Important Considerations for Specifying MV Mining Switchgear Western Mining Electrical Association Edmonton, Canada June 13, 2008

Transcription

1 Important Considerations for Specifying MV Mining Switchgear Western Mining Electrical Association Edmonton, Canada June 13, 2008

2 (Above 1000V and up to 38kV for Surface Mining) Key Components of Specification: Scope Applicable Standards Service Conditions Ratings Construction Tests Quality Assurance System

3 Scope Scope of work Define what is required Example: This specification defines requirements of one (1) 69kV-25kV, 60Hz, 15 MVA mine-duty skid mounted portable substation with primary structure, transformer, neutral grounding resistor and secondary switchgear, close coupled to transformer.

4 Applicable Standards (For illustration only) IEE Std C Metal-Enclosed Interrupter Switchgear IEEE Std C AC HV Circuit breakers IEEE Std C37.22 MV Switches used in indoor Metal-Enclosed Switchgear NFPA 70E-2000, Electrical Safety Requirements for Employee Workplace IEEE Std , IEEE Guide for performing Arc-Flash Hazard Calculations NEC, National Electric Code

5 Types of Switchgear Assemblies Defined by IEEE Standards SWITCHGEAR ASSEMBLIES METAL-ENCLOSED POWER SWITCHGEAR METAL-ENCLOSED BUS C37.23 CONTROL SWITCHBOARDS C37.21 LOW-VOLTAGE POWER CIRCUIT BREAKER (LV) C METAL-CLAD (MC) C METAL-ENCLOSED INTERRUPTER (MEI) C GUIDE FOR TESTING MV ME SWITCHGEAR FOR INTERNAL ARCING FAULTS C NON-SEGREGATED PHASE SEGREGATED PHASE ISOLATED PHASE REQUIREMENTS AND GUIDE FOR CALCULATING LOSSES VERTICAL (OPEN OR ENCLOSED) DUAL DUPLEX CONTROL DESK BENCHBOARD DUPLEX BENCHBOARD FIXED RACK CABINET SWING RACK CABINET

6 Service Conditions Usual Service Conditions The equipment shall be designed for the following service conditions: 1. The temperature of the cooling air surrounding the enclosure of the switchgear is within the limits of -30 C and +40 C 2. The altitude of the installation does not exceed 1000 m (3300 ft) 3. The effect of solar radiation is not significant

7 Unusual Service Conditions Or you may list: 1. The equipment shall be suitable to operate within the limits of -30 C and +50 C (require either derating or select next higher ampacity rating) 2. The altitude of the installation does not exceed 1500 m (5000 ft), (require either de-rating or use higher insulation level 3. The effect of solar radiation shall be considered per IEEE Std C37.24

8 Load current-carrying capabilities at various ambients 552A 1104A

9 Altitude Correction Factors Switchgear that depends on air for an insulating and cooling medium will have a higher temperature rise and a lower dielectric withstand capability when operated at higher altitudes The following Table shows historical altitude correction factors for dielectric withstand voltage and continuous current Specifier may refer to Annex B of IEEE PC for additional guidance

10 Altitude Correction Factors

11 Effect of Solar Radiation is Normally Insignificant Monthly Normal Max Temp in US & Canada See IEEE Std C for Ref Station June July August Phoenix 39.7 C/103.5 F 41.1 C/106 F 39.8 C/103.6 F Las Vegas 37.9C/100.2F 41.1C/106F 39.6C/103.3F Sheridan 24.9C/76.8F 30.1C/86.2F 29.6C/85.3F Evansville 30.1C/86.2F 31.7C/89F 30.7C/87.3F Fairbanks 21.2C/70.2F 22.4C/72.3F 19.1C/66.4F Edmonton 20.9C/69.6F 22.5C/72.5F 21.8C/71.2F Temperature rise of about 15 C may be expected on the conducting parts due to solar radiation

12 Ratings Ratings of Switchgear Designations of Operating Limits under Specified Conditions 1. Rated maximum voltage 2. Rated power frequency 3. Rated insulation levels 4. Rated continuous current 5. Rated momentary withstand current 6. Rated short-time withstand current

13 Example 25kV Dual VCB House w/o NGR Ratings of Switchgear 1. Rated maximum voltage = 27kV rms 2. Rated power frequency = 60Hz 3. Rated insulation levels: Power frequency withstand voltage = 60kV rms; BIL = 125kV peak 4. Rated continuous current = 1200A 5. Rated momentary withstand current = 43kA peak(10 Cy) 6. Rated short-time withstand current = 16kA (2 s) Bkrs have SC interrupting rating, switches do not Switches do have fault close rating

14 Example Neutral Grounding Resistor Ratings of NGR kV L-L, 13.8kV L-N, 60 Hz C = Ohm 3. Current = 25A 4. Duty/Max Temperature rise = Extended/610 C 5. Finish = Mill galvanized 6. Enclosure type = Outdoor 7. IEEE Std , reaffirmed 1990

15 Neutral Ground Monitoring if applicable Specify 1. Neutral ground monitoring device 2. Sensing resistor 3. Current transformer

16 Rating of Simple 25kV Junction box

17 25kV Junction box Ratings of Switchgear 1. Rated maximum voltage = 27kV rms 2. Rated power frequency = 60Hz 3. Rated insulation levels: Power frequency withstand voltage = 60kV rms; BIL = 125kV peak 4. Rated continuous current = 600A 5. Rated momentary withstand current =??ka peak(10 Cy) 6. Rated short-time withstand current =??A (2 s)

18 Associated Major Components Ratings of major components should also be listed in specification 1. Vacuum circuit breakers 2. Disconnect switches (specify load-break or non load-break) 3. Instrument transformers (CT s, PT s & CPT s) 4. Lighting arresters (MCOV for grounded or ungrounded system) 5. Ground monitor 6. Metering, controls, relays and ground monitors 7. Power transformers and primary structures for portable substations

19 Construction Considerations for Rugged Mine Duty Switchgear Skid (shall be fabricated using the following structural members) Wide flange I-beams for cross members Heavy duty structural steel channels for runners Wide runners with 3/8 steel plates on bottom ¼ Thick steel deck and belly plates ¾ -1 Thick steel wear plates under runners 1 ½ X 10 X 30 steel towing eyes with 3 eye Towing eyes at 45 degree angle to facilitate lifting with slings 1 Diameter steel J-hooks for tying off the cables

20 Skid for Portable Substation (Partial view)

21 Skid for Portable Substation

22 Skid for Portable Substation

23 Construction Considerations for Rugged Mine Duty Switchgear Enclosure (shall be fabricated with) 11 Gauge steel with seam welded construction Stainless steel hinges and door hardware Galvanized steel slide-bolt latches with provisions for padlocking Double flange door construction with drip shield Nema 3-R construction with door stops and gaskets Viewing windows for disconnect switches Adequate cable termination height 3/8 Steel plates for blast protection of transformers

24 Construction Considerations for Mine Duty Switchgear Enclosure Finishes After the enclosure fabrication all welds and hard to reach areas shall be cleaned with steel wire brush and power grinder to remove any corrosion, weld splatter and scale All enclosures shall be cleaned with high pressure phosphatizing solution to clean and etch the surfaces Enclosure shall be painted with a minimum of mil high-solids primer and mil acrylic enamel top coat Electronic paint gauge may be used to assure uniform quality finish Exterior paint shall withstand 2000 hours of exposure to a 5% salt spray

25 Steel Fabrication Welds are cleaned with a steel wire brush Power grinder is used to remove any corrosion, scale and weld splatter

26 Steel Fabrication High pressure cleaning with phosphatizing solution, rinsing and air drying of sub-assemblies and assemblies

27 Construction Two-Coat Paint System Primer: Alkyd high-solids universal primer Finish Coat: Acrylic enamel, high-solids semi-gloss finish 2000 Hrs of salt spray withstand, resistant to chalking, peeling, and UVR

28 38kV Switch and Fuse Enclosure for Portable Sub

29 Blast Protection of transformers 11 Ga Seam welded construction 3/8 Steel Plates Optional top lifting structure for crane handling

30 Wiring Control and secondary wiring Wiring shall be rated for 600V, and 90 C, and shall be flame-retardant. Wire shall be type SIS as listed in the NEC. Wiring across a hinge shall be flexible to withstand repeated door movement without sustaining damage to wire strands or insulation Wire size shall be suitable for the maximum steady-state load Wire shall be No. 14 AWG and larger

31 Insulation Coordination When Cables are ran through neutral CT CT s are properly spaced and air gaps are sealed with RTV to eliminate corona

32 Production Tests Production tests made for quality control shall be performed to assure that product meets the design specifications and applicable standards 1. Power frequency (60Hz) dielectric tests 2. Mechanical operation tests (Functioning of operating mechanisms, interlocks, door locks etc) 3. Grounding of instrument transformer cases (Metal case design only) 4. Control wiring continuity check (Operational check) 5. Polarity verification (To ensure correct connections between instrument transformers and meters) 6. Request test data for power transformer if applicable

33 Final Inspection & Production Tests

34 Quality Assurance Vendor shall be certified to ISO-9001 Quality Management System Vendor shall provide MSHA certified field service technicians when required

35

36 MSHA Certified technicians

37 Questions?

38 Thank you