Some common terms used in electrical services - Printable Version

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Some common terms used in electrical services - Manish Jain - 01-05-2024

Some common terms used in electrical services 

MCB: Miniature circuit breaker : It automatically switches off electrical circuit during an abnormal condition or overload of the network. Nowadays we use an MCB in low voltage electrical network instead of a fuse 

SP-MCB:A Single Pole Breaker is used with a typical 120v circuit, having one hot wire and one neutral wire. 

DP-MCB : However, a Double Pole Breaker is used with a typical 220v circuit (like for a dryer or heater) having two hot wires. If there is a short circuit to either hot wire, both poles are ganged together so both trip together 

Based on the number of poles, the breakers are classified as : 
SP –Single Pole, 
SPN – Single Pole and Neutral, 
DP – Double pole, 
TP – Triple Pole, 
TPN – Triple Pole and Neutral, 
4P – Four Pole. 

ELCB: An Earth-Leakage Circuit Breaker (ELCB) is a safety device used in electrical installations with high Earth impedance to prevent shock. It detects small stray voltages on the metal enclosures of electrical equipment, and interrupts the circuit if a dangerous voltage is detected.

RCCB  Residual current circuit breaker 

Power Factor – Power factor is defined as the cosine of angle between voltage & current in an a.c. circuit. or 
It is the ratio of Active Power (output) to Apparent Power (Input). In other words, it the ratio of power consumed by the load to the total power given to it.
It is denoted by Cos Ø. The value of power factor depends on the types of load.

Power Factor Cos Ø = Output (Active Power) in W/ Input (Apparent Power) in VA

Power Factor (pf) plays an important role in power consumption. Value of power factor depends on the type of load. Broadly there are three types of load resistive, inductive & capacitive load. Value of pf is unity on resistive load, pf is lagging on inductive load & pf is leading on capacitive load
(Note -Power factor happens in AC circuits only not in DC circuits because in DC system voltage & current don’t vary with time.)

ELECTRCIAL LOAD – Electrical Load is a device or equipment which works/operates on electrical power.

GENERALLY THERE ARE THREE TYPES OF LOAD –

1. Resistive load,
   
2. Inductive load
   
3. Capacitive load.
   

Resistive Load – When voltage is applied to a resistive load, current flows in the circuit & follows the same cycle with respect to time as voltage. In other words, there is no gap between voltage & current with respect to time. Example–Incandescent Lamps & Heaters.

Inductive Load – When voltage is applied to an inductive load, it draws a large amount of current (initially for few cycles/seconds) and then it settles down to the full load current. In this case, current reaches its peak after the voltage. Hence in this case, there is a gap between voltage & current with respect to time & this gap is called power factor. All inductive loadswork on electromagnetic field system which is responsible of lagging power factor. Examples – Induction motors, Transformers, choke, Induction Heaters, electromechanical relays etc

Capacitive Load – A capacitive load is a load in which current wave reaches its peak before the voltage & that is responsible for leading power factor.
Example – synchronous motors and capacitors.

VOLTAGE DROP – Voltage drop is defined as the amount of voltage loss that occurs through all or part of a circuit due to impedance.
(Note: –  Impedance is the property of material that opposes the flow of current in the circuit. Impedance in the circuit includes resistance, inductance & capacitance).
In other words, same supply voltage will not appear across load as voltage drop occurs in the circuit due to impedance. Impedance is the net effect of resistance, inductance & capacitance offered by circuit.

LT PANEL – LT panel is a metal enclosure fitted with ACB, MCCB, MCB, metering, relays that is used to receive 415V supply (from one or more Transformers & DG Sets) & distribute it to various loads.

FEEDER – Feeder is a section of panel which connects electrical source/power with load through cables or bus ducts.

INCOMING FEEDER– It is the section of panel where electrical power is received by ACB/MCCB/MCB from source like transformers or/and DG sets& connected with outgoing feeders such as ACB/MCCB/MCB through internal bus- bars. The capacity of Incomer feeder should always be more than all outgoing feeders of that panel.

OUTGOUNG FEEDERs– It is the section of panel where load/sub panel is connected though cables etc.

BUS-BARS – Bus-bars are made up of either Aluminum or Copper (Al or Cu). These are of rectangular in shape. Incoming & outgoing feeders are connected through these bus-bars. The capacity of bus-bar depends on the load which is to be connected with it.

CABLE ALLEY – This is the section of the panel where cables (incoming/outgoing) are connected with panel feeders.(Note – panel designing is a specialized job & should be done carefully by expert in this field).


DB (DISTRIBUTION BOARD) – Distribution board is set of MCBs, ELCBs/RCCBs which are installed in a metal box & is used to distribute electrical power to different loads.

Classification of DB according to usage –
LDB (Lighting DB) – It is used to distribute power to lighting circuits, 6A power points, exhaust fans etc. It is used for maximum 6A/10A current loads.
PDB (Power DB) – It is used to distribute electrical power /supply to power loads such as Geyser, Fridge, AC etc. All these items draw high current. MCBs of current rating 16A,20A,25A are used.
L&P DB – When DB is use for both lighting & power loads.
NDB (Normal DB) – It is used for normal AC supply where load is to be fed from normal power.
UPS DB – It is used for UPS supply where load is to be fed from UPS power.

Classification of DB according to supply (three-phase & single phase) –
3- phase DB –
A 3 Phase DB consists of one no. three phase incoming MCB and a set of single phase outgoing MCBs. A 3 phase DB can be used for Lighting & Power load.  It can be arranged in two ways –

Incomer – One TPN /4P MCB/ISOLATOR along with equal rating of ELCB /RCCB is used and outgoing– single phase MCBs – 4 nos/6 nos/8 nos/10 nos/12 nosper phase are used .  Such arrangements are called 4Way TPN DB/6Way TPN DB/8Way TPN DB/10Way TPN DB/12Way TPN DB. One no. neutral bar per phase & one no. earth link per phase are fitted in the DB for neutral &earthing wire connections of each circuit.
Incomer – One no. TPN /4P MCB/ ISOLATOR and outgoing single phase MCBs 4 nos/6 nos/8 nos/10 nos/12 nos SP MCBs per phase alongwith SP/DP ELCB per phase are used.  Such arrangements are called 4Way TPN DB/6Way TPN DB/8Way TPN DB/10Way TPN DB/12Way TPN DB. One neutral bar per phase & one earth link per phase are fitted in the DB.
Single phase DB –
A Single phase DB consists of one incoming and a set of outgoing MCBs. These can be arranged in following way –

Incomer – One DP MCB and outgoing–  4nos/6 nos/8 nos/10 nos/12 nos  SP MCBs along with SP/DP ELCB are used.


Bus Duct – Bus-ducts are sometimes used as a replacement of cables. It is used to connect Transformer and LT panel or two panels with each other. Bus-ducts are of two types – 1) Conventional type & 2) Sandwich type.

Bus-duct is made up of metal enclosure in which insulated bus bars are laid & placed with insulated support.Both ends of Bus-ducts are connected with equipment through flexible joints/plats. The purpose of flexible joints is to prevent transfer of vibrations from one end to another if bus-duct is connected with vibrating equipment like transformer.


RISING MAINS – 
Rising mains are used in high rise buildings such as residential and commercial which is installed in electrical shafts. The function of rising mains is to carry electrical supply from LT panel to the top floor of the building & provide tapping point on each floor so that power supply is available on each floor. Rising mains is metal enclosure in which electrical supply is available. Rising mains is installed in a vertical shaft. Tap boxes are mounted on Rising Mains from where electrical supply is taken by the user. Incoming end of rising mains is connected with adopter box & last end (on top floor) is covered with a metal cap. Rising mains is connected with LT panel through cables. One end of cable is connected with LT panel & other end with adopter box.


for more detail visit .... Electrical drawing of building

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