Date Code 20001006 Loss-of-Potential, Load Encroachment, and Directional Element Logic 4-35
SEL-351 Instruction Manual
Most often, this setting is set directly to logical 1:
E32IV = 1 (numeral 1)
For situations where zero-sequence source isolation can occur (e.g., by the opening of a circuit
breaker) and result in possible mutual coupling problems for the zero-sequence voltage-polarized
and channel IN current-polarized directional elements, SELOGIC Control Equation setting E32IV
should be deasserted to logical 0. In this example, this is accomplished by connecting a circuit
breaker auxiliary contact from the identified circuit breaker to the SEL-351 Relay:
E32IV = IN6 (52a connected to optoisolated input IN6)
Most any desired control can be set in SELOGIC Control Equation setting E32IV.
DIRECTIONAL CONTROL PROVIDED BY TORQUE CONTROL SETTINGS
For most applications, the level direction settings DIR1 through DIR4 are used to set overcurrent
elements direction forward, reverse, or nondirectional. Table 4.1 shows the overcurrent elements
that are controlled by each level direction setting. Note in Table 4.1 that all the time-overcurrent
elements (51_T elements) are controlled by the DIR1 level direction setting. See Figure 4.12,
Figure 4.17, and Figure 4.18.
In most communications-assisted trip schemes, the levels are set as follows (see Figure 5.4):
Level 1 overcurrent elements set direction forward (DIR1 = F)
Level 2 overcurrent elements set direction forward (DIR2 = F)
Level 3 overcurrent elements set direction reverse (DIR3 = R)
Suppose that the Level 1 overcurrent elements should be set as follows:
67P1 direction forward
67G1 direction forward
51PT direction forward
51AT direction reverse
51BT direction reverse
51CT direction reverse
51NT nondirectional
51GT direction forward
Courtesy of NationalSwitchgear.com
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