New OneLiner's Relay Operation Check Algorithm for Lines with Dual Pilot

In response to the user requests, we had made some changes in the OneLiner command "Check | Relay operation using stepped-event" algorithm for lines with dual pilot. These lines are identified in the OLR network by users using a special tag on one of the relay groups.

Prior to this change, OneLiner checked lines with dual pilot in the same way as all other lines, except that no branch outages of any kind are considered in the check.

With the new checking algorithm, the program will initiate a stepped-event analysis with only a single step in which the dual-pilot line is artificially tripped at all the line terminals at t=0s. The relay coordination logic will compute the coordinating time interval (CTI) for all the protective elements in the vicinity of the dual-pilot line. If a CTI is less than the parameter “Minimum coordinating interval in cycles for relays in the vicinity of dual-pilot lines” you specified in the Check | Relay Checking Parameters command (the default is 5 cycles), the report will give an error of “CTI too low” or "CTI is zero" to warn you of fast, overreaching relays in the vicinity that may race against the dual-pilot scheme. OneLiner still will not allow you to specify branch outages of any kind.

Additional explanation of the checking method for dual-pilot lines is available in the updated on-line help. You can find it by searching for the words "ALGORITHM FOR LINES WITH DUAL PILOT".

Warning: The checking algorithm does not take into account any backup relays that may be on the terminals of the dual-pilot line. To check the backup relays, you must first remove the dual-pilot tag(s).

The new checking algorithm is available in OneLiner V14.8 Build 65877 or later (Build number is displayed in the Help | About dialog box). Users should contact ASPEN Support to request this program update.