Schweitzer Engineering Laboratories SEL-311A, Instruction Manual

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4-10 Loss-of-Potential, CCVT Transient Detection, Date Code 20011205
Load-Encroachment, and Directional Element Logic
SEL-311A Instruction Manual
Directional Element Enables
Refer to Figure 4.5, Figure 4.6, and Figure 4.7.
The directional element enables, Relay Word bits 32QGE, 32VE, and 32IE have the following
correspondence to the directional elements:
32QGE Negative-sequence voltage-polarized directional element
32VE Zero-sequence voltage-polarized directional element
32IE Channel IP current-polarized directional element
Note that Figure 4.6 has extra directional element enable 32QE, which is used in the logic that
controls phase distance elements (see Figure 4.14).
The settings involved with 32QGE, 32VE, and 32IE in Figure 4.6 and Figure 4.7 (e.g., settings
a2, k2, a0) are explained in the following subsection
Directional Control Settings .
Best Choice Ground Directional Logic
Refer to Figure 4.5 and Figure 4.8.
Relay Word bits 32QGE, 32VE, and 32IE and setting ORDER are used in the Best Choice
Ground Directional logic in Figure 4.8. The Best Choice Ground Directional logic determines the
order in which the directional element should be enabled to operate. The ground distance and
residual ground overcurrent elements set for directional control are then controlled by this
directional element.
Directional Elements
Refer to Figure 4.5, Figure 4.9, Figure 4.10, and Figure 4.11.
The enable output of Best Choice Ground Directional logic in Figure 4.8 determines which
directional element will run.
Additionally, note that if enable setting ELOP = Y or Y1 and a loss-of-potential condition occurs
(Relay Word bit ILOP asserts), the negative-sequence voltage-polarized and zero-sequence
voltage-polarized directional elements are disabled (see Figure 4.9 and Figure 4.10).
The channel IP current-polarized directional element does not use voltage in making direction
decisions, thus a loss-of-potential condition does not disable the element, but rather aids in
enabling it. When the internal enable 32IE is asserted, the channel IP current-polarized
directional element (Figure 4.11) is enabled if enable setting ELOP = Y or Y1 and a loss-of-
potential condition occurs (Relay Word bit ILOP asserts).
Refer to Figure 4.1 and accompanying text for more information on loss-of-potential.
Directional Element Routing
Refer to Figure 4.5 and Figure 4.12.
The directional element outputs are routed to the forward Relay Word bit 32GF.