(1)According to DL/T 626, after the disc insulator is put into operation, it should be inspected once within 3 years, and then the inspection period can be extended according to the measured deterioration rate and operating experience, but the longest cannot exceed 10 years. The inspection cycle requirements for porcelain insulators are shown in the table below.
Porcelain insulator detection cycle
|
Average annual cracking rate (%) |
＜0.005 |
0.005~0.01 |
>0.01 |
|
Detection cycle (year) |
5~6 |
4~5 |
3 |
Note a: When the average annual cracking rate of the measured porcelain insulator is less than 0.001% in the seventh or eighth year, the detection cycle can be extended to 10 years;
Note b: Mechanical strength test once every 5 years.
(2) The detection methods for disc insulator degradation in operation mainly include ground inspection, detection of power outage climbing tower, detection of live climbing tower or laboratory detection after replacement, etc.
(3) The detection contents of disc insulator appearance deterioration mainly include: shed shed damage and cracks; steel cap and iron foot corrosion and bending; pouring cement and shed shed and steel cap displacement; porcelain insulator surface deglazing and anti-pollution flashover Aging and peeling of the coating; discharge flashover of sheds and metal parts; shedding and deformation of locking pins of insulators, etc.
(4) The insulation resistance degradation of disc insulators can be detected and judged by spark gap detection method (distributed voltage detection method) and laboratory megohmmeter detection method.
(5) If necessary, dry power frequency withstand voltage test and electromechanical damage load test can be carried out on random insulators.
(6) Infrared (ultraviolet) thermal imaging camera can also be used for auxiliary detection of disc insulator deterioration detection. This detection method mainly judges insulation degradation by comparing the thermal imaging of insulators between different sheets of the same phase and between different phases Condition.
(7) Refer to the table below for the common degradation detection methods, requirements and judgment standards of disc insulators.
Insulator Insulation Testing Methods, Requirements and Judgment Standards
|
No. |
detection methods |
Judgment Standards |
|
1 |
Measuring voltage distribution (or spark gap) |
(1) The voltage value of the tested insulator is lower than 50% of the standard value, and it is judged as a deteriorated insulator: (2) If the voltage value of the tested insulator is higher than 50% of the standard specified value, and at the same time significantly lower than the voltage value of the qualified insulators on both adjacent sides, it is judged as a deteriorated insulator; (3) If there is no discharge under the specified spark gap distance and discharge voltage, it is judged as a deteriorated insulator. |
|
2 |
Measuring insulation resistance |
(1) Voltage level 500kv: the insulation resistance of the insulator is lower than 500MΩ, and it is judged as a deteriorated insulator; (2) The voltage level is below 500KV: the insulation resistance of the insulator is lower than 300MΩ, and it is judged as a deteriorated insulator. |
|
3 |
Dry power frequency withstand voltage test |
For porcelain insulators with a rated electromechanical damage load of 70KN-550KN, apply 60KV dry power frequency withstand voltage for 1min; for large-diameter anti-pollution insulators, apply the dry power frequency flashover voltage value corresponding to ordinary insulators. Those who are not tolerant are judged as deteriorated insulators. |
|
4 |
Visual inspection |
Porcelain parts with cracks, breakage, glaze defect or severe burns, serious peeling of cement glue, serious corrosion of iron caps and steel feet, etc. are judged as deteriorated insulators. |
|
5 |
Electromechanical failing load test |
When the electromechanical damage load is lower than 85% of the rated mechanical load, the insulator is judged as a deteriorated insulator. |
