TRANSMISSION FACILITIES...7

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2 Table of Contents 1. INTRODUCTION Objective NERC FAC-008 Compliance Seminole s Normal Rating Seminole s Four-Hour Rating Seminole s Emergency Rating Implementation TRANSMISSION FACILITIES Normal Rating Emergency Rating POWER TRANSFORMER Power Transformer Generator Step-Up Power Transformer Transmission CIRCUIT BREAKER Normal Rating Emergency Rating INSTRUMENT TRANSFORMER Instrument Transformer Potential Instrument Transfer Current Instrument Transfer Current Bushing Instrument Transformer Current, Free-Standing AIR DISCONNECT SWITCH Normal Rating Emergency Rating CIRCUIT SWITCHER Normal Rating Emergency Rating LINE TRAP Normal Rating Emergency Rating Page 2 of 37

3 9. SHUNT COMPENSATION DEVICE STATION BUS Station Bus Strain Station Bus Rigid SERIES COMPENSATION DEVICE Normal Rating Emergency Rating GENERATOR FACILITIES Seminole Generating Station (SGS) Generator Generator Bushing Current Transformers (CT) Iso-Phase Bus GENERATOR FACILITIES Midulla Generating Station (MGS) Generator Generator Bushing Current Transformers (CT) Metal Clad Vacuum Circuit Breakers Iso-Phase Bus Non-Segregated Metal Enclosed Bus Duct Shielded Triple Tandem Extruded Cables General MGS Assumptions METERING DEVICE AND RELAY PROTECTIVEDEVICE TERMINAL EQUIPMENT APPENDIX A - SEMINOLE RATING TABLES APPENDIX B TERMINAL EQUIPMENT Terminal Equipment Elements and Dedicated Facility Element Configurations Page 3 of 37

4 1. INTRODUCTION 1.1. Objective This document describes Seminole s methodology used to determine the Normal Rating and Emergency Rating of Seminole transmission and generation Facilities. Seminole s Normal Rating and Emergency Rating for each of Seminole s Facilities will not exceed the most limiting rating for each Element or individual piece of equipment that makes up that Facility 1.2. NERC FAC-008 Compliance It is the intent of this document to demonstrate Seminole s compliance with NERC Reliability Standard FAC-008 to ensure that the Facility Ratings used in the reliable planning and operation of the BES are based on established methodologies Seminole further demonstrates compliance by documenting and making readily available Seminole s Normal Ratings and Emergency Ratings Equipment is specified, designed, and applied for the full ranges of voltage, current, frequency, fault current, transient conditions, and ambient conditions to which it is expected to be subject. This consideration of operating limitations is applicable to all equipment on the BES Seminole s Facility Ratings are published in its BES Facility Ratings documentation, these ratings are subject to change as required for technical, operational, and business applications that may require re-rating Facilities The following specifically demonstrates compliance to NERC FAC-008 requirements: Seminole shall make its Facility Ratings Methodology available for inspection and technical review by those Reliability Coordinators, Transmission Operators, Transmission Planners, and Planning Authorities that have responsibility for the area in which the associated Facilities are located, within 15 business days of receipt of a request If a Reliability Coordinator, Transmission Operator, Transmission Planner, or Planning Authority provides written comments on its technical review of Seminole s Facility Ratings Methodology, Seminole shall provide a written response to that commenting entity within 45 calendar days of receipt of those comments. The response Page 4 of 37

5 shall indicate whether a change will be made to the Facility Ratings Methodology and, if no change will be made to that Facility Ratings Methodology, the reason for the no change Seminole s Normal Rating This section describes Seminole s Normal Rating methodologies for all transmission Elements. Seminole s Normal Rating methodologies for all generation Elements are described separately in Sections 12 and 13 of this document Summer Rating the summer rating is based on manufacturer s nameplate, manufacturer s recommendations, the design of the Element, or industry standards, and takes into consideration the ambient conditions Winter Rating Seminole s winter rating for all generation and transmission equipment is the Loadability Factor (LF) that takes advantage of lower ambient temperatures. The winter rating is derived from multiplying the summer rating by the LF of that Element Seminole s Four-Hour Rating Seminole s four-hour summer rating equals the summer Normal Rating and the four-hour winter rating equals the winter Normal Rating Seminole s Emergency Rating This section describes Seminole s Emergency Rating methodologies for all transmission Elements. Seminole s Emergency Rating methodologies for all generation Elements are described separately in Sections 12 and 13 of this document. Seminole s Emergency Ratings for transmission Elements are based on pre-event loading of the equipment, ambient conditions, and, unless stated otherwise, a 7-minute post-event duration that the equipment will be allowed to run at the Facility s Emergency Rating. The Emergency Rating is determined by multiplying a Multiplying Factor (MF) to the Element s summer Normal Rating. Seminole utilizes two philosophies for pre-event loading: Station Equipment (Power Transformers, Shunt Compensation Devices, Series Compensation Devices, and Generators), Relay Protective Devices and Terminal Equipment 100% pre-event loading Transmission Lines the Emergency Rating for Seminole transmission lines will be determined from the actual pre-event loading of the transmission line to determine the allowable post-event loading. Page 5 of 37

6 1.6. Implementation Prior to December 30, 2011, Seminole s Emergency Ratings were equivalent to the Normal Ratings. Effective December 30, 2011, Seminole incorporated new Normal Ratings and Emergency Ratings system-wide. As these ratings are revised, they will be added to Seminole s BES Facility Ratings documentation. Page 6 of 37

7 2. TRANSMISSION FACILITIES Seminole overhead transmission lines are designed and operated so that the conductor maintains a safe clearance from objects, including: vegetation, buildings, vehicles and people. These clearances are determined by the NESC and followed by Seminole through the use of the individual line design characteristics. While manufacturer conductor temperatures and minimal loss of life recommendations are considered, Seminole has accepted additional loss of life in the conductor with transmission line designs at higher maximum temperatures not exceeding temperatures herein Normal Rating Seminole s Normal Rating is based on the individual transmission line s design parameters. These design parameters with consideration of the thermal limitation and maximum conductor sag specific to each line are used to maintain minimum NESC clearances Design Considerations Each of Seminole s transmission line s have individual thermal limitations. Following is a list of typical conductors in use by Seminole and the maximum operating temperatures not to be exceeded: AAC - 85 C ACSR C ACSS C In addition, the following line parameters are Seminole s standard in rating all Seminole conductor: Parameter Value Wind Speed, perpendicular to the conductor 3.0 ft / s Latitude/Azimuth 30 /0 Altitude 40 ft Time/Day 12:00 PM/Jun 10 Environmental Conditions Clear Ambient Temperature Summer - 35 C Winter - 0 C Operated Temperature ( C )/Coefficient of Emissivity Operated Temperature ( C )/Coefficient of Solar Absorption <=75 C >75 C <=75 C >75 C Table 1. Transmission line summer and winter Normal Rating parameters Page 7 of 37

8 Design Tools Seminole utilizes Southwires SWRate version 3.0 to perform the Calculations required. SWRate s calculations are based on IEEE Standard 738[1] Emergency Rating Seminole s Emergency Rating is based on the pre-event loading of the transmission line. For clearance purposes, Seminole s transmission lines will not be allowed to exceed the designed thermal limitation of that transmission line Design Considerations Seminole utilizes the same design and ambient parameters in determining the Emergency Rating as are used in calculating the Normal Rating of the transmission line. Additionally the following pre-event loading parameters are utilized: Pre-Event Loading The transmission line s allowable MF will depend on the preevent loading of the transmission line. The resulting allowable current will be limited to the maximum operating temperature of the transmission line Design Tools Seminole utilizes Southwires SWRate version 3.0 to perform the Calculations required. SWRate s calculations are based on IEEE Standard 738[1]. Page 8 of 37

9 3. POWER TRANSFORMER 3.1. Power Transformer Generator Step-Up Seminole s Generator Step Up (GSU) transformer capacities are based on the manufacturers nameplate rating of the unit. Seminole s GSUs Normal Rating and Emergency Rating are equal Normal Rating - Seminole s Normal Rating for all GSUs are the manufacturer s nameplate rating Summer Seminole uses the manufacturer s nameplate rating Winter Seminole s winter rating is the same as the summer rating of the unit Emergency Rating Seminole s Emergency Rating equals the Normal Rating Power Transformer Transmission Seminole does not own or operate any BES transmission power transformers; however, the following is Seminole s rating methodology for transmission power transformers. Seminole s transmission power transformer capacities are based on the manufacturers nameplate rating of the unit Normal Rating Summer Seminole summer rating is the manufacturer s nameplate rating of the unit Winter Seminole s winter rating is the same as the summer rating of the unit Emergency Rating Seminole s Emergency Rating Methodology for transmission power transformers is based on IEEE standard C IEEE has withdrawn this standard; however, Seminole has decided to retain the standard for Seminole s Emergency Rating based on the following understandings and believes these values to be conservative based on the parameters chosen: Transmission power transformers will not typically experience 100% of loading levels pre-event. Seminole has chosen MF values from IEEE C57.92 based on 100% pre-event loading of the transformer Seminole s Emergency Rating transmission power transformers will not be post-event loaded beyond the 7-minute emergency duration. Page 9 of 37

10 Seminole has chosen MF values from IEEE C57.92 based on 30- minute post-event loading resulting in a calculated maximum loss of life of 0.25% Rating Considerations: The following assumptions are not to be exceeded. IEEE C57.92 does not specifically indicate loading beyond the nameplate for the 7 minute duration assumptions provided below. Therefore, Seminole has adopted the 30 minute loading with a 0.25% loss of life as the Emergency Rating. To simplify transformer Rating Methodology, Seminole has adopted the 65 C rise above ambient for 55 C and 65 C rise transformers. This rating is more conservative than the 55 C rise and will be used for all transmission power transformers regardless of the transformer s rise. 65 C rise 40 C summer, 0 C winter 0.25% loss of life within a 24 hour period 100% load prior to peak load Multiplier Factors 1 : Transformer Summer Winter Design OA/FA 1.56pu 2.00pu OA/FOA/FOA 1.45pu 1.77pu Table 2. Transmission line summer and winter Normal Rating parameters 1 IEEE C , Table 3. Page 10 of 37

11 4. CIRCUIT BREAKER 4.1. Normal Rating Summer - Seminole s Normal Rating is based on the Manufacturer s nameplate for that unit Winter - Seminole s winter rating LF is based on IEEE C To simplify circuit breaker ratings, Seminole will use an LF for the more conservative SF 6 type of circuit breakers for SF 6 and oil type circuit breakers of 1.3pu. LF = I r θ MAX θ a θr 1/1.8 Parameter θ a, ambient temperature 0 C I a, allowable LF at θ A I r, rated continuous current Values (1 - from Table 1, IEEE C ) SF pu Oil pu θ MAX, allowable maximum SF C temperature at rated current 2 Oil - 90 C θ r, limit of observed temperature rise SF 6-65 C at rated current 2 Oil - 50 C Table 3. Circuit breaker winter LF parameters 1.00pu of summer Normal Rating 4.2. Emergency Rating Seminole s Emergency Rating is based on the following assumptions parameters listed in Table 4 and equations listed below. To simplify circuit breaker ratings, Seminole will use an MF for the more conservative SF 6 type of circuit breakers for SF 6 and oil type circuit breakers of 1.6pu. 1.8 I θ i = + I r i ( θ MAX 40) θ a 2 From Table 1 Limits of temperature and temperature rise for various parts and materials of circuit breakers, IEEE C Page 11 of 37

12 θmax θ s i θs = + θi 1 1 ts / τ e θ s MF = θmax Parameter I i, initial current carried, pre-event I r, rated current I s, emergency current carried, postevent θ MAX, maximum allowable temperature at rated load θ MAXs, allowable maximum temperature under emergency load (additional 15 C) θ s, total temperature due to I S θ a, ambient temperature θ i, total temperature due to I i /I r =1 at 35 C τ, thermal time constant (IEEE C , Table 4) Values 1.00pu of summer Normal Rating 1.00pu of summer Normal Rating SF pu Oil pu SF C Oil - 90 C SF C Oil C TBD 35 C, summer ambient also used for winter SF C Oil - 85 C 0.5, for all circuit breakers Table 4. Circuit breaker summer and winter MF parameters Page 12 of 37

13 5. INSTRUMENT TRANSFORMER 5.1. Instrument Transformer Potential Rating of potential devices is beyond the scope of this methodology. These devices do not have a Normal Rating or an Emergency Rating due to their designed application. Potential transformers (PT, VT, CCVT) are specified for the kv range of its transmission, substation, or generation system Instrument Transfer Current For Seminole s owned or operated Current Transformers (CT, CVT), Seminole s Normal Rating and Emergency Rating are the same. The CT manufacturer develops and supplies the CTs with a rating factor (RF) and any overload factors to those units Rating Assumptions: Average ambient temperature, air cooled over a 24hr period, 30 C Maximum ambient temperature of 40 C Seminole has accepted the slight loss of life for the occasion when average temperatures exceed 30 C or maximum ambient temperatures exceed 40 C Instrument Transfer Current Bushing Rating CTs Per IEEE Standard C57.13, Temperature rise of current transformers that are a part of high-voltage power circuit breakers or power transformers shall be in accord with IEEE Standard C37.04 or IEEE Standard C , respectively. For bushing CTs operating at other than maximum turns ratio, the thermal RF must be used in conjunction with the operating turns ratio in determining the rating of the CT Normal Rating Summer Seminole s summer rating for bushing CTs are the manufacturer s nameplate times the transformer s RF at the bushing CTs operating turns ratio A 3000A bushing CT, with an RF of 1.5, operated at 1500:5 will have a Normal Rating of 1500A X 1.5 = 2250A Winter Seminole s winter rating for bushing CTs takes advantage of lower ambient temperatures as shown in Figure 1-55 C rise current Page 13 of 37

14 transformer basic loading characteristics (in air), IEEE C Table 5 lists the standard RFs and the resulting LF at 0 C ambient temperature. RF LF (at 0 C) pu pu Table 5. Bushing CT LF pu pu pu pu Emergency Rating - Seminole s Emergency Rating for bushing CTs is equal to the Normal Rating Instrument Transformer Current, Free-Standing The CT manufacturer develops and supplies a RF and any overload factors for each CT Normal Rating Summer Seminole s summer rating for free-standing and slip-over CTs is the manufacturer s nameplate times the transformers RF Winter - Seminole s winter rating for free-standing and slip-over CTs takes advantage of lower ambient temperatures as shown in Figure 1-55 C rise current transformer basic loading characteristics (in air), IEEE C Table 6 lists the standard RFs and the resulting LF at 0 C ambient temperature. RF LF (at 0 C) pu pu pu pu pu pu Table 6. Free-Standing CT LF Page 14 of 37

15 Emergency Rating - Seminole s Emergency Rating for bushing CTs is equal to the Normal Rating. Page 15 of 37

16 6. AIR DISCONNECT SWITCH 6.1. Normal Rating Summer Seminole s summer rating is the manufacturer s nameplate of that unit Winter Seminole s winter rating is based on Figure 1 Non-enclosed indoor and outdoor switches LF vs. ambient temperature, IEEE C To simplify air disconnect switch ratings, Seminole has adopted the most conservative class designation of F06, ӨMAX = 105 C, ӨR = 53 C, to derive the LF at 0 C ambient temperature for all types of material (IR=1.0pu). LF = I R θ MAX θ A θ R LF 1.40pu Table 7. Air disconnect switches winter Normal Rating LF 6.2. Emergency Rating Seminole s Emergency Rating is based on the IEEE C37.37 formula below. From IEEE, during short term loading conditions (less than 24hours) the switch is allowed an additional 20 C, ӨE, on ӨMAX (I=1.0pu). MF θ + θ θ e dit MAX E r = dit θ R (1 e ) θ A Page 16 of 37

17 Parameter Value Ө MAX, allowable max temperature 105 C Ө R, limit of observable temperature rise 53 C Ө E, additional temperature allowed for less than 24hr 20 C d, duration of emergency 7 min T, time constant for switches 30 min Ө A, ambient temperature MF 35 C - summer 0 C - winter 1.30pu - summer 1.50pu - winter Table 8. Air disconnect switches summer and winter Emergency Rating parameters and Loadability Factor Page 17 of 37

18 7. CIRCUIT SWITCHER Seminole s Normal Rating and Emergency Rating are based on IEEE C Normal Rating Summer Seminole s summer rating is based on the Manufacturer s nameplate for that unit Winter Seminole s winter rating is based on the equation below from IEEE C to take advantage of lower ambient temperatures. To simplify circuit switcher ratings, Seminole will use an LF for the more conservative SF6 type of circuit switcher for all types of circuit switchers of 1.3pu. LF = I r θ MAX θ θ r a 1 / 1.8 Parameter Values (1 - from Table 1, IEEE C ) θ a, ambient temperature 0 C LF SF pu Oil pu I r, rated continuous current 1.00pu of summer Normal Rating θ MAX, allowable maximum temperature at rated current SF C Oil - 90 C θ r, limit of observed temperature rise at rated current SF 6-65 C Oil - 50 C Table 9. Circuit switcher winter LF and rating parameters 7.2. Emergency Rating Seminole s Emergency Rating is based on the following assumptions, parameters listed in Table VII.2 and equations listed below To simplify circuit switcher Emergency Rating, Seminole has chosen to use the more conservative values of SF 6 Ө MAX and θ MAXs and a summer and winter base of 35 C ambient for all circuit switchers (SF 6 and Oil). To simplify circuit switcher Page 18 of 37

19 ratings, Seminole will use an MF for the more conservative SF 6 type of circuit switcher for all types of circuit switchers of 1.6pu. 1.8 I θ i = MAX + I r i ( θ 40) θ a θmax θ s i θs = + θi 1 1 ts / τ e Parameter I i, initial current carried, pre-event I r, rated current MF θ 40 s MF = 40 θmax θ MAX, maximum allowable temperature at rated load θ MAXs, allowable maximum temperature under emergency load (additional 15 C) θ s, total temperature due to I S θ a, ambient temperature Values 1.00pu of summer Normal Rating 1.00pu of summer Normal Rating 1.60pu SF C SF C TBD θ i, total temperature due to I i /I r =1 at 35 C SF C τ, thermal time constant (IEEE C , Table 4) Table 10. Circuit switcher MF and rating parameters 35 C, summer ambient also used for winter 0.5, for all circuit switchers Page 19 of 37

20 8. LINE TRAP Seminole s Normal Rating and Emergency Rating, summer and winter, for line, or wave, traps are based on ANSI C Normal Rating Summer Seminole s summer rating is based on the Manufacturer s nameplate for that unit Winter - To simplify line trap ratings, Seminole has adopted the most conservative insulation temperature index from Table 6, ANSI C and line trap material resulting in a LF of 1.12pu. Seminole utilized IEEE C , for dry-type aid-core series-connected reactors to calculate the winter load factor. LF Tk = T k θ Parameter T k, absolute temperature for conductor Values (1 - from Table 1, IEEE C ) C - copper C - aluminum Ө, ambient temperature 0 C LF 1.17pu - copper 1.12pu - aluminum Ө MAX, hottest spot temperature rise 85 C (above 40 C) Table 11. Line trap LF and rating parameters 8.2. Emergency Rating Seminole s Emergency Rating is defined in ANSI C Seminole has chosen as an Emergency Rating of 1.40pu to match the 40 C, and the 1.50pu to match 0 C, 15 minute overload (Seminole will not exceed 7 minutes) current allowed by Table 1A, Annex A, IEEE C C ambient 0 C ambient 1.40pu 1.50pu Table 12. Line trap MF Page 20 of 37

21 9. SHUNT COMPENSATION DEVICE Seminole s summer and winter Normal Rating and Emergency Rating for shunt compensation devices, shunt capacitors, and shunt reactors are equal and are provided by the manufacturer. Page 21 of 37

22 10. STATION BUS Station Bus Strain Normal Rating Seminole s Normal Rating, summer and winter, for strain bus utilize the same operating conditions as transmission lines (See Section 2) Emergency Rating - Seminole s Emergency Rating is defined below: Seminole s Emergency Rating, summer and winter, for strain bus utilize the same operating conditions as transmission lines (See Section 2) Seminole s Emergency Rating, summer and winter, for station jumpers utilize the same operating conditions as transmission lines (See Section 2) Station Bus Rigid The following is Seminole s rating methodology for rigid aluminum tubular bus, 53% and 40% conductivity. Aluminum tubular bus, 53% and 40% conductivity, is the primary rigid bus design throughout Seminole s system. Ratings for less common rigid bus material and design, such as Aluminum Integral Web Channel Bus (IWCB), are direct from IEEE , Annex B, or manufacturer s recommendations Normal Rating Summer and winter Seminole s Normal Rating, summer and winter, utilizes Std IEEE , Annex C, for tubular bus uses Seminole s bus calculator to derive the values with the following parameters. Parameter Values (1 - from Table 1, IEEE C ) T 1, ambient temperature 35 C - summer 0 C - winter T 2, bus temperature 90 C - Normal 100 C - Emergency v, wind velocity in feet per second 3fps C, conductivity 53% T6 40% T6 F, skin effect coefficient at cycles Page 22 of 37

23 LAT, north latitude in degrees 30 TIME, time of day for anticipated highest load levels Atmospheric conditions Z 1, azimuth of conductor line in degrees Table 13. Line trap MF 12:00 noon Clear N-S Emergency Rating Seminole s Emergency Rating allows the conductor temperature, T 2, to be heated to 100 C while utilizing the remaining Normal Rating parameters outlined in this section. Page 23 of 37

24 11. SERIES COMPENSATION DEVICE Seminole does not own or operate any BES series compensation devices; however, the following is Seminole s rating methodology for series reactors Normal Rating Seminole s Normal Rating, summer and winter, are based on and provided by the manufacturer s nameplate Emergency Rating Seminole s Emergency Rating, summer and winter, are provided by the manufacturer s nameplate. Page 24 of 37

25 12. GENERATOR FACILITIES Seminole Generating Station (SGS) Generator Assumptions: The Original Equipment Manufacturer (OEM) has designed, built and delivered this generator in accordance with all applicable design standards and as such has provided name plate data that supports the stated operating limitations Considerations: Ratings provided by the OEM (name plate data) Generator Capability Curves provided to Seminole by the OEM Ambient conditions (relative humidity, barometric pressure, temperature, etc.) Operating Limitations Limitations will be evaluated as required based on current operating conditions (such as out of service H2 coolers) Normal Rating The normal rating is based on the OEM provided nameplate data and capability curves Emergency Rating The emergency rating is equal to the normal rating Generator Bushing Current Transformers (CT) Assumptions: The generator bushing CTs are rated in terms of primary current, even though the short time mechanical and thermal limitations are those of the secondary winding only (IEEE standard C , section 6.6.3) The SGS generator bushing CTs are single ratio CTs and as such are at maximum turns ratio. A rating factor (RF) of 1.0 is used to determine the CT s rating The generator CTs have the following characteristics and if replaced, are so with CTs with identical characteristics: Ratio: 25000/5 Page 25 of 37

26 Considerations: Single Ratio CT Ratings provided by the OEM (name plate data) Ambient conditions (relative humidity, barometric pressure, temperature, etc.) Operating Limitations Limitations will be evaluated as required based on current operating conditions (such as ambient temperatures exceeding designed CT operating conditions) Normal Rating The normal rating is based on the OEM provided nameplate data Emergency Rating The emergency rating is equal to the normal rating Iso-Phase Bus Assumptions: The Iso Phase bus is equipped with forced and cooled ventilation and unaffected by ambient conditions Considerations: IEEE standard C37.23 (Standard for Metal Enclosed Bus) was referenced to verify that proper cooling was established by the supplier (OEM) Ratings provided by the OEM (name plate data) The OEM equipment manual provides the ratings for this equipment Ambient conditions (weather, temperature, etc.) Being forced cooled, the Iso-phase bus is unaffected by ambient conditions Operating Limitations (forced cooling air, closed cooling water flow) With no forced air flow or cooling coils operating, SECI will operate the unit generator as prescribed by the manufacture s emergency rating Normal Rating Seminole utilizes the manufacturer s technical manual for the Iso-Phase bus ratings. Page 26 of 37

27 Emergency Rating SECI will operate at the following limited ratings during the specified conditions: Total cooling fan failure (loss of fan and cooling coils) 60 Minutes at the Normal Rating, then reduce to 14,000 amps any time greater than 60 minutes into and during the emergency condition Operational fan, failed cooling coils 90 Minutes at the Normal Rating, then reduce to 14,000 amps any time greater than 90 minutes into and during the emergency condition. Page 27 of 37

28 13. GENERATOR FACILITIES Midulla Generating Station (MGS) Generator Assumptions: The Original Equipment Manufacturer (OEM) has designed, built and delivered this generator in accordance with all applicable design standards and as such has provided name plate data that supports the stated operating limitations Considerations: Ratings provided by the OEM (name plate data) Generator Capability Curves provided to Seminole by the OEM Ambient conditions (relative humidity, barometric pressure, temperature, etc.) Operating Limitations Limitations will be evaluated as required based on current operating conditions Normal Rating The normal rating is based on the OEM provided nameplate data and capability curves Emergency Rating The emergency rating is equal to the normal rating Generator Bushing Current Transformers (CT) Assumptions: The generator bushing CTs are rated in terms of primary current, even though the short time mechanical and thermal limitations are those of the secondary winding only (IEEE standard C , section 6.6.3) The MGS generator bushing CTs are single ratio CTs and as such are at maximum turns ratio. A rating factor (RF) of 1.0 is used to determine the CT s rating The generator CTs have the following characteristics and if replaced, are so with CTs with identical characteristics: Combined Cycle Unit Ratio: 10,000/5 Page 28 of 37

29 Considerations: Peaking Unit Ratio: 4000/ Single Ratio CT Ratings provided by the OEM (name plate data) Ambient conditions (relative humidity, barometric pressure, temperature, etc.) Operating Limitations Limitations will be evaluated as required based on current operating conditions (such as ambient temperatures exceeding designed CT operating conditions) Normal Rating The normal rating is based on the OEM provided nameplate data Emergency Rating The emergency rating is equal to the normal rating Metal Clad Vacuum Circuit Breakers MGS has five 13.8 kv metal clad with vacuum circuit breakers enclosed in each Peaker control house Assumptions: The Original Equipment Manufacturer (OEM) has designed, built and delivered these breakers in accordance with all applicable design standards and as such has provided name plate data that supports the stated operating limitations Considerations: Ratings provided by the OEM (name plate data/technical Manual) Each Peaker Generator breaker is housed in the confines of an airconditioned Control House Operating Limitations Limitations will be evaluated as required based on current operating conditions Normal Rating The normal rating is based on the OEM provided nameplate data Emergency Rating The emergency rating is equal to the normal rating. Page 29 of 37

30 13.4. Iso-Phase Bus MGS s three Combined Cycle units have associated Iso-phase buses Assumptions: The Original Equipment Manufacturer (OEM) has designed, built and delivered these buses in accordance with all applicable design standards and as such has provided name plate data that supports the stated operating limitations Considerations: IEEE standard C37.23 (Standard for Metal Enclosed Bus) Ratings provided by the OEM (nameplate data) Ambient conditions (weather, temperature, etc.) Operating Limitations Limitations will be evaluated as required based on current operating conditions Normal Rating The normal rating is based on the OEM provided nameplate data Emergency Rating The emergency rating is equal to the normal rating Non-Segregated Metal Enclosed Bus Duct Each Peaker Generator is connected to an output breaker through a 4000-amp Non-Segregated Metal Enclosed Bus Duct Assumptions: The Original Equipment Manufacturer (OEM) has designed, built and delivered these buses in accordance with all applicable design standards and as such has provided name plate data that supports the stated operating limitations Considerations: IEEE standard C37.23 (Standard for Metal Enclosed Bus) Ratings provided by the OEM (nameplate data/ Technical manual) Ambient conditions (weather, temperature, etc.) Page 30 of 37

31 Operating Limitations Limitations will be evaluated as required based on current operating conditions Normal Rating The normal rating is based on the OEM provided nameplate data Emergency Rating The emergency rating is equal to the normal rating Shielded Triple Tandem Extruded Cables Each of the Peaker's generator breakers is connected to the low side of its step up transformer through 6 per phase (18 total) 15 KV shielded triple tandem extruded cables with copper conductor and 5-mil bar copper tape shield per phase. These cables are rated for cable tray use with each tray holding up to 36 cables Assumptions: The Original Equipment Manufacturer (OEM) has designed, built and delivered these buses in accordance with all applicable design standards and as such has provided name plate data that supports the stated operating limitations Considerations: The methodology used to rate these cables is per IEEE Standard 835, Table for 5 to 15 kv Shielded Single Conductor Extruded Dielectric Power Cable - in Free Air - Triplexed - 40ºC Air Ambient - 90ºC - Copper Conductor - Concentric Strand was used which indicates 734 amps per conductor Each cable is calculated to carry a maximum of amps based on Peaker Generator Name Plate Data ( kv or 3,441 amps/phase) Although rated for 105 C, the IEEE Standard 835 does not contain a table for 105 C copper conductor, concentric strand; the more conservative rating 90ºC table is used Cable losses and required area to dissipate the heat generated under load are calculated and shown below to allow using the rating applicable in Free Air NEMA Standard WC-74 Table 2-3 lists the resistance for 750-kcmil 25 ºC at ohms/k ft. Page 31 of 37

32 Assuming cable operating temperature at 70 degrees C (78% of rated temperature), the resistance is ohms/k ft With 36 heat sources and load factor of 100%, the losses are watts/ft For every 5 feet of solid non-ventilated trench there is a ventilated section of 30 by 40 inches The ventilated sections are covered with grating capable of taking H20 traffic Total wattage for each 5 ft section is watts square inches of area will dissipate a watt The minimum required area for watts is 519 square inches The ventilated area is 1440 square inches, which is % of requirement Operating Limitations C continuous operating temperature (see section ) C emergency rating C short circuit rating Normal Rating The normal rating is based on the OEM provided cable ratings, IEEE Standard 835, and the considerations listed in Sections through above Emergency Rating The emergency rating is equal to the normal rating General MGS Assumptions Average ambient temperature, air cooled over a 24hr period, 30 C Historically maximum ambient temperature is 40 C Each Facility Rating shall equal the most limiting applicable Equipment Rating of the individual equipment that comprises that Facility Operating limitations: Page 32 of 37

33 If the contingency of the Hardee/Vandolah 230 kv double circuits occurs and the overload on the Hardee/Polk line is 140% or higher, the Special Protection System (SPS) will automatically trip the online MGS Peakers. If the Interconnection Reliability Operating Limit (IROL) and System Operating Limit (SOL) still exist, SECI will coordinate manually backing down the online generation at MGS and HPS until the loading on the line is 100% or less If the contingency of the Hardee/Vandolah 230 kv double circuits occurs and the overload on the Hardee/Polk line is between 100% and 140%, the SPS will not trip. SECI will coordinate manually backing down the online generation at MGS and HPS until the loading on the line is 100% or less If the contingency of the Hardee/Vandolah 230 kv double circuits occurs and the overload on the Hardee/Polk line is 140% or higher, the SPS will automatically trip the online MGS Peakers. SECI will monitor the loading on the Hardee/Polk line. SECI will initiate any increase in generation output at HPS and MGS to prevent the potential overload on the Hardee/Polk 230 kv line. Page 33 of 37

34 14. METERING DEVICE AND RELAY PROTECTIVEDEVICE The terms Metering Device and Relay Protective Device are not NERC defined terms. For the purpose of this document, Seminole has defined these terms as devices that accept secondary quantities from the outputs of instrument transformers, e.g., generation, substation, and transmission equipment that is directly connected to a source primary voltage. This equipment is part of NERC s defined Protection System that includes: instrument transformers and line traps. The Normal Rating and Emergency Rating for Relay Protective Devices are located in the following sections within this document: Instrument Transformers - Section 5 - INSTRUMENT TRANSFORMER Line Traps - Section 8 - LINE TRAP Page 34 of 37

35 15. TERMINAL EQUIPMENT Terminal Equipment is not a NERC-defined term. For the purpose of this document, Seminole has defined this term as generation, substation, and transmission equipment to include circuit breakers, disconnect switches, circuit switchers, and station bus. Terminal Equipment will be used to identify all equipment within a switchyard or substation that has common use by more than one Facility. See APPENDIX B TERMINAL EQUIPMENT for examples of common Seminole bus configurations. The Normal Ratings and Emergency Ratings for terminal equipment are located in the following sections within this document: Air Disconnect Switches: Section 6 AIR DISCONNECT SWITCH Station Bus: Section 10 STATION BUS Circuit Breakers: Section 4 CIRCUIT BREAKER Circuit Switchers: Section 7 CIRCUIT SWITCHER Page 35 of 37

36 16. APPENDIX A - SEMINOLE RATING TABLES The following table is a tabulation of equipment covered in within this document. All LF and MF values are all in reference to Seminole s summer Normal Rating. Summer Winter Equipment Normal Emergency Normal Emergency Transmission Lines Variable Variable Variable Power Transformer GSU Transmission Variable Variable Circuit Breakers Instrument Transformers X RF Multiplier LF LF For a 2000A CT with a RF = 1.5: Summer A Normal Summer A Emergency Winter A Normal Winter A Emergency Air Disconnect Switches Circuit Switchers Line Trap Shunt Compensation Devices NA NA NA Station Bus Strain 3 Rigid Variable Variable Variable Variable Variable Variable Series Compensation Devices NA NA NA Generators Variable Variable 3 Seminole s normal and winter Normal Rating and Emergency Rating for conductors are determined by the transmission line s design parameters or the conductor s maximum allowed thermal capabilities. 4 Applicable to CT units only. 5 These devices are specifically designed and rated by the manufacturer, Seminole does not assign a LF or MF to these units. Page 36 of 37

37 17. APPENDIX B TERMINAL EQUIPMENT Terminal Equipment Elements and Dedicated Facility Element Configurations A Facility s rating will be based on all Elements within and dedicated to the Facility (transmission line conductor, line jumpers, line CTs, wave traps) and the Terminal Equipment Elements (breakers, CTs, disconnect switches, rigid or strain bus and equipment jumpers) that are associated with that Facility. The Terminal Equipment Facility Rating shall be based on the Facility Ratings Methodology within this document and its rating will be limited, under single or creditable multiple contingency conditions, to the rating of the most limiting Element within the Terminal Equipment. Page 37 of 37