CHAPTER 15: THEORY OF OPERATION
SERIES COMPENSATED LINES
D90
PLUS
LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL
651
Figure 555: Dynamic reach, low-current external fault
The following figure illustrates a high-current external fault. The air gaps or MOVs conduct
majority of the fault current and neither steady-state nor transient overreach takes place.
The relay does not reduce its reach as it is not necessary.
Figure 556: Dynamic reach, high-current external fault
The following figure illustrates a high-current internal fault. Because of the large current,
the reach is not reduced and the element responds to the internal fault. A traditional
approach would leave this fault out of the relay reach.
6WHDG\VWDWHDSSDUHQWLPSHGDQFH
5
;
,PSHGDQFHWUDMHFWRU\
7KHUHDFKLVVDIHO\UHGXFHG
6HWUHDFK
=
6& 029
)DUHQG
EXVEDU
5
)
6&
029
$&'5
5
;
,PSHGDQFHWUDMHFWRU\
QRVXEV\QFKURQRXVRVFLOODWLRQV
7KHUHDFKLVQRWUHGXFHG
6HWUHDFK
)DUHQG
EXVEDU
5
)
6&
029
6WHDG\VWDWHDSSDUHQWLPSHGDQFH
$&'5
