How to set default value for taxonomy autocomplete field?
Load taxonomy term using term id then, generate data in your required format.

 // Term id.
 $tid = 8193;   
 // Obtain the term. 
 $term = taxonomy_term_load($tid);
 // Format data.
 $data = $term-&gt;name . '[tid:' . $tid .']';

$form['field_school_locality_city_level'][LANGUAGE_NONE]['names']['#default_value'] = $data;