Power System Modelling and Analysis of a Combined Cycle Power Plant Using ETAP

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POWER SYSTEM MODELLING AND ANALYSIS OF A COMBINED CYCLE

POWER PLANT USING ETAP

Ch. Siva Kumari

_{, D. Sreenivasulu Reddy}

1

_{PG Scholar, Dept. of Electrical and Electronics Engineering,}

SreeVidyanikethan Engineering college, Tirupathi, Andhra Pradesh, India.

2

_{Assistant 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.

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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-B

33 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 57 0.415 kV BUS 58 0.415 kV 33 KV BUS-A

33 kV GRID I/C-1 15242 MVAsc CB1 GRID TRAFO-1 15 %Z 220/33 kV50 MVA CB2 CB15 STG 1 36 MW CB3 GEN TRAFO-1 15.62 %Z 11/34.5 kV 50 MVA CB4 STG 2 36 MW CB5 GEN TRAFO-2 15.49 %Z 11/34.5 kV 50 MVA CB6 Lump1 100 MVA CB21 CB25 BFP-2 850 kW CB40 CC-2 650 kW CB41 CC-3(S/B) 650 kW CB42 CWP-2(S/B) 1250 kW CB43 S/S-1-I/C2 3125 kVA CB39 CAP-2 3000 kvar CB44 CB26 Open CB36 UAT-3 10.57 %Z 6.6/0.433 kV 2.5 MVA CB64 CB70 CB125 CB126 Open CB124 CB69 LCO-1 75 kW CB67 AUG. AF-1 55 kW CB68 HRSG-2 800 kVA CB65 LCO-2 75 kW CB71 AUG. AF-2(S/B) 55 kW CB72 HRSG-2. 800 kVA CB66 Open UAT-2 10.35 %Z 6.6/0.433 kV 2.5 MVA CB37 CB38 UAT-4 10.48 %Z 6.6/0.433 kV 2.5 MVA UAT-1 10.53 %Z 6.6/0.433 kV 2.5 MVA CB35 BFP-1(S/B) 850 kW CB31 S/S-1-I/C1 3125 kVA CB30 CC-1 650 kW CB32 CWP-1 1250 kW CB33 CAP-1 3000 kvar CB34 CB24 SAT-1 12.13 %Z 33/6.9 kV 31.5 MVA CB19 Lump16 60 MVA CB129 CB20 SAT-3 12.01 %Z 33/6.9 kV 31.5 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-B 33 kV 33 KV BUS-A

33 kV CB2 GRID TRAFO-1 15 %Z 220/33 kV50 MVA

CB15 CB19 SAT-1 12.13 %Z 33/6.9 kV 31.5 MVA CB20 SAT-3 12.01 %Z 33/6.9 kV 31.5 MVA CB4 GEN TRAFO-1 15.62 %Z 11/34.5 kV 50 MVA CB6 GEN TRAFO-2 15.49 %Z 11/34.5 kV 50 MVA CB22 STG 1

36 MW 36 MWSTG 2

CB3 CB5 CB1 CB35 UAT-1 10.53 %Z 6.6/0.433 kV 2.5 MVA CB36 UAT-3 10.57 %Z 6.6/0.433 kV 2.5 MVA CB31 BFP-1(S/B) 850 kW CB30 CB32 CC-1 650 kW CB33 CWP-1 1250 kW CB40 BFP-2 850 kW CB41 CC-2 650 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 kV 2.5 MVA CB44 CB24 CB26 Open CB64 CB66 Open CB65 CAP-1 3000 kvar CAP-2 3000 kvar BUS 57 0.415 kV LCO-1 75 kW BUS 58 0.415 kV LCO-2 75 kW AUG. AF-1 55 kW AUG. AF-2(S/B) 55 kW CB126 Open S/S-1-I/C1 3125 kVA S/S-1-I/C2 3125 kVA HRSG-2 800 kVA HRSG-2. 800 kVA BOIL-1. 71.9 kVA

CB67CB68 CB69 CB70 CB71 CB72 CB124 CB125 ASB (CUS) 71.9 kVA Lump1 100 MVA CB21 Lump16 60 MVA CB129 GRID I/C-1 15242 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-1 110 kW CB76 LT HEAT-1 55 kW CB77 RCC CTID-1 110 kW CB78 RCC CTID-2 110 kW CB79 RCC CTID-3 110 kW CB80 Lump3 160 kVA Lump2 160 kVA CB75 Open MHU-2 110 kW CB83 RCC CTID-6 110 kW CB87 Mtr1 75 kW CB86 LT HEAT-2 55 kW CB84 RCC CTID-4 110 kW CB85 CB81 CB88 Lump4 235 kVA CB90 Open Lump5 235 kVA CB89 CB82 CB74 CB73 BUS-B(BOARD 2) 0.415 kV BUS-A(BOARD 2) 0.415 kV CB75 Open CB73 CB74 MHU-1 110 kW LT HEAT-1

55 kWRCC CTID-1110 kWRCC CTID-2110 kWRCC CTID-3110 kW 110 kWMHU-2LT HEAT-255 kWRCC CTID-4110 kW RCC CTID-6

110 kW BUS 66 0.415 kV BUS 67 0.415 kV CB90 Open

CB76 CB77 CB78CB79 CB80 CB81 CB82 CB83 CB84 CB85 CB86 CB87 CB88 CB89 Lump5 235 kVA Lump4 235 kVA Lump2

160 kVA Lump3160 kVA

Mtr1

75 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 76 0.415 kV

BUS-A(BOARD 5)0.415 kV BUS-B(BOARD 5)0.415 kV ACW-1 360 kW CB46 CAP-3 3000 kvar CB48 CTP-1 315 kW CB49 GBC-1 750 kW CB50 BFP-UB-1(S/B) 1750 kW CB51 BFP-HRSG-1 910 kW CB52 FD FAN-UB-1 1200 kW CB53 SAT-2 12.13 %Z 33/6.9 kV 31.5 MVA BFP-HRSG-2 910 kW CB55 BFP-HRSG-3(S/B) 910 kW CB56 Open CB45 UAT-5 10.54 %Z 6.6/0.433 kV2.5 MVA

UAT-6 10.28 %Z 6.6/0.433 kV 2.5 MVA CB58 CTP-2(S/B) 315 kW CB57 Open BFP-UB-3 1750 kW CB59 GBC-2(S/B) 750 kW CB60 Open ACW-2(S/B) 360 kW CB61 Open CAP-4 3000 kvar CB63 CB99 LUBE-2 STG-2 90 kW CB101 CB103 CB109 CB108 Open CB107 CB102 LUBE-2 STG-1 90 kW CB104 CB96 CB105 CB106 CB100 Open BOIL -1.

71.9 kVAACELDB.71.9 kVAACELDB71.9 kVA110 UPS-2144 kVAASB(CUS)71.9 kVA

110V UPS-3 144 kVA CB98 Open UAT-8 10.4 %Z 6.6/0.433 kV 2.5 MVA CB54 CB28 FD FAN-UB-2 1200 kW CB62 CB29Open SAT-4 12.33 %Z 33/6.9 kV 31.5 MVA CB23 GTG 2 34.5 MW CB11 GEN TRAFO-5 15.47 %Z 11/34.5 kV 50 MVA CB12 GTG 1 34.5 MW CB9 GEN TRAFO-4 15.53 %Z 11/34.5 kV 50 MVA CB10 CB27 CB47 UAT-7 10.55 %Z 6.6/0.433 kV 2.5 MVA CB97 CB92 CB345 CB286 Open CB344 CB91 LUBE-1 STG-1 90 kW CB93 LUBE-1 STG-2 90 kW CB94 BSCWP-1 90 kW CB95 UPS1 144 kVA 110V UPS-1 144 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 kV 50 MVA CB12 GEN TRAFO-5 15.47 %Z 11/34.5 kV 50 MVA SAT-2 12.13 %Z 33/6.9 kV 31.5 MVA CB23 SAT-4 12.33 %Z 33/6.9 kV 31.5 MVA GTG 1 34.5 MW CB9 GTG 2 34.5 MW CB11 CB46 CB48 ACW-1 360 kW CB47 UAT-7 10.55 %Z 6.6/0.433 kV 2.5 MVA CB49 CTP-1 315 kW CB50 GBC-1 750 kW CB51 BFP-UB-1(S/B) 1750 kW CB52 BFP-HRSG-1 910 kW CB53 FD FAN-UB-1 1200 kW CB28 CB55CB56 Open BFP-HRSG-2

910 kWBFP-HRSG-3(S/B)910 kW CTP-2(S/B)315 kW

CB58 UAT-6 10.28 %Z 6.6/0.433 kV 2.5 MVA CB57 Open CB59 BFP-UB-3 1750 kW CB60 Open CB61 Open GBC-2(S/B)

750 kWACW-2(S/B)

360 kW CB62CB63 FD FAN-UB-2 1200 kW CB45 UAT-5 10.54 %Z 6.6/0.433 kV2.5 MVA

CB54 UAT-8 10.4 %Z 6.6/0.433 kV 2.5 MVA CB27 CB29Open CB98 Open CB97 CB99 CAP-3 3000 kvar CAP-4 3000 kvar BUS 76 0.415 kV BUS-A(BOARD 4) 0.415 kV LUBE-1 STG-1 90 kW BUS-B(BOARD 4) 0.415 kV LUBE-1 STG-2

90 kWBSCWP-190 kW

BUS-B(BOARD 5) LUBE-2 STG-2

90 kW LUBE-2 STG-1

90 kW

CB286 Open

CB108 Open BOIL -1.

71.9 kVA

CB91 CB92 CB93 CB94 CB95 CB96 CB100 Open

CB101 CB102 CB103CB104 CB344 CB345

CB107 CB109 CB105

CB106 110V UPS-1

144 kVA ACELDB.71.9 kVAACELDB71.9 kVA110 UPS-2144 kVAASB(CUS)71.9 kVA

110V UPS-3 144 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 8 0.415 kV CB110 CB116 Open CB119 Lump11 542 kVA CB120 CB115 CB117 CB122 Lump13 125 kVA CB123 Open Lump12 125 kVA CB121 CB114 LUBE-3 90 kW CB113 BOIL-2 71.9 kVA CB112 LUBE-4 90 kW CB118 BOIL-2. 71.9 kVA 220V DC-1 71.9 kVA BOIL-3

71.9 kVA 220V DC-2

71.9 kVA BOIL-3. 71.9 kVA CB111 Open Lump10 185 kVA Lump9 185 kVA Lump8 460 kVA Lump7 85 kVA Lump6 85 kVA BUS-B(BOARD 6) 0.415 kV BUS-A(BOARD 6) 0.415 kV CB110 CB111 Open CB112 BUS-A(BOARD 5)0.415 kV 0.415 kV

BOARD 8 0.415 kV

BUS-A(BOARD 7)0.415 kV LUBE-3 90 kW BUS-B(BOARD 7) 0.415 kV LUBE-4 90 kW CB123 Open BOIL-2 71.9 kVA BOIL-2. 71.9 kVA

CB113 CB114CB115 CB116Open CB117 CB118 CB120 CB119

CB122 CB121 220V DC-1

71.9 kVA

BOIL-3

71.9 kVA 220V DC-2

71.9 kVA

Lump6

85 kVA Lump785 kVA

Lump8

460 kVA Lump9

185 kVA Lump10185 kVA

Lump12

125 kVA 125 kVALump13

Lump11

542 kVA

BOIL-3.

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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 k

Z

cU

I

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

p

kI

i



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.

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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

current

Fault

=

PSM

...Eqn (3)

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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