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Hello everyone, we’re happy that we’re all together again and this tutorial we will
explain some basics related to the world of electrical engineering that will be the
guide for us and the rest of this course. Those are some very important
fundamentals for anyone who works in the electrical engineering field. Are you
ready? Fasten your pill and let’s get it started. The aim of this tutorial is to know
what are the different ranges of the voltage that are used in the electrical field. Also
we will learn what is the relation between the different engineering parameters like
the volage, the power, the current and so on. So let’s go ahead. Indeed there are
some standard ranges of the voltage that are used in the different electrical
applications. And those different ranges are categorized according to some
standards for us to know what are the types or the categories of the voltages that
we are working with so the first category of range is the low voltage range which
starts from 1 volt and it ends at 1 KV so if you are handling any value of
voltage that is in between of those margins you are in the low voltage range at this
condition. Now, the second line is the medium voltage category that has a range
from 1 KV to 66 KV or some other standards consider the medium voltage to ends
at 33 KV. So anyway those are the ranges of the medium voltage also the third
ranges-the high voltage range that starts at 66 KV and ends at 220 KV or 500
KV. Also this is according to some other standards and for example when you
know that there is a step up transformer that rises the voltage from 11 KV to 220
KV, so this means that the primary voltage of the transformer is a medium
voltage and the secondary of this is a medium voltage and the secondary of
this transformer is a high voltage or in other words we say that it’s a medium to
high voltage Transformer. Now the next ranges the extra high voltage that ranges
from 500 KV to 750 KV and finally we have the ultra high voltage that ranges
from 750 KV to 1,200 KV, so those are the voltage ranges map that can guide us
for any value of the voltage to know what is the kind of this voltage that we are
handling. Now after knowing the borders of the voltage ranges, we need now to
know some commonly used values of the voltage that are used much inside those
ranges so the popular values of the voltage and the low voltage Zone as 120 and
220 V and also 380 V. So those are some standard values of the volage that are

used in our homes for the appliances to work on according to the American
standards or according to the pre standard also the popular values of the
medium voltage zone as 11 KV 22, 33, 66, 2.2 also 3.3 and 6.6 . So the medium
voltage devices or Transmission Lines use those values very commonly, while the
high voltage popular ranges are 66, 132, 220, 400 and 500 KV, and for the extra
and ultra voltage the most popular ranges are 500 and 750,1000 and 1200. But now
you may ask why we need to have some standard ranges of the voltage that the
world works according to them? So this is because the electrical devices like the
transformers,the generators or the cables for example so they are designed


mainly according to the voltage’s standards or those voltage’s standards so we
must have some standard level of the voltage that the world must work according
to them to manufacture those devices according to those standards that the world
works on, but if we specified many standards according to each country or each
group of countries at this condition, we must manufacture some electrical
devices with many different standards to cope with many voltage labels and this
will be an efficient solution.
Alright, now let’s move to the main electrical system parameter. So the first
parameter that we will work on of the electrical voltage is the active power and it’s
unit as what, so it’s equal to the voltage times, the current times, the power factor if
we are talking about the AC power. So the power physical meaning is that it’s the
electrical energy that an electrical equipment can consume or produce at a specific
time suppose we have a motor rated of 2,000 W, so this means that this electrical
power that this motor must consume to produce a specific mechanical rotational
power as 2,000 W So it’s supplied by an electrical power to convert it to the
mechanical power corresponding to this electrical power and also when I say that I
have a power station with a power of 500 MW for example, so this means that this
station has some generators that can generate an electric power of about 500
MW. And this power is transmitted to the consumer to get the benefit from it by

converting it from its electrical form some other forms that the user need like the
lighting purposes or to operate some mechanical loads or for the factories loads
and so on now after knowing that the power equals to the voltage multiplied by the
current, we need to know what is the relation between the voltage and the
current. So we have two cases for the relation between the voltage and the current:
- Firstly in case of constant power So at this condition The current will be
inversely proportional to the voltage and this is logically true because of the
voltage increases but we need to get the constant t power so with this
condition the current must decrease to have the same value of a constant
power and the case at which we have a constant value of power when we are
talking about the power source itself as the power source has usually a
constant value of power suppose that we have the same power station
that produces a constant power of 500 MW. Now if we are trying to transmit
this power through a voltage range of 220 KV so it’s a high voltage
range And at this condition The current transmitted will be 2.2 KA which is
a small value. Now if we try to transmit this power on the high voltage range
of 66 KV which is smaller than 220 KV so with this condition, the current
transmitted will increase to 7.5 KA instead of 2.2 KA, also another
example if we have a constant power of 1000 W and we need to transmit this
power through a transformer so at this transformer is a step up one and the
voltage at the primary coil is 10 V and we have 100 A now if we step up this


voltage from 1 V to 100 V so the transmitted ampe on the secondary will
decrease to 10 A instead of 100 A on the primary side so you notice
that when the voltage increases the current decreases As we have a
constant power conduction.
- Now the second case If we are talking about an electric load that consumes
the power. So we are not talking about the electric power source that
supplies the power but now we are talking about the load or the device

that consumes the power. Now, this condition we will have a constant
load with a constant power so the resistive or the impedance is constant and
its relation is the volage over the current, now to get the constant
resistance when the voltage increases, the current must increase for the
resistance to remain constant so in that case of constant load the
evoluges directly proportional to the current now the electric current has
some properts and the most important of them is that is affected sectional
area of the cable used so if we are designing a cable to carry a specific value
of electric current so at this condition the cable cross sectional area will be
designed according to the current that will path through this cable so the
electric current is directly proportional to the cross sectional area and this
is because the cable conductor is supposed to be at you which carries some
free electrons of the electric current so if we have a smaller cross sectional
area than what the electric current need to path through it. So the path at this
condition will be very narrow for the electrons to follow through the
conductor and it will have some collisions with the conductor atoms which it
produces and increase in the conductor temperature. So there will be an
excessive heat that produce in the conductor material and there may be a
failure in the cable or it may be damage or burn out due to the smaller cross
sectional area than it’s required. On the other hand in case of we have a
larger cross sectional area that is suitable for this amount of electric current
to flow and to at so at this condition the flow of the electric current or the
electrons will be very easy with no collations with the conductor atoms.
Now the final thing we have is the voltage designing conditions so if the current
was directly proportional to the cross sectional area here the voltage is
directly proportional to the insulation level this is because the voltage is nothing
but an electromotive force so the volish can be represented by the force that those
electrons are moving with so we must ensure that the insulation is
sufficient enough to be stronger than the voltage level to ensure that the voltage
force will not prey the insulation force like this case here and for this reason we

can note that at the high voltage caples they have a large insulation level than the
low voltage insulation level and this is because when the voltage increases the
magnetic field produce from the cable will increase so we must surround this large


magnetic field and this large electromotor force with the sufficient insulation
level to avoid the case of break of insulation. So I think that’s enough for
this tutorial about some electrical fundamentals and at this point we have
finished how basically right now thank you for watching and see you next tutorial.