How to Protect Transformer?

This article describes in detail how to protect the main transformer.

25 measures can help your main transformer policy operation. Effectively prevent accidents such as main transformer damage and transformer explosion.

Daelim has been in the industry for 15 years, focusing on transformer production and R&D of transformer manufacturer. It has a number of independent research and development technologies, and an experienced main transformer design and R&D team. 

Can provide you with professional design and complete after-sales service. Daelim has after-sales service teams in many countries and can provide professional installation services. Ensure that everything you do in purchasing transformers and transformer operations is smooth and efficient.

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Strengthen the management of the whole process of transformer equipment selection, ordering, acceptance, and commissioning, and clarify the personnel responsible for transformers and their responsibilities

Check and accept newly purchased transformer equipment in strict accordance with relevant regulations to ensure that the improvement measures are implemented in the equipment manufacturing, installation, and test stages, and no problems of the same type are left when it is put into production.

Before ordering, you should obtain the test report of the transformer that has undergone a sudden short-circuit test and the dynamic calculation report of the short-circuit resistance capability from the manufacturer; before the design liaison meeting, the calculation report of the short-circuit resistance capability of the ordered transformer should be obtained.

Transformers with voltage levels of 220kV and above should go to the factory for supervision and acceptance. The supervision should be carried out according to the requirements of the key control points for the supervision of the transformer to the factory. After the supervision and acceptance work is completed, the personnel who go to the factory should submit the supervision report, which shall be used as the original equipment Data archive.

Qualified standards for the factory partial discharge test.

For 220kV and above transformers, when the measured voltage is 1.5Um/√3, the medium voltage terminal of the autotransformer is not more than 200pC, and the others are not more than 100pC.

110kV transformer, when the measured voltage is 1.5Um/√3, not more than 300pC.

For the transformer of the neutral grounding system, when the measuring voltage is 1.0Um/√3, the liquid immersion is not more than 10pC, and the solid type is not more than 50pC. When the measuring voltage is 1.2Um/√3, the liquid immersion is not more than 5pC, and the solid type is not more than 20pC.

Transformers with voltage levels of 220kV and above shall be subjected to dielectric loss test under high voltage.

Ask the manufacturer for the factory inspection report of the main materials and accessories and the manufacturer’s factory test report; during the factory test, the supplied bushings should be installed on the transformer for testing; all accessories should be pre-installed as a whole according to the actual use when leaving the factory. pass.

Carry out the handover test procedures carefully; for 110kV and above voltage level transformers, low-voltage short-circuit impedance test or frequency response method should be used to test the winding deformation before leaving the factory and put into production to keep the original record. Transformers with a voltage level of 220kV and above and a capacity of 120MVA and above must undergo on-site partial discharge tests when they are newly installed. Transformers with voltage levels of 220kV and above must undergo on-site partial discharge tests after overhaul.

During the transportation of large transformers, a three-dimensional impact recorder with a time scale and a suitable range should be installed in accordance with the specifications. After arriving at the destination, the three parties of the manufacturer, the transportation department and the user should jointly check and accept, and the recording paper and escort records should be provided to the user for retention .

When purchasing equipment, the manufacturer should be required to have reliable and sealing measures. For equipment in operation, such as poor sealing, improvement measures should be taken to ensure that the transformer and transformer are prevented from entering water or the air is damp. Strengthen operation inspections, and pay special attention to oil leakage in the negative pressure area of ​​the transformer cooler submersible pump. Prevent accidents caused by casing, lead wire and tap changer. If the distance between the umbrella skirts of the casing is lower than the standard, measures such as adding silicone rubber umbrella skirts should be taken to prevent rain flash accidents.

The bearings of the submersible pump should be E-class or D-class. Bearings without nameplates and no grades are prohibited. The oil pump should be a low-speed oil pump with a speed not greater than 1000r/min. In order to ensure the cooling effect, the air cooler should be flushed with water regularly.

The transformer body and the heavy-watt protection of the on-load switch should be tripped. If the heavy-duty protection needs to be withdrawn, safety measures should be formulated in advance, approved by the chief engineer, and restored within a time limit.

For 220kV and above voltage level substation equipment, infrared imaging temperature measurement inspection must be carried out at least once a year. Take effective measures in terms of technology and management to prevent or reduce the output short circuit of the transformer as much as possible, and improve the operating conditions of the transformer. After the transformer is subjected to a sudden short circuit in the near area, it should be tested for low-voltage short-circuit impedance or the winding deformation by frequency response method, and compared with the original record, before it can be put into operation after judging that the transformer is fault-free.

New or expanded transformers generally do not use water cooling. For special occasions, water cooling systems must be used, and double-layer copper pipe cooling systems should be used. For the single-copper-tube water-cooled transformer currently in normal use, the oil pressure should always be kept higher than the water pressure, and maintenance should be strengthened, and effective operation monitoring methods should be adopted to discover the leakage failure of the cooling system in time.

For thin insulating transformers, technical supervision can be carried out according to general transformer equipment. If serious defects are found, the transformer body should not undergo transformational overhaul, and the replaced thin insulating transformers should not be relocated and installed.

The quality control of the new transformer oil should be strengthened, and the user can select the appropriate oil type according to the operating experience. After the oil arrives at the site, it should be sampled and tested before it can be injected into the equipment. Strengthen oil quality management, strictly implement relevant standards for the oil in operation, and be cautious about the blending of different oil types.

Improve the fire-fighting facilities of transformers in accordance with regulations, and strengthen management, focusing on preventing the expansion of accidents when transformers catch fire.

Prevent problems with casing.

After the bushing is installed in place, it must be left still before being electrified. The static time of 500kV casing shall not be less than 36h, and that of 110~220kV casing shall not be less than 24h.

protect the transformer

For 110kV and above bushings with a storage period of more than 1 year, partial discharge test, dielectric loss test under rated voltage and oil chromatographic analysis should be carried out before installation.

For the casing installed in the emergency repair of the accident, an oil sample should be taken for a chromatographic test within 3 months after it is put into operation.

The 110 kV and above bushings used as spare parts should be placed indoors and vertically. If stored horizontally, the elevation angle should be in accordance with the manufacturer’s requirements to prevent the capacitor core from being exposed to the oil surface and getting damp.

When casing oil leaks, it should be dealt with in time to prevent internal damage caused by moisture.

About Bin Dong

Hello, I am Bin, General manager of Daelim which is a leading transformer manufacturer. If you have problems when you are looking for the equipment, what you need to do is tell us.

Custom Power Transformer

When you need to find more than just existing transformers, Daelim’s Transformer Service Center can help you design and produce distribution transformers that meet your unique needs.

We have our own factory and a professional team of engineers, which can design and modify application requirements that meet all your conditions.

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