RXRLdRLd LdAngleLdAngleLdAngleLdAngleen06000404_ansi.vsdANSI06000404 V1 ENFigure 127: Load encroachment of Faulty phase identification with loadencroachment for mho function FMPSPDIS (21) characteristicThe use of the load encroachment feature is essential for long heavy loaded lines, wherethere might be a conflict between the necessary emergency load transfer and necessarysensitivity of the distance protection. The function can also preferably be used on heavyloaded medium long lines. For short lines the major concern is to get sufficient faultresistance coverage and load encroachment is not a major problem. So, for short lines, theload encroachment function could preferably be switched off.The main settings of the parameters for load encroachment are done in Faulty phaseidentification with load encroachment for mho function FMPSPDIS (21). The operationof load encroachment function is always activated. To deactivate the function, settingLoadEnchMode should be set off or the setting of RLdFw and RLdRv must be set to a valuemuch higher than the maximal load impedance.8.4.2.5 Short line applicationThe definition of short, medium and long lines is found in IEEE Std C37.113-1999. Thelength classification is defined by the ratio of the source impedance at the protected line’sterminal to the protected line’s impedance (SIR). SIR’s of about 4 or greater generallydefine a short line. Medium lines are those with SIR’s greater than 0.5 and less than 4.Section 8 1MRK 506 369-UUS -Impedance protection258 Line distance protection REL670 2.2 ANSIApplication manual
