Inspection of transformers can be performed without any detection tools.

Transformers are electrical devices that change voltage and current based on the principle of electromagnetic induction. In power transmission and distribution systems, transformers are essential for stepping up or stepping down voltages to reduce energy losses during transmission. For example, industrial facilities typically receive power at 10 kV, which is then stepped down to low voltage via transformers for on-site use. Today, let’s learn about several common transformer inspection methods.

1. Visual Inspection Method

The visual method involves operators using their eyes to observe visible parts of operating equipment to detect abnormalities. Changes such as discoloration, deformation, displacement, cracking, loosening, sparking, smoking, oil leakage, broken strands or broken conductors, flashover marks, foreign object accumulation, corrosion, or contamination can all be identified through visual inspection. Therefore, the visual method is one of the most commonly used techniques in equipment routine inspection.

2. Olfactory Inspection Method (Smell Test)

When the insulation materials in electrical equipment overheat, they emit a distinct odor into the surrounding air. Experienced personnel can detect this unusual smell during routine patrols. Upon noticing such an odor, the inspector should carefully examine the equipment to locate the overheated component or area and continue investigating until the root cause is identified.

3. Tactile Inspection Method (Touch Test)

For live high-voltage equipment—such as operating transformers or the neutral grounding system of an arc suppression coil—the touch method is strictly prohibited due to safety risks. However, for de-energized equipment with a reliably grounded enclosure, touch inspection can be used to check temperature or heat rise. Additionally, secondary equipment can be checked for heating or vibration using the hand-touch method.

4. Auditory Inspection Method (Hearing Test)

Primary and secondary electromagnetic devices in substations—such as transformers, instrument transformers, relays, and contactors—normally produce a steady, rhythmic, and consistent "hum" when energized and operating properly. This sound comes from the core and windings under AC excitation. Operation personnel should become familiar with the normal sound characteristics. When a fault occurs, unusual noises may appear—such as irregular sounds or even "cracking" or "popping" discharges. By comparing changes in pitch, rhythm, and volume between normal and abnormal conditions, operators can identify the presence, nature, and location of equipment faults.