Basics of LV Switchboard-Presentation

Power Center Factory Basic of LV Switchboard (IEC-61439-2) Presented by y Eng. Nooruddin Khan 18 Dec 2013

Switchboard: Definition? 

A Switchboard is a point in an electrical network at which an incoming-power supply divides into separate circuits, each of which is controlled and protected by the fuses or switchgear of the switchboard. switchboard

Switchboard: 

A distribution switchboard is divided into a number of functional units, each comprising all the electrical and mechanical elements that contribute to the fulfillment of a given function. It represents a key li k in link i the th dependability d d bilit chain. h i

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Distribution switchboards are critical to the dependability of an electrical installation. They must comply with well-defined standards governing the design and construction of LV switchgear assemblies assemblies.

Picture: Switchboard panel with open-type knife switches is an Edison DC type. from The Frick Power House, 1904 A.D.

Switchboard Parameters: 

Rated Operational Voltage (Ue) : This is the maximum continuous voltage at which equipment may be used.

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Rated Insulation Voltage (Ui) : The highest operating voltage that will not cause a dielectric strength failure. The rated insulation voltage is used as a parameter for dielectric strength tests and for the creepage distance. The rated insulation voltage must always be higher than the rated operating voltage (Ue).

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Rated Impulse Voltage (Uimp) : The peak value of an impulse voltage of which the circuit of an assembly is capable of withstanding without failure failure.

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Rated current (In) : Maximum current that the device can carry continuously without abnormal temperature rise rise.

Switchboard Parameters: 

Rated short time withstand current (Icw) : Maximum short time withstand current that the equipment can carry without damage.

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Rated Peak withstand current (Ipk) : The rated peak withstand current of a circuit of an assembly is the value of peak current assigned to that circuit by the manufacturer which that circuit can withstand satisfactorily.

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Rated short-circuit making capacity (Icm) Maximum current (peak)) a device can make at its rated voltage (p g according g to the conditions of standard. Devices without protection like switches, must be able to withstand short-circuit current with a value & duration resulting from action of the associated protection device.

Switchboard Parameters: 

Rated ultimate short-circuit breaking capacity (Icu) : This is the maximum short-circuit current value that a circuit breaker can break att a given i voltage lt and d phase h angle l ((cos ϕ). ϕ) The Th tests t t are executed t d according to the sequence O - t - CO. O represents an automatic break operation, t a time interval and CO a make operation followed by an automatic break operation. Following the test, the circuit breaker must continue to provide a minimum level of safety ((isolation, dielectric strength). g )

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Rated service short-circuit breaking capacity (Ics) : This is the value al e expressed e pressed as a percentage of Ic Icu. It will ill be one of the following values: 25% (category A only), 50%, 75% or 100%. The circuit breaker must be capable of operating normally after breaking the Ics current several times using the sequence O-t-CO-t-CO.

LV Switchboard: Standard 

International Standard IEC-61439-1 IEC 61439 1 & 2 (Old Standard IEC-60439-1 IEC 60439 1 is still valid for KSA market till 2014). Certified switchboard is called “Verified assembly” or in old std. “Type Tested Assembly”

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American Standard ANSI-C37.20.1 or IEEE, UL-508 (Out of Power Center Scope) p )

MV Switchgear: Standard

IEC-61439-2: Verification

Switchboard: Customer Inquiry  (1)

Customer send his inquiry in different ways Single Line Diagram (Example)

Switchboard: Customer Inquiry (2)

Load Schedule (Example)

Switchboard: Customer Inquiry (3)

Main/Branch CB Size Listing (Example)

Switchboard: Customer Inquiry (4)

Drawings (Example)

Specification: 

Additional information with inquiry: Customer specification should be attached with SLD/Schedule/drawing etc.

Request For Quotation (RFQ) 

Please send all inquiry to PC with filled RFQ.

Switchboard: Main Components 

Housing (Enclosure)

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Bus-bar

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Incoming g CB/Fuse/Switch

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Outgoing CB/Fuse/Switch

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Metering & Indication

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Control & Accessories etc etc.

Housing (Enclosure)

Enclosure: Function? 

Protection of switchgear, against i t mechanical h i l iimpacts, t vibrations and other external influences (EMI, dust, moisture, vermin, etc.)

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The protection of human life against the possibility of direct and indirect electric

Enclosure: Selection Criteria 

Application: Indoor/Outdoor

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Degree g of Protection: IP Rating, g, IP-31,, IP-42 or IP-55

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Mechanical Strength (IK) Rating

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Material: Mild Steel/Stainless Steel/Polyester/GRP

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Certification: Type Tested/Universal

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Form of Separation: Form-1/2a/2b/3a/3b/4a/4b

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Entry: Top/Bottom

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Access: Front/Rear

IP Rating as per IEC-60529

IK Rating as per IEC-62262

Form of Separation:

Bus-bar 

Bus bar is a conductor of electricity e.g. strip or bar of copper, brass or aluminum that conducts electricity within a switchboard, distribution board board, substation substation, battery bank or other electrical apparatus etc.

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Cu-ETP (Electrolytic-Tough-Pitch) R240 grade of bus bar is specified in switchboard application as per EN 1650

Bus-bar Selection Criteria 

Thumb Rule: 1.5A/mm2 (Not Accurate & just for rough estimation)

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S l t suitable Select it bl size i from f tables t bl d developed l db by CDA CDA.

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Tables Developed by switchboard manufacturers

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Using Formula

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Using Software

Switchgear & CB 

A Switchgear is the combination of electrical disconnect switches, fuses or circuit breakers used to control, protect and isolate electrical equipment

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A Circuit Breaker is a manually or automatically operated electrical switch designed to protect an electrical circuit from damage caused by overload or short circuit.

Overload Protection

Short Circuit Protection

Insulation Fault Protection

Electrical Hazard

LV & MV Switchgear

Type of LV Circuit Breaker 

There are three types of LV Circuit Breakers in market

1 1.

MCB (Miniature Circuit Breaker) in two frame size upto 63A/upto 120A (Schneider Electric iC60 & iC120 range)

2 2.

MCCB (Molded Case Circuit Breaker) available normally upto 1600A (Schneider Electric MCCB NSX/Easypact range upto 630A & NS from 630A upto 3200A)

3.

ACB (Air Circuit Breaker) available upto 6300A (Schneider Electric NT range upto 1600A & NW range upto 6300A)

Selection Criteria of LV CB What are the characteristics for choosing a circuit breaker?  Current parameter: In – Icu – Ics – Icm 

Voltage parameters: Ue – Ui – Uimp

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Fixed or withdrawable

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Standard

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T Type off trip t i unitit

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Number of poles

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Need for discrimination

Metering & Indication Lamps 

Normally Metering consists of Digital multimeter or Analog Ammeters & Voltmeters 72X72 or 96X96 size with selector switch, Current transformers & control fuses/fuse holders

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Indication Lamps consist of three in Indication Lamps of 22mm diameter with Red/Yellow/Blue colors for all phases

Types of Switchboard 

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Switchboard or Main Distribution Board (Example: Blokset, Prisma Plus-P) Motor Control Center (Example: Blokset, Prisma Plus-P) Panelboard or Sub Main Distribution Board (Example: Prisma Plus P & G Plus-P Loadcenters or Final Distribution Board (Example: Prisma Pack, Disbo)

Technology in Switchboard 

Traditional distribution switchboards: Switchgear and fuse gear, etc. are normally located on a chassis at the rear of the enclosure. Required careful designing having knowledge of dimension of all components. (Example: Universal Enclosure p panels) )

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Functional distribution switchboards: Made up of functional modules d l th thatt iinclude l d switchgear it h d devices i ttogether th with ith standardized accessories for mounting & connections, ensuring a high level of reliability & a great capacity for last-minute and future changes.

Product Range        

Switchboards up-to 6300A & up-to Form-4b Panel-boards L dC Load Centers t MCC (DOL/Y-∆/VFD/Soft-starter) Auto & Manual Synchronizing Panels Auto. ATS & MTS Lighting Control Panels PFC Panels (Capacitor Bank)

Product Characteristics

Designing Tools (Software) 

E di l ffor coordination Ecodial di i study d off electrical l i l network k

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Rapsody for design Prisma Plus switchboard switchboard.

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Schneider online “Electrical Calculation Tools”

Basic Calculation

Basic Calculation

Basic Calculation

Questions

Thank You