Power System

What is Electrical Power System?

The electrical power system is an important part of electrical and electronics engineering. The electrical power system is a bunch of conductor networks. Basically, the electrical power can be supplied in the two ways, such as three-phase, and single-phase power supply. The unit of electrical power is watts because the electricity is measured in units of power that are called watts. Noted that we will broadly discuss high voltage power system analysis. We will explain the generation transmission and distribution of electricity or power generation and distribution process. So take a look and get a better idea about the generation transmission and distribution system.

What is the Sources of Electricity?

We know that an electrical power system consists of three main parts, such as power generation, transmission system, and distribution system. Though there are lots of renewable energy sources in the world, such as water, wind, sunlight, biofuels, nuclear energy, and others but these are not at the professional level for all countries. It is noted that electrical power is generated in the electricity generation station by the combination of some devices.

In this case, we can say that the generating station is the source of electricity. But if we consider the battery then the battery is also the source of DC electricity. Modern AC power transmission systems can be divided into two, such as AC transmission and DC transmission. In an AC transmission system, three-phase three-wire transmission and three-phase four-wire systems are commonly used in the distribution systems.

Components of Electrical Power System

power-system-component

An electrical power plant is a place where electrical energy is generated by some special plan and process. Electricity is transmitted from generating station to the load center by the transmission line and voltage is stepped down by using step-down transformer. Basically, these processes happen through a massive plan and a large number of devices. Indeed all the process happens due to the use of electricity in our daily life. Basically, the power generation and distribution process are not easy due to some difficulties. The modern power system consists of a large number of components, and these are used in various places. These valuable components are given below.

  • Service transformer.
  • Electrical power transformer.
  • Instrument transformer.
  • Lightning arrestor.
  • Web trap.
  • Alternator.
  • Turbine.
  • Transmission line.
  • Switchgear equipment.

Certain standard voltages for transmission and distribution are common in the world. The maximum convenient value for the system is determined by considering the capacity of the generator.

What is Transmission Line

The transmission line is one of the major parts of the power generation and distribution process. A transmission line is a huge high voltage circuit that is built for high power transmission from an electrical power plant. For high voltage power transmission, the transmission line is a single circuit, or double circuit. There are two types of transmission lines based on operating voltage:

  • Primary transmission: 230KV, 132KV
  • Secondary transmission: 66KV, 33KV

There are different types of transmission lines, and it depends on also the power plants. Suppose hydroelectric power plants are placed in a remote area (hilly area) and a high voltage transmission substation is located far away from the hydropower plants. Another thing is that power consumer locality can be far away from the hilly area. For this reason, hydropower transmission becomes long. Based on the category transmission lines can be short, medium, and long lines:

Short Transmission Line:

Basically, the short transmission line is available and it is spread like a net. Most of the power plants (coal, oil, nuclear, and gas power plants) are placed near the consumer locality. For this reason, the short transmission line area is more. If the length of a transmission line is less than 80KM and the line voltage is less than 20KV then it is called a short transmission line.

Medium Transmission Line:

There are also large numbers of areas for the medium transmission line. Basically, the medium transmission line is used to transmit electrical power within mid-range areas. If the length of a transmission line is more than 80 km but less than 200KM and the line voltage is more than 20KV but less than 100KV then it is called a medium transmission line.

Long Transmission Line:

Basically, hydroelectric power plants are located in the hilly area. For this reason, the transmission substation is located far away, and the transmission line length becomes long distance. If the length of a transmission line is more than 200KM and the line voltage is more than 100KV then it is called a long transmission line. It is noted that there are more advantages to transmitting electrical power over a long distance.

What is Transposition in Transmission Line?

Transmission line transposition equals the average inductance capacitance of each line, resulting in relatively improved voltage regulation. Transposition is the periodic exchange of transmission line conductors. A transposition system is done to reduce crosstalk and improve the transmission system. In telecommunications, when three conductors are alternately switched in a power transmission line, the transposition system is applied to the balanced pair.

What is Power Distribution System?

The electrical power generation and distribution process are the first and last steps of the power supply system. A distribution line is a circuit that is built to deliver or distribute electric power at the consumer level, i.e. shops, houses, industries, etc. It has many branches and is connected by numerous tapping services. There are two types of a distribution system based on the distribution voltage:

  • The primary distribution system and voltage ranges are 1KV, 6.6KV, and 3.3KV.
  • The secondary distribution system and voltage ranges are 400V and 220V.

Electricity Generation Transmission and Distribution system

Explain the generation transmission and distribution of electricity is essential. Because all the electrical engineers should know the electricity supply system. Whereas bulk electrical energy is produced by a special plant which is called an electrical generating station. Basically, the generation voltage is 11KV and steps up to a very high voltage based on the transmission distance (usually 132KV, 230KV, 400KV, etc.).

Electrical-supply-process

The electrical power can be transmitted in the two ways, such as a three-phase three-wire system, and three-phase four-wire system, etc. The AC three-phase three-wire system is the most common for electric power transmission. The AC 3 Phase-4 wire method is widely used in secondary distribution systems. In addition, different methods can be used for the transmission and distribution of electric power, such as:

  • DC system: (two wire DC system, DC two-wire with main pointed earthed, DC three-phase system.)

What is Electrical Grid System?

The high voltage electrical power line is spread like a net in the entire country from power generation and distribution process, to share power it is called a grid system. The power of any power plant can be shared (older power plants can share power with new power plants), and it can be transmitted from one place to another place.

A grid system or power grid is the system of a combined supply of electricity generated by multiple power plants through a transmission line at a certain high-quality voltage within a network. In short, whenever some of the power plants operated together or share power to meet the load demand it is called an interconnected grid system.

There are more privileges of the interconnected grid system. Suppose three power plants are operating together and generating a certain amount of electricity to meet the load demand. if one power plant is collapsed then some other power plant can share the load until maintenance of the collapsed power plant. it is noted that the older power plants can be run by following the electric power grid or ac power grid system.

What is Corona Effect?

The phenomenon of violet glow and producing hissing noise is called the corona. Corona always occurs in an AC circuit. A special stage occurs when two conductors are kept in a position greater than the spacing diameter and their horizontal AC voltage is gradually increased.

corona-formation

The air around this special phase conductor is ionized by electrostatic stress and the insulation in the air breaks. In this state, light purple rays are seen and weight gas is formed which is known as the corona.

Influence of Corona:

  • Purple rays can be seen around the conductor.
  • Weight is created by gas.
  • Power loss.
  • Harmonics current is created.

What is Proximity Effect?

When there is another conductor next to one conductor, its flux is induced in the current conductor next to it. The results of this flux appear to be greater in the near half than in the distant half of both conductors. As a result, unequal current distribution occurs, and resistance like skin effect increases. This phenomenon is called the proximity effect.

Influence of Proximity Effect:

The alternating flux is produced in the conductor due to the other nearby conductor current. This alternating flux generates an eddy current or circulating current in the conductor and power loss occurs in the windings. The proximity effect is highly responsible for the increase of the nearer conductor as compared to the DC current resistance. This effect is increased with frequency. The conductor AC resistance can increase ten times more than DC resistance. The effect of proximity effect causes unequal current distribution in the conductor and increases the resistance and decreases the value of self-reactance.

Way of Reduce Proximity Effect

  • Leaving the frequency range low.
  • Increases the spacing of the conductor.
  • Using standard conductors.

What is Ferranti Effect?

The Ferranti effect is one of the important parts of the modern electrical power system. Whenever a medium and long transmission line is unloaded or connected with very little load, a leading charging current flows, and the voltage at the receiving end is found to be higher than the receiving end. This phenomenon is called the Ferranti effect.

What is Overhead Transmission?

Overhead means above the head. The line that is drawn over the head is the overhead line. In the case of overhead transmission, the maximum stress is between conductive and neutral. That is why in case of saving, it is better to consider the maximum voltage conductor for transmission of even power, even distance, even in the neutral wire.

We already discussed above explain the generation transmission and distribution of electricity. You can get better knowledge about overhead transmission voltage range. Main considerations: Cost, Life, Brittle, Weight, Resistance, Power loss, Tensile strength, Low specific-gravity, Temperature Co-efficient, shorter Sag. There are some main parts or equipment used in the overhead transmission line, such as

  • Conductor.
  • Supports.
  • Insulator.
  • Cross arms.
  • Others-phase plates.
  • Danger plate.
  • Lighting arrestors.
  • Anti-climbing wires.
  • Ground wires.
  • Bird guards.
  • Vibration damper.
  • Jumpers.
  • Fuses and Isolating switch.

What is Insulator?

The insulator is a mechanical device that is used to separate the line conductor from the earth connection. Basically, the insulator is made of porcelain. There are different types of elements of insulators, such as porcelain, glass, steatite, Pyrex, etc. However, the best insulator material is glossy porcelain. Basically, different types of Insulators are used for the overhead line based on the transmission voltage, such as

  • Pin type.
  • Suspension / Disc type.
  • Strain type.
  • Shekel type.

Qualities of Insulator: Mechanically strong and robust, with high-quality electrical resistance, high-quality relative permeability, high ratio of puncture strength, and spark overvoltage.

External causes of overvoltage in overhead line

causes-of-overvoltage

Overvoltage and overcurrent both are common causes of the modern electrical power system. Overvoltage can occur for different reasons. One of the most reasons to occur overvoltage and overcurrent is lightning. The lightning effect is the major effect for the high voltage and low voltage power lines. Basically, there are two ways to occur electric faults, such as internal cause and external cause. There are some ways to occur external, such as

  • Direct lightning stock.
  • Electric induction.

What is Safety factor?

The safety factor is an important issue in the electrical power system. The ratio of puncture strength and flash overvoltage is called the safety factor. Suppose we are calculating for a residential safety factor then we have a current value of 20 Amp and a safety factor has 35%. In this case, we have to design an electrical system by multiplying current and safety factors (20 * 25%) = 7 Amp

What is String efficiency?

String efficiency is the ratio of the total voltage of a string and the number of disks in the landscape of the disk closest to the multiplier conductor.

What is Sag and Tension?

The distance from the horizontal imaginary line connecting the two points at which the two towers are drawn or connected to the maximum hanging point of the wire is called sag. That is, the difference between the lowest point of the conductor and the plane of the support is called sag.

Tension is the tensest state of the conductor, and this condition occurs in the winter season. Sag and tension are inversely proportional to each other. If the sag is increased ten tension decreases and if tension increase then sags decrease vice-versa. There is a statutory limit of sag and tension for the overhead conductor.

What is Underground Cable?

The line that is drawn under the ground is the underground line. When the power is transmitted through the underground cable, there is more pressure on the insulation of the two conductors. In this case, the maximum voltage between the two conductors is considered to save copper. It is noted that the underground cable is much superior to the overhead conductor.

Basically, the underground cable is made of many insulations. Because if a fault occurs then it is complex to find and make health. It is noted that the chances of underground faults are very rare than the overhead transmission line. There are some special parts of an underground cable that are given below:

  • Serving.
  • Armoring.
  • Bedding.
  • Lead sheath.
  • Paper insulation.
  • Conductor.
underground-cable

Advantage of Underground Cable:

We know that there are two types of transmission systems: underground transmission and overhead transmission systems. Those who are developed country they used underground systems because the underground system is very costly than the overhead transmission system. The advantages of an underground transmission line are given below.

  • The underground system has no corona discharge like the overhead transmission system.
  • There is no chance to occur surge voltage due to lightning.
  • It ensures maximum public safety and no chance of getting a shock.
  • More reliable in any natural disaster including rain, snow, wash, and thunder.
  • Basically, the underground maintenance cost is low compared to the overhead transmission system.
  • One system is highly reliable and guaranteed availability.

Does an ungrounded electrical system require the main bonding jumper?

There are two types of electrical transmission systems overhead transmission and Underground transmission systems. It is true that the underground system is much superior to the overhead transmission system, and there is less chance to occur faults. But it is very expensive than the overhead transmission line.

There are also some demerits of the underground system but it is more secure and reliable. Basically, the main bonding jumper is used to connect the grounding conductor contained in each branch circuit. This main bonding jumper needs to contain a means of disconnecting (switch) for electrical service that encloses the base tie with neutral conductors that need to be disconnected from the service.

What is Electrical Substation?

An electrical substation is a crucial part of the electrical power system. Whereas voltage level is changed (high voltage to low voltage or low voltage to high voltage) by the special apparatus (transformer, and other switchgear equipment) which is called substation. Management of substation equipment in electrical supply system which helps in changing various characteristics such as voltage, AC to DC, frequency, power factor, etc.

substation-components-electrical-power-system

The substation between the power plant and the customer is a medium station where the electrical energy is received by multiple feeders with the help of electrical equipment and converted to different quality supply voltage with the help of transformers.

What is the Importance of Electrical Substation?

The substation is a crucial station in the electrical power system. Whereas voltage level is divided by some special devices and smart process which is called electrical substation. Substations can be used to step up the voltage level and step down the voltage level. However, there are large numbers of equipment are installed at the electrical substation.  There is no comparison of electrical substations in the electrical power system. Substations are required for the installation of high voltage and low voltage switch gears, circuit breakers, isolators, relays, etc.

  • The medium voltage generated in the powerhouse within the transmission substation can be transmitted to the far edge by increasing the high voltage.
  • If the frequency is low in any substation the frequency is improved that is sometimes called frequency changer substation.
  • The high voltage AC to DC or high voltage DC to AC is converted in a substation that is called converting substation.
  • The incoming and outgoing line through the switching substation is completed in the switching operation.

The main Consideration to Build a Substation

We know that substation is an important part of the modern power system. Basically, electrical voltage is divided into the substation. Sometimes voltage can step up or step down by using a power transformer. There is more consideration for building a substation. If you would like to select places for the electrical substation you must think about some important terms:

  • Ensure availability of water source because water is required to generate steam.
  • Make sure about the sufficient cooling arrangement.
  • Find a location that is far away from the locality.
  • Select such a place where the transportation system is good.

What are the Types of Substations?

substation-types-electrical-power-system-details

We told before electrical substation means that whereas voltage level is changed by using some special apparatus. the transformer is one of the most crucial devices in the substation that is used to change voltage levels. There are different types of substations but we are discussing some of them.

What is Transmission Substation?

This substation connects 2 or more transmission lines. This type of substation uses a high voltage switch to keep the line connected to the isolator for fault removal and repair. This substation uses a transformer to convert the two transmission voltages. Using a capacitor, reactor, or static VAR for voltage control, the electrical transformer here also works like phase shifting.

What is Transformer Substation?

The transformer is one of the major components of the power generation and distribution process. A transformer substation is a point where the transmission voltage level is stepped down, then it is taken to the distribution substation level to a distribution substation. To send It is also supplied from transmission substation to sub-transmission level power industry. Indeed, most of the substation in the modern electrical power system is transformer-type substation.

What is Distribution Substation?

The distribution substation is located very close to the customer. The distribution substation converts transmission power or sub-transmission power to the distribution level. Which is given to industrial, commercial, and residential customers. And their secondary output is distributed to lower-level customers.

Unit Substation

A unit substation is a substation that is electrically and mechanically connected to one or more transformers and one or more switchgear is located. The secondary substation is defined as a unit substation with 1 outgoing maximum 1000 voltage. It is noted that all the high voltage substations have an electrical power transformer to change the voltage level.

What is Power Factor?

Power factor is the cosine of the angle between voltage and current in an AC circuit. It means that the power factor is the phase difference between voltage and current, which is denoted by ɸ. We can say the term power factor is cos ɸ. Current lag behind the voltage if the AC circuit is inductive which is referred to as lagging. If the capacitive circuit leads the voltage the power factor is called the leading power factor. The power factor formula is (power factor) = (real power)/ (apparent power), or P.F = KW/KVA.

  • I cos ɸ in phase with voltage (V).
  • I sin ɸ 900 out of phase with voltage (V).

Whereas, I cos ɸ is the active power or wattful component, and I sin ɸ is the reactive power or wattles component. It is noted that, If the reactive power of a circuit is high then the power factor becomes low. If the reactive power becomes low, then the power factor becomes high. (Vice versa). The value of the power factor is not more than unity (1). In some cases, the power factor is expressed in percentages, such as 0.8 lagging power factor is sometimes referred to as 80%.  

What is Power Triangle?

The power triangle is an important factor in high voltage power system analysis because we get the power factor, apparent power, active power, and reactive power. If we analyze the power factor, then we get a solution. Assume that, OAB is each side current triangle, if it is multiplied by the voltage V then we get the power triangle or power factor formula.

  • OA = VI cos ɸ that represents active power in watt (W) or KW.
  • AB = VI sin ɸ that represents reactive power in (VAR) or KVAR.
  • OB = VI that represents apparent power in (VA) or KVA.
power-factor

We know that apparent power is the whole power of a circuit basically, there are two types of apparent components, such as active power and reactive power. If the active and reactive power is right angle to each other we get

OB2 = OA2 + AB2

(Apparent power)= (Active power)2 + (reactive power)2

(KVA)= (KW)2 + (KVAR)2

(PF) Power factor cos ɸ = OA/OB

Power factor cos ɸ = Active power/Apparent power

Power factor cos ɸ = KW/KVA

It is noted that reactive power is directly responsible for the low power factor. The above equation or power triangle shows that the higher the power factor, and lower the reactive power.  

(Reactive power) KVAR = KVA sin Φ

KVAR = KW/cos Φ (sin Φ)

KVAR = KW tan Φ

What are the Causes of Low Power Factor?

The power factor is an important part of the power generation and distribution process. There is a limit to the power factor for the load. Basically, the standard power factor is considered between 0.8 to 0.95 if the power factor becomes less than 0.8 then the power factor is considered as the low power factor. In this case, we need to improve the power factor by using some devices. There are some reasons for the low power factor, such as 

  • Basically, the inductive type load is responsible for the low lagging power factor. Most of the AC motor is the inductive type, and the induction motor (three-phase, single-phase motor) is highly responsible for the low lagging power factor (0.2, 0.3).
  • Industrial heating furnaces, electric discharge lamps, and arc lamps are also responsible for the low lagging power factor.

What are the Power Factor Improvement Equipments?

 The power factor is the angle between voltage and current. Power factor is an important consideration in the AC circuit and power generation and distribution process. The maximum value of the power factor is one and the minimum value is considered zero but sometimes the power factor becomes low due to some reasons. There are some devices or components to improve the power factor, such as

Static Capacitor

static-capacitor-power-system-details

The static capacitor is the power factor improvement device. The static capacitor is connected in parallel with the equipment that supplies the lagging power factor. This capacitor draws the leading current and completely neutralizes the lagging reactive component of the load current. In this way, the power factor is increased and power loss is also decreased. If the power load becomes three phases then the capacitor can be connected in series or delta. It is noted that static capacitor is widely used in the industry to improve power factor.

Synchronous Condenser

The synchronous condenser is a Synchronous motor. Synchronous condenser means that overexcited Synchronous motor running on no load. An overexcited synchronous motor takes a leading current and behaves as a capacitor. If a Synchronous condenser is connected in parallel with the supply then the synchronous condenser takes a leading current and completely neutralizes the lagging reactive component, and improves the power factor. Phase advancer is also used to improve the power factor.

Disadvantages of Low Power Factor

Basically, the power factor is the angle between voltage and current, and the power factor is a crucial part of the power system. The highest value of the power factor is 1 and the low value is 0 but the standard is 0.85 or more. We know that the low power factor is responsible to increase revenue. There are some disadvantages of low power factor, such as

  • The power factor is inversely proportional to the load current. It means lower the load current higher is the power factor vice-versa.
  • KVA rating is responsible for the low power factor. It means if the KVA rating becomes high power factor will be low vice-versa.
  • If power becomes low then copper loss becomes high.
  • Voltage regulation becomes poor if the power factor becomes low. It means a greater voltage drop occurs in the transmission line, transformer, alternator, etc.

Leave a Comment