From the previous chapter, we know that the condition maintenance of equipment is based on safety, reliability, environment, cost, etc. Through equipment status evaluation, risk assessment, and maintenance decision-making, it is a strategy to achieve safe and reliable operation of equipment and reasonable maintenance cost. The basis is to evaluate the status of the equipment, the process is to conduct risk assessment and maintenance decision-making, and finally come up with a reasonable maintenance strategy for the equipment. Especially in the maintenance of shunt capacitor devices, this strategy can effectively improve the operating stability of the equipment and reduce maintenance costs.
1 Principles of condition maintenance of filter and shunt capacitor devices
For any equipment to carry out condition maintenance, the principle of “must be repaired if necessary, and must be repaired well” should be followed. Filters and shunt capacitors are no exception. According to the results of equipment status evaluation, risk assessment is carried out considering equipment risk factors, and maintenance plans for equipment are dynamically formulated. The plan and content of condition maintenance are reasonably arranged, which is specific to the content of condition maintenance work of AC and DC filter and shunt capacitor devices, including power outage, power outage testing and experiment, and power outage and non-power outage maintenance and maintenance work.
In the process of carrying out the condition inspection and maintenance of the filter and shunt capacitor device, dynamic condition evaluation management should be implemented. A condition evaluation should be carried out after each equipment inspection or test. At the same time, regular equipment evaluation should be carried out according to local requirements to grasp the equipment status in real time. Generally, when the filter shunt capacitor device equipment is newly put into operation, a condition evaluation should be carried out on the equipment within one month. In the early stage of equipment operation, according to the provisions of DL’T 393-2010 “State Inspection and Test Procedures for Transmission and Transformation Equipment”, routine tests should be arranged for the filter and shunt capacitor equipment within one year after commissioning. At the same time, a comprehensive inspection should be carried out on the equipment and its accessories (including electrical circuits and equipment appearance parts), various state quantities should be collected, and a condition evaluation should be carried out again. After this evaluation, the various equipment state quantity information collected will be comprehensively compared with the equipment state quantity information collected during the equipment installation handover. The equipment operation and maintenance personnel should have a preliminary understanding of the quality of the equipment and the problems that may arise in the future operation.
For filter and shunt capacitor equipment that have been in operation for more than 10 years, the probability of failure or failure has increased significantly. It is advisable to adjust the maintenance plan and content according to the equipment operation and evaluation results.
2 Classification and status inspection and maintenance items of filter and parallel capacitors
2.1 Maintenance classification
According to the nature and scope of work, the maintenance of AC and DC filters and shunt capacitor devices is divided into 4 categories: A-type maintenance, B-type maintenance, C-type maintenance, and D-type maintenance. Among them, A, B, and C are power-off maintenance, and D is non-power-off maintenance.
Class A maintenance
Class A maintenance refers to the overall inspection, maintenance, replacement and testing of AC and DC filters and shunt capacitor device.
In order to better define the Class A maintenance of filter and shunt capacitor device, based on the domestic self-flow converter station’s many years of operation experience, this type of maintenance generally includes: ① The capacitor tower avalanche breakdown is replaced as a whole, or the faulty capacitors on a single tower exceed 30% of the total number of capacitors in the tower and need to be replaced; ② The resistors, reactors, current transformers, and lightning arresters in the device have serious faults and cannot be repaired on site and need to be replaced as a whole; ③ Various routine tests and diagnostic test items before and after equipment processing
Class B maintenance
Class B maintenance refers to the local maintenance of AC and DC filters and shunt capacitor devices, disassembly inspection, maintenance, replacement and testing of components.
Class B maintenance usually includes: ① Replacement of a small number of capacitors in the capacitor tower, generally considered to be less than 20%; ② The resistors, reactors, current transformers, lightning arresters, etc. in the filter device do not need to be replaced as a whole, and the local disassembly inspection and repair of the equipment or the replacement and maintenance of a part of the equipment can be completed on site; ③ Various routine tests and diagnostic test items before and after equipment processing; ④ Complex diagnostic test items to verify the quality of the equipment.
Class C maintenance
Class C maintenance is the routine inspection, maintenance and testing of AC/DC filters and shunt capacitor device.
Class C maintenance is: ① After the power outage, the appearance of the equipment is inspected and cleaned, and the equipment parts are repaired and repaired, which does not involve any replacement work; ② Routine testing of the equipment, generally does not include diagnostic testing of the equipment.
Class D maintenance
Class D maintenance is the live testing, appearance inspection and maintenance of AC/DC filters and shunt capacitor device without power outage.
Class D maintenance of equipment is relatively easy to define in reality, that is, any work on the equipment without power outage can be considered as Class D maintenance.
2.2 Maintenance items
The status classification and maintenance items of the maintenance of AC/DC filters and shunt capacitor devices are shown in Table 1.
Table 1 Classification of equipment status and maintenance items
Note With the continuous improvement of maintenance methods and the continuous application of new technologies, the original Class C maintenance may be partially converted into Class D maintenance. These require everyone to continuously apply new methods and technologies in future work to gradually reduce the workload. At the same time, on the other hand, the equipment has changed from power outage processing to the same processing work that can be completed without power outage, which also improves the equipment availability.
3 Maintenance strategies for filtering and shunt capacitor installations
The filter and shunt capacitor device maintenance strategy is how to carry out equipment maintenance work. Only after the equipment has undergone status evaluation and risk assessment, can its maintenance strategy be obtained. The maintenance strategy includes maintenance equipment, maintenance cycle, maintenance test items, etc. After the formulation of the maintenance strategy is completed, the on-site maintenance personnel will perform the corresponding maintenance work according to the strategy.
3.1 Requirements for filter and shunt capacitor device maintenance strategy
The status maintenance strategy for equipment reactors, capacitors, resistors, current transformers and lightning arresters in filter and shunt capacitor devices includes the formulation of annual maintenance plans, as well as defect handling, maintenance and inspection without power outages during testing. The maintenance strategy should be adjusted dynamically according to the results of the equipment status evaluation.
The annual maintenance plan should be revised at least once a year. According to the evaluation results of the most recent equipment status, consider the equipment risk assessment factors, and refer to the manufacturer’s requirements to determine the next power outage maintenance time and maintenance category. When arranging the maintenance plan, the maintenance cycle of related equipment should be coordinated and arranged as unified as possible to avoid repeated power outages.
For equipment defects, they should be handled according to the nature of the defects and the relevant provisions of defect management. If there are multiple defects in the same equipment, they should also be arranged to be handled in one maintenance as much as possible. If necessary, the maintenance category can be adjusted.
The normal cycle of Class C maintenance should be consistent with the test cycle. The non-stop maintenance items and test items of various types of equipment should be arranged according to the specific actual situation.
When the defect handling of current transformers and lightning arresters involves internal defect handling or disassembly, it is generally not arranged to be handled on site. Usually, spare parts are directly used for replacement, and then the faulty equipment is returned to the factory or handled in the maintenance workshop of the repair unit.
3.2 Maintenance strategy
The maintenance strategy of the filter and shunt capacitor device based on the status score is shown in Table 2.
Table 2 Maintenance strategy table of filter and shunt capacitor device
3.2.1 “Normal state” maintenance strategy
AC and DC filters and shunt capacitor device evaluated as “normal state” shall perform Class C maintenance. According to the actual condition of the equipment, Class C maintenance can be performed according to the normal cycle or extended for one year. Before Class C maintenance, Class D maintenance can be appropriately arranged according to actual needs.
3.2.2 “Attention state” maintenance strategy
AC and DC filters and shunt capacitor devices evaluated as “attention state” shall be subject to Class C maintenance. If the evaluation result is “attention state” due to the deduction of points for a single state quantity, Class C maintenance should be arranged in advance according to the actual situation. If the evaluation result is “attention state” due to the total deduction of points for multiple state quantities, it can be performed according to the normal cycle, and necessary maintenance and test content should be added according to the actual condition of the equipment.
AC and DC filters and shunt capacitor device evaluated as “attention state” should appropriately strengthen Class D maintenance.
3.2.3 “Abnormal state” maintenance strategy
AC and DC filters and shunt capacitor device evaluated as “abnormal state” shall determine the maintenance category and content according to the evaluation results, and arrange maintenance in a timely manner. Class D maintenance should be strengthened before implementing power outage maintenance.
3.2.4 “Severe Status” Maintenance Strategy
For AC and DC filters and shunt capacitor devices that are evaluated as “severe status”, the maintenance category and content shall be determined according to the evaluation results, and maintenance shall be arranged as soon as possible. Class D maintenance shall be strengthened before power outage maintenance.
[/fusion_text][/fusion_builder_column][/fusion_builder_row][/fusion_builder_container]
