The most powerful predictive maintenance tool of all: a camera that sees what the eye cannot — the temperature of every connection, contact, and insulator, while the substation operates at full load without any disconnection. A loose connection reveals itself as a glowing hotspot months before it becomes a fault.
Why Thermal Imaging Specifically?
- No de-energizing required: inspection is carried out while the equipment is energized and under normal load — in fact, this is a condition of its effectiveness, since a thermal problem only appears when current is flowing.
- Early detection: increased resistance at a connection generates localized I²R heating that builds up slowly — the camera catches it long before melting and arcing occur.
- Fast comprehensive scanning: an entire substation in a single round.
What Do You Inspect in the Substation?
- Connections of the busbars and joints — the highest-current and most fault-prone locations.
- Disconnector and switch contacts — wear raises their temperature under load.
- Cable terminations and ends, and insulating bushings.
- Fuses and their bases, transformer tanks and radiators (uneven differentials), and capacitor banks (one unit hotter than its neighbors).
How Do You Read the Results?
| Indicator | Significance |
|---|---|
| A hotspot at one connection compared to similar connections | A loose or corroded connection — comparison between the three phases is the most reliable criterion |
| One phase consistently hotter than the other two along the entire path | Load imbalance — a distribution issue, not a connection issue |
| Gradual heat distribution across an equipment body | May be normal — compare against its usual pattern and the load at the time of inspection |
- Record the load at the time of inspection: a temperature differential at 30% load will roughly double at full load (heat follows the square of the current).
- Classify findings by severity (temperature differential from reference) and set a remediation deadline for each severity level.
- Document images in the equipment record for comparison between rounds — the trend matters more than a single snapshot.
Sample answer: A 25-degree differential between identical connections carrying the same current is a serious indication of a poor connection (loosening or corrosion) raising the local resistance. I first check whether the phase loads are balanced to rule out imbalance, and record the load at the time of inspection — since the differential will worsen with the square of the current at higher load. I then classify it according to the established severity criteria and schedule urgent remediation: isolate, disassemble, clean, and re-torque to the correct value, followed by re-inspection afterward to confirm.
Reading absolute temperature values while ignoring relative comparison and load. 60 degrees may be entirely normal for a fully loaded busbar, while 45 degrees may be a serious alarm if its counterparts are at 30 — comparison between identical phases under the same load conditions is the standard.
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