Schweitzer Engineering Laboratories SEL-300G - Negative-Sequence Overcurrent Elements; Element Description; Functional Description; Setting Descriptions

Relay Element Settings 2-35
SEL-300G Instruction Manual Date Code 20020206
X
DWG: M300G048
R
-Xd'
2
40Z1P
40Z2P
XTXT
40DIR
Zone 1
Zone 2
1.1•Xd
Figure 2.18: Loss-of-Field Element Operating Characteristic,
Positive Zone 2 Offset
NEGATIVE-SEQUENCE OVERCURRENT ELEMENTS
Element Description
Functional Description
Generator unbalance current causes high rotor heating. IEEE Standard C50.13: 1977 defined the
ability of generators to withstand unbalance current in terms of negative-sequence current. The
standard defines a continuous withstand capability as well as a short-time capability, expressed
in terms of I
2
2
t.
The SEL-300G Relay provides a negative-sequence definite-time overcurrent element suitable
for unbalance alarm application and an I
2
2
t time-overcurrent element for unbalance current
tripping.
The negative-sequence overcurrent elements are supervised by the 46QTC torque-control setting.
Setting Descriptions
Enable Neg.-Seq. Overcurrent Protection (Y, N) E46 = Y
Set E46 = Y to enable negative-sequence overcurrent elements. If negative-sequence
overcurrent protection is not required, set E46 = N. When E46 = N, the 46QTC, 46Q1,
46Q1T, 46Q2, and 46Q2T Relay Word bits are inactive and the following settings are
hidden and do not need to be entered.