What is ΔT in thermography?

ΔT (delta T) is the temperature difference between the measured component and a reference point (typically a similar component under the same load, or ambient temperature). It is the primary severity indicator in thermographic inspections.

What severity levels are used?

Common severity classification uses four levels: Minor (monitor), Intermediate (plan repair), Serious (repair soon), and Critical (immediate action). The ΔT thresholds vary by component type and industry standards.

What ΔT thresholds apply to electrical panels?

For electrical connections (ΔT over ambient): 1-10°C = Minor, 11-20°C = Intermediate, 21-40°C = Serious, >40°C = Critical. These thresholds are based on NETA MTS standards and are widely used in electrical thermography.

How does load affect thermography readings?

Temperature rise is approximately proportional to the square of the current (I²R heating). When equipment is not at full load, findings may be worse at full load. Always record the load percentage during inspection and extrapolate to full load conditions.

What are the main standards for thermography?

Key standards include ISO 18434 (condition monitoring by thermography), NETA MTS (electrical maintenance testing), ASTM E1934 (IR building surveys), and IEC 62446 (PV systems). ISO 18434 provides the overall framework for machine condition monitoring using IR.

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紅外線熱像儀溫度限制

依據 ISO 18434 分類紅外線檢測結果。輸入元件類型與高於參考溫度的測量 ΔT，即可獲得嚴重度分類與建議處置措施。

ISO 18434NETA MTS紅外線檢測

分類

嚴重度

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測量 ΔT

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優先級

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建議措施

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此元件的溫度閾值

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溫度計

Electrical Components (NETA MTS, ΔT over ambient)

ΔT (°C)	嚴重度	優先級	措施
1–10	輕微	4	監控，方便時修復
11–20	中等	3	計畫於下次預定停機時修復
21–40	嚴重	2	盡快修復
>40	嚴重	1	立即採取行動 — 有故障/火災風險

機械元件

元件	輕微	中等	嚴重	嚴重
馬達機殼	<10°C	10–25°C	25–40°C	>40°C
軸承座	<10°C	10–20°C	20–35°C	>35°C
聯軸器	<5°C	5–15°C	15–25°C	>25°C
疏水閥	<20°C	20–40°C	40–60°C	>60°C
保溫層	<5°C	5–15°C	15–30°C	>30°C

依據 ISO 18434 的紅外線熱成像溫度限制 | Vibromera

分類

Electrical Components (NETA MTS, ΔT over ambient)

機械元件

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