International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395 -0056
Volume: 03 Issue: 06 | June-2016 www.irjet.net p-ISSN: 2395-0072
© 2016, IRJET | Impact Factor value: 4.45 | ISO 9001:2008 Certified Journal | Page 1331
POWER SYSTEM MODELLING AND ANALYSIS OF A COMBINED CYCLE
POWER PLANT USING ETAP
Ch. Siva Kumari1, D. Sreenivasulu Reddy2
1PG Scholar, Dept. of Electrical and Electronics Engineering, SreeVidyanikethan Engineering college, Tirupathi, Andhra Pradesh, India.
2Assistant Professor, Dept. of Electrical and Electronics Engineering, SreeVidyanikethan Engineering college, Tirupathi, Andhra Pradesh, India.
--------------------------------------------------------------------------***---------------------------------------------------------------------------- Abstract-This paper presents a methodology for keen assessment of power supply reliability and quality of electrical network. Now a days power supply reliability and quality are major concern. Study of electrical power system is an essential element in power system planning and design. The power system studies are conducted for ensuring the designed network is meeting the required specifications and standards with respect to safety, flexibility in operation, etc.,. In this paper the major emphasis will be given on performing load flow analysis, short circuit analysis, transient stability analysis and relay coordination. These analyses are done in this paper by using ETAP (Electrical Transient Analyser Program).
Key Words: ETAP software, over current relays, relay settings, relay coordination and Transient stability analysis.
1. INTRODUCTION
Availability of various generation sources such as conventional and non-conventional sources. These sources can significantly impact the power flow and voltage profile as well as other parameters at customers and utility side. Electrical networks/installations are designed based on national and international standards depending on the type of the project and its requirements. In addition, some initial FEED (Front End Engineering Design) studies are taken before the system single line diagram is frozen. The power system Studies are essential to pre-confirm the parameters of various equipments/components of the planned electrical facility. In electrical power systems, most of the electrical parameters variation occurs dynamically due to sudden addition or sudden tripping of generators. The faulted/disturbance occurred part of the network is isolated by analysing the electrical power system.
Electrical power generation broadly classified into two types based on the utilization of power. The first one is captive power plants, it refers to power generated from the plant set up by an industry is used for its own exclusive consumption. Second one is utility power
plants, it refers to generated power is sold or supplied to various customers and not for its own use. Combined cycle power plant is a type of captive power plant and it is the combination of steam turbine and diesel turbine. Each captive power plant has to be tailor made to suit particular customer/industry need. It includes setting up and commissioning of generators, hooking up with grid, catering to the power plant auxiliaries as well as customer’s industrial loads to ensure availability of adequate reliable power supply to the industry.
1.1 Designing Objectives:
While designing a captive power plant and offerings as a business solution, following are the major objectives to be met:
i. Ensuring optimization in equipment selection. ii. Identifying and rectifying deficiencies in the system at
the design stage itself before it goes into operation. iii. Analysing different power plant operating scenarios
for economic operation. iv. Establishing system performance and guarantees. v. Ensuring safe and reliable operation.
vi. Establishing the provisions of the system’s future expansion plans.
2. SINGLE LINE DIAGRAM USING ETAP
Fig. 1 shows the combined cycle power plant consisting of two steam turbine generators (STG) with a capacity of 36MW each, two gas turbine generators (GTG) with a capacity of 34.5MW each and it is connected to grid [1]. Different loads are connected at different bus levels (33KV, 6.6KV, 415V). Different types of loads are lump loads, HT motors and LT motors. Lump loads are the combination of 70% motor load and 30% non-motor load operating with a power factor of 0.88 lag. IEC standard ETAP software library data [2] is considered as default data for impedances of the system components.
3. LOAD FLOW ANALYSIS AND ITS RESULTS
International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395 -0056
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Checking of the system performance i.e., checking of the adequacy of all system component ratings, transformer sizes and their impedances and tap changer settings under a variety of operating conditions including contingency conditions [1]. The main objective of the load flow analysis [3] is determination of the steady state active and reactive power flows, current flows, system power factor and system voltage profiles (magnitudes and phase angles of load and generator bus voltages). Fig. 2 shows the load flow analysis results of a combined cycle power plant.
Fig-1: Single line diagram of combined cycle power plant
Fig-2: Load flow analysis results
4. SHORT CIRCUIT ANALYSIS AND ITS FAULTS
Fault level (short circuit) analysis are used to determine both maximum and minimum three phase faults and earth fault level at all switch boards under fault make and fault break conditions including the dc component [4]. Types of short circuit faults are line to ground (LG) fault, line to line (LL) fault, double line to ground (LLG) fault, three phase (LLL) fault and three phase to ground (LLLG) fault.
IEC standards use the following definitions, which are relevant in the calculations and outputs of ETAP for Short circuit analysis.
Initial Symmetrical Short Circuit Current (I”K): This is the RMS value of the AC symmetrical component of an available short circuit current applicable at the instant of short circuit if the impedance remains at zero time value.
Peak Short Circuit Current (Ip): This is the maximum possible instantaneous value of the available short circuit current.
BUS-A(BOARD 3)0.415 kV
33KV BUS-B33 kV
6.6KV BUS A (BOARD 1)
6.6 kV
6.6KV BUS B (BOARD 1)
6.6 kV
BUS-B(BOARD1)0.415 kV
BUS-A(BOARD1)
0.415 kV
BUS 570.415 kV
BUS 580.415 kV
33 KV BUS-A33 kV
GRID I/C-115242 MVAsc
CB1
GRID TRAFO-1
15 %Z
220/33 kV50 MVA
CB2
CB15
STG 136 MW
CB3
GEN TRAFO-1
15.62 %Z
11/34.5 kV50 MVA
CB4
STG 236 MW
CB5
GEN TRAFO-2
15.49 %Z
11/34.5 kV50 MVA
CB6
Lump1
100 MVA
CB21
CB25
BFP-2850 kW
CB40
CC-2650 kW
CB41
CC-3(S/B)650 kW
CB42
CWP-2(S/B)1250 kW
CB43
S/S-1-I/C23125 kVA
CB39
CAP-23000 kvar
CB44
CB26Open
CB36
UAT-3
10.57 %Z
6.6/0.433 kV2.5 MVA
CB64
CB70
CB125CB126Open
CB124
CB69
LCO-175 kW
CB67
AUG. AF-155 kW
CB68
HRSG-2
800 kVA
CB65
LCO-275 kW
CB71
AUG. AF-2(S/B)55 kW
CB72
HRSG-2.800 kVA
CB66Open
UAT-2
10.35 %Z
6.6/0.433 kV2.5 MVA
CB37 CB38
UAT-4
10.48 %Z
6.6/0.433 kV
2.5 MVAUAT-1
10.53 %Z
6.6/0.433 kV2.5 MVA
CB35
BFP-1(S/B)850 kW
CB31
S/S-1-I/C13125 kVA
CB30
CC-1650 kW
CB32
CWP-11250 kW
CB33
CAP-13000 kvar
CB34
CB24
SAT-1
12.13 %Z
33/6.9 kV31.5 MVA
CB19
Lump16
60 MVA
CB129CB20
SAT-3
12.01 %Z
33/6.9 kV31.5 MVA
BOIL-1.71.9 kVA
ASB (CUS)71.9 kVA
BUS-B(BOARD1)0.415 kV
BUS-A(BOARD1)
0.415 kV
6.6KV BUS B (BOARD 1)
6.6 kV
6.6KV BUS A (BOARD 1)
6.6 kV
33KV BUS-B33 kV
33 KV BUS-A33 kV
CB2
GRID TRAFO-1
15 %Z
220/33 kV50 MVA
CB15
CB19
SAT-1
12.13 %Z
33/6.9 kV31.5 MVA
CB20
SAT-3
12.01 %Z
33/6.9 kV31.5 MVA
CB4
GEN TRAFO-1
15.62 %Z
11/34.5 kV50 MVA
CB6
GEN TRAFO-2
15.49 %Z
11/34.5 kV50 MVA
CB22
STG 136 MW
STG 236 MW
CB3 CB5CB1
CB35
UAT-1
10.53 %Z
6.6/0.433 kV2.5 MVA
CB36
UAT-3
10.57 %Z
6.6/0.433 kV2.5 MVA
CB31
BFP-1(S/B)850 kW
CB30 CB32
CC-1650 kW
CB33
CWP-11250 kW
CB40
BFP-2850 kW
CB41
CC-2650 kW
CB42
CC-3(S/B)650 kW
CB43
CWP-2(S/B)1250 kW
CB34 CB39
CB25
CB38
UAT-4
10.48 %Z
6.6/0.433 kV
2.5 MVA
CB37
UAT-2
10.35 %Z
6.6/0.433 kV2.5 MVA
CB44
CB24CB26Open
CB64
CB66OpenCB65
CAP-13000 kvar
CAP-23000 kvar
BUS 570.415 kV
LCO-175 kW
BUS 580.415 kV
LCO-275 kWAUG. AF-1
55 kW
AUG. AF-2(S/B)55 kW
CB126Open
S/S-1-I/C13125 kVA
S/S-1-I/C23125 kVA
HRSG-2
800 kVA
HRSG-2.800 kVA
BOIL-1.71.9 kVA
CB67 CB68 CB69 CB70 CB71 CB72
CB124 CB125
ASB (CUS)71.9 kVA
Lump1
100 MVA
CB21
Lump16
60 MVA
CB129
GRID I/C-115242 MVAsc
BUS-A(BOARD 2)
0.415 kV
BUS-B(BOARD 2)0.415 kV
BUS 67
0.415 kV
BUS 66
0.415 kV
MHU-1110 kW
CB76
LT HEAT-1
55 kW
CB77
RCC CTID-1110 kW
CB78
RCC CTID-2110 kW
CB79
RCC CTID-3110 kW
CB80
Lump3160 kVA
Lump2160 kVA
CB75Open
MHU-2110 kW
CB83
RCC CTID-6110 kW
CB87
Mtr175 kW
CB86
LT HEAT-255 kW
CB84
RCC CTID-4110 kW
CB85CB81
CB88
Lump4235 kVA
CB90
Open
Lump5235 kVA
CB89
CB82
CB74CB73
BUS-B(BOARD 2)0.415 kV
BUS-A(BOARD 2)
0.415 kV
CB75Open
CB73CB74
MHU-1110 kW
LT HEAT-1
55 kW
RCC CTID-1110 kW
RCC CTID-2110 kW
RCC CTID-3110 kW
MHU-2110 kW
LT HEAT-255 kW
RCC CTID-4110 kW
RCC CTID-6110 kW
BUS 66
0.415 kV
BUS 67
0.415 kV
CB90
Open
CB76CB77
CB78 CB79 CB80CB81 CB82
CB83 CB84 CB85 CB86 CB87
CB88 CB89
Lump5235 kVA
Lump4235 kVA
Lump2160 kVA
Lump3160 kVA
Mtr175 kW
BUS-A(BOARD 4)0.415 kV
BUS-B(BOARD 4)0.415 kV
6.6KV BUS A(BOARD 2)6.6 kV
6.6KV BUS B(BOARD 2)6.6 kV
BUS-B(BOARD 3)0.415 kV
BUS 760.415 kV
BUS-A(BOARD 5)0.415 kV
BUS-B(BOARD 5)0.415 kV
ACW-1360 kW
CB46
CAP-3
3000 kvar
CB48
CTP-1315 kW
CB49
GBC-1750 kW
CB50
BFP-UB-1(S/B)1750 kW
CB51
BFP-HRSG-1910 kW
CB52
FD FAN-UB-11200 kW
CB53
SAT-2
12.13 %Z
33/6.9 kV31.5 MVA
BFP-HRSG-2910 kW
CB55
BFP-HRSG-3(S/B)910 kW
CB56Open
CB45
UAT-5
10.54 %Z
6.6/0.433 kV2.5 MVA
UAT-6
10.28 %Z
6.6/0.433 kV2.5 MVA
CB58
CTP-2(S/B)315 kW
CB57Open
BFP-UB-31750 kW
CB59
GBC-2(S/B)750 kW
CB60Open
ACW-2(S/B)360 kW
CB61Open
CAP-43000 kvar
CB63
CB99
LUBE-2 STG-290 kW
CB101 CB103
CB109
CB108
Open
CB107
CB102
LUBE-2 STG-190 kW
CB104CB96
CB105CB106
CB100Open
BOIL -1.71.9 kVA
ACELDB71.9 kVA
110 UPS-2144 kVA
ASB(CUS)71.9 kVA
ACELDB.71.9 kVA
110V UPS-3144 kVA
CB98Open
UAT-8
10.4 %Z
6.6/0.433 kV2.5 MVA
CB54
CB28
FD FAN-UB-21200 kW
CB62
CB29 Open
SAT-4
12.33 %Z
33/6.9 kV31.5 MVA
CB23
GTG 234.5 MW
CB11
GEN TRAFO-5
15.47 %Z
11/34.5 kV50 MVA
CB12
GTG 134.5 MW
CB9
GEN TRAFO-4
15.53 %Z
11/34.5 kV50 MVA
CB10
CB27
CB47
UAT-7
10.55 %Z
6.6/0.433 kV
2.5 MVA
CB97
CB92
CB345
CB286
OpenCB344
CB91
LUBE-1 STG-190 kW
CB93
LUBE-1 STG-290 kW
CB94
BSCWP-190 kW
CB95UPS1
144 kVA
110V UPS-1144 kVA
BUS-B(BOARD 3)0.415 kV
BUS-A(BOARD 3)0.415 kV
6.6KV BUS B(BOARD 2)6.6 kV
6.6KV BUS A(BOARD 2)6.6 kV
CB10
GEN TRAFO-4
15.53 %Z
11/34.5 kV50 MVA
CB12
GEN TRAFO-5
15.47 %Z
11/34.5 kV50 MVA
SAT-2
12.13 %Z
33/6.9 kV31.5 MVA
CB23
SAT-4
12.33 %Z
33/6.9 kV31.5 MVA
GTG 134.5 MW
CB9
GTG 234.5 MW
CB11
CB46 CB48
ACW-1360 kW
CB47
UAT-7
10.55 %Z
6.6/0.433 kV
2.5 MVA
CB49
CTP-1315 kW
CB50
GBC-1750 kW
CB51
BFP-UB-1(S/B)1750 kW
CB52
BFP-HRSG-1910 kW
CB53
FD FAN-UB-11200 kW
CB28
CB55 CB56Open
BFP-HRSG-2910 kW
BFP-HRSG-3(S/B)910 kW
CTP-2(S/B)315 kW
CB58
UAT-6
10.28 %Z
6.6/0.433 kV2.5 MVA
CB57Open CB59
BFP-UB-31750 kW
CB60Open
CB61Open
GBC-2(S/B)750 kW
ACW-2(S/B)360 kW
CB62 CB63
FD FAN-UB-21200 kW
CB45
UAT-5
10.54 %Z
6.6/0.433 kV2.5 MVA
CB54
UAT-8
10.4 %Z
6.6/0.433 kV2.5 MVA
CB27
CB29 Open
CB98Open
CB97
CB99
CAP-3
3000 kvarCAP-43000 kvar
BUS 760.415 kV
BUS-A(BOARD 4)0.415 kV
LUBE-1 STG-190 kWBUS-B(BOARD 4)
0.415 kV
LUBE-1 STG-290 kW
BSCWP-190 kW
BUS-B(BOARD 5)
LUBE-2 STG-290 kW LUBE-2 STG-1
90 kW
CB286
Open
CB108
Open BOIL -1.71.9 kVA
CB91CB92
CB93 CB94 CB95 CB96 CB100Open
CB101CB102
CB103 CB104
CB344 CB345CB107 CB109
CB105CB106110V UPS-1
144 kVAACELDB71.9 kVA
110 UPS-2144 kVA
ASB(CUS)71.9 kVA
ACELDB.71.9 kVA
110V UPS-3144 kVA
UPS1
144 kVA
BUS-B(BOARD 6)0.415 kV
BUS-A(BOARD 6)
0.415 kV
BUS-A(BOARD 7)0.415 kV
BUS-B(BOARD 7)0.415 kV
BOARD 80.415 kV
CB110
CB116Open
CB119
Lump11542 kVA
CB120
CB115CB117
CB122
Lump13
125 kVA
CB123OpenLump12
125 kVA
CB121
CB114
LUBE-390 kW
CB113
BOIL-271.9 kVA
CB112
LUBE-490 kW
CB118
BOIL-2.71.9 kVA
220V DC-171.9 kVA
BOIL-371.9 kVA 220V DC-2
71.9 kVABOIL-3.71.9 kVA
CB111Open
Lump10185 kVA
Lump9185 kVA
Lump8460 kVA
Lump785 kVA
Lump685 kVA
BUS-B(BOARD 6)0.415 kV
BUS-A(BOARD 6)
0.415 kV
CB110CB111
OpenCB112
BUS-A(BOARD 5)0.415 kV 0.415 kV
BOARD 80.415 kV
BUS-A(BOARD 7)0.415 kV
LUBE-390 kW
BUS-B(BOARD 7)0.415 kV
LUBE-490 kW
CB123Open
BOIL-271.9 kVA
BOIL-2.71.9 kVA
CB113 CB114CB115 CB116
Open CB117CB118
CB120 CB119
CB122
CB121220V DC-171.9 kVA
BOIL-371.9 kVA 220V DC-2
71.9 kVA
Lump685 kVA
Lump785 kVA
Lump8460 kVA Lump9
185 kVALump10185 kVA
Lump12125 kVA
Lump13
125 kVA
Lump11542 kVA
BOIL-3.71.9 kVA
International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395 -0056
Volume: 03 Issue: 06 | June-2016 www.irjet.net p-ISSN: 2395-0072
© 2016, IRJET | Impact Factor value: 4.45 | ISO 9001:2008 Certified Journal | Page 1333
Symmetrical Short Circuit Breaking Current (Ib): This is the RMS value of an integral cycle of the symmetrical AC component of the available short circuit current at the instant of contact separation of the first pole of a switching device.
Steady-State Short Circuit Current (Ik): This is the RMS value of the short circuit current, which remains after the decay of the transient phenomena.
Voltage Factor (c): This is the factor used to adjust the value of the equivalent voltage source for minimum and maximum current calculations.
4.1 CALCULATION METHODS:
Initial Symmetrical Short Circuit Current Calculation: Initial symmetrical short-circuit current (Ik
’’) is calculated using the following formula:
k
n
kZ
cUI
3
'' …
Eqn (1)
Where, Zk is the equivalent impedance at the fault location.
Peak Short Circuit Current Calculation: Peak short-circuits current (ip) is calculated using the following formula:
''2 kp kIi …
Eqn (2)
Where, k is a function of the system R/X ratio at the fault location.
In this paper, we considered three faults i.e., LG, LLG and three phase faults at randomly considered buses. The following table-1 gives the short circuit fault current at different buses considering LG Fault.
Table-1: Fault currents at different buses considering LG Fault
FAULTED BUS VOLTAGE (KV)
FAULT CURRENT (KA)
33KV BUS-A 19.76 32.07
6.6KV BUS-A (BOARD 1) 6.55 0.63
415V BUS-A (BOARD 1) 0.26 41.09
415V BUS-B (BOARD 3) 0.25 37.97
415V BUS-B (BOARD 6) 0.25 38.32
The following table-2 and table-3 gives the short circuit fault currents and voltages at different bus boards considering LLG Fault and three phase fault respectively.
Table-2: Fault currents at different buses considering LLG Fault
FAULTED BUS VOLTAGE (KV)
FAULT CURRENT (KA)
33KV BUS-A 19.67 31.9
6.6KV BUS-A (BOARD 1)
5.64 0.311
415V BUS-A (BOARD 1)
0.26 37.26
415V BUS-B (BOARD 3)
0.25 35.93
415V BUS-B (BOARD 6)
0.26 36.1
Table-3: Fault currents at different buses
considering LLL Fault
FAULTED BUS FAULT CURRENT (KA)
33KV BUS-A 33.1
6.6KV BUS-A (BOARD 1) 25.9
415V BUS-A (BOARD 1) 46.1
415V BUS-B (BOARD 3) 40.5
415V BUS-B (BOARD 6) 41.1
5. TRANSIENT STABILITY ANALYSIS
Determination of the system response due to different disturbances which are the source of instability i.e., which lead to loss of synchronism or stalling or overloading of generators and motors. Switching transients [5] are mostly associated with mal-functioning of circuit breakers and switches, switching of capacitor banks and other frequently switched loads.
In this we considered that three phase fault is occurred at 0.5 Sec on 33KV bus, then the system may goes into unstable condition. After making some trails we can conclude that the critical clearing time [6] is 0.74
International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395 -0056
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Sec i.e., the system is stable if the fault is cleared before 0.24 Sec after the fault is created otherwise the system goes into unstable condition. The following fig. 3 and fig. 4 shows the power angle of the system and speed of the generator respectively.
Fig-3: Power angle
Fig-4: Generator speed
6. RELAY CO-ORDINATION
Typical power system comprises number of important equipments which have to be protected. In order to provide sufficient reliable protection to ensure smooth working of power system, installation of relay and circuit breaker sets are required. Primary protection relay must operate within its pre-determined time period [7]. In case of failure of primary protection relay operation which may be because of any reason, back-up protection [8] has to take care by its operation and hence relay coordination is very important to minimize the outages which are occurring frequently. Over current relays [9]is one of the most important protection devices in the captive power plants. The primary protection and backup protection are provided by co-ordinating the
relays which are placed at different branches in the network. In this paper, we considered the relays of relay140, relay146, relay157, relay198, relay205 and relay 382 and the characteristics of these all relays are shown in following fig. 5.
Fig-5: Characteristics of relays
Plug setting multiplier (PSM) and time setting multiplier (TSM) are to be calculated for the co-ordination of the relays. The definitions which are relevant in the calculations and outputs of ETAP are as follows:
TMS adjusts the operating time of the relay. If the TMS value is low then the operation of relay is fast.
ratio CT X setting Plug
currentFault = PSM
...Eqn (3)
In this paper we considered that if the three phase fault is occurred at lump load of 235KVA which is connected at bus6, then the relays will operate as follows:
International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395 -0056
Volume: 03 Issue: 06 | June-2016 www.irjet.net p-ISSN: 2395-0072
© 2016, IRJET | Impact Factor value: 4.45 | ISO 9001:2008 Certified Journal | Page 1335
Fig-6: Relay co-ordination of the system
7. CONCLUSION
Thus, in this paper, we have modelled the combined cycle power plant in the ETAP software and different power system analyses are done in single network. The network is very complicated, so the calculations can’t able to do by hand calculation. ETAP is very helpful to reduce the malfunctioning of network and to increase the efficiency of the system by operating proper relay co-ordination within less time.
REFERENCES :
1. Raja Nivedha.R, Sreevidya.L, V.Geetha, R.Deepa, “Design of Optimal Power System Stabilizer Using ETAP”, International Journal of Power System Operation and Energy Management, ISSN (PRINT): 2231–4407, Volume-1, Issue-2, 2011.
2. https://ETAP.com.
3. Rohankapahi, “Load flow analysis of 132kV substation using ETAP software”, IJSER, volume 4, Issue 2, Feb 2013.
4. Bruce L. Graves “Short Circuit, coordination and harmonic studies” Industry Applications Magazine, IEEE Volume:7, Issue: 2, PP:14-18, Publication Year: 2001.
5. Jignesh S. Patel, Manish N. Sinha, “Power System Transient Stability Analysis Using ETAP Software”, National Conference on Recent Trends in Engineering & Technology, 13-14 May 2011.
6. Lewis G. W. Roberts, Alan R.Champneys, Keith R. W. Bell, Mario di Bernardo, “Analytical Approximations of Critical Clearing Time for Parametric Analysis of Power System Transient Stability”, IEEE Journal on Emerging And Selected Topics in Circuits and Systems, Vol.5, No.3, PP:465-472, September 2015.
7. Prof. vipul N. Rajput, Prof. Tejas M. vala, “ Co-ordination of over current relays for chemical industrial plant using ETAP”, International journal of futuristic trends in Engineering and Technology, vol.1(2), PP.36-39, 2014.
8. BhuvaneshOza, Nirmalkumar Nair, Rashesh Mehta, Vijay Makwana, “Power System Protection & Switchgear” Tata McGraw Hill Education Private limited, New Delhi, 2010.pp 1-50, 175-270.
9. PrashantP.Bedekar, Sudhir R. Bhide, and Vijay S. Kale, “Coordination of Overcurrent Relays in Distribution System using Linear Programming Technique”, IEE International conference on Control, Automation, Communicated & Energy Conservation June 2009.