You can’t claim your travel expenses if you are undertaking private travel and add on a work-related component – eg while on holiday in Cairns, you notice a work-related seminar and decide to attend. In this scenario, you may claim the seminar fees, but not your travel expenses such as flights or accommodation.
Receiving a travel allowance from your employer does not automatically entitle you to a deduction. You still need to show that you were away overnight, you spent the money yourself, and the travel was directly related to earning your income.