ABB RET670 Applications Manual page 272

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IED application

ANSI06000404 V1 EN

Load encroachment of Faulty phase identification with load

encroachment for mho function FMPSPDIS (21) characteristic

The use of the load encroachment feature is essential for long heavy loaded lines,

where there might be a conflict between the necessary emergency load transfer and

necessary sensitivity of the distance protection. The function can also preferably be

used on heavy loaded medium long lines. For short lines the major concern is to get

sufficient fault resistance coverage and load encroachment is not a major problem. So,

for short lines, the load encroachment function could preferably be switched off.

The main settings of the parameters for load encroachment are done in Faulty phase

identification with load encroachment for mho function FMPSPDIS (21). The

operation of load encroachment function is always activated. To deactivate the

function, setting LoadEnchMode should be set off or the setting of RLdFw and RLdRv

must be set to a value much higher than the maximal load impedance.

Short line application

The definition of short, medium and long lines is found in IEEE Std C37.113-1999.

The length classification is defined by the ratio of the source impedance at the

protected line's terminal to the protected line's impedance (SIR). SIR's of about 4 or

greater generally define a short line. Medium lines are those with SIR's greater than

0.5 and less than 4.

en06000404_ansi.vsd

1MRK504116-UUS C

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