Electrical Knowledge In Detail's

 

Electrical Knowledge

Electrical Engineering Fundamentals:

Understanding Ohm's Law, voltage, current, resistance, and basic circuit concepts is essential

What is electricity:

Electricity is the set of physical phenomena associated with the presence and motion of matter possessing an electric charge. Electricity is related to magnetism, both being part of the phenomenon of electromagnetism, as described by Maxwell’s equation. Common phenomena are related to electricity, including lightning, static electricity, electric heating, electric discharge and many others.

Circuit Analysis:

Circuit analysis is the process of determining the electrical behavior of a circuit, including voltage, current and power within the circuit. It involves using mathematical equations and tools to understand how different circuit elements (Resistor, Capacitor, Inductor, Voltage and Current Source) interact to produce the desired element properties.

Current:

In the certain time, The amount of electrons or charge flow in a conductor is called current. Its symbol I and its Unit Ampere which short A and its measure in Series.

      Current Always Flow Negative to Positive.

[ When one coulomb charge flow in a conductor or wire in one second, its called one coulomb.]

Specifically, 1 C = 1 A ⋅ s. It also represents the charge of approximately 6.241509 × 10^18 elementary charges (e.g., the number of electrons or protons). 

Type of Current:

1.       AC (Alternating Current)

2.       DC (Direct Current)

without 2 type current one more current present that is EDDY CURRENT, which produce from coper wire coil. Ex: Motor, Transformer etc.

AC (Alternating Current): Where the flow of electrons or charge Changes their direction across the time, its called Alternating Current.

DC (Direct Current): Where the flow of electrons or charge can’t Changes their direction across the time, its called Direct Current.    

Voltage:

Voltage is one kind of / a type of electric pressure, which changes the place of free electrons in a conductor is called voltage. Its symbol  V  and its Unit Volt which short v and its measure in Parallel.

Whatis the Difference Between Current and Voltage?

Current	Voltage
At the certain time, The amount of electrons or charge flow in a conductor is called current.	Voltage is one kind of / a type of electric pressure, which changes the place of free electrons in a conductor is called voltage.
Current is the flow of electron.	Voltage is one kind of / a type of electric pressure.
Its symbol  I .	Its symbol  V .
its Unit Ampere which short A.	its Unit Volt which short v.
its measure in Series.	its measure in Parallel.

 

Resistor:

A resistor is a device that resists the flow of electric current in a conductor.

Resistance is the measure of how much a conductor opposes the passage of electric current. Its symbol  R  and its Unit is  Ω .

Resistor is 2 Types:

1.       Fixed Resistor

2.       Variable Resistor

Capacitor:

A capacitor is a device that stores electrical energy by accumulating electric charges on two closely spaced surfaces that are insulated from each other.

Capacitance is the ability of an object to store electric charge. It is measured by the change in charge in response to a difference in electric potential.

Its symbol  Q and its Unit is  µF .

 

Inductor:

An inductor is a passive electronic component, also known as a coil, choke, or reactor, that stores energy in a magnetic field when current flows through it. It's primarily used to store energy or to create a magnetic field.

Inductance is the tendency of an electrical conductor to oppose a change in the electric current flowing through it. The electric current produces a magnetic field around the conductor. The magnetic field strength depends on the magnitude of the electric current, and therefore follows any changes in the magnitude of the current.

Its symbol  L and its Unit is  Henry(H) .

 

Circuit:

An electric circuit allows electrical current to flow in a closed path to provide power and control various electrical and electronic devices as loads. The circuit components work together to allow the flow of current at specific voltages, currents and resistance.

Type of Circuit: There are different types of circuits like: series, parallel, series-parallel, star-delta, linear, non-linear, unilateral, bilateral, closed, open, DC and AC. 

1. Series Circuit: In a series circuit, components are connected end-to-end, creating a single path for current flow. If one component fails, the entire circuit is disrupted. 

                                                              

 

2. Parallel Circuit: In a parallel circuit, components are connected across multiple paths. Current can flow through different branches, so if one branch fails, others can still function. 

3. Series-Parallel Circuit: This type combines elements of both series and parallel connections. 

4. Open Circuit: An open circuit has a break in the path, preventing current flow. 

5. Closed Circuit: A closed circuit has a complete path, allowing current to flow. 

6. Short Circuit: A short circuit provides an unintended, low-resistance path for current, often causing excessive current flow. 

7. DC Circuit: A DC circuit uses direct current, where the current flows in one direction. 

8. AC Circuit: An AC circuit uses alternating current, where the current reverses direction periodically. 

 

Ohm’sLaw:

At constant temperature, The current flowing through a conductor is directly proportional to the potential difference in volts across the two ends of the given conductor and inversely proportional to the resistance (R) in ohms (Ω) between the ends of the same conductor  [   V=IR   or   I=V/R   or   R=V/I  ] .

Kirchhoff’sLaw:

Kirchhoff's Laws quantify how current flows through a circuit and how voltage varies around a loop in a circuit. Kirchhoff’s Laws are two fundamental laws that Kirchhoff’s Current Law (KCL) and Kirchhoff’s Voltage Law (KVL).

Kirchhoff’s Current Law (KCL): states that the total current entering a junction in a circuit is equal to the total current leaving that junction.

Kirchhoff’s Voltage Law (KVL): states that the total voltage around any closed loop in a circuit is zero.

Jule’s Law:

Jule’s 1^st Law: The amount of heat generated per second in a wire carrying a current is proportional to the electrical resistance of the wire and the square of the current. He calculated that the heat emitted every second equals the absorbed electric power, also known as power loss.

Joule’s law of heating equation:

The heat produced by the current flow in an electric wire is measured in Joules.

The Joule’s law of heating expression is as follows:

Q=I²Rt

Where, Q denotes the amount of heat, I the amount of electric current, R the amount of electric resistance in the conductor, and t is the amount of time.

Jule’s 2^nd Law: The internal energy of an ideal gas is independent of its volume and pressure and only depends on its temperature.

αT = 1 for an ideal gas defined by appropriate microscopic postulates, implying that the temperature change of such an ideal gas during a Joule–Thomson expansion is zero. 

According to this theoretical result, for such an ideal gas:

The internal energy of a perfect gas is solely determined by its temperature (not pressure or volume).

In his experiments, Joule discovered this rule for real gases, which is known as Joule’s second law.

Faraday’sLaw:

Faraday's first law of electromagnetic induction states that a changing magnetic field induces an electromotive force (EMF) in a nearby conductor.

 

Faraday's second law of electromagnetic induction states that the magnitude of the electromotive force (EMF) induced in a circuit is directly proportional to the rate of change of magnetic flux through the circuit.

Ꜫ= -ꓠ ∆ᶲ⁄∆ᵼ

Where ε is the electromotive force, Φ is the magnetic flux, and N is the number of turns.

Power Generation System:

A power generation system is a system designed to produce electricity from various energy sources. These systems typically involve a combination of components that convert a primary energy source into mechanical energy, then into electrical energy. The primary energy source could be heat, water, wind, or solar radiation. 

Components of a Power Generation System:

Primary Energy Source:

This is the initial source of energy, such as fossil fuels, nuclear materials, water flow, wind, or sunlight.

Conversion System:

This component transforms the primary energy into mechanical energy, often using turbines or other mechanisms.

Generator:

The generator converts the mechanical energy into electrical energy.

Power System:

The generated electricity is then distributed through a power system, which includes transmission and distribution networks to deliver power to consumers.

Types of Power Generation Systems:

Thermal Power Plants:

These plants use the heat generated by burning fossil fuels (coal, gas, oil) or nuclear fission to produce steam, which drives turbines and generators.

Hydroelectric Power Plants:

These plants utilize the potential energy of water, often from dams, to drive turbines and generators.

Wind Power Systems:

These systems use wind turbines to convert the kinetic energy of wind into mechanical energy, which is then converted to electricity by a generator.

Solar Power Systems:

These systems use solar panels (photovoltaic cells) to convert sunlight directly into electricity.

Other Power Generation Methods: This includes geothermal power, nuclear power, and fuel cells.

Power Generation System Overview:

 

Power Generation, Transmission, Distribution System:

Power generation, transmission, and distribution refer to the three key stages of providing electricity to consumers. Power generation is the process of produce electricity from various energy sources, transmission is the process of moving that electricity over long distances at high voltages, and distribution is the process of converting the high-voltage electricity to lower voltages which suitable for individual home and business. 

Power Generation: This involves converting energy sources like coal, gas, nuclear, or renewable resources (solar, wind, hydro) into electrical energy. Power plants are the facilities where this conversion takes place, and the generated electricity is typically at a high voltage. 

Transmission: Once electricity is generated, it needs to be transported over long distances to reach consumers. This is done using high-voltage transmission lines, which form a network of power lines connecting power plants to substations. 

Distribution: The electricity then needs to be delivered to individual homes and businesses. This is achieved through lower-voltage distribution lines and transformers, which step down the voltage to levels suitable for consumer use. 

Substation:

Substation is a part of the Electrical generation, transmission, and distribution system. We can turn voltage from high to low or low to high and do various important works with the help of a substation.

The substation is situated between power plant and customers. Where various electrical devices and numbers of feeders are used for transforming Electricity into voltage with different values, with the help of a transformer. Also, power factor, frequency, and AC turn into DC with the help of a substation

Things we should keep in mind while designing Electrical substations:

• First, we have to select a suitable place.
• Ensure the security- Proper maintenance, changing defective devices, regular inspection and examining by standard, security from fire-related accidents and other matters should be considered.
• It has to be easily manageable, and maintained and should be of minimum cost.

Types of substation :

We can divide substations into different types. Here we will show the types based on two factors:

• Service
• Structural characteristics

[Substations are classified based on their voltage levels, such as grid substations (which receive power from generation stations) and distribution substations (which deliver power to end-users).]

Service: It is mainly based on voltage level up down, improving power factor, turning AC power into DC power, etc. 

• Transformer substation: For controlling up down of voltage.
• Switching substation: For switching the line. 
• Power factor correction substation: For improving power factor.
• Converting substation: For turning AC into DC.
• Industrial substation: For supplying power in different industries. 
• Frequency substation.

Structural Characteristics:

• Indoor substation: If the devices and equipment used in the substation are placed in a shade or building, then it is an indoor substation. Its voltage is a maximum of 11 kV.
• Outdoor substation: If the devices and equipment are placed in an open place, then it is an outdoor substation. They are mainly higher than 66 kV.
• Underground substation: This type of substation is situated in the underground of populated places.
• Paul mounted substation: It is a type of outdoor substation which is situated between the H-pole and 4 poles.

The above-mentioned substation can be divided into different types :

• Step-up substation
• Primary substation
• Secondary substation
• Distribution substation

The view of substation element:

Generating Station>>Substation>>Distribution

1. Primary power lines side

       2. Secondary power lines side

Primary Power lines side:

1. Primary power lines
2. Ground wire
3. Overhead lines
4. Lightning arrester
5. Disconnect switch
6. Circuit breaker
7. Current transformer
8. Transformer for measurement of electric voltage
9. Main transformer
10. Control building
11. Security fence
12. Secondary Power line

The components we need for a substation:

Incoming Circuit:

• Lightning Arrestor.
• Overhead earth wire.
• Isolator
• Fuses
• Earthling Switch etc
• Incoming Lines (Underground & Overhead)

High Voltage Switchgear Panel: (HT):

• Bus Bars
• Isolators
• Circuit Breaker
• C.T
• P.T
• Metering System
• Indicating Instruments
• Various Protective Relays

Low Voltage Switchgear Panel: (LT):

• Bus bars
• Isolators
• Fuses
• Magnetic contractors
• Air-break switch
• Various types of no-fuse breaker

Electrical Knowledge

• Metering system
• Indicating instruments
• Various protective relays etc
• PFI capacitors

Some other common components:

• Transformer
• The battery bank and charging system
• Outgoing line
• Emergency power supply system
• Also, some other components are needed based on the types of substations.

 

Transformer:

A transformer is a stationary electrical device that transfers electrical energy from one circuit to another without changing the frequency.

How Does a Transformer Work and Why Is It Used:

How it Works: A transformer primarily operates based on mutual induction. Now, you might wonder what mutual induction is.

“When a current change in one circuit induces an electromotive force (EMF) in another circuit that is magnetically linked, this process is called mutual induction.”

When an electrical supply is given to the primary coil, a magnetic field is generated around it, which is then collected by the secondary coil.

This creates mutual induction between the primary and secondary coils, causing electricity to flow in the secondary coil.

In other words, A transformer has no moving parts, meaning it is a completely stationary device. Its construction is very simple, such as two or more insulated copper wires wound around an insulated steel or iron core (laminated steel/Iron core).

We know that a transformer has two windings, primary and secondary. When voltage is applied to the primary winding, a magnetic field is created, and the magnetic flux passes through the iron core to the secondary winding, creating a magnetic field there as well.

As a result, voltage is induced in the secondary coil. The amount of electricity flowing in the secondary side compared to the primary side depends on the number of turns in the primary and secondary coils, which is known as the transformation ratio.

Why It Is Used: Transformers are generally used to step up or step down voltage. For example, consider a substation with a voltage of 11 kV, but the consumer level requires 400/220 volts.

In this case, a transformer is used to step down the 11kV voltage to 400/220 volts.

Different Parts of a Transformer:

A transformer mainly consists of two parts:

1. Primary Coil: The side of the transformer where power supply is provided is called the primary coil.
2. Secondary Coil: The side of the transformer where the output is collected is called the secondary side.

In addition, a three-phase transformer has other parts, which are discussed below:

1. Core: The steel frame around which the windings are wrapped is called the core. Using a steel core allows the magnetic flux generated on the primary side to easily link with the secondary.
2. Winding: A transformer’s winding can have two or more coils. These coils are usually made with super enamel copper wire.
3. Insulation: To insulate the core from the coil, non-conductive paper (insulating paper) is used on the core. The coil itself is insulated between the turns with a super enamel coating.
4. Tank: The tank of a transformer contains oil in which the windings and core are immersed. The tank is sealed with a weatherproof gasket. The core is fixed to the bottom of the tank.
5. Transformer Oil: The oil used inside the tank is called transformer oil. It is primarily used for insulation and to keep the windings cool.
6. Conservator: The volume of the transformer oil changes with its temperature. A drum is used on top of the tank to accommodate these changes. This drum is called the conservator.

7. Breather: As the volume of transformer oil changes, air enters and exits the tank. To keep this air dry and free of moisture, a glass container is used, called a breather.
8. Bushing: The transformer windings’ terminals are brought outside the tank through bushings. The primary coil is connected to the AC source, and the secondary coil is connected to the load via these bushings.
9. Earth Point: To protect the transformer from various hazards, it has two earth points. These earth points are connected to the ground.

Types of Transformers:

Based on Operation:

• Step-Up Transformer: A transformer that provides a higher output voltage compared to the input voltage is called a step-up transformer. Example: Step-up transformers are used in IPS, UPS, etc.
• Step-Down Transformer: A transformer that provides a lower output voltage compared to the input voltage is called a step-down transformer. Example: Step-down transformers are used in household electronic devices, such as televisions, DVD players, charger lights, etc.

Based on Usage:

• Power Transformer: This type of transformer changes both current and voltage at the output. Typically, this type of transformer steps up or steps down AC at the input. Examples: Auto-transformers, toroidal transformers, variable transformers, etc.
• Distribution Transformer: Distribution transformers, or service transformers, are used to distribute power to consumers. Voltage is stepped down according to demand and distributed at the consumer level.
• Auto Transformer: An auto-transformer is a type of transformer with only one winding, part of which is shared between the primary and secondary coils, making them electrically and magnetically connected.
• Instrument Transformer: An instrument transformer is a highly accurate electrical device used to change the level of voltage and current separately.

Instrument transformers can be further categorized into:

• Current Transformer (CT): This transformer reduces high current to a lower range for measurement using low-range meters.
• Potential Transformer (PT): This transformer reduces high voltage to a lower range for measurement using low-range meters.

Based on Frequency:

• Audio Frequency Transformer: Audio frequency transformers are typically used in audio amplifier circuits ranging from 20Hz to 20,000Hz.
• Radio Frequency Transformer: These transformers are used to transfer radio frequency energy from one circuit to another.

Based on Number of Phases:

• Single-Phase Transformer
• Polyphase Transformer

Based on Installation:

• Indoor Type Transformer
• Outdoor Type Transformer
• Underground Transformer
• Pole Mounted Transformer

Transformer Losses:

• Iron or Core Losses
• Copper or Resistance Losses
• Stray Losses
• Dielectric Losses

Iron or copper losses can be further categorized into:

• Eddy Current Losses
• Hysteresis Losses 

Transformer Efficiency:

Transformer efficiency refers to the ratio of output power to input power. There is no machine in the world with 100% efficiency, but transformers can achieve efficiency ranging from 90% to 99% of the input power.

Therefore, it can be understood that transformers have the highest efficiency with minimal power loss:

Where,

• V₂ – Secondary terminal voltage
• I₂ – Full load secondary current
• Cosϕ₂ – Power factor of the load
• P_i – Iron losses = Hysteresis losses + Eddy current losses
• Pc – Full load copper losses = I₂²R_es

Why is Transformer Rated in KVA, not in KW?

Copper losses ( I²R) depends on Current which passing through transformer winding while Iron Losses or Core Losses or Insulation Losses depends on Voltage. So the Cu Losses depend on the rated current of the load so the load type will determine the power factor, that is why the rating of Transformer in kVA, and not in kW.

Switchgear:

Switchgear is a variety of equipment, That switches, controls and protects the electrical system. Switching devices include Relay, Circuit Breaker, Magnetic Contactors, etc.

The primary functions of switchgear are to protect, control, and regulate the flow of electrical power. 

Type of Switchgear: There are three primary types of switchgear: Low Voltage (less than 1 kV), Medium Voltage (up to 36 kV), and High Voltage (above 36kV).

Low Voltage Switchgear:

Also called LV switchgear in short, low voltage switchgear is designed for systems that carry less than 1000 volts of electricity. Mostly built in the form of metal enclosed structures, this switchgear typically comprises these separate parts: breaker, bus, and cable compartments.

Individual breakers are housed in their own compartments, while solid barriers protect the bus compartment from the others. The cable compartment on the other hand, is accessed from the rear, although some also use front access.

Low voltage switchgear is designed with a broad range of capabilities including arc resistant and arc quenching capacities. Typically, this type of switchgear uses 30-cycle withstand current breakers. This means the breakers can tolerate 30 cycles of fault current without tripping or getting damaged.

LV Switchgear Application:

As its name suggests, low voltage switchgear is meant for low voltage power systems- or electrical networks that carry less than 1 kV. As such, you‘ll find it extensively used in residential and commercial applications such as schools, hospitals, office buildings, and homes.

Low voltage switchgear is usually installed on the secondary side of transformers. Here, it ensures the safe distribution of power into residential buildings or industrial facilities. Other applications include coupling with MCCs to control motor systems, also called motor control center switchgear.

Medium Voltage Switchgear:

Unlike low voltage switchgear, which is intended for use in lower voltage applications, medium voltage switchgear is rated for higher voltages of up to 36 kV. MV switchgear must withstand greater electrical distress, since it carries more voltage and current.

The switchgear is, therefore, available in a variety of insulation and designs including: mineral oil, sulfur hexafluoride (SF6), and other variations such as metal clad, metal enclosed, pad mount, vault, and submersible types.

Depending on the arc flash rating, this type of switchgear is further classified into type 1, 2, 2B, and type 2C switchgear. Type1 switchgear only has arc resistant devices in the front, while type2 has the entire assembly arc resistant. Type 2B switchgear must be arc resistant all around, type C switchgear between compartments as well as all around.

MV Switchgear Application:

MV switchgear is often found on both the primary and secondary side of power. That means application in power generation plants as well as in electricity distribution systems. Most of the time, medium voltage switchgear is used in utility plants such as hydroelectric and solar.

Other MV switchgear applications include controlling power distribution in heavy industrial facilities such as oil and gas, mining, and the railway industry. In these situations, different classes of the switchgear, such as metal enclosed and metal clad medium voltage switchgear are used.

High Voltage Switchgear:

Switchgear for 36 kV systems and above is known as high voltage or high tension switchgear. Because it handles higher levels of electricity, HV switchgear is prone to arc flashes and must use technologies to prevent or quench it.

High voltage switchgear is classified as 2 major types: air and gas insulated. Air insulated switchgear in the high voltage category is normally composed of large equipment and used outdoors. On the other hand, high voltage, gas insulated switchgear is typically an indoor equipment.

HV switchgear may use oil or oil-less breakers. Oil switchgear usually has mineral oil as an insulation medium. Oil-less breakers in these types of switchgear relies on other mediums for insulation, such as air, SF6, and even vacuum.

HV Switchgear Application:

Generally, this type of equipment is employed in applications that involve power sources and power distribution networks. So you will mostly find HV switchgear in power plants, transmission lines, and other utility circuits where it’s used to monitor systems, isolate circuits in the event of faults and other functions.

Transmission lines convey electricity from generating plants to either to cities or neighboring countries. These require the use of high voltage switchgear consisting of switching and protection devices. The equipment includes isolators and reclosers that automatically break and re-establish connections when a fault is detected.

Which Type Of Circuit Breaker Is Use to LT & HT Switchgear:

In Low Tension (LT) switchgear, Air Circuit Breakers (ACBs), Molded Case Circuit Breakers (MCCBs), and Miniature Circuit Breakers (MCBs) are commonly used.

 High Tension (HT) switchgear typically employs Vacuum Circuit Breakers (VCBs) and Minimum Oil Circuit Breakers (MOCBs).

LT Switchgear:

• Air Circuit Breakers (ACBs): These are used for larger currents and higher capacities, such as in industrial applications. 

• Molded Case Circuit Breakers (MCCBs): They offer a broader range of current ratings and are suitable for various applications. 

• Miniature Circuit Breakers (MCBs): These are commonly used for residential and smaller commercial applications, offering protection against overcurrent and short circuits. 

HT Switchgear:

• Vacuum Circuit Breakers (VCBs): VCBs are favored for high-voltage applications due to their excellent arc-quenching capabilities and compact design. 

• Minimum Oil Circuit Breakers (MOCBs): MOCBs use oil to extinguish the arc, providing reliable protection for high-voltage systems. 

What is Circuit Breaker:

A circuit breaker is an automatic electrical switch designed to protect a circuit from damage caused by excessive current, such as from an overload or short circuit. It essentially interrupts the flow of current when a fault is detected, preventing potential damage to electrical equipment and components.

Here's a more detailed breakdown:

1. By Voltage:

• Low-voltage circuit breakers: Designed for electrical circuits with a voltage of 1000V or less. 
• Medium-voltage circuit breakers: Designed for electrical circuits with a voltage between 1000V and 20,000V. 
• High-voltage circuit breakers: Designed for electrical circuits with a voltage of 20,000V or more. 

2. By Circuit Type:

• AC (Alternating Current) circuit breakers: Designed for AC circuits.
• DC (Direct Current) circuit breakers: Designed for DC circuits. 

3. By Arc Extinguishing Medium:

• Oil circuit breakers: Use oil to quench the arc.
• Air circuit breakers: Use air to extinguish the arc.
• Vacuum circuit breakers: Utilize a vacuum to extinguish the arc.
• SF6 circuit breakers: Use sulfur hexafluoride gas to extinguish the arc. 

4. By Functionality:

• Standard circuit breakers: Basic circuit breakers that protect against overloads and short circuits.
• GFCI (Ground Fault Circuit Interrupter) circuit breakers: Protect against ground faults.
• AFCI (Arc Fault Circuit Interrupter) circuit breakers: Protect against arc faults. 

5. Other Types:

• Miniature Circuit Breaker (MCB): A small, low-voltage circuit breaker.
• Molded Case Circuit Breaker (MCCB): A larger, more durable low-voltage circuit breaker.
• Residual Current Circuit Breaker (RCCB): Also known as an Earth Leakage Circuit Breaker (ELCB), it protects against electrical leakage. 

• RCBO (Residual Current Breaker with Overcurrent protection): RCBOs are a safety measure designed to protect against electric shock, fires, and electrocution caused by earth faults, overloads, and short circuits. 

 LT & HT Side Main Work:

In electrical systems, "LT" stands for Low Tension (typically 415V or 230V) and "HT" stands for High Tension (11 kV or higher). The main work in both HT and LT sides involves power distribution, with HT focused on transmission and LT on local distribution and consumption. 

HT Switchgear mainly use to Shutdown The Transformer.

LT Switchgear mainly use to Control The Load.

PFI Details:

Power Factor: The Cosine of the angle between voltage and current phasors in an AC circuit is known as the Power factor.

 If Φ phase angle between voltage and current, then the power factor is CosΦΦ 

In an ac circuit, there is generally a phase difference between voltage and current. In an inductive circuit, the current lags the applied voltage by an angle of 'ΦΦ ', hence the power factor of the circuit is referred to as lagging, whereas in a capacitive circuit, the current leads the applied voltage by an angle of ‘ΦΦ’, hence the power factor of the circuit is referred to as leading.

Power Factor Formula: Power Factor=Active Power(KW)/Apparent power(VA)

PFI panel circuit diagram

For better understanding, we will look at some devices which we will get inside a power factor improvement panel.

1. Busbar 

2. HRC ( High rupturing capacity) fuse

3. Magnetic contactor 

4. Fixed capacitor

5. Power factor correction relay

6. Indicator light

It has to be noted that, we can control the power factor improvement panel in two ways:

1. Manually by push switch.

2. Automatically by power factor relay.

First, we will discuss the manual operation. We can see the connection diagram in the picture. There is a balloon-shaped device that is a fixed capacitor. This device is used for improving power factors. These devices are placed in different stages.

How Many Stages do We Need and How to Know the Number of Stages?

There are 6,12,24 stages. It depends on the capacity of your factory load. Generally, considering the power rating of the factory transformer the fixed capacitor will be placed in stages. 

1. 6 stage for 500 kVA.

2. 12 stage for 500-1000 kVA

3. 24 stage for 1000 kVA.

And the process is placing values upwards. For example, you need a total of 60 kVA reactive power and if you want to place them in 6 stages the sequence will be 6,8,9,10,12,15 kVA. And the capacitors have parallel connections for getting 380/400/440 volt from the LT panel.

PFI Panel Circuit Diagram

1. 380/400/440 volt supply enters busbar of PFI panel by LT panel’s MCCB.

2. HRC fuse works as the security between the busbar and LT panel.

3. A magnetic contactor helps each capacitor to get a 380/400/440 volt supply from the busbar.

4. Here capacitors have a direct online starter connection with a magnetic contactor. 

5. Capacitors are placed in 6 stages.

6. By activating the push switch, magnetic contactors normally open contact will close. And the capacitor will get power.

7. The activated capacitor will work for the correction of the power factor.

If you want to do it automatically, you have to use a power factor relay. It will supply power by magnetic contactor to fixed capacitor if the power factor decreases. This relay also has a connection with indicator light. Performing capacitor’s indicator light will get activated.

What is Power Generation?

A Generation System can refer to several thing’s But most commonly it means a system that produce energy, typically electricity. This can involve converting primary energy source like fossil, nuclear material, or renewable sources into usable forms.

What is Transmission Line?

Transmission line is a type of line that transmits a high amount of generated power from one station to another via conductive wires.

What is a Distribution Line?

The electricity that is transmitted from the transmission line to residential or consumer-level is called a distribution line.

What is Primary Transmission?

The long, extra-high voltage line from the generating station to the receiving end is called primary transmission.

Primary transmission voltage is usually 110kV, 132kV, 230kV, 400kV, or even higher.

What is Secondary Transmission?

The long high-voltage line from the receiving end to the substation is called secondary transmission. Secondary transmission voltage is lower than primary transmission voltage.

Secondary transmission voltage is generally 33kV or 66kV.

What is Secondary Distribution?

The system that reduces the voltage from an 11kV primary distribution line to 400V or 230V using a distribution transformer for various consumer-level electricity supplies in cities, towns, or factories is called secondary distribution.

What is the Best Method for Transmission and Distribution?

The best method for power generation and distribution is the AC system, and for transmission, the DC system is the most efficient.

What is the Maximum Transmission Voltage in Bangladesh?

The maximum transmission voltage in Bangladesh is 400kV, which is located at Bibiyana-Kaliakoir.

What is a Feeder?

A feeder is an un-tapped line constructed from a high voltage substation or grid substation to various load centers for supplying electricity in densely populated, residential, or industrial areas.

What is the Main Difference Between a Feeder and Distribution?

An un-tapped conductor used to supply electricity from a high voltage substation or grid substation to various load centers in densely populated areas is called a feeder.

A conductor with connection tapping to the consumer’s service mains is called a distributor.

What are the Advantages of High Voltage Power Transmission?

• Line losses are reduced.
• Voltage drop along the line is significantly minimized.
• Transmission efficiency increases.
• Less conductor size is required.
• The cost of power transmission is lower.

What Should Be the Percentage Rate of Frequency Fluctuation?

It should be within 2.5%.

What is the Acceptable Maximum Voltage Drop Rate in a Distributor?

6%

What is System Loss?

The overall power loss due to equipment usage at the production center, resistance loss in transmission wires, and other technical losses is called system loss.

What are the Disadvantages of Low Power Factor in the System?

When the power factor is low, larger conductors are required, line losses increase, system efficiency decreases, and costs increase, resulting in a much higher per-unit cost.

What is the Economic Power Factor?

It is a type of power factor that, when improved, results in the maximum annual savings, and is also known as the optimum power factor.

Fundamentals of Electrical Power Transmission and Distribution:

Electrical power transmission and distribution systems are primarily based on three key aspects.

1. Power Generation
2. Power Transmission
3. Power Distribution

First, power is generated. Then, it is transmitted over long distances. Finally, it is made usable and distributed at the consumer level.

The following diagram shows the entire process simply:

• Typically, 11kV is obtained from the power generation site, which is the generation voltage (varies by country).
• This 11kV needs to be transmitted over long distances throughout the country.
• Before transmitting this 11kV power, it is stepped up to 132kV, 230kV, or 400kV for several reasons, and then it is transmitted over long distances.
• Now, if power needs to be connected to various locations, it is stepped down from 132/230/400kV to 11kV.
• If it is a large mill or industrial establishment, the 11kV is directly connected. It is then adjusted or increased to a usable level.
• For residential purposes, the 11kV is stepped down again to 0.44kV or 440V and supplied to homes or small areas.
• From there, it is transformed to 220-240V as needed for use.

Types of Transmission Lines:

Transmission lines are mainly of two types.

• Overhead
• Underground

OHTL Overhead Transmission Line:

OHTL is an electric power transmission line that uses bare conductors suspended by towers or poles. These lines are used for transmitting and distributing electricity, commonly found in power plants, substations, and rural areas. 

Underground Transmission Line:

An underground power line provides electrical power with underground cables. Compared to overhead power lines, underground lines have lower risk of starting a wildfire and reduce the risk of the electrical supply being interrupted by outages during high winds, thunderstorms or heavy snow or ice storms.

Overhead Transmission Line: Advantages and Disadvantages:

Overhead transmission lines are commonly seen. Especially when traveling or in rural areas, you can see large towers in fields with thick wires attached. This is essentially an overhead transmission line. There are several advantages and disadvantages to this type of line.

Advantages:

• It is safe and feasible to transmit power above 66kV.
• Fault detection in the line is easy.
• Construction and installation costs are much lower.

Disadvantages:

• They occupy a large area.
• If any instrument is damaged or defective, it is costly to repair.

Underground Transmission Line: Advantages and Disadvantages:

In densely populated or industrial areas, underground transmission lines are used. Below are the advantages and disadvantages of underground lines:

Advantages:

• These lines do not occupy much space.
• They are less likely to be affected by various natural disasters.
• Even if any instrument is damaged or defective, it is much safer and easier to repair than overhead transmission lines.

Disadvantages:

• The installation and maintenance costs of underground lines are high.
• They are mostly used in densely populated areas or industrial sectors.
• It is not cost-effective to use these lines for transmitting power over long distances.

What Components are Present in an Overhead Line?

The following components are generally found in an overhead line.

• Support
• Cross-arm and Clamp
• Insulator
• Conductor
• Stay and Guy
• Lightning Arrester

• Guard Wire
• Fuse and Isolating Switch
• Continuous Earth Wire
• Jumper
• Vibration Damper

There are other components as well.

Which Type of Pole Uses a Stay?

A stay is used on angle poles and terminal poles to balance the tension on both sides.

Where is an “H” Type Pole Used?

An H type pole is used in 132 kV transmission lines with a long span of up to 160 meters. It is also used in places where switchgear or transformers are required on the line.

Why is a Transmission Line Typically Grounded?

Sometimes, due to lightning or abnormal conditions, insulation breakdown may occur. To protect the line from such incidents, a continuous earth wire is used over the overhead line, allowing excess voltage to discharge into the ground.

Where and Why is a Cradle Guard Used?

A cradle guard is used for safety purposes. It is employed in places where the overhead line crosses roads, railways, or buildings to prevent the conductor from falling to the ground if it breaks.

What Conductors are Used in an Overhead Line?

The conductors used in overhead lines are:

• Steel-Cored Aluminum
• Copper
• Aluminum
• Galvanized Steel Conductor

In special cases, Phosphor Bronze, Copper-Clad Cadmium Copper, etc., are also used.

 

What Typr of Conductors are Used in an Overhead Line?

• ACC ( ALL Aluminum conductor )
• AAAC ( ALL Alloy Aluminum  conductor )
• ACAR ( Aluminum conductor, Alloy Reinforced )
• ACSR ( Aluminum conductor, Steel Reinforced )

ACSR Conductor is the most common use in OHTL ( Over Head Transmission Line ).

 

What Qualities Should Conductors Have in an Overhead Line?

The qualities that conductors should have in an overhead line are:

• Low specific resistance (high electrical conductivity)
• High tensile strength
• Low cost
• The wire should be strong and flexible
• High melting point
• Durability

What is Skin Effect?

When AC electricity flows through a conductor, it tends to flow along the surface rather than through the core. This phenomenon is known as the skin effect. As a result of the skin effect, line resistance increases, leading to higher line losses.

What is Sag?

Sag refers to the drooping of a conductor between two poles or towers. When a conductor is installed between two points on poles or towers, it sags slightly. The maximum sag occurs at the lowest point of the conductor compared to the imaginary straight line connecting the two points.

Sag Detail’s:

In transmission lines, sag is the vertical distance between the highest point of a conductor (at the support towers) and the lowest point of the conductor between those supports. It's essentially the curve or dip in the overhead transmission line. 

Here's a more detailed explanation:

Why is it important?

Sag is intentionally included in transmission line design to prevent excessive tension in the conductors. If the conductors were stretched too tightly between towers, they could be damaged by thermal expansion and contraction due to temperature changes, or by wind and ice loading. 

Factors affecting sag:

Several factors influence the amount of sag in a transmission line: 

• Conductor weight: Heavier conductors will sag more. 

• Span length: Longer spans between towers will result in greater sag. 

• Tension: Higher tension in the conductor will reduce sag. 

• Temperature: Temperature changes cause conductors to expand and contract, affecting sag. 

• Wind and ice: Wind and ice loading can increase sag. 

Ground clearance:

Maintaining adequate ground clearance is crucial, especially at maximum temperature and minimum loading conditions, to prevent hazards. 

Mathematical representation:

Sag (s) can be calculated using the formula: s = w * L^2 / (8 * T), where 'w' is the weight of the conductor per unit length, 'L' is the span length, and 'T' is the tension in the conductor. 

Example:

If you have a conductor with a weight of 1.54 N/m, a span length of 5 meters, and a tension of 500 N, the sag would be:

S = (1.54 N/m * (5 m)^2) / (8 * 500 N) ≈ 0.0385 meters or 38.5 mm

What is Corona Effect?

The corona effect is a phenomenon of partial electrical discharge caused by the ionization of the air surrounding a conductor. It appears when the voltage exceeds a critical value, but whose conditions do not allow the formation of an electric arc.

What is Ferranti Effect?

The effect in which the voltage at the receiving end of the transmission line is more than the sending voltage is known as the Ferranti effect.

What Happens in a Transmission Line When the Load Power is Very Low?

When the load power is very low, the capacitance effect is generally observed in the line. In this situation, the line carries a 90-degree leading charging current. As a result, the voltage at the receiving end is higher than at the sending end, leading to negative voltage regulation.

Friends, we have already written three articles on power transmission and distribution. Click below to read them.

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A Brief About Overhead Power Transmission Lines (OHTL) (Part 1 – OHTL supports)

Introduction

The electrical power system comprises of three main subsystems: generation, transmission, and distribution. The transmission system is responsible for connecting the generation side to the consumption or distribution side as shown by figure 1.

Most of the power transmission systems are operating in Alternating Current (AC) with several high voltage levels that increases with the increase of the line length to reduce the transmission losses.

AC power transmission lines might be designed to be Overhead Transmission Lines (OHTL) or Underground Transmission Cables (UGTC). The majority of AC transmission lines are overhead transmission lines and the main reason is that the cost of underground cable system is considerably more compared to overhead lines. In general, OHTL are generally used for power transmission at long distances in open county and rural areas in addition to that, OHTL are generally with longer lifespan, easier to install and repair and require lower manufacturing & construction costs in comparison to UGTC.

Sample OHTL and UGTC are shown by figures 1 & 2 respectively:

Overhead power transmission lines components

An OHTL comprises of many several components, the utmost important remain both: supports and conductors. Other components are insulators, insulator and conductor fittings, overhead ground wire, spacers and brackets. Following figure 4 shows samples of OHTL designs with supports and some other components indicated.

Types of OHTL Supports

The main function of the of the OHTL supports (also named: towers, structures or pylons) is to provide the necessary mechanical support for the transmission conductor at the design electrical clearance from ground and also from other phase conductors. In addition to that all towers have to withstand all kinds of environmental effects.

OHTL supports can be made using different types of materials such as wood, concrete, steel, metal alloys and recently fiber reinforced polymers were introduced but still rarely used.

OHTL supports according to their mechanical design are classified into two types:

1.     Self-supporting; which might be of the following types (examples are shown in figure 5)

-         Lattice steel towers.

-         steel poles.

-         Steel reinforced concrete poles.

-         Wooden poles

1.     Guyed or non-self-supported: although those types of supports were introduced at the second quarter of the 20th century, but their use declined with time for the transmission purposes compared to the self-supporting ones. However, guyed supports can be in the H, V or Y shapes. Another use of the guyed supports is for fast transmission system restoration in case of transmission supports collapse or for transmission circuits diversion during projects or modification works and for this purpose, some special designed guyed supports called Emergency Restoration Systems (ERS) that can be assembled in short time in different configurations are used. Respectively a sample H-shape guyed power transmission support and an ERS support are shown in figure 6

Moreover, OHTL supports can be classified according to the mechanical support they are providing to the conductors into:

1.     Angle supports: used when the line is changing its direction with deviation angles varies from 30 to 90 degrees in a standardized value (e.g. 30, 45, 60, etc.).

2.     Suspension supports: used for sections were the line is running straight with some allowed deviation usually not to exceed 10 degrees.

3.     Terminal supports: usually used at substation entry as they are designed to take full mechanical tension on one side and no tension (or slack) on the other side.

Furthermore, OHTL supports might be classified based on the number of circuits they are carrying (supporting); and so, it might be single circuit support, double circuits support or quadrable circuits support and in some rare cases, OHTL support is designed to carry one or more transmission circuits in the upper part of the support and a distribution circuit/circuits or insulated fiber communication cable in the lower part but this kind of supports utilization will be only possible with OHTL with short spans between supports.  

General considerations for OHTL supports design

In this part, the basic steps for the design of an overhead line supports are determined in brief remembering that in the design process, and although it is to some how standardized process, the design is highly affected by the data and requirements provided by the utility itself which are to be as accurate as possible to reflect the local working conditions of the line to be met by the design.

Anyhow, before starting the design of the line supports, the following details shall be provided:

1.     The line electrical requirements such as:

• The minimum clearances between conductors, and between conductor and the support itself.
• Number, type and location of ground wire/wires with respect to the outermost conductor.
• The minimum required mid-span clearance of the lowest conductor above ground level or to other conductors at intersection with other lines conductors.
• Minimum Insulator required creepage path and hence the minimum length of the insulator assembly.
• Electrical loading requirements (this will determine the number of conductors per phase and number of circuits per support.
• Short circuits, Etc.

1.     The line minimum mechanical strengths requirements and required safety factors.

2.     Environmental & and climatic conditions including the proposed preliminary routes/ terrains.

Based on the above details, the supports design process is conducted to provide supports that accomplish the above requirements as below:

a)     Selection of the basic supports configuration and minimum height to meet electrical design requirements. The supports minimum height is governed by:

-         The minimum permissible ground clearance.

-         The maximum sag.

-         Phase conductors vertical spacing.

-         Ground wire to top conductor vertical clearance.

 b)     Determination of the mechanical strength of the selected support configuration: the selected support configuration shall be designed mechanically to withstand the sum of the mechanical loads resulting from electrical requirements, climatic effects, terrain and the added safety factor. It is always to bear in mind during support design that the design the design is meet the loading requirements within the economic requirements of the utility.

The mechanical loads to be determined for the purpose of OHTL support design are:

I. Wind Loads: this step includes the determination of wind loads affecting both, the support and conductors.

II. Conductors load: this step includes the calculation of mechanical loads resulting from conductor’s tensions (the maximum working tension and Every day stress), short Circuit conditions, ice accumulation in cold weather countries.

III. Induced vibration effects.

IV. Finalize the design based on combined Loads: this is necessary to achieve a reasonable design that matches the requirements without being oversized and achieved by the assumption that not all of the factors aforementioned will be at highest together.

V. Applying the safety factor.

VI. Design verification through prototyping and type testing of the supports.

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