Electrical Engineering

AN INVESTIGATION INTO THE CHARACTERISTICS OF HIGH AND LOW

VOLTAGE ELECTRICAL POWER DISTRIBUTION NETWORKS

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December 9, 2018

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Introduction

For the past few years, innovations and simulation systems have dominated the electrical

engineering sector in order to improve various aspects of transmission of various voltages.

Besides, it is important to note that transmission of voltages occur based on a number of

generational aspects. High and low voltage distribution occurs based on the specificity of the

characteristics that create the major differences in the system (Cotilla-Sanchez et al., 2012, p.

12). In order to understand the differences in the characteristics involved in the two transmission

system networks, a number of experiments were carried out using various transmission voltages.

This report seeks to discuss the characteristics of generation, transmission and low voltage

distribution networks based on the research that was carried out using the tests and laboratory

experiments using the voltages.

Background of the study

There has been intense research on the differences in the characteristics of high and low

voltage electrical power distribution networks for quite some time. Having been motivated by

such research, various tests were carried out with the aim of understanding the practicality that is

often associated with transmission of high and low voltages in various system networks (Cotilla-

Sanchez et al., 2012, p.123). Using HAVC Transmission Line Analyser and OrCAD as analysis

tools and software respectively, it was apparent that the need to carry out experiments that would

create changes in the understanding of the characteristics was inevitable. In fact, the experiments

were carried out as a result of lack of clear cut characteristics of the high and low voltage

transmission systems. The difference in characteristics will be of great importance to the entire

electrical engineering fraternity as they will make the readers understand the differences

involved in various transmission networks and encourage more research in the study.

Procedure

In order to come up with the most accurate results, a number of procedures were used in

carrying out the experiments. The experiments were carried out using various voltages that gave

various readings in terms of current, frequency, and power factor. The first procedure involved

using experiments that had low voltage as 151V and the high voltage as 159V. The power was

run through the system network under the frequency of 50Hz and a system power factor of zero

(Cotilla-Sanchez et al., 2012. P.67). The network system was monitored keenly and the resultant

Vr, Vy and Vb recorded for the sending end and the receiving end. In addition, the current was

monitored as Iy, Ib and Ir. In order to understand the changes and differences in the voltage and

current within the system network, it was important to note the recorded values at each stage of

the test. Moreover, the test also ensured that the results for sending and receiving ends were

carried out using different lines names and Line (1-2), Line (2-3) and Line (3-1).

The second experiment was also carried out to check on the power cycle of the high and

low voltage distribution network systems with the standard voltage being kept at 150V. The

centre of the cycle was recorded as -445.5835,-45.808 while the radius was given as 471.77. In

addition, the experiment also recorded the radius of the power cycle.

The entire procedure was mainly aimed at ensuring that the results of the experiments

were accurate and able to give clear cut differences between high and low voltage distribution

networks. The procedure also involved carrying out experiments 1 -5 in the attached HAVC

Transmission Line Analyser so as to get the actual differences in figures of the voltages that were

used in the experiments at every stage. Under this procedure, it was important to ensure that the

process was fool proof and all loopholes avoided in order to get the best results.

The next procedure involved examining and analysing real, apparent and reactive power

components in linear and non-linear loads. The process involved use of HAVC Transmission

Line Analyser readings to make comparisons that could help the users in noting the differences

in the low and high voltage distribution systems. In order to understand all the aspects associated

with low and high voltage transmissions, the experiments had to be carried out at different

intervals so as to avoid any errors that might arise during the experiment (Zhai, 2011, p.22). The

third experiment also involved monitoring of the results on the receiving and sending end so as

to get the final results on the differences between the various voltage loads that were used.

It was evident that various changes were noticed during the entire experiment stage from

experiment one to experiment five. In fact, it was the changes that were applied in understanding

the differences that existed between the high and low voltage system networks. As a matter of

fact, the procedure mainly involved use of the same process while changing the values at every

stage of the experiment (Masters, 2013, p.86). Other activities used in the procedure involved

evaluation of the optimum capacitor value for unity / near unity power factor for power

distribution network. This was done by comparing the power factors that were recorded during

different intervals of the voltages used in the experiments. The procedure also involved

conducting a series of simulation assessments in order to help in determining the power factor in

linear and non-linear loads connected at distribution network (Zhai, 2011, p.23). By

incorporating all the above procedures, it was easy to ensure that the system worked out as it was

supposed to and accurate results arrived at.

Materials and methods

The main materials that were used in the entire experiment included HVAC transmission

line analyser that was made up of various sections with each section performing a specific

function. The first section of the machine was the generating station which mainly carried out

power generation activities based on the following features:

Generating Station Healthy(R, Y, B) - Power ONOFF indicate on of 3 phase input

supply.

Generating Unhealthy - Indicates fault condition

From NC1 (VPST-100HV3#F) - Normally closed relay contact.

From NO1 (VPST-100HV3#F) - Normally open relay contact.

A1 - Indicates R phase Current

A2 - Indicates Y phase Current

A3 - Indicates B phase Current

Sending End Voltage (P, N) - Used to measure any one phase voltage

Contactor - Connects or disconnects 3 phase supply with respect to measurement and

protection relay (NO, NC) terminals Isolator Switch - Auxiliary switch of Contactor.

Another part of the equipment that was involved in the experiments was the transmission

line model that had the following features:

The Simulated transmission line is considered for length of 180 km. The line may be used

3 ф, 180 km line or 1

ф,540 km line. The 180 km line is divided into 6 π sections.

Each π section is 30km long. The line inductance is taken for every 30 km and

capacitance for every 15 km. The actual value of line parameters of 400KV transmission line are

0.02978Ω/km,1.06mH/km and 0.0146μ F/km.

The equipment was designed in a way that ensured it carried the required amount of

voltage and carry out the measurement procedures so as to give the most accurate readings.

Furthermore, the equipment help in understanding the readings since it had an automated system.

The third part of the equipment was made up in a way that enabled it to carry out the

voltage test functions by using a number of system design requirements that included the

following aspects:

The power carried by the transmission line is 250W.

Isolator Switch - Auxiliary switch of Contactor

R1, Y1, B1, N1 - Input terminals of transmission line module

R2, Y2, B2, N2 - Input terminals of transmission line module

(R, Y, B) - Power ONOFF indication of 3 phase input supply.

The second equipment was made up of the measurement section that mainly carried out

tasks associated with measuring the voltages and the results got from the experiments.

The conditions that were necessary to ensure accuracy of the results in the experiments

included maintaining optimum current and voltages to the required levels. In addition, the

experiment was carried out under room temperature to avoid any changes in temperature that

could lead to problems in recording and reading the results. The experiment also depended on a

control procedure that used slightly different values to create changes in the entire experiment.

With the aim of noting the differences in characteristics of low and high voltage systems, the

entire procedure was based on the eligibility of the results (Yan & Saha, 2012, p.58).

Findings

Based on the procedures, methods and equipment used in the experiment, it is evident

that the high and low voltage distribution networks have a number of distinct characteristics.

High voltage transmission network systems often have a similar relative frequency, but never

have the same comparative phase as AC power point interchanges. In order to transport the

power that is generated at various generating stations when the network is under low voltages,

the level of materials used in the transmission channels must be able to hold the current without

causing any electric leakages (Short, 2014, p.45). . It is also notable that low voltage power

distribution networks have a number of economical values that help in saving the cost and

requirements of the transmission.

Low voltage power distribution networks are designed in a manner that make them

transport the induced voltages at cheaper costs compared to high voltage systems. At low voltage

level, both the weight and width of insulation in the network used to transmit the voltages have

to be less in the usable alternator. As a result, the transmission of electricity in low voltages cuts

the total costs since the lesser the alternator, the lesser the cost. Besides, it directly minimizes the

total cost and required size of the alternator (Ghosh & Ledwich, 2012, p.34).

On the other hand, the high voltage transmission networks also were seen to have specific

characteristics that made them relatively expensive to use. One of the characteristics is that high

voltage transmission and distribution networks require more advanced transmission cables hence

making it expensive to transport such. In terms of generation of high voltage electricity voltages,

it is of great essence to understand the fact that the generation requires maximum cabling

processes (Mezhiba & Friedman, 2012, p.101).

High-voltage distribution network systems often consist of overhead conductors that are

never covered using any form of insulation. Besides, the conductor material used is often made

of an aluminium metal alloy that gets divided into a number of strands that get reinforced using

steel strands. However, Copper was at times used in the overhead transmission of high voltage

electricity voltages (Pagani & Aiello, 2013). Most systems use aluminium due to its lighter

weight compared to any other usable metals. In addition, aluminium usually yields only slightly

reduced system performance and its price costs much less compared to copper and other

conductors. Overhead conductors that are used in high voltage transmission are often supplied by

various metal and cabling companies that are found worldwide. Improvement of conductor

material and wire shapes is also regularly used with the aim of allowing an increase in capacity

and to modernize several transmission circuits.

Another method that can be used to distribute high voltage charges is the underground

cabling procedure. This involves the transfer of electric power using underground power

cables instead of applying the overhead power lines. The use of underground cables is always

preferred when distributing high voltage charges since it is more secure and is rarely affected by

bad weather conditions. However, the cables have to be insulated thereby making it expensive to

use in high voltage distribution network systems (Richardson, Flynn, & Keane, 2012, p.87).

Conclusion and recommendations

In summary, the entire report has looked into a number of factors associated with low and

high voltage transmission network systems. Using various experiments, the paper has come up

with a number of findings on the characteristics of low and high voltage transmission networks.

In addition, the experiments also gave results that were quite useful in helping compile the

report. Based on the results, procedures, and findings, it is recommended that the generation,

transmission and distribution of electricity using overhead cables when dealing with high

voltages. On the other hand, it is recommended that low voltage electricity be transmitted using

underground cabling.

References

Richardson, P., Flynn, D., & Keane, A. (2012). Optimal charging of electric vehicles in low-

voltage distribution systems. Power Systems, IEEE Transactions on, 27(1), 268-279.

Pagani, G. A., & Aiello, M. (2013). The power grid as a complex network: a survey. Physica A:

Statistical Mechanics and its Applications, 392(11), 2688-2700.

Ghosh, A., & Ledwich, G. (2012). Power quality enhancement using custom power devices.

Springer Science & Business Media.

Short, T. A. (2014). Electric power distribution handbook. CRC press.

Mezhiba, A. V., & Friedman, E. G. (2012). Power distribution networks in high speed integrated

circuits. Springer Science & Business Media.

Yan, R., & Saha, T. K. (2012). Investigation of voltage stability for residential customers due to

high photovoltaic penetrations. Power Systems, IEEE Transactions on, 27(2), 651-662.

Zhai, M. Y. (2011). Transmission characteristics of low-voltage distribution networks in China

under the smart grids environment. Power Delivery, IEEE Transactions on, 26(1), 173-

180.

Masters, G. M. (2013). Renewable and efficient electric power systems. John Wiley & Sons.

Cotilla-Sanchez, E., Hines, P. D., Barrows, C., & Blumsack, S. (2012). Comparing the

topological and electrical structure of the North American electric power

infrastructure. Systems Journal, IEEE, 6(4), 616-626.

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