IEEE Press. p. 139. ISBN 978-0-7803-4713-7. <a href="978-0-7803-4713-7" target="_blank">978-0-7803-4713-7</a> <a href="#fnref:15" class="footnote-back-ref">↩</a></p></li> <li id="fn:16"><p>Kazibwe, Wilson E.; Sendaula, Musoke H. (1993). Electric power quality control techniques. New York: Van Nostrand Reinhold. p. 11. ISBN 978-0-442-01093-5. <a href="978-0-442-01093-5" target="_blank">978-0-442-01093-5</a> <a href="#fnref:16" class="footnote-back-ref">↩</a></p></li> <li id="fn:17"><p>Bollen, Math H.J. (1999). Solving power quality problems: voltage sags and interruptions. New York: IEEE Press. p. 139. ISBN 978-0-7803-4713-7. <a href="978-0-7803-4713-7" target="_blank">978-0-7803-4713-7</a> <a href="#fnref:17" class="footnote-back-ref">↩</a></p></li> <li id="fn:18"><p>Kazibwe, Wilson E.; Sendaula, Musoke H. (1993). Electric power quality control techniques. New York: Van Nostrand Reinhold. p. 11. ISBN 978-0-442-01093-5. <a href="978-0-442-01093-5" target="_blank">978-0-442-01093-5</a> <a href="#fnref:18" class="footnote-back-ref">↩</a></p></li> <li id="fn:19"><p>Kazibwe, Wilson E.; Sendaula, Musoke H. (1993). Electric power quality control techniques. New York: Van Nostrand Reinhold. p. 11. ISBN 978-0-442-01093-5. <a href="978-0-442-01093-5" target="_blank">978-0-442-01093-5</a> <a href="#fnref:19" class="footnote-back-ref">↩</a></p></li> <li id="fn:20"><p>Kazibwe, Wilson E.; Sendaula, Musoke H. (1993). Electric power quality control techniques. New York: Van Nostrand Reinhold. p. 11. ISBN 978-0-442-01093-5. <a href="978-0-442-01093-5" target="_blank">978-0-442-01093-5</a> <a href="#fnref:20" class="footnote-back-ref">↩</a></p></li> <li id="fn:21"><p>Remus Teodorescu; Marco Liserre; Pedro Rodríguez (2011). Grid Converters for Photovoltaic and Wind Power Systems. Wiley-IEEE Press. ISBN 978-1-119-95720-1. <a href="978-1-119-95720-1" target="_blank">978-1-119-95720-1</a> <a href="#fnref:21" class="footnote-back-ref">↩</a></p></li> <li id="fn:22"><p>Karady, George. "Effect of voltage sags on loads in a distribution system" (PDF). <a href="https://pserc.wisc.edu/wp-content/uploads/sites/755/2018/08/T-16_Final-Report_Oct-2005.pdf" target="_blank">https://pserc.wisc.edu/wp-content/uploads/sites/755/2018/08/T-16_Final-Report_Oct-2005.pdf</a> <a href="#fnref:22" class="footnote-back-ref">↩</a></p></li> <li id="fn:23"><p>Karady, George. "Effect of voltage sags on loads in a distribution system" (PDF). <a href="https://pserc.wisc.edu/wp-content/uploads/sites/755/2018/08/T-16_Final-Report_Oct-2005.pdf" target="_blank">https://pserc.wisc.edu/wp-content/uploads/sites/755/2018/08/T-16_Final-Report_Oct-2005.pdf</a> <a href="#fnref:23" class="footnote-back-ref">↩</a></p></li> <li id="fn:24"><p>Karady, George. "Effect of voltage sags on loads in a distribution system" (PDF). <a href="https://pserc.wisc.edu/wp-content/uploads/sites/755/2018/08/T-16_Final-Report_Oct-2005.pdf" target="_blank">https://pserc.wisc.edu/wp-content/uploads/sites/755/2018/08/T-16_Final-Report_Oct-2005.pdf</a> <a href="#fnref:24" class="footnote-back-ref">↩</a></p></li> <li id="fn:25"><p>Karady, George. "Effect of voltage sags on loads in a distribution system" (PDF). <a href="https://pserc.wisc.edu/wp-content/uploads/sites/755/2018/08/T-16_Final-Report_Oct-2005.pdf" target="_blank">https://pserc.wisc.edu/wp-content/uploads/sites/755/2018/08/T-16_Final-Report_Oct-2005.pdf</a> <a href="#fnref:25" class="footnote-back-ref">↩</a></p></li> <li id="fn:26"><p>Karady, George. "Effect of voltage sags on loads in a distribution system" (PDF). <a href="https://pserc.wisc.edu/wp-content/uploads/sites/755/2018/08/T-16_Final-Report_Oct-2005.pdf" target="_blank">https://pserc.wisc.edu/wp-content/uploads/sites/755/2018/08/T-16_Final-Report_Oct-2005.pdf</a> <a href="#fnref:26" class="footnote-back-ref">↩</a></p></li> </ol>