CHAPTER 9: THEORY OF OPERATION SERIES-COMPENSATED LINESD60 LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL 9-219takes place. The relay does not reduce its reach as it is not necessary. Section (c) shows a high-current internal fault.Because of the large current, the reach is not reduced and the element responds to this internal fault. Traditional approachleaves this fault out of the relay reach.The neutral and negative-sequence directional protection functions of the relay cope with the voltage and/or currentinversions by adding appropriate offset to their polarizing signals as explained in the Ground Directional Overcurrentsection. The offset impedance can always be selected successfully to guarantee correct fault direction discriminationregardless of the degree of compensation and location of the series capacitors and the potential source.See the Application of Settings chapter for recommendations on settings for series compensation applications.
