Comprehensive Analysis of AC and DC Power Systems: Report

This report provides a comprehensive analysis of AC and DC power systems. It begins by differentiating between AC and DC currents through graphical representations and discusses key differences such as frequency, direction, and magnitude. The report explains the concept of RMS values and their importance in AC circuits. It then explores the industrial and domestic applications of both AC and DC, highlighting their respective advantages and disadvantages. Furthermore, the report compares AC and DC power transmission, detailing the steps involved and the reasons behind them. Finally, it addresses the hazards associated with AC and DC, including safe voltage levels and the impact of body resistance, concluding with a list of references.

Dc and Ac Systems 1
AC and DC Power
Student’s name
Institutional affiliation
Date

Dc and Ac Systems 2
A. With the aid of graphical representation of dc and ac potential difference and
corresponding current, indication of principle differences between AC and DC.
According to McPherson (2012), electric current can be classified into two different forms.
These include dc (direct current) and ac (alternating current). Direct current is a type of
electrical current characterized by the constant or uniform flow of current in only one
direction. Alternating current, on the other hand, changes its direction of flow and magnitude
at a certain predetermined rate. For instance, the ac power provided by certain utility
companies reverses its direction 50 times every second. The graphical representation of both
ac and dc currents in terms of variation in magnitude with time is given in figure 1 below.
Despite their distinct characteristics, the two types of currents can be converted from one
form to the other and back with the help of electrical circuits such as rectifiers and inverters.

Dc and Ac Systems 3
Figure 1: Graphical representation of a) dc current and, b) ac current
The principles differences between dc and ac current are summarized in the table given below
Dc current Ac current
The frequency of Dc current is always zero The frequency of ac current is usually 50 or
60 Hz, depending on the country or region
Dc current always flows in the same
direction
The direction of flow changes constantly at
a predetermined rate
The magnitude of a dc current is constant The magnitude of ac current changes with
time
Its power factor is always unity The power factor lies between zero and one
It is pure and pulsating It can be generated in several forms such as
sinusoidal and square forms
A. Knowledge of rms value and peak values.
The value of an alternating current changes continually from zero to a maximum peak value
then back to zero in the opposite direction to a maximum negative value. Consequently, most
of the time its magnitude is lower than the peak value which makes peak measurement

Dc and Ac Systems 4
ineffective in the measurement of the true effect of the ac voltage. Instead, the rms (root mean
square) value of the current or voltage is calculated. According to Harsany (2012), the rms
value of a certain quantity can be defined as the squared values of that quantity taken over a
specific interval. Mathematically, it can be expressed as follows,
rms value= √ 1
b−a ∫
a
b
y2 dt
For a sinusoidally varying voltage or current, the rms value is 1
√ 2 which is about 0.7 times
the peak value of the voltage or current,
V rms= V peak
√2
I rms= I peak
√2
It is important to note that the above formulas only apply to sinusoidally varying voltages and
currents. Different formulas arise for other forms such as triangular waveforms. Rms values
provide a convenient method for expressing ac currents and voltages in values equivalent to
dc values. An rms value of an ac current is the equivalent dc value that yields the same effect
(Floyd & Buchla, 2013). For instance, a bulb connected to a 12 V rms ac voltage will shine
with equal brightness if it is connected to a dc supply of the same magnitude.
A. Industrial and domestic applications of AC and DC and their advantages and
disadvantages.

Dc and Ac Systems 5
The two different forms of currents find applications in many different domestic and
industrial applications. Each form of current is suitable for specific applications. The ability
to convert current from one form to another makes it possible and convenient to use any
desired form anywhere (Herman, 2012). Some of the domestic applications of ac and dc
voltages include,
i) Dc and ac voltages are used in homes for lighting purposes. Most electric bulbs
can run on either dc or ac voltages.
ii) Most electrical and electronic appliances used in homes such as radios and
televisions require dc currents for operation. Since most utility companies supply
power in alternating form, rectifiers are used to convert ac to dc for their
operation.
iii) Dc current is used to charge batteries used for power storage, for instance from
solar panels that generate dc currents.
iv) Dc and ac currents are also used to run electric motors used in appliances such as
electric fans. Some motors are designed to run on dc power while others are
designed to run on ac power.
The industrial applications of dc and ac power include
i) Industrial applications such as electroplating require dc currents for effective
operation. Factories can generate their own dc power or they can rectify the ac
power provided by utility companies
ii) Many industrial applications require the use of motors such as running belts or
robotic systems. Depending on factors such as the application and control torque
requirements, ac or dc motors are used.
iii) Ac or dc currents are also used for lighting in industries.

Dc and Ac Systems 6
iv) In the transport industry, electric motors running on dc currents are increasingly
being used in electric vehicles.
The advantages and disadvantages of dc and ac currents are outlined below,
Advantages of dc
i) It can be directly stored in batteries
ii) It is used directly to power all types of electronic equipment
Disadvantages
i) Dc electric power cannot be produced at high voltages due to commutation
problems
ii) Its magnitude can only be changed using dc-dc converters which require active
components and complex circuitry.
Advantages of ac
i) Its level or magnitude can be raised or lowered directly using power transformers
ii) Machines running on ac are simpler in construction and cheaper
Disadvantages
i) It cannot be used to power electronic circuits directly
ii) It exhibits additional losses from charging currents
A. Compare transmissions of electrical power using ac and dc. Highlight the steps
required in the transmission and the reasons for them.
Electrical power is usually generated in places located far away from the consumption centers
(Grigsby, 2016). Consequently, it must be transported over long distances using electrical

Dc and Ac Systems 7
conductors. It is possible to transmit power using either dc or ac voltages. Each of these
forms of power transmission has its own benefits. The table below presents a comparison of
the two forms of transmission considering factors such as economy and efficiency.
Dc transmission Ac transmission
Only two conductors are required fo
transmission with the possibility to use one
conductor and earth as the return. This saves
copper.
Transmission requires at least three
conductors for three-phase systems which
increases transmission costs
The conductor size can be made smaller due
to the absence of skin effect
Conductor size is chosen taking into account
skin effect hence larger size
No charging current Charging currents ven on no-load hence
additional losses
Dc transmission exhibits less corona hence
lower interference with communication
links
Coronal loss is significantly high due to the
high transmission voltages necessary
There is no voltage drop due to inductance
and capacitance effects which increases
transmission efficiency
Inductive and capacitive line effects in
addition to resistive effects increase voltage
drop in the lines.
Steps
The first step in the transmission of any form of power is generation. Power is normally
generated in ac form in power stations using alternators. After generation, for ac
transmission, the next step is to use transformers to raise the level for long-distance
transmission to reduce losses. After transmission, it is stepped down to levels that can be used
in industrial and domestic applications. For dc transmission, rectifiers are used after

Dc and Ac Systems 8
generation to convert ac to dc (Jovcic, 2019). At the receiving station, inverters are used to
convert dc to ac for distribution.
A. Hazard associated with ac and dc: safe levels of ac and dc voltage; typical resistance
of current pathway in the body, skin resistance and changes of environment.
Both dc and ac voltages are hazardous at high levels. According to Jones & Jones (2011),
current is the hazardous factor in electrical shock. Voltage determines the level of current that
flows the body of a given resistance. The skin resistance of a human body has the following
typical values,
Resistance type Resistance value
Wet skin 1kΩ
Dry skin 100k to 600kΩ
Since the resistance of the body changes with the environment, the current that can flow
through the body due to a certain level of voltage changes. Consequently, it is difficult to
have standard limiting values of current and voltage for the safety of humans. According to
Sutherland (2014), an ac voltage of about 50 volts is the safety limit although it could kill
under certain conditions. Dc levels less than about 42.4 volts (safety extra-low voltage) are
non-hazardous. Generally, dc currents are more hazardous compared to ac.

Dc and Ac Systems 9
References
Floyd, T. L., & Buchla, D. M. (2013). DC/AC Fundamentals: A Systems Approach. New
York, NY: Pearson Higher Ed.
Gonen, T. (2011). Electrical Power Transmission System Engineering: Analysis and Design,
2nd Edition. Boca Raton, FL: CRC Press.
Grigsby, L. L. (2016). Electric Power Generation, Transmission, and Distribution, Third
Edition. Boca Raton, FL: CRC Press.
Harsany, S. C. (2012). Fundamentals of Electronics: DC/AC Circuits. MN.
Herman, S. L. (2012). Direct Current Fundamentals. Boston, MA: Cengage Learning.
Jones, R. A., & Jones, J. G. (2011). Safe Work Practices for the Electrician. Burlington, MA:
Jones & Bartlett Publishers.
Jovcic, D. (2019). High Voltage Direct Current Transmission: Converters, Systems, and DC
Grids. MA: John Wiley & Sons.
McNichol, T. (2011). AC/DC: The Savage Tale of the First Standards War. Hoboken, NJ:
John Wiley & Sons.
McPherson, S. S. (2012). War of the Currents: Thomas Edison vs Nikola Tesla. Minneapolis,
MN: Twenty-First Century Books.
Sutherland, P. E. (2014). Principles of Electrical Safety. Hoboken, NJ: John Wiley & Sons.