9328900990 Rev L BE1-951 Application 8-3
Operation - Protection
The phase, neutral and negative-sequence elements are activated to provide timed (51) and
instantaneous (50) overcurrent protection in this scheme. A function block is disabled by setting the
pickup set point at zero in each of the four setting groups. Virtual Output VO11 is assigned for all
protective trips. When VO11 becomes TRUE, OUT1 will operate and trip the breaker. Contact outputs
OUT2, OUT3, OUT4, and OUT5 are designated to specific function blocks. OUT2 operates for
instantaneous phase overcurrent conditions, OUT3 trips for timed phase overcurrent situations, OUT4
operates for instantaneous neutral, and negative-sequence overcurrent conditions and OUT5 operates for
timed neutral and negative-sequence overcurrent conditions.
All contact sensing inputs are unassigned, but IN1 is typically assigned to monitor breaker status (52b).
Inputs IN2, IN3, and IN4 are available for user specified functions.
Voltage protection, frequency protection, automatic reclosing, breaker failure, breaker control, and virtual
switches are not included in this logic scheme.
Operation - Setting Group Selection
A setting group can be selected automatically or by using the communication ports or the front panel HMI.
Automatic setting group changes are based on current level and duration. Automatic setting group
changes for cold load pickup and/or dynamic setting adjustments are enabled by the SP-GROUP#
command. Setting group changes initiated by contact sensing inputs are not accommodated in this
scheme, but IN2, IN3, or IN4 can be programmed to provide this function.
Operation - Alarms
If the continuous self-test diagnostics of the relay detect an error, failsafe output contact OUTA will close
and the Relay Trouble LED of the HMI will light. OUTA will also close if relay operating power is lost. More
information about alarms is provided in Section 6, Reporting and Alarm Functions.
Table 8-1. BASIC-OC Contact Sensing Input Logic
State Labels
Input Purpose Name Label
Energized De-Energized
IN1
Optional input used for breaker status
indication in Sequence of Events Reporting.
TRUE when breaker is open. Typically, IN1
is connected to the 52b contact of the
breaker.
BREAKER OPEN CLOSED
IN2 N/A INPUT_2 TRUE FALSE
IN3 N/A INPUT_3 TRUE FALSE
IN4 N/A INPUT_4 TRUE FALSE
Table 8-2. BASIC-OC Function Block Logic
Function Purpose
BESTlogic
Expression
Mode
Setting
50TP Used for instantaneous phase overcurrent protection. 0 1 (enabled)
50TN Used for instantaneous neutral overcurrent protection. 0
1 (3 Phase
Residual)
50TQ
Used for instantaneous negative-sequence overcurrent
protection.
0 1 (enabled)
150TP N/A 0 0 (disabled)
150TN N/A 0 0 (disabled)
150TQ N/A 0 0 (disabled)
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