Important Considerations for Specifying MV Mining

Switchgear Western Mining Electrical

Association Edmonton, Canada

June 13, 2008

Specifying MV Mining Switchgear (Above 1000V and up to 38kV for Surface Mining)

Key Components of Specification:

Scope Applicable StandardsService ConditionsRatings ConstructionTestsQuality Assurance System

Specifying MV Mining Switchgear Scope

Scope of workDefine 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.

Applicable Standards (For illustration only)

• IEE Std C37.20.3-2001 Metal-Enclosed Interrupter Switchgear

• IEEE Std C37.06-2000 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 1584-2002, IEEE Guide for performing

Arc-Flash Hazard Calculations• NEC, National Electric Code

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)

C37.20.1

METAL-CLAD (MC) C37.20.2

METAL-ENCLOSED INTERRUPTER (MEI)

C37.20.3

NON-SEGREGATED PHASE

SEGREGATED PHASE

ISOLATED PHASE REQUIREMENTS AND

GUIDE FOR CALCULATING LOSSES

VERTICAL (OPEN OR ENCLOSED)

DUAL

DUPLEX

CONTROL DESKBENCHBOARD

DUPLEX BENCHBOARDFIXED RACK CABINET

SWING RACK CABINET

METAL-ENCLOSED POWER SWITCHGEAR

METAL-ENCLOSED POWER SWITCHGEAR

METAL-CLAD (MC) C37.20.2

METAL-ENCLOSED INTERRUPTER (MEI)

C37.20.3

NON-SEGREGATED PHASE

METAL-ENCLOSED BUS C37.23

METAL-ENCLOSED BUS C37.23

GUIDE FOR TESTING MVME SWITCHGEAR FOR

INTERNAL ARCING FAULTSC37.20.7-2001

Specifying MV Mining Switchgear Service Conditions

Usual Service ConditionsThe 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

Specifying MV Mining Switchgear 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 de- rating 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

Specifying MV Mining Switchgear Load current-carrying capabilities at various ambients

552A1104A

Specifying MV Mining Switchgear 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 PC37.100.1 for additional guidance

Specifying MV Mining Switchgear Altitude Correction Factors

Effect of Solar Radiation is Normally Insignificant Monthly Normal Max Temp in US & Canada

See IEEE Std C37.24-2003 for Ref

Station June July AugustPhoenix 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

Specifying MV Mining Switchgear Ratings

Ratings of SwitchgearDesignations of Operating Limits under Specified Conditions

1. Rated maximum voltage2. Rated power frequency3. Rated insulation levels4. Rated continuous current5. Rated momentary withstand current6. Rated short-time withstand current

Specifying MV Mining Switchgear Example – 25kV Dual VCB House w/o NGR

Ratings of Switchgear1. Rated maximum voltage = 27kV rms2. Rated power frequency = 60Hz3. Rated insulation levels: Power frequency withstand

voltage = 60kV rms; BIL = 125kV peak4. Rated continuous current = 1200A5. Rated momentary withstand current = 43kA

peak(10 Cy)6. Rated short-time withstand current = 16kA (2 s)

Bkrs have SC interrupting rating, switches do notSwitches do have fault close rating

Specifying MV Mining Switchgear Example – Neutral Grounding Resistor

Ratings of NGR1. 23.9kV L-L, 13.8kV L-N, 60 Hz2. Resistance @ 25 C = 552.0 Ohm3. Current = 25A4. Duty/Max Temperature rise = Extended/610 C 5. Finish = Mill galvanized6. Enclosure type = Outdoor7. IEEE Std 32-1972, reaffirmed 1990

Specifying MV Mining Switchgear Neutral Ground Monitoring if applicable

Specify1. Neutral ground monitoring device2. Sensing resistor3. Current transformer

Specifying MV Mining Switchgear Rating of Simple 25kV Junction box

Specifying MV Mining Switchgear 25kV Junction box

Ratings of Switchgear1. Rated maximum voltage = 27kV rms2. Rated power frequency = 60Hz3. Rated insulation levels: Power frequency withstand

voltage = 60kV rms; BIL = 125kV peak4. Rated continuous current = 600A5. Rated momentary withstand current = ??kA

peak(10 Cy)6. Rated short-time withstand current = ??A (2 s)

Specifying MV Mining Switchgear 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 monitor6. Metering, controls, relays and ground monitors7. Power transformers and primary structures for

portable substations

Specifying MV Mining Switchgear Construction Considerations for Rugged Mine Duty

SwitchgearSkid (shall be fabricated using the following structural members)

• Wide flange I-beams for cross members• Heavy duty structural steel channels for runners• 18”-26” 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

Specifying MV Mining Switchgear Skid for Portable Substation (Partial view)

Specifying MV Mining Switchgear Skid for Portable Substation

Specifying MV Mining Switchgear Skid for Portable Substation

Specifying MV Mining Switchgear 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

Specifying MV Mining Switchgear 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 1.5-2.0 mil high-solids primer and 2.0-3.0 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

Steel FabricationWelds are cleaned with a steel wire brush

Power grinder is used to remove any corrosion, scale and weld splatter

Steel Fabrication

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

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

Specifying MV Mining Switchgear 38kV Switch and Fuse Enclosure for Portable Sub

Specifying MV Mining Switchgear Blast Protection of transformers

3/8” Steel Plates11 Ga Seam welded construction

Optional top lifting structure for crane handling

Specifying MV Mining Switchgear 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

Insulation Coordination When Cables are ran through neutral CT

CT’s are properly spaced and air gaps are sealed with RTV to eliminate corona

Specifying MV Mining Switchgear 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 tests2. 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

Final Inspection & Production Tests

Specifying MV Mining Switchgear Quality Assurance

• Vendor shall be certified to ISO-9001 Quality Management System

• Vendor shall provide MSHA certified field service technicians when required

MSHA Certified technicians

Questions?

Thank you