Basler Electric BE1-700 - Manual (Page 61)

The user should also be aware that the 79 function "Sequence Control Block" (79SCB) provides an
alternate method to control relay operation based on the reclose status. See the 79 function description
later in this section for additional details.
Automatic Control by Monitoring Line Current
The Setting Group 0 and 1 switch to and return settings determine how the function selects the active
setting group when automatic selection is enabled.
Automatic control of the active setting group allows the relay to automatically change configuration for
optimum protection based on the current system conditions. For example, in locations where seasonal
variations can cause large variations in loading, the overcurrent protection can be set with sensitive
settings during the majority of the time and switch to a setting group with lower sensitivity (higher pickups)
during the few days of the year when the loading is at peak.
The relay will switch to a setting group when current rises above the "switch-to threshold" for the "switch-
to time" and will return from the setting group when current falls below the "return threshold" for the
"return time." However, if the "switch-to" threshold is 0 and a non-zero switch-to time is entered, then the
relay changes to the indicated setting group and falls below 10% of nominal (0.5 A / 0.1 A for 5 A / 1 A
nominal relays) after the switch-to time. This is used in the example application for cold load pickup,
below.
If the monitored element is 60FL, 791, 792, 793, or 794, the switch-to time, switch-to threshold, return
time, and return threshold are ignored and the setting group is based upon the status for the reclose step.
This method of controlling setting groups will be covered further in the following paragraphs:
If a group's switch-to threshold is zero and the groups switch-to time delay is 0 and the monitored element
is any overcurrent element (i.e., not 60FL, 791, 792, 793, or 794), then the relay will never automatically
switch to that setting group.
There are five settings for each group that are used for automatic control. Each group has a switch
threshold and time delay, a return threshold and time delay, and a monitored element. The switch and
return thresholds are a percentage of the SG0 pickup setting for the monitored element. The monitored
element can be any of the 51 protective functions. Thus, if you wish to switch settings based upon
loading, you could set it to monitor 51P. If you wish to switch settings based upon unbalance, you could
set it to monitor 51N, 151N, or 51Q. When the monitored element is 51P, any one phase must be above
the switch threshold for the switch to time delay for the criteria to be met. All phases must be below the
return threshold for the return time delay for the return criteria to be met.
On the BE1-700C, this function can also be used to automatically change the active setting group for cold
load pickup conditions. If the switch threshold for a group is set to 0%, the function will switch to that
group when there is no current flow for the time delay period, indicating that the breaker is open or the
circuit source is out of service. The threshold for this is 10% nominal rating of the relay current input.
Note the difference in operation when a switch-to threshold of 0% is used. For this setting the group is
switched to when current falls below 0.5 A / 0.1 A (5 A / 1 A nominal). But when any other switch level is
used, the switch occurs when current rises above the switch level.
When the switch criteria are met for more than one setting group at a time, the function will use the
numerically higher of the enabled settings groups. If the switch to time delay setting is set to 0 for a
setting group, automatic control for that group is disabled. If the return time delay setting is set to 0 for a
setting group, automatic return for that group is disabled and the relay will remain in that settings group
until returned manually by logic override control.
Group Control by Monitoring Reclose Status
The active setting group may also be controlled by the status of the reclose (79) (optional) function. Upon
entering a reclose operation, as the relay steps through an automatic reclose operation, the relay may be
instructed to change to an appropriate setting group using the command SP-GROUP[n] = ,,,,<791, 792,
793, or 794>. If the monitored element in the SP-GROUP command is 791, 792, 793, or 794, the switch-
to time, switch-to threshold, return time, and return threshold are ignored.
When settings group changes are made via SP-GROUP[n] = ,,,,<791, 792, 793 or 794> the relay will stay
in the last group changed to until the relay returns to reset condition. Upon return to reset condition, the
relay restores Setting Group 0.
The points in the reclose process that the 791, 792, 793, and 794 setting causes a change to the desired
setting group is when a) the referenced reclose occurs and b) after the breaker closes. For instance, SP-
9376700990 Rev M BE1-700 Protection and Control 4-5