Sel SEL-487B, Manual

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Schweitzer Engineering Laboratories, Inc. SEL-487B Data Sheet
7
Figure 11 Open-Phase Detection Reduces Breaker
Failure Coordination Time
High-speed, open-pole detection logic detects open-pole
conditions in less than 0.75 cycle, reducing breaker
failure coordination times as in Figure 11.
Overcurrent Elements
Choose from 10 time-overcurrent curves (Table 3) for
each of the 21 current inputs. Each torque-controlled
time-overcurrent element has two reset characteristics.
One choice resets the elements if current drops below
pickup for one cycle, while the other choice emulates the
reset characteristic of an electromechanical induction
disk relay.
Each terminal also includes instantaneous and definite-
time overcurrent elements. These overcurrent elements
are summarized in Table 4.
Disconnect Status Monitor
Figure 12 shows the disconnect open and close contact
relationship. During the open-to-close operation, the 89b
contact must open (disconnect is CLOSED) during the
transition zone before the main contact arcing starts. The
89a contact must close in this transition zone.
During the close-to-open operation, the 89b contact must
close during the transition zone after the main contact
arcing is extinguished (disconnect is OPEN), as shown in
Figure 12. The 89a contact must open in this transition
zone.
Table 5 shows the four possible disconnect auxiliary
contact combinations and how the relay interprets each
combination.
Figure 12 Disconnect Switch Auxiliary Contact Requirements for the Zone Selection Logic; No CT Switching Required
Table 3 Time-Overcurrent Curves
US IEC
Moderately Inverse Standard Inverse
Inverse Very Inverse
Very Inverse Extremely Inverse
Extremely Inverse Long-Time Inverse
Short-Time Inverse Short-Time Inverse
Subsidence
Open-Phase
Detection
Table 4 Overcurrent Elements per Terminal
Element Quantity Levels
Instantaneous Overcurrent Phase One level
Definite-Time Overcurrent Phase One level
Table 5 Disconnect Status as a Function of the
Auxiliary Contacts
89a 89b
Relay 89 Status
Interpretation
0 0 closed
0 1 open
1 0 closed
1 1 closed
Closed
89a Status
Open Open
Closed Closed
89b Status
Open
Disconnect Switch Starts to Close
Disconnect Switch Starts to Open
Open
Intermediate
Position
Intermediate
Position
Arcing Closed Arcing Open
Closing
q w
q
w
Opening
Main Contact Status
Intermediate
Position
Intermediate
Position