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9/30/14 Electrical Installa-ons Over 600 Volts Training Presenta2on by: Interna2onal Associa2on of Electrical Inspectors Southwestern Sec2on 2 1 Instructors Primary Course Outline Presented by: •  Introduc2on Chris Hunter Director Field Applica2on Program General Cable •  Basic principles and proper terminology Chuck Mello •  Voltages (low, medium, and high) Field Evalua2on Program Manager – Underwriters Laboratories •  Codes and standards Chuck Leisher •  Equipment and cable installa2ons Regional Technical Specialist Square D/Schneider Electric •  Key requirements in the NESC and the NEC •  Conductor and equipment tes2ng and maintenance Program Credits: Chris Hunter, Mike Johnston, Chuck Mello, Chuck Leisher •  Personnel safety 3 4 1 9/30/14 Scope of Presenta2on •  Review the opera2ng fundamentals of medium and high voltage systems Medium Voltage Cables and Termina2ons Chris Hunter •  Review the installa2on requirements of equipment and conductors •  Review the NEC requirements that apply to medium and high voltage installa2ons •  Review requirements from other codes and standards such as the NESC •  Review essen2als of safety for electrical workers 5 Specific Topics Covered •  Basic design criteria, basic principles and concepts •  Review of terminology •  Power genera2on and distribu2on •  Conductor types, splices, and installa2ons •  Termina2ons of medium and high voltage conductors •  Review of equipment types and applica2ons •  Building construc2on requirements related to medium and high voltage distribu2on 7 6 Topics Not Covered •  The high voltage aspects for signs from NEC Ar2cle 600 •  High voltage parts within u2liza2on equipment such as X-­‐ray equipment •  High voltage parts in electronic equipment, industrial machinery or similar products •  Other non-­‐power distribu2on high voltage applica2ons 8 2 9/30/14 Basic Principles Basic Principles (cont.) •  Protec2on of equipment from physical damage (external causes) •  Protec2on (safety) of people –  General Public •  Limited access •  Warning signs •  Protec2on of equipment and conductors from electrical damage (internal and external causes) •  Equipment construc2on –  Qualified workers •  Adequate clearances •  Protec2on of people (general public and qualified workers) from the hazards associated with medium and high voltage electrical systems 9 9/30/14 •  Equipment construc2on •  Safe work prac2ces •  Awareness of hazards •  Working on or near live parts
9 10 9/30/14 10 Terminology Basics •  Using a common language of communica2on is important Terminology Review •  Slang terms mean different things to different people •  Medium and high voltage systems bring forth new terminology and new meanings to exis2ng terms •  Defining and understanding the medium and/or high voltage words and terms –  Power used discussed in kVA now it is in MVA •  1 MVA is 1000 kVA –  Voltage ra2ngs are kV (thousand of volts instead of volts –  Fault duty is now in MVA class with kA interrup2ng ra2ng –  There is a “short-­‐2me ra2ng” for equipment 11 9/30/14 12 12 3 9/30/14 Terminology Basics (cont.) Medium Voltage Terminology •  Maximum Voltage/Maximum Design Voltage -­‐ Highest maximum voltage for which the equipment is designed and is upper limit for opera2on. Examples: 15 kV class, Max Voltage 14.4 kV •  Conductors (wires) are referred to as cables. •  Cables have short-­‐circuit protec2on but can take an overload up to a insula2on temperature of 220°C. •  Nominal Voltage -­‐ Normal system opera2ng voltage for which equipment should be applied. Examples: 4.16/4.76 kV, 13.8/15.0 kV. U2lity voltage will typically vary a max. +/-­‐ 5% of nominal system voltage. •  Low voltage circuit breakers have overcurrent inherent within the breaker •  High voltage “circuit breakers” are dumb electrically operated switches with external “brains” (protec2ve relaying) •  BIL -­‐ Basic Impulse Level -­‐ crest voltage the equipment will withstand without flashover. Wave shape is 1.2 x 50 µs expressed in kV. Examples: 4.16/4.76 kV BIL is 60 kV, 13.8/15.0 kV BIL is 95 kV, 27 kV BIL is 125 kV, 38 kV BIL is 150 kV. Transformer BILs may be different •  Those relays get their signals from “PTs” and “CTs” •  Devices are referenced to standard numbering such as “52”, “50/51”, “67”, “86”, “81o/u”, “87”, “27/47” 13 9/30/14 13 14 9/30/14 14 Medium Voltage Terminology (cont.) •  Dielectric Withstand •  This is a standard produc2on test using AC voltage, 60 hertz. This tes2ng verifies the device, insula2ng materials and spacings can withstand the test voltage for one minute, both phase-­‐to-­‐ phase and phase-­‐to-­‐ground with devices in the open and closed posi2ons, without flashover or puncture of insula2on materials. Impulse Test Wave Shape
•  Examples typical for switchgear: 50us
15 4.16/4.76 kV 60 kV BIL, test voltage is 19 kV 13.8/15.0 kV 95 kV BIL, test voltage is 36 kV 27 kV 125 kV BIL, test voltage is 60 kV 34.5/38 kV 150 kV BIL, test voltage is 80 kV 16 4 9/30/14 Medium Voltage Terminology (cont.) •  Interrup2ng Ra2ngs – Medium Voltage Terminology (cont.) •  Momentary Current Ra2ng -­‐ maximum current a closed device can withstand for 10 cycles –  Non-­‐load Break – Switches suitable to open voltage only (minimal load such as charging current acceptable) –  Load Break – Switches suitable to interrupt only load’s current. Load Interrupter Switches are not fault interrup-on rated. Load break ra2ngs are 600 or 1200A. (Load break interrupter switches cannot be used with GFP protec2on) •  Short-­‐Time Current Ra2ng -­‐ Average RMS current a device can carry, 2 seconds for load interrupter switches, 3 seconds for vacuum breakers •  Fault Close Ra2ng -­‐ Load Interrupter Switch -­‐ Maximum asymmetrical short circuit current it can close into and remain closed. Typical ra2ngs are: 40kA, 61kA and 80kA. –  Fault Rated – Switches with vacuum interrupters or circuit breakers with fault current interrup2ng ra2ngs. Vacuum circuit breakers are fault interrup2on rated in kA, 25kA (15kV only); 40kA and 50kA at 4.76kV, 8.25kV and 40kA, 50kA and 63kA at 4.76 and 15kV. Ra2ngs for 27kV are 16kA, 25kA or 40kA. Ra2ngs for 38 kV are 32 kA or 40 kA •  Close and Latch Ra2ng -­‐ Used with vacuum circuit breakers. Expressed in Crest current as maximum breaker can close into with opera2ng mechanism latching breaker in closed posi2on. Ra2ngs are 2.7 2mes breaker current interrup2ng ra2ng at maximum voltage ra2ng. 17 18 Medium Voltage Terminology (cont.) •  Insula2on systems employed in medium and high voltage equipment and installa2ons can be any of the following: –  Air –  Oil –  Vacuum –  SF6 What is SF6 Equipment? •  SF6 (sulfur hexafluoride) is a gas that is used in electrical power equipment. •  It is colorless, odorless, non-­‐flammable and chemically stable. •  This means that at room temperature it does not react with any other substance. –  Argon –  Freon •  Applies to circuit breakers, motor contactors, transformers and to gas insulated bus structures 19 •  SF6 is a very good electrical insulator and can effec2vely ex2nguish arcs, which makes high and medium voltage apparatus filled with SF6 highly popular. •  SF6 is about 6 2mes heavier than air. 20 5 9/30/14 Medium Voltage Terminology (cont.) •  Switchgear -­‐ Low Voltage Power Switchgear [ANSI/IEEE C37.20.1} –under 600 volt power switchgear typically with removable (draw out) low voltage power circuit breakers -­‐ Metal Clad Switchgear [ANSI/IEEE C37.20.2] – Over 600 volt switchgear where main bus is segregated into separate metal enclosed compartments from breaker cubicles, bus and outgoing cables. Draw out circuit breakers used. -­‐ Metal Enclosed Switchgear [ANSI/IEEE C37.20.3] –Over 600 volt switchgear with exposed but and typically interrupter switches in overall enclosure. ANSI/IEEE C37.20.4 covers interrupter switches. 21 22 NEC Defini2on of Qualified Person •  Qualified Person. One who has skills and knowledge related to the construc2on and opera2on of the electrical equipment and installa2ons and has received safety training on the hazards involved. •  FPN: Refer to NFPA 70E-­‐2004, Standard for Electrical Safety in the Workplace, for electrical safety training requirements. Design Concepts •  Understanding the different designs used for medium and high voltage power distribu2on •  ??? Should the electrical inspector have the same knowledge and electrical system training??? 23 24 6 9/30/14 Basic System Designs (cont.) Basic System Designs •  Typical medium voltage system configura2ons and voltages: •  Medium voltage systems configura2on and voltages (cont.) –  12,470 Volts 3Ø 3W Grounded Wye (7,200) -­‐-­‐2,400 Volts 3Ø 3W Delta –  13,200 Volts 3Ø 3W Delta or Grounded Wye (7,620) –  2,400/1,385 Volts 3Ø 3W Grounded Wye –  13,800 Volts 3Ø 3W Delta or Grounded Wye (7,970) –  4,160 Volts 3Ø 3W Delta –  20,800 Volts 3Ø 3W Grounded Wye (12,000) –  4,160/2,400 Volts 3Ø 3W Grounded Wye –  7,200 Volts 3Ø 3W Delta •  There are a number of other MV systems voltages above 20,800 volts but no commonality exists. Maximum typically will be 34,500 volts. Maximum MV 69 kV system voltage –  11,400 Volts 3Ø 3W Grounded Wye (6,582) –  12,000 Volts 3Ø 3W Grounded Wye (6,930) 25 26 Basic System Designs (cont.) Basic System Designs (cont.) •  Distribu2on system design op2ons: •  Designing power distribu2on systems for performance and reliability –  Radial system •  Con2nuity of Service -­‐ Commercial, manufacturing, process/
cri2cal process –  Primary selec2ve system •  Selec2vity -­‐ Isolate Faults – Short-­‐circuit current and 2me/
current coordina2on study, arc flash study –  Primary selec2ve & secondary selec2ve system –  Secondary selec2ve system –  Secondary spot network system •  Major Failure Problems -­‐ U2lity source, primary cable/
termina2ons, transformer, man or animals •  System Selec2on -­‐ U2lity source(s), other sources such as generators •  See the following single-­‐line diagrams courtesy of the Square D Company 28 27 7 9/30/14 Typical Radial System Design Typical Primary Selec2ve Design 29 Courtesy of: Square D Company Secondary Selec2ve Design 30 Courtesy of: Square D Company Primary/Secondary Selec2ve Design 31 Courtesy of: Square D Company 32 Courtesy of: Square D Company 8 9/30/14 Secondary Spot Network Design 33 Courtesy of: Square D Company Typical Double-­‐Ended (Tie-­‐Breaker) Design 34 Courtesy of: Square D Company High Voltage or Low Voltage? •  Low Voltage by NEC is under 600 volts with some excep2ons (There are recent changes moving this to 1000 Volts) The Voltages –  Wire and cable is 2000 Volts –  Grounding of systems over 1000 volts •  Low Voltage per IEEE is under 1000 volts •  Medium Voltage per IEEE is over 1000 up to 72,500 volts •  What are the voltage levels for low, medium, and high voltage electrical distribu2on systems? 35 36 •  High Voltage per IEEE is over 72,500 up to 230,000 volts 9 9/30/14 The Electrical Codes High Voltage or Low Voltage? (cont) •  Na2onal Electrical Code (NEC ) ANSI/NFPA 70 •  Extra High Voltage per IEEE is over 230,000 up to 765,000 volts •  Canadian Electrical Code Parts I & II •  Ultra High Voltage per IEEE is over 765,000 with systems opera2ng at 1,100,000 volts •  The Other Electrical Code –  Na2onal Electrical Safety Code (NESC) ANSI/IEEE C2 -­‐2012 •  Note: The NEC does not have a specific upper voltage limit but generally handles up to 35,000 volts (medium voltage) 37 Na-onal Electrical Code ® 2011 & 2014 – 90.2 •  Sec2on 90.2(A) provides what is covered by the NEC. •  Sec2on 90.2(B) provides what is not covered by the NEC. •  The defini2on of the term Service Point is important in establishing a point of coverage for the Codes that must be applied. •  Service Point. The point of connec2on between the facili2es of the serving u2lity and the premises wiring. Informa2onal Note: The service point can be described as the point of connec2on between where the serving u2lity ends and the premise wiring begins. The serving u2lity generally specifies the loca2on of the service point based on the condi2ons of service. 39 38 Na2onal Electrical Safety Code -­‐ 011 Scope •  Rules cover supply and communica2on lines, equipment, and associated work prac2ces employed by a public u2lity or private electric supply, communica2ons, railway, or similar u2lity in the exercise or func2on as a u2lity. •  NESC covers u2lity facili2es and func2ons up to the service point. •  NESC covers street and area lights (supplied overhead and underground) under the exclusive control of u2li2es (including their authorized contractors) or other qualified persons (such as those associated with an industrial complex). 40 10 9/30/14 Na2onal Electrical Code® Origin of the NEC •  ANSI Standard on the safe installa2on of electrical systems •  Model document suitable for adop2on by law – Annex G (Ar2cle 80) •  Purpose -­‐ Prac2cal safeguarding of persons and property from hazards arising from the use of electricity • 
•  Is not a design specifica2on or an instruc2on manual for untrained persons NEC is 117 years old The 1897 Edi2on was the first Na2onal Conference on Standard Electrical Rules Na2onal Board of Fire Underwriters Na2onal Fire Protec2on Associa2on American Na2onal Standards Ins2tute ANSI -­‐ 70 41 Over 600 Volt Rules in the NEC •  Ar2cle 328 MV Cable •  Ar2cle 399, Overhead Over 600 Volts •  Ar2cle 490, Equipment, Over 600 Volts, Nominal •  Parts of Other Ar2cles –  Part II of Art. 100 –  Parts III & IV of Art. 110 –  Part III of Art. 225 –  Part VIII of Art 230 –  Part IX of Art 240 –  Part X of Art 250 –  Part II of Art 300 – 
42 NEC Access to NESC •  Sec2on 90.2 (A) – FPN -­‐ for reference to the NESC, ANSI C2. •  Sec2on 90.2(C) – Gives AHJ authority to use NESC by Special Permission. Part V of Art 314 Part II of Art 368 Part III of Art 400 Part X of Art 430 Part II of Art 460 Part II of Art 470 Part IX of Art 690 Part VIII of Art 692 –  Specific Sec2ons of other Ar2cles [e.g. Sec2on 450.3(A)] 43 44 11 9/30/14 NESC Background The Na2onal Electrical Safety Code (NESC) is applicable to systems and equipment operated by electric, telephone and cable television u2li2es. Reviewing the Types of Medium and High Voltage Equipment The NESC covers basic provisions for safeguarding of persons from hazards arising from the installa2on, opera2on, and maintenance of electric supply sta2ons and overhead and underground electric supply and communica2on lines. The NESC as wriyen is a voluntary standard and is not a design manual. Equipment types and applicable product and manufacturing standards and different insula2on systems 45 46 Equipment Safety Standards Review of Electrical Equipment •  This por2on of the presenta2on reviews the types of medium voltage equipment available •  Equipment standards come from many organiza2ons –  ANSI/IEEE –  ANSI/NEMA –  ANSI/UL –  AEIC •  Also reviewed are the uses for various types of medium voltage equipment. 47 48 12 9/30/14 Equipment Safety Standards (cont.) METAL-CLAD SWITCHGEAR
•  Switchgear and Controlgear -­‐ ANSI C37 ANSI C37.20.2
–  Metal clad switchgear –  Metal enclosed switchgear –  Sta2on cubical switchgear –  Controlgear METAL-CLAD AND STATION-TYPE CUBICLE SWITCHGEAR
AC High Voltage Circuit Breakers Rated on a Symmetrical Current Basis
•  Breakers and Switches -­‐ ANSI C37 ANSI C37.04 Rating Structure
ANSI C37.06 Preferred Ratings
ANSI C37.09 Test Procedure
Maximum Design kV
Continuous Current
1200 1200
2000 2000
Short Circuit MVA Class
•  MAIN SWITCHING/INTERRUPTING DEVICE -­‐ Vacuum breaker; removable; drawout construcSon •  PRIMARY CIRCUIT -­‐ Grounded Metal Barriers •  LIVE PARTS ENCLOSED -­‐ Grounded Metal Compartments •  AUTOMATIC SHUTTERS -­‐ Grounded; breaker removable element •  INSULATED PRIMARY BUS •  MECHANICAL INTERLOCKS •  INSTRUMENTS/RELAYS -­‐ Secondary Wiring Isolated •  BREAKER ACCESS DOOR -­‐ Used for relays/instruments INSULATED -­‐ ISOLATED Short Circuit kA
49 40(36)
Insulation Level kV 60Hz 19
BIL 60
Short Time Rating: 3 seconds RMS sym. I
Close and Latch Rating: RMS sym. I kA x 2.7
Interrupting Time: 83ms or approximately 5 cycles
750 2000
1250 2650
52 52 13 9/30/14 490.24 Minimum Space Separa2on •  In field-­‐fabricated installa2ons, the minimum air separa2on between bare live conductors and between such conductors and adjacent grounded surfaces shall not be less than the values given in Table 490.24. •  These values shall not apply to interior por2ons or exterior terminals of equipment designed, manufactured, and tested in accordance with accepted na2onal standards. 53 54 490.21(A) Circuit Breakers Circuit Breakers •  (A)(1) Loca2on •  Circuit breakers installed indoors shall be mounted either in metal-­‐enclosed units or fire-­‐resistant cell-­‐mounted units, or they shall be permiyed to be open-­‐mounted in loca2ons accessible to qualified persons only. •  Circuit breakers used to control oil-­‐filled transformers shall either be located outside the transformer vault or be capable of opera2on from outside the vault. SURGE ARRESTERS DistribuSon-­‐Intermediate-­‐StaSon Class MOV-­‐Metal Oxide Varistor MCOV-­‐Maximum ConSnuous OperaSng Voltage EffecSvely Grounded System/Ungrounded/System MOV(kv)
•  Oil circuit breakers shall be arranged or located so that adjacent readily combus2ble structures or materials are safeguarded in an approved manner. 51 56 14 9/30/14 490.21(A) Circuit Breakers (cont.) 490.21(A) Circuit Breakers (cont.) •  (A)(2) Circuit breakers shall have the following equipment or opera2ng characteris2cs: •  (1) An accessible mechanical or other approved means for manual tripping, independent of control power. •  (2) Be release free (trip free). •  (3) If capable of being opened or closed manually while energized, main contacts that operate independently of the speed of the manual opera2on. •  (4) A mechanical posi2on indicator at the circuit breaker to show the open or closed posi2on of the main contacts. •  (5) A means of indica2ng the open and closed posi2on of the breaker at the point(s) from which they may be operated. •  (A)(3) Nameplate •  Circuit breakers shall have a permanent and legible nameplate showing manufacturer's name or trademark, manufacturer's type or iden2fica2on number, con2nuous current ra2ng, interrup2ng ra2ng in megavolt-­‐amperes (MVA) or amperes, and maximum voltage ra2ng. •  Modifica2on of a circuit breaker affec2ng its ra2ng(s) shall be accompanied by an appropriate change of nameplate informa2on. •  Note: May require re-­‐evalua-on by tes-ng lab or approval by the AHJ. 57 58 490.21(A)(4) Circuit Breakers -­‐ Ra2ng •  (1) The con2nuous current ra2ng shall not be less than the maximum con2nuous current through the circuit breaker. •  (2) The interrup2ng ra2ng shall not be less than the maximum fault current the circuit breaker will be required to interrupt, including contribu2ons from all connected sources of energy. •  (3) The closing ra2ng shall not be less than the maximum asymmetrical fault current into which the circuit breaker can be closed. •  (4) The momentary ra2ng shall not be less than the maximum asymmetrical fault current at the point of installa2on. •  (5) The rated maximum voltage shall not be less than the maximum circuit voltage. 59 60 15 9/30/14 62 Photo IAEI Archives 9/30/14 61 61 300.34 Conductor Bending Radius •  Non-­‐shielded conductors shall not be bent to a radius less than 8 2mes the overall diameter of the conductor. •  Shielded or lead-­‐covered conductors shall not be bent to a radius less than 12 2mes the overall diameter for during or a|er installa2on. •  For mul2conductor or mul2plexed single conductor cables having individually shielded conductors, the minimum bending radius is 12 2mes the diameter of the individually shielded conductors or 7 2mes the overall diameter, whichever is greater. 63 9/30/14 64 64 16 9/30/14 65 66 Metal-Clad Switchgear
Main Breaker Section
67 68 17 9/30/14 Circuit Breaker-Overcurrent Protection
Services 230.200 Comply with preceding sections plus additional
requirements or modifications.
Overcurrent protection is required.
Service disconnect can include Overcurrent Protection.
Overcurrent Protection consists of phase CTs and overcurrent
relays. 240.100(A)(1) gives details for feeder and branch circuits:
Metal-Clad Switchgear
Two High Feeder
•  Minimum of three overcurrent relays operated from three
current transformers.
Breaker Section
•  Three separate overcurrent relay elements can be part of a
single electronic relay unit.
69 70 Device 50 Instantaneous Overcurrent Relay
Device 51 Time Delay Overcurrent Relay
Typical 50/51 CT/Relay Connections
•  MV Circuit Breakers-overcurrent relays-provide protection
•  Separate device 50 instantaneous only is available for high
speed detection of phase or ground faults
• Usually the 50 instantaneous and 51 time delay functions are
combined together into one relay, 50/51 designation
• Current transformer input is required. Usually 5A secondary,
but 1A relays are available.
•  Single Ratio or Multi Ratio CT Decision
•  Residual Connection of CTs for 50/51 and 50N/51N
•  Zero Sequence CT for 50GS Feeder Breakers Only
71 72 18 9/30/14 490.21(B) Power Fuses and Fuseholders
(1) Use - Protect conductors and equipment. Parallel fuses permitted
with identical ratings.
(2) Interrupting rating-not less than available fault current
ANSI C37.20.3
(3) Voltage rating-maximum voltage rating not less than maximum
system voltage.
(4) Identification of Fuse Mounting-Nameplate showing type,
continuous current rating, interrupting rating and maximum voltage
Indoor AC Medium Voltage Switches
(5) Fuses expelling flame-must function without hazard.
Used in Metal Enclosed Switchgear
(6)Fuseholders-de-energized while being replaced, boric acid/CLF
ANSI C37.20.4
73 (7) High Voltage Fuses-metal enclosed switchgear and provided with
gang operated switch. Exception allows more than one switch for
74 single set of fuses.
74 490.21(E) Load Interrupter Switches
Permitted when used in conjunction with suitable fuses or circuit
breaker to interrupt faults currents. More than one switch may be
used to connect to alternate supply source. Primary Selective System
(1) Continuous current rating-equal/exceed current where installed.
490.21(E) Load Interrupter Switches (continued)
(5) Stored Energy for Opening-switch mechanism may be left in
uncharged position if a single movement opens the switch.
(2)Maximum voltage rating-equal/exceed maximum circuit voltage.
(3)Identification-Nameplate, type, continuous current rating,
interrupting rating, fault closing rating, maximum voltage rating.
(6) Supply Terminals- located either at the top or located to prevent
dropping of tools or fuses into energized bus. Barriers may be used .
(4)Switching of Conductors-operating mechanism location of switch
does not expose operator to energized parts and operable from
outside enclosure.
INTERRUPTER SWITCH: Fixed or Drawout -­‐ Fixed is normal MECHANICAL INTERLOCKS: Drawout -­‐ Fuse Door -­‐ Fixed Mounted POWER FUSES: Boric Acid or CLF BARE BUS: Insulator Supported BARRIERED COMPARTMENTS: Not Required INSTRUMENT TRANSFORMERS: Full Voltage, Fixed Mounted CONTROL WIRING/INSTRUMENTS: Isolated/Grounded Barriers ENCLOSURES: Indoor (NEMA 1), Outdoor (NEMA 3R), Categories A,B,C
77 Metal Clad & Metal Enclosed NEMA 3R Non Walk-In
ANSI C37.20.2 & C37.20.3 Enclosure Definitions
78 n  Metal-­‐Enclosed construcSon •  Category A u  NEMA 1 u  NEMA 3R –  Provide degree of protecSon against contact with enclosed equipment in ground level installaSons subject to deliberate, unauthorized acts by members of the unsupervised general public n  Direct drive mechanism. n  Permanently afached handle. n  Standardized 11 gauge enclosure. •  Category B n  Visible isolaSon viewing window. –  Used in the installaSons not subject to deliberate, unauthorized acts by member of unsupervised public and provides a degree of protecSon to unauthorized and untrained personnel against incidental contact with enclosed equipment. n  Fuse access door mechanically interlocked (Switch open & fuse de-­‐energized with door open). n  Provision for padlock. •  Category C n  Provision for Key Interlock. –  Enclosures are intended to provide a degree of protecSon against contact with enclosed equipment in secured installaSons intended to be accessible only to authorized persons. n  InterconnecSon coordinated with all transformers. n  OpSonal motor operator. 79 80 20 9/30/14 Load Interrupter Switch Ratings
Nominal Voltage (kV)
Max. Design Voltage (kV)
BIL (kV)
Frequency (Hz)
Continuous Amps
Interrupting Amps
Fault Close
(kA Asymmetrical)
Momentary Current
(kA Asymmetrical 10 Cycles)
Capacitor Switching
Short Time Rating
(kA 2 Seconds)
Dielectric Withstand
(kV 1 Minute)
Indoor solid material power fuse holder assembly (boric-­‐acid arc-­‐ex2nguishing type) Shown from le| to right are a refill kit, spring and cable assembly, fuse holder, and silencer 36
(1) C-UL Listed (tested to CSA C22.2 N0.31 and CSA 22.2 No. 193
(2) 61 kA Momentary is also available.
(3) Not UL Listed.
(4) For fused version only S&C boric acid fuses can be used.
81 81 82 Photo: NECH Exhibit 490.2 S&C Electric Co. Metal enclosed switchgear 83 Photo: Square D Company 84 21 9/30/14 EUSERC Utility Medium Voltage Metering Sections
Metering Sequence
Hot or Cold
Hot Sequence-APS,
SRP, Nevada Power,
Cold Sequence-SCE,
Work Space-Hot
Stick Rules
85 85 Photo: IAEI Archives 86 High Voltage Industrial Control Equipment
High Voltage Industrial Control Equipment
Basic Components Continued
ANSI/UL 347 2.2-7.2kV
Overload Protection-Current transformers used to feed overload sensing
in three phase configuration. A motor protection relay can be used that
provides more motor function protection
Basic Components
Metal Enclosed Bus-an assembly of rigid conductors with associated
connections, joints and insulating supports within a grounded metal
Controller-Class E1-Class E1 controllers employ their contacts for starting
and stopping a motor and interrupting short circuits or faults exceeding
operating overloads.
Isolation-non load break disconnect required and operated only after the
circuit is opened by controller and have visible evidence of the isolating
gap. Controller may be drawout for visible disconnect or fixed mounted
controller with NEC 2008 490.22 isolation compliance. Other option is for
controller to be drawout eliminating need for isolation disconnect switch.
Controller-Class E2- Class E2 controllers employ their contacts for starting
and stopping a motor and employ high-voltage motor circuit fuses for
interrupting short circuit or faults exceeding operating overloads.
Control device area is isolated from high voltage compartment. May have
separate plug disconnect for supplying control power from external
source for testing controller.
High-Voltage Motor Circuit Fuse- Class R short circuit protection only.
87 88 22 9/30/14 89 Photo: 9/30/14 IAEI Archives 90 TRANSFORMERS
Standard/Special Service Conditions
Standard Ambient Temperature Reference for all transformer types: 30
Degree C Average, 40 Degree C Maximum in any given 24 hour period.
Any other condition, de-rate or build special transformer.
ANSI C57.12.00 covers a wide range of reference ANSI standards
depending on type of construction.
BIL: Different BIL levels are specified in ANSI for different types of
transformers. Test similar to that shown for Metal-Clad and MEI
Three basic types: Pad-Mounted, Substation, and Station
Pad-Mounted are either live front construction or dead front construction,
ANSI C57.12.22 and C57.12.26 respectively for construction details. Units
are tamperproof and don’t require supervised access site construction.
Impedance: ANSI standard is 5.75%, +/- 7.5%, 750-5000 kVA, all types.
Altitude: 1000 meters, 3300 feet. Above these levels, dielectric level is
reduced, kVA reduced due to less cooling from air, Metal-Clad and MEI
have similar reductions for voltage, continuous current and BIL.
Others: step-up/step-down operation, special loading conditions-traction
transformers, transformers used for testing, parallel operation, and others
that require special design considerations.
91 Substation type have gauges, tap changer and other accessories mounted
on tank wall, bushings on each end, and require HV and LV sections for
incoming and outgoing cables. Supervised access site construction is
required for indoor or outdoor installation. ANSI C57.12.10 transformer
construction reference.
Dry Type, Solid Cast and Encapsulated
Station type are different from substation type in that bushings are
mounted on top of transformer for aerial incoming and outgoing cable
terminations. Supervised access site construction is required. Usually
applied in outdoor switching yards. ANSI C57.12.10
UL 1562 Standard-numerous references incorporating ANSI standards.
ANSI C57.12.01 General Requirements
ANSI C57.12.90 is test standard for liquid filled transformers. ANSI
C57.12.00 defines test classifications as Routine (production tests), Design
and Other. Other tests are conducted on a particular production
transformer by specification. Example BIL would be done on a design but
is not a production test.
ANSI C57.12.55 Enclosure Conformance and Test Conformance
Types of liquids: Mineral Oil (flammable) NEC 450.26 indoor and 450.27
outdoor, (RTemp discontinued), Beta fluid and Silicon (less
flammable)NEC 450.23 indoor/outdoor. New “veggie” liquids meet NEC
ANSI C57.12.91 Test Code for Dry Type Transformers
Temperature Rise: 65 (standard), 55/65 or 55 degrees C
ANSI C57.12.56 Thermal Evaluation Dry Type Insulation Systems
ANSI C57.12.60 Thermal Evaluation Solid Cast/Resin Encapsulated
Insulation Systems
NEC 450.3 Overcurrent Protection Primary/Secondary, Primary Only
NEC 450.9 Ventilation openings not blocked by walls. Required Marking.
Square D is 3” for 600V and below, 12” above 600V
( UL Listed perANSI)
Pad Mounted - Dead Front
Live Front
Substation Type
Flammable Mineral Oil
High Fire Point
R-Temp - 312ºC
Silicone - 350ºC
Beta Fluid-308oC
Temperature Rise
65 ºC, 55/65 º, 55 ºC
Windings AL or CU
(UL Listed UL1562)
Power Dry
150 ºC
115 ºC
80 ºC
AL or CU
Uni Cast
100 ºC
80 ºC
AL or CU
- Cast Primary
- Encapsulated VPI
185oC Insulation System
Power Cast
80 ºC
CU Only
- Cast Primary
- Cast Secondary
185oC Insulation System
220oC Insulation System
Fan Cooling 133%on VPI, 133% or 150%
on Uni Cast or Power Cast
Forced Air Cooling (except pad mounted)
115% 2000 kVA max, or 125% 2500 kVA
To 5000 kVA
95 9/30/14 96 96 24 9/30/14 TRANSFORMER OVERCURRENT
PROTECTION Table 450.3(A)
Primary/Secondary Overcurrent Protection Required Any Location
Transformer Impedance not more than 6%
-Primary Breaker - 600%FLC of Primary
Table 450.3(A)
-Secondary Breaker (above 600V) - 300% FLC Secondary
Supervised Installation-Any Transformer Impedance
-Note 3 A supervised location is a location where conditions of
maintenance and supervision ensure that only qualified persons
monitor and service the transformer installation.
-Secondary Fuse (above 600V) - 250% FLC Secondary
Primary Overcurrent Protection Only
-Primary Fuse -300% FLC of Primary
-Secondary Breaker or Fuse (600V or below) 125% FLC of
-Note #1 permits next highest standard rating to be used
-Maximum of Six Secondary devices - Sum must equal rating
97 97 of single device
Table 450.3(A)
-More than six secondary devices permitted
- Primary Breaker - 300% FLC of Primary
- Primary Fuse - 250% FLC of Primary
- No limit on number of secondary devices
98 Photo of gear with contact viewing window. Supervised Installation
Primary and Secondary Overcurrent Protection Required
Transformer Impedance not more than 6%
-Primary Breaker - 600% FLC of Primary
-Primary Fuse - 300% FLC of Primary
-Secondary Breaker (above 600V) -300% FLC of Secondary
-Secondary Fuse (above 600V) - 250% FLC of Secondary
-Major Difference- Secondary breaker or fuse 600V or
below - 250% FLC of secondary
-Maximum of Six Secondary Devices - Sum must equal
99 99 rating of single device
9/30/14 IAEI Archives Photo: 100 100 25 9/30/14 Cast Resin Transformer Core and coil assembly Oil-­‐filled transformer 101 Photo: Delixi Group Co., LTD. Photo: IAEI Archives 103 Photo: Taishan Group Co., L102 TD. Photo: IAEI Archives 104 26 9/30/14 NEC CODE ISSUES ON SUBSTATIONS
2008 section 230.200 all services above 600V must comply with applicable
provisions of the previous sections. Watch 230.204(A) Oil switches and air,
oil, vacuum and SF6 circuit breakers-isolation requirement
Scope of this standard is to coordinate equipment by assisting in
component selection with various combinations of incoming sections,
transformer sections, outgoing sections, and transition (throat) sections.
Main service medium voltage switchgear may have ground fault protection
but secondary also requires ground fault per 230.95. Section 240.13 applies
and feeder sections article 215 and 225.
Primary Unit Substation-Outgoing Section is above 1000V.
Secondary Unit Substation- Outgoing Section is 1000V or less
Incoming Sections can be a variety of equipment, Metal-Clad, MEI of High
Voltage Industrial Control
Transformer Section (rating) determines ratings of both incoming and
outgoing section ratings. Can be liquid filled substation type, or any of the
dry type. Pad-Mounted transformers are not considered substation type.
Outgoing Section could be Metal-Clad, MEI, HV Industrial Control, or a
combination of them. LV could be LV Power Breaker Switchgear UL 1558,
ANSI C37.20.1, UL 1066 ANSI C37.13 on breakers, Switchboards per UL
891, or Motor Control Centers per UL 845.
105 105 Methods of Grounding • 
Service (SUSE) label is needed on secondary equipment- No this is not
service equipment by NEC definition of service point. But 2008 NEC
250.30 applies for separately derived systems. Bonding jumper, grounding
electrode conductor connection apply and neutral disconnect link is
required by UL 891 on Switchboards and 1558 on Switchgear
Secondary Main is not required but Table 450.3(A) still applies depending
on supervised/unsupervised interpretation.
Transformer Secondary Conductors- 240.21(C)(4) permits conductors
outdoors from building to be furnished without overcurrent protection at
transformer. Must terminate in a single overcurrent device.
106 Methods of grounding over 1,000 volts Effec2vely grounded through surge arresters Reactance grounded through an inductor Low resistance grounded High resistance grounded Solidly grounded 107 108 27 9/30/14 Impedance Grounded Neutral Systems Impedance grounded systems •  Accomplished by reactance grounding, resistance grounding, or high-­‐resistance grounding •  Shall be grounded in accordance with the provisions of 250.186 109 Grounding using grounding-­‐type transformer 111 110 Use of zigzag grounding transformer 112 28 9/30/14 Single Point Grounded System Single point grounded system •  This method permiyed in accordance with 250.184(B) •  System permiyed to be supplied from a separately derived system or a mul2grounded neutral system with an equipment grounding conductor connected to the mul2grounded neutral at the source of a single point grounded neutral system •  Grounding electrode is required for the system •  See the remainder of the requirements in 250.184(B) 113 Mul2grounded Neutral Conductor •  Shall be of sufficient ampacity but not less than 33-­‐1/3 % of the phase conductors •  Shall be grounded at each transformer and addi2onal loca2ons by connec2on to grounding electrode •  At least one grounding connec2on shall be installed every 400 m (1300 |) •  Maximum distance between any two adjacent electrodes shall not be more than 400 m (1300 |) •  In mul2grounded shielded cable systems, the shields of the cables shall be grounded at each cable joint exposed to personnel contact 115 114 114 Mul2grounded neutral systems 250.184(C) 116 29 9/30/14 230.206 Overcurrent Devices as Disconnec2ng Means 230.205 Disconnec2ng Means •  (A) Loca2on –  Shall be located according to 230.70 •  (B) Type –  Shall simultaneously disconnect all ungrounded service conductors –  Shall have a fault-­‐closing ra2ng not less than the maximum short-­‐circuit current available –  Fuses shall be permiyed to contribute to the fault-­‐closing ra2ng •  Where the circuit breaker or alterna2ve for it, as specified in 230.208 for service overcurrent devices, meets the requirements specified in 230.205, they shall cons2tute the service disconnec2ng means. •  (C) Remote Control –  Permiyed in separate buildings or structures for mul2-­‐
building, industrial installa2ons under single management. Note: Not required to be SUSE as required for equipment 600 V or less [230.66] 117 230.208 Protec2on Requirements •  A short-­‐circuit protec2ve device shall be provided on the load side of, or as an integral part of, the service disconnect, and shall protect all ungrounded conductors that it supplies. •  The protec2ve device shall be capable of detec2ng and interrup2ng all values of current, in excess of its trip se~ng or mel2ng point, that can occur at its loca2on. •  A fuse rated in con2nuous amperes not to exceed three 2mes the ampacity of the conductor, or a circuit breaker with a trip se~ng of not more than six 2mes the ampacity of the conductors, shall be considered as providing the required short-­‐circuit protec2on. 9/30/14 119 9/30/14 118 118 230.208 Protec2on Requirements •  (A) Equipment Type. Equipment used to protect service-­‐entrance conductors shall meet the requirements of Ar2cle 490, Part II. •  (B) Enclosed Overcurrent Devices. The restric2on to 80 percent of the ra2ng for an enclosed overcurrent device for con2nuous loads shall not apply to overcurrent devices installed in systems opera2ng at over 600 volts. 120 30 9/30/14 230.209 Surge Arresters (Lightning Arresters) •  Surge arresters installed in accordance with the requirements of Ar2cle 280 shall be permiyed on each ungrounded overhead service conductor. 121 9/30/14 230.211 Metal-­‐Enclosed Switchgear •  Service equipment, including instrument transformers, shall conform to Ar2cle 490, Part I. 122 9/30/14 Ar2cle 240 Part IX •  Metal-­‐enclosed switchgear shall consist of a substan2al metal structure and a sheet metal enclosure. •  Where installed over a combus2ble floor, suitable protec2on thereto shall be provided. 9/30/14 230.210 Service Equipment – General Provisions 123 •  Overcurrent Protec2on Over 600 Volts Nominal –  240.100 Feeders and Branch Circuits –  240.101 Addi2onal Requirements for Feeders 124 31 9/30/14 240.100 Feeders and Branch Circuits 240.100 Feeders and Branch Circuits (cont.) •  (1) Overcurrent Relays and Current Transformers •  (A) Loca2on and Type of Protec2on. Feeder and branch-­‐circuit conductors shall have overcurrent protec2on in each ungrounded conductor located at the point where the conductor receives its supply. •  Overcurrent protec2on is permiyed at an alterna2ve loca2on in the circuit when designed under engineering supervision that includes but is not limited to considering the appropriate fault studies and 2me–
current coordina2on analysis of the protec2ve devices and the conductor damage curves. •  Circuit breakers used for overcurrent protec2on of 3-­‐phase circuits shall have a minimum of three overcurrent relay elements operated from three current transformers. The separate overcurrent relay elements (or protec2ve func2ons) shall be permiyed to be part of a single electronic protec2ve relay unit. •  (2) Fuses A fuse shall be connected in series with each ungrounded conductor. •  The overcurrent protec2on shall be permiyed to be provided by either 240.100(A)(1) or (A)(2). 125 126 240.100(B) Protec2ve Devices 240.100(C) Conductor Protec2on •  The protec2ve device(s) shall be capable of detec2ng and interrup2ng all values of current that can occur at their loca2on in excess of their trip-­‐se~ng or mel2ng point. •  The opera2ng 2me of the protec2ve device, the available short-­‐circuit current, and the conductor used shall be coordinated to prevent damaging or dangerous temperatures in conductors or conductor insula2on under short-­‐circuit condi2ons. 127 •  Vacuum Circuit Breakers -­‐ minimum of three overcurrent relays operated from three CTs. Can be individual relay elements or part of a single electronic protec2ve relay unit. ANSI designa2on for relay func2ons is 50 -­‐ instantaneous, 51 -­‐ 2me delay. •  Load Interrupter Switches -­‐ Fusible -­‐ two types available, Current Limi2ng or Boric Acid with replaceable refills. One fuse in each ungrounded conductor 128 32 9/30/14 Cable Shields and Stress Reduc2on 240.101 Addi2onal Requirements for Feeders •  The con2nuous ampere ra2ng of a fuse shall not exceed three 2mes the ampacity of the conductors. •  The long-­‐2me trip element se~ng of a breaker or the minimum trip se~ng of an electronically actuated fuse shall not exceed six 2mes the ampacity of the conductor. •  Conductors tapped to a feeder shall be permiyed to be protected by the feeder overcurrent device where that overcurrent device also protects the tap conductor. •  Solid dielectric insulated conductors operated above 2000 volts in permanent installa2ons shall have ozone-­‐resistant insula2on and shall be shielded •  All metallic insula2on shields shall be grounded through an effec2ve grounding path mee2ng the requirements of 250.4(A)(5) or 250.4(B)(4). •  Shielding shall be for the purpose of confining the voltage stresses to the insula2on –  The shield is not a subs2tute for the equipment grounding conductor! 129 Ar2cle 110 Requirements 130 NEC Working Space Requirements •  Ar2cle 110 (110.30 to 110.40) Part III is specific for over 600 Volts •  Sec2on 110.30 •  110.34 Work Space and Guarding. (cont’d) •  Table 110.34(A) Minimum Depth of Clear Working Space at Electrical Equipment Part I General Requirements apply to under and over 600 Volt installa2ons •  Table 110.34(E) Eleva2on of Unguarded Live Parts Above Working Space 131 132 33 9/30/14 Ar2cle 110 Requirements (cont.) •  Sec2on 110.31 Enclosures to limit access to qualified persons only •  Sec2ons 110.32, 100.33, 100.34 -­‐ Working space and guarding –  Rooms, fences, metal enclosures locked, eleva2on –  Service equipment and foreign systems 133 9/30/14 134 134 110.34(C) Locked Rooms or Enclosures •  Entrances to buildings, vaults, rooms, or enclosures containing exposed live parts or exposed conductors opera2ng at over 600 volts, nominal, shall be kept locked unless such entrances are under observa2on of qualified persons. •  Warning signs shall be provided to read as follows: DANGER – HIGH VOLTAGE – KEEP OUT 9/30/14 135 135 136 34 9/30/14 Key Words 9/30/14 137 137 138 QUESTIONS THANK YOU FOR YOUR ATTENTION Chris, Chuck and Chuck 139 140 35