Accelerated depreciation is the right to write down the capital goofs for tax purpose. It is faster than the rate at which they normal depreciated.
The purpose of accelerated depreciation is to promote investment which enable the company to defer the its taxes when it starts to invest.
Based on the concept of accelerated depreciation, the profit of the firm excluded of depreciation and therefore it tax liabilities are lower than under normal depreciation.
When the capital goods are written off, profit net depreciation become higher than they would have been under normal depreciation.