WHY IS ELECTRICAL POWER TRANSMITTED AT HIGH VOLTAGES?

 

1. Introduction

Electricity generated at power plants must travel long distances to reach industries, offices, commercial establishments, and homes. However, transmitting large amounts of electrical power over long distances presents a major engineering challenge: power losses in transmission lines due to their electrical resistance.

To reduce these losses, electrical power is transmitted at very high voltages using high-voltage transmission lines.

In India, transmission systems commonly operate at 132 kV, 220 kV, 400 kV and 765 kV. High-voltage direct current (HVDC) systems are also used for bulk power transfer over long distances.

The key principle is simple: for the same amount of power, increasing the voltage reduces the current, which significantly reduces resistive power losses.

2. Why Is Electricity Transmitted at High Voltages?

A. To reduce current

For a three-phase AC transmission system, the electrical power transferred is:

P = √3 × V_L × I_L × cosφ

Where:

·         P = active power in watts

·         V_L = line-to-line voltage in volts

·         I_L = line current in amperes

·         cosφ = power factor

For the same transmitted power and power factor, current is inversely proportional to voltage.

I_L = P / (√3 × V_L × cosφ)

Therefore, increasing transmission voltage reduces the current flowing through the conductors.

B. To reduce power losses

Every conductor has electrical resistance. When current flows through it, some electrical energy is converted into heat.

P_loss = I²R

For a balanced three-phase line, the total conductor loss is:

P_loss = 3I²R

Here, R is the resistance of one phase conductor over the line length. Since losses depend on the square of current, even a moderate reduction in current can significantly reduce energy losses.

Practical Example

Suppose a transmission line carries 100 MW of three-phase power at a power factor of 1. Compare transmission at 11 kV and 220 kV, assuming the same conductor resistance per phase.

Parameter	At 11 kV	At 220 kV
Transmitted power	100 MW	100 MW
Line current (approx.)	5,249 A	262 A
Relative resistive losses	100%	0.25%

The voltage increases by 20 times, so the current falls to one-twentieth, assuming the same power and power factor. With identical resistance per phase, resistive losses at 220 kV are 1/400 of those at 11 kV. Actual networks can have different conductor designs, voltages, and operating conditions.

This is why high-voltage transmission is essential for transporting bulk electrical power efficiently.

3. Other Advantages of High-Voltage Transmission

·         Reduced conductor size for a given current limit: lower current can allow a smaller conductor cross-section for a specified thermal limit, although actual sizing depends on mechanical strength, voltage drop, corona, and reliability requirements.

·         Improved transmission efficiency: less electrical energy is wasted as heat in the conductors.

·         Long-distance power transfer: large quantities of electricity can be transported from generating stations to major load centres.

·         Better utilization of transmission corridors: high-capacity lines can transfer more power through a given route, subject to system limits.

·         Lower current-related voltage drop: reduced current generally reduces the resistive component of voltage drop, although reactive effects remain important in AC networks.

However, high voltage also requires greater insulation clearances, more sophisticated substations, protective equipment, and additional safety precautions.

4. What Types of Conductors Are Used for Transmission Lines?

Transmission conductors must offer a suitable combination of electrical conductivity, mechanical strength, low weight, corrosion resistance, and cost effectiveness.

1. ACSR — Aluminium Conductor Steel Reinforced

ACSR is one of the most widely used overhead transmission conductors. Construction: stranded aluminium wires surround a central steel core.

Why it is used: aluminium provides electrical conductivity; the steel core provides mechanical strength; and the design offers a good balance of cost, weight, and tensile strength.

Applications: conventional overhead transmission lines, including many 132 kV, 220 kV and 400 kV networks.

2. AAAC — All Aluminium Alloy Conductor

AAAC is made entirely from stranded aluminium alloy wires. Advantages include a good strength-to-weight ratio, better corrosion resistance than many conventional ACSR designs, and no separate steel core.

Applications: overhead distribution and transmission lines where alloy strength and corrosion resistance are useful.

3. AAC — All Aluminium Conductor

AAC consists of stranded electrical-grade aluminium wires. It offers high electrical conductivity for its material, low weight, and good corrosion resistance. Its tensile strength is lower than that of many steel-reinforced conductors.

Applications: primarily distribution lines and shorter spans where mechanical strength requirements are moderate.

4. ACAR — Aluminium Conductor Alloy Reinforced

ACAR combines electrical-grade aluminium strands with aluminium-alloy reinforcing strands. It offers a useful balance of electrical conductivity and mechanical strength.

Applications: overhead transmission and distribution where the required electrical and mechanical characteristics favour this construction.

5. HTLS — High-Temperature Low-Sag Conductors

HTLS is a category of advanced conductors designed to carry higher current at elevated operating temperatures while limiting sag. Some designs use advanced aluminium alloys and composite or specially engineered cores.

Advantages include higher current-carrying capacity in suitable applications, reduced sag at higher operating temperatures compared with conventional conductors of comparable design, and the potential to increase capacity on existing transmission routes.

Applications: uprating existing transmission lines when acquiring new rights-of-way is difficult or expensive.

Note: Copper has excellent electrical conductivity, but aluminium-based conductors are generally preferred for long overhead transmission lines because they offer a favourable combination of conductivity, weight, cost, and mechanical design.

5. Why Is Aluminium Preferred Over Copper?

Although copper is more conductive per unit cross-sectional area, aluminium has a much lower density and is generally more economical for overhead transmission.

Property	Aluminium	Copper
Electrical conductivity	Lower per unit area	Higher per unit area
Density	About 2.70 g/cm³	About 8.96 g/cm³
Weight for equivalent conductor resistance	Lower	Higher
Material cost per unit mass	Generally lower	Generally higher
Typical overhead transmission use	Very common	Less common

For approximately equal DC resistance at the same length and temperature, aluminium needs around 1.6 times the cross-sectional area of copper. Nevertheless, its mass is only about half that of the copper conductor. This helps reduce the mechanical load on towers and makes aluminium an attractive material for overhead power transmission.

6. Why Are Bundled Conductors Used at 220 kV, 400 kV and 765 kV?

At extra-high voltages, one conductor per phase may produce a strong electric field at its surface. This can cause corona discharge, particularly under adverse weather conditions.

Corona can lead to:

·         Audible noise and radio interference

·         Power loss

·         Localized electrical discharge around conductor surfaces

To reduce these effects, transmission lines may use two, three, four, or more sub-conductors per phase, depending on the voltage level and design. These are called bundled conductors.

Bundling increases the effective electrical radius of each phase, reducing the surface electric-field intensity. It can also reduce line reactance and improve power-transfer characteristics. The exact bundle arrangement depends on the transmission voltage, conductor design, corona performance, and economic considerations.

7. How Does Electricity Travel from the Power Plant to Our Homes?

1.       Generating station: Electricity is generated, commonly at medium voltage.

2.       Step-up transformer: Voltage is increased for efficient bulk transmission.

3.       High-voltage transmission network: Power travels through 132 kV, 220 kV, 400 kV, 765 kV AC or HVDC systems as applicable.

4.       Receiving grid substation: Voltage is stepped down for regional distribution.

5.       Distribution transformer and consumer: Voltage is reduced to suitable utilization levels, such as 230 V single-phase supply in India.

The step-up transformer makes long-distance transmission more efficient, while receiving substations and distribution transformers progressively reduce the voltage to appropriate levels for consumers.

8. Important Engineering Considerations

·         Thermal rating: the conductor must not exceed permissible operating temperatures.

·         Sag and clearance: conductors must maintain safe clearances from the ground, buildings, vegetation, and other infrastructure.

·         Mechanical loading: wind, ice where applicable, conductor tension, and tower loading must be accounted for.

·         Insulation coordination: insulators and clearances must withstand operating voltage and expected overvoltages.

·         Corona and electric fields: conductor diameter and bundle arrangements help control electrical stress.

·         System stability and reactive power: these become particularly important for long AC transmission lines.

·         Safety: high-voltage lines require appropriate protection, earthing arrangements, and safe working distances.

Washroom Fragrances vs Electric Washroom Fragrances: An Electrical Engineer’s Guide

A pleasant-smelling washroom is important in homes, offices, hotels, shopping malls, hospitals and commercial buildings. Traditionally, washroom fragrances have been provided through manual aerosol sprays, fragrance gels, liquid fresheners and passive air fresheners.

With technological advancements, electric washroom fragrance systems have become increasingly popular. These devices use electrical power, electronic timers, sensors or controlled dispensing mechanisms to release fragrance automatically.

Types of washroom fragrance systems

1. Manual aerosol fragrance

A person presses a nozzle to release fragrance. The can uses a propellant to disperse a fine spray of fragrance into the air.

Power supply: Not required

Best suited for: Homes and low-traffic washrooms

2. Passive gel or liquid fragrance

Fragrance evaporates naturally into the air. Some models use replaceable gel blocks, scented liquids or wicking materials.

Power supply: Not required

Best suited for: Small bathrooms and low-cost applications

3. Electric automatic aerosol dispenser

A motor or solenoid-based mechanism releases fragrance at preset intervals. Electronic controls determine when the spray mechanism operates.

Power supply: Batteries or mains, depending on model

Best suited for: Offices, restaurants and commercial washrooms

4. Electric fragrance diffuser

Depending on the design, it may heat a fragrance cartridge, use a fan to circulate scented air or use an ultrasonic mechanism with a compatible fragrance formulation.

Power supply: Mains or USB, depending on model

Best suited for: Homes, hotel rooms and selected commercial spaces

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How does an electric washroom fragrance dispenser work?

An electrically operated automatic aerosol dispenser typically consists of the following components:

1. Power supply

Batteries or an approved external power supply provide the electrical energy required to operate the dispenser.

2. Electronic timer or microcontroller

It controls the interval between fragrance releases. Some models also provide day/night settings and operating modes.

3. Actuator mechanism

A small DC motor, geared mechanism or solenoid presses the aerosol valve, depending on the design.

4. Timing and control settings

The user selects the fragrance-release interval. More advanced models may use motion or occupancy sensors to control dispensing.

Traditional vs electric fragrance systems

Parameter	Traditional fragrance	Electric fragrance
Operation	Manual or natural evaporation	Automatic or electronically controlled
Electricity	Not required	Required for powered models
Initial cost	Usually low	Usually higher
Fragrance release	Depends on user action or evaporation	Timed, sensor-based or continuous, depending on model
Fragrance consumption	Varies with use and formulation	Can be controlled by settings, but may still be excessive
Maintenance	Replace spray can, gel or liquid	Replace refill and batteries; clean mechanism if required
Reliability	Mechanically simple	Depends on electronics and actuator reliability
Odour control	Depends on frequency of use and placement	More consistent fragrance dispensing is possible
Installation	Generally simple	Requires suitable mounting and, for mains-powered models, safe electrical installation
Best application	Homes and small washrooms	Busy offices, hotels and commercial washrooms

Electrical engineering: How much electricity does it consume?

One common misconception is that every electric fragrance dispenser consumes a significant amount of electricity. In reality, consumption depends on the design.

A battery-powered aerosol dispenser generally uses very little energy because its electronic controller consumes small amounts of power and its motor or solenoid operates only briefly during dispensing.

A continuously heated diffuser or fan-based unit may consume more because it operates for longer periods.

The following is an illustrative calculation, not a specification for a particular product.

Example: continuously powered diffuser

Formula: Energy (kWh) = Power (W) × Hours × Days ÷ 1,000. Excludes refill and battery costs. Actual consumption depends on the product and its duty cycle.

For a battery-operated dispenser, this continuous-load calculation is not appropriate. Its energy consumption must instead be calculated from standby current, operating current, actuation duration and number of dispensing cycles.

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Which is more economical?

The purchase price alone does not determine the most economical system. A better comparison considers the total cost of ownership.

Total annual cost = Initial cost + Fragrance refills + Batteries or electricity + Maintenance

For example, a traditional spray may have a lower initial cost, but its fragrance consumption depends on how frequently people use it. An automatic dispenser may provide more predictable dosing, although an unnecessarily short spray interval can increase refill costs.

For offices and hotels, the number of washrooms and daily footfall also matter. A slightly more expensive dispenser may be worthwhile if it reduces manual intervention and makes fragrance availability more consistent.

Advantages and disadvantages

Traditional fragrance

Advantages

·         Low initial investment

·         No electrical supply or wiring

·         Simple operation and replacement

·         No electronic or actuator failures

Disadvantages

·         Depends on manual use or natural evaporation

·         Fragrance may be inconsistent

·         Manual sprays may be forgotten during busy periods

Electric fragrance

Advantages

·         Automated and scheduled dispensing

·         Adjustable release intervals in many models

·         Less dependence on staff or user intervention

·         Some models support occupancy-based control

Disadvantages

·         Higher initial cost

·         Batteries, refills and occasional servicing are required

·         Electronic or mechanical faults can interrupt operation

·         Poor settings can waste fragrance

Safety considerations from an electrical engineer

Washrooms are often humid environments, so electrical safety is particularly important.

·         Avoid unsafe mains connections: Do not place ordinary mains-powered devices where they may be splashed or exposed to excessive moisture.

·         Choose suitable equipment: Check the manufacturer's instructions, environmental protection rating and permitted installation location.

·         Use appropriate protection: Mains installations must comply with applicable electrical safety requirements and local regulations.

·         Consider flammable aerosols: Many aerosol fragrance products contain flammable propellants. Keep them away from flames, hot surfaces and ignition sources.

·         Maintain ventilation: Fragrances mask or supplement odour management; they do not remove the underlying source of bad odours.

·         Follow refill instructions: Do not modify the dispenser or use incompatible liquids, especially in heating or ultrasonic devices.

For commercial premises, equipment selection should consider the washroom's moisture exposure, ventilation, occupancy, maintenance arrangements and manufacturer's specified operating conditions.

Where should each system be used?

Homes and small bathrooms:- Manual sprays or passive gel fragrances are usually sufficient when cost and simplicity are the main priorities.

Offices and commercial washrooms: Automatic dispensers can improve consistency and reduce dependence on staff manually spraying fragrance.

Hotels, malls and high-footfall locations: Programmable dispensers or appropriately sized fragrance systems can support scheduled maintenance and predictable operation.

Which one should you choose?

The choice between traditional and electric washroom fragrances depends on usage, operating costs and the level of automation required.

·         Choose traditional fragrance when simplicity, low initial cost and zero electricity consumption are the priorities.

·         Choose an automatic electric aerosol dispenser when controlled, scheduled fragrance release and reduced manual intervention are important.

·         Choose a powered diffuser when its particular fragrance-dispersion method suits the space and its electrical and maintenance requirements can be met.

 

Electronic Components used in Appliances

 Electronic components are the building blocks of devices such as ceiling fans, LED lights, mobile chargers, televisions, washing machines, inverters, computers and industrial control systems.

The most important distinction is that a diode controls current flow, a transistor controls or switches current, and other components store energy, limit current, filter signals or control electrical power.

1. Understand the main electronic components

1. Diode — One-way current device

Allows current to flow mainly in one direction and blocks it in the opposite direction.

• Terminals: Anode (+) and cathode (−).

• Applications: AC-to-DC rectifiers, reverse-polarity protection and LED circuits.

• Example: A charger uses diodes to convert AC into pulsating DC.

2. Transistor — Electronic switch or amplifier

A small electrical signal can control a larger current, depending on the transistor type.

• BJT terminals: Base, collector and emitter.

• MOSFET terminals: Gate, drain and source.

• Applications: Motor control, amplifiers, switching power supplies and digital electronics.

• Example: A transistor can switch an LED ON or OFF using a microcontroller.

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3. Resistor — Limits current

Opposes current flow and produces a voltage drop.

• Unit: Ohm (Ω).

• Applications: Current limiting, voltage dividers and biasing transistors.

• Example: A resistor connected in series with an LED prevents excessive current.

4. Capacitor — Stores electric-field energy

Stores charge and resists sudden changes in voltage.

• Unit: Farad (F).

• Applications: Filtering, timing, noise suppression and motor starting or running.

• Example: A capacitor in a power supply smooths rectified DC; a ceiling fan may use a capacitor to create a phase shift for its auxiliary winding.

5. Inductor — Stores magnetic-field energy

Opposes sudden changes in current.

• Unit: Henry (H).

• Applications: Filters, transformers, switching converters and motor circuits.

• Example: An inductor in a DC-DC converter helps regulate output voltage and current.

6. Rectifier — Converts AC to DC

Usually uses one or more diodes.

• Types: Half-wave, full-wave and bridge rectifiers.

• Applications: Chargers, adapters, inverters' auxiliary supplies and power electronics.

• Example: A bridge rectifier uses four diodes to rectify both halves of an AC waveform.

2. Difference between diode and transistor

This is one of the most important concepts in basic electronics.

Feature	Diode	Transistor
Main function	Controls current direction	Controls current or acts as a switch/amplifier
Typical terminals	2	3
Control input	No separate control terminal	Base or gate controls operation
Main operating modes	Forward and reverse bias	Cut-off, active and saturation for a BJT; operating regions vary for MOSFETs
Amplification	No ordinary power gain	Can provide signal or power gain
Common uses	Rectification, protection, light emission	Switching, amplification, regulation
Example	Charger rectifier	Electronic motor controller

 

How does a diode work?

A typical silicon diode has a forward voltage drop of approximately 0.6–0.8 V at suitable operating currents.

• Forward bias: Anode is at a higher potential than the cathode, allowing current to flow once sufficiently forward-biased.

• Reverse bias: Current is generally very small until breakdown, provided the diode is operated within its ratings.

For example, if a silicon diode is connected in series with a 5 V source and a resistor, approximately 0.7 V may appear across the diode, with the remaining voltage appearing across the resistor.

How does a transistor work?

Consider an NPN bipolar junction transistor (BJT).

• A small base current can control a larger collector current in its appropriate operating region.

• In cut-off, it acts approximately like an open switch.

• In saturation, it acts approximately like a closed switch.

• In the active region, it can amplify signals.

A MOSFET works differently: its gate-to-source voltage controls the channel, and its gate ideally draws almost no steady-state DC current.

Practical example: A diode can rectify an AC waveform, while a transistor can use a control signal to turn a DC motor on or off.

3. Other important semiconductor components

LED (Light Emitting Diode)

Converts electrical energy into light. It is a type of diode, not a separate category of semiconductor altogether.

Uses: Indicator lamps, displays, LED bulbs and lighting. It normally requires current limiting or a suitable driver.

Zener diode

Designed to operate in reverse breakdown within its specified limits.

Uses: Reference voltages, voltage clamping and simple regulation circuits.

Photodiode

Converts incident light into an electrical signal.

Uses: Optical sensors, light meters, remote-control receivers and communication systems.

SCR (Silicon Controlled Rectifier)

A controlled semiconductor switch with anode, cathode and gate terminals. A gate pulse turns it on; in a typical DC circuit, it remains on until current falls below its holding current.

Uses: Controlled rectifiers, power control and industrial circuits.

TRIAC

A bidirectional AC power-control device.

Uses: AC lamp dimmers, heater controllers and certain fan speed regulators. Some BLDC and induction-motor controllers use entirely different control methods.

IGBT (Insulated-Gate Bipolar Transistor)

A gate-controlled power semiconductor combining a MOS gate structure with bipolar conduction.

Uses: Variable-frequency drives, industrial inverters, traction systems and high-power converters.

IC (Integrated Circuit)

A chip containing many interconnected components, such as transistors, diodes and resistors.

Uses: Timers, amplifiers, microcontrollers, voltage regulators, logic circuits and communication systems.

4. Passive components and electrical control components

These components are just as important as semiconductors in practical circuits.

Potentiometer

An adjustable resistor, often with three terminals. It can provide a variable voltage or resistance.

Uses: Volume controls, calibration, adjustable references and some speed-control circuits.

Relay

An electrically operated switch. A coil creates a magnetic field that changes the state of its contacts.

Uses: Motor starters, control panels, automation and electrical isolation between control and load circuits.

Fuse

Opens a circuit when excessive current causes its element to melt.

Uses: Short-circuit and overcurrent protection. It must be selected for the correct current, voltage and breaking capacity.

Thermistor

A temperature-sensitive resistor. An NTC thermistor's resistance decreases as temperature increases.

Uses: Temperature sensing, motor protection and limiting inrush current.

LDR (Light Dependent Resistor)

Its resistance usually decreases as light intensity increases.

Uses: Automatic streetlights, dusk-to-dawn switches and light-sensing circuits.

Transformer

Transfers AC energy through magnetic coupling. It can change voltage and provide electrical isolation.

Uses: Power supplies, chargers, instrumentation and industrial control circuits. A conventional transformer does not operate continuously on steady DC.

5. Quick comparison of electronic components

Component	Primary function	Energy or signal behaviour
Resistor	Limits current, drops voltage	Dissipates energy as heat
Capacitor	Stores charge, filters voltage	Stores energy in an electric field
Inductor	Opposes rapid current changes	Stores energy in a magnetic field
Diode	Directs current	Rectifies or protects
Transistor	Switches or amplifies	Controls current or conduction
LED	Produces light	Converts electrical energy into light
Relay	Switches a circuit	Electromagnetic operation
Fuse	Interrupts excess current	Protective, one-time operation in typical designs
IC	Performs a circuit function	Integrates multiple electronic devices
SCR/TRIAC	Controls power	Controlled switching, especially in power circuits

6. How these components work together in a practical circuit

Consider a simplified AC-to-DC power supply used to operate electronic equipment.

AC input -230 V AC mains, where applicable

Transformer or switching converter -Provides voltage conversion where required

Diode bridge- Converts AC into pulsating DC

Capacitor and regulator- Smooths and regulates the DC supply

Electronic load- A microcontroller, sensor or other circuit

A real power supply may also include resistors, switching transistors or MOSFETs, feedback ICs, inductors, fuses and protective components. Many modern chargers use high-frequency switching converters rather than a large mains-frequency transformer.

Important safety note: A non-isolated power supply can have dangerous mains voltage present on its output circuitry. Never handle or probe mains-connected circuits without appropriate training, isolation and safety equipment.

For a deeper understanding, the most useful next step is to study how diodes, transistors, capacitors, MOSFETs and TRIACs work inside actual circuits, such as an LED driver, mobile charger, ceiling-fan regulator or BLDC fan controller.