The setting of DU> should be set high (approximately 60% of UBase) and thecurrent threshold DI< low (approximately 10% of IBase) to avoid unwantedoperation due to normal switching conditions in the network. The delta current anddelta voltage function shall always be used together with either the negative or zerosequence algorithm. If USetprim is the primary voltage for operation of dU/dt andISetprim the primary current for operation of dI/dt, the setting of DU> and DI< willbe given according to equation 44 and equation 45.DU USetUBaseprim> = 100.EQUATION1523 V3 EN-US (Equation 44)DI ISetIBaseprim< = 100.EQUATION1524 V4 EN-US (Equation 45)The voltage thresholds UPh> is used to identify low voltage condition in thesystem. Set UPh> below the minimum operating voltage that might occur duringemergency conditions. A setting of approximately 70% of UBase is recommended.The current threshold IPh> shall be set lower than the IMinOp for the distanceprotection function. A 5...10% lower value is recommended.10.2.3.6 Dead line detection M13683-78 v4The condition for operation of the dead line detection is set by the parametersIDLD< for the current threshold and UDLD< for the voltage threshold.Set the IDLD< with a sufficient margin below the minimum expected load current.A safety margin of at least 15-20% is recommended. The operate value musthowever exceed the maximum charging current of an overhead line, when only onephase is disconnected (mutual coupling to the other phases).Set the UDLD< with a sufficient margin below the minimum expected operatingvoltage. A safety margin of at least 15% is recommended.Section 10 1MRK 504 169-UEN ASecondary system supervision174 Transformer protection RET650 2.2 IECApplication manual
