Switchboard Maintenance & Calibration (Part 2)

Low Voltage Application

 Low voltage is the mean voltage nominal from 415V and 240V.
 On other hand, LV is the power supply for many electrical applications such as: 
 Street Lighting 
 Electrical Motor 
 Electrical Heater 
 Electrical Crane 
 HVAC or Chiller System(sometimes Chiller System utilize HV power supply) 

 Ultra Low Voltage is the meaning of nominal voltage at 50V, 24V, or 12V. Practically, ULV is a power supply for instrumentation equipment and confine space appliances as per Regulation from OSHA and requirements of Malaysian DOSH. 

Building Main Intake from Utility


Electrical Switching Room


What is an MSB?

MSB is Main Switchboard, the main incoming from a power supply, normally transformed by a Transformer from High Voltage to Low Voltage.
 Some industries are called MSB Power Control Centre (PCC) and Motor Control Centre (MCC).




Parts of Switchboard




Components and Functions on Switchboard


The main component inside of switchboard is: 
1) Circuit Breakers: are devices capable of making and breaking the electric circuit 
2) Protection Relay: the device to monitor, sense and trip the system when a fault current occurs. 
3) Busbars: are connected to another cubicle inside the switchboard. 
4) Power Cables: are connected incoming supply to the outgoing (load) 
5) Current Transformers: are used for reducing/stepping down alternating current from a higher value to a lower suitable value for measuring, protection and control.
6) Voltage transformer is used for stepping down voltage from a higher value to a lower suitable value for measurement, protection, and control. 
7) Capacitor Bank: these are devices for Power factor improvement.
8) Ground or Earthing bar: are the alternate paths of fault current to the true earth.

Modular Switchboard


Modular Switchboard - Feature

Each Panel has essentially three horizontal sections. 
• The bottom most is the Base Frame – a steel section that bears the weight of the switchboard. 
• It is followed by a region where the modules are stacked. 
• The topmost section consists of a busbar chamber where the busbar for power, controls, and heat supplies runs. 
• Each module is provided with a handle to close/open the module door. 
• In cases where the lower limit of handle position is violated, a Dummy Module may be inserted to raise the overall height of the handle and meet the constraint.

Modular Switchboard – Feature (CTND)

• It may not be possible to fully utilize the total available height of a panel due to various constraints while stacking the modules. In such cases, the space left shall be each moduled markets a Vacant Module. 
• Air Circuit Breakers (ACBs) are the highest-rated switchgear on LV and MV boards. 
• Cable alley is a section of the panel, where power and control cables arise (from the bottom) and each module. These alleys need not be part of every panel.

Types of Switchboard

(a) Self-contained, floor mounted, flush fronted, metal-clad cubicle type suitable for front and rear access. 
(b) Self-contained, floor mounted, flush fronted, metal-clad cubicle type suitable for front access. 
(c) Pedestal, floor mounted, metal-clad type suitable for front access. 
(d) Wall-mounted metal-clad type suitable for front access.

Switchboard

• The switchboards shall house their air circuit breakers, molded case circuit breakers, fuse switches, switch fuses, isolators, contactors, busbars, meters, protective relays, selector switches, indicating lamps, current transformers, cable terminating boxes, cable glands, anti-condensation heaters complete with automatic thermostats and isolators and all other necessary items of equipment. 
• Must be suitable for operation on a 415/240 V, 3 phase, 4 wire, 50 Hz. 
• System with solidly earthed neutral.

a) Self-Contained Floor Mounted Cubicle Switchboard – Front Access



b) Self-Contained Floor Mounted Cubicle Switchboard – Front & Rear Access

Have modules on both front and rear.

c) Pedestal Floor Mounted Switchboards


c) Pedestal Floor Mounted Switchboards (ctnd)

 The framework of the switchboard shall be fabricated from sheet steel of thickness, not less than 2.5 mm. 
 The switchboard shall be self-supporting when assembled. 
 The switchboard shall be of rigid construction and shall be designed to withstand without any sag, deformation, or warping, the loads likely to be experienced during normal operating, maintenance, or maximum fault conditions. 
 All panels shall be fabricated from sheet steel of thickness, not less than 2.0 mm. 
 Removable covers shall be provided at the front to give access to all parts for maintenance and easy removal if necessary. 
 An inspection chamber of suitable dimension shall be provided in between the busbar chamber and the main incoming switchgear for testing, inspection, and accommodating current transformers for the power correction of main incoming equipment and other monitoring and indicating equipment that may be installed at a later stage.
 The switchboard shall undergo de-rusting treatment, and antirust treatment and finished with epoxy dry powder and oven-baked semi-gloss enamel grey. 
 The switchboard shall be securely fixed onto the floor and clear from the wall.

d) Wall Mounted Switchboards


 The switchboard shall be fabricated from sheet steel thickness not less than 2.0 mm. 
 The enclosure shall be of all-welded construction with sheets bent where possible so as to minimize the number of welded joints. 
 The four sides of the enclosure shall be returned at the front to facilitate the fixing of the front cover plates. 
 The front cover plates or doors shall be of box formation and flanged to facilitate fixing to the enclosure. 
 When required by the supply authority or licensee, the portion of the front cover for mounting cut-out, meter, and residual current operated circuit breaker shall be of fiber type with thickness not less than 5 mm.

d) Wall Mounted Switchboards (ctnd)

 The front cover of the switchboard shall be provided with grommets and a dust seal to exclude dust and dirt. 
 Meshed louver or ventilation vent with filter shall be provided on both sides for ventilation. 
 All edges shall be rounded. 
 Serrated star washers shall be fitted to ensure satisfactory earthing of the front cover. 
 The switchboard shall undergo de-rusting treatment, and anti-rust treatment and be finished with epoxy dry-powder and oven-baked semi-gloss enamel grey. 
 The switchboard shall be firmly bolted to the wall or structure by means of bolts and nuts.

















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Switchboard Maintenance & Calibration (Part 1)

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