CHAPTER 9: THEORY OF OPERATION DISTANCE ELEMENTSD30 LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL 9-79Table 9-5: Non-directional mho phase distance functionsTable 9-6: Non-directional mho ground distance functionsTable 9-7: Non-directional quadrilateral phase distance functionsTable 9-8: Non-directional quadrilateral ground distance functions9.1.4 Fast distance algorithmIn order to improve operating speed of the phase and ground distance zone 1 and zone 2 elements under CVT transientconditions for high SIRs up to 60, a fast distance algorithm is implemented in the relay. This algorithm uses a weightedaverage digital filtering technique and runs in parallel with a regular distance algorithm, which uses a fixed digital CVTfiltering technique. The fast distance algorithm applies the same comparators as a regular distance algorithm.The fast distance algorithm is activated upon detection of the system disturbance and is active for three cycles only. Thepickup and operate operands of the fast distance elements are internally OR-ed with regular distance elements, to achieveintegrated distance element optimal operating speed.Note that fast distance is not active for the following applications:• Use of the dynamic reach control for series-compensated line applications by selecting a non-zero value for thevoltage level setting in the Distance elements• Non-directional option for the zone 1 and 2 Direction setting• Phase Distance applications through power transformers, when the XFMR VOL CONNECTION or XFMR CURCONNECTION setting is other than "None"9.1.5 Memory polarizationAll distance functions use memory polarization. The positive-sequence voltage, either memorized or actual, is used as apolarizing signal. The memory is established when the positive-sequence voltage remains above 80% of its nominal valuefor five power system cycles. The memory voltage is a two-cycle old voltage.Characteristic Comparator inputs Limit angleOffset mho I × Z – V V-I × Z REV COMP LIMITFault type NOT SLG See the Fault Type Characteristic section Removed during open pole conditionsCharacteristic Comparator inputs Limit angleOffset mho I × Z – V V-I × ZREV COMP LIMITFault-type I_0 I_2 50°Characteristic Comparator inputs Limit angleForward Reactance I × Z – V I × Z COMP LIMITReverse Reactance I × Z REV – V I × Z REV COMP LIMITRight Blinder I × Z R – V I × Z R 90°Left Blinder I × Z L – V I × Z L 90°Fault type NOT SLG See the Fault Type Characteristic section Removed during open pole conditionsCharacteristic Comparator inputs Limit angleForward Reactance I × Z – V j × I_0 × e jΘ or j × I_2× e jΘ COMP LIMITReverse Reactance I × ZREV – V –j × I_0 × e jΘ or –j ×I_2 × e jΘ COMP LIMITRight Blinder I × ZR – V I × ZR 90°Left Blinder I × ZL – V I × ZL 90°Fault-type I_0 I_2 50°
