Electrical Engineering Part-4

 

Electrical Engineering

Part-4

🔷 Electrical Panel & Switchgear (LT, HT Panels, Design Basics)

🔷 Introduction

Electrical panels and switchgear are the backbone of any power distribution system. They control, protect, and distribute electrical energy safely from the source to various loads.

In residential, commercial, and industrial projects, proper panel design ensures:

Safety of equipment

Reliable operation

Ease of maintenance

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🔷 What is an Electrical Panel?

An electrical panel is an enclosure that contains electrical components such as:

Circuit breakers

Busbars

Relays

Meters

It receives power from the source and distributes it to different circuits.

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🔷 What is Switchgear?

Switchgear refers to a combination of devices used for:

Switching

Controlling

Protecting electrical equipment

It includes:

Circuit breakers

Isolators

Fuses

Protective relays

👉 Switchgear ensures fault isolation and system safety.

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🔷 Types of Electrical Panels

1. LT Panel (Low Tension Panel)

Voltage level: Up to 1 kV
Used in buildings and industries

Common LT Panels:

Main LT Panel

PCC (Power Control Center)
MCC (Motor Control Center)
APFC Panel
Distribution Board

👉 Used for final power distribution

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2. HT Panel (High Tension Panel)

Voltage level: Above 1 kV (typically 11 kV / 33 kV)
Used in substations and large industries

Common HT Panels:

Incoming Panel
Outgoing Feeder Panel
Bus Coupler Panel

👉 Used for bulk power handling

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🔷 Main Components of Electrical Panel

1. Circuit Breaker

Protects system from:

Overload

Short circuit

Types:

MCB

MCCB

ACB

VCB

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2. Busbar

Conducts power inside panel
Made of copper or aluminium

👉 Must be properly sized for current capacity

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3. Protective Relay

Detects fault conditions
Sends trip signal to breaker

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4. Metering Devices

Voltmeter
Ammeter
Energy meter

👉 Used for monitoring

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5. Contactors & Starters

Used for motor control
Provides automatic switching

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🔷 Basic Panel Layout (SLD Concept)

Incoming Supply
       |
   Circuit Breaker
       |
     Busbar
   /   |    \
Feeder Feeder Feeder
  |      |      |
Load   Motor  DB

👉 You prefer SLD (Single Line Diagram) — this is the basic concept used in all projects.

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🔷 Switchgear Classification

Based on Voltage:

LT Switchgear
HT Switchgear

Based on Installation:

Indoor Switchgear
Outdoor Switchgear

Based on Insulation:

Air Insulated (AIS)
Gas Insulated (GIS)

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🔷 Important Design Considerations

1. Load Calculation

Calculate total connected load
Apply diversity factor

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2. Short Circuit Capacity

Panel must withstand fault current

👉 Very important for safety

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3. Busbar Sizing

Based on current rating
Temperature rise limits

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4. Protection Coordination

Proper relay and breaker setting
Selective tripping

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5. Ventilation

Avoid overheating
Provide proper airflow

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6. IP Protection

IP42 / IP54 / IP65 as per location

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7. Earthing

Proper earthing of panel body
Safety against leakage current

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🔷 Types of Circuit Breakers (Brief)

Type	Application
MCB	Small loads
MCCB	Medium loads
ACB	Main LT panels
VCB	HT panels

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🔷 Safety Features

✔ Interlocking system
✔ Emergency stop
✔ Danger labels
✔ Earth bus connection
✔ Insulated busbars

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🔷 Common Site Issues

❌ Loose connections
❌ Overheating
❌ Improper cable termination
❌ Dust accumulation
❌ Wrong protection setting

👉 Regular inspection is mandatory

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🔷 Practical Tips for Site Engineers

Since you are working in construction & electrical execution, focus on:

✔ Check panel rating vs load
✔ Verify cable size & termination
✔ Ensure proper earthing
✔ Test breakers before energization
✔ Maintain panel clearance space
✔ Follow safety procedures

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🔷 Conclusion

Electrical panels and switchgear play a critical role in safe and efficient power distribution. Proper design, installation, and maintenance ensure system reliability and prevent electrical hazards.

🔷Substation & Electrical Distribution System

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🔷 Introduction

Electric power generated at power plants is transmitted over long distances and finally distributed to consumers through substations and distribution systems.

A substation plays a vital role in controlling, protecting, and distributing electrical power safely and efficiently.

For site engineers, understanding substations is essential for execution, testing, and maintenance of electrical systems.

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🔷 What is a Substation?

A substation is a facility where electrical power is transformed from one voltage level to another and distributed to different feeders.

👉 Main functions:

Voltage transformation

Switching and control

Protection of equipment

Distribution of power

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🔷 Types of Substations

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🔸 1. Step-Up Substation

Located near power plant

Increases voltage for transmission

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🔸 2. Step-Down Substation

Reduces voltage for distribution

👉 Example:

33kV to 11kV

11kV to 415V

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🔸 3. Distribution Substation

Supplies power to consumers

Located near load centers

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🔸 4. Indoor Substation

Installed inside buildings

Used in commercial complexes

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🔸 5. Outdoor Substation

Installed in open area

Used for high voltage systems

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🔷 Main Components of Substation

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🔸 1. Transformer

Converts voltage level

Main equipment

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🔸 2. Circuit Breaker

Protects system from faults

Trips automatically

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🔸 3. Isolator

Used for maintenance

Operates without load

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🔸 4. Busbar

Common conductor

Distributes power

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🔸 5. Lightning Arrester

Protects from lightning surges

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🔸 6. CT & PT

Used for measurement and protection

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🔸 7. Earthing System

Ensures safety

Provides fault current path

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🔷 Single Line Diagram (SLD)

SLD is a simplified representation of electrical system using single lines.

👉 Shows:

Transformer

Circuit breakers

Load connections

✔ Very important for site engineers

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🔷 Electrical Distribution System

Distribution system delivers power from substation to end users.

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🔸 Types of Distribution

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1. Primary Distribution

High voltage (11kV, 33kV)

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2. Secondary Distribution

Low voltage (415V, 230V)

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🔷 Types of Distribution Systems

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🔸 1. Radial System

Simple system

Single path for supply

❌ Less reliable

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🔸 2. Ring Main System

Supply from two sides

✔ More reliable

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🔸 3. Interconnected System

Multiple sources

✔ Highly reliable

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🔷 Voltage Levels in India

👉 Common levels:

Generation → 11kV

Transmission → 132kV / 220kV / 400kV

Distribution → 11kV

Utilization → 415V / 230V

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🔷 Substation Layout

A typical substation includes:

✔ Incoming line
✔ Transformer
✔ Switchgear panel
✔ Control room
✔ Earthing grid

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🔷 Protection in Substation

Protection devices include:

✔ Circuit breakers
✔ Relays
✔ Lightning arresters

👉 Protect against:

Overload

Short circuit

Earth fault

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🔷 Earthing in Substation

Proper earthing is critical.

👉 Types:

Equipment earthing

Neutral earthing

✔ Ensures safety and fault clearing

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🔷 Maintenance of Substation

✔ Regular inspection
✔ Check oil level in transformer
✔ Tightening of connections
✔ Cleaning of panels

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🔷 Safety Precautions

✔ Use PPE
✔ Isolate supply before work
✔ Follow lockout-tagout system
✔ Maintain safe distance

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🔷 Practical Site Tips

✔ Always follow SLD
✔ Label all equipment
✔ Maintain proper clearance
✔ Ensure proper ventilation
✔ Check earthing resistance

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🔷 Common Mistakes

❌ Improper earthing
❌ Overloading transformer
❌ Poor maintenance
❌ Wrong cable connections

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🔷 Conclusion

Substations and distribution systems are the backbone of electrical supply. A well-designed system ensures reliable, efficient, and safe power distribution.

Understanding these systems helps engineers manage large projects effectively and avoid failures.