Tutorial on Shunt Capacitor Banks Design, Application and Protection Considerations Presenter: Pratap Mysore, HDR Minnesota Power Systems Conference November 12, 2015 Topics Covered . Power system Considerations, Capacitor Benefits . Capacitor Ratings, Capabilities and Service Conditions Shunt Shunt . Capacitor Unit Construction and failure mode - . Bank Design, Connections and Configuration . Sizing of Capacitor Banks Tutorial Bank Capacitor MIPSYCON_2015 MIPSYCON_2015 . MVAR sizing . Voltage Rating . Insulation requirement 2 Topics Covered .Switching Transients .Single Bank Switching .Back to Back Switching Shunt Shunt .Voltage Magnification - .Resonance Issues Capacitor Bank Tutorial Bank Capacitor .Use of Current Limiting Reactor MIPSYCON_2015 .Sizing .Switching Issues 3 Topics Covered .Switching Devices .Circuit Breaker .Circuit Switcher Shunt Shunt - . Bank Protection Capacitor Bank Tutorial Bank Capacitor .System Protection VS Bank Protection MIPSYCON_2015 .Unbalance Protection Methods 4 Tutorial Reference Materials . IEEE Std. 18-2012* – IEEE Standard for Shunt Power Capacitors. IEEE 1036-2010* – IEEE Guide for the application of Shunt Power Capacitors. PES-TR16*; Technical Report, “Transient Limiting Shunt Shunt Inductor Applications in Shunt Capacitor Banks” - * Document developed under Capacitor Subcommittee of Transmission and Distribution Committee Capacitor Bank Tutorial Bank Capacitor . C37.99 2012# – IEEE guide for the Protection of MIPSYCON_2015 Shunt capacitor Banks # Document developed under IEEE Power Systems Relaying Committee (Will soon be Power Systems Relaying and Control Committee) 5 IEEE Reference Documents . IEEE Std18TM - 2012: IEEE Standard for Shunt Power Capacitors - Revised and approved for publication on 5th December 2012 – Published on 15 February 2013. This standard provides a basis for uniformity in Shunt design, manufacturing and testing of shunt power - capacitors. Capacitor Bank Tutorial Bank Capacitor . The revision included portions of NEMA CP1 MIPSYCON_2015 document. The ratings and capabilities remain the same as 2002 version. 6 IEEE Reference Documents . IEEE 1036TM-2010 – IEEE Guide for the Application Shunt Power- under revision. Provides guidelines for the application, protection, and ratings of equipment for the Shunt Shunt safe and reliable utilization of shunt power - capacitors. Capacitor Bank Tutorial Bank Capacitor MIPSYCON_2015 MIPSYCON_2015 7 IEEE Reference Documents . C37.99 -2012; IEEE Guide for the Protection of Shunt Capacitor Banks . Revisiting analog relays technologies for the application of digital relays technologies for the protection of externally fused, internally fused, fuseless and unfused capacitor Shunt Shunt banks. - . Added theory and analysis of unbalance relaying methods. Massive editorial changes. Capacitor Bank Tutorial Bank Capacitor . Minimized bank grounding section directing references to MIPSYCON_2015 IEEE 1036. 8 IEEE Reference Documents . Technical Report PES-TR16 -2014 As Stated in the document, “The report was written in response to a great amount of confusion in the power industry surrounding the application of Transient limiting Inductors in shunt Shunt Shunt capacitor banks”. - Capacitor Bank Tutorial Bank Capacitor MIPSYCON_2015 MIPSYCON_2015 9 Other IEEE Documents . NEMA CP 1-2000 (R2008), Shunt Capacitors . Portions of this document was incorporated in the Latest revision of IEEE-18. IEEE Std. C37.48-2005 (R2010) IEEE Guide for Shunt Application, Operation, and Maintenance of High- - Voltage Fuses, Distribution Enclosed Single-Pole Air Switches, Fuse Disconnecting Switches, and Tutorial Capacitor Bank Accessories MIPSYCON_2015 10 Reactive Compensation . Allows System voltage levels to stay within the acceptable limits Shunt Shunt .Permits the maximum utilization of - transmission circuits Capacitor Bank Tutorial Bank Capacitor MIPSYCON_2015 MIPSYCON_2015 11 Long Transmission line • Represented as a series of inductor/ Capacitor elements VS VR Shunt Shunt . Voltage and Current at any point x on the - transmission line is given by: Capacitor Bank Tutorial Bank Capacitor .V(x) = VR cos(L-x) +jZ0IRsin (L-x) MIPSYCON_2015 .I(x) = IR cos(L-x) +j[VR/Z0]sin (L-x) 12 Terms used in Transmission wave equations • =(LC) = Phase constant Typically 2.07x 10-3 radians/mile • Z0 = (L/C) = Surge Impedance of the line – ~ 450 Shunt Shunt for single conductor (230 kV and below) and - around ~ 280 for bundled conductor (345 and higher) Capacitor Bank Tutorial Bank Capacitor MIPSYCON_2015 MIPSYCON_2015 • Charging KVAR/ Mile – ~ 900 @ 345 kV; ~ 270 @ 230 kV and around ~ 70 @ 115 kV • Inductive reactance – 0.5-0.8 ohms/mile 13 Receiving End Voltage of an Unloaded Line . VR = VS/Cos L ; . For a 300 mile 500 kV line, the receiving end voltage = 1.0/COS(2.07x10-3x300) Shunt Shunt . Angle = 2.07x10-3x300 radians =0.621radians =35.60 - . VR = 1.229P.U. Remote end voltage is 130% of the nominal. Tutorial Bank Capacitor MIPSYCON_2015 MIPSYCON_2015 14 Line Voltage and Charging Current V X Shunt Shunt - Line Length Capacitor Bank Tutorial Bank Capacitor MIPSYCON_2015 MIPSYCON_2015 IX Line Length 15 Surge Impedance Loading • If the line is terminated with impedance Z0, VR=IRZ0 j(l-x) • V(x) = VR [cos(L-x) +jsin (L-x)] =VRe Shunt Shunt . The magnitudes of voltage at any point of the line - is independent of the position, x Capacitor Bank Tutorial Bank Capacitor MIPSYCON_2015 MIPSYCON_2015 16 Voltage Profile of a Loaded Line P<P0 1.0 P=P0 VR = controlled to 1.0 P.U. P>P0 Shunt Shunt x - 2 Voltage Surge SI Loading [V /Z0] Capacitor Bank Tutorial Bank Capacitor Impedance,Z0 MIPSYCON_2015 345 kV 285 425 MVA (711Amps) 500 kV 285 877 MVA (1013 Amps) 17 P-V, V-Q Curves Operating Point 105% 0.9 Lead Unity PF VR Stable voltage Region Q Shunt Shunt VC - (70%) Unstable voltage Point of voltage Region instability Bus Voltage PCritical Tutorial Bank Capacitor Power MVAR required to Keep MIPSYCON_2015 the bus voltage at a level (ex:1.05) at specified power transfer 18 Shunt Reactor and Shunt Capacitor • Compensate the effect of capacitive/ inductive currents • Shunt Capacitors raise the system voltage – Shunt Reactors lower the bus voltage Shunt Shunt • During light load periods, shunt reactors are used - to control the system voltage • During heavy load periods, shunt capacitors are Tutorial Bank Capacitor used to maintain the system voltage MIPSYCON_2015 19 Application of Shunt Capacitor Banks . To provide local voltage support . Banks are switched when voltage falls below a set value. (15 -20 sec) . To provide system voltage support for higher power transfer Shunt Shunt - . To Provide fast switching to prevent voltage collapse or voltage excursions– (Poor man’s SVC s) (switching Capacitor Bank Tutorial Bank Capacitor time in cycles) MIPSYCON_2015 20 Shunt Capacitor Bank Function . Var support (local Voltage Support). Capacitors supply the reactive power and reduce losses by reducing the current on equipment such as transmission lines. Shunt Shunt - 2000A 2000 +j1000A 0.89 pf Load 2236 A Capacitor Bank Tutorial Bank Capacitor (without capacitor) j1000A MIPSYCON_2015 21 Size and number of capacitor banks . Maximum bank size is influenced by: . Change in system voltage upon capacitor bank switching . Switchgear continuous current limitation . Minimum bank size is influenced by: Shunt Shunt . The type of capacitor bank used: externally fused, - internally fused, fuseless, etc. Capacitor Bank Tutorial Bank Capacitor . The easily available ratings of capacitor units MIPSYCON_2015 . Capacitor bank unbalance considerations . Fuse performance and/or coordination 22 . The cost of the required switchgear and protection Size and Number of Capacitor Banks Capacitor bank sized so that the system voltage will not change more than 3% during switching ( GE flicker curve) I Q M var V C c Shunt Shunt - I SC Ssc Mva It is important to know the application of Capacitor Capacitor Bank Tutorial Bank Capacitor Bank MIPSYCON_2015 - for Local voltage support under contingencies (loss of a source) 23 - for System Support during through flow. Capacitor Unit Ratings As Per IEEE Std. 18 Standard ratings IEEE Std 18-2012 establishes ratings for the following electrical parameters Shunt Shunt . Voltage, rms (terminal-to-terminal) - . Reactive power Capacitor Bank Tutorial Bank Capacitor . Number of phases MIPSYCON_2015 . Frequency . Terminal(s)-to-case (or ground) insulation class 24 Capacitor Unit Ratings . Voltage - RMS (continuous): 110% of the rated value Crest Voltage 120% of the peak value including harmonics . Current - 135% of nominal rating including Shunt Shunt Harmonics - . VAR: -0 to +10% of the rated value ( +15% for units manufactured before the year 2000) Tutorial Bank Capacitor measured at 25 deg.C MIPSYCON_2015 . Temperature - -40 deg. C to +40 deg. C . Max. continuous reactive output - 135% of the 25 rated value Capacitor Unit Overvoltage Limit Reference - NEMA CP1-2000 and IEEE 1036 Voltage Duration (Percentage of Rated) 110% Continuous Shunt - 125% 30 minutes 130% 1 minute Capacitor Bank Tutorial Bank Capacitor 140% 15 seconds MIPSYCON_2015 170% 1 second 200% 15 cycles 220% 6 cycles 26 Capacitor Transient overvoltage Limit Momentary capabilities, transient peak overvoltage 4.0 3.5 3.0 voltage) Shunt Shunt - 2.5 2.0 Capacitor Bank Tutorial Bank Capacitor Peak voltage of voltage rated Peakcrestunit of (Per MIPSYCON_2015 MIPSYCON_2015 1.5 1 10 100 1000 10000 Number of transients per year 27 Source: IEEE 1036 Effect of Geomagnetically Induced Currents . GIC is quasi-DC