Figure 354: Operation timer characteristic of IFPTOC function when Operation
principle = “Touch voltage based”, Operating curve type = “Inverse time IEEE80” and
IEEE multiplier = 500. Characteristics are according to standard IEEE80. Maximum
earthing Ris = 10ohm.
Cross-country fault protection
In high impedance earthed networks, single phase earth fault introduces over-
voltages in the healthy phases. Such over-voltages may initiate another single-phase
earth fault in another phase and location in a galvanically connected network. Such
fault condition is commonly known as cross-country fault, which is a two phase
short-circuit through earth with high earth fault current. Cross-country fault must
be therefore quickly disconnected in order to limit risk to health and damages to
equipment.
Protection functions
1MRS759142 F
624 REX640
Technical Manual
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