short duration voltage disturbance identification using rms algorithm in distribution system

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International Journal of Electrical Engineering & Technology (IJEET)

Volume 7, Issue 3, May–June, 2016, pp.01–13, Article ID: IJEET_07_03_001

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ISSN Print: 0976-6545 and ISSN Online: 0976-6553

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SHORT DURATION VOLTAGE

DISTURBANCE IDENTIFICATION USING

RMS ALGORITHM IN DISTRIBUTION

SYSTEM

S. Vijaya Laxmi

Research Scholar, University College of Engg & Tech,

Acharya Nagarjuna University, Andhra Pradesh–India

Dr. P. V. Ramana Rao

Professor & H.O.D/E.E.E, University College of Engg & Tech,

Acharya Nagarjuna University, Andhra Pradesh–India

ABSTRACT

Delivering good quality of power is the main agenda for distribution

system to the loads. But maintain power quality is not so easy due to the load

variations in the system. Sag and swell are the main factors that affect power

quality. In this paper, multiple sag conditions and swell conditions were tested

by producing the condition in different phases of the system. A simple

algorithm called RMS algorithm was developed and tested for the said

conditions. Sag and swell were generated on single phase and multiple phases

for testing the algorithm. The algorithm and the results were obtained using

Matlab.

Key words: RMS, Algorithm, Sag, Swell, Power Quality

Cite this Article: S. Vijaya laxmi and Dr. P. V. Ramana Rao, Short Duration

Voltage Disturbance Identification Using RMS Algorithm in Distribution

System. International Journal of Electrical Engineering & Technology, 7(3),

2016, pp. 01–13.

http://www.iaeme.com/ijeet/issues.asp?JType=IJEET&VType=7&IType=3

1. INTRODUCTION

Power quality determines the quality of electric power to load devices. Maintaining

frequency, voltage and power factor within nominal values makes load to function

properly without stress on the devices. This maintenance of power quality also

reduces the losses in the system increasing the life of the equipment connected. The

paper and also the technology on that are mostly driven by the able quality problems.

S. Vijaya laxmi and Dr. P. V. Ramana Rao


The term power quality [1-4] is very general conception. Broadly, it should be

outlined as provision of voltages and system style in order that user electrical power

will use electric energy from the distribution system successfully, while not

interference on interruption. Power quality is outlined within the IEEE one hundred

Authoritative lexicon of IEEE normal terms because the conception of powering and

grounding instrumentation in a very manner that's appropriate to the operation of that

instrumentality and compatible with the premise wiring system and alternative

connected equipment utilities might want to outline power quality as responsible.

From the able quality market or trade perspective, it's any product or service that's

equipped to users or utilities to live, treat, remedy, educate engineers or forestall

Power Quality problems, issues and connected things. This paper critically discusses

concerning the able quality of power issues, problems and connected standards,

assessment of power quality problems and strategies for its correction [5-8].

Power quality issues like transients, sags, swells and alternative to the curving

wave shape of the availability voltage have an effect on the performance of those

instrumentality items. Voltage sags and swell in an electrical grid aren't forever

attainable to avoid as a result of the finite clearing time of the faults that cause the

voltage sags, swells and therefore the propagation of sags and swells from the

transmission and distribution systems to the low-tension hundreds [9-10]. Voltage

sags and swells are the common reasons for interruption in production plants and for

end instrumentality malfunctions generally, specifically, in economical identification

will cause disruption and vital prices attributable to loss of production. One solution

to the present downside is to create the instrumentality itself additional tolerant to

sags, either by intelligent management or by storing energy within the instrumentality.

The main objective of the paper is to generate sag and swell in different phases of

the system and analyze them. A simple RMS algorithm was generated to analyze the

condition of the system, whether the sag/swell exists in the system. If yes, in which

phase of the system. This algorithm developed is very simple.

2. POWER QUALITY DISTURBANCES

Figure 1 Power Quality Issues

Short Duration Voltage Disturbance Identification Using RMS Algorithm In Distribution

System


Figure 2 Power System Network that can Produce Sag/Swell

Power quality issues are shown diagrammatically in figure 1 and figure 2 shows

the power system network that creates sag/swell for observation and analysis. Power

system disturbances can occur as general phenomenon and these disturbances are of

two types-long term duration and short duration disturbances. Long duration

disturbances are the disturbances that persist for the duration more than 1 minute. If

the duration of the fault is less than 1 minute, the fault is termed as short duration

fault. Long duration voltage raise is called over voltage and short duration voltage

raise is called swell. Similarly, long duration voltage drop is termed as under-voltage

and short duration voltage drop is termed as sag. Sag is a general phenomenon that

occurs due to energizing heavy loads or starting of large motors. Swell is another kind

which might be produced due to energizing capacitor banks or sudden release in

loads.

Voltage sag might cause poor efficiency and decreases the life time of the device

connected. Swell might cause the device to be damaged. This causes the power

system to poor power quality. Poor power quality can cause unexpected power supply

failures, equipment failure or malfunctioning, equipment overheating and might lead

to reduction in lifetime of the device, increased system losses and production of EMI.

Long term sustained voltage variation if when the supply voltage is zero for more

than 1 minute, the long term voltage disturbance is termed as sustained interruption.

This sustained interruption cannot be cleared automatically and needs human

intervention. Short term variations can be designated as instantaneous, momentary or

temporary. Instantaneous variations in voltage vary from time duration 0-30 cycles,

momentary variations vary from 30 cycles to 30 seconds and temporary variations

vary from 30 seconds to 1 minute in time. Sag is termed as the variation in voltage

from 90% to 10% of its final value for short duration. Swell is raise in voltage value

from 110% to 180% if its final value. Interruption occurs when voltage or current falls

to 0.1 pu in less than 1 minute. When current commutation occurs in power electronic

devices, a periodic voltage disturbance is caused which is called notching.

Instantaneous rapid change in voltage is called transient. Depending on the type of

transient nature, transients are classified into two types- oscillatory and impulsive.

Harmonics are power frequency disturbances having frequency which is integral

multiples of power frequency. These power frequency disturbances can be

decomposed to sum of fundamental quantity and harmonic content. These are mainly

produced due to the presence of non-linear loads in the system.



3. RMS ALGORITHM

A simple algorithm called RMS algorithm was developed to detect the sag/swell in

the system. Sag or swell can cause unusual operation of the system. Thus the sag and

swell should be avoided. But in the power system due to load variations these sag and

swell cannot be avoided and these are very general phenomenon as per the power

system is concerned. But measures should be taken to reduce the sag/swell. To take

any action the first step needed is to identify the parameter. Here the identification of

sag/swell is much important to take necessary action against to reduce the quantity of

sag/swell and bring the voltage level to nominal value. Also the identification is

required in how many phases sag/swell are present in the system. So a simple RMS

algorithm was developed for identification.

Table I RMS Algorithm test cases for identification of sag/swell

Voltage Sag Voltage Swell

Output Phase -

A

Phase -

B

Phase -

C

Phase -

A

Phase -

B

Phase –

C

Case 1 0 0 0 0 0 0 No sag exists

No swell exists

Case 2 1 0 0 0 0 0 Sag exists in 1 phase

Case 3 0 0 0 1 0 0 Swell exists in 1 phase

Case 4 1 1 0 0 0 0 Sag exists in 2 phases

Case 5 0 0 0 1 1 0 Swell exists in 2 phases

Case 6 1 1 1 0 0 0 Sag exists in 3 phases

Case 7 0 0 0 1 1 1 Swell exists in 3 phases


Swell exists in 1 phase

















The test conditions were considered as 1 for ON and 0 for OFF. As shown in table

1, the sag and swell were generated for different phases of the power system. Fourier

analysis provides a set of mathematical tools which can be used to break down a

signal into its various magnitude components.


System


The identified voltage magnitude from the algorithm will send to the MATLAB

file for evaluation of voltage magnitudes for the given reference signal. In Matlab file

multiple conditional operators have been included for identification type of fault. In

the Matlab file, the identified voltages have been compared to the specified reference

voltages with the use of logical operators, if the identified voltage is less the specified

voltage given as fault identified as sag, if it is greater it is considered as swell.

If the Sag/Swell have been identified in the pre process then it have to identify

whether symmetrical fault or asymmetrical fault. Analysis for identification of fault in

the phases has taken here.The end of the identification process is displaying the

results, these results can further utilized for fault reducing devices a like DVR,

SFCL...Etc.

4. MATLAB RESULT ANALYSIS

Matlab results were obtained by considering different cases producing sag and swell

in different phases of power system.

Case 1: analysis when no sag and no swell are present in the system

Figure 3 Result showing no sag/swell present in the system

Case 2: analysis when only sag exists in 1 phase of the system

Figure 4 result showing sag present in 1 phase of the system



Case 3: analysis when only swell exists in 1 phase of the system

Figure 5 Result showing swell present in 1 phase of the system

Case 4: analysis when sag exists in 2 phase of the system

Figure 6 result showing sag present in 2 phase of the system

Case 5: analysis when swell exists in 2 phase of the system



System


Case 6: analysis when only sag exists in 3 phase of the system

Figure 8 Result showing sag present in 3 phase of the system

Case 7: analysis when swell exists in 3 phase of the system


Figure 3 shows the result window noting that no sag or no swell is present in the

system. Figure 4 shows that sag is present in 1 phase of the system while no swell is

present in the system. Figure 5 shows the swell present in 1 phase with no sag in the

system. Figure 6 shows sag present in 2 phases with no swell and figure 7 shows the

swell in 2 phases with no sag. Figure 8 shows sag present in 3 phases with no swell

while figure 9 shows swell in 3 phases of the system with no sag.

Case 8: analysis when sag exists in 1 phase and swell in 1 phase of the system



Figure 10 Result showing sag present in 1 phase and swell exists in 1 phase of the system

Case 9: analysis when sag exists in 1 phase and swell in 2 phases of the system

Figure 11 Result showing sag present in 1 phase and swell exists in 2 phases of the system

Case 10: analysis when sag exists in 1 phase and swell in 3phases of the system


Figure 10 shows the window noting sag is present in 1 phase with swell also in 1

phase of the system. Figure 11 shows sag present in 1 phase with swell in 2 phases of

the system. Figure 12 shows the presence of sag in 1 phase with swell in 3 phases of

the system.


System


Case 11: analysis when sag exists in 2 phases and swells in 1 phase of the system


Case 12: analysis when sag exists in 2 phases and swells in 2 phases of the system






Figure 13 shows the window noting sag is present in 2 phases with swell also in 1

phase of the system. Figure 14 shows sag present in 2 phases with swell in 2 phases of

the system. Figure 15 shows the presence of sag in 2 phases with swell in 3 phases of

the system.

Case 14: analysis when only sag exists in 3 phases and swells in 1 phase of the

system

Figure 16 Result showing sag present in 3 phases and swell exists in 1 phase of the system

Case 15: Analysis when only sag exists in 3 phases and swells in 2 phases of the

system


System





Figure 16 shows the window noting sag is present in 3 phases with swell also in 1

phase of the system. Figure 17 shows sag present in 3 phases with swell in 2 phases of

the system. Figure 18 shows the presence of sag in 3 phases with swell in 3 phases of

the system.

5. CONCLUSION

A Novel sag/swell detection algorithm has been proposed and compared and

implemented by using Matlab algorithms. The simulation study of algorithm has been

presented in this paper for extracting voltage component of source voltage under

sag/swell conditions. The function of in Matlab is a powerful tool for doing that even

with noisy signals. The identification process is very accurate. The simulation results

shows that sag/swell have been identified with what phase swell or sag exists. This

algorithm explained is very simple and can effectively detect the presence of

sag/swell in the system. Different cases have been considered for the production of

sag/swell and the results were shown.

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System


AUTHORS PROFILE

S.VIJAYA LAXMI was born in India in 1975; She received the

B. Tech degree in Electrical and Electronics Engineering from

V.R.S. Engineering College, Vijayawada, Nagarjuna University

in 1997 and M. Tech degree from S.V.U College of Engineering

in 2005 S.V.U Tirupati and Andra Pradesh, India. Currently she

is pursuing Ph.D in Electrical Engineering, as a Research

Scholar in University college of Engineering and Technology,

Acharya Nagarjuna University, Andhra Pradesh India. Her areas

of Interest are Voltage Quality Identification and Mitigation in

Power systems and Application of Intelligent control techniques

to Power systems.

P.V. RAMANA RAO was born in India in 1946; He received

the B. Tech degree in Electrical and Electronics Engineering

from IIT Madras, India in 1967 and M. Tech degree from IIT

Kharagpur, India in 1969. He received Ph. D from R.E.C

Warangal in 1980. Total teaching experience 41 years at NIT

Warangal out of which 12 years as Professor of Electrical

Department. Currently Professor of Electrical Department in

University college of Engineering and Technology, Acharya

Nagarjuna University, Andhra Pradesh, India. His fields of

interests are Power system operation and control, Power System

Stability, HVDC and FACTS, Power System Protection,

Application of DSP techniques and Application of Intelligent

control techniques to Power systems.