The previous articles have introduced the minor repair cycles and projects of transformers in detail, as well as specific project operations. The next article will describe the major repair cycles and projects of transformers. Knowledge about the transformer overhaul cycle, how often the transformer is overhauled, how to define the transformer overhaul cycle, what are the transformer overhaul items, and what quality standards are used to check whether the transformer overhaul work is completed in accordance with the regulations, let’s learn together.
1. Transformer overhaul cycle
(1) Generally, it will be overhauled within 5 years after being put into operation and every 10 years thereafter.
(2) For fully-sealed transformers welded along the box edge or as otherwise specified by the manufacturer, overhaul shall be carried out only when it is determined that there is an internal fault or serious oil leakage from the body after testing and inspection combined with the operating conditions.
(3) After the main transformer running in the power system is subjected to a short circuit at the outlet, after comprehensive diagnosis and analysis, it can be considered for overhaul in advance.
(4) For transformers in operation, when abnormal conditions are found or internal faults are found through tests, overhaul should be carried out in advance; transformers that are in normal operation have been comprehensively diagnosed and analyzed, and approved by the chief engineer, the overhaul period can be appropriately extended.
2. Transformer overhaul project
(1) Lift the bell to overhaul the body, or lift out the body for overhaul.
(2) Overhaul of windings, leads and magnetic (electrical) screen wear devices.
(3) Overhaul of iron core, iron core fasteners (through-core screws, clips, pull straps, straps, etc.), pressure nails, pressure plates and grounding sheets.
(4) Overhaul of fuel tank and accessories, including casing, moisture absorber, etc.
(5) Maintenance of auxiliary equipment such as coolers, oil pumps, water pumps, fans, stuffy doors and pipes.
(6) Maintenance of safety protection devices.
(7) Overhaul of the oil protection device.
(8) Calibration of the temperature measuring device.
(9) Overhaul and test of operation control box.
(10) Maintenance of off-excitation tap-changer and on-load tap-changer.
(11) Replacement of all gaskets and component leak testing.
(12) Dry the insulation of the body if necessary.
(13) Treatment or oil change of transformer oil.
(14) Clean the fuel tank and spray paint.
(15) Test and trial operation of overhaul.