Schweitzer Engineering Laboratories SEL-700G Series, Инструкция по эксплуатации

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4.133
Date Code 20170814 Instruction Manual SEL-700G Relay
Protection and Logic Functions
Group Settings (SET Command)
Adjust the final setting value of a0N from the above derived value of a0N,
depending on your security philosophy, etc. The a0N factor increases the
security of the zero-sequence voltage-polarized directional element. It keeps
the elements from operating for zero-sequence current as a result of any
system unbalance.
High-Impedance Grounded System Considerations for Phase-to-Phase
or Three-Phase Faults
On high-impedance grounded systems (when setting ORDERX := U), phase-
to-phase or unbalanced three-phase faults can cause the high-impedance
grounded element to operate on false quantities. To prevent this situation,
consider 67N element for example, use the SEL
OGIC
torque control equation
50N1TC as follows:
50N1TC := 59V1X1 AND NOT DIRQEX
The positive-sequence over-voltage element in the above torque-control
equation is set to 75% of nominal voltage considering DELTAY_X := WYE,
PTRX := 100, VNOM_X := 11.6 kV (line-line).
59V1X1P := 50.23 V (75%*11.6kV/(1.732*PTRX)
The 59V1X1 Relay Word bit deasserts during a three-phase fault, and the
DIRQE Relay Word bit asserts during a phase-to-phase fault. If either one of
these occur, the 50N1TC setting evaluates to logical 0, and the high-
impedance grounded directional element is blocked.
Directional Control Provided by Torque Control Settings
For most applications, the level direction settings DIR1 and DIR2 are used to
set overcurrent elements direction forward, reverse, or nondirectional.
Table 4.33 shows the overcurrent elements that are controlled by each level
direction setting. Note in Table 4.33 that all the time-overcurrent elements
(51_T elements) are controlled by the DIR1 level direction setting. See
Figure 4.83, Figure 4.84, Figure 4.89, and Figure 4.90.
Suppose that you need to set the Level 1 overcurrent elements as follows:
To accomplish this, the DIR1 setting is “turned off”, and the corresponding
SEL
OGIC
control equation torque control settings for the previous overcurrent
elements are used to make the elements directional (forward or reverse) or
nondirectional. The necessary settings are as follows:
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
67PY1T direction forward
67GY1T direction forward
51PYT direction reverse
51GYT nondirectional
DIR1Y := N (“turned off”; see Figure 4.83, Figure 4.89, and Figure 4.90)
50PY1TC := DIRPFY (direction forward)
50GY1TC := DIRGFY (direction forward)
51PYTC := DIRPRY (direction reverse)
51GYTC := 1 (nondirectional)