Method and apparatus for detecting flashover between conductors in power transmission lines of different voltage levels suspended in parallel from the same towers

Apparatus for detecting a flashover between conductors in power transmission lines of different voltage levels suspended from the same towers, comprising:

• a power network comprising the power lines and wherein one of the power lines is a high voltage power line and the other power lines are connected to the high voltage power line via transformers of a known transformer ratio (am) and internal impedance (ZXm), and wherein the line impedances (ZL) are known;
• a flashover indicating means (CALC) storing the known transformer ratios (am), the line impedances (ZL) and the internal impedances (ZXm) for determining the occurrence of a flashover;
• said flashover indicating means receiving the phase currents I1 and phase voltages U1 of the high voltage line and detecting a current change I1 in any of the phases in the high voltage line and calculating the following parameters:
• ##EQU2## where .alpha., .beta., .phi. and .gamma. may be R-, S- or t-phase and n.multidot.ZL is the line impedance from the measuring station to the fault location (F) at the relative distance to fault n, whereby fault n can be determined;
• and
• said flashover determining means generates a signal IF for indicating that a flashover has occurred within the protective zone if 0<n<1.