Schweitzer Engineering Laboratories SEL-311A, Instruction Manual

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Date Code 20011205 Loss-of-Potential, CCVT Transient Detection, 4-1
Load-Encroachment, and Directional Element Logic
SEL-311A Instruction Manual
SECTION 4: LOSS-OF-POTENTIAL, CCVT TRANSIENT
DETECTION, LOAD-ENCROACHMENT, AND
DIRECTIONAL ELEMENT LOGIC
L
OSS
-
OF
-P
OTENTIAL
L
OGIC
The loss-of-potential (LOP) logic operates as shown in Figure 4.1.

From Figure 5.3
‚
To Figure 3.4 through Figure 3.7,
Figure 4.9 through Figure 4.11,
Figure 4.14, and Figure 4.15
Figure 4.1: Loss-of-Potential Logic
Inputs into the LOP logic are:
3PO three-pole open condition (indicates circuit breaker open condition
see Figure 5.3)
V
1
positive-sequence voltage (V secondary)
I
1
positive-sequence current (A secondary)
V
0
zero-sequence voltage (V secondary)
I
0
zero-sequence current (A secondary)
The circuit breaker has to be closed (Relay Word bit 3PO = logical 0) for the LOP logic to
operate.