CALIFORNIA STATE UNIVERSITY, NORTHRIDGE DISTANCE …

CALIFORNIA STATE UNIVERSITY, NORTHRIDGE

DISTANCE AND OVERCURRENT PROTECTION

OF FEEDERS AT DISTRIBUTION SUBSTATION

A graduate project submitted in partial fulfillment of the requirements

For the degree of Master of Science in

Electrical Engineering

By

Youssef Pierre Chedid

December 2013

ii

The graduate project of Youssef Pierre Chedid is approved by:

_________________________________ ___________________

Professor Xiyi Hang Date

_________________________________ __________________

Professor Benjamin Mallard Date

_________________________________ _________________

Professor Bruno Osorno, Chair Date

California State University, Northridge

iii

Table of Contents

Signature Page…………………………………………………………………………….ii

List of Figures……………………………………………………………………..…...…iv

List of Tables……………………………………………………………………..…….…v

Abstract………………………………………………………………………………...…vi

1. Introduction…………………………………………………………………….....1

2. Background Theory

2.1.Microprocessor vs. Electromechanical Relays……………………………..…2

2.2.Overcurrent Protection………………………………………………………..5

2.3.TCC Curves…………………………………………………………………...6

2.4.Directional Overcurrent Protection………………………………………..…10

2.5.Distance Protection………………………………………………………..…14

2.6.Comparison and Selection…………………………………………………...16

2.7.Fuses…………………………………………………………………………17

2.8.Fault Location…………………………………………………………….…18

3. System Application

3.1.Entire GUI……………………………………………………….……….….21

3.2.GUI - Windows…………………………………………………………..….22

3.3.Substation Design…………………………………………………………....27

3.4.GUI - Overcurrent Example……………………………………………….…29

3.5.GUI – Distance Protection Example…………………………………………32

3.6.GUI – Fault Location Example……………………………………………....34

4. Conclusion…………………………………………………………………...…..36

References………………………………………………………………………………..37

Appendix A. Fuse Curves Data …………………………………………………………38

Appendix B. Partial GUI Code ……………………………………….............................39

iv

List of Figures

Figure 2.11 - Westing House electromechanical time overcurrent relay………………….3

Figure 2.12 - SEL-751A Feeder Relay…………………………………………………....4

Figure 2.13 - SEL-351 Overcurrent Relay………………………………………………...4

Figure 2.31 - U2 Curve (TD: 0.5 to 15)…………………………………………………...8

Figure 2.32 - U3 Curve (TD: 0.5 to 15)…………………………………………………...9

Figure 2.33 - U4 Curve (TD: 0.5 to 15)………………………………………………….10

Figure 2.41 - Single Source System with Relay…………………………………………12

Figure 2.42 - Two Source System……………………………………………………….13

Figure 2.51 - Distance Protection example………………………………………………14

Figure 2.71 - S&C Standard Speed………………………………………………………18

Figure 3.11 - Entire GUI…………………………………………………………………21

Figure 3.21 - GUI-Window 1…………………………………………………………….22




Figure 3.25 - GUI-Window 5……………………………………………………….........26

Figure 3.26 - GUI-Window 6……………………………………………………….........27

Figure 3.31 - Operating Single Line of 12kV Distribution Substation…………………..28

Figure 3.41 - Main and Backup relay coordination……………………………………...30

Figure 3.42 - AcSELerator Software (SEL-351)………………………………………...31

Figure 3.51 - GUI_ Zone Protection……………………………………………………..33

Figure 3.52 - AcSELerator Software (SEL-421)………………………………………...34

Figure 3.61 - Fault Location using Algorithm I………………………………………….35

Figure 3.62 - Fault Location using Algorithm II………………………………………...35

v

List of Tables

Table 2.21 - Overcurrent Protection Elements……………………………………………5

Table 2.51 - SEL Zone Protection……………………………………………………….15

Table 2.71 - Fuse Manufacturers and Types……………………………………………..17

Table A1.1 - S&C Standard Curves Data Points………………………………………...38

vi

ABSTRACT

DISTANCE AND OVERCURRENT PROTECTION

OF FEEDERS AT DISTRIBUTION SUBSTATION

By

Youssef Pierre Chedid

Master of Science in Electrical Engineering

The “Distance and Overcurrent Protection of Feeders at Distribution Substation” report

will discuss protection of distribution feeders at a substation. The paper will discuss the

three types of protection that can be implemented on a distribution feeder. Also, this

paper presents an in depth analysis and comparison of the overcurrent, directional

overcurrent, and distance protection. Using AutoCAD, a substation’s operating single

line was constructed as an example of an actual substation. Also, a “Protection

Assistance” graphical User Interface (GUI) was created to assist in feeder protection. The

GUI will include SEL overcurrent time-current curves, overcurrent relay coordination,

fuse relay coordination, mho graph for distance protection, and fault location using

Wavelet Transform.

1

1. Introduction

Distribution Feeders are a crucial part of the electric grid. They deliver power from the

transmission line to the customers. Applying proper protection on distribution feeders is

critical since a small fault (without proper protection) can affect the whole feeder and

cause a huge outage. Feeders usually exist in a distribution substation, and a substation

usually contains approximately 5 to 10 feeders. In newer substations, feeders are usually

rated at 12kV but 4kV feeders might exist. Protection on feeders at substation exists

through relays, usually two relays per feeder; the first is the main protection and the other

acts as a backup. Usually microprocessor relays are used but electromechanical and solid

state relays still exist.

The three types of protection that can be applied to feeders are overcurrent protection,

directional overcurrent protection, and distance protection. The overcurrent protection is

much more applicable in the industry than the directional and distance protection. In

situations where a distributed generator (DG) is present, power is reversed at some

instances. Since overcurrent protection protects from faults in one direction, it cannot be

implemented in these circumstances. In such a situation directional overcurrent or

distance protection would be the ideal protection. Directional overcurrent detects fault in

forward and reverse directions and distance protection uses zones to protect the feeder.

2

2. Background Theory

2.1 Microprocessor vs. Electromechanical Relays

Overcurrent Protection can be applied in microprocessor relays and electromechanical

relays. The theory behind overcurrent protection is when extremely large current is found

in the electric circuit caused by electric grid faults. The excessive current can be caused

by single line to ground faults, double line to ground faults, line to line faults, and three

phase faults. [4] In protection there are two types of overcurrent protection, instantaneous

overcurrent protection (ANSI Device No. 50) and time overcurrent protection (ANSI

Device No. 51). Overcurrent protection is used in many equipment protection

applications. Some of these applications are:

Feeder protection and backup feeder protection

Transmission/Sub-transmission lines backup protection

Transformer backup protection

Bus Tie, Bus Sectionalizer, & Capacitor Banks

Generators and motors

Originally overcurrent protection was implemented in electromechanical relays. Some

manufacturer’s that produce electromechanical relay are General Electric, ABB, and

Westing House. Figure 2.11, shown below displays a “General Electric”

electromechanical relay implementing phase time overcurrent.

3

Figure 2.11 - Westing House electromechanical time overcurrent relay.

Three electromechanical relays, one for each phase, are displayed in figure 2.11 above.

Their primary job is to provide backup protection to the transformer bank at this

particular substation. Electromechanical relays are very reliable and last a long time but

the only disadvantage is that they are very inefficient. Each electromechanical relays

have only one protection element per relay. Some of the elements are phase time

overcurrent, ground time overcurrent, Differential, pilot wire, and many other functions.

On the other hand, the invention of microprocessor relays made protection much more

effective. In a microprocessor relay, one relay can implement multiple functions. For

example, instead of having six electromechanical relays to function as primary and

backup protection for a transformer bank, an engineer can have two relays that implement

the same job. Some manufacturer’s that produce microprocessor relay are “Schweitzer

Engineering Laboratories (SEL)”, “ABB”, and “General Electric”.

4

Figure 2.12 and figure 2.13 below displays some common microprocessor overcurrent

relays.

Figure 2.12 – SEL-751A Feeder Relay

Figure 2.13 – SEL-351 Overcurrent Relay

5

2.2 Overcurrent Protection

The Overcurrent Protection inside the SEL relays or any microprocessor relay consist of

different elements. Some of these elements are described in table 2.21 below.

Table 2.21- Overcurrent Protection Elements

Through this entire report, 50G, 50P, 51G, and 51P are the elements which will be

applied the most. 50G and 50P refer to instantaneous tripping of the circuit breaker

instead of waiting a specific time for the tripping. 51G and 51P refer to tripping of the

circuit breaker depending on time set by the engineer. Unlike instantaneous, time

overcurrent protection depend on many factors. Some of these factors are:

Time Dial

Secondary current

Time-Current curves

- U.S. Curves

- IEC Curves

6

Current Transformer

Maximum fault Current

Tripping time (Tp)

Reset time (TR)

2.3 TCC Curves

To further illustrate on the time-current curves, five different curves exist for each of the

US curves and the IEC curves. For US curves, the five curves are Moderately Inverse

(U1), Inverse (U2), Very Inverse (U3), Extremely Inverse (U4), and Short Time Inverse

(U5). While for the IEC curves, there five curves constitute of Moderately Inverse (C1),

Inverse (C2), Very Inverse (C3), Extremely Inverse (C4), and Short Time Inverse (C5).

The following equations displayed below are the US and IEC curve equations.

(

)

(

)

(

)

(

)

(

)

(

)

7

(

)

(

)

(

)

(

)

The most commonly used curves are the U2, U3, and U4 curves. Figure 2.31, 2.32, and

2.33 best describe the commonly used curves for different time-dials.

8

Figure 2.31 – U2 Curve (TD: 0.5 to 15) [2]

9


As shown in figure 2.32 above, different curves are displayed for varying time dial. “The

tripping time duration of the overcurrent relay (SEL) can vary due to relay type, time-dial

setting (TDS) and magnitude fault currents.”[3] The U3 curve will be used in a

coordination example in the application section. In addition, U4 curve which is displayed

in figure 2.33 below will also be used in the upcoming coordination example of a feeder

protection.

10


2.4 Directional Overcurrent Protection

The current and voltage phases are used to determine relay direction to a fault in a typical

directional overcurrent relay. This task is accomplished using different methods.

Directional overcurrent relay use the ANSI device number “67”. “The old solid state and

electromechanical relay, detects the direction where the fault occurred by analyzing and

comparing the phase angle relationship of phase voltages to phase currents. Considering

watt phase flow (ANSI “32”), the terminology would be that if voltage- neutral phase is

11

in phase with current phase (0°, ±90°), then flow of power on that particular phase is

indicated as reverse (or forward, depending on one’s location).[1]

The second approach for directional overcurrent relays is symmetrical components. Many

modern microprocessor relays use symmetrical component’s angular relationship

voltages and currents and the resultant angular nature of Z0, Z1, and Z2 as calculated

from Vp/Ip to determine the fault’s direction. The impedances listed above are

manipulated to create three directional methodologies, 67Zero, 67Positive, and

67Negative that are used in relay logic in various ways by each manufacturer.[1] The

following equations illustrate the symmetrical component method of calculating for the

directional overcurrent variables.

[

] [

] [

] [

]

[

] [

] [

] [

]

[

] [

] [

] [

]

12

Figure 2.41 – Single Source System with Relay

[

] [

]

([

] [

]) [

]

[

] [

] [

] [

]

13

Figure 2.42 – Two Source System

( ) ( )

( ) ( )

14

2.5 Distance Protection

Distance protection is a crucial type of protection that varies from overcurrent protection.

It occupies the ANSI number of 21. Selectivity and fast operation is why some electrical

engineers prefer distance relay over overcurrent relays. Distance relays are generally

implemented for transmission line protection, sub-transmission lines backup protection,

and primary phase-fault protection. Overcurrent relays are commonly used for all type of

fault primary and back-up protection, but in today’s market there is a huge demand

toward distance relays for phase to ground protection.[5]

The basic distance protection is based on Zones. Usually the first zone protects 80% of

the electric circuit, while the second zone protects 120% of the circuit (Table 2). The

third zone is equal to the second zone and it is upside down. The SEL relay design

implements up to five zones. These values can vary depending on the design but they are

used as default values for SEL relays that implement distance protection. The reason for

using 80% for the first zone is to avoid nuisance trips. The extra 20% that is implemented

on zone 2 is used to fasten protection towards the end of the line. The third zone is upside

down to protect the line from reverse current.

Figure 2.51 – Distance Protection example

15

Figure 2.51 above displays an example of a three zone system. In the example above, two

transmission lines exist and three protective zones are implementing the distance

protection. As displayed, the first zone protects between 50 to 100 percent of the first

transmission line while the second zone protects the first line and 0 to 50 percent of the

second line. The third zone protects both transmission line and little extra. This example

is designed in a different manner than the distance SEL relays.

In general distance protection is implemented on transmission lines but is it possible to

implement such protection on feeders? Depending on the protection engineer’s design,

yes it is possible but is it more efficient? Based on the measured impedance, the

advantage of Distance protection is that it can differentiate between faults occurring in

different sections of the electric circuit. Basically, the distance relay compares the voltage

at the relay to the current detected from a fault. The way to adjust the distance protection

is by adjusting the positive sequence (Z1) impedance of the transmission line. As soon as

the fault occurs in any part of the transmission line, the distance relay separates the line

into two sections. Automatically, the first section is from distance relay to the location

where the fault occurred. The fault impedance is proportional to the distance protection

positive sequence impedance. Hence, an approximation of the fault location can be found

by using the impedance of the relay location.[3]

Zones Percent Protection (SEL) Direction

Zone 1 80% Forward

Zone 2 120% Forward

Zone 3 120% Reverse

Zone 4 N/A Forward

Zone 5 N/A Forward

Table 2.51 – SEL Zone Protection

16

2.6 Comparison and Selection

After analyzing the three types of protection, it is time to analyze feeder protection. All

three types of protections can be implemented in feeder protection. The most common

feeder protection is overcurrent protection. One problem with overcurrent protection is

that it is a one way protection, which means that if power reversed direction the feeder

would be unprotected. Power can reverse direction if a distributed generator (DG) is

connected to the grid. In order to provide overcurrent feeder protection even when power

is reversed, directional overcurrent is implemented. One disadvantage of directional

overcurrent protection is the settings are too complicated. As shown from equation X to

equation Y, directional overcurrent equations are much more involved with multiple

variables to account for. If overcurrent protection is not to be implemented, distance

protection can be used. Distance protection will protect a given feeder or line regardless

of the direction of the power. At a renewable energy source, distance protection can be

implemented to feeders since it is common to have a DG connected to the grid.

17

2.7 Fuses

Fuses are essential part of feeder protection; they are usually placed to interrupt faults

without tripping the breaker. A fuse is basically a low value resistor which works as a

device that melts when the current rating exceeds the fuse rating. It is commonly used

downstream in a distribution feeder. One of the advantages of fuses are that they protect

the feeder from a huge outage [6]

There several types of fuses that are commonly used, some of these fuses are:

Brush Chance Cooper

Kearney

Cooper

McGraw

Cooper

RTE

GE S&C Southern

States

Type 1 K K K D 1406B 9F57 Coor AF-UF

Type 2 MS KS K-silver 1551B K AK-UK

Type 3 SloFast QA K-Tin 1555B N AT-UT

Type 4 T T S-Tin QR AM-M-UM

Type 5 H X T-Tin Sta AH(5-25kV)

Type 6 N (200) C-Tin T UH(5-15kV)

Type 7 EH DR

Type 8 EK-Tin KSR

Type 9 ET-Tin Cap

Type10 N-Tin

Type11 H

Table 2.71- Fuse Manufacturers and Types

The type of fuse used in this report is the S&C Standard Speed fuses. Figure 10 below

displays the total clearing time-current characteristic curves.

18

Figure 2.71 – S&C Standard Speed

The table for the time current graph drawn in figure 2.71 is displayed in the appendix.

Also these TCC curves are used in the Graphical User Interface in the application section.

2.8 Fault Location

Fault location is a crucial aspect of protection applications. It is difficult to pinpoint or

locate the exact location of a fault in a power circuit. “Most notable power signals include

a combination of impulse-like events such as spikes and transients for which Short Time-

Fourier Transform (STFT) and Fourier Transform (FT) and other conventional time-

19

frequency methods are not as suitable for analysis.” [2] “The Wavelet Transform (WT) is

one of the best ways for analyzing transient signals.”[2] Therefore the Wavelet analysis

that is based on two Algorithms is the best solution for accurate fault location.

Fault location is a crucial aspect in protection. With feeders as long as 10 miles, finding

the exact location of the fault makes life easier for the protection engineer. The fourth

window of the “Feeder Distribution GUI” will calculate the exact fault location of a given

line from the source to the exact location. It gives the users two options in which both

calculate the fault location but one is a little more accurate than the other. Algorithm II is

more accurate than Algorithm I, but it requires more information. The equation for

Algorithm I & Algorithm II respectively are:

(

)

Where;

d= distance of fault from source to fault location.

L= Transmission line length.

= The time from fault distance to the left relay.

= The time from fault distance to the right relay.

v= Wave speed calculated according to pre-measurements

20

= The difference in the main and reflected waves for the relay left of fault.

= The difference in the main and reflected waves for the relay right of fault.

A simple example will solved using hand calculation to illustrate the difference between

the two methods and the level of accuracy.

21

3. System Application

3.1 Entire GUI

Using MATLAB, a Graphical User Interface was created to help set up the system’s

feeder protection. Even though this GUI is created for Feeder Protection assistance, it can

be used for other applications too. For that reason, the GUI created is called “Protection

Assistance”. Figure 3.11 below displays the entire GUI

Figure 3.11 – Entire GUI

22

3.2 GUI - Windows

“Protection Assistance” GUI is consist of six main windows. The first three windows

help assist with Overcurrent relay coordination. The Fourth window is involved in

Distance Protection while the fifth window assists the user with fault location using the

WV method. The sixth window is the axes window which allows the user to view the

plots generated by the other windows.

Window 1 is displayed in figure 3.21 below. This Window is a “Given Window” which

means it is used to input the necessary data in order of other windows to display the

results.

Figure 3.21 – GUI-Window 1

Window 1 allows the user to choose the number of relays to be coordinated. First the user

enters the Current Transformer (CT) ratio for up to three relays. Then the user enters the

relative information associated with the relays. Also the user must enter the Time dial

23

(TD) and the secondary current (Is) associated with the relay used. All the symbols

followed by “(1)” are associated with the first relays used. Also, “(2)” and “(3)” are

associated with the second and third relay respectively. After providing the necessary

information, the user has to select the time-current characteristic curve to be used for

phase and ground at each relay selected. The curves that are available for selection are the

U.S. curves and the I.E.C. curves. A code was written for each “curve selection” pop up

menu in order to display the graph associated with the curve right after the curve type is

selected.

This process will only display the curves related to a specific design but in order to

coordinate the relays together couple of additional steps have to be followed. The first

step is to run the short circuit analysis on a separate program and display the maximum

fault “Imax” in the edit box in window 1. Clicking the push bottom “Calc (Tp)” located

next to “Imax” will calculate the Tripping time for each relay in Window 3 displayed in

figure 3.23. The last edit box in window 1 is the coordination “Time Interval (T.I.)”. The

“Default” push bottom, located next to the “Time Interval” edit box, is used to input a

default value of 0.25 for the time interval.

Figure 3.22 below displays window 2 of the GUI “Fuse Selection”. This window is used

for the user to select the number of fuses to be coordinated with the relay and the fuse

rating.

24

Figure 3.22 - GUI-Window 2

Window 2 allows the user to integrate in the design up to three fuses. A code was written

for each “Fuse selection” pop up menu in order to display the graph associated with the

rated fuse. The SMU Fuse Units-S&C Standard Speed time overcurrent characteristic

curves were used with the rating varying from 10E to 250E. Coordination between the

relays selected in window 1 and the fuses selected in window 2 will be done in window 3.

Figure 3.23 below displays window 3 of the GUI which is responsible for coordination,

where it’s between two relays or fuse and a relay.


Window 3 displays the Tripping time for phase and ground time overcurrent which will

in turn assist the GUI in the coordination calculations. This window is split into two mini

windows, the left side and the right side. The left side calculates the Relay-Fuse

coordination while the right side calculates the Relay-Relay Coordination. The left

window coordinates between each of the fuses and each relay if used in design. The right

window coordinates between all three relays. The edit box for each coordination box will

25

display a “YES” or “NO” respond upon pushing the “Coordinate (F)” or “Coordinate

(R)” push bottoms depending on application.

Figure 3.24 below displays window 4 of the GUI which is responsible for distance

protection.


Window 4 allows the user to input the Current Transformer, Potential Transformer and

the primary impedance of the line in a given electric circuit. After that, the user has the

choice to input up to five zones of protection in the distance relay. Three of these zones

have a “SEL” push bottom which will display the default Zone values suggested by a

Schweitzer Electric Laboratories (SEL) distance relay. After the user inputs the Zone

values, the number of zones used should be selected from the pop up menu under “Zone

Selection”. After the number of zones is selected, a mho graph will be displayed in

window 6.

Figure 3.25 below displays window 5 of the GUI which is responsible for fault location

using the wavelet Transform.

26

Figure 3.25 – GUI-Window 5

Window 5 allows the user to calculate for the fault location from the source to the fault

location using two different algorithms. First the user has to input the length of the line

(L) in km, the time from the left relay to the fault (t1) in ms, and the time from the right

relay to the fault (t2) in ms. Then depending on which algorithm the user decides to use,

the user have to insert other variables. If Algorithm I to be used, the user needs to insert a

value for the Wave speed calculated according to pre-measurements (v). Otherwise, if

Algorithm II to be used, the user needs to insert a value for the difference in the main and

reflected waves for the relay left and right of the fault ( respectively). If the

values for all the variables are known, then both methods can be implemented. After

choosing which algorithm to implement from the pop up menu, the distance of the fault

will be displayed in the “Fault Location” edit box in km.

Figure 3.26 below displays the axes where all the plots from different windows will be

displayed.

27


Window 6 will display the time current curve characteristics for the relays and fuses from

windows 1 & 2 and the mho graph from window 4. The “Reset” push bottom will clear

the graph from any plots in order to prevent confusion when the user decides to re-plot or

change design.

3.3 Substation Design

After explaining the graphical user interface windows and their basic functions, an

example will be implemented to further explain the benefit of the GUI. A 12kV

distribution substation is designed to supply a certain area with power. Figure 3.31 below

displays the operating single line for the substation.

28

Figure 3.31 – Operating Single Line of 12kV Distribution Substation

The operating single line of Substation “matadors” is drawn using AutoCAD. Within

figure 31, a legend exists to explain what each symbol drawn refers to. For example, a

square box is a circuit breaker, a circle is a relay, an arrow pointing downwards is a

feeder, and so on. In the single line, the substation receives 34.65kV from the Switching

Station through the CSUN-Utility line 1 to the 34kV Bus. The CSUN-Utility line 2 exists

as a backup for the first line. Then the power leaves the 34kV line to Transformer Bank 1

where it is converted to 12kV. Transformer 2 and 3 exist as backup to the first

transformer. After that, power moves from the low side transformer bank to the 12.47kV

29

operating bus. Then power transfers from the operating bus to the feeders. The transfer

bus exists as backup to the operating bus. After the feeders, power is sent downstream to

supply residential and businesses.

3.4 GUI - Overcurrent Example

As displayed on the single lines, the protection on the feeders consists of two relays

connected to the circuit breaker. The main relay is SEL-351 while the backup relay is

SEL-501. The functions used as protection on the main relay (SEL-351) are 50, 50P,

50G, 79, and 81.The functions used for protection on the backup relay (SEL-501) are

51G and 51P. One problem exists with the current protection which is coordination

between the main relay and the backup relays. The GUI designed in this section will

solve the coordination problem. Figure 3.41 below displays a design set for the two relays

and the coordination applied on them. Many solutions can exist for these relays as long as

they coordinate with each other.

30

Figure 3.41- Main and Backup relay coordination

As displayed in window 1, the given CT is 400:5 so the CT ratio is 80 for both relays.

The design for the main relay consists of time dial of 3 and secondary current is set at 7A

which sets the minimum pickup current at 560A.The curve chosen is the extremely

inverse (U4) curve. The design for the backup relay consists of time dial of 3 and

secondary current is set at 10A which makes the minimum pickup current at 300A. The

curve chosen is the inverse curve (U2). After running the short circuit analysis using

31

computer software, the maximum fault was found to be 20,000A so Imax in window 1

was set to 20,000. The curves for the two relays are displayed in window 6, the blue is

the main relay and the green is the backup relay. After plotting the graphs, for

coordination purposes the time interval (window 1) was set to 0.25. Clicking on

“Coordinate(R)” bottom in window 3 displayed a “YES” which means both relays are

coordinated. If “NO” was displayed that means both relays were not coordinated and the

designed to be altered.

After having both relays coordinated, the next step would be to input the data used in the

SEL software “AcSELerator”.

Figure 3.42 - AcSELerator Software (SEL-351)

32

Figure 12 displays a quick view of the acSELerator software. As shown in figure 12, the

time dial, secondary current, and the curve type are displayed in Phase TOC in

acSELerator.

3.5 GUI - Distance Protection Example

Draw the mho graph of the distance protection of a feeder. Implement three zones and

use the SEL Default zone percentages for the zone values (Zone 1: 80%, Zone 2: 120%;

Zone 3:120%). Use a CT value of 250:5 and a PT of 69000:115. The feeder’s primary

impedance is set to 2+j20. Using equations 2.32 and 2.33:

After applying hand calculations to the zone protection example above, the same example

was simulated using the window 4 from the GUI.

33

Figure 3.51 – GUI_ Zone Protection

Figure 3.51 below displays the GUI using the Zone protection example data. The mho

graph is plotted in window 6 to resemble the given data.

A simple example will solved using hand calculation to illustrate the difference between

the two fault location methods and the level of accuracy.

After implementing the following zone protection example into the GUI, the data will be

applied to the SEL-421 using the acSELerator software as shown in figure 3.52.

34

Figure 3.52 – AcSELerator Software (SEL-421)

3.6 GUI - Fault Location Example

For a 200km transmission line, find the fault location on the transmission line if the time

from the fault to the left and right relay is 2.0ms and 1.5ms respectively? The wave speed

calculated according to pre-measurements is 2.96*10^8; while for the uncalculated wave

speed delta1 is 0.65msand delta2 is 0.75ms.

First Algorithm:

( )

35

Therefore, the fault location using the second algorithm is 174km.

Second Algorithm:

(

)

(

( ))

Therefore, the fault location using the second algorithm is 171km. The second algorithm

is much more accurate than the first because more variables are involved.

Figure 3.61 – Fault Location using Algorithm I

Figure 3.62 – Fault Location using Algorithm II

Using window 5 from the GUI, the same example was solved and figure 3.61 and 3.62

display the results using both methods. The result from the GUI matched the results from

the hand calculations.

36

4. Conclusion

The paper discussed the three types of protection that can be implemented on a

distribution feeder.

This paper presented an in depth analysis and comparison of the overcurrent,

directional overcurrent, and distance protection.

In addition, this paper presented two new fault location detection algorithms.

The most commonly used protection on feeders is Overcurrent protection.

Schweitzer Engineering Laboratories relays and time-current curves (TCC) were

used in this report.

An operating single line diagram of a fictional substation was drawn using

AutoCAD to display feeder location in a substation.

A Graphical User Interface “Protection Assistance” was created using MATLAB

to help assist with Overcurrent and distance protection.

Coordination between the main relay and backup relay was implemented using

TCC curves in the GUI

Also, the GUI included a window to assist in fault location calculation using the

Algorithm of choice.

Zone protection and directional overcurrent protection are crucial and necessary

in certain cases especially when reverse power is present.

A study was implemented on zone protection and the mho graph was displayed in

the GUI.

It all comes down to the engineer’s choice to what design to implement.

37

References

[1] J. Horak and W. Babic, “Directional Overcurrent Relaying (67) Concepts”, IEEE

Rural Electric Power Conference, 2006.

[2] A. Tabatabaei, M.R. Mosavi, & A. Rahmati, “Fault Location Techniques in Power

System based on Traveling Wave using Wavelet Analysis and GPS Timing”, Iran

University of Science and Technology.

[3] D. Uthitsunthorn, and T. Kulworawanichpong, “Distance Protection of a Renewable

Energy Plant in Electric Power Distribution Systems”, International Conference on

Power System Technology, 2010

[4] Linear Technology. “Overvoltage & Overcurrent Protection”. Internet:

www.linear.com/products/overvoltage__*_overcurrent_protection, 2013 [Nov. 2, 2013].

[5] Distance Protection. “Line Protection with Distance Relay”. Internet:

www.gedigitalenergy.com/multilin/notes/artsci/art14.pdf, Nov, 2013 [Nov. 5, 2013].

[6] Online Electrical Engineering Study Site. “Electrical Fuse HRC Fuse High Rupturing

Capacity”. Internet: www.electrical4u.com/electrical-fuse-hrc-fuse-high-rupturing-

capacity/, Nov, 2013 [Nov. 1, 2013].

[7] I. Chilvers and N. Jenkins, "Distance relaying of 1l kV circuits to increase the

installed capacity of distributed generation", IEEE Proceedings - Generation,

Transmission and Distribution.

[8] H. Shateri and S. Jamali, "Measured impedance by distance relay in second protective

zone", The International Universities Power Engineering Conference, September 2007

[9] L.G. Perez, and A.1 Urdaneta, "Optimal Computation of Distance Relays Second

Zone Timing in a Protection Scheme with Directional Overcurrent Relays", IEEE

Power Engineering Review.

[10] T Smith, M.E. Lacedonia, S. Pitts and Z. Zhang, “Review of Application of Ground

Distance Protection”,

[11] 1 Cho, C. Jung and 1 Kim, "Adaptive setting of digital relay for transmission line

protection", International Conference on Power System Technology.

http://www.linear.com/products/overvoltage__*_overcurrent_protection

http://www.gedigitalenergy.com/multilin/notes/artsci/art14.pdf

http://www.electrical4u.com/electrical-fuse-hrc-fuse-high-rupturing-capacity/

http://www.electrical4u.com/electrical-fuse-hrc-fuse-high-rupturing-capacity/

38

Appendix A. Fuse Curves Data

Table A1.1 – S&C Standard Curves Data Points

39

Appendix B. Partial GUI Code

function varargout = GradeProject(varargin) % gui_Singleton = 1; gui_State = struct('gui_Name', mfilename, ... 'gui_Singleton', gui_Singleton, ... 'gui_OpeningFcn', @GradeProject_OpeningFcn, ... 'gui_OutputFcn', @GradeProject_OutputFcn, ... 'gui_LayoutFcn', [] , ... 'gui_Callback', []); if nargin && ischar(varargin{1}) gui_State.gui_Callback = str2func(varargin{1}); end

if nargout [varargout{1:nargout}] = gui_mainfcn(gui_State, varargin{:}); else gui_mainfcn(gui_State, varargin{:}); end % End initialization code - DO NOT EDIT

% --- Executes just before GradeProject is made visible. function GradeProject_OpeningFcn(hObject, eventdata, handles, varargin) handles.output = hObject; set(hObject, 'Color', [0 1 1]); axes(handles.axes4); guidata(hObject, handles);

% --- Executes on selection change in popupmenu19. function popupmenu19_Callback(hObject, eventdata, handles) CT1=str2num((get(handles.edit17,'string'))); Is_ph1=str2num((get(handles.edit25,'string'))); Ip_ph1= CT1*Is_ph1; Imax=[20000 19500 19000 18500 18000 17500 17000 16500 16000 15500 15000

... 14500 14000 13500 13000 12500 12000 11500 11000 10500 10000 9500

9000 ... 8500 8000 7500 7000 6500 6000 5500 5000 4500 4000 3500 3000 2500

2000 ... 1500 1000]; Imult_p=Imax./Ip_ph1; switch get(handles.popupmenu19,'Value') case 1 TD_ph1=str2num((get(handles.edit22,'string'))); Tp_ph1=TD_ph1.*(0.0226+(0.0104./((Imult_p.^0.02)-1))); p72=1; p7111=num2str(p72); set(handles.edit140,'string',p7111) axes(handles.axes4) plot(Imult_p,Tp_ph1,'--r')

40

hold on

case 2 TD_ph1=str2num((get(handles.edit22,'string'))); Tp_ph1=TD_ph1.*(0.18+(5.95./((Imult_p.^2)-1))); p72=2; p7111=num2str(p72); set(handles.edit140,'string',p7111) axes(handles.axes4) plot(Imult_p,Tp_ph1,'--r') hold on



case 5 TD_ph1=str2num((get(handles.edit22,'string'))); Tp_ph1=TD_ph1.*(0.00262+(0.00342./((Imult_p.^0.02)-1))); p72=5; p7111=num2str(p72); set(handles.edit140,'string',p7111) axes(handles.axes4) plot(Imult_p,Tp_ph1,'--r') hold on

case 6 TD_ph1=str2num((get(handles.edit22,'string'))); Tp_ph1=TD_ph1.*(0.14./((Imult_p.^0.02)-1)); p72=6; p7111=num2str(p72); set(handles.edit140,'string',p7111) axes(handles.axes4) plot(Imult_p,Tp_ph1,'--r') hold on

case 7 TD_ph1=str2num((get(handles.edit22,'string'))); Tp_ph1=TD_ph1.*(13.5./((Imult_p)-1)); p72=7;

41

p7111=num2str(p72); set(handles.edit140,'string',p7111) axes(handles.axes4) plot(Imult_p,Tp_ph1,'--r') hold on

case 8 TD_ph1=str2num((get(handles.edit22,'string'))); Tp_ph1=TD_ph1.*(80./((Imult_p.^2)-1)); p72=8; p7111=num2str(p72); set(handles.edit140,'string',p7111) axes(handles.axes4) plot(Imult_p,Tp_ph1,'--r') hold on

case 9 TD_ph1=str2num((get(handles.edit22,'string'))); Tp_ph1=TD_ph1.*(120./((Imult_p)-1)); p72=9; p7111=num2str(p72); set(handles.edit140,'string',p7111) axes(handles.axes4) plot(Imult_p,Tp_ph1,'--r') hold on

case 10 TD_ph1=str2num((get(handles.edit22,'string'))); Tp_ph1=TD_ph1.*(0.05./((Imult_p.^0.04)-1)); p72=10; p7111=num2str(p72); set(handles.edit140,'string',p7111) axes(handles.axes4) plot(Imult_p,Tp_ph1,'--r') hold on

otherwise end

% --- Executes during object creation, after setting all properties. function axes13_CreateFcn(hObject, eventdata, handles) imshow('matadors.gif')

function pushbutton7_Callback(hObject, eventdata, handles) CT1=str2num((get(handles.edit2,'string'))); Is_ph1=str2num((get(handles.edit6,'string'))); Ip_ph1= CT1*Is_ph1; TD_ph1=str2num((get(handles.edit1,'string'))); Imax=str2num((get(handles.edit29,'string'))); Imult_p=Imax./Ip_ph1; R1_p=str2num((get(handles.edit135,'string'))); if R1_p==1 Tp_ph1=TD_ph1.*(0.0226+(0.0104./((Imult_p.^0.02)-1)));

42

Tp_ph11=num2str(Tp_ph1); set(handles.edit135,'string',Tp_ph11) elseif R1_p==2 Tp_ph1=TD_ph1.*(0.18+(5.95./((Imult_p.^2)-1))); Tp_ph11=num2str(Tp_ph1); set(handles.edit135,'string',Tp_ph11) elseif R1_p==3 Tp_ph1=TD_ph1.*(0.0963+(3.88./((Imult_p.^2)-1))); Tp_ph11=num2str(Tp_ph1); set(handles.edit135,'string',Tp_ph11) elseif R1_p==4 Tp_ph1=TD_ph1.*(0.0352+(5.67./((Imult_p.^2)-1))); Tp_ph11=num2str(Tp_ph1); set(handles.edit135,'string',Tp_ph11) elseif R1_p==5 Tp_ph1=TD_ph1.*(0.00262+(0.00342./((Imult_p.^0.02)-1))); Tp_ph11=num2str(Tp_ph1); set(handles.edit135,'string',Tp_ph11) elseif R1_p==6 Tp_ph1=TD_ph1.*(0.14./((Imult_p.^0.02)-1)); Tp_ph11=num2str(Tp_ph1); set(handles.edit135,'string',Tp_ph11) elseif R1_p==7 Tp_ph1=TD_ph1.*(13.5./((Imult_p)-1)); Tp_ph11=num2str(Tp_ph1); set(handles.edit135,'string',Tp_ph11) elseif R1_p==8 Tp_ph1=TD_ph1.*(80./((Imult_p.^2)-1)); Tp_ph11=num2str(Tp_ph1); set(handles.edit135,'string',Tp_ph11) elseif R1_p==9 Tp_ph1=TD_ph1.*(120./((Imult_p)-1)); Tp_ph11=num2str(Tp_ph1); set(handles.edit135,'string',Tp_ph11) elseif R1_p==10 Tp_ph1=TD_ph1.*(0.05./((Imult_p.^0.04)-1)); Tp_ph11=num2str(Tp_ph1); set(handles.edit135,'string',Tp_ph11) end Is_gd1=str2num((get(handles.edit7,'string'))); Ip_gd1= CT1*Is_gd1; TD_gd1=str2num((get(handles.edit3,'string'))); Imult_p1=Imax./Ip_gd1; R1_g=str2num((get(handles.edit136,'string'))); if R1_g==1 Tp_ph1=TD_ph1.*(0.0226+(0.0104./((Imult_p1.^0.02)-1))); Tp_ph11=num2str(Tp_ph1); set(handles.edit136,'string',Tp_ph11) elseif R1_g==2 Tp_ph1=TD_ph1.*(0.18+(5.95./((Imult_p1.^2)-1))); Tp_ph11=num2str(Tp_ph1); set(handles.edit136,'string',Tp_ph11) elseif R1_g==3 Tp_ph1=TD_ph1.*(0.0963+(3.88./((Imult_p1.^2)-1))); Tp_ph11=num2str(Tp_ph1); set(handles.edit136,'string',Tp_ph11) elseif R1_g==4

43

Tp_ph1=TD_ph1.*(0.0352+(5.67./((Imult_p1.^2)-1))); Tp_ph11=num2str(Tp_ph1); set(handles.edit136,'string',Tp_ph11) elseif R1_g==5 Tp_ph1=TD_ph1.*(0.00262+(0.00342./((Imult_p1.^0.02)-1))); Tp_ph11=num2str(Tp_ph1); set(handles.edit136,'string',Tp_ph11) elseif R1_g==6 Tp_ph1=TD_ph1.*(0.14./((Imult_p1.^0.02)-1)); Tp_ph11=num2str(Tp_ph1); set(handles.edit136,'string',Tp_ph11) elseif R1_g==7 Tp_ph1=TD_ph1.*(13.5./((Imult_p1)-1)); Tp_ph11=num2str(Tp_ph1); set(handles.edit136,'string',Tp_ph11) elseif R1_g==8 Tp_ph1=TD_ph1.*(80./((Imult_p1.^2)-1)); Tp_ph11=num2str(Tp_ph1); set(handles.edit136,'string',Tp_ph11) elseif R1_g==9 Tp_ph1=TD_ph1.*(120./((Imult_p1)-1)); Tp_ph11=num2str(Tp_ph1); set(handles.edit136,'string',Tp_ph11) elseif R1_g==10 Tp_ph1=TD_ph1.*(0.05./((Imult_p1.^0.04)-1)); Tp_ph11=num2str(Tp_ph1); set(handles.edit136,'string',Tp_ph11) end CT2=str2num((get(handles.edit16,'string'))); Is_ph2=str2num((get(handles.edit20,'string'))); Ip_ph2= CT2*Is_ph2; TD_ph2=str2num((get(handles.edit19,'string'))); Imult_p3=Imax./Ip_ph2; R2_p=str2num((get(handles.edit137,'string'))); if R2_p==1 Tp_ph1=TD_ph1.*(0.0226+(0.0104./((Imult_p3.^0.02)-1))); Tp_ph11=num2str(Tp_ph1); set(handles.edit137,'string',Tp_ph11) elseif R2_p==2 Tp_ph1=TD_ph1.*(0.18+(5.95./((Imult_p3.^2)-1))); Tp_ph11=num2str(Tp_ph1); set(handles.edit137,'string',Tp_ph11) elseif R2_p==3 Tp_ph1=TD_ph1.*(0.0963+(3.88./((Imult_p3.^2)-1))); Tp_ph11=num2str(Tp_ph1); set(handles.edit137,'string',Tp_ph11) elseif R2_p==4 Tp_ph1=TD_ph1.*(0.0352+(5.67./((Imult_p3.^2)-1))); Tp_ph11=num2str(Tp_ph1); set(handles.edit137,'string',Tp_ph11) elseif R2_p==5 Tp_ph1=TD_ph1.*(0.00262+(0.00342./((Imult_p3.^0.02)-1))); Tp_ph11=num2str(Tp_ph1); set(handles.edit137,'string',Tp_ph11) elseif R2_p==6 Tp_ph1=TD_ph1.*(0.14./((Imult_p3.^0.02)-1)); Tp_ph11=num2str(Tp_ph1);

44

set(handles.edit137,'string',Tp_ph11) elseif R2_p==7 Tp_ph1=TD_ph1.*(13.5./((Imult_p3)-1)); Tp_ph11=num2str(Tp_ph1); set(handles.edit137,'string',Tp_ph11) elseif R2_p==8 Tp_ph1=TD_ph1.*(80./((Imult_p3.^2)-1)); Tp_ph11=num2str(Tp_ph1); set(handles.edit137,'string',Tp_ph11) elseif R2_p==9 Tp_ph1=TD_ph1.*(120./((Imult_p3)-1)); Tp_ph11=num2str(Tp_ph1); set(handles.edit137,'string',Tp_ph11) elseif R2_p==10 Tp_ph1=TD_ph1.*(0.05./((Imult_p3.^0.04)-1)); Tp_ph11=num2str(Tp_ph1); set(handles.edit137,'string',Tp_ph11) end Is_gd2=str2num((get(handles.edit21,'string'))); Ip_gd2= CT2*Is_gd2; TD_gd2=str2num((get(handles.edit18,'string'))); Imult_p4=Imax./Ip_gd2; R2_g=str2num((get(handles.edit138,'string'))); if R2_g==1 Tp_ph1=TD_ph1.*(0.0226+(0.0104./((Imult_p4.^0.02)-1))); Tp_ph11=num2str(Tp_ph1); set(handles.edit138,'string',Tp_ph11) elseif R2_g==2 Tp_ph1=TD_ph1.*(0.18+(5.95./((Imult_p4.^2)-1))); Tp_ph11=num2str(Tp_ph1); set(handles.edit138,'string',Tp_ph11) elseif R2_g==3 Tp_ph1=TD_ph1.*(0.0963+(3.88./((Imult_p4.^2)-1))); Tp_ph11=num2str(Tp_ph1); set(handles.edit138,'string',Tp_ph11) elseif R2_g==4 Tp_ph1=TD_ph1.*(0.0352+(5.67./((Imult_p4.^2)-1))); Tp_ph11=num2str(Tp_ph1); set(handles.edit138,'string',Tp_ph11) elseif R2_g==5 Tp_ph1=TD_ph1.*(0.00262+(0.00342./((Imult_p4.^0.02)-1))); Tp_ph11=num2str(Tp_ph1); set(handles.edit138,'string',Tp_ph11) elseif R2_g==6 Tp_ph1=TD_ph1.*(0.14./((Imult_p4.^0.02)-1)); Tp_ph11=num2str(Tp_ph1); set(handles.edit138,'string',Tp_ph11) elseif R2_g==7 Tp_ph1=TD_ph1.*(13.5./((Imult_p4)-1)); Tp_ph11=num2str(Tp_ph1); set(handles.edit138,'string',Tp_ph11) elseif R2_g==8 Tp_ph1=TD_ph1.*(80./((Imult_p4.^2)-1)); Tp_ph11=num2str(Tp_ph1); set(handles.edit138,'string',Tp_ph11) elseif R2_g==9 Tp_ph1=TD_ph1.*(120./((Imult_p4)-1));

45

Tp_ph11=num2str(Tp_ph1); set(handles.edit138,'string',Tp_ph11) elseif R2_g==10 Tp_ph1=TD_ph1.*(0.05./((Imult_p4.^0.04)-1)); Tp_ph11=num2str(Tp_ph1); set(handles.edit138,'string',Tp_ph11) end CT3=str2num((get(handles.edit17,'string'))); Is_ph3=str2num((get(handles.edit24,'string'))); Ip_ph3= CT3*Is_ph3; TD_ph3=str2num((get(handles.edit23,'string'))); Imult_p5=Imax./Ip_ph3; R3_p=str2num((get(handles.edit139,'string'))); if R3_p==1 Tp_ph1=TD_ph1.*(0.0226+(0.0104./((Imult_p5.^0.02)-1))); Tp_ph11=num2str(Tp_ph1); set(handles.edit139,'string',Tp_ph11) elseif R3_p==2 Tp_ph1=TD_ph1.*(0.18+(5.95./((Imult_p5.^2)-1))); Tp_ph11=num2str(Tp_ph1); set(handles.edit139,'string',Tp_ph11) elseif R3_p==3 Tp_ph1=TD_ph1.*(0.0963+(3.88./((Imult_p5.^2)-1))); Tp_ph11=num2str(Tp_ph1); set(handles.edit139,'string',Tp_ph11) elseif R3_p==4 Tp_ph1=TD_ph1.*(0.0352+(5.67./((Imult_p5.^2)-1))); Tp_ph11=num2str(Tp_ph1); set(handles.edit139,'string',Tp_ph11) elseif R3_p==5 Tp_ph1=TD_ph1.*(0.00262+(0.00342./((Imult_p5.^0.02)-1))); Tp_ph11=num2str(Tp_ph1); set(handles.edit139,'string',Tp_ph11) elseif R3_p==6 Tp_ph1=TD_ph1.*(0.14./((Imult_p5.^0.02)-1)); Tp_ph11=num2str(Tp_ph1); set(handles.edit139,'string',Tp_ph11) elseif R3_p==7 Tp_ph1=TD_ph1.*(13.5./((Imult_p5)-1)); Tp_ph11=num2str(Tp_ph1); set(handles.edit139,'string',Tp_ph11) elseif R3_p==8 Tp_ph1=TD_ph1.*(80./((Imult_p5.^2)-1)); Tp_ph11=num2str(Tp_ph1); set(handles.edit139,'string',Tp_ph11) elseif R3_p==9 Tp_ph1=TD_ph1.*(120./((Imult_p5)-1)); Tp_ph11=num2str(Tp_ph1); set(handles.edit139,'string',Tp_ph11) elseif R3_p==10 Tp_ph1=TD_ph1.*(0.05./((Imult_p5.^0.04)-1)); Tp_ph11=num2str(Tp_ph1); set(handles.edit139,'string',Tp_ph11) end Is_gd3=str2num((get(handles.edit25,'string'))); Ip_gd3= CT3*Is_gd3; TD_gd3=str2num((get(handles.edit22,'string')));

46

Imult_p6=Imax./Ip_gd3; R3_g=str2num((get(handles.edit140,'string'))); if R3_g==1 Tp_ph1=TD_ph1.*(0.0226+(0.0104./((Imult_p6.^0.02)-1))); Tp_ph11=num2str(Tp_ph1); set(handles.edit140,'string',Tp_ph11) elseif R3_g==2 Tp_ph1=TD_ph1.*(0.18+(5.95./((Imult_p6.^2)-1))); Tp_ph11=num2str(Tp_ph1); set(handles.edit140,'string',Tp_ph11) elseif R3_g==3 Tp_ph1=TD_ph1.*(0.0963+(3.88./((Imult_p6.^2)-1))); Tp_ph11=num2str(Tp_ph1); set(handles.edit140,'string',Tp_ph11) elseif R3_g==4 Tp_ph1=TD_ph1.*(0.0352+(5.67./((Imult_p6.^2)-1))); Tp_ph11=num2str(Tp_ph1); set(handles.edit140,'string',Tp_ph11) elseif R3_g==5 Tp_ph1=TD_ph1.*(0.00262+(0.00342./((Imult_p6.^0.02)-1))); Tp_ph11=num2str(Tp_ph1); set(handles.edit140,'string',Tp_ph11) elseif R3_g==6 Tp_ph1=TD_ph1.*(0.14./((Imult_p6.^0.02)-1)); Tp_ph11=num2str(Tp_ph1); set(handles.edit140,'string',Tp_ph11) elseif R3_g==7 Tp_ph1=TD_ph1.*(13.5./((Imult_p6)-1)); Tp_ph11=num2str(Tp_ph1); set(handles.edit140,'string',Tp_ph11) elseif R3_g==8 Tp_ph1=TD_ph1.*(80./((Imult_p6.^2)-1)); Tp_ph11=num2str(Tp_ph1); set(handles.edit140,'string',Tp_ph11) elseif R3_g==9 Tp_ph1=TD_ph1.*(120./((Imult_p6)-1)); Tp_ph11=num2str(Tp_ph1); set(handles.edit140,'string',Tp_ph11) elseif R3_g==10 Tp_ph1=TD_ph1.*(0.05./((Imult_p6.^0.04)-1)); Tp_ph11=num2str(Tp_ph1); set(handles.edit140,'string',Tp_ph11) end

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