Insulation resistance test technology Basic knowledge of insulation resistance testing.
Insulation resistance test is divided into two types of cable: common type wire and cable and commonly used outdoor type "W" wire and cable 1, ordinary wire and cable insulation high resistance meter DC voltage is adjusted to 100-500V, length is 50FT-5000FT wire in the sink After soaking for 2 hours, one electrode of the high impedance meter was connected to the copper plate electrode of the sink and the other electrode was connected to the wire conductor to be tested. The measurement time is 60 seconds, and the insulation resistance of a 1000-foot wire is greater than 2.5M at an acceptance standard of 15.6°C.
The measured water temperature of 10°C-29.4°C is converted to a value of 15.6°C and a length of 1000 feet:
R*L*M*TCF
1,000
R: High resistance meter reading L: Measured wire length M: High resistance meter magnification TCF: Temperature correction factor 2. Common outdoor type “w†wire and cable, such as SPT-2W, SJTW, CXTW, etc.
The short-term insulation resistance test method is the same as that of the ordinary type wire and cable, but the qualification criterion is completely different. The resistance of the “W†type wire is much higher. Such as CXTW22AWG, the qualified standard is 15.6 °C 225M/1000 feet. There are two ways to determine.
(1) Determination Standards SPT-2W, SPT-1W, XTW, and CXW, SJTW, etc.
Insulation resistance test is divided into two types of cable: common type wire and cable and commonly used outdoor type "W" wire and cable 1, ordinary wire and cable insulation high resistance meter DC voltage is adjusted to 100-500V, length is 50FT-5000FT wire in the sink After soaking for 2 hours, one electrode of the high impedance meter was connected to the copper plate electrode of the sink and the other electrode was connected to the wire conductor to be tested. The measurement time is 60 seconds, and the insulation resistance of a 1000-foot wire is greater than 2.5M at an acceptance standard of 15.6°C.
The measured water temperature of 10°C-29.4°C is converted to a value of 15.6°C and a length of 1000 feet:
R*L*M*TCF
1,000
R: High resistance meter reading L: Measured wire length M: High resistance meter magnification TCF: Temperature correction factor 2. Common outdoor type “w†wire and cable, such as SPT-2W, SJTW, CXTW, etc.
The short-term insulation resistance test method is the same as that of the ordinary type wire and cable, but the qualification criterion is completely different. The resistance of the “W†type wire is much higher. Such as CXTW22AWG, the qualified standard is 15.6 °C 225M/1000 feet. There are two ways to determine.
(1) Determination Standards SPT-2W, SPT-1W, XTW, and CXW, SJTW, etc.
The insulation resistance listed in the table is a short-term water immersion resistance at 15.6°C. In addition, a 50°C ramp-up is required to test the insulation resistance for a long time.
(2) TCF determination First, we must determine the impedance factor C, and then find out the corresponding M factor from UL62 Table 33.1. Apply the previous formula to obtain the impedance.
Note: For sheathed cables, such as SVT, SJTW, the insulation resistance listed in the table is the insulation resistance between the wires in the sheath. Therefore, during the measurement, the outside of the sheath should be cut off and then submerged.
Determination of impedance factor C: See UL 62, section 34.
Principle: In the process of heating and cooling the two samples, measure the resistance of 5 fixed temperature points, plot on semi-logarithmic coordinates, calculate the resistance at 15.6°C, and read out the resistance of 16.1°C. Divide the two to find the value of C
(2) TCF determination First, we must determine the impedance factor C, and then find out the corresponding M factor from UL62 Table 33.1. Apply the previous formula to obtain the impedance.
Note: For sheathed cables, such as SVT, SJTW, the insulation resistance listed in the table is the insulation resistance between the wires in the sheath. Therefore, during the measurement, the outside of the sheath should be cut off and then submerged.
Determination of impedance factor C: See UL 62, section 34.
Principle: In the process of heating and cooling the two samples, measure the resistance of 5 fixed temperature points, plot on semi-logarithmic coordinates, calculate the resistance at 15.6°C, and read out the resistance of 16.1°C. Divide the two to find the value of C
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