JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD

Prerequisite

Power System Protection

Course Objectives:

• To study numerical relays.
• To develop mathematical approach towards protection.
• To study algorithms for numerical protection.

Course Outcomes

After completion of the course, students will be able to:

• Learn the importance of Digital Relays.
• Apply Mathematical approach towards protection.
• Develop various Protection algorithms.

UNIT - I

MATHEMATICAL BACKGROUND TO DIGITAL PROTECTION Overview of static relays, Transmission line protection, Transformer protection, Need for Digital protection. Performance and operational characteristics of Digital protection, Basic structure of Digital relays, Finite difference techniques, Interpolation formulas, Numerical differentiation, Curve fitting and smoothing, Fourier analysis, Walsh function analysis, Relationship between Fourier and Walsh coefficients.

UNIT - II

BASIC ELEMENTS OF DIGITAL PROTECTION Basic components of a digital relay, Signal conditioning subsystems, Conversion subsystem, Digital relay subsystem, The digital relay as a unit.

UNIT - III

DIGITAL RELAYING ALGORITHMS-I Sinusoidal-Wave-Based algorithms: Sample and first-derivative methods, First and second-derivative methods, Two-sample technique, Three-sample technique, an early relaying scheme. Fourier analysis-based algorithms: Full cycle window algorithm, Fractional-cycle window algorithms, Fourier-transform based algorithm, and Walsh-function-based algorithms.

UNIT - IV

DIGITAL RELAYING ALGORITHMS-II Least squares-based methods: Integral LSQ fit, Power series LSQ fit, multi-variable series LSQ technique, Determination of measured impedance estimates. Differential equation-based techniques: Representation of transmission lines with capacitance neglected, Differential equation protection with selected limits, Simultaneous differential equation techniques. Travelling-wave based protection: Fundamentals of Travelling-wave based protection, Bergeron’s- equation based protection scheme, Ultra-high-speed polarity comparison scheme, Ultra-high-speed wave differential scheme, Discrimination function-based scheme, superimposed component trajectory- b a s e d scheme.

UNIT - V

DIGITAL PROTECTION OF TRANSFORMERS AND TRANSMISSION LINES Principles of transformer protection, Digital protection of Transformer using FIR filter-based algorithm, least squares curve fitting-based algorithms, Fourier-based algorithm, and Flux-restrained current differential relay. Digital Line differential protection: Current-based differential schemes, Composite voltage- and current- based scheme.

TEXTBOOKS:

• 1. A.G. Phadke and J. S. Thorp, “Computer Relaying for Power Systems”, Wiley/Research studies Press, 2009.
• 2. A.T. Johns and S. K. Salman, “Digital Protection of Power Systems”, IEEE Press, 1999.

REFERENCES:

• 1. Gerhard Zeigler, “Numerical Distance Protection”, Siemens Publicis Corporate Publishing, 2006.
• 2. S.R.Bhide, “Digital Power System Protection”, PHI Learning Pvt.Ltd, 2014. M. Tech – II Semester L T P C 3 0 0 3