1. KAIST NUCLEAR & QUANTUM NICIEL SEMINAR 1 / 20 A Feasibility Study on Application of Synchronous Condenser for PFC to Domestic Power System of Nuclear Power Plants Young Seung LEE 08/26/2005 SEMINAR

2. KAIST NUCLEAR & QUANTUM NICIEL SEMINAR 2 / 20 Contents Introduction On-Site Power System of Nuclear Power Generating Station IEEE Design Guide for Electric Power Service Systems for Generating Stations (IEEE Std 666-1991) Chapter 8 of IEEE Recommended Practice for Electric Power Distribution for Industrial Plants (IEEE Std 141- 1993, IEEE Red Book) Synchronous Condensers Vs Capacitors Summary Further Study References

3. KAIST NUCLEAR & QUANTUM NICIEL SEMINAR 3 / 20 Introduction Domestic consumption of electricity in a nuclear power plant is 4 ~ 7% of the electrical output and the power factor of on-site power is about 80%. Energy savings using power factor improvements are possible enough at the stations. Despite benefits of power factor correction (PFC), it is not used in the on-site power system of nuclear power generating stations. Review of IEEE standards about nuclear power generating station gives requirements, information, cautions, and problems of applying PFC to us.

4. KAIST NUCLEAR & QUANTUM NICIEL SEMINAR 4 / 20 On Site Power System of Nuclear Power Generating Station Classification by site  Off site power supply system  On site power supply system Classification by safety  Non-class 1E power system  Class 1E power system Classification by type  Alternating current power system  Direct current power system Classification by supply  Preferred power system  Standby power system

5. KAIST NUCLEAR & QUANTUM NICIEL SEMINAR 5 / 20 On Site Power System of Nuclear Power Generating Station Components of Class 1E power system

6. KAIST NUCLEAR & QUANTUM NICIEL SEMINAR 6 / 20 IEEE Design Guide for Electric Power Service Systems for Generating Stations (IEEE Std 666-1991)  General planning guide

7. KAIST NUCLEAR & QUANTUM NICIEL SEMINAR 7 / 20 IEEE Design Guide for Electric Power Service Systems for Generating Stations (IEEE Std 666-1991)  Effects of voltage variation  General effects  When the voltage at the terminals of utilization equipment deviates from the value on the nameplate of the equipment, the performance and the operating life of the equipment are affected.  Synchronous motors  Synchronous motors are affected in the same manner as induction motors, except that the speed remains constant (unless the frequency changes), and the maximum or pull-out torque varies directly with the voltage if the field voltage remains constant. If the field voltage varies with the line voltage, then the pull-out torque varies as the square of the voltage.

8. KAIST NUCLEAR & QUANTUM NICIEL SEMINAR 8 / 20 IEEE Design Guide for Electric Power Service Systems for Generating Stations (IEEE Std 666-1991)  Synchronous motor protection  The few large, low-speed, salient pole synchronous motors applied in generating stations are usually protected with methods and techniques similar to those for the large induction motors. A power factor relay is applied to protect the motor from operating below synchronous speed with the field applied. This out-of-synchronism or out-of-step operation causes pulsations in the stator current and the power factor rapidly becomes lagging. When the power factor relay senses abnormally lagging power factor, the field excitation is removed and the motor may be tripped.

9. KAIST NUCLEAR & QUANTUM NICIEL SEMINAR 9 / 20 IEEE Design Guide for Electric Power Service Systems for Generating Stations (IEEE Std 666-1991)  Synchronous motors (salient pole type)  Principles of operation  The rotor of the synchronous motor differs considerably from the induction- motor rotor.  During normal steady state operation, the rotor turns at synchronous speed, and there is no average relative motion between rotor pole and the stator flux pole.  Should the rotor be at standstill when direct current is applied to the field winding, the interaction of the stator flux and the rotor flux will provide a large oscillating torque, but the rotor will not accelerate.  To start a synchronous motor, then, it is necessary to embed a number of bars in the face of each pole and short circuit these bars at each end to form a squirrel cage similar to that found in the induction motor. Further, the field winding must be disconnected from the dc supply.  When the rotor has reached sufficient speed, direct current is applied to the field winding, and the motor pulls into step with the rotating stator flux.

10. KAIST NUCLEAR & QUANTUM NICIEL SEMINAR 10 / 20 IEEE Design Guide for Electric Power Service Systems for Generating Stations (IEEE Std 666-1991)  Synchronous motors (salient pole type)  Control and special starting considerations  There are differences in control and motor protection of the synchronous motor, relative to those for induction motors, that are related to the rotor construction. Since the dc excitation is a necessity for synchronous operation, and synchronous operation is fundamental to the synchronous motor, protection against loss of field and loss of synchronism should be provided.  During start, the control equipment must automatically and accurately ensure that the rotor speed has reached a proper value and further, in many cases, ensure that the proper angle between rotor and stator flux exists before the dc excitation is applied.

11. KAIST NUCLEAR & QUANTUM NICIEL SEMINAR 11 / 20 IEEE Design Guide for Electric Power Service Systems for Generating Stations (IEEE Std 666-1991)  Fault Considerations  AC fault current  The four basic sources of fault current on station service systems are Synchronous generators Synchronous motors and condensers Induction machines Transmission system (considered to be a constant voltage and constant impedance generator)

12. KAIST NUCLEAR & QUANTUM NICIEL SEMINAR 12 / 20 IEEE Design Guide for Electric Power Service Systems for Generating Stations (IEEE Std 666-1991)  Fault Considerations  AC fault current  Subtransient reactance, X”d X”d determines the current during the first few cycles of a fault.  Transient reactance, X’d X’d determines the machine current before steady-state conditions.  Synchronous reactance, Xd Xd determines steady-state current flow.

13. KAIST NUCLEAR & QUANTUM NICIEL SEMINAR 13 / 20 Chapter 8 of IEEE Recommended Practice for Electric Power Distribution for Industrial Plants (IEEE Std 141- 1993, IEEE Red Book)  Power Factor  Significance of power factor  Reduced power bills, release of system capacity, improved voltage, and decreased I 2 R losses.  Beneficial features and problems of Capacitors  Relatively low cost, ease of installation, minimal maintenance requirements, very low losses, and manufactures in a variety of sizes.  Sensitivity to overvoltage, impact of harmonic currents, and switching transients.  Definition of power factor  Power factor is the ratio of active power (watts) to total root-mean-squared (rms) voltamperes (apparent power).  Active power is usually less than apparent power for two reasons. Different phase and waveform Displacement power factor is the ratio of the active power of the fundamental wave to the apparent power of the fundamental wave. This is the cosine of the phase angle by which the fundamental current lags (or leads) the fundamental voltage. Distortion power factor is the ratio of the fundamental circuit current to the total root-mean- squared current. This ratio will be less than unity whenever there are nonlinear loads supplied by the circuit. While displacement power factor can be improved by adding a source of vars, distortion power factor can only be improved by filtering the harmonic currents.

14. KAIST NUCLEAR & QUANTUM NICIEL SEMINAR 14 / 20 Chapter 8 of IEEE Recommended Practice for Electric Power Distribution for Industrial Plants (IEEE Std 141- 1993, IEEE Red Book)  Power Factor  Definition of power factor (continued) 

15. KAIST NUCLEAR & QUANTUM NICIEL SEMINAR 15 / 20 Chapter 8 of IEEE Recommended Practice for Electric Power Distribution for Industrial Plants (IEEE Std 141- 1993, IEEE Red Book)  Typically unimproved power factor values

16. KAIST NUCLEAR & QUANTUM NICIEL SEMINAR 16 / 20 Chapter 8 of IEEE Recommended Practice for Electric Power Distribution for Industrial Plants (IEEE Std 141- 1993, IEEE Red Book)  Equations related to Power Factor  Reactive power required to improve the power factor   Voltage improvement   Power system losses   Release of system capacity 

17. KAIST NUCLEAR & QUANTUM NICIEL SEMINAR 17 / 20 Synchronous Condensers Vs Capacitors  Principal advantage of synchronous condensers is the ease with which the amount of correction could be adjusted.  Synchronous condensers (SC) are capable of supplying kvars equal to its rating to the system as well as absorbing up to 50% of its rating.  SCs allow for a finer adjustment to changes in the load.  SCs can be overloaded for short periods of time, whereas this is not the case for capacitors.  Capacitors have lower losses than SCs.  SCs add to the short-circuit of a system current of a system and may increase the size of the breakers required.  Switching capacitor banks can cause transient and harmonic problems.

18. KAIST NUCLEAR & QUANTUM NICIEL SEMINAR 18 / 20 Summary On-site power system of nuclear power generating stations is made up of main generator, transformers (UAT, SST, MOT), uninterruptible power supply (UPS), standby diesel generators, buses, protective system, circuit breakers, etc.. General design guide was reviewed on electrical power service systems for generating stations through IEEE Std 666-1991. Also, items related to power factor were obtained at IEEE Std 141-1993. benefits were estimated according to power factor improvement by using the data of Wolsong #2. Characteristics of Synchronous condensers were compared with those of capacitors. Nonlinear loads such as UPS exist in the on-site power system of nuclear power generating stations, and it is the reason why I choose synchronous condensers as the method of power factor correction. The synchronous condenser is a source of fault current. Therefore, analysis of fault current is needed.

19. KAIST NUCLEAR & QUANTUM NICIEL SEMINAR 19 / 20 Further Study I want to demonstrate merits of synchronous condensers for power factor improvement, using simulation program like ETAP Powerstation, developed by Operation Technology Inc.. I will show that the method reduces harmonic problems in comparison with capacitors. I want to perform the analysis of short-circuit current for breaking capacity.

20. KAIST NUCLEAR & QUANTUM NICIEL SEMINAR 20 / 20 References IEEE Standards related to Nuclear Power Generating Station IEEE Std 308-2001, IEEE Standard Criteria for Class 1E Power Systems for Nuclear Power Generating Stations IEEE Std 741-1997, IEEE Standard Criteria for Protection of Class 1E Power Systems and Equipment in Nuclear Power Generating Stations IEEE Std 379-2000, IEEE Standard Application of the Single-Failure Criterion to Nuclear Power Generating Station Safety Systems IEEE Std 384-1992, IEEE Standard Criteria for Independence of Class 1E Equipment and Circuits IEEE Std 577-2004, IEEE Standard Requirements for Reliability Analysis in the Design and Operation of Safety Systems for Nuclear Facilities IEEE Std 946-2004, IEEE Recommended Practice for the Design of DC Auxiliary Power Systems for Generating Stations IEEE Std 765-2002, IEEE Standard for Preferred Power Supply (PPS) for Nuclear Power Generating Stations IEEE Std 603-1998, IEEE Standard Criteria for Nuclear Power Generating Stations IEEE Std 690-2004, IEEE Standard for the Design and Installation of Cable Systems for Class 1E Circuits in Nuclear Power Generating Stations IEEE Standards related to Electricity IEEE Std 141-1993, IEEE Recommended Practice for Electric Power Distribution for Industrial Plants (IEEE Red Book) IEEE Std 142-1991, IEEE Recommended Practice for Grounding of Industrial and Commercial Power Systems (IEEE Green Book) IIEEE Std 241-1990, IEEE Recommended Practice for Power Systems in Commercial Buildings (IEEE Gray Book) IEEE Std 242-2001, IEEE Recommended Practice for Protection and Coordination of Industrial and Commercial Power Systems (IEEE Buff Book) IEEE Std 399-1997, IEEE Recommended Practice for Industrial and Commercial Power System Analysis (IEEE Brown Book) IEEE Std 446-1995, IEEE Recommended Practice for Emergency and Standby Power Systems for Industrial and Commercial Applications (IEEE Orange Book) IEEE Std 493-1997, IEEE Recommended Practice for the Design of Reliable Industrial and Commercial Power Systems (IEEE Gold Book) IEEE Std 602-1996, IEEE Recommended Practice for Electric Systems in Health Care Facilities (IEEE White Book) IEEE Std 739-1995, IEEE Recommended Practice for Energy Conservation and Cost Effective Planning in Industrial Facilities (IEEE Bronze Book) IEEE Std 1100-1999, IEEE Recommended Practice for Powering and Grounding Sensitive Electronic Equipment (IEEE Emerald Book) IEEE Std 666-1991, IEEE Design Guide for Electric Power Service Systems for Generating Stations