WIRING

Electric Wire - Electrical Circuits

Electric wires are used in electrical circuits to transmit electricity
from power sources (batteries or generators) to household
appliances. They are made from conductive materials like copper or
aluminum and are insulated with rubber or plastic to prevent electric
shocks.
Properties of Electric Wire
• Conductivity: Made from copper or aluminum for efficient
electricity conduction.
• Insulation: Covered with rubber or plastic to prevent shocks
and electrical shorts.
• Flexibility: Easy to bend and shape for circuit installation.
• Durability: Suitable for various environments and long-lasting.
Types of Electric Wires
1. NM Cable (Non-Metallic Cable): Used in modern household
wiring, containing hot, neutral, and ground wires inside a plastic
sheath.
2. UF Cable (Underground Feeder): Used for wet locations and
direct burial in the ground, typically for outdoor applications.
3. THHN/THWN Wire: Thermoplastic high heat- and water-
resistant nylon-coated wire used for commercial buildings.
4. Low-Voltage Wire: Used for circuits requiring low voltage, such
as doorbells or outdoor lighting.
5. Phone and Data Wire: Low-voltage wires used for telephone
and internet connections.
 6. Coaxial Cable: Used for connecting televisions to antennas for
signal transmission.
Color Coding of Electric Wires
• Live Wire: Brown insulation
• Neutral Wire: Light blue insulation
• Earth Wire: Green-yellow insulation
Wire Sizes (AWG - American Wire Gauge)
Wire size determines the current capacity. Some examples:
• 4/0 AWG: 230 Amps (Heavy duty)
• 3/0 AWG: 200 Amps (Industrial appliances)
• 1 AWG: 130 Amps (High amp circuits)
• 12 AWG: 35 Amps (Low voltage lighting)
• 24 AWG: 3.5 Amps (Telecommunication devices)
Letter Codes on Electric Wires
• N: Copper Cable
• Y: Full insulation (PVC)
• Z: Special Wires Cable
• S: Special Wires Cable
• F: Soft Wires
• A: Cables used inside pipes
• M: Water-resistant cables
Applications of Electric Wire
• Household Wiring: Transmits electricity to appliances.
 • Commercial & Industrial: Powers machinery, equipment, and
office circuits.
• Entertainment Industry: Used for lighting, concerts, and
studios.
• Security: Used in surveillance systems and alarms.
Conclusion
Choosing the correct electric wire size is crucial for safety, preventing
voltage drops and overheating. The wire gauge should match the
circuit's power needs and length. Understanding the type of wire and
its application ensures safe and efficient electrical installations.
What is Wiring?
Wiring refers to the system of electrical conductors used to distribute
electrical power within a building or room, ensuring efficient and safe
electricity use while controlling the load.
Types of Electrical Wiring:
1. Tee System or Joint Box System:
o Used for temporary installations.
o Cheap and does not consume much cable.
2. Loop-in System:
o Appliances are connected in parallel.
o Each appliance is individually controlled and easily
accessible for fault finding.
3. Cleat Wiring:
o Wires are supported on walls and ceilings by porcelain
cleats or plastic.
o Temporary system, not ideal for domestic use.
 4. Batten Wiring:
o Uses TRS cables and is resistant to steam, chemicals, and
water.
o Cost-effective but not commonly used.
5. Casing and Capping Wiring:
o Wires are enclosed in wooden casings.
o Obsolete but easy to repair.
6. Lead Sheathed Wiring:
o Conductors are covered with a lead alloy sheath.
o Protects against corrosion, moisture, and mechanical
damage.

Conduit Wiring Classification:

7. Surface Conduit Wiring:

o Installed on the surface of roofs or walls.
o Conduits are fixed using plugs at equal distances.
8. Concealed Conduit Wiring:
o Hidden inside walls and plastered over using plastic or
metallic pipes.
o Metallic Conduit:
▪ Made of steel, strong but costly.
▪ Class A Conduit: Thin steel sheet, also known as
low gauge conduit.
▪ Class B Conduit: Thick steel sheet, also known as
high gauge conduit.
o Non-Metallic Conduit:
▪ Made of flexible materials like solid PVC.
▪ Easy to bend and install.
▪

What is a Miniature Circuit Breaker (MCB)?

A Miniature Circuit Breaker (MCB) is a small device that
automatically turns off an electrical circuit when the current flowing
through it is too high. This helps prevent damage to electrical
appliances like fans, washing machines, ovens, and fridges, or even
avoid fires caused by electrical overloads or short circuits. Unlike
fuses, MCBs can be reset after they trip, making them more
convenient and safer to use.
How Does MCB Work?
• Overload Protection: When the current exceeds the safe limit,
the bi-metallic strip inside the MCB heats up and bends,
triggering the switch to turn off the current.
• Short Circuit Protection: In case of a short circuit (when the
current rises suddenly and unexpectedly), a solenoid inside the
MCB pulls a plunger, which trips the switch and cuts off the
current.
Why is MCB Better Than a Fuse?
• MCBs can be reset once they trip, while fuses need to be
replaced after they blow.
• MCBs provide more convenience and safety, as they are easier
to operate and maintain.
Types of MCBs
1. A Type: Trips when the current exceeds 2-3 times the rated
current. Used in semiconductor manufacturing.
2. B Type: Trips when the current exceeds 3-5 times the rated
current. Used for cable protection.
3. C Type: Trips when the current exceeds 5-10 times the rated
current. Common in domestic and commercial appliances like
lights, transformers, and IT equipment (e.g., computers).
 4. D Type: Trips when the current exceeds 10-20 times the rated
current. Used for motors.
5. K Type: Can withstand 8-12 times the rated current. Used in
heavy-duty appliances like compressors and X-ray machines.
6. Z Type: Highly sensitive, used for devices that require very low
current protection.
Key Components of MCB
• Bi-metallic Strip: Bends to trip the switch during overloads.
• Solenoid and Plunger: Protects against short circuits by
triggering the trip.
• Latch Mechanism: Holds the switch in place until triggered by
overload or short circuit.
Examples of MCBs in Real Life
• Fan & Lights: Protects against electrical overloads to prevent
fire.
• Washing Machine & Oven: Trips during a short circuit,
preventing device damage or fire.
• Computers & Servers: C Type MCBs protect these appliances
from electrical faults.
Uses of MCB
• Domestic Usage: MCBs protect household devices like lights,
heaters, and fans.
• Industrial Usage: Protects heavy machinery and electrical
equipment from overloads and short circuits.
Quick Facts for Competitive Exams
1. MCB stands for Miniature Circuit Breaker.
 2. MCBs automatically turn off the circuit when there is an
overload or short circuit.
3. MCBs can be reset, unlike fuses that need replacement.
4. The bi-metallic strip in an MCB bends to protect against
overload.
5. The solenoid in the MCB is used to protect against short
circuits.
6. There are 6 types of MCBs: A Type, B Type, C Type, D Type, K
Type, and Z Type.
7. MCBs are essential for safety in both domestic and industrial
electrical systems.

Earth Leakage Circuit Breaker (ELCB) – Overview

An Earth Leakage Circuit Breaker (ELCB) is a safety device used to
protect against electric shock due to earth leakage currents. It
disconnects the electrical supply if it detects leakage current,
preventing damage to equipment or personal injury. There are two
main types: Voltage ELCB and Current ELCB (also known as RCCB or
RCD). The modern current ELCBs (RCCB/RCD) are more efficient and
widely used.

What is Earth Leakage?

Earth leakage is when electrical current unintentionally flows from
the live conductor to the earth, often due to faulty insulation or
damaged wiring. It can be dangerous as it might flow through a
person’s body, causing severe electrical shock, even potentially fatal,
if the current exceeds 30mA.
Causes of Earth Leakage
• Damaged insulation of wires or cables.
• Broken conductors that expose live wires.
• Faulty grounding of electrical equipment, allowing current to
flow through the body when touched.

What is an Earth Leakage Circuit Breaker (ELCB)?

An ELCB is a device that automatically shuts off the electrical circuit
when it detects leakage current. It is primarily designed to protect
against electrical shock but does not protect against overloads or
short circuits, so it is used alongside an MCB (Miniature Circuit
Breaker).

Function of ELCB
The main function of an ELCB is to prevent electrical shock. It
monitors leakage currents and breaks the circuit if it detects an
imbalance between the live and neutral currents.

Operation of ELCB
In normal operation, the current entering the load through the live
wire is equal to the current leaving the load through the neutral wire.
If current leaks through an unintended path, it causes an imbalance.
The ELCB detects this imbalance and cuts off the current by opening
the contacts of the switch, thus preventing shock.

Types of ELCBs
1. Voltage ELCB:
 o Working Principle: Detects the voltage difference
between the earth and the equipment body. If the
insulation fails and the live wire comes into contact with
the body, the ELCB senses this voltage difference and trips
the circuit.
o Disadvantages: It cannot detect leakage current unless it
flows through the earth connection, and it is not sensitive
enough for modern electrical systems.
o Obsolescence: Voltage ELCBs have been largely replaced
by current ELCBs (RCCBs) due to their inefficiency and
limitations.
2. Current ELCB (RCCB or RCD):
o Working Principle: Operates by detecting a current
imbalance between the live and neutral wires. If the
current in the neutral line is less than that in the live wire
(due to leakage), the RCCB trips and disconnects the
power.
o Advantages: It can detect all types of leakage currents,
providing better protection.
o Types: RCCBs are classified based on the number of poles
(e.g., 2-pole, 3-pole, 4-pole).

Types of RCCBs Based on Poles:

• 2-Pole: For single-phase systems.
• 3-Pole: For three-phase systems.
• 4-Pole: For four-wire three-phase systems.

Advantages and Disadvantages of ELCBs

Advantages:
• Prevents electrical shock by quickly disconnecting power when
leakage current is detected.
• Protects against damaged insulation and broken wiring.
Disadvantages:
• Does not protect against overloading or short circuits.
• May trip unnecessarily due to minor leakage currents in old
appliances.

Applications of ELCBs
• ELCBs are critical in areas with higher risk of electric shock, such
as wet environments (bathrooms, kitchens, etc.), or where
electrical equipment is exposed to harsh conditions.

Key Facts for Exams:

1. Voltage ELCB operates by detecting the voltage difference
between the earth and equipment.
2. Current ELCB (RCCB) works based on the current imbalance
between the live and neutral wires.
3. RCCB is a more modern and effective solution for earth leakage
protection.
4. ELCBs must be used with an MCB for full protection against
both leakage and short circuits.
5. ELCBs protect against earth leakage, but not against overload
or short circuits.
6. Types of RCCBs include 2-pole, 3-pole, and 4-pole for different
systems.
This concise explanation provides all the essential facts related to
Earth Leakage Circuit Breakers, making it easy to understand and
remember for competitive exams.

How the MCCB Operates

A MCCB (Molded Case Circuit Breaker) is designed to provide
protection and isolation in electrical systems. It combines overload
protection, short-circuit protection, and an electrical switch for
disconnection. This is achieved using a thermal element for overload
protection and a magnetic element for short-circuit protection.

Key Operations of MCCB

1. Overload Protection:
o The MCCB uses a bimetallic contact (two metals that
expand at different rates when heated). Under normal
conditions, the contact allows the current to flow. If the
current exceeds the rated limit, the metal expands,
bending the contact and triggering the trip bar, which
disconnects the power supply.
o There is a time delay built into this mechanism to allow
temporary overcurrent situations (like motor inrush
currents) without tripping the MCCB.
2. Short Circuit Protection:
o The MCCB uses an electromagnetic device (solenoid coil)
to detect short circuits. Under normal conditions, the
solenoid generates a minimal electromagnetic field. In the
event of a short circuit, the increased current flow
strengthens this field, which attracts a trip bar and opens
the contacts to disconnect the circuit instantly.
 3. Manual Disconnection Switch:
o MCCBs can also serve as manual disconnect switches
during maintenance or emergencies. When contacts
open, an arc may form. The MCCB has internal arc
quenching mechanisms to extinguish this arc safely.

MCCB Characteristics and Ratings

MCCBs are rated based on the electrical parameters that define their
capabilities. Here are some of the most important characteristics:
1. Rated Frame Current (Inm): Maximum current the MCCB can
handle. It defines the upper limit of the trip current.
2. Rated Current (In): Current value at which the MCCB will trip
due to overload. This value can be adjusted up to the rated
frame current.
3. Rated Insulation Voltage (Ui): Maximum voltage the MCCB can
withstand under laboratory conditions.
4. Rated Working Voltage (Ue): The operational voltage at which
the MCCB is rated to work.
5. Rated Impulse Withstand Voltage (Uimp): The transient
voltage the MCCB can resist during switching surges or lightning
strikes.
6. Operating Short Circuit Breaking Capacity (Ics): Maximum fault
current the MCCB can handle without being damaged.
7. Ultimate Short Circuit Breaking Capacity (Icu): The maximum
fault current the MCCB can handle before it is damaged.
8. Mechanical Life: The maximum number of manual operations
the MCCB can undergo before failure.
 9. Electrical Life: The maximum number of trips the MCCB can
perform before failure.

Sizing the MCCB

When selecting an MCCB for a circuit, consider the following:
1. Rated Working Voltage (Ue): The MCCB’s rated voltage should
match the system voltage.
2. Trip Value: The trip current should be adjusted based on the
load’s expected current.
3. Breaking Capacity: The MCCB should have a breaking capacity
greater than the potential fault currents in the circuit.

Types of MCCB
MCCBs are classified into different types based on their trip
characteristics:
1. Type B:
o Operating Current: Trips between 3 to 5 times the rated
current (In).
o Operating Time: 0.04 to 13 seconds.
o Applications: Domestic, lighting, and resistive loads.
o Surge Current: Low.
o Installation Location: Sub-feeder of Distribution Board.
2. Type C:
o Operating Current: Trips between 5 to 10 times rated
current (In).
o Operating Time: 0.04 to 5 seconds.
 o Applications: Commercial and industrial, inductive loads
(e.g., motors).
o Surge Current: Moderate.
o Installation Location: Incoming/outgoing of Distribution
Board.
3. Type D:
o Operating Current: Trips between 10 to 20 times rated
current (In).
o Operating Time: 0.04 to 3 seconds.
o Applications: Commercial and industrial, inductive-
capacitive loads (e.g., pumps, large motors).
o Surge Current: High.
o Installation Location: Incoming of Distribution
Board/Panels.
4. Type K:
o Operating Current: Trips between 8 to 12 times rated
current (In).
o Operating Time: 0.04 to 5 seconds.
o Applications: Industrial, inductive loads, and motors with
high inrush currents.
o Surge Current: High.
o Installation Location: Incoming of Distribution
Board/Panels.
5. Type Z:
o Operating Current: Trips between 2 to 3 times rated
current (In).
 o Operating Time: 0.04 to 5 seconds.
o Applications: Highly sensitive devices, such as
semiconductor equipment.
o Surge Current: Very low.
o Installation Location: Sub-feeder of Distribution Board for
IT equipment or medical devices.
Each type is designed for different application requirements based on
the expected load, surge currents, and fault tolerance needed in the
system.

Residual Current Circuit Breaker (RCCB)

A Residual Current Circuit Breaker (RCCB), also known as a Residual
Current Device (RCD), is an electrical safety device designed to
protect against electric shocks and prevent electrical fires caused by
ground faults or leakage currents. RCCBs are commonly used in
residential, commercial, and industrial electrical systems to provide
an additional layer of protection beyond regular overcurrent circuit
breakers or fuses.
Operation and Key Features
1. Detection of Ground Faults:
o RCCBs continuously monitor the electrical current flowing
in a circuit. They compare the incoming current on the live
(phase) wire with the outgoing current on the neutral
wire. Under normal circumstances, the currents entering
and leaving the RCCB should be equal, indicating a
balanced electrical circuit.
2. Imbalance Detection:
 o If there is an imbalance between the incoming and
outgoing currents, it suggests that some of the current is
leaking from the circuit, possibly due to a ground fault.
RCCBs are highly sensitive and can detect even small
leakage currents, as low as a few milliamps.
3. Tripping Mechanism:
o When the RCCB detects an imbalance beyond a preset
threshold (typically 30 mA or 300 mA, depending on the
application and safety regulations), it trips or disconnects
the circuit within a fraction of a second. This quick action
prevents the leakage current from reaching hazardous
levels, which could cause electric shock or fires.
4. Manual Reset:
o After an RCCB trips due to a ground fault, it can be
manually reset. To reset, the switch is turned to the "OFF"
position and then back to "ON". This allows power
restoration once the fault has been resolved.

Applications of RCCBs
1. Residential Electrical Panels:
o RCCBs are commonly installed in household electrical
distribution boards to protect circuits powering outlets,
lighting, and other domestic appliances.
2. Commercial Buildings:
o RCCBs are used in commercial settings to safeguard
circuits in offices, retail spaces, restaurants, and other
business environments.
3. Industrial Facilities:
 o RCCBs are employed in industrial environments to protect
circuits that power machinery, equipment, and other
industrial processes.
4. Construction Sites:
o Portable RCCBs are used at construction sites to provide
ground fault protection for temporary electrical
distribution and power tools.
5. Outdoor Electrical Installations:
o RCCBs are frequently used in outdoor electrical systems,
such as garden lighting, fountains, and other external
electrical equipment, to prevent potential electric shocks
or hazards.

RCCBs are crucial for ensuring electrical safety in various

environments by detecting and reacting to ground faults or leakage
currents quickly, providing reliable protection against electric shock
and fire risks.

MCB VS MCCB :

MCB vs MCCB

MCB MCCB

These are used for low MCCBs are used in high energy
energy requirements such as requirement applications such as
small electronic circuits or high-power equipment in industries
home wiring. or for commercial purposes.
 MCBs have ratings under 100 MCCBs goes as high as 2500 amps.
amps.

It is a low-voltage circuit It is also of low voltage to meet

breaker. IEC947 standards.

Trip characteristics cannot be Trip characteristics can be adjusted.

adjusted.

Interrupting rating under Interrupting rating ranges from 10000

18000 amps. to 200000 amps.

ELCB VS RCCB
RCCB (Residual Current Circuit ELCB (Earth Leakage Circuit
Feature
Breaker) Breaker)

RCCB stands for Residual ELCB stands for Earth

Acronym
Current Circuit Breaker Leakage Circuit Breaker

Detects leakage current by Detects leakage current

Detection
comparing the live and flowing back through the
Mechanism
neutral currents earthing wire

Detects leakage currents Only detects leakage when the

Sensitivity as low as 30mA, 100mA, current flows back via the
and 300mA earthing system
 More advanced and widely
Older technology, less
Technology used for electric shock
reliable than RCCB
prevention

Provides 100% protection Provides protection but may

Protection against electric shock due to not detect leakage
leakage currents effectively in some cases

Works efficiently with May not work efficiently

Waveform normal waveform supply, with non-standard
Efficiency and detects leakage waveforms caused by
accurately overloads

Commonly used with MCBs in Primarily used in older

Common
residential properties to installations, less
Usage
protect against leakage commonly used now

More reliable for detecting Less reliable compared to

Reliability leakage currents and RCCB, especially in modern
protecting against shocks electrical systems

Typically used in residential, More commonly found in

Application
commercial, and industrial older electrical systems or
Area
settings for safety installations