Is the SQL Server instance running on your local PC or on a another machine that is accessed via network?

If it is running on a networked server (typical) and you have SQL Server Management Studio (SSMS) connected to that instance during the affected time range, does its connection also drop unexpectedly?

I agree with others that your issue sounds like something else on your network is causing connections to the database to be dropped. Do you have an instance of SQL Server running on your PC that you can connect your app to, temporarily, to troubleshoot? If so, I would see if the app's connection to the local instance also drops during the same time interval. If not, that would indicate something else on the network is causing the issue.

Some time ago I worked for a company that experienced a nearly identical problem. The issue was caused by Network/Security teams implementing a port scanning process to detect unauthorized network access... as a result, when the various ports used by a mission-critical, unattended process were scanned (at roughly the same time every day), it caused that application's connections to the database to be dropped, causing major service outages. Of course, this port scanning was implemented without first informing any of the development teams! A stellar example of teams working together (not!)

HI Sivaprakash;

  FWIW:  As  suggestion, I would talk with your Network and DBA teams to see if there are any session / connection timeouts set in your environment that might be affecting your PB App(s).

Regards ... Chris