【正文】 e or impedance between two or more points of a circuit which are normally at different potentials. ? Short circuit current: According to IEC 60 909, a short circuit current results from a short circuit in an electrical work. It is necessary to differentiate here between the short circuit current at the position of the short circuit and the transferred short circuit currents in the work branches. ? Initial symmetrical short circuit current: This is the effective value of the symmetrical short circuit current at the moment at which the short circuit arises, when the short circuit impedance has its value from the time zero. ? Initial symmetrical short circuit apparent power: The short circuit power represents a fictitious parameter. During the planning of works, the short circuit power is a suitable characteristic number. ? Peak short circuit current: The largest possible momentary value of the short circuit occurring. ? Steady state short circuit current: Effective value of the initial symmetrical short circuit current remaining after the decay of all transient phenomena. ? DC aperiodic ponent: Average value of the upper and lower envelope curve of the short circuit current, which slowly decays to zero. ? Symmetrical breaking current: Effective value of the short circuit current which flows through the contact switch at the time of the first contact separation. ? Equivalent voltage source: The voltage at the position of the short circuit, which is transferred to the positivesequence system as the only effective voltage and is used for the calculation of the short circuit currents. ? Superposition method: The superposition method considers the previous load of the work before the occurrence of the short circuit. It is necessary to know the load flow and the setting of the transformer step switch. ? Voltage factor: Ratio between the equivalent voltage source and the work voltage Un,divided by 3. ? Equivalent electrical circuit: Model for the description of the work by an equivalent circuit. ? Farfromgenerator short circuit: The value of the symmetrical AC periodic ponent remains essentially constant. ? Neartogenerator short circuit: The value of the symmetrical AC periodic ponent does not remain constant. The synchronous machine first delivers an initial symmetrical short circuit current which is larger than twice the rated current of the synchronous machine. ? Positivesequence short circuit impedance: The impedance of the positivesequence system as seen from the position of the short circuit. ? Negativesequence short circuit impedance: The impedance of the negativesequence system as seen from the position of p the short circuit. ? Zerosequence short circuit impedance The impedance of the zerosequence system as seen from the position of the short circuit. Three times the value of the neutral point to ground impedance occurs here. ? Short circuit impeda