power system modelling and analysis of a combined cycle power

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




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-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



6.6KV BUS A(BOARD 2)6.6 kV

6.6KV BUS B(BOARD 2)6.6 kV


BUS 760.415 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



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


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-A(BOARD 6)

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-A(BOARD 6)

0.415 kV

CB110CB111

OpenCB112

BUS-A(BOARD 5)0.415 kV 0.415 kV

BOARD 80.415 kV


LUBE-390 kW


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




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




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:




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.

https://etap.com/

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power system modelling and analysis of a combined cycle power