TERMS AND DEFINITIONS Time Behavior of the Short Circuit Current Short Circuit Path in the Positive-Sequence System Classification of Short Circuit Types Methods of Short Circuit Calculation Calculating with Reference Variables GENERAL INFORMATION ABOUT IEC 60 909 THE SIGNIFICANCE OF IEC 60 909 SUPPLY NETWORKS Calculation Variables for Supply Networks Lines Supplied from a Single Source Radial Networks Ringnetworks Meshed Networks NETWORK TYPES FOR THE CALCULATION OF SHORT CIRCUIT CURRENTS Low Voltage Network Types Medium Voltage Network Types SYSTEMS UP TO 1 KV TN Systems Calculation of Fault Currents TT Systems IT Systems Transformation of the Network Types Described to Equivalent Circuit Diagrams NEUTRAL POINT TREATMENT IN THREE-PHASE NETWORKS Networks with Isolated Free Neutral Point Networks with Grounding Compensation Networks with Low Impedance Neutral Point Treatment IMPEDANCES OF THREE-PHASE OPERATIONAL EQUIPMENT Network Feed-Ins Synchronous Machines Transformers Short Circuit Current on the Secondary Side Voltage Regulating Transformers Cables and Overhead Lines Short Circuit Current Limiting Asynchronous Machines Consideration of Capacitors and Non-Rotating Loads Consideration of Static Converters IMPEDANCE CORRECTIONS Correction Factor KG for Generators Correction Factor KKW for Power Plant Block Correction Factor KT for Transformers with Two and Three Wind THE METHOD OF SYMMETRICAL COMPONENTS Symmetrical Components Impedances of Symmetrical Components CALCULATION OF SHORT CIRCUIT CURRENTS Three-Pole Short Circuits Two-Pole Short Circuits with Contact to Ground Two-Pole Short Circuit Without Contact to Ground Single-Pole Short Circuits to Ground Peak Short Circuit Current Ip Symmetrical Breaking Current Ia Steady State Short Circuit Current Ik MOTORS IN THREE-PHASE NETWORKS Short Circuits At the Terminals of Asynchronous Motors Motor Groups Supplied from Transformers with Two Windings Motor Groups Supplied from Transformers with Different Nominal Voltages MECHANICAL AND THERMAL SHORT CIRCUIT STRENGTH Mechanical Short Circuit Current Strength Thermal Short Circuit Current Strength Limitation of Short Circuit Currents CALCULATIONS FOR SHORT CIRCUIT STRENGTH Short Circuit Strength for Medium Voltage Switchgear Short Circuit Strength for Low Voltage Switchgear EQUIPMENT FOR OVERCURRENT PROTECTION Short Circuit Currents in DC Systems Resistances of Line Sections Current Converters Batteries Capacitors DC Motors PROGRAMS FOR THE CALCULATION OF SHORT CIRCUIT CURRENTS EXAMPLES: CALCULATION OF SHORT CIRCUIT CURRENTS Example 1: Radial Network Example 2: Proof of Protective Measures Example 3: Connection Box to Service Panel Example 4: Transformers in Parallel Example 5: Connection of a Motor Example 6: Calculation for a Load Circuit Example 7: Calculation for An Industrial System Example 8: Calculation of Three-Pole Short Circuit Current and Peak Short Circuit Current Example 9: Meshed Network Example 10: Supply to a Factory Example 11: Calculation with Impedance Corrections Example 12: Connection of a Transformer Through An External Network and a Generator Example 13: Motors in Parallel and Their Contributions to the Short Circuit Current Example 14: Proof of the Stability of Low Voltage Systems Example 15: Proof of the Stability of Medium and High Voltage Systems Example 16: Calculation for Short Circuit Currents with Impedance Corrections Example 17: Calculation with Per-Unit Magnitudes Skryť popis