Electrical Current Flow Effects

When the electrical current flow in a load circuit the result will be light, heat generation, electromagnetism and chemical reaction, let us clear these effects:

Heat generation:

As an example when electrical current flows throw incandescent lamp, heat will be generated throw the conversion of electrical energy to thermal energy inside the lamp components. Also when electrical current exceeds the rated value of the fuse, fuse link will be melted due to excessive heat.

Electromagnetism:

In fact electricity may be used to produce magnetism and also magnetism can be used to produce electricity. When any conductor carries electrical current, magnetic field will be produced around this conductor where magnetic field strength will proportional to the amount of current flow in the conductor. Magnetic fields will take various forms with a variable strength according to the conductor shape as following:

When the electrical current passes throw a straight conductor the magnetic field will form circular lines around the conductor.

When the electrical current passes throw a loop conductor, the magnetic field lines will be concentrated to make a strong magnetic field, in this case magnetic field strength will proportional to the current value and the number of turns .If we put an iron core inside these coils we can get strong electromagnetic field as the iron material increase the magnetic filed strength.

Chemical reactions: 

When a battery is connected to an external electrical load, electrical current will flow throw it, the question is how the current is generated from a battery?

The answer is, each battery consists of two different metals and acid mixture with water, when a chemical reaction between these components is done, voltage difference will appear between the two battery terminals and the current will flow across the load until the two metals become the same and the acid reduced to nearly zero. On the other hand when we charge a battery by an alternator the reaction will reversed as the chemical reaction will produced by the current flow consequently  the current will make electrochemical reaction that restore again the metal and the acid with water mixture until the battery will be full charged again .

Electrical Current Flow Theory

How can you catch electricity?

Electricity is a form of energy that we cannot live without it. Sometimes it called the unseen force as we cannot see, touch and smell or hear it.But on the other hand we see the effect of electricity when the lamp give the light or when the motor rotates …etc. and we can hear the effect of electricity when a fuse blow out also we can smell the effect of electricity when some insulated wire are over heated due to the excessive amount of current pass throw it so the insulation is burned.

Theory of the electrical current flow:

We have two theories that describe how the current flow throw any load,the first one called conventional theory and the second called electrons theory, let us know the difference:

Conventional theory:

It says that the electrical current flow throw any load from the positive to the negative side of the power supply as it see that the free electrons flow from the high potential side to the low potential side. This theory is usually used for automotive systems.

Electrons theory:

It says that the electrical current flow throw any load from the negative to the positive side of the power supply as it see that the free electrons flow from the high number of electrons side to the low number of electrons side to balance the charges inside the power supply. This theory is usually used for electronics systems.

About the effect of the current direction, in fact some devices like diode are affected by the current direction and other devices don't affect as resistive loads.

Electrons flow and electrical current formation:

There are a number of electrons in the inner and outer orbit of the atom, the electrons present in the outer orbit are away from the nucleus and less attracted to it, so we call them "free electrons" as the are so easy to move . Electrical current is formed when these free electrons move from one atom to the next one. These electrons become free due to a certain force like heat, friction, pressure, chemical reaction or magnetic action.

Electrical earth mat for 33kv substation.

What is an electrical earth mat? Well the attached pictures shows you an earth mat installation in progress at a 33kV substation.



Picture 1: Earth mat installation in progress







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Electricity from Generators to Loads

Electricity makes our life comfortable and easier. We use electricity more and more every year and off course we need it in places far from the generation power plants places. So in most cases electricity must move for along distances from one place to another before it will be used and the same time there are a standards present in the loads places that describe the electricity specifications that will operate our machines and appliances. 

Let’s trace the path of electricity from a generation power plant to the load (a lamp or other appliance) present in your house:

First, the electricity is generated at power generation plants and then it moves through conductors to power transformers that will steps up the electricity voltage (called step up transformers) to a standard known level and then the electricity is transmitted throw of transmission lines network whichcalled "electric grid" .These transmission lines consist of huge tower lines that you can see along the highway and all transmission lines are connected together.

The reason that makes us step up the voltage before transmission is to reduce electricity losses in the conductors.

Second, near to cities that comprise the electrical loads there will be a step down transformers located in substations (contain transformers + switches + another electrical equipment's) at the end of the transmission lines referred above, this step down transformers reduce the voltage value to another standard level.

Third, this reduced voltage electricity is then carried by distribution lines that deliver the electricity to another step down transformers, present in the center of the cities and villages at the vicinity of the customers electrical loads and usually these step down transformers are called distribution transformers and they sound as a large gray metal box mounted on an electric pole. Distribution lines can be overhead lines or underground cables.

Finally, this reduced voltage electricity out from the distribution transformers feed your electrical loads in your house like lamps and other equipment's as the generated reduced voltage is suitable to operate them according to the standards and to your local regulation.

The electricity enters your house through a three-wire cable, controlled by

a circuit breaker or a fuse to feed your outlets and wall switches in your house and off course the utility company puts an electric meter beside this circuit breaker or fuse to measure how much electricity you will use every month.

Electricity Generation Fuels

Electricity generation fuels type is differ from one country to another, Let us take United States as an example; there are "four " kinds of power plants fuels that produce most of the electricity in united state:  Coal, Nuclear, Natural Gas and Hydropower as coal plants generate almost half of the electricity in United State and on other hand the renewable energy source " geothermal, wind, and solar power plants ", generate three percent of the produced electricity .In other countries, we will see another types of fuels and another percentage for each fuel. Let us know about the (4) type's power stations that mainly united state depends on:

(1) Fossil Fuel Power Plants:

Fossil fuel power plants burn fuels like natural gas, coal or oil to produce electricity. These energy sources are called fossil fuels because they are formed from the remains and residuals of an ancient sea plants and animals. Most of our electricity is generated from these fossil fuel power plants.

Power plants burn the fossil fuels and use the heat generated to boil the water into a steam, this steam is channeled through a number of pipes at high pressure to move a turbine generator providing the electricity. Fossil fuel power plants have many disadvantages as they produce emissions that pollute the air, contribute to global climate change and also they are considered as less efficiency type of power plants. Sometimes we call fossil fuel power plants as a thermal power plants because they use heat energy to make electricity (note that "Thermeis" is the Greek word for heat).Most fossil power plants in the United States use coal because it is cheap and abundant to extent that almost 92 % of the coal in the United States is sent to power plants to generate electricity.

(2) Nuclear Power Plants:

Nuclear power plants are called also thermal power plants as they generate electricity in the same way as fossil fuel plants referred above, except that they use uranium as a fuel which isn’t burned.

Uranium is a material found in the rocks underground. A nuclear power plant splits uranium atoms into small atoms in a process called "fission"and the result is a huge amount of heat. This heat is used to convert water into steam, which drives a turbine generator and finally electricity is generated.

Nuclear power plants don’t produce carbon emissions, but their waste is radioactive. Nuclear waste must becarefully stored to avoid contamination of people and the environment.

(3) Hydropower Plants:

Hydropower plants use the kinetic energy resulting from the moving of the water to generate electricity as this Fast moving water spin the blades of a turbine generator. Hydropower is considers as a renewable energy source because it is generated from rainfall.

Not only United states but all countries all over the world aims to increase the usage percentage of renewable energy such as wind, solar, ..etc. to avoid the many disadvantages resulting from using the fossil fuels.

Electricity Cost

The cost of electricity with respect to electricity supply authorities depends on several factors. If these factors cost increased, the cost of the customers consumed electricity "kwh bill" would increase. So electricity supply authorities should be more interested in reducing these factors cost.

What are the factors that affect electricity cost?

Mainly there are three factors:-

(1) Fuel Cost:

It considered as the most effective factor that affect the cost of electricity generation, in fact many energy sources (fuels) can be used to generate electricity but with a variable cost for example, the cheapest fuel cost is the falling water power used in hydropower station and the most expensive is the sun rays used by solar cells in solar power station.

(2) Building Cost:

The second factor affect the electricity cost is the cost of the power plant building itself and also its components for example nuclear power plants are very expensive to build, but on the other hand their fuel (uranium) is inexpensive. Also Coal-fired plants are cheaper to build, but their fuel (coal) is more expensive so electricity supply authorities commonly do a number of technical studies in indicate the most cheaper and effective power plant type.

(3) Efficiency:

One of the most important factors that figure electricity cost, as supply authorities must also consider the plant’s efficiency. Efficiency is the amount of useful energy you get out of a system compared to the input energy. The most efficient machine is the machine that converts all the energy input into useful work with fewer amounts of losses. So in power plant, the more the plant efficiency the less the cost of electricity generated.

In general, today’s power plants use (3) units of fuel to produce one unit of electricity (kwh), as a typical coal power plant burns about 8100 tons of coal each day and about two-thirds of the chemical energy in the coal (5,300 tons) is lost as it is converted first to heat energy and then to kinetic energy, and finally into electrical energy.

Most of the lost energy in power plants is the heat. You can notice this wasted heat in the big clouds of steam pouring out of the towers on some power plants

Over Voltage and Voltage Swell

They are considered as a sever power quality problems present in electrical distribution network that have damage effects on the electrical equipments.

What do over voltage and voltage swell mean?

Over Voltage: is the increase in AC RMS voltage at power frequency to greater than 110% of the network nominal voltage and for duration longer than one minute. According to IEEE 1159/1995, increased voltage will range from 110% to 120% of the nominal voltage and for duration longer than one minute.

Voltage Swell: is the increase in AC RMS voltage at power frequency to the rang between 110% to 180% of the network nominal voltage and for duration rang from 0.5 cycle (10 ms) to one minute. According to IEEE 1159/1995, increased voltage will range from 110% to 120% of the nominal voltage and for duration rang from 3 sec to one minute.

What are the causes of over voltage and voltage swell?

Over Voltage Causes:

(1) Load switched off and power factor correction capacitors switched on.

(2) Poor system voltage regulation.

Voltage swell causes:

(1) Single line to ground fault .  

(2) "Start – Stop" of heavy loads.

(3) Bad dimensioned power supply and bad regulated transformer mainly at off-peak hours.

What are the impacts of over voltage and voltage swell?

These two problems have more dangerous effects on electrical equipment's and electrical distribution network components than under voltage and voltage sag as following:

Over Voltage Impacts:

Over  voltage causes many problems with the equipments that required steady state voltage especially modern load so it causes malfunction, miss operation and in some times full operation stoppage.

Voltage Swell Impacts:

Voltage swell causes many problems like:

(1) Data loss and flickering of lighting and screens.

(2) Stoppage or damage of sensitive electrical equipments especially if the voltage values are too high.