1. What is AB electrification and Electricity?
AB electrification and Electricity - refers to a wide range of application of electric energy in the field of agricultural and bioystems production and rural life. It is the important technical basis of mechanization and automation of agricultural production, including the production, transmission, distribution and utilization of agricultural power, the development of agricultural technology and equipment with power as the power, the promotion of household electronics and electrical equipment in rural areas, etc.
Electrification refers to the process of replacing technologies that use fossil fuels (coal, oil, and natural gas) with technologies that use electricity as a source of energy.
Electricity is the energy generated by the movements of electrons (negative charge) and positrons (positive charge) within conductive materials.
2. Discuss the Methods of Producing Electrical Energy.
There are three main steps in the process of getting electricity to a home or business: generation, transmission, and distribution.
Generation: electricity is produced in plants capable of drawing electrical energy from primary energy sources. These primary energies may be renewable (wind, solar power, tidal power, etc.) or non-renewable (coal, natural gas, oil, etc.). The companies which (fully or partly) own the various power plants sell the energy generated to companies which supply it commercially.
Transmission: once the energy has been processed and turned into electricity, it is sent through overhead or underground wires from the plants to substations. There, transformers ensure sufficient electrical voltage. Substations tend to be above ground near to power plants, or on the outskirts of cities, though if they are not too large, they may also be within the actual city, inside a building.
Distribution: from the substations, electricity is distributed to the homes in the surrounding area. As a consumer, you cannot choose your electricity distributor; it is determined by where you live. That company is responsible for ensuring electricity reaches your home properly and takes care of repairs when needed. It is also the company which owns your electricity meter and sends readings from it to your commercial energy supplier.
3. What are the uses and application of electricity in the farm and in the biosystems structures?
Electricity uses in the farm buildings, on the farm land, crop treatment, and in the farm house.
❖ Electric motors were used to drive barn machinery, chaffcutters and root cutters, cattle cake and graincrushers, and water pumps
❖ Electricity’s ease of operation and low maintenance showed savings in time and labour.In the fields, a number of electrically driven, rope-haulage plowing installations.
❖ Electricity plays an equally important part in the dairy farm for feed rationing, milking, and milk cooling; all these applications are automatically controlled
❖ Developed electrically powered equipment for crop conservation and storage to help overcome weather hazards at harvest time and to reduce labour requirements to a minimum
❖ Grain can now be harvested in a matter of days instead of months and dried to required moisture content for prolonged storage by means of electrically driven fans, gas or electrical heaters
❖ Conditioning and storage of such root crops as potatoes, onions, carrots, and beets, in especially designed stores with forced ventilation and temperature control, and of fruit in refrigerated stores are all electrically based techniques that minimize waste and maintain top quality over longer periods than was possible with traditional methods of storage
4. Explain the two categories of electrical systems and the advantages of one to the other.
1. Direct current – flow in one direction; from negative to positive; and supplied through dry cell or storage battery.
2. Alternating current – constant reverses in direction of flow; produced by a generator.
Advantages are:
a. easily produced
b. cheaper to maintain
c. can be transformed to higher or lower voltage
d. distribution to far distance with low voltage drop
e. more efficient compared with the direct current
“AC electricity is dangerous because it involves high voltage transmission line.
However, it can be reduce to desired voltage as it passes the distribution line
5. Illustrate the AC Power Curve and the Phase shift. Differentiate True, Apparent and Reactive Power in relation to power factor.
ALTERNATING CURRENT (AC) is an electric current which periodically reverses direction and changes its magnitude continuously with time in contrast to direct current (DC) which flows only in one direction.
The usual waveform of AC in most electric power circuits is a sine wave, whose positive half-period corresponds with positive direction of the current and vice versa.
A PHASE SHIFT is the delay present between two waveforms that share the same frequency or period. In summary, we express phase shifts in terms of angle, which we measure in radians or degrees that are either positive or negative.
Phase difference is used to describe the difference in degrees or radians when two or more alternating quantities reach their maximum or zero values. The phase difference, Φ of an alternating waveform can vary from between 0 to its maximum time period, T of the waveform during one complete cycle and this can be anywhere along the horizontal axis between, Φ = 0 to 42π (radians) or Φ = 0 to 360o depending upon the angular units used. Phase difference can also be expressed as a time shift of τ in seconds representing a fraction of the time period, T for example, +10mS or – 50uS but generally it is more common to express phase difference as an angular measurement.
The PHASE DIFFERENCE or PHASE SHIFT as it is also called of a Sinusoidal Waveform is the angle Φ (Greek letter Phi), in degrees or radians that the waveform has shifted from a certain reference point along the horizontal zero axis. In other words phase shift is the lateral difference between two or more waveforms along a common axis and sinusoidal waveforms of the same frequency can have a phase difference.
We know that reactive loads such as inductors and capacitors dissipate zero power, yet the fact that they drop voltage and draw current gives the deceptive impression that they do dissipate power. This “phantom power” is called REACTIVE POWER. It is measured in a unit called Volt-Amps-Reactor (VAR), rather than watts. The mathematical symbol for reactive power is the capital letter Q.
TRUE POWER is the actual amount of power being used or dissipated in a circuit. It is measured in watts (W) and symbolized by the capital letter P.
APPARENT POWER is the combination of reactive and true power and it is the product of a circuit’s voltage and current, without reference to phase angle. It is measured in the unit of Volt-Amps (VA) and symbolized by the capital letter S.
6. Discuss and give the formula for Ohms Law and Joules Law.
Ohm’s law, description of the relationship between current, voltage, and resistance. The amount of steady current through a large number of materials is directly proportional to the potential difference, or voltage, across the materials. Thus, if the voltage V (in units of volts) between two ends of a wire made from one of these materials is tripled, the current I (amperes) also triples; and the quotient V/I remains constant. The quotient V/I for a given piece of material is called its resistance, R, measured in units named ohms. The resistance of materials for which Ohm’s law is valid does not change over enormous ranges of voltage and current. Ohm’s law may be expressed mathematically as V/I = R. That the resistance, or the ratio of voltage to current, for all or part of an electric circuit at a fixed temperature is generally constant had been established by 1827 as a result of the investigations of the German physicist Georg Simon Ohm.
Joule’s law, in electricity, mathematical description of the rate at which resistance in a circuit converts electric energy into heat energy. The English physicist James Prescott Joule discovered in 1840 that the amount of heat per second that develops in a wire carrying a current is proportional to the electrical resistance of the wire and the square of the current. He determined that the heat evolved per second is equivalent to the electric power absorbed, or the power loss.
A quantitative form of Joule’s law is that the heat evolved per second, or the electric power loss, P, equals the current I squared times the resistance R, or P = I2 R. The power P has units of watts, or joules per second, when the current is expressed in amperes and the resistance in ohms.
7. Explain/Illustrate/Discuss the following:
a. Resistive Circuits in Series and Parallel
In a series circuit, the output current of the first resistor flows into the input of the second resistor; therefore, the current is the same in each resistor. In a parallel circuit, all of the resistor leads on one side of the resistors are connected together and all the leads on the other side are connected together.
b. Inductance and Inductive Reactance
Inductors and chokes are basically coils or loops of wire that are either wound around a hollow tube former (air cored) or wound around some ferromagnetic material (iron cored) to increase their inductive value called inductance.
Like resistance, reactance is measured in Ohm’s but is given the symbol “X” to distinguish it from a purely resistive “R” value and as the component in question is an inductor, the reactance of an inductor is called Inductive Reactance, ( XL ) and is measured in Ohms. Its value can be found from the formula.
Where:
XL = Inductive Reactance in Ohms, (Ω)
π (pi) = a numeric constant of 3.142
ƒ = Frequency in Hertz, (Hz)
L = Inductance in Henries, (H)
We can also define inductive reactance in radians, where Omega, ω equals 2πƒ.
c. Capacitance and Capacitive Reactance
Capacitive reactance is the opposition by a capacitor or a capacitive circuit to the flow of current. The current flowing in a capacitive circuit is directly proportional to the capacitance and to the rate at which the applied voltage is changing. The rate at which the applied voltage is changing is determined by the frequency of the supply; therefore, if the frequency of the capacitance of a given circuit is increased, the current flow will increase. It can also be said that if the frequency or capacitance is increased, the opposition to current flow decreases; therefore, capacitive reactance, which is the opposition to current flow, is inversely proportional to frequency and capacitance. Capacitive reactance XC, is measured in ohms, as is inductive reactance. The below Equation is a mathematical representation for capacitive reactance.
Where,
f=frequency(Hz)
π=~3.14
C = capacitance (farads)
d. Series and Parallel RLC networks and circuits
In RLC circuit, the most fundamental elements of a resistor, inductor and capacitor are connected across a voltage supply. All of these elements are linear and passive in nature. Passive components are ones that consume energy rather than producing it; linear elements are those which have a linear relationship between voltage and current.
There are number of ways of connecting these elements across voltage supply, but the most common method is to connect these elements either in series or in parallel. The RLC circuit exhibits the property of resonance in same way as LC circuit exhibits, but in this circuit the oscillation dies out quickly as compared to LC circuit due to the presence of resistor in the circuit.
When a resistor, inductor and capacitor are connected in series with the voltage supply, the circuit so formed is called series RLC circuit.
Since all these components are connected in series, the current in each element remains the same,
Let VR be the voltage across resistor, R.
VL be the voltage across inductor, L.
VC be the voltage across capacitor, C.
XL be the inductive reactance.
XC be the capacitive reactance.
The total voltage in RLC circuit is not equal to algebraic sum of voltages across the resistor, the inductor and the capacitor; but it is a vector sum because, in case of resistor the voltage is in-phase with the current, for inductor the voltage leads the current by 90o and for capacitor, the voltage lags behind the current by 90o.
So, voltages in each component are not in phase with each other; so they cannot be added arithmetically. The figure below shows the phasor diagram of series RLC circuit. For drawing the phasor diagram for RLC series circuit, the current is taken as reference because, in series circuit the current in each element remains the same and the corresponding voltage vectors for each component are drawn in reference to common curr ent vector.
e . Delta-Y transformation in terms of R
The Delta-Wye transformation is an extra technique for transforming certain resistor combinations that cannot be handled by the series and parallel equations. This is also referred to as a Pi - T transformation.
Sometimes when you are simplifying a resistor network, you get stuck. Some resistor networks cannot be simplified using the usual series and parallel combinations. This situation can often be handled by trying the \Delta - \text YΔ−Ydelta, minus, start text, Y, end text transformation, or 'Delta-Wye' transformation.
The names Delta and Wye come from the shape of the schematics, which resemble letters. The transformation allows you to replace three resistors in a \DeltaΔdelta configuration by three resistors in a \text YYstart text, Y, end text configuration, and the other way around.
The \Delta - \text YΔ−Ydelta, minus, start text, Y, end text drawing style emphasizes these are 3-terminal configurations. Something to notice is the different number of nodes in the two configurations. \DeltaΔdelta has three nodes, while \text YYstart text, Y, end text has four nodes (one extra in the center).
The configurations can be redrawn to square up the resistors. This is called a \pi - \text Tπ−Tpi, minus, start text, T, end text configuration,
The \pi - \text Tπ−Tpi, minus, start text, T, end text style is a more conventional drawing you would find in a typical schematic. The transformation equations developed next apply to \pi - \text Tπ−Tpi, minus, start text, T, end text as well.
For the transformation to be equivalent, the resistance between each pair of terminals must be the same before and after. It is possible to write three simultaneous equations to capture this constraint.
Consider terminals xxx and yyy (and for the moment assume terminal zzz isn't connected to anything, so the current in \text R3R3start text, R, end text, 3 is 000 ). In the \DeltaΔdelta configuration, the resistance between xxx and yyy is RcRcR, c in parallel with Ra +RbRa+RbR, a, plus, R, b .
On the \text YYstart text, Y, end text side, the resistance between xxx and yyy is the series combination R1+R2R1+R2R, 1, plus, R, 2 (again, assume terminal zzz isn't connected to anything, so \text R1R1start text, R, end text, 1 and \text R2R2start text, R, end text, 2 carry the same current and can be considered in series). We set these equal to each other to get the first of three simultaneous equations,
We can write two similar expressions for the other two pairs of terminals. Notice the \DeltaΔdelta resistors have letter names, (Ra(Raleft parenthesis, R, a, etc.))right parenthesis and the \text YYstart text, Y, end text resistors have number names, (R1(R1left parenthesis, R, 1, etc.))right parenthesis.
After solving the simultaneous equations (not shown) , we get the equations to transform either network into the other.
REFERENCES:
https://www.rff.org/publications/explainers/electrification-101/
https://www.endesa.com/en/discover-energy/energy-and-more/how-electricity-is-generated
http://www.fao.org/3/i2433e/i2433e.pdf
https://www.britannica.com/science/Joules-law
https://openpress.usask.ca/physics155/chapter/6-2-resistors-in-series-and-parallel/#:~:text=In%20a%20series%20circuit%2C%20the,other%20side%20are%20connected%20together.
https://www.electronics-tutorials.ws/accircuits/phase-difference.html