GE D30 Instruction Manual

Also see for D30 series: Communications manual Communications guide Instruction manual Instruction manual Instruction manual

Contents

5-210 D30 LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUALGROUPED ELEMENTS CHAPTER 5: SETTINGS5The negative-sequence voltage must be greater than the VOLTAGE CUTOFF LEVEL setting specified in the PRODUCT SETUP DISPLAY PROPERTIES menu to be validated for use as a polarizing signal. If the polarizing signal is not validated, neitherforward nor reverse indication is given. The following figure explains the usage of the voltage polarized directional unit ofthe element. It shows the phase angle comparator characteristics for a phase A to ground fault, with settings ofECA = 75° (element characteristic angle = centerline of operating characteristic)FWD LA = 80° (forward limit angle = ± the angular limit with the ECA for operation)REV LA = 80° (reverse limit angle = ± the angular limit with the ECA for operation)The element incorporates a current reversal logic: if the reverse direction is indicated for at least 1.25 of a power systemcycle, the prospective forward indication is delayed by 1.5 of a power system cycle. The element emulates anelectromechanical directional device. Larger operating and polarizing signals result in faster directional discrimination,bringing more security to the element operation.Figure 5-115: Negative-sequence directional characteristicThe forward-looking function is designed to be more secure compared to the reverse-looking function, so use the forward-looking function for the tripping direction. The reverse-looking function is faster compared to the forward-looking function,so use the reverse-looking function for the blocking direction. This allows for better protection coordination. Take this biasinto account when using the negative-sequence directional overcurrent element to directionalize other protectionelements. The negative-sequence directional pickup must be greater than the PRODUCT SETUP  DISPLAY PROPERTIES CURRENT CUT-OFF LEVEL setting value.SettingsNEG SEQ DIR OC1 OFFSET — Specifies the offset impedance used by this protection. The primary application for the offsetimpedance is to guarantee correct identification of fault direction on series compensated lines (see the Application ofSettings chapter for information on how to calculate this setting). In regular applications, the offset impedance ensuresproper operation even if the negative-sequence voltage at the relaying point is very small. If this is the intent, the offsetimpedance shall not be larger than the negative-sequence impedance of the protected circuit. Practically, it is severaltimes smaller. Enter the offset impedance in secondary ohms.NEG SEQ DIR OC1 TYPE — Selects the operating mode for the overcurrent unit of the element. The choices are “NegSequence” and “Zero Sequence.” In some applications it is advantageous to use a directional negative-sequenceovercurrent function instead of a directional zero-sequence overcurrent function as inter-circuit mutual effects areminimized.827806A2.CDRVAG (reference)VCG VBG–I_2 lineI_2 lineECA line–ECA lineLALALALA ECAFWD OperatingRegionREV OperatingRegionFWDLAFWDLAREVLAREVLAV_2 line–V_2 line