Peak-to-peak with peak backupThe peak-to-peak with peak backup measurement principle is selected with theMeasurement mode setting using the value "P-to-P+backup". It is similar to the peak-to-peak mode, with the exception that it has been enhanced with the peak backup. Inthe peak-to-peak with peak backup mode, the function starts with two conditions: thepeak-to-peak value is above the set start current or the peak value is above two timesthe set Start value. The peak backup is enabled only when the function is used in theDT mode in high and instantaneous stages for faster operation.Wide peak-to-peakThe wide peak-to-peak measurement principle is available in products where it isnecessary for overcurrent protection to operate already starting from as low frequencyas 2 Hz during the generator start-up or shutdown phase. The wide peak-to-peakmeasurement principle is selected with the Measurement mode setting "Wide P-to-P".The measurement mode calculates the average from the positive and negative peakvalues over the 500 ms wide measurement window, independently of the Frequencyadaptivity setting value. Retardation and reset times are longer due to the length of themeasurement window. The frequency of the fault current affects the operate time. Thedamping of the harmonics is quite low and practically determined by thecharacteristics of the anti-aliasing filter of the protection relay current inputs.When using measurement mode “Wide P-to-P”, the protection relayaccepts only Operate delay time setting value 800 ms or longer andOperating curve type 5=”ANSI Def. Time” or 15=”IEC Def. Time”.These settings should be used for all six setting groups. If the settingsare applied only in the active setting group, the validation is notsatisfied and the setting commit fails.Operation accuracy in the frequency range 2...85 Hz is ±1.5% or ±0.003 xIn. Operatetime accuracy in definite time mode is ±1.0% of the set value or ±60 ms when IFault = 2⋅ set Start value and the fault current frequency is 10...85 Hz.11.7 Calculated measurementsCalculated residual current and voltageThe residual current is calculated from the phase currents according to equation:Io I I IA B C= − + +( )GUID-B3A734AA-7F26-4138-834A-25E953C023C7 V1 EN (Equation 366)The residual voltage is calculated from the phase-to-earth voltages when the VTconnection is selected as “Wye” with the equation:Section 11 1MRS759142 CGeneral function block features1706 REX640Technical Manual
