GE MiCOM P40 Agile Technical Manual

Contents

2.2 UNDERVOLTAGE PROTECTION LOGICV00803VAV<1 Voltage Set &V<1 Time DelayV <1 Trip A/ABV<1 Start A/AB&1&&&1&&11V<1 StartV<1 TripV< Operate ModeAny PhaseThree PhaseV< Measur't ModeVAB&VBV<1 Voltage Set &V<1 Time DelayV<1 Trip B/BCV<1 Start B/BCV< Measur't ModeVBC&VCV<1 Voltage Set &V<1 Time DelayV<1 Trip C/CAV<1 Start C/CAV< Measur't ModeVCA&V<1 Timer BlockV<1 Poledead InhEnabledVTS Fast BlockAll Poles Dead&Note: This diagram does not show all stages . Other stages follow similar principles.VTS Fast Block only applies for directional models .890832414789684790685791686788683Figure 110: Undervoltage - single and three phase tripping mode (single stage)The Undervoltage protection function detects when the voltage magnitude for a certain stage falls short of a setthreshold. If this happens a Start signal, signifying the "Start of protection", is produced. This Start signal can beblocked by the VTS Fast Block signal and an All Poles Dead signal. This Start signal is applied to the timer moduleto produce the Trip signal, which can be blocked by the undervoltage timer block signal (V<(n) Timer Block). Foreach stage, there are three Phase undervoltage detection modules, one for each phase. The three Start signalsfrom each of these phases are OR'd together to create a 3-phase Start signal (V<(n) Start), which can be beactivated when any of the three phases start (Any Phase), or when all three phases start (Three Phase), dependingon the chosen V< Operate Mode setting.The outputs of the timer modules are the trip signals which are used to drive the tripping output relay. Thesetripping signals are also OR'd together to create a 3-phase Trip signal, which are also controlled by the V< OperateMode setting.If any one of the above signals is low, or goes low before the timer has counted out, the timer module is inhibited(effectively reset) until the blocking signal goes high.In some cases, we do not want the undervoltage element to trip; for example, when the protected feeder is de-energised, or the circuit breaker is opened, an undervoltage condition would obviously be detected, but we wouldnot want to start protection. To cater for this, an All Poles Dead signal blocks the Start signal for each phase. Thisis controlled by the V cell, which is included for each of the stages. If the cell is enabled, the relevantstage will be blocked by the integrated pole dead logic. This logic produces an output when it detects either anP14x Chapter 10 - Voltage Protection FunctionsP14xEd1-TM-EN-1 211