Low Voltage Switchgear: Design & Calculation Internal OBJECTIVE • To acquire basic LVSG design & construction • Understand the critical elements of switchgear • Calculate the equivalent busbar for the LVSG Internal CONTENTS • Definition • Construction • How to design? Internal DEFINITION – LVSG • Designed for switching and protection of low voltage equipment • Used both to de-energize equipment to allow work to be done and to clear faults downstream • LVSG range 24VDC – 690VAC Internal LVSG CONSTRUCTION • Enclosure • Busbar • Incoming , outgoing devices & auxiliary Circuits Internal CONTENTS • Definition • Construction • How to design? Internal ENCLOSURE • A part providing a specified degree of protection of equipment against certain external influences and a specified degree of protection against approach to or contact with live parts and moving parts • Housing affording the type and degree of protection suitable for the intended application Internal ENCLOSURE • Consists of the following: • Functional unit • Section • Sub-section • Compartment • Partition • Barrier • IP Rating • Forms of Separation Internal ENCLOSURE • Consists of the following: • Functional Unit – part of an assembly comprising all the electrical and mechanical elements that contribute to the fulfilment of the same function • Section • Sub-section • Compartment • Partition • Barrier • IP Rating • Forms of Separation Internal ENCLOSURE • Consists of the following: • Functional Unit • Section – constructional unit of an assembly between two successive vertical delineations • Sub-section • Compartment • Partition • Barrier • IP Rating • Forms of Separation Internal ENCLOSURE • Consists of the following: • Functional Unit • Section • Sub-section – constructional unit of an assembly between two successive horizontal or vertical delineations of compartment • Partition • Barrier • IP Rating • Forms of Separation Internal ENCLOSURE • Consists of the following: • Functional Unit • Section • Sub-section • Compartment – section or sub-section enclosed necessary for interconnection, control or ventilation • Partition • Barrier • IP Rating • Forms of Separation Internal ENCLOSURE • Consists of the following: • Functional Unit • Section • Sub-section • Compartment Partition • Partition – part of the enclosure of a compartment separating it from other compartments • Barrier • IP Rating • Forms of Separation Internal ENCLOSURE • Consists of the following: • Functional Unit • Section • Sub-section Barrier • Compartment • Partition • Barrier – part providing protection against direct contact from any usual direction of access • IP Rating • Forms of Separation Internal IP RATING (IEC 60529) Degrees of protection provided by enclosures (IP Code) IP XX Internal IP Rating (IEC 60529) Description Degrees of protection provided by enclosures (IP Code) IP XX First Character Protection against ingress of solid foreign objects Internal 0 No Protection 1 Protected against solid foreign objects of 50 mm ∅ and greater 2 Protected against solid foreign objects of 12,5 mm ∅ and greater 3 Protected against solid foreign objects of 2,5 mm ∅ and greater 4 Protected against solid foreign objects of 1,0 mm ∅ and greater 5 Dust-protected 6 Dust-tight IP Rating (IEC 60529) Description Degrees of protection provided by enclosures (IP Code) IP XX Second Character Protection against ingress of water with harmful effects Internal 0 No Protection 1 Protected against vertically falling water drops 2 Protected against vertically falling water drops when enclosure tilted up to 15° 3 Protected against spraying water @ 60° on either side 4 Protected against splashing water 5 Protected against water jets 6 Protected against powerful water jets 7 Protected against the effects of temporary immersion in water 8 Protected against the effects of continuous immersion in water QUIZ # 1 IP 00 No protection at all Internal QUIZ # 2 IP 54 5 – Dust protected 4 – Protected against splashing water Internal QUIZ # 3 IP 30 3 – Protected against solid foreign objects of >2,5 mm ∅ 0 – No protection against water Internal QUIZ # 4 IP 65 6 – Dust-tight 5 – Protected against water jets Internal QUIZ # 5 IP 31 3 – Protected against solid foreign objects of 2,5 mm ∅ and greater 1 – Protected against vertically falling water drops Internal NEMA Rating NEMA Definitions Rating NEMA Definitions Enclosures constructed for either indoor or outdoor use to provide a degree of protection to personnel against incidental contact with the enclosed equipment; to provide a degree of protection against falling dirt, rain, sleet, snow, windblown dust, splashing water, hose-directed water, & corrosion; & that will be undamaged by thee external formation of ice on the enclosure Enclosures constructed for indoor use to provide a degree of protection to personnel against incidental contact with the enclosed equipment; to provide a degree of protection against falling dirt; against settling airborne dust, lint, fibers, & flyings; & to provide a degree of protection against dripping & light splashing of liquids. Enclosures constructed for either indoor or outdoor use to provide a degree of protection to personnel against incidental contact with the enclosed equipment; to provide a degree of protection against falling dirt; against hose-directed water & the entry of water during occasional temporary submersion at a limited depth; & that will be undamaged by the external formation of ice on the enclosure. Enclosures constructed for either indoor or outdoor use to provide a degree of protection to the personnel against incidental contact with the enclosed equipment; to provide a degree of protection against falling dirt; against hose-directed water & the entry of water during prolonged submersion at a limited depth; & that will be undamaged by the external formation of ice on the enclosure 1 Enclosures constructed for indoor use to provide a degree of protection to personnel against incidental contact with the enclosed equipment & to provide a degree of protection against falling dirt 4X 2 Enclosures constructed for indoor used to provide a degree of protection to personnel against incidental contact with the enclosed equipment, to provide a degree of protection against falling dirt, & to provide a degree of protection against dripping & light splashing of liquids 5 3 Enclosures constructed for either indoor or outdoor used to provide a degree of protection to personnel against incidental contact with the enclosed equipment; to proved a degree of protection against falling dirt, rain, sleet, snow, & windblown dust; & that will undamaged by external formation of ice on the enclosure 6 3R Enclosures constructed for either indoor or outdoor used to provide a degree of protection to personnel against incidental contact with the enclosed equipment; to provide a degree of protection against falling dirt, rain, sleet, & snow; & that will be undamaged by external formation of ice on the enclosure 6P 3S Enclosures are constructed for either indoor or outdoor use to provide a degree of protection to personnel against incidental contact with the enclosed equipment; to provide a degree of protection against falling dirt, rain, sleet, snow, & windblown dust; & in which the external mechanism(s) remain operable when ice laden. 12 & 12K Enclosures constructed (without knockouts) for indoor use to provide a degree of protection to personnel against incidental contact with the enclosed equipment; to provide a degree of protection against falling dirt; against circulating dust, lint, fibers, & flying; & against dripping & light splashing of liquids 4 Enclosures constructed for either indoor or outdoor use to provide a degree of protection to personnel against incidental contact with the enclosed equipment; to provide a degree of protection against falling dirt, rain, sleet, snow, windblown dust, splashing water, & hose-directed water; & that will be undamaged by the external formation of ice on the enclosure 13 Enclosures constructed for indoor use to provide a degree of protection to personnel against incidental contact with the enclosed equipment; to provide a degree of protection against falling dirt; against circulating dust, lint, fibers, & flyings; & against the spraying, splashing, & seepage of water, oil, & noncorrosive coolants. Internal IP vs NEMA Are they the same? Internal FORMS OF SEPARATION • Based from IEC 61439-2 • Protection against contact with live parts belonging to the adjacent functional units • Protection against the passage of solid foreign bodies from one unit of an assembly to an adjacent unit. • Note: forms of separation is a guide Internal FORMS OF SEPARATION • Form 1 • Form 2 • Form 3 • Form 4 Internal FORMS OF SEPARATION • Form 1 – no separation FORM • Form 2 – separation of bus-bars from the functional units CONSTRUCTION TYPE 1 2a • Form 3 – separation of bus-bars, separation of all functional units from one another, but not their outgoing terminals 2b Type 1 Type 2 • Form 4 – separation of bus-bars, separation of all functional units from one another including their outgoing terminals 3a 3b Type 1 Type 2 Internal FORMS OF SEPARATION • Form 1 – no separation • Form 2 – separation of bus-bars from the functional units FORM CONSTRUCTION TYPE 4a Type 1 Type 2 • Form 3 – separation of bus-bars, separation of all functional units from one another, but not their outgoing terminals Type 3 4b • Form 4 – separation of bus-bars, separation of all functional units from one another including their outgoing terminals Type 4 Type 5 Type 6 Type 7 Internal FORMS OF SEPARATION • Form 1 – no segregation of busbar, terminals, cables & functional unit • Advantage: • Cheap • Fast fabrication • Air circulation • Disadvantage: • Possible damage to adjacent functional unit during arc flash Internal FORMS OF SEPARATION • Form 2a - Busbars are separated from functional units only - Functional units are not separated from each other and not separated from incoming or outgoing termination • Advantage: value engineering • Disadvantage: Can affect other functional units during arcflash Internal FORMS OF SEPARATION • Form 2b – Type 1 - Busbars are separated from functional units - Separation is thru insulation Heat Shrinkable Sleeve 1kV – 36kV PVC Busbar Sleeve Tagging only Internal FORMS OF SEPARATION • Form 2b – Type 2 - Busbars/conductor are separated from functional units via partitions - Functional units are not separated Internal FORMS OF SEPARATION • Form 3a - Busbars are separated from functional units - Functional units are separated from each other - Functional units are separated from incoming and outgoing terminals - Incoming and outgoing terminals are not separated from each other Internal FORMS OF SEPARATION • Form 3b – Type 1 - Busbars are separated from functional units - Functional units are separated from each other - Terminals for external conductors are separated from the respective functional unit and the busbars - Busbars with insulation cover ` Internal FORMS OF SEPARATION • Form 3b – Type 2 - Busbars are separated from functional units - Functional units are separated from each other - Terminals for external conductors are separated from the respective functional unit and the busbars - Busbar separation is thru barrier or partition Internal FORMS OF SEPARATION • Form 4a – Type 1 - Busbars are separated from functional units - Functional units are separated from each other - Separation of terminals for external conductors from other terminals and from the busbars - Busbar is with insulation Internal FORMS OF SEPARATION • Form 4a – Type 2 - Busbars are separated from functional units - Functional units are separated from each other - Separation of terminals for external conductors from other terminals and from the busbars - Busbar separation is thru barrier or partition Internal FORMS OF SEPARATION • Form 4a – Type 3 - Busbars are separated from functional units - Functional units are separated from each other - Individual, integral cable glanding facilities are to be provided for each circuit Internal FORMS OF SEPARATION • Form 4b – Type 4 - Busbars are separated from functional units - Functional units are separated from each other - Terminals for external conductors from their own functional unit, other sets of terminals and from the busbars Internal FORMS OF SEPARATION • Form 4b – Type 5 - Busbars are separated from functional units - Functional units are separated from each other - Terminals for external conductors from their own functional unit, other sets of terminals and from the busbars - Separation of terminals for external conductors to be achieved by insulated coverings. Internal FORMS OF SEPARATION • Form 4b – Type 6 - Busbars are separated from functional units - Functional units are separated from each other - Terminals for external conductors from other terminals and from the busbars Internal FORMS OF SEPARATION • Form 4b – Type 7 - Busbars are separated from functional units - Functional units are separated from each other - Terminals for external conductors from other terminals and from the busbars - Individual, integral cable glanding facilities are to be provided for each circuit. Internal BUSBAR • Low-impedance conductor to which several electric circuits can be separately connected • Backbone of LVSG • Main Busbar • Distribution Busbar Internal BUSBAR DESIGN CONSIDERATIONS • Material • Busbar Jointing • Calculation Internal MATERIAL Conductor material needs the following properties: • Low electrical and thermal resistance • High mechanical strength in tension, compression and shear • High resistance to fatigue failure • Low electrical resistance of surface films • Ease of fabrication • High resistance to corrosion • Competitive first cost and high eventual recovery value. Internal MATERIAL PROPERTY (@20C) COPPER (C101) ALUMINUM (1350) Electrical Conductivity (Annealed) % IACS 101 61 Electrical Resistance (Annealed) mΩ mm 17.2 28.3 Temperature Coefficient of Resistivity per K 0.0039 0.004 Thermal Conductivity W/m-K 397 230 Specific Heat J/kg-K 385 900 Coefficient of Expansion per K 17 x 10-6 23 x 10-6 Tensile Strength (Annealed) N/mm2 200-250 50-60 Tensile Strength (half hard) N/mm2 260-300 85-100 0.2% Proof Strength (annealed) N/mm2 50-55 20-30 0.2% Proof Strength (half hard) N/mm2 170-200 60-65 Elastic Modulus kN/mm2 116-130 70 kg/m2 8910 2700 °C 1083 660 Density Melting Point Internal MATERIAL Temperature Effect on Conductivity – Conductivity varies with temperature π = π 20 (1 + πΌ20βπ) Where: π − ππππππ πππππ’ππ‘ππ πππ ππ π‘ππππ @ 200°πΆ, Ω π 20 − πππππ’ππ‘ππ πππ ππ π‘ππππ @ 20β, Ω πΌ20 − π‘πππππππ‘π’ππ πππππππππππ‘ of resistance @ 20β, πππ πΎ βπ − π‘πππππππ‘π’ππ ππππππππππ, πΎ βπ = ππ − 20 ππ − π‘πππππππ‘π’ππ ππππππππππ, πΎ Internal BUSBAR JOINTING • Jointing Considerations • Jointing Method Internal JOINTING CONSIDERATION • Joint resistance • Streamline effect • Contact resistance • Machining busbars Internal JOINTING CONSIDERATION Sizes of the contact areas Contact area = 5 x cross section area Ac = 5 x Ab Lc = 5 x tb Ac Ab Internal JOINTING CONSIDERATION • Joint resistance – clamped or bolted joint is made by bringing together two flat surfaces under controlled (and maintained) pressure • Streamline effect π π = π π + π π π π − joint resistance π π − spreading resistance • Contact resistance π π − πππ‘ππππππ πππ ππ π‘ππππ • Machining busbars Internal JOINTING CONSIDERATION • Joint resistance • Streamline effect – current flow to the overlap related to the ratio of busbar joint overlap & thickness • Contact resistance • Machining busbars Internal JOINTING CONSIDERATION • Joint resistance π π ππ π= = π π π π ππ • Streamline effect – current flow to π − resistance ratio the overlap related to the ratio of π π − resistance of overlap, μΩ busbar joint overlap & thickness π π − resistance of busbar, μΩ π − resistivity of busbar, μΩ • Contact resistance π − busbar width, ππ π − busbar thickness, ππ • Machining busbars Internal JOINTING CONSIDERATION • Joint resistance • Streamline effect • Contact resistance – the contact interface between the 2 faces of a busbar joint consists of a large number of separate point contacts • Condition of contact surface • Contact pressure Internal JOINTING CONSIDERATION • Condition of contact surface o dirt on busbar surface prior to jointing affects conductivity o busbar surface should be cleaned from contaminants prior to jointing o purpose of coating (tin, nickel, silver) is to prevent re oxidation or corrosion of busbar Internal JOINTING CONSIDERATION • Condition of contact surface o Nickel plating o a process that involves depositing a layer of nickel onto a copper substrate o this layer provides a protective barrier that enhances the durability and resistance of the copper to corrosion, wear, and tarnishing Internal JOINTING CONSIDERATION • Condition of contact surface o Silver plating o providing stable contact resistance and a low maximum operating temperature that increase the service life of the bus joint. Internal JOINTING CONSIDERATION • Condition of contact surface o Tin plating o the most versatile finish for copper bus bars. o provides excellent corrosion resistance for components susceptible to tarnish under a wide range of environmental conditions. electronics. Internal JOINTING CONSIDERATION • Contact Pressure π = πΎπΉπ· o The appropriate torque for each bolt size depends on the bolt π − tightening torque (Nm) material and the maximum πΎ − constant, often referred to as the ‘nut factor operating temperature expected. πΉ − force (kN) o Contact resistance falls rapidly with increasing pressure π· − nominal bolt diameter (mm) Internal JOINTING CONSIDERATION Nut Factors for Different States of Lubrication BOLT LUBRICATION NUT FACTOR DRY 0.20 – 0.22 CONTACT ACID COMPOUND 0.19 – 0.21 BOUNDARY LUBRICANT (MO2S) 0.15 – 0.16 Typical Thread Characteristics Internal JOINTING CONSIDERATION EXAMPLE: The proof load for a M30 metric bolt grad 8.8 is 337,000N. Calculate torque required to achieve this tension with a dry bolt with 0% lubrication. π = πΎπΉπ· π = (0.2)(337ππ)(30mm) π = 2022ππ Internal JOINTING CONSIDERATION • Joint resistance • Streamline effect • Contact resistance • Machining busbars o Copper is a soft, “greasy” or “sticky” metal in terms used in the trade o shaping is generally carried out dry, but lubrication is necessary for high-speed cutting or drilling operations (up to 50 m/mn). Internal JOINTING CONSIDERATION • Joint resistance • Streamline effect • Contact resistance • Machining busbars o Cutting o Punching π = πΏ1 + πΏ2 o Bending Internal BUSBAR THICKNESS MINIMUM BENDING RADIUS Upto 10mm 1t 11 – 25mm 1.5t 26 – 50mm 2t JOINTING METHODS • Bolted Joints • Welded Joints • Soldered Joints • Clamped Joints • Riveted Joints Internal JOINTING METHODS • Bolted Joints – formed by overlapping the bars and bolting through the overlap area • Welded Joints • Soldered Joints • Clamped Joints • Riveted Joints Internal JOINTING METHODS Bar Width mm Joint Overlap mm Joint Area mm2 Number of Bolts Coarse Thread Bolt Torque Nm Hole Size mm Washer Diameter mm Washer Thickness mm 16 32 512 2 M6 7.2 7 14 1.8 20 40 800 2 M6 7.2 7 14 1.8 25 60 1500 2 M8 17 10 21 2.0 30 60 1800 2 M8 17 10 21 2.0 40 70 2800 2 M10 28 11.5 24 2.0 50 70 3500 2 M12 45 14 28 2.2 60 60 3600 4 M10 28 11.5 24 2.7 80 80 6400 4 M12 45 14 28 2.2 100 100 1000 5 M12 45 15 28 2.7 120 120 14400 5 M12 45 15 28 2.7 160 160 25600 6 M16 91 20 28 2.7 200 200 40000 8 M16 91 20 28 2.7 Internal JOINTING METHODS • Bolted Joints • Welded Joints – made by butting the ends of the bars and welding • Soldered Joints • Clamped Joints • Riveted Joints Internal JOINTING METHODS • Bolted Joints • Welded Joints • Soldered Joints – rarely used for busbars unless they are reinforced with bolts or clamps since heating under short-circuit conditions can make them both mechanically and electrically unsound. Internal JOINTING METHODS • Bolted Joints • Welded Joints • Soldered Joints • Clamped Joints – formed by overlapping the bars and applying an external clamp around the overlap. Internal JOINTING METHODS • Bolted Joints • Welded Joints • Soldered Joints • Clamped Joints • Riveted Joints – similar to bolted joints but difficult to control the contact pressure Internal BUSBAR CALCULATION FACTORS • Busbar Cross Section • Arrangement & mounting • Altitude • Short circuit resistance & its support Internal BUSBAR CALCULATION FACTORS • Heat generated by a busbar • DC: Heat is generated per unit length of a conductor carrying a direct current, πΌ 2 π ππ • AC: resistance is increased due to π = πΌ 2 π 0 π, W/mm πΌ − current, A π 0 − dc resistance per length, Ω/ππ tendency to flow to outer surface π − skin effect π ππ π= π ππ π ππ − ππππππ‘ππ£π ππ πππ ππ π‘ππππ, Ω Internal BUSBAR CALCULATION FACTORS πΌ − current, A o Flat Bars @ 40°C A − cross sectional area, ππ2 π΄0.5 π0.39 π 0.61 πΌ = 1.02 [ 1 + πΌπ π]0.5 p − conductor perimeter, mm θ − temperature β πππ‘π€πππ conductor & air, °πΆ o Hollow Round Bars @ 40°C α − temperature coefficient, per β π΄0.5 π0.36 π 0.61 πΌ = 1.13 [ 1 + πΌπ π]0.5 ρ − resistivity of copper, μΩmm πΌππ = o Solid Round Bars @ 40°C π΄0.68 π 0.61 πΌ = 1.78 [ 1 + πΌπ π]0.5 Internal πΌππ π ππ π ππ BUSBAR CALCULATION FACTORS πΌ − current, A o Flat Bars @ 50°C A − cross sectional area, ππ2 πΌ = 7.73π΄0.5 π0.39 p − conductor perimeter, mm o Hollow Round Bars @ 50°C πΌ = 8.63π΄0.5 π0.36 πΌππ = o Solid Round Bars @ 50°C πΌ = 13.6π΄0.68 Internal πΌππ π ππ π ππ BUSBAR CALCULATION FACTORS • Lamination or Parallel connection • It is the combination of another busbar in parallel • Additional busbar to increase the ampacity required • This is due to obstruction to free air (convection & radiation) • Recommended spacing = busbar thickness Internal BUSBAR PLY MULTIPLYING FACTOR 2 1.8 3 2.5 4 3.2 5 3.9 6 4.4 8 5.5 10 6.5 BUSBAR CALCULATION FACTORS A copper busbar @ 50C & 50Hz, with the following dimension: 100 x 5mm, S=1.12 • Determine the DC current • Determine the AC current • Determine the AC current if parallel with 3 bars Internal BUSBAR CALCULATION FACTORS A copper busbar @ 50C & 50Hz, with the following dimension: 100 x 5mm, S=1.12 • Determine the DC current • Determine the AC current • Determine the AC current if parallel with 3 bars Given: copper busbar = 100 x 5mm, 50Hz, @ 50C, S=1.12 Required: Idc, Iac, Iac with 3 // bars Internal BUSBAR CALCULATION FACTORS Solution: π° = π. πππ¨π.π ππ.ππ πΌππ = 1314.75 π₯ 2.5 π΄ = 100π₯5 = 500ππ2 π°ππ = π, πππ. πππ¨ @ ππππ ππππππ π = 2 100 + 5 = 210ππ πΌ = 7.73(500)0.5 (210)0.39 π°π π = π, ππππ¨ π = 1.12 = 1.058 1,391π΄ πΌππ = 1.058 π°ππ = ππππ. πππ¨ Internal BUSBAR CALCULATION FACTORS πΌππ’π πππ = πΌπβπππ‘ π₯ π1 π₯ π2 π₯ π3 π₯ π4 π₯ π5 πΌππ’π πππ − πππππ’πππ‘ππ ππ’π πππ πππππππ‘π¦ πΌπβπππ‘ − ππ’πππππ‘ π£πππ’π π π‘ππ‘ππ ππ πβπππ‘ π1 , π2 , π3 , π4 , π5 − ππ’ππ‘ππππ¦πππ ππππ‘ππ Internal BUSBAR CALCULATION FACTORS π1 − πππ‘πππππ πππππ’ππ‘ππ£ππ‘π¦ ππ’ππ‘ππππ¦πππ ππππ‘ππ π1 = 1, ππ π’πππππ€π π2 − π‘πππππππ‘π’ππ ππ’ππ‘ππππ¦πππ ππππ‘ππ π2 – Heat resistance of equipment in contact with busbars (such as insulators or current transformers) must be considered when determining the temperature level that busbars can reach. In electricity switch enclosures, busbar temperature must be under 100°C. Internal BUSBAR CALCULATION FACTORS π1 − πππ‘πππππ πππππ’ππ‘ππ£ππ‘π¦ ππ’ππ‘ππππ¦πππ ππππ‘ππ π1 = 1, ππ π’πππππ€π π2 − π‘πππππππ‘π’ππ ππ’ππ‘ππππ¦πππ ππππ‘ππ π2 – Heat resistance of equipment in contact with busbars (such as insulators or current transformers) must be considered when determining the temperature level that busbars can reach. In electricity switch enclosures, busbar temperature must be under 100°C. Internal BUSBAR CALCULATION FACTORS π3 − πππ’ππ‘πππ ππππππ‘ ππ’ππ‘ππππ¦πππ ππππ‘ππ π3 = 1, ππ π£πππ‘ππππ πππ’ππ‘ Internal BUSBAR CALCULATION FACTORS π4 − ππ π πππππ¦ ππππππ‘ ππ’ππ‘ππππ¦πππ ππππ‘ππ π4 = 1, π’π ππ πππ πππππ‘πππππ‘π¦ π π€ππ‘πβ ππππππ π’πππ ππππΈ: ππ’ππ‘ππππππ ππ π’π ππ π€βππ π‘βπππ ππ ππ ππ’π‘πππ‘ ππ 2π ππ ππ’π πππ π −β π4 = π2 Internal BUSBAR CALCULATION FACTORS π4 − ππ π πππππ¦ ππππππ‘ ππ’ππ‘ππππ¦πππ ππππ‘ππ π4 = 1, π’π ππ πππ πππππ‘πππππ‘π¦ π π€ππ‘πβ ππππππ π’πππ π4 ππ π = 10ππ π4 ππ π = 5ππ Internal BUSBAR CALCULATION FACTORS π5 − πππ‘ππ‘π’ππ ππππππ‘ ππ’ππ‘ππππ¦πππ ππππ‘ππ π΄π πππ‘ππ‘π’ππ πππππππ ππ , π π ππ πππ ππππ ππ‘π¦. πΆππππππ πππππππ‘π¦ πππππππ ππ , π‘βπ’π , βπππ‘ πππππππ ππ Internal BUSBAR CALCULATION FACTORS A copper busbar with the following dimension: 80 x 10mm • Determine the busbar ampacity Internal BUSBAR CALCULATION FACTORS A copper busbar with the following dimension: 80 x 10mm • Determine the busbar ampacity if bare Given: copper busbar = 2 x 80 x 10mm Solution: π1 = 1, ππ πππ‘πππππ πππππ’ππ‘ππ£ππ‘π¦ ππππ£ππππ πΌππ’π πππ = πΌπβπππ‘ π₯π1 π₯π2 π₯π3 π₯π4 π₯π5 π2 = 1, πππππππ‘ π‘πππ ππ πΏπππΊ ππ 35β πΌππ’π πππ = 2110π₯1x1x1x1 π3 = 1, π ππππ π£πππ‘ππππ πππ’ππ‘ πΌππ’π πππ = 2110π΄ π4 = 1, ππ ππππππ π‘βππ 2π π5 = 1, ππππ£π π ππ πππ£ππ Required: busbar ampacity Internal BUSBAR CALCULATION Simpler means? Use Rule of Thumb: • Calculation 1: 2A/mm2 I = 2 xw x t I = 2A /mm2 x 80mm x 10mm I = 1600A I = 1600 x 1.8 = 2880A • Calculation 2: Icu = 1.2 x w x t Ial = 0.8 x w x t Internal BUSBAR CALCULATION FACTORS • Expansion of main busbar Length of busbars increase by expanding due to increase in temperature. This must be taken into account when busbars are supported βπ = ππ π₯ πΌ π₯ βπ‘ βπ − ππ₯πππππ πππ πππππ‘β, π ππ − ππππ‘πππ πππππ‘β, π βπ‘ − π‘πππππππ‘π’ππ ππππππππππ, πΎ πΌ − πππππππππππ‘ ππ π‘βπππππ ππ₯πππππ πππ, πππ πΎ πΌ = 0.000017/πΎ Internal BUSBAR CALCULATION FACTORS • Short Circuit Mechanical Resistance of copper busbar assemblies πΉπ − ππππππ πππ‘π€πππ ππππ ππ’π ππππ π‘βπ π πππ ππππππ‘πππ. ππππππππ‘ ππ’π₯ππππππ¦ π ππππππ‘πππ ππππ€πππ ππ ππππππππ‘ πβππ ππ ππππππ‘πππ πππππππππ π‘π ππ’πππππ‘(πβππ π ππ’π ππππ ) Internal BUSBAR CALCULATION FACTORS Calculation of force generated between main busbars √3 ππ 2 πΏπ πΉπ = π₯ π₯ππ3 π₯ 2 2π ππ πΉπ − forces generated between main busbars, N ππ − magnetic field constant, H/m ππ = 4π10−7 π»/π ππ3 −three phase symmetrical short circuit current peak value, A πΏπ −length of main busbars between to support points, m ππ −effective length between main busbars, m Internal BUSBAR CALCULATION FACTORS Calculation of force generated between auxiliary busbars ππ3 ππ πΉπ = π₯ 2π π 2 π³π π₯ ππ πΉπ − forces generated between auxiliary busbars, N ππ − magnetic field constant, H/m ππ = 4π10−7 π»/π ππ3 −three phase symmetrical short circuit current peak value, A πΏπ −largest distance between two adjacent intermediate support element used between main busbars, m ππ −effective length between main busbars, m π −number of auxiliary busbars creating the main busbar Internal BUSBAR CALCULATION FACTORS • Busbar assembly whose short circuit mechanic strength will be calculated consists of 2 pcs of busbars (with a cross-section of 100x10mm) per phase. • Distance between phase axis is 150mm • Short circuit current is unknown; however it is known that the transformer supplying the entire plant has a power of 1000kVA • Busbar assembly was supported on two lateral planes of each switch cabinets. The widest switch cabinet has a width of 600mm • Given: • Effective short circuit current: π"π3 = 25kA • Busbar = E-Cu F30 • Busbar dimension: 2 x 100 x 10 • ππ3 = n x π"π3 = 2.1 x 25kA = 52.5kA • • Lm = 600mm Ls = 600mm a = 150mm ππ = 4π10−7 π»/π πΌ = 1.1 Required: Find the force for the busbar insulator • π½ = 0.73 • π π0,2 πππ = 250π/ππ2 • π π0,2 πππ₯ = 360π/ππ2 Internal BUSBAR CALCULATION FACTORS Solution: √3 ππ √3 4π10−7 0.6 2 πΏπ πΉπ = π₯ π₯ππ3 π₯ = π₯ π₯(52.5k)2 π₯ = 1801π 2 2π ππ 2 2π 0.159 ππ3 2 π³π ππ 4π10−7 πΉπ = π₯ π₯ = π₯ 2π π ππ 2π 52.5k 2 2 π₯ π.π = 1736N ππ.πππππ−π ππ = 150 = 159ππ 0.94 1 0.42 1 = = ππ 20 47.62ππ πΉπ3 π₯ πΏπ 1801 π₯ 0.6 ππ = ππ π₯ ππ π₯ π½ π₯ = 1π₯ 1π₯ 0.73 π₯ = 29.61π₯106 π/π2 −6 8π 8 π₯ 3.33π₯10 ππ 2 0.1π₯(0.01)2 π = ππ₯ = 2π₯ 6 6 −6 3 π = 3.33π₯10 π πΉπ π₯ πΏπ 1736 π₯ 0.6 ππ = πππ π₯ πππ π₯ = 1π₯ 1π₯ = 39.22π₯106 π/π2 −6 16ππ 16 π₯ 1.66π₯10 ππ 2 0.1π₯(0.01)2 π= = 6 6 π = 1.66π₯10−6 π3 Internal BUSBAR CALCULATION FACTORS Solution: 6 ππ‘ππ‘ππ = ππ + ππ = 29.61π₯10 + 39.22π₯10 6 π 6 π = 68.83π₯10 2 ππ 68.83 π ππ2 πΉπ = ππΉ π₯ ππ π₯ πΌ π₯ πΉπ = 2.7 π₯ 1.1 π₯ 1801 = πππππ΅ ππ‘ππ‘ππ ≤ 3.7 0.8 π₯π π0,2 πππ₯ 68.83 ≤ 3.7; 0.24 0.8 π₯360 Internal BUSBAR CALCULATION FACTORS Solution: a. πΉπ = πππππ΅ , force on the support point which the busbar can resist short circuit current w/o bending b. Insulators need 5349N (535kgf) peak force in order to resist short circuit Internal BUSBAR CALCULATION FACTORS Internal EARTH OR GROUND BAR - a central point for equipment ground connections - a common point where surges flow - 50% of main busbar rating Internal INCOMING & OUTGOING DEVICES • INCOMING • ACB • MCCB • ISOLATOR • FUSE • OUTGOING • ACB • MCCB • FUSE • MCB • MOTOR CB Internal AUXILIARY CIRCUITS – used for controls or monitoring • MCB • Relay or contactor • ATS • Meter • Terminal blocks Internal HOW TO DESIGN? • SLD or customer specification • Do the BOQ • Determine the sizes & clearances of functional units • Determine the cable size, qty & route • Design the switchgear based from desired arrangement Internal HOW TO DESIGN? REQUIREMENT • SLD or customer specification • Do the BOQ TYPE • Determine the sizes & clearances of functional units • Determine the cable size, qty & route • Design the switchgear based from desired arrangement Internal HIMEL OFFER ITEM QTY REFERENCE CODE TOTAL HOW TO DESIGN? • SLD or customer specification • Do the BOQ • Determine the sizes & clearances of functional units • Determine the cable size, qty & route • Design the switchgear based from desired arrangement Internal HOW TO DESIGN? • SLD or customer specification • Do the BOQ • Determine the sizes & clearances of functional units • Determine the cable size, qty & route • Design the switchgear based from desired arrangement Internal HOW TO DESIGN? • SLD or customer specification • Do the BOQ • Determine the sizes & clearances of functional units • Determine the cable size, qty & route • Design the switchgear based from desired arrangement Internal HOW TO DESIGN? • SLD or customer specification • Do the BOQ • Determine the sizes & clearances of functional units • Determine the cable size, qty & route • Design the switchgear based from desired arrangement Internal Q&A Internal Low Voltage Switchgear: Design & Calculation By Jason Sonido – REE Internal Thank You For more information, visit us on www.himel.com Scan to contact us Internal
