IMPROVED LOSS OF POTENTIAL DETERMINATION FOR USE IN PROTECTIVE RELAYS FOR ELECTRIC POWER SYSTEMS

摘要

The positive sequence voltage on the power line is measured at a given time, i.e. the present time, and also for one cycle earlier, and the ratio thereof is then compared against a threshold value of 0.9. There are four other supervisory tests which also must be true for a loss of potential condition to be indicated. These include determination of change in positive sequence current and angle and zero sequence current and angle. If the change in those values is smaller than selected thresholds, then a loss of potential condition is indicated.