# A Comprehensive Survey for Deep-Learning-Based
## 3 Abnormal Detection with Images over Short Distances
### Infrared Image  
#### 3.2.1 Infrared-Image-Based Anomaly Detection for Low-Voltage Pulse Technology in Smart Grids  
During the operation of power grid equipment, whether the condition of transformer winding in a strong electronic circuit is stable and whether the insulated current transformer works normally are very important for the monitoring of the local/general power systems [80]. Therefore, based on such a starting point, [PERSON], [PERSON], [PERSON], et al. [23] proposed using acoustic sensors and infrared sensors to measure the acoustic activity data of local discharge in the transformer, the air pressure data in the shell, and the internal circuit data of electronics and electricity. The data obtained by analyzing these collected data are used to detect the contact of a disconnector, and whether there are abnormalities in power transformer bushing and circuit breaker equipment [24; 25]. Because it involves various electronic circuit components (such as a limiter, coupling transformer, measuring current transformer, and measuring voltage transformer), the circuit designed for low-voltage pulse is sensitive to the data changes of these electronic components. Therefore, we use the low-voltage pulse test method combined with short-circuit-induced reactance to detect abnormalities in the windings of radial and axial transformers and the currents of insulated current transformers.  
As shown in Figure 1, by using infrared sensors, one can control and effectively detect the fault abnormalities of electrical equipment (e.g., overheating of disconnector contact, bushing condition of power transformer, circuit breaker condition, coupling transformer, measuring current transformer, measuring voltage transformer). The low-voltage impulse test is a very sensitive and reliable method to detect the deformation of transformer winding. The oscillogram obtained by low-voltage pulse detection is a description of the working state of the transformer winding. The main resonance frequency reflects whether the transformer winding is normal or not. The frequency spectrum of 250 MVA 220 kV winding transformer includes 110 kHz, 320 kHz, and 550 kHz, which change approximately twice after mechanical radial winding deformation. The frequency spectrum changes after a short circuit of an 80 MVA 110 kV transformer. The original 300 kHz, 500 kHz, and 700 kHz resonant frequencies disappear, and the new 400 kHz and 800 kHz resonant frequencies disappear. Comprehensive inspection results show that the basic causes of instrument transformer failure are low quality of sulfur hexafluoride, design defects of the transformer, lack of absorber for absorbing moisture, decomposition products of sulfur hexafluoride, use of non-corrosion-resistant materials in transformer manufacturing, and low-service-quality maintenance. The quality of sulfur hexafluoride must comply with the standards specified in IEC 60480-2004. If there are defects in the hardware equipment, there will be an abnormal temperature in a part of the power transformer and insulated current and voltage transformer. This phenomenon is detected by the infrared sensor. The detected abnormal equipment will then be repaired. A summary of the above analysis is given in Table 2, with which one can find _con_ and _pro_ of investigated technologies.