## 1 Introduction  
Transformers are the main equipment in transmission and distribution systems because of their ability to easily transfer voltage levels. At present, electricity is the dominant form of energy used in daily life. In addition, in industrial systems, electrical energy is required for production in different industries, such as the automotive industry, agriculture and food industry, petrochemical and chemical industry, etc. However, when using electric energy, the equipment in the transmission and distribution system is also affected, which inevitably includes transformers. Usually, require maintenance periods. However, when a transformer has a partial discharge (PD) defect that is not detected early, it will cause the insulation of the transformer to deteriorate and, which could cause a serious accident in the future [1]. These failures are a problem that will inevitably cause damage to the transformer and cause enormous economic losses. The relationship between PD and sensors has been extensively studied due to the importance of PD in power systems, as PD results in damage to electrical equipment. Several researchers have studied sound-wave propagation inside a transformer tank with the simulation method [2], as well as the properties and suitability of sensors to detect PD in electrical devices, such as switchgear, rotary electric machines, cables, and transformers [3]. Inspection of insulation and partial discharge (PD) analysis are used to reflect the state of the insulation, with accurate PD signal measurement being key to detection systems for transformer insulation [4; 5]. PD measurement is widely used in many industries, such technology as technology and manufacturing, and is one of the most common techniques that used to assess the insulation condition of transformers. For example, PD measurement is used to observe the location of insulation defects causing discharge, i.e., PD source localization [6; 7]. Localization of PD faults in transformers is required at various times when fault currents are identified in transformers. Measurement of partial discharge levels in accordance with IEC 60,270 is an important procedure, which is standardized worldwide in order to guarantee quality assurance of transformers [7; 8; 9]. In addition, PD measurement is performed as a part of routine measurements during the manufacturing process [6; 8]. Therefore, PD detection and localization procedures are normally initiated as a result of corresponding indications, which are obtained from dissolved gas-in-oil analysis (DGA) and PD monitoring. For these reasons, precise location of PD can help with effective maintenance during operation to optimize the production of power transformers [9]. However, unusual devices can create some problems, such as causing nonsqp PD pluses and phenomena, such as light, sound and electromagnetic radiation. Therefore, a new device is required to address these issues. At present, the excellent properties of cast-resin dry-type transformers are widely used in industrial systems, such as heavy industry, airports, hospitals, public transport systems, and high-rise buildings. In particular, cast-resin transformers are used buildings requiring safety from explosions or fire, as it is the safest transformer for indoor installation [10; 11]. Furthermore, it is a first-choice equipment for use in high-rise buildings and other buildings. However, the service life of cast-resin dry-type transformers depends on the insulation conditions; when in operation under heat, the electric field, mechanical force, and the environmental conditions can lead to the transfer of electric charges in the transformer. Periodic offline diagnostic tests play an important role in the transformer devices, generally occurring over a 6-12 month/period. However, if something goes wrong with the transformer between inspections, it can result in massive damage to the transformer and related power systems. It may take hours to address damages that occur as a result of PD.