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Tham khảo tài liệu 'power quality monitoring analysis and enhancement part 9', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Single-Point Methods for Location of Distortion Unbalance Voltage Fluctuation and Dips Sources in a Power System 187 to the substation A busbars. This results from significant differences in the lines lengths and may occur in real systems. No. of the distance protection Impedance under normal operating conditions Impedance under disturbance conditions module Q argument deg module Q argument deg Z1 262.1 298.0 12.7 210.2 Z2 57.5 27.8 2.9 22.1 Z3 53.4 194.5 3.8 200.4 Table 2. Fault in the middle of line F2 No. of the distance protection Impedance under normal operating conditions Impedance under disturbance conditions module Q argument deg module Q argument deg Z1 183.7 347.1 48.2 192.6 Z2 X X Z3 183.5 167.4 48.2 12.9 Table 3. Fault at the origin of line 3 F3 - line 2 disconnected No. of the distance protection Impedance under normal operating conditions Impedance under disturbance conditions module Q argument deg module Q argument deg Z1 262.1 298.0 13.8 48.5 Z2 57.5 27.8 37.0 246.9 Z3 53.4 194.5 22.0 214.7 Table 4. Fault at the origin of line 1 F1 No. of the distance protection Impedance under normal operating conditions Impedance under disturbance conditions module Q argument deg module Q argument deg Z1 262.1 298.0 87 209.7 Z2 57.5 27.8 25.3 184.1 Z3 53.4 194.5 19.9 9.8 Table 5. Fault at the origin of line 3 F3 The method correctness depends to a large extent on the system configuration and this dependence results from the method of operation of the distance protection. 3.8 Vector-space approach 28 The testing of all these methods show that in cases of asymmetrical voltage dips they are rather ineffective. Furthermore al the discussed methods except the energy based one require computation of voltage and current phasors for the fundamental-frequency component. 188 Power Quality - Monitoring Analysis and Enhancement Because voltage dips are transient disturbance events all phasor-based methods might produce questionable results due to inherent averaging in the .
