unsymmetrical check on the line where the IED connected will give alarm or trip atdetecting broken conductors.6.10.3 Setting guidelinesGlobalBaseSel: Selects the global base value group used by the function to define (IBase),(VBase) and (SBase).Broken conductor check BRCPTOC (46) must be set to detect open phase/s (series faults)with different loads on the line. BRCPTOC (46) must at the same time be set to not operatefor maximum asymmetry which can exist due to, for example, not transposed power lines.All settings are in primary values or percentage.Set minimum operating level per phase Pickup_PH to typically 10-20% of rated current.Set the unsymmetrical current, which is relation between the difference of the minimumand maximum phase currents to the maximum phase current to typical Pickup_ub = 50%.Note that it must be set to avoid problem with asymmetry under minimumoperating conditions.Set the time delay tOper = 5 - 60 seconds and reset time tReset = 0.010 - 60.000 seconds.6.11 Directional over-/under-power protection GOPPDOP/GUPPDUP (32/37)6.11.1 ApplicationThe task of a generator in a power plant is to convert mechanical energy available as atorque on a rotating shaft to electric energy.Sometimes, the mechanical power from a prime mover may decrease so much that it doesnot cover bearing losses and ventilation losses. Then, the synchronous generator becomesa synchronous motor and starts to take electric power from the rest of the power system.This operating state, where individual synchronous machines operate as motors, impliesno risk for the machine itself. If the generator under consideration is very large and if itconsumes lots of electric power, it may be desirable to disconnect it to ease the task for therest of the power system.Section 6 1MRK 511 286-UUS ACurrent protection138Application manual
