ML20072P579

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Power System Harmonic Study for Peach Bottom Nuclear Power Plant, Final Rept
ML20072P579
Person / Time
Site: Peach Bottom  Constellation icon.png
Issue date: 08/26/1994
From: Schlake R, Steciuk P
GENERAL ELECTRIC CO.
To:
Shared Package
ML20072P577 List:
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NUDOCS 9409080058
Download: ML20072P579 (18)
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{{#Wiki_filter:_ _ _ ( Final Repdrt POWER SYSTEM HAhMONIC STUDY l . l FOR i PEACH BOTTOM NUCLEAR POWER PLANT , i i PREPARE 0: BY: PETER A. ST8CIUK RANDALL L Sd, HLAKE 

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Table of Contents c Section Topic fast

1. INTRODUCTION 1
2. SYSTEM MODELING AND DATA 5
3. HARMONIC ANALYSIS AND RESULTS 9
4. CONCLUSIONS 15
5. RECOMMENDATIONS 16 Appendix 1: Design Specifications Provided by GEDS Appendix 2: Data Provided by PECO Appendix 3: Harmonic Analysis Results Appendix 3.1: Harmonic Analysis Results at 100% ASD Speed Appendix 3.2: Hannonic Analysis Results at 80% ASD Speed Appendix 3.3: Hannonic Analysis Results at 60% ASD Speed Appendix 3.4: Harmonic Analysis Results at 40% ASD Speed AUG 26 '94 17:37 510 385 7067 PAGE.002

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Section 1 INTRODUCTION . The Peach Bottom Nuclear Power Plant, owned and operated by Philadelphia Electric ~  ; Company (PECO), is comprised of two 1280 MW generating units. Each unit employs  ; two 8000 hp variable speed recirculation pumps (total of 4 pumps) which have been powered by 9000 hp motor-generator (M-G) sets since the units were originally installed. Maintenance costs associated with the M-G sets are a matter of concem to PECO,  ; resulting in their planned replacement by 8250 hp static adjustable speed drive (/,CD) ' equipment. Since static motor drives do not draw purely sinusoidal load currents frem the AC supply system, the issue of power system harmonic distortion arises. Power system harmonics are sustained currents and voltages having frequencies which are whole number multiples of the base system operating frequency and come about as a result of the non-linear characteristics of power system loads. One major source of t harmonics in modern industrial power systems is the solid state, phase controlled, line commutated, ac-dc converter, such as the rectifier portion of the proposed ASD . 4 equipment. A simplified view of such a device is that it creates de by drawing power selectively on a phase-by-phase basis from the ac supply. Through the action of the full- ' wave rectifier, nonsinusoidal alternating current is typically drawn from the ac power -  ; i system. , The waveform of the input current drawn by a static device depends upon the type of

power converter employed. . De motor controllers typicaUy produce a constant de output current, under steady load conditions, which results in a square wave input current. ,

Although variable frequency ac output currents are generated by the proposed ASD drives, they typically draw nearly square wave input currents from the supply system, due , s to the smoothing effects of the de link within the drive. Other types ofvariable 

                           ' frequency ac drives or de drives which do not supply constant output current may draw heavily distorted input currents. In any case, Fourier analysis allows these steady state            '

F nonsinusoidalinput currents to be described as the sum of a series of harmonic sinusoidal components.' Since power system generators produce mainly the fundamental frequency { ; and only the fundamental component carries usable energy, it is pretty accurate to ' describe nonlinear loads as sources of harmonic current injection into the system. i 1 'i 

                        ' AUG.2B '94_17:37                                                          518 385 7067     PAGE.003 c        ,_

        ^
           . . [G The typical square wave input current can be reduced into a Fourier series consisting of the fundamental plus all odd harmonics. In the most general case of balanced three phase ,

drives, the third harmonic component and its multiples disappear leaving only the first, fifth, seventh, eleventh, etc. In more complex drive configurations (i.e.,12-pulse) some of these components can be reduced through cancellation. Since Kirchoffs laws always apply, harmonic currents which are injected into the system will circulate and must be dealt with by power systems engineers. Although hannonic currents are injected by many types ofloads, they are often not really harmful. It is true that the presence of harmonic currents causes the heating value current to be greater than the fundamental frequency load current, but the difference is nonnally small. The theoretical maximum value of each of the harmonic currents in a pure square wave is equal to the inverse of the harmonic order. Thus, on a typical three phase, six pulse, de drive, the effective, or " root sum square (RSS)", current will be only 4% greater than the fundamental component: l e = SQRT(1 2+ (1/5)2 + (1/7)2 + (1/11)2 + (1/13)2 + , , , ) - 1,04 St.ch harmonics are unlikely to cause a conventional thermal problem unless power distribution equipment is loaded at near rated levels. In such cases, the effects of harmonic losses must be taken into account and power delivery equipment may need to be derated. However, major thermal problems are uncommon unless something happens to amplify some of the effects of one or more harmonic components. The inclusion of capacitors for power factor improvement creates an RLC network which will exhibit one or more natural frequencies of oscillation. The previously mentioned harmonic currents may excite natural resonances in the system, thereby being amplified - and possibly causing significant thermal problems. Two general types of resonant conditions may be encountered: Series resonance - for which the equivalent impedance of the network approaches zero and excessive through currents can flow causing problems due to 12R heating of network elements. Parallel resonance - for which the equivalent impedance of the network approaches infinity. Heavy cunents build up within the system and severe voltage distortion can result from even a small injected harmonic current. 2 l AUG 26 '94 17:38 518 385 7067 PAGE.004 _m_ _m___._.___ --_ __--__-_.-_______-______.-.m.m .m.__._____-__ ._..-_.__

' (. _ .0n It is obvious that system resonance should be avoided at harmonic current injection frequencies. However, harmonic currents simultaneously injected by a muaber of sources can cause trouble when flowing into the system even in the absence oflocal resonance. For this reason, limits have been established regarding the voltage and current , distortion present at the point of common coupling between industrial plants and host utilities. Industry experience has also led to recommended limits regarding the harmonic distortion ofin-plant bus voltages to insure the proper operation of typical voltage ' sensitive load equipment. Drives and other non-linear loads inexorably inject harmonics into the plant power system. The need is to control how these currents circulate within the system so as to minimize their adverse effects and meet harmonic distortion requirements. This control is usually achieved through the application of so-called " harmonic filters". Harmonic filters are shunt-connected power capacitors which have been " tuned" by the addition of a i small series inductance so that the effective impedance of the shunt path at some >

harmonic frequency is very low. The low shunt impedance does two things
                          . It provides a preferred, controlled path for harmonic current circulation thus
reducing and/or rninimiring the hannonic current flow in the principal circuit  ;

4 of the system. 

                          . It greatly limits the range of harmonic frequencies over which harmonic                    +

resonance can occur with associated amplified harmonic currents and voltages.  : i t At the same time, filters are designed such that fundamental frequency VAR ^ requirements are also met. For a capacitor bank to serve reliablyin an harmonie filter, it must be specifically designed for that purpose; this requires that the capacitor bank have substantially higher voltage capability than a " standard" capacitor bank. Capacitors in an harmonic filter are

subjected to more than nominal system voltage, and so existing unfiltered capacitors probably cannot be converted to harmonic filters. It is also generally the case that an harmonic filter designed to accomplish a power factor improvement objective will have a higher nominal VAR rating than one designed solely as an harmonic filter.

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To control the propagation and effects of these currents,13,8 kV harmonic filters are to be installed in parallel with each ASD unit. Each ASD installation willinclude one 2400 kVAr 5th, one 1800 kVAr 7th and one 1200 kVAr lith hannonic filter. The design specifications for these filters as provided by General Electric Drive Systems Department , (GEDS) are included in Appendix-1. The present study investigates the performance of the proposed harmonic filters and the resulting degree of harmonic distortion expected under a variety of operating scenarios. Start-up and normal plant configurations are evaluated in addition to assessing the effects of filter outages on the hannonic distortion of plant voltages and currents. t 1 i i a 4 , I AUG 26 '94 17:39 518 385 7067 PAGE.006 l l l

g ert+5 wr wrswwmemam e y s, . Section 2 SYSTEM MODELING AND DATA This report specifically studies the performance of the ASD units and harmonic filters - associated with Generating Unit 2. As shown in Figure 2.1, the associated portion of the electrical distribution system includes Generating Unit #2, Start-Up Transformers #2 and 

         #3, #2 Unit Auxiliary Transformer, #1 Auxiliary Bus and #2 Auxiliary Bus. - The figure .

shows the bus numbers, ASD locations and harmonic filter arrangements examined in this report. The performance of the ASDs and harmonic filters associated with Generating Unit #3 are not evaluated since they are normally fed via different supply transformers from a stiff utility tie point. The result of the strong tie point is to reduce the harmonic common coupling between the Unit-2 and Unit-3 distribution systems. Since PECO has indicated that the Unit-2 and Unit-3 systems are nearly identical, only one is examined for the purpose of this study. Several system configurations were examined based on the status of breakers A, B, C and D, noted in Figure 2.1. For each combination of breaker states, several plant load conditions were evaluated. Each scenario correlates the ASD load and harmonic current injection with the appropriate amount of 60 Hz motor load at each bus system model. As shown in Figure 2.1, the short, circuit stiffness at each 230 kV utility tie point is 10,265 MVA, The stiffness at the 500 kV tie point is 34,189 MVA. The #2 Unit Auxiliary Transformer (3-winding type) shown in Figure 2.1 was modeled using an equivalent-T representation. l l b l AUG 25 '94 17: 40 519 385 7067 PAGE.007 l l

23OKV SYSTEM s' 23OKV SYSTEM SC; 10.265 WVA .. 3 SC: 10.265 MVA 11,700MVA c- 20,9/500KV O l2 GEN UTIL2 3-1$ 390uvA 1280 MVA, 22 KV, 0.90Pr N UDL1 

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Filter Impedance / Rating With age, the impedance of capacitors may be expected to increase slightly, thereby , raising the tuning point of a harmonic filter. If the tuning point rises sufficiently, the filter may create parallel resonant conditions at the frequency for which it was originally tuned. To avoid this occurrence, itis desirable to tune the filter slightly below the target frequency, i.e., a 5th tuned to 4.9H, a 7th tuned to 6.85H or an 1Ith tuned to 10.9H. This arrangement gives good performance and avoids the possible amplification of harmonic currents due to the interaction between the filters. In accordance with the filter design specifications and normal manufacturing tolerances, the ASD harmonic filters are assumed to be tuned at the 4.89,6.85, and 10.92 harmonic orders, respectively. Table 2.1 documents the impedances of the filter capacitors and reactors used in this study. Per manufacturer's test data, the harmonic filter capacitors typically exhibit a kVAr output of 105% of their nameplate ratings. The capacitor impedances in Table 2.1 reflect these test results. Capacitor resistances are negligible. Filter reactor impedances are based upon the desired tuning point, in accordance with allowable manufacturing tolerances and available tap positions. The X/R ratios of the filter tuning reactors are - assumed to equal 40. It is assumed that harmonic filter reactor cores will not saturate under the full spectra of hannonic filter current, thereby resulting in constant reactor inductance. Table 2,1 Filter Impedance Data Used in Harmonic Study DESIRED Filter kVAr CAPACITOR REACTOR TUNING POINT Rating IMPEDANCE IMPEDANCE (14.41 kV) (PU) (PU) (N) - 2400 0.0000 -j6.20127 0.00648-j0.25935 4.89 1800 0.0000 -j8.26838 0.00440 -j0.17618 6.85 10.92 1200 0.0000 -jl2.40254 0.00260 -j0.10401 N9tt

1. PU unit on 10 MVA,13.8 KV
2. Impedance data is not actual measured filter impedance data i 3. Assumed reactor X/R ratio of 40
4. Capacitor impedance based on 105% kVAr nameplate rating l

7 AUG 26 '94 17: 41 518 385 7067 PAGE.009 

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U l Harmonic Current Inlection The magnitudes of the harmonic current components " injected" by the ASD units are related to the drive speed. As the drive speed and fundamental component ofload , I current increase, the magnitudes 'of the lower harmonic components also tend to increase. Some of the higher frequency components reach maximum values at intermediate load levels, but the majority of the harmonic current components are greatest at full load. Table 2.2 shows the harmonic currents injected into the 13.8 kV bus by each ASD unit for a variety of drive speeds. Since the separate ASD units are located at different points within the electrical distribution system and operate independently, the hannonic currents generated by the separate drives will not generally occur at the same phase angles. As the separate currents combine in the power system, they will add vectorily and some degree of cancellation may expected to occur. For the purposes of this study, it is assumed that the harmonic currents injected by the separate drives are actually in phase and add arithmetically. This assurnption leads to a conservative calculation of the total , hannonic distortion (THD) since cancellation due to unequal phase angels is ignored. Table 2.2 Harmonic CurrentInjection 3er Each ASD DRIVE % OPEED 

                                     -H       100.00   80.00     60.00     40.00     20.00 1      335.0    214.4     113.9      63.7      63.7 6       66.0     43.2      23.1       13.0     13.0-8.9                           ;

7 44.6 29.8 15.9 8.9 11 26.6 19.3 10.6 6.0 6.0 i l 13 20.4 15.1 8.3 4.6 4.7 8.9 4.0 4.0 l 17 14.4 11.9 19 10.7 9.5 5.5 3.1 3.1 3.0 3.0 l 23 7.6 8.2 6.1 25 5.3 6.4 4.0 2.3 2.3 l 2.4 j 29 3.4 5.8 4.o 2.4 1.8 1.8 I 31 2.1 4.5 3.1 l 35 0.9 4.2 3.3 2.0 2.0 37 0.4 3.1 2.5 1.4 1.4 _ 41 0.9 2.9 2.7 1.7 1.7 0.9 2.1 2.0 1.2 1.2 43 47 1.6 2.0 2.3 1.5 1.6 49 1.2 1.4 1.7 1.0 1.0 

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                                                                  !/ .W'.d/il$  F:WN."/S PT' l-THD % ] 26.5 l 28.7 l 29.8 l 30.2 l 30.2 s

l AUG 26 '94 17: 42 518 385 7067 PAGE.010 

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        *Ej Section 3 HARMONIC ANALYSIS AND RESULTS To evaluate the effects ofinjected harmonic currents on the Peach Bottom Nuclear Plant electrical distribution system, a computer based harmonic analysis was perfonned. The analysis method basically determines hannonic current flows and bus voltages using a system of nodal admittance equations. Ideal voltage or current sources at individual frequencies represent harmonic sources. Inductances, capacitances and transformers are assumed to be ideal elements within the frequency range ofinterest. Eddy current factors are employed in modeling the resistances of each type of device. The solution of multiple source systems uses the superposition principle disregarding phase angle relationships. Thus, the current or voltage distortion at any point is the algebraic sum of the distortion due to each source. This renders the calculation method conservative.

Actual measurements are expected to be less than the calculated values. However, this method is a valid means of assessing the boundaries of the harmonic perfonnance of an actual industrial power system. The following equations are useful in assessing the extent of harmonic current and voltage distortion. THDy = SQRT( SVh2) / V for i h = 2 to n V h= Voltage @ Harm. Order h l l Irss = SQRT( SI h2)/11 for h = 2 to n Ih = Current @ Harm. Order h 

                         = S Vh "S Ih* Zh      for h = 1 to n      Zh= Impedance. @ Harm. Order h Vsum The response of the electrical distribution system to the harmonic currents injected by the ASD equipment was evaluated under sixty four (64) different operating scenarios. As illustrated in Tables 3.1 through 3.4, analyses were perfonned under four switching configurations involving circuit breakers A, B, C and D (see Figure 2.1). Under each configuration, four combinations of hannonic filter states were evaluated. For each combination of circuit breaker and harmonic filter switching conditions, four ASD speeds (40,60,80 & 100 %) were evaluated. Tables 3.1 through 3.4 summarize the conditions and key results of each scenario. The output for each scenario is provided in Appendix-3.

9 AUG 26 '94 17: 42 518 385 7067 PAGE.011

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Table 3.1 l Total Harmonic Distortion Resulta j Adjustable Speed Drive at 100% Speed i Case sysseen BusJ Bus 4  :;- TMD THD THD THD THD THD. F9ters AUX-1 AUX 2 EMER E-LC Non 1E Voltage N Ceedgerstlen F9 ears '.[ AlskV 490V 400Y Criteria Breaks 45osed AUX-1 AUX-2 - 13.8 kV 13.8 kV i B&C Off Off muu 5.4 5.3 . . (5 >5.0 2 B&C On On 2.1 2.1 . . l.8 3 B&C Off On mmre 5.3 2.1 . . 4.3 > 5.0 4 B&C On Off 2.1 5.2 . . l .3 > 5.0 l I 6 A&D On On REE 2.3 2.3 2.3 2.1 2.0 < 7 A&D M On - 6.7 23 6.5 6.0 5.6 > 5.0 ? 8 A&D On M 23 6.2 - 2.3 2.1 5.1 > 5.0 f 10 AAC On on Emu 2.3 2.1 2.3 2.1 2.0 f f 11 A&C Otr On m 6.7 2.1 6.5 60 56 75.0 12 A&C On Off 2.3 5.2 2.3 2.1 4.2 >5.0 t r.', .Y L 14 B&D On On m 2.1 2.3 . . 1.9 _ 15 B&D Off On m 5.2 2.3 . . 4.4 73.0 16 B&D On Off gm 1.1 6.2 . . 5.1 >5.0  ; ? L l F Table 3.2 $ Total Harmonic Distortion Results Adjustable Speed Drive at 80% Speed Case Sysesan BusJ Bus 4 imu TED TED Tau THD THD. f .- EMER B-LC Non 1E Voltage _.~ AUX 1 

                      #     Ceedgareale    FBiers                            FBesee                                                                                AUX.2 L                                                                                                                                                                                                               400V Brunks-Cissed  AUX.1                            AUX.2 13.8 kV                              13.8 kV              4.16 kV      400V                Cities 4m J

4.7 . 4.0 B&C OII Off umui 4.5 . ( 1 2 5&C on On umm 2.3 23 . . 2.0 , f l 3 5&C Otr On m 47 2.3 . . 4.0 Off A6 . 3.s L ~4 B&C On 2.3 . i l 6 A&D On on m 2.f - 2.5 2.6 2.3 2.2 l 7 A&D Off On m 19 2.5 5.8 5.3 5.0 >5.C 5.5 2.6 2.3 4.5 > 5.J 8 A&D On Off 2.6 2.3 2.6 2.3 1.2 10 A&C On On EM 2.6 > 11 AAC Off On e __5.9 23 5.8 5.3 3.0 j'T 4.6 2.6 2.3 3.7 12 A&C On Off 2.6 l 0 l' W h r >. 14 B4D On On m 23 23 . . 1.1 15 bad Off On m 4.7 2.5 . . 4.0 46 >5.0 $' 36 bad On Off . m 2.3 53 . . i L 10 5 3 AUG 25 '94 17: 43 518 385 7067 PAGE.012  ; 6 

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Table 3.3 Total Harmonic Distortion Results Adjustable Speed Drive at 60% Speed _ __ _ J Systeun Bus 4 Bus-2 THD THD THD TND THD THD. 4 Case AUX-2 BMER E-14 Non-1E Voltate l 

                       #       Cr"._ " -     Peters     FBleve          A1lX 1 13.8 kV       A16kV         480V         480V        Criteria Broeks-Closed AUX-1      AUX-2           13J kV Off                                    3.1                         .             26 i          B&C                    Off m           3.1                          .

EM 1.6 . . 1.4 2 BAC On On 1.7 Off m 1.6 . . 16 3 BAC On 3.1 Off 3.0 . . 2.5 4 BAC On 1.7 1.8 1.8 1.7 1.6 6 A&D On On 1.9 1.5 3.8 3.3 3.3 7 A&D Off On 3.9 M 1.9 3.6 1.5 1.7 2.9 8 A&D On 1.7 1.6 to A&C On On EER 1.9 1.6 1.8 3.8 3.5 3.3 Ii A&C Off On unsu 3.9 1.6 A&C On Off L9 3.0 1.8 13 2.4 12 14 BAD On On m 1.6 1.8 - . 1.5 __ BW . 2.6 13 B&D Off On 3.1 1.8 . 3.6 . 2.9 16 B&D On Off sami 1.6 . Table 3.4 Total Harmonic Distortion Results Adjustable Speed Drive at 40% Speed Bas 4 THD Trw THD TMD THD THD. Case Bystem Bus 4 , . AUX 4 E3RR I.LC Non.15 Voltage N Consguration Futsee Futers / AUK.1 - 13.8 kV 23J W 4.16W 480V 480V Cr66stes Rheks Closed AUX.1 AUX-2 Off mm 1.9 . . i.6 i B&C Off 1.8 

                                                                  = mas                    1.0             .           .            0.8 2         B&C           On        On               1.0 1.0             .           .            1.3 3         B&C           Off       On    -          1.8                                                                         _
                                                                                                                       .            1.6 4         B&O           da        Off              1.0           L.9             .

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2. 2.2 m 1.1 1.1 1.0 0.9 6 A&D On On 1.1 1.9 ,

EM 1.1 2.2 2.0 7 A&D Of On 2.3 1.9 Off 2.3 1.1 1.0 4 A&D On 4.1 

                     '                                                                                                        t .M-        W#2.'dM 0.9 10        A&C          On        On     M          1.1           1.0           1.1         1.0 1.9 1.0          2.2          2.0                                                 ,

In A&C Off On 3.3 ,. 1.1 1.0 1.3 12 AAC On Off ,,1 1.9 

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                                                                                                             .           .           0.9 14        B&D           On        On     NIE       1.0           4.1 1.1              .           .            1.J                                 ,

B&D Off On 1.8 _ 15 2.3 . 1.9 16 B&D On Off 1.0 . i-11 AUG 26 '94 17: 44 518 385 7067 PAGE.013

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Tables 3.1 through 3.4 compare the expected total harmonic distortion of bus voltage (THDv) with the acceptable levels recommended in IEEE Stnd. 519 - 1993. The standard has been developed to establish guidelines concerning the distortion of system voltage and current waveforms due to the behavior of non-linear load devices. . The standard primarily concerns itself with conditions at the point of common coupling (PCC) between an industrial customer and the local utility system. Within an industrial plant, the PCC is considered to be the point between the non-linear load and other loads. For the purposes of this study, the PCC is considered to be the 13.8 kV Auxiliary bus supplying a given ASD. The standard recommends that the THDv at a general purpose bus be maintained at or below 5% while 10% THDy may be allowed at a bus serving solid state drive equipment. These limits are not analytica'ly derived, but are based upon many years' experience l within the electricalindustry. Table 3.1 summarizes the results of the harmonic analysis assuming the ASDs are operating at 100% speed. As seen in the table, the THDy at a given 13.8 kV Auxiliary Bus is expected to exceed 5% under this drive load when the local harmonic filters are turned off. The THDy is expected to exceed 6% when the 13.8 kV bus is supplied via its start up transformer and to only slightly exceed 5% when the larger, generator auxiliary - transformer is employed. Table 3.2 stunmarizes the results of the harmonic analysis assuming the ASDs are operating at 80% speed. As seen in the table, the THDv at a given 13.8 kV Auxiliary Bus is not expected to exceed 5% when supplied via the generator auxiliary transformer 

           . regardless of the state of the localharmonic filter. If a given 13.5 kV bus is supplied         .

the associated start-up transformer, the local harmonic filter will be required to hold the THDv below 5%. However, without the local filter, the THDv is expected to only [ slightly exceed 5%. i Tables 3.3 and 3.4 illustrate that the THDv is not expected to exceed 5% at any bus under 

;             any switching condition if the ASD speeds are at or below 60%.

Case 5 in Table 3.2 indicates that THDv may approach 6% under start-up configuration with both filter sets turned off and the ASD speeds at 80%. Case 5 in Table 3.3 indicates a THDy approaching 4% under similar conditions with the drive speeds at 60%. By interpolation, it may be assumed that the THDy may approach 5% at approxima ASD speed. 12 26 '94 M 45 518 385 7067 PAGE.014

i ,,'e.'..  ; The harmonic analysis results, contained in Appendix 3, indicate the current and voltage duties impressed upon the harmonic filter reactors and capacitors. When compared with the filter design ratings, contained in Appendix 1, it is clear that the harmonic filter capabilities will not be exceeded under any operating scenario evaluated. Although solid state drives often constitute the major source of harmonic currents in an industrial system, other non-linear loads are also present. Some common examples are fluorescent lighting, personal computers and battery chargers. Although the effects'of such devices do not equal those created by high power drives and rectifiers, they may be  : of significant magnitudes when considering a low voltage distribution circuit. Such is the l case at the Peach Bottom Nuclear Plant. Per recent measurements performed by PECO, the ambient bus voltage distortion present at 480V Load Center #1 falls between 1 and 2% Although negligible in itself, this , ambient voltage distortion will add to the distortion levels predicted in the aforementioned hannonic analysis. The voltage components at each frequency will add vectorily, thus the total voltage at any one frequency will be less than the arithmetic addition of the individual components. Since the various phase angle relationships of these voltage components are unknown, a conservative approach should be taken in estimating the possible total harmonic distortion at a given bus. Table 3.5 conservatively estimates the THDy at 480V Load Center #1. The voltage - i components predicted by the harmonic analysis with circuit breakers A and D closed and both harmonic filters turned off are edded arithmetically to the ambient voltage i components noted in the PECO measurements. The resulting THDv at the load center _ bus is indicated at the bottom of the table for ASD speeds of 40,60,80 and 100% By , interpolation, it .may be assumed that the THDy at Load Center #1 may approach 5% at approximately 65% ASD speed. Thus, the inclusion of ambient harmonic distortion results in a 5% reduction in ASD speed if the THDv at the 480V Load Center #1 is to _be  ; maintained at or below 5%. , Finally, it must be remembered that the preceding analysis is conservative. Variability - introduced by system damping effects and harmonic source phase angle relationships should result in lower harmonic distortion levels than those predicted herein. Although the IEEE recommendations concerning bus voltage distortion are only meant to apply at the point of common coupling between a static load and power supply system, PECO intends to apply the 5% guideline throughout the Peach Bottom Nuclear Plant distribution system. Before final plant operating guidelines based on hannonic distortion limits are 13 l AUG 26 '94 17: 45 518 385 7067 PAGE.015 

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established, a thorough measurements program should be undertaken to verify the actual L distortion levels experienced within the plant under various operating conditions. Table 3.5 / Projected Percent Harmonic Distortion at 480V Load Center #1 I Including the Effects of Ambient Volta ge Distortion ASD Speed (%) ;g/f{ d'ib 100 80 60 40 H Amblent H Ambient in - s-n .' 100 100 100 100 f.9 2 1.1 1 100 0 0 0 d 6.'.- 4 0.4 3 0.7 0 . l 1.8 0.9 0.5 ile 6 0.2 5 0.8 2.7 i 1.7 0.9 0.5 t.19 8 0.2 7 0.6 2.5 i 0 0 0 up 10 0.2 9 0.2 0 1.7 0.9 0.5 y.)y. 12 0.2 11 0.2 2.4 13 0.1 2.2 1.6 0.9 0.5 m 14 0.1 i 0 0 s% 16 0.1 15 0.2 0 0 0.6 s';t' 18 0.1 17 0.1 2 1.6 1 0.8 0.5 WK 20 0.1 l 18 0 1.6 1.5 0 0 0 VP. 22 0.1 'i 21 0.1 0 0.6 .?.m. 24 0.2 23 0.2 1.4 1.5 1 i i I 25 0 1.1 1.3 0.8 0.5 M 28 0.1 

                                                                                                                                      ~

0 0 0 Mili 28 0.1 27 0.1 0 0.9 0.6 P.@ 30 0.1 29 - 0.1 0.8 1.4 - 0.8 0.5 r(sh 32 0.1 31 0.1 0.5 1.1 0 0 i% 34 0.1 33 0.2 0 0 0.9 0.6 & 38 0.6 35 0.6 0.2 1.2 0.8 0.4 *it.n 38 0.2 37 0.1. 0.1 0.9 . 0 0 -{. 9 40 0.1 39 0.1 0 0 . 0.9 0.8  ;>.ht-. 42 0 41 0 0.3 1 0,7 0.4 .s>3 44 0.1 43 0.1 0.3 0.7 0 0 q.6. 46 0.1 45 0.1 0 0 0.8 0.9 0.8 72 48 0.1 0.7 47 0.1 0.1 0.8 0.7 0.4 . k l, . 50 49 0 0.6 THDv 9100% As0 speed = 7.10 THDv 9 80% ASD Speed = 8.46 THDv 9 60% As0 speed - 4.68 THDv 9 40% ASD Speed = 3.46 14 AUG 26 '94 17: 46 518 385 7067 PAGE.016 

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Section 4 CONCLUSIONS The following conclusions may be drawn from the foregoing analysis:

1. The harmonic filters as specified by GEDS are adequate to meet the system requirements per IEEE-std. 519-1993 and performance requirements per PECO.
2. For the system conditions investigated, the operation of the ASD equipment, -

including harmonic filters, will create less than 3% additional harmonic distortion of system voltage (THDv).

3. To maintain THDy below 5% at the 13.8 kV bus with a set of harmonic filters out of service, the associated ASD should not be operated above 70% speed.
4. To maintain THDy at lower voltage buses below 5% under similar conditions while including the effects of ambient distortion may require the reduction of the ASD speed to 65%.
5. Before final plant operating guidelines based on hannonic distortion limits are established, a thorough measurements program should be undertaken to verify the

' actual distortion levels experienced within the plant under various operating l Conditions. a , d 15 AUG 26 '94 17: 47 518 385 7067 PAGE.017

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l Section 5 RECOMMENDATIONS The following recommendations are made based on the results reported herein:

1. For each filter installation the optimal tuning points should be as follows:

range <5 n = tuning point 5th filter n = 4.89 n = 6.85 range <7 i.e. 60 Hz

  • n 7th filter range < 11 lith filter n = 10.92 Note that exact tuning of the filters is not possible due to the discrete nature of the filter reactor taps, but should be tuned as nearly as possible to the tuning points show above.
2. At the time ofinstalletion,13.8 kV bus voltage and filter current measurements should be performed to ensure that distortion levels are within PECO voltage distortion criteria and that the filters are operating within their design limits.
3. The filters should be checked periodically (i.e. annually) to ensure their proper condition and fitness to serve.
4. The installation of future drives or capacitor banks may effect the duties impress upon the harmonic filters. Filter duties should be investigated following a .

plant modification.

5. To maintain THDy levels at or below 5%, a given ASD should not be operated 70% speed while the associated harmonic filters are offline. The effects of harmonic distortion may lower this limit to 65%
6. Before final plant operating' guidelines based on harmonic distottion limits are established, a thorough measurements program should be undertaken to vesify actual distortion levels experienced within the plant under various operating conditions.

16 AUG 26 'S4 17: 47 518 385 7067 PAGE.'018 i 

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