The AR700 measures acoustic signals with multiple relocatable acoustic sensors mounted on the transformer. The software determines the defect location using the time difference of all incoming signals. Finally, these coordinates are shown in a 3D model of the transformer. AR700 device is used for measuring of acoustic signals on the external surfaces of gas-insulated switchgears, power transformers and other grounded tank high-voltage equipment. The acoustic signals are caused by partial discharges in the insulation, which is the site of the defects. The advantage of AR700 device is the quick installation of the relocatable acoustic PD sensors on the grounded external surface of high-voltage equipment. The sensors have magnetic holders thus making it unnessary to de-energize the equipment for the sensors installation. AR700 device has 4 synchronic channels for acoustic signal measurement. This gives the possibility not only to detect defects in the insulation, but also to locate them. The 3D location function of the AR700 device is unique for acoustic devices.