Capstone Turbine Corporation Nordhoff Street Chatsworth CA USA Phone: (818) Fax: (818) Web:

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1 Phone: (818) Fax: (818) Web: Technical Reference Capstone MicroTurbine Electrical Installation Rev F (October 2013) Page 1 of 31

2 Capstone Turbine Corporation Nordhoff Street Chatsworth CA USA Telephone: (818) Facsimile: (818) Website: Capstone Technical Support Telephone: (866) 4-CAPSTONE or (866) Rev F (October 2013) Page 2 of 31

3 Table of Contents 1. Introduction Reference Documents General Requirements Protective Earth (PE) / Chassis Ground Grounding the Microturbine Neutral Grounding Location Grounding Potential Overcurrent Protection & Disconnecting Devices Power Bay Connections MultiPac Power Connections Grid Connect Phase Sequence Transformer Applications and Impedance Allowable Connections Standalone Mode Output and Load Specification Phase Sequence Transformers for Highly Non-Linear Loads Transformer Sizing Recommendation Generic Diagrams of Isolation Transformer Installation Allowable Connections Dual Mode Installations Requiring 4-Pole Motorized Grid Breaker Allowable Connections C65 Hybrid UPS Surge Protection Device Allowable Connections Input Impedance Example 1: Model C30 - Considering 1 Microturbine Example 2: Model C65 - Considering 1 Microturbine Example 3: Considering 3 Microturbines Rev F (October 2013) Page 3 of 31

4 List of Figures Figure 1. Recommended Device Layout... 9 Figure 2. C30 User Connection Bay Figure 3. C65 User Connection Bay Figure 4. C65 HUPS User Connection Bay Figure 5. C200 User Connection Bay Figure 6. C1000 User Connection Bay Figure 7. Power Connections: MultiPac System Ground Rod At Each Unit Figure 8. Power Connections: MultiPac System Common Ground Rod Figure 9. Connection to 480V Wye Service - Direct Connection Figure 10. Connection to Non-480V Wye Service Autotransformer with Grounded Neutral Figure 11. Connection to Wye-Wye Service: Isolation Transformer Figure 12. Connection to Wye-Delta Service: Isolation Transformer Figure 13. Connection to Non-480V Wye Service Autotransformer with Floating Neutral Figure 14. Isolation Transformer Installation Example Figure 15. Isolation Transformer Installation Example Figure 16. Isolation Transformer Installation Example Figure 17. Paralleling Transformers Installation Figure 18. Stand Alone Connections: Three-Phase Loads Figure 19. Dual Mode Connections: Using an Isolation Transformer List of Tables Table 1. Referenced Documents... 6 Table 2. Overcurrent Protection Sizing... 8 Table 3. N L1 L2 L3 DC Terminal Block Specifications Table 4. Protective Earth (PE) / Chassis Ground Terminal Block Specifications Table 5. Grid Connect Allowable Configurations Matrix Table 6. HUPS Allowable Connections Rev F (October 2013) Page 4 of 31

5 1. Introduction This document presents electrical installation information for the Capstone MicroTurbine systems. Capstone Microturbines (with the exception of the C65 Hybrid UPS) provide two operational modes: Grid Connect Mode (GC) Stand Alone Mode (SA) GC mode provides alternating current (AC) electrical power in parallel with a utility grid or with another generation source. GC mode includes built-in utility-synchronization capability and protective relay functions. In this mode, the microturbine acts as a current source, controlling its current output to meet the commanded power output at the rated voltage. SA mode provides alternating current (AC) electrical power for standby, backup, or remote offgrid purposes. In this mode, the microturbine acts as a voltage source, regulating its voltage output to the configured voltage and frequency settings. A Dual Mode (DM) connection option (which requires a Dual Mode System Controller), is available and allows automatic transition between GC and SA modes. Multiple systems can be combined and controlled as a single larger generating source, commonly known as a MultiPac. Operation as a MultiPac is available for SA, GC, and Dual Mode operation. The C65 Hybrid UPS product is unique since there are two AC connections, one for grid and one for critical load. The grid connection operates in a mode very similar to GC mode, and the critical load connection operates in a mode very similar to SA mode. This product s unique electrical configuration is considered separately in Section 7. This document describes proper electrical interconnection for the Alternating Current (AC) output versions only. Refer to our Hybrid Electric Vehicle documentation for Direct Current (DC) model installation instructions. CAUTION: All of the allowable utility service connections for the various microturbine operating modes are presented in this document. Consult Capstone if your utility service connections do not agree with those presented in this document Rev F (October 2013) Page 5 of 31

6 2. Reference Documents Table 1 provides a list of Capstone documents referenced in this Technical Reference. Table 1. Referenced Documents Document Part No Description C65 Microturbine User s Manual C30 Microturbine User s Manual C30 Electrical Technical Reference C60/C65 Electrical Technical Reference MultiPac Technical Reference Protective Relay Functions Technical Reference C200 Technical Reference C1000 Technical Reference C200 CARB Product Specification C30 and C60 HEV Application Guide C200 with HRM Outline and Installation (O&I) Drawing 3. General Requirements It is the responsibility of the installer to supply all ancillary electrical equipment such as electrical cable, switchgear, transformers, and disconnects through which the microturbine delivers its output power. The equipment must be capable of safely handling the maximum potential loads, and must meet all applicable local and national regulations. This section outlines general requirements for all Capstone products. WARNING: It is essential that the installer consult all of the applicable codes and industry standards before connecting the interface wiring for the microturbine. Notice that a qualified electrician may be required to perform this work Protective Earth (PE) / Chassis Ground All Capstone Microturbine products must have protective earth (PE) grounding for the chassis. A separate ground lug is included in the user connection bay for this purpose. Commonly this PE is provided by a ground rod installation. Using a single PE connection for multiple microturbine chassis grounds is acceptable. This PE may or may not be the same ground used for the microturbine neutral; if it is not, the PE for the chassis ground and the ground for the neutral should be at equivalent potentials, with respect to earth. All electrical wiring, including protection and grounding, must conform to all local and national electrical codes and regulations. All drawings in the document will indicate the protective earth (PE)/ chassis ground by PE/G Rev F (October 2013) Page 6 of 31

7 3.2. Grounding the Microturbine Neutral All installations, for both GC and SA modes, must have the neutral wire properly grounded. This provides a ground reference for proper operation. Neglecting to properly ground the microturbine system (that is, no neutral-to-ground connection, or more than one neutral-toground connection) can cause damage to the microturbine system. All electrical wiring, including protection and grounding, must conform to all local and national electrical codes and regulations Grounding Location It is recommended to ground the neutral wire(s) in only a single location, unless local code requires more than one connection. For example, it is sometimes required by local code to ground the neutral before the conductor leaves one building and travels into another, in case the neutral is broken during earthmoving activities. In the case of multiple grounding points, these grounding points should be at equivalent earth potentials; otherwise circulating currents can occur and provide a poor reference for operation. For GC installations, the recommended location of the neutral-to-ground connection is at the utility service panel or the utility service transformer. A neutral-to-ground connection is often already present at the wye utility service transformer. For SA and DM installations, the recommended location of the neutral-to-ground connection is at the microturbine service panel. Use of four-pole breakers may necessitate multiple neutral-toground connections, and more information is provided on this subject in Section 6. If multiple neutral-to-ground connections are required, please contact Capstone Applications Engineering for approval Grounding Potential WARNING: A solid earth ground 1 of the microturbine neutral is MANDATORY for successful operation. A high-resistance ground should not be necessary, due to the very low fault current contribution of the microturbine(s) 2. However, a high-resistance ground may be possible, and will require a modification to the microturbine as well as additional external surge protection equipment (to be supplied by the installer). Please contact Capstone Applications Engineering for approval. WARNING: Any high-resistance grounding scheme MUST BE APPROVED BY CAPSTONE PRIOR TO COMMISSIONING. 1 Measurable at 5 ohms or less ground resistance per NEC, NFPA, and IEEE recommendation 2 Approximately 2X nominal current Rev F (October 2013) Page 7 of 31

8 3.3. Overcurrent Protection & Disconnecting Devices Overcurrent protection is required for each microturbine, usually by circuit breaker or fused disconnect. This overcurrent protection device must be installed between the microturbine and the electrical service panel. The type and fault-current ratings of the device must meet maximum current and voltage ratings for each microturbine model as well as meet all local codes and specifications. Recommended sizing for overcurrent protection devices is as follows: Table 2. Overcurrent Protection Sizing Microturbine Model Recommended Trip Setting 3 C30 60 A rms C65 (UL, HUPS, and all other) C65 (CE) C200 C600 C800 C A rms 150 A rms 400 A rms 1200 A rms 1600 A rms 2000 A rms If a fused disconnect switch is used instead of circuit breaker, time delay fuses are not required. Fast acting, current limiting fuses are recommended. It is recommended to install the fuses on the microturbine side of the switch. CAUTION: A lockable disconnect device should be located within sight of the microturbine. Any disconnect device should always have lockout provisions to facilitate safe maintenance operations. In the case that the service panel and microturbine are very near, it may be acceptable to use the overcurrent protection device as this lockable disconnect; please note that most circuit breakers will require additional hardware to become lockable. In the case of a long distance between the microturbine and the service panel, this should be a separate lockable switch. Figure 1 shows the recommended configuration for a four unit multipack of microturbines. 3 Recommended trip setting based on 125% of maximum microturbine steady state current as listed in the C65 Electrical Technical Reference (410001). For example, the nominal steady state current of a C200 is 310 A rms. 125% x 310 Arms = A rms. This is rounded up to 400A rms Rev F (October 2013) Page 8 of 31

9 To Primary Service Panel or Utility Service Transformer Service Panel Main Circuit Breaker Circuit Breaker Lockable Disconnect To MT2 To MT3 To MT4 MT Note: Locate the lockable disconnect within viewing distance of the microturbine Figure 1. Recommended Device Layout Always refer to the latest national and local codes relative to your location to determine the proper connection requirements Power Bay Connections The User Connections Bay for each microturbine model is shown below. NOTE: In accordance with UL 2200, the conductor gauge and torque specifications for both N L1 L2 L3 DC and grounding terminal blocks are listed in Table 3 and Table 4 respectively. This is applicable for copper and aluminum conductor types. NOTE: Final selection of conductor sizing must respect all local and national codes. The wire gauge information in Table 3 and Table 4 is only a listing of physical capabilities of the terminal blocks, and should not be substituted for a proper engineering analysis for conductor gauge Rev F (October 2013) Page 9 of 31

10 Table 3. N L1 L2 L3 DC Terminal Block Specifications Microturbine Connection C30/C65/ C65 HUPS AC C200 / C65 HUPS DC C600/C800/ C1000 Wire Size Torque Spec 4 Max # of (AWG / MCM) (mm 2 ) (Lb-in) (N-m) Conductors Min Max Min Max per phase 6 2/ MCM 600 MCM Table 4. Protective Earth (PE) / Chassis Ground Terminal Block Specifications Wire Size Torque Spec 4 Microturbine (AWG) (mm 2 ) Connection (Lb-in) (N-m) Min Max Min Max C30 / C C / C600 / C800 / C1000 Installer must land ground wire on ground bus bar using appropriate hardware 4 Torque value listed is based upon maximum wire size using UL486 recommendation. Smaller torque values may be possible for small gauge wire. Refer to UL486 for recommended torques using wire gauges smaller than the maximum torque Rev F (October 2013) Page 10 of 31

11 Figure 2. C30 User Connection Bay Figure 3. C65 User Connection Bay Rev F (October 2013) Page 11 of 31

12 DC Battery (+) Terminal DC Battery (-) Terminal PE/G Auxiliary DC Gas Pack Connection with Fusing Figure 4. C65 HUPS User Connection Bay Rev F (October 2013) Page 12 of 31

13 Figure 5. C200 User Connection Bay Rev F (October 2013) Page 13 of 31

14 Phase A Bus Bar Phase B Bus Bar Phase C Bus Bar Neutral Bus Bar Ground Bus Bar Figure 6. C1000 User Connection Bay Rev F (October 2013) Page 14 of 31

15 3.5. MultiPac Power Connections Refer to the MultiPac Technical Reference (410032) for details on MultiPac operation. Power connections between the MultiPac systems will be necessary, and these connections must consider the proper phase wiring, neutral wiring, and grounding connections between the various systems. Refer to Figure 8 for electrical connection diagram for permitted MultiPac connections. Protective earth (PE) / chassis grounding can either be a ground rod at each unit (as shown in Figure 7), or can be a single, common ground rod at the service panel (as shown in Figure 8). For simplification of the following connection diagrams in this document, this multipac is represented electrically by a set of terminals L3, L2, L1, and N labeled Single or Multipac Connections. Figure 7. Power Connections: MultiPac System Ground Rod At Each Unit Rev F (October 2013) Page 15 of 31

16 Viewable Lockable Disconnect Microturbine or Multipac Service Panel Single Unit or Multipac Connections MT Circuit Breaker Main Circuit Breaker Microturbine #1 L3 L2 L1 N G L3 L2 L1 N Microturbine #N L3 L2 L1 N G MT Circuit Breaker PE/G NOTE: All wiring shown should be connected regardless of connection type. Figure 8. Power Connections: MultiPac System Common Ground Rod 4. Grid Connect Table 5 presents the various allowable connections for the Grid Connect operating mode. The table will show important attributes for comparison including standards compliance, wiring, etc. No 3-wire delta utility service connections are allowed 5. For details on each configuration, refer to the figure number shown for that configuration. 5 No three-wire delta utility service connections are allowed because the phase-to-ground voltages float, and over time, these voltages (with respect to ground) become unbalanced and cause microturbine nuisance trips. In addition, the phase-to-ground voltages can reach levels that can break the insulation in the IGBTs-to-ground and cause equipment failure Rev F (October 2013) Page 16 of 31

17 Table 5. Grid Connect Allowable Configurations Matrix Figure No. Standards Compliance Utility Service UL1741 CE/Other Wye Delta Transformer Type 9 X X X None 10 X X X Autotransformer with Grounded Neutral 11 X X X Wye/Wye Isolation 12 X X X Wye/Delta Isolation 13 X X Autotransformer with Floating Neutral 4.1. Phase Sequence The output phase sequence is L1 to L2 to L3. Notice that improper phase sequence connections may cause the microturbine to trip. It is the installer s responsibility to verify the proper phase connections between the microturbine and the grid Transformer Applications and Impedance A voltage transformer for the microturbine will be required if the circuit voltage is outside the 400 to 480 Volts AC range. All GC mode installations with transformers between the microturbine and the grid 6 must consider maximum grid impedance. Proper sizing of transformers in the installation is required to limit the impedance seen by the microturbine. For impedance limits required for installation of each microturbine model, refer to the Electrical Specification documents referenced in Table 1. Refer to Input Impedance on page 30 for example calculation of the impedance of the line run and transformers to the utility source Allowable Connections Figure 9 through Figure 13 present the permitted utility (or transformer) connections for Capstone products. 6 To a point in the distribution grid where the voltage is 6 kv or higher Rev F (October 2013) Page 17 of 31

18 Single Unit or Multipac Connections L3 Utility Service L2 L1 N PE/G Figure 9. Connection to 480V Wye Service - Direct Connection Figure 10. Connection to Non-480V Wye Service Autotransformer with Grounded Neutral Rev F (October 2013) Page 18 of 31

19 Figure 11. Connection to Wye-Wye Service: Isolation Transformer Figure 12. Connection to Wye-Delta Service: Isolation Transformer Rev F (October 2013) Page 19 of 31

20 Figure 13. Connection to Non-480V Wye Service Autotransformer with Floating Neutral 5. Standalone Mode 5.1. Output and Load Specification The microturbine output consists of three phases and a neutral. The current in each phase need not be balanced, as long as the electrical current limits per phase are respected. Loads may be connected phase-phase or phase-neutral. The nominal Stand Alone voltage setting is available between any two phases.. For current and voltage specifications of each microturbine model, refer to the Electrical Specification documents referenced in Table Phase Sequence For SA installations, the output phase rotation sequence is L1 to L2 to L3. Notice that improper phase connections can damage the connected loads or cause microturbine trips. Capstone cannot be held responsible for equipment damage caused by improper connections. It is the installer s responsibility to verify the proper phase connections between the microturbine and the load(s) Transformers for Highly Non-Linear Loads For any SA installation with highly non-linear loads, an isolation transformer is required. This transformer functions as a harmonic filter and provides additional benefits for motor starting and kva margin. Highly non-linear loads are defined as: Any loads causing the site current THD to be greater than 8% Rev F (October 2013) Page 20 of 31

21 Capstone Turbine Corporation Nordhoff Street Chatsworth CA USA Non-linear lighting loads: Fluorescent ballasts and sodium lamps There are two major benefits that are worth consideration. First, the energy storage in the transformer windings will reduce voltage drop during DOL (across-the-line) motor starts. Second, for 400V applications, using an operating voltage of 480V on the microturbine side of the transformer will provide up to 20% higher kva margin available for starting large electric loads. For sites requiring an isolation transformer, the recommended configuration is as follows: - Delta connection on microturbine side. - Wye connection is recommended on load side. However, delta connection on load side is also acceptable if required by installation volts output setting on microturbine side (may not be commercially available in your country, so 400V is acceptable, but this limits any motor starting benefits). - Impedance between 4-8%. Lower impedance will provide overall better voltage regulation, but may require a soft start ramp to be configured on the microturbines for installations with 3 or more microturbines. Autotransformers are not allowed as an alternative to the required isolation transformer, since they do not provide the galvanic isolation and delta winding which minimize the transmission of harmonics Transformer Sizing Recommendation For any SA installation requiring a transformer, the following sizing recommendations are provided. Per the discussion in Section 5.3, the recommended configuration is one or two large transformers after the paralleling of the microturbines, so these recommended sizes can be summed based on the total number of units connected to the same paralleling bus. o 45 kva per C30 system o kva per C65 system o 300 kva per C200 system o 900 kva per C600 system o 1200 kva per C800 system o 1500 kva per C1000 system 5.5. Generic Diagrams of Isolation Transformer Installation Figure 14 through Figure 16 represent examples of allowed configurations for SA and DM installations. Capstone recommends any transformers should be placed after the paralleling of the Multipac. Figure 17 represents a connection that is not recommended, but may be possible. If individual transformers are used before the paralleling of the microturbines, these transformers must be matched with identical impedance, kva rating, wiring sequence, and phase difference (primary to secondary) Rev F (October 2013) Page 21 of 31

22 Figure 14. Isolation Transformer Installation Example Figure 15. Isolation Transformer Installation Example Rev F (October 2013) Page 22 of 31

23 Figure 16. Isolation Transformer Installation Example Figure 17. Paralleling Transformers Installation Rev F (October 2013) Page 23 of 31

24 5.6. Allowable Connections Figure 18. Stand Alone Connections: Three-Phase Loads 6. Dual Mode An installation designed to switch between GC and SA operation is identified as a Dual Mode installation, and must meet the installation requirements for both GC and SA operation, including the required isolation transformer for SA operation. Automatic transfer between modes may be accomplished with the optional Capstone Dual Mode System Controller. Refer to the Dual Mode System Controller Technical Reference (410071) for details. Whether manual or automatic, the electrical conversion from one mode to the other must be planned with care, particularly the neutral and ground connections. Safety requirements, code requirements, and functional requirements must all be met Installations Requiring 4-Pole Motorized Grid Breaker In some parts of the world, 4-pole circuit breakers are required, which will break the neutral wire as well as the three phases. Given the requirement of grounding the neutral wire in both SA mode and GC mode (discussed in Section 3.2), there may need to be a neutral-grounding relay capable of keeping the neutral grounded when the DMSC switches the motorized breaker open. This construction and theory of operation is discussed in the Dual Mode System Controller Technical Reference (410071). The below allowable connections assume 3-pole breakers, but are otherwise valid for 4-pole breaker installations, assuming the proper neutral-grounding considerations Allowable Connections Figure 19 presents indirect connection using the Dual Mode System Controller. The DMSC is installed between the isolation transformer and the protected loads, and the utility or local transformer Rev F (October 2013) Page 24 of 31

25 Single Unit or MultiPac Connections Isolation Transformer Dual Mode System Controller Wye Utility Service or Local Transformer L3 L2 L1 N G Refer to Figures 10 & 11 for isolation transformer connection details Must be continuous with the utility ground Protected Loads PE/G Figure 19. Dual Mode Connections: Using an Isolation Transformer 7. C65 Hybrid UPS The C65 Hybrid UPS microturbine comes with two AC power connections, the GLCM and LLCM. The GLCM connection should connect to the utility grid source, and the LLCM output should connect to the critical load bus. Due to the unique design of the C65 Hybrid UPS microturbine compared to other Capstone products, external isolation transformers are required on both connections to avoid momentary short circuit through the internal power electronics. The required LLCM and GLCM AC power connections must be three-phase, four wire ungrounded wye. WARNING: The neutral wire should NOT be grounded at the microturbine connection bay or at either isolation transformer. The only ground connection should be the chassis ground connection at each C65 Hybrid UPS microturbine. This is due to the fact that the positive DC bus is grounded internally. The chassis grounding is required per normal installation guidelines listed in Section CAUTION: The maximum length for the conductor between each microturbine AC connection and the isolation transformer is 10 meters. All conductor should be run using grounded conduit. Exceeding this length could result in excessive EMF generation, which could interfere with operation of sensitive electrical equipment. Contact Capstone Applications Engineering with any questions. The DC external battery should be connected with proper polarity of positive and negative verified. There should be no power grounding on the external battery string, since this is provided internally to the Hybrid UPS Microturbine. For the DC battery connection, a DC circuit Rev F (October 2013) Page 25 of 31

26 breaker disconnect must be included between the batteries and the unit. See the C65 Hybrid UPS Application Guide (Refer to Table 1) for more details on battery system specification. Three- or four-wire connections are allowable, as shown in Figure 20 and Figure 21. For fourwire connections, the critical loads need not be balanced as long as the current limits per phase are not exceeded. WARNING: Three-wire critical load connections are allowable as long as the neutral on the critical load side of the isolation transformer is grounded AND the critical loads are BALANCED. No unbalanced critical loads are allowed for 3-wire critical load connections Surge Protection Device Due to the unique internal architecture of the C65 Hybrid UPS system, a surge protection device must be installed on the grid-side connection of the isolation transformer for each unit. Capstone will provide the device required for UL installations as well as any other 4-wire 480Y/277V installations. All other wiring configurations will require an alternative surge protection device, which must be specified with the assistance of Capstone Applications Engineering. The spec sheet and installation documents from the manufacturer are listed in Appendix of the C65 Hybrid UPS Application Guide (480049). The required connections for the surge protection device are described in detail in Figure 20 through Figure 22 below. The device should be mounted with leads as short as possible, recommended not to exceed 1m in length Allowable Connections Table 6. HUPS Allowable Connections Figure No. Grid Connection Wiring 4-wire 3- wire Critical Load Connection 4-wire 3-wire UL2200/1741 Compliance Isolation Transformer Windings Surge Protection Device 16 X X Yes Wye/Wye Supplied by Capstone 17 X X Yes Wye/Wye Contact Applications Engineering 18 X X No Wye/Delta Contact Applications Engineering Rev F (October 2013) Page 26 of 31

27 Figure Wire HUPS Installation Rev F (October 2013) Page 27 of 31

28 Figure Wire HUPS Installation with Wye/Wye Transformers Rev F (October 2013) Page 28 of 31

29 Grid L3 L2 L1 N Optional Lockable Disconnect Isolation Transformer Circuit Breaker Utility Service Surge Protection Device Electrical Connection Bay Critical Load L3 L2 L1 N Optional Lockable Disconnect Isolation Transfer (Wye-Wye) Circuit Breaker Critical Load Service Panel DC Battery + - to External Battery System PE/G Figure Wire HUPS Installation with Wye/Delta Transformers Rev F (October 2013) Page 29 of 31

30 8. Input Impedance Refer to Table 1 for the Electrical Specification documents listing input impedance requirements of each microturbine model Examples of the total electrical input impedance calculations which detail the values considering the microturbine output looking towards the utility are provided in the following paragraphs. NOTE: Input impedance calculations are for Grid Connect operation only Example 1: Model C30 - Considering 1 Microturbine Total Impedance for all conductors: Z L = 0.5%, Z R = 1.0% 30 KVA MicroTurbine 480 V 208 V 240 V Utility 5 kv 45 kva 45 kva 60 kva Z L1 = 5.6% Z L2 = 6.4% Z L3 = 5% Z R1 = 1.7% Z R2 = 1.9% Z R3 = 1.6% Inductive: Z L (Total) = 5.6% (30/45) + 6.4% (30/45) + 5% (30/60) + 0.5% = 11% (Value exceeds acceptable limit of 10%) Resistive: Z R (Total) = 1.7% (30/45) + 1.9% (30/45) + 1.6% (30/60) + 1% = 4.22% (Value is within acceptable limit of 5%) 8.2. Example 2: Model C65 - Considering 1 Microturbine Total Impedance for all conductors: Z L = 0.5%, Z R = 1.0% 65 KVA MicroTurbine 480 V 208 V 240 V Utility 5 kv 75 kva 75 kva 100 kva Z L1 = 5.6% Z L2 = 6.4% Z L3 = 5% Z R1 = 1.7% Z R2 = 1.9% Z R3 = 1.6% Z L (Total) = 5.6% (65/75) + 6.4% (65/75) + 5% (65/100) + 0.5% = 14.2% (Value exceeds acceptable limit of 10%) Z R (Total) = 1.7% (65/75) + 1.9% (65/75) + 1.6% (65/100) + 1% = 5.16% (Value exceeds acceptable limits of 5%) Rev F (October 2013) Page 30 of 31

31 8.3. Example 3: Considering 3 Microturbines Total Impedance for all conductors: Z L = 0.5%, Z R = 1.0% 480 V MicroTurbine #1 30 kva 480 V 45 kva Z L1 =5.6%, Z R1 =1.7% MicroTurbine #2 30 kva 480 V 480 V 4160 V Utility 34.5 kv 45 kva Z L2 =5.6%, Z R2 =1.7% 500 kva 2000 kva Z L4 = 7.2% Z L5 = 5% Z R4 = 1.8% Z R5 = 1.3% MicroTurbine # kva 480 V kva Z L3 =4.3%, Z R3 =1.4% Note: In these calculations, the number 120 represents the sum of the Microturbine outputs ( ) Microturbine #1 (30 kva): Z L (MT1) = 5.6% (30/45) + 7.2% (125/500) + 5% (125/2000) + 0.5% = 6.3% (Value is within acceptable limits) Z R (MT1) = 1.7% (30/45) + 1.8% (125/500) + 1.3% (125/2000) + 1% = 2.7% (Value is within acceptable limits) Microturbine #2 (30 kva): Z L (MT2) = 5.6% (30/45) + 7.2% (125/500) + 5% (125/2000) + 0.5% = 6.3% (Value is within acceptable limits) Z R (MT2) = 1.7% (30/45) + 1.8% (125/500) + 1.3% (125/2000) + 1% = 2.7% (Value is within acceptable limits) Microturbine #3 (65 kva): Z L (MT3) = 4.3% (65/112.5) + 7.2% (125/500) + 5% (125/2000) + 0.5% = 5.1% (Value is within acceptable limits) Z R (MT3) = 1.4% (65/112.5) + 1.8% (125/500) + 1.3% (125/2000) + 1% = 2.3% (Value is within acceptable limits) Rev F (October 2013) Page 31 of 31