Cheng-Ting Hsu

Presenter: Cheng-Ting Hsu

Cogeneration System Design for a Cogeneration System Design for a High-Tech Science-Based Industrial Park High-Tech Science-Based Industrial Park

Department of Electrical EngineeringSouthern Taiwan University of Technology

Tainan, Taiwan

˙Introduction

˙System Configurations of Cogeneration Facility

˙Short Circuit Analysis

˙Mathematical Modeling of Cogeneration Units

˙Protective Relay Setting for Tie Line

˙Load Shedding Scheme

˙Computer Simulation by Transient Stability Analysis

˙Conclusion

Outline

Introduction

• With so many semiconductor manufacturers in the science-based industrial park, power quality and service reliability have always been the critical issues for the industrial customers.

• This paper presents the proper design of protective relay settings for tie line tripping and load shedding of a cogeneration system in a high-tech science-based industrial park.

System Configurations of Cogeneration Facility

Bus902

Bus903

Three Operation Modes of the Cogeneration System  

Operation Modes

GTG1(MW)

GTG2(MW)

GTG3(MW)

STG(MW)

Total Gen.(MW)

Total Load(MW)

3G1S 45 45 45 26.9 161.9 151.9

2G1S 45 45 OFF 26.9 116.9 151.9

1G1S 45 OFF OFF 26.9 71.9 151.9

Short Circuit Analysis

 

The Short Circuit Current at Long-Song SubstationCases Total fault

current (kA)Fault current supplied by cogeneration (kA)

with 161/161 kV transformers

I"k39.588 1.566

Iasym63.34 -

Ipeak106.89 -

Ib 39.584 1.564without 161/161 kV

transformersI"k

40.425 2.512

Iasym64.68 -

Ipeak109.15 -

Ib 40.403 2.494

Mathematical Modeling of Cogeneration Units

• Generator Model

• Excitation System Model

• Governor System Model

Governor Model of Cogeneration Units

Gas Turbine

Steam Turbine

Protective Relay Setting for Tie Line

• 27 relay: 0.65pu • 81L relay: 58.4 Hz with 0.1second time delay

Load Shedding Scheme

 

.u.pm60

H2

dt

dH2P 0

0step

where m0 is the initial frequency decay rate at the tie line trippingH = 4.4pu for 3G1S = 3.36pu for 2G1S = 2.32pu for 1G1S

Computer Simulation by Transient Stability Analysis

• Case A: A three-phase bolted fault is assumed to occur at Long-Song substation and the relay 27 of the cogeneration system is activated to trip the

tie line in 0.1 second after the fault.

• Case B: A short circuit contingency with fault impedance

of 6.22ohm occurs at Long-Song substation.

• Case C: A far distance fault at TPC system is assumed and the relay 81L of the cogeneration is activated to trip the tie line.

Case AA three-phase bolted fault is occurred at Long-Song substation

and the under voltage relay of the cogeneration system

is activated to trip CB H1 and H2 in 0.1 second. . F

H1 H2

Bus 903

Bus 932

Bus 903

Bus 932

Case BA short circuit contingency with fault impedance occurs

at Long-Song substation. The cogeneration is operated

in 3G1S mode.

Bus 903

Case CA far distance fault is assumed and the relay 81L of the

cogeneration is activated at 58.4Hz to trip the tie line. The

cogeneration system is operated in 3G1S, 2G1S and 1G1S modes.

Gas turbine

Steam turbine

• With the series 161/161 kV transformers, the short circuit current provided by the cogeneration system will be less than 2kA to meet the operational criterion.

• With the series 161/161 kV transformers, the critical clearing time and the residual voltage at customer load buses can be both enhanced.

• By applying the designed protective relay settings for tie line tripping and load shedding, the isolated cogeneration system will be restored to stable operation after transient disturbances introduced by utility faults.

Conclusions