The positions of all switching devices in a bay and from some other bays determine theconditions for operational interlocking. Conditions from other stations are usually notavailable. Therefore, a line grounding switch is usually not fully interlocked. The operatormust be convinced that the line is not energized from the other side before closing thegrounding switch. As an option, a voltage indication can be used for interlocking. Takecare to avoid a dangerous enable condition at the loss of a VT secondary voltage, forexample, because of a blown fuse.The switch positions used by the operational interlocking logic are obtained fromauxiliary contacts or position sensors. For each end position (open or closed) a trueindication is needed - thus forming a double indication. The apparatus control functioncontinuously checks its consistency. If neither condition is high (1 or TRUE), the switchmay be in an intermediate position, for example, moving. This dynamic state maycontinue for some time, which in the case of disconnectors may be up to 10 seconds.Should both indications stay low for a longer period, the position indication will beinterpreted as unknown. If both indications stay high, something is wrong, and the state isagain treated as unknown.In both cases an alarm is sent to the operator. Indications from position sensors shall beself-checked and system faults indicated by a fault signal. In the interlocking logic, thesignals are used to avoid dangerous enable or release conditions. When the switching stateof a switching device cannot be determined operation is not permitted.For switches with an individual operation gear per phase, the evaluation must considerpossible phase discrepancies. This is done with the aid of an AND-function for all threephases in each apparatus for both open and close indications. Phase discrepancies willresult in an unknown double indication state.15.4.1 Configuration guidelinesThe following sections describe how the interlocking for a certain switchgearconfiguration can be realized in the IED by using standard interlocking modules and theirinterconnections. They also describe the configuration settings. The inputs for deliveryspecific conditions (Qx_EXy) are set to 1=TRUE if they are not used, except in thefollowing cases:• 989_EX2 and 989_EX4 in modules BH_LINE_A and BH_LINE_B• 152_EX3 in module AB_TRAFOwhen they are set to 0=FALSE.15.4.2 Interlocking for line bay ABC_LINE (3)Section 15 1MRK 506 369-UUS -Control700 Line distance protection REL670 2.2 ANSIApplication manual
