4-12
Protection and Control
BE1-951
Figure 4-8. Instantaneous Overcurrent Elements
2.
Override logic control and change the active setting group to SG1.
>CS-GROUP=1
GROUP=1 SELECTED
>CO-GROUP=1
GROUP=1 EXECUTED
3.
Return control of the active setting group to the automatic setting group logic.
>CS-GROUP=L
GROUP=L SELECTED
>CO-GROUP=L
GROUP=L EXECUTED
Retrieving Setting Group Status Information
The active setting group can be determined from HMI screen 1.4.5 or by using the RG-STAT command.
Section 6,
Reporting and Alarm Functions, General Status Reporting provides more information about
determining the active setting group.
Logic override status can be determined from HMI screen 2.3.1 or through the RG-STAT command. Section
6,
Reporting and Alarm Functions, General Status Reporting provides more information about determining
logic override status.
OVERCURRENT PROTECTION
The BE1-951 includes instantaneous elements for Phase, Neutral, and Negative Sequence, as well as time-
overcurrent elements for Phase, Neutral or Ground, and Negative Sequence.
50T Instantaneous Overcurrent Protection with Settable Time Delay
There are two BESTlogic elements for phase (50TP and 150TP), two elements for ground (50TN and
150TN), and two elements for negative sequence (50TQ and 150TQ) instantaneous overcurrent protection.
The alphanumeric designation for each element contains the letter T to indicate that the element has an
adjustable time delay. If an element has a time delay setting of zero, then that element will operate as an
instantaneous overcurrent relay. Each element can also be set as either directional or nondirectional. Refer
to the paragraph,
67 Directional Overcurrent Element, for more information.
The 50TP, 50TN, and 50TQ instantaneous overcurrent elements are shown in Figure 4-8. The 150TP,
150TN, and 150TQ elements are identical to their counterparts. Each element has two logic outputs: Pickup
(PU) and Trip (T).
Each element has a Block (BLK) input that can be used to disable the function. A BESTlogic expression is
used to define the BLK input. When this expression is TRUE, the element is disabled by forcing the outputs
to logic zero and resetting the timers to zero. This feature functions in a similar way to a torque control
contact of an electro mechanical relay.
A Logic Mode input allows each instantaneous overcurrent element to be enabled or disabled. The ground
elements, 50TN and 150TN, have additional mode selections. Element operation can be based on
calculated three-phase 3Io current values (Mode 1) or on measured ground current through the optional
independent ground CT input (Mode G). More information about logic mode selections is provided in the
following
BESTlogic Settings for Instantaneous Overcurrent Elements subsection.
