8.2.3.6 Reservation input (RESIN) M16678-3 v3With the FutureUse parameter set to Bay future use the function can handle baysnot yet installed in the SA system.8.3 Interlocking IP15572-1 v2M13530-4 v4The main purpose of switchgear interlocking is:• To avoid the dangerous or damaging operation of switchgear• To enforce restrictions on the operation of the substation for other reasons forexample, load configuration. Examples of the latter are to limit the number ofparallel transformers to a maximum of two or to ensure that energizing isalways from one side, for example, the high voltage side of a transformer.This section only deals with the first point, and only with restrictions caused byswitching devices other than the one to be controlled. This means that switchinterlock, because of device alarms, is not included in this section.Disconnectors and earthing switches have a limited switching capacity.Disconnectors may therefore only operate:• With basically zero current. The circuit is open on one side and has a smallextension. The capacitive current is small (for example, < 5A) and powertransformers with inrush current are not allowed.• To connect or disconnect a parallel circuit carrying load current. The switchingvoltage across the open contacts is thus virtually zero, thanks to the parallelcircuit (for example, < 1% of rated voltage). Paralleling of power transformersis not allowed.Earthing switches are allowed to connect and disconnect earthing of isolatedpoints. Due to capacitive or inductive coupling there may be some voltage (forexample < 40% of rated voltage) before earthing and some current (for example <100A) after earthing of a line.Circuit breakers are usually not interlocked. Closing is only interlocked againstrunning disconnectors in the same bay, and the bus-coupler opening is interlockedduring a busbar transfer.The positions of all switching devices in a bay and from some other bays determinethe conditions for operational interlocking. Conditions from other stations areusually not available. Therefore, a line earthing switch is usually not fullyinterlocked. The operator must be convinced that the line is not energized from theother side before closing the earthing switch. As an option, a voltage indication canbe used for interlocking. Take care to avoid a dangerous enable condition at theloss of a VT secondary voltage, for example, because of a blown fuse.1MRK 511 423-UEN A Section 8ControlBay control REC650 2.2 IEC 127Application manual
