Basler BE1-CDS220, Instruction Manual

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BE1-CDS220 Protection and Control 4-21
OVERCURRENT PROTECTION
50T - Instantaneous Overcurrent Protection with Settable Time Delay
There are three independent function blocks for phase (50TP, 150TP, 250TP), three for neutral (50TN,
150TN, 250TN), and three for negative-sequence (50TQ, 150TQ, 250TQ) instantaneous overcurrent
protection. Each function block can be attached to either of the two hardware CT input circuits by the
BESTlogic mode setting.
The instantaneous overcurrent protective functions in the BE1-CDS220 relay are labeled 50T because
each has a settable time delay. If the time delay is set to zero, they operate as instantaneous overcurrent
relays.
Figure 4-18 shows the 50TP phase instantaneous over-current as a typical 50T function. Each of the nine
independent functions has two logic outputs: #50TnPU (picked up) and #50TnT (trip) where n indicates
whether it is a P (phase), N (neutral), or Q (negative-sequence) and the #50 differentiates between the
protective functions (50, 150, or 250).
D2843-02
07-24-00
BLK
50TPT
Mode =
0-disable
1-ct ckt 1
2-ct ckt 2
SL-50TP
LOGIC
50TPPU
Figure 4-18. Instantaneous Overcurrent Logic Block
A Block logic input is provided to each function and can be used to disable the function. When this
expression is TRUE, the function is disabled by forcing the outputs to logic zero and resetting the timers
to zero. For example, this could be used similar to a torque control contact on an electromechanical relay.
Each instantaneous overcurrent function has a pickup and a time delay setting. When the measured
current is above the pickup threshold, the pickup logic output, 50TPPU (for example) = TRUE and the
timer is started. If the current stays above pickup for the time delay, the trip logic output, 50TPT (for
example) = TRUE. If the current falls below the dropout ratio, which is 95%, the timer is reset to zero.
The phase overcurrent protective functions include three independent comparators and timers, one for
each phase. If the current is above the pickup setting for any one phase, the pickup logic output is
asserted and if the trip condition is TRUE for any one phase, the trip logic output is asserted.
If the target is enabled for the function, the target reporting function will record a target for the appropriate
phase when the protective function trip output is TRUE and the fault recording function trip logic
expression is TRUE. See Section 6, Reporting and Alarm Functions, Fault Reporting Functions, for more
details on the target reporting function.
BESTlogic Settings for Instantaneous Overcurrent
BESTlogic settings are made from the BESTlogic Function Element screen in BESTCOMS. Figure 4-19
illustrates the BESTCOMS screen used to select BESTlogic settings for the 50T elements. To open the
BESTlogic Function Element screen, select Overcurrent from the Screens pull-down menu. Then select
the 50T, 150T or 250T tab. Open the BESTlogic Function Element screen for the desired element by
selecting the BESTlogic button corresponding with the desired element. Alternately, these settings can be
made using the SL-x50T ASCII commands (where x = blank, 1, or 2).