5-14
Trip and Target Logic
Date Code 20010625
SEL-311L Instruction Manual
relay continues to see zero voltage. The directional elements have no voltage for reference and
cannot operate. In this case, the instantaneous overcurrent element in the SOTF trip logic should
be nondirectional.
C
OMMUNICATIONS
-A
SSISTED
T
RIP
L
OGIC
—G
ENERAL
O
VERVIEW
The SEL-311L Relay includes communications-assisted tripping schemes that provide unit-
protection for transmission lines with the help of communications. No external coordination
devices are required.
Figure 5.6: Communications-Assisted Tripping Scheme
Refer to Figure 5.6 and the top half of Figure 5.4.
The six available tripping schemes are:
v
Direct Transfer Trip (DTT)
v
Direct Underreaching Transfer Trip (DUTT)
v
Permissive Overreaching Transfer Trip (POTT)
v
Permissive Underreaching Transfer Trip (PUTT)
v
Directional Comparison Unblocking (DCUB)
v
Directional Comparison Blocking (DCB)
Summary of Contents for SEL-311L
Page 6: ......
Page 8: ......
Page 26: ......
Page 54: ......
Page 144: ......
Page 216: ......
Page 252: ......
Page 302: ......
Page 338: ......
Page 480: ......
Page 484: ......
Page 486: ......
Page 502: ......
Page 532: ...12 28 Standard Event Reports and SER Date Code 20010625 SEL 311L Instruction Manual 4 ...
Page 552: ......
Page 554: ......
Page 574: ......
Page 576: ......
Page 596: ......
Page 602: ......
Page 628: ......
Page 656: ......
Page 662: ......
Page 664: ......
Page 688: ......
Page 700: ......
Page 716: ......
Page 722: ......
Page 734: ......