ClicksThe poor contact of the outlet connector of the cable accessory usually has a thermal image feature, which is a thermal spectrum centered on the heating point. Common phenomena are:
1. The overall insulation of the cable head is poor:
Refers to defects such as dampness and deterioration of the overall insulation caused by poor processing or long-term operation of the cable head. The characteristic is that the temperature of the entire cable head is relatively high.
Although the surface temperature rise of the heating cable head does not exceed the regulations, the temperature difference of the same kind is relatively high (4.7K), which is a defect of poor overall insulation of the cable head.
2. Poor local insulation of cable head:
It refers to defects such as partial damage, dampness, and deterioration of the insulation caused by poor processing or long-term operation of the cable head. The characteristic is that the temperature rise of the local insulation area at the intersection of the cable head is too large.
3. Poor insulation of cable head outlet sleeve:
Refers to the defect that the outlet sleeve of the cable above 35kV is not well sealed, which causes the water inflow and damp. Its characteristic is that the overall temperature of the casing rises, and the temperature of the middle and lower parts close to the flange is relatively high. The temperature difference between phases should not exceed 0.5K when compared with similar types.
Fourth, the overall heating of the cable:
Refers to defects caused by cable insulation aging or overload operation. The maximum allowable temperature rise of the cable and cable head shall not exceed the relevant regulations.
5. Poor contact of power capacitor:
Parallel capacitors (series capacitors) are judged according to relevant regulations. When the thermal image is abnormal or the relative temperature difference of the same kind exceeds the standard, other test methods shall be used to determine the nature of the defect and treatment opinions.
6. Poor contact of insulators:
1. Porcelain insulator string:
a) The temperature distribution of a normal insulator string corresponds to the voltage distribution law, that is, an asymmetrical saddle shape, and the temperature difference between adjacent insulators is small.
b) The thermal image characteristic of low-value insulators is that the temperature rise of the steel cap is too large, and the temperature rise of the steel cap is too low for the zero-value insulators, and the dirty insulators are manifested as the temperature rise of the porcelain plate.
2. Support insulator:
Normal support insulators have slight heat near the conductor, and abnormal insulators show obvious heat generation overall or locally.
7. Other equipment:
1. Poor contact of wires, bus bars, isolation switches and other connecting parts
The thermal image feature is a thermogram centered on the hot spot.
2. Heating of wall bushing support plate:
The supporting iron plate of the high-current wall bushing is not open, causing a large eddy current loss.
3. The arrester in the wave trap is damaged:
The normal lightning arrester basically does not heat up. If there is obvious heating, the arrester has been damaged.
4. Poor contact of the secondary circuit:
The thermal image feature is a thermogram centered on the hot spot.
