Field Companion
Four quick checks for the readings you take on site. Free, on any phone, no sign-up.
Thermal hot spot
Example valuesLoad at the time of the scan
Severity bands follow NETA MTS Table 100.18. The full-load estimate scales the rise with the square of current, a common rule of thumb.
Insulation resistance
Example valuesRatio tests (optional)
Minimum values and PI limits from IEEE 43 (2000 edition). Temperature correction uses the older rule that resistance halves for every 10 °C rise; the 2013 edition corrects by insulation type, so treat the corrected figure as a guide.
Voltage unbalance
Example valuesA small voltage unbalance causes a much larger current unbalance, so motor windings run hotter than the voltage figure suggests.
Unbalance = largest deviation from the average ÷ the average (NEMA MG 1). NEMA calls for motor derating above 1% and advises against running above 5%.
Cable fault distance
Example valuesPulse-echo gives the distance along the cable, not over the ground. Joints, slack loops and route bends shift the spot, so pinpoint acoustically or with a surge locator before you dig.
Distance = V/2 × time to reflection. V/2 = known length ÷ time to the far-end reflection.
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Guidance for trained people only. Always follow your site's safety rules, the equipment manufacturer's instructions and the full standard before making a decision.
Guidance for trained people.
Always follow your site's safety rules, the equipment manufacturer's instructions and the full standard.
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Built on known methods
NETA MTS Table 100.18, IEEE 43 and NEMA MG 1, with the method named under each result.