Schweitzer Engineering Laboratories SEL-351-5, Instruction Manual

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4.57
Date Code 20070117
Instruction Manual SEL-351-5, -6, -7 Relay
Loss-of-Potential, Load Encroachment, and Directional Element Logic
Directional Control Provided by Torque Control Settings
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 4.4 shows the overcurrent elements that are controlled by each level
direction setting. Note in Table 4.4 that all the time-overcurrent elements
(51_T elements) are controlled by the DIR1 level direction setting. See
Figure 4.17 , Figure 4.18 , Figure 4.23 , and Figure 4.24 .
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
To accomplish this, the DIR1 setting is “turned off,” and the corresponding
SEL
OGIC
control equation torque control settings for the above overcurrent
elements are used to make the elements directional (forward or reverse) or
nondirectional. The required settings are:
DIR1 = N (“turned off”; see Figure 4.17 , Figure 4.18 , Figure 4.23 , and
Figure 4.24 )
67P1TC = 32PF (direction forward; see Figure 3.3 )
67G1TC =
32GF
(direction forward; see Figure 3.10 )
51PTC =
32PF
(direction forward; see Figure 3.14 )
51ATC = 32PR (direction reverse; see Figure 3.15 )
51BTC = 32PR (direction reverse; see Figure 3.16 )
51CTC =
32PR
(direction reverse; see Figure 3.17 )
51NTC =
1
(nondirectional; see Figure 3.18 )
51GTC = 32GF (direction forward; see Figure 3.19 )
This is just one example of using SEL
OGIC
control equation torque control
settings to make overcurrent elements directional (forward or reverse) or
nondirectional. This example shows only Level 1 overcurrent elements
(controlled by level direction setting DIR1). The same setting principles apply
to the other levels as well. Many variations are possible.