CHAPTER 4: SETPOINTS FLEXLOGIC889 GENERATOR PROTECTION SYSTEM – INSTRUCTION MANUAL 4–391Pickup = 0.5MVA / 15.936 MVA = 0.0313 puFlexElement settings:• Input 1(+): Pwr1 Apparent• Input 2(-): Off• Operating Mode: Absolute• Input Comparison Mode: Level• Direction: Under• Pickup: 0.0313 puPower Factor Cap Bank Switch-In ExamplePFBASE = 1.00FlexElement can be programmed to switch-in cap bank, if for example the measured 3PhPower Factor has negative value(lag), and drops below the pickup of -0.7 pu. Programmingthe Hysteresis setpoint to the desired percentage can define the PF value at which the capbank can be switched off. For example, if the cap bank is required to be switched off at PFvalue of -0.9, than the percent hysteresis is computed as:% hysteresis = ((abs(-0.9)-abs(-0.7))/ PFBASE)*100 = 20%FASTPATH:The minimum pickup should not be less than 0.01 pu, as the measurement resolution forthe Power Factor is 0.01.• Input 1(+): Pwr1 PF• Input 2(-): Off• Operating Mode: Signed• Input Comparison Mode: Level• Direction: Under• Pickup: -0.700 pu• Hysteresis: 20.0 %Detecting high THD (Total Harmonic Distortion)THDBASE = 100%A FlexElement can be programmed to detect excessive amount of harmonics in thesystem, and Alarm, Trip, or switch-in/out an equipment to suppress the high amount ofharmonics. The Total Harmonic Distortion is an estimation of how the AC signals aredistorted and as shown above, it can be used as an input for the FlexElement.For example if an operation from a FlexElement is desired when the THD for the phase Avoltage exceeds 20%, then having a base of 100%, the pickup setting should be set to0.200 pu.• Input 1(+): J2 Phase A THD• Input 2(-): Off• Operating Mode: Absolute• Input Comparison Mode: Level• Direction: Over• Pickup: 0.200 puFASTPATH:The harmonics and THD values are measured as percentage of the fundamental signal,and have resolution of 0.01%. However for the minimum pickup setting of 0.001 pu, thiswould mean percentage step of 0.1%.Simple V/Hz ratio detection for protected equipmentV/HzBASE = 1.00High V/Hz ratios in the power system are harmful for the insulation of theprotected equipment – transformer, generator, or elsewhere in the power system. If notdetected, it can lead to excessive heat and degradation of the insulation which will
