Distance Elements Analysis - GE D90 Plus Instruction Manual

Line distance protection system

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CHAPTER 15: THEORY OF OPERATION

Distance elements analysis

LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL

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

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.

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.

DISTANCE ELEMENTS