An integrated current sensing transformer includes a bobbin, a magnetic core assembly, a first primary winding element, a second primary winding element, a secondary winding element. The bobbin has a receptacle therein. The magnetic core assembly is partially embedded into the receptacle for providing a closed path of magnetic flux. The first primary winding element is wound around the bobbin for inputting a first test current therein. The second primary winding element is wound around the bobbin for inputting a second test current therein. The secondary winding element is wound around the bobbin for outputting a sensing current when either the first test current or the second test current is sensed. The magnitude of the sensing current is directly proportional to the magnitude of the first test current or the second test current.