Date Code 20010625
Loss-of-Potential, CCVT Transient Detection,
4-5
Load-Encroachment, and Directional Element Logic
SEL-311L Instruction Manual
Figure 4.3: Load-Encroachment Logic with Example Settings
A positive-sequence impedance calculation (Z
1
) is made in the load-encroachment logic in
Figure 4.3. Load is largely a balanced condition, so apparent positive-sequence impedance is a
good load measure. The load-encroachment logic only operates if the positive-sequence current
(I
1
) is greater than the Positive-Sequence Threshold shown in Figure 4.3. For a balanced load
condition, I
1
= phase current magnitude.
Forward load (load flowing out) lies within the hatched region labeled ZLOUT. Relay Word bit
ZLOUT asserts to logical 1 when the load lies within this hatched region.
Reverse load (load flowing in) lies within the hatched region labeled ZLIN. Relay Word bit
ZLIN asserts to logical 1 when the load lies within this hatched region.
Relay Word bit ZLOAD is the OR-combination of ZLOUT and ZLIN:
ZLOAD = ZLOUT + ZLIN
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: ......