Test results are dependent on the temperature of the insulating material and the humidity of the surrounding environment at the time of the test.
Contents
Electrical Apparatus and systems other than Transformer and Motor Windings (20°C)
| Nominal Equipment Rating (Volts) | Minimum DC Test Voltage | Recommended Minimum Insulation Resistance (Megohms) |
|---|---|---|
| 250 | 500 | 25 |
| 600 | 1,000 | 100 |
| 1,000 | 1,000 | 100 |
| 2,500 | 1,000 | 500 |
| 5,000 | 2,500 | 1,500 |
| 8,000 | 2,500 | 2,500 |
| 15,000 | 2,500 | 5,000 |
| 25,000 | 5,000 | 10,000 |
| 34,500 | 5,000 | 100,000 |
| 46,000 and up | 5,000 | 100,000 |
Reference: ANSI/NETA-ATS 2017 & ANSI/NETA-MTS 2015 Table 100.1 - Insulation Resistance Test Values Electrical Apparatus and Systems Other Than Rotating Machinery
Transformer Insulation Resistance Test Values
| Transformer Coil Voltage Rating | Recomended Test Voltage (DC) | Recommended Minimum Insulation Resistance in Megohms | |
|---|---|---|---|
| Liquid Filled | Dry Type | ||
| 0 - 600 | 1000 | 100 | 500 |
| 601 - 5000 | 2500 | 1000 | 5000 |
| > 5000 | 5000 | 5000 | 25000 |
Reference: ANSI/NETA-ATS 2017 & ANSI/NETA-MTS 2015 Table 100.5 - Transformer Insulation Resistance Testing
Insulation Resistance Acceptance Test Values for Motor Windings (1 Minute @ 40°C)
| Winding Rated Voltagea | Recomended DC Test Voltage | Recomended Minimum Insulation Resistance in Megohms: Windings Before 1970, Field Windings, Others Listed in NETA ATS Table 100.11b | Recomended Minimum Insulation Resistance in Megohms: DC Armature, AC Windings, (form-wound coils) | Recomended Minimum Insulation Resistance in Megohms: Random-Wound Stator Coils, Form-Wound Coils below 1kV |
|---|---|---|---|---|
| < 1,000 | 500 | kV + 1 | 100 | 5 |
| 1,000 - 2,500 | 500 - 1,000 | kV + 1 | 100 | - |
| 2,501 - 5,000 | 1,000 - 2,500 | kV + 1 | 100 | - |
| 5,001 - 12,000 | 2,500 - 5,000 | kV + 1 | 100 | - |
| > 12,000 | 5,000 - 10,000 | kV + 1 | 100 | - |
aRated line-to-line voltage for three-phase ac machines, line-to-ground voltage for single-phase machines, and rated direct voltage for dc machines or field windings.
bkV is the rated machine terminal to terminal voltage.
Reference: ANSI/NETA ATS-2017 Table 100.11 - Insulation Resistance Test Values Rotating Machinery for One Minute at 40° C
Insulation Resistance Maintenance Test Values for Motor Windings (1 Minute @ 40°C)
| Winding Voltagea | Recomended Minimum DC Test Voltage | Recomended Minimum Insulation Resistance in Megohms: Windings Before 1970, Field Windings, Others Listed in NETA MTS Table 100.11b | Recomended Minimum Insulation Resistance in Megohms: DC Armature, AC Windings, (form-wound coils) | Recomended Minimum Insulation Resistance in Megohms: Random-Wound Stator Coils, Form-Wound Coils below 1kV |
|---|---|---|---|---|
| < 1,000 | 500 | kV + 1 | 100 | 5 |
| 1,000 - 2,500 | 500 - 1,000 | kV + 1 | 100 | -- |
| 2,501 - 5,000 | 1,000 - 2,500 | kV + 1 | 100 | -- |
| 5,001 - 12,000 | 2,500 - 5,000 | kV + 1 | 100 | -- |
| > 12,000 | 5,000 - 10,000 | kV + 1 | 100 | -- |
aRated line-to-line voltage for three-phase ac machines, line-to-ground voltage for single-phase machines, and rated direct voltage for dc machines or field windings.
bkV is the rated machine terminal to terminal voltage.
Reference: ANSI/NETA MTS-2015 Table 100.11 - Insulation Resistance Test Values Rotating Machinery for One Minute at 40° C. Values based on IEEE Std 43-2013.
