GE D90 Plus - Distance Elements Analysis

CHAPTER 15: THEORY OF OPERATION DISTANCE ELEMENTS
D90
PLUS
LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL 637
Figure 552: Dynamic shift of the memory-polarized quadrilateral characteristic
Mutual zero-sequence compensation can raise concerns regarding directional integrity on
reverse faults in the situation when the relay gets overcompensated. This problem does not
affect the D90
Plus
because its ground distance elements use zero-sequence and negative-
sequence currents in extra directional comparators. Both the currents are from the
protected line and are not affected by any compensation as the latter applies only to the
reach defining comparators: the mho, reactance, and blinder characteristics.
Distance elements analysis
This subsection shows how to analyze the operation of the distance elements in steady
states using the results of short circuit studies. All quantities are secondary ohms, volts,
and amperes. Ground phase A and phase AB distance elements are analyzed. Assume the
following settings have been entered in the Settings > Protection > Elements > Group 1 >
Ground Distance menu.
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;
5
0HPRU\SRODUL]HG
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6HOISRODUL]HG
0HPRU\SRODUL]HG
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