MODERN PROTECTIVE RELAYING: Fault Analysis, Relay Coordination, and Numerical Protection in Electric Power Systems

A relay that trips the wrong breaker did exactly what it was told. Protection systems rarely fail because a relay broke. They fail because a number was wrong. A fault current calculated on the wrong base. A ratio that saturates under offset. A zone that reaches past the far bus. A pickup set above the smallest fault the relay is supposed to see. The device then follows its settings faithfully, and a line stays energised that should have been cleared, or a healthy feeder goes dark. Most books stop short of that chain. The academic texts derive the characteristics. The field handbooks list the criteria. Very few walk the arithmetic from a fault study, through an instrument transformer, to a number you can enter in a settings file and defend six months later. The gap shows up two ways. A student learns the impedance plane and the sequence networks, passes the course, and still cannot say where a Zone 2 reach comes from. An engineer inherits a settings file nobody can reconstruct, so every proposed change becomes a negotiation with a document instead of an argument from a calculation. This book builds the chain in the order the subject depends on. Fault analysis first, because no setting exists without fault current. Instrument transformers next, because a relay only sees what the current and voltage transformers hand it. Then the relay functions, simplest to most complex, each derived from its measurement principle rather than asserted. What you will be able to calculate Balanced and unbalanced fault currents on a real network, carried forward into settings Current transformer saturation under offset, and a ratio and accuracy class that will not lose the fault Pickup, time dial and instantaneous elements that grade at both ends of the current range Three-zone distance reach with ground compensation, corrected for infeed Differential slopes and harmonic restraint that survive inrush and through-fault current What a relay measured, decided and did, reconstructed from its own event record A coordination study from input data through to a signed setting register What is inside Sixteen chapters run from power system structure and protective zones through relay technology, balanced and unbalanced fault analysis, current and voltage transformers, overcurrent, distance and pilot protection, and the differential protection of transformers, buses, generators and motors, into coordination studies, numerical settings, testing and event analysis, the digital substation, and adaptive protection under inverter-based generation. Four appendices carry the device function number tables, the standard inverse-time curve equations, a per-unit review and the sequence transformation reference. One three-bus system runs through the whole book. Every element is set on it, tabulated, and commissioned by the closing chapters, so the calculations connect instead of sitting in isolation. Worked examples show every step with units tracked, and practice problems are answerable from the chapter with the answers worked in full. The scope is stated openly: protective relaying for the bulk electric system. Power electronics, direct-current protection, relay hardware design, excitation systems and substation civil work are left to books written for them. Written for upper-level and graduate electrical engineering students, for protection and control engineers, for planning and operations engineers who must read what a relay did, and for instructors who need worked examples and problem sets. Start with the fault study. The settings follow from there.