This paper presents the modeling and simulation of a 25 kV 50 Hz AC traction system using Power System Block set (PSB) / SIMULINK software package. The three-phase system with substations, track section with rectifier-fed DC locomotives and a detailed traction load are included in the model. The model has been used to study the effect of loading and fault conditions in 25 kV AC traction. The relay characteristic proposed is a combination of two quadrilaterals in the X-R plane. A brief summary of the hardware setup used to implement and test the relay characteristic using a Texas Instruments TMS320C50 digital signal processor (DSP) has also been presented.

Abstruct-This paper presents the design, implementation and testing of a single-phase distance relaying scheme for 25 kV 50 Hz AC traction system using a Texas Instruments TMS320C50 digital signal processor @SP), The three-phase system with substations, track section with rectifier-fed DC locomotives and a detailed traction load are modeled using Power System Block set (PSB) I SlMULlNK software package. The model has been used to study the effect of loading and fault conditions in 25 kV AC traction. The relay characteristic proposed is a combination of two quadrilaterals in the X-R plane in which resistance and reactance reaches are independentiy controllable. The algorithms, hardware and software are also briefly described.

Abstruc&The presence of Flexible AC Transmisston System (FACTS) devices in the loop significantly affects the apparent resistance and reactance seen by a distance relay, as FACTS devices respond to changes in the power system configuration. The objective of this paper is to investigate the effect of mid-point compensation of STATic synchronous COMpensator (STATCOM) on the performance of impedance distance relay under normal load and fault conditions and to implement the adaptive distance relaying scheme for transmission line protection. From the simulation studies carried out in PSCAD software and using andyticd calcdations, it is identified that there 1s a need €or the distance relay to adapt to the new setlings in its characteristic for the detection of fault within the zone of protection of transmission line. Apparent impedance is simulated for different loading and h e to ground (L-G) fault cooditlons at different Iocations on the power system network. The proposed adaptive distance relay scheme has been implemented on TMS320C50 Digital Signal Processor @SP) system. Index Terms-Apparent impedance, distance relays, DSP processor TMS320C50, Fourier algorithm, PSCAD/EMTDC, quadrilateral characteristics and STATCOM. J.V.V.N Bapiraju is with the Department of Electrical Engg., Indian Institute of Science, Bangdore-560 012 @apiraju~ce.iisc.emet.in). U.J.Shenoy, corresponding author is with the Department of Electrical Engg., Indian Institute of Science, Bangalore-560 012 (ui@,ee.iisc.met.inJ KO. Sheshadri is with the Department of Electrical E m . , Indian ldstitute of Science, Bangalore-560 012 (kg_sheshadri@!yabw.com ). H.P. Kincha is with the Department of Electrical Engg.. Indian Institute of Science, Bangalore-560 0 12 (hpk@ee.iisc .emet. in). D. 7hukamm is with the Deparbnent of Electrical Engg., Indian Institute of Science, Bangalore-560 012 (dtram~ce.iisc.ernet.iab I = (P -jQ)/F'* Z = v * / ( P -j Q ) Ra = (V' . P ) / ( P2 + Q2 X, = ( Y 2 . Q ) / ( P 2 + Q ' )Variation of resistance and reactance with respect to reactive power demand for a constant active power demand can be calculated using equations given in (5) and (6). (51 AXo = { V 2 .(Pz -Q 2 ) / ( P 2 +Qz)2).(AQ) 0-7803461 0-8JOU$20.00 0 2004 IEEE