66kv Transformer Fault Analysis For a 66kV transformer secondary winding deformation fault case, we elaborated
The 500kV Transformer is the core equipment in the ultra-high voltage grid, and when it has a major equipment failure, it often needs to be solved by replacing the transformer.
The use of the transformer transfer replacement technology can significantly compress the outage maintenance time, reduce the construction input, and effectively improve the grid reliability. The workflow, construction method, safety and quality control, engineering practice and effectiveness of the 500 kV transformer transfer replacement technology are introduced for the reference of colleagues.
As the core equipment of the ultra-high voltage grid, 500 kV transformer, once a major failure occurs in the field that cannot be repaired, often needs to be solved by replacing the transformer with a new one, while the traditional transformer replacement mode requires the following steps: fault transformer blackout → removal of electrical connection of the fault transformer → cooling oil discharge of the fault transformer → removal of the fault transformer accessories → the fault transformer body is moved out of the main transformer foundation → the fault transformer body accessories are removed from the substation. Faulty transformer body accessories evacuate the substation → new transformer body accessories into the field → the key components test qualified → new transformer body unloading in place → transformer accessories installed → vacuum hot oil cycle → static → high voltage electrical test → new transformer electrical connection → restore power supply operation.
Due to the many operational links and long chains, a set of three 500 kV transformer replacement requires more than 40 days of power outages, which can cause extensive and prolonged power outages and power restrictions during maintenance. How to minimize the transformer replacement operation time and resume power supply operation as soon as possible is extremely important to ensure the power supply reliability of the grid.
The 500 kV transformer whole assembly transfer replacement technology is mainly through the workflow optimization and construction process innovation, realize the fault transformer and the new transformer in the transformer body and high voltage casing, radiator, oil storage cabinet, fan, connecting tube and oil valve and other accessories in the normal connection, transformer full of oil, transformer overall electrical test qualified state of the handling replacement operation.
This operation method in the workflow will be most of the new transformer installation test work moved to the fault transformer before the power outage, the fault transformer disassembly, evacuation work moved to the new transformer to restore power supply operation, thus can significantly reduce the power outage repair time; in the construction process is mainly adopted to improve the hydraulic shock-free shift steering, operation and vibration real-time monitoring, narrow space, multiple work surface installation test, etc. technology, to ensure the safety and quality of the old and new transformers in the overall handling process.
With the adoption of the transformer transfer technology, a group of three 500 kV transformer replacement outage time can be reduced to about 20 days, its economic and social benefits are very significant. Requirements and operational difficulties of transformer assembly and transfer.t
The workflow was reorganized and optimized, moving most of the new transformer installation test work to before the fault transformer outage, and moving the disassembly and evacuation of the fault transformer to after the new transformer resumed power supply operation to shorten the substation outage maintenance time as much as possible.
The optimized 500 kV transformer replacement operation flow is as follows: planning handling route → operation area rectification and isolation → arrangement of transformer temporary installation platform → new transformer body accessories into the field → new transformer body in temporary installation platform unloading in position → transformer oil and key accessories test qualified → installation of new transformer accessories → vacuum → hot oil circulation → static → high voltage test qualified → fault transformer outage → removal of fault Transformer electrical connection → fault transformer whole move out of the foundation → new transformer whole carry on the foundation → restore the new transformer electrical connection → new transformer to resume operation → fault transformer oil discharge → demolition fault transformer accessories → fault transformer body and accessories withdrawal from the field.
In the optimized transformer replacement operation process, many faulty transformer removal and new transformer installation work test need to be carried out simultaneously in the substation, in order to avoid mutual interference between the two operations, should be based on the actual conditions of the substation, according to local conditions, scientific planning of the work site and handling route.
Transformer temporary installation platform should be as close as possible to the faulty transformer, in order to reduce the handling workload, but also need to leave enough machinery, personnel access, and high-voltage live equipment to maintain sufficient safety distance.
Usually, the transformer expansion area reserved by the substation, the “T” intersection at the end of the substation channel, the outdoor yard adjacent to the office and living area, and the green belt on the opposite side of the transformer foundation, these areas can be selected as the transformer temporary installation platform after reinforcement by rectification.
During the construction period, the transport channel may be occupied for a long time, so the plan of detouring machinery and personnel during the occupation period should be planned in advance.
The construction process mainly adopts the combined transformer temporary installation platform, improved hydraulic jacking and sliding, operation and vibration real-time monitoring, installation in narrow spaces and other technologies to ensure the safety of the old and new transformers in the overall transfer and replacement process.
First of all, the selected location should be surveyed to ensure that there are no pipe trenches or pits under the platform location and the ground is repaired and leveled.
Use large combined beam steel formwork to build temporary installation platform, each module in place between the splicing, both sides to heavy-duty buckle locking, so that it meets the overall installation of the main transformer test bearing, stability requirements.
On the transformer overhang more high-voltage casing, heat sink, oil pipe, switch and valve body and other vulnerable, key parts to take support, bundling and wrapping and other ways to strengthen and protect, to avoid damage in the handling operations.
Transformer shift transfer route in advance must be underground survey, identify underground pipelines, ditch pit location, good reinforcement and protection measures; fill the potholes with sand and gravel or hardwood board, and then dense pavement thick steel plate reinforcement to enhance the ground bearing capacity;.
Choose straight 50 kg/m heavy steel rail to lay the sliding track, spell long joints at both ends of the rail should be padded in the same board, there shall be no leave empty.
Installed on the rail slide track settlement real-time monitoring system, can real-time sensitive feedback ground settlement situation. Transformer temporary installation platform as shown in Figure 1, heavy rail paving as shown in Figure 2.
The main equipment selected is 70 MPa high-pressure oil pumping station, 250 t hydraulic jack, 30 t hydraulic thruster and 30 t sequential follow-up hydraulic clamps each 4, multi-way synchronous balance combination valve, feedback type proportional remote control each group. Among them, the multi-way synchronous balance combination valve mainly ensures multiple jacks synchronous jacking and multiple thrusters with the same speed horizontal propulsion, feedback proportional remote control for the operation of the command according to the remote feedback display of oil pressure, stroke and speed data, real-time monitoring of the load size and operating conditions, adjust the jacking and propulsion speed by adjusting the high pressure rotary valve opening degree, so that the transformer jacking and landing, propulsion and sliding more smooth, more reliable and more intelligent.
Due to the large transformer components, large size, heavy tonnage and high requirements, it is appropriate to install three vibration impact recorders on the transformer at the same time, which are installed in the lower part of the transformer body, the top of the body box, and the flat position of the upper end of the high voltage casing.
The IMS-200 intelligent monitoring terminal is selected for the vibration recorder, which can monitor the three-dimensional vibration value, internal air pressure, longitudinal and transverse inclination of the main transformer, moving speed and temperature and humidity changes of the transformer in real time through 4G remote data communication and Bluetooth near-field communication technology at the cell phone mobile end and computer end.
In the transformer jacking position, slide rail slide plate position and other key positions, casing, radiator and other weak positions to add removable magnetic suction conduit type video monitoring device, monitoring device can be achieved through 4G communication remote monitoring, while through the Light bridge digital wireless map technology to support real-time monitoring of four mobile terminal in the 300 m distance range (data delay is less than 0 . At the same time, the operation commander can use 433M RF remote control to switch cameras conveniently, so that abnormalities can be investigated in real time during the operation.
To accommodate simultaneous installation or removal operations on multiple working surfaces in live-run substations, a convenient small electric crane is applied, which has a compact electric rotating and telescoping boom and can carry out work apparatus handling operations at the bottom of height-constrained radiators.
The application of the assembled lifting derrick that climbs on the side of the transformer body to complete the vertical lifting of transformer parts under compact space conditions can significantly improve the installation and removal efficiency.
Adopting the whole-assembly transfer method to replace large power transformers can significantly reduce the outage maintenance time of hub substations, quickly restore power supply, and effectively improve the reliability of the power grid, so it has greater promotion and application value in the fields of short-circuit resistance of power transformers, transformer capacity increase transformation and abnormal disposal.
At the same time, the 500 kV transformer transfer operation has high requirements on the management ability of the construction enterprise, the operation equipment and personnel team. The construction unit should formulate a scientific construction operation plan in advance, take strict measures to prevent high-voltage electric shock, equipment protection and vibration damping, strengthen the operation process management and ensure the quality of the project in order to achieve the expected results.
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