By default SQL log file size limits are setup to unrestricted.
If you wish to setup a limit, you can do so by following the below. Please be careful when making such changes. Make sure you have a backup of your databases before attempting any changes.
1) Open SQL Enterprise or SQL Server Management Studio
2) Expand databases
3) Right click on the database you wish to set the log size limit on and click properties
4) Click Files
5) Locate your log file in the list. Should be databasename_log
6) Scroll across to the tab named AutoGrowth and click the square button
7) Click restricted file growth and add a limit, click ok