Yea, it's normal to see these entries in the alert log. However, you shouldn't get these during normal operation.

Here's a sample of one of mine:

grep SUCCESS alert_+ASM1.log |head -6

SUCCESS: diskgroup DISKGROUP1 was mounted
SUCCESS: completed COD recovery for group 1/0x46bdb403 (DISKGROUP1)
SUCCESS: refreshed PST for 1/0x46bdb403 (DISKGROUP1)
SUCCESS: rebalance completed for group 1/0x46bdb403 (DISKGROUP1)
SUCCESS: rebalance completed for group 1/0x46bdb403 (DISKGROUP1)
SUCCESS: refreshed PST for 1/0x46bdb403 (DISKGROUP1)