Transformer oil leakage causes, transformer with oil plugging, transformer repair, transformer plugging, transformer repair manufacturers, transformer repair manufacturers, transformer plugging price, transformer oil leakage causes and repair technology

why

1, poor material. Poor sealing material and defect are the main reasons for leakage of transformer connection. More than 75% of transformer leakage oil is in the connection part, and the leakage oil caused by the failure of rubber seals accounts for more than 95% of the leakage oil in the connection part. Oil is leaking through the gap between the rubber seal and the connection interface. When the rubber seal does not fail, there is generally no leakage, because the rubber can fill and press the convex and concave surface under extrusion. The surface quality of the seal and the geometry of the oil leakage also have a certain impact, but the key is still the material performance of the rubber seal. Rubber seals are generally located between the upper cover of the tank, the upper and lower sections along the large and small flanges. In the operation of the transformer, they are in high temperature extrusion, oil immersion, local exposure conditions, especially the sealant on the insulating porcelain casing, with the transformer body in the vacuum tank to endure 115℃ high temperature and nearly 40h baking. Poor quality, especially the flat round rubber inside the porcelain tube, has begun to age, oil immersion began to deteriorate. Because it is in the upper part of the transformer tank, the size of the oil pressure is not uniform, although not leakage, but if the transformer movement or transportation shaking, vibration, coupled with the impact of oil will leak. Visible. Inferior rubber seals are easy to aging, deterioration, cracking, plastic deformation, and even failure. Is the main cause of oil leakage.

2. Influence of welding residual stress. Welding residual stress is another main reason for oil leakage of transformer weld. The oil tank has many solder spots, long welds, difficult welding, welding materials, welding specifications, welding technology and welding technology, etc., which will affect the welding quality. Especially, manual arc welding is more prone to weld burnthrough, porosity, slag inclusion, cracks and non-fusion defects. Among them, welding penetration defects may not be detected in the hydraulic seal test of the tank, which is also the cause of oil leakage. www.qdyuke.com

Welding is essentially a process of metal re-melting. The solution at about 1350℃ is quenched in the air, resulting in residual tensile stress of more than 200Mpa on the weld, which greatly reduces the fatigue strength. In special cases, the peak value of residual stress may be close to the fatigue strength of the weld. When the transformer is impacted and vibrated, these external forces superimpose the residual stress of the weld. Once the fatigue strength is exceeded, cracks will occur in the peak area of the residual stress but not in the defect of the penetration weld. The statistics show that the weld leakage accounts for 65%, and in the operation of the power transformer, most of the metal components are subjected to the frequency of 100HZ, the amplitude of the forced vibration is 6~60μm, the amplitude of the flat part of the box wall is 75~440μm. Because the welding seam latent residual stress, so transformer site often by impact, vibration and weld leakage oil.

3, transformer welding spot, welding seam is long. Oil-immersed power transformer is a combination of welding and connecting pieces based on steel plate welding shell. A 31500KVA transformer uses rubber seals to connect about 27 points, more than 30 rubber seals of various shapes, including the welding of both ends of the heat pipe and the fuel tank, the total welding spot is more than 70, the total length of the weld is about 20m, so the leakage way may be more. Direct leakage is caused by the failure of rubber seals and weld cracking, porosity, slag, etc.

4. Other reasons. In addition to seals and weld leakage oil, conductive copper rod of medium and small transformers, conductive copper plate of special transformers and the brazing place of the installation seat also often leak. Some manufacturers often use copper cast rod or plate instead of rolled rod or plate for various reasons. Cast copper is easy to produce porosity, loose and slag, often formed through channels and leakage. The brazing brittleness of conductive copper plate and support is very big, which may leak due to cracks in transformer installation wiring or operation, and the nut of transformer connection sealing part is often leaked due to vibration loose during transformer operation.

Some transformer neutral point is directly grounded,and some transformer neutral point is grounded through the gap.The protection of transformer neutral point is mainly to reflect the grounding fault.

Case 1:When a grounding fault occurs in the system,the neutral earthed transformer should be equipped with zero-sequence current protection,which can be composed of two sections,each with two time limits.The short time limit action is to disconnect the busbar or subsection circuit breaker to reduce the scope of the fault,and the long time limit action is to disconnect the circuit breaker on each side of the transformer.

Case 2:When a grounding fault occurs in the system,after the neutral earthed transformer is switched off,the zero sequence voltage rise or resonant overvoltage of the power grid will endanger the neutral insulation of the transformer that is not grounded.Therefore,neutral point ungrounded transformer should be installed with zero sequence voltage protection or gap zero sequence current protection.

(1)Graded insulated transformer

Large transformer is the core equipment of power production,because of its high cost,so in the 110 kV and above neutral point directly grounded power grid,the transformer with graded insulation is mostly used.

In actual operation,some of the neutral points of transformers are directly grounded.But some of the neutral points of the transformer are not grounded.The so-called graded insulation,is the transformer coil near the neutral part of the main insulation,the insulation level is lower than the insulation level of the coil end.

Problems should be paid attention to in the operation of graded insulated transformers:

1,the neutral point of graded insulation transformer must be equipped with arrester and prevent overvoltage gap;

2,if conditions permit,operation mode permits,graded insulated transformer must be grounded operation;

3,if the neutral point of graded insulated transformer is not grounded,the neutral overvoltage protection must be reliable input.

(2)key principles of transformer neutral point configuration

1,in the operation of the double bus,it should be considered when the bus switch trip,ensure that the two separate systems should have at least one transformer neutral point grounding;

2,transformer,low voltage side of the power supply,the neutral point of the transformer shall be directly grounded to prevent the trip of the high voltage side circuit breaker,the transformer becomes the neutral insulation system;

3.The neutral point of the main transformer of the generator-transformer-line group should be kept grounded.

(three)three forms of transformer neutral overvoltage

1.Atmospheric overvoltage

2.Overvoltage caused by single-phase grounding fault

3.Over-voltage caused by incomplete phase switching of circuit breaker(mainly manifested as non-synchronous reclosing,incomplete phase action and wire disconnection of circuit breaker in power grid)

(four)three ways of transformer neutral point clearance protection

Gap,arrester and arrester combined discharge gap can be used in three ways.

The transformer adopts the protection mode of arrester combined with discharge gap.

The discharge gap adopts rod-rod gap,and the arrester is mostly configured as zinc oxide arrester.

The protection division of the parallel gap of the lightning arrester is that the power frequency and operating overvoltage are borne by the gap,while the lightning and transient overvoltage are borne by the lightning arrester.At the same time,the gap is used to limit the power frequency overvoltage and residual voltage that may appear on the lightning arrester with too high amplitude.This way not only protects the neutral point of the transformer,but also plays a role of mutual protection.

(5)transformer neutral point gap overcurrent protection

To prevent overvoltage damage to the transformer neutral point insulation,for the main transformer neutral point is generally installed discharge gap measures,and the use of current transformer neutral point casing or installed in the discharge gap loop independent current transformer,a transformer neutral point discharge gap zero sequence current protection(hereinafter referred to as"clearance over-current protection)"

The principle of transformer neutral gap protection is shown in the figure below.

When is the voltage side neutral discharge gap protection put in,when to quit,why?

Should exit before the neutral point grounding switch is closed,and put in after the neutral point grounding switch is opened.(i.e.discharge gap protection and neutral point cannot be in the input state at the same time)

Because:discharge gap protection is composed of zero-sequence voltage and zero-sequence current in parallel,and the current setting is sensitive,the time is short,and there is no relationship with other protection.In the state of direct grounding,if there is an external fault,there will be zero sequence current flowing in the neutral point CT,which will cause the misoperation of clearance overcurrent protection.

In the clearance grounding state,in the occurrence of grounding fault,after other grounding changes jump,the neutral point zero sequence voltage will rise,so that the clearance zero sequence voltage protection action.After gap breakdown,zero sequence current action,protection ungrounded transformer.

In the use of transformer oil chromatography analyzer for chromatographic analysis of transformer oil,sampling this process directly determines the analysis effect,so before the operation should pay special attention to the matters needing attention when sampling,and today to please intelligent star about the details of the influence of sampling,let us do a reference.

A,whatever the type of transformer oil chromatographic analyzer,at the time of sampling sampling requirements must pay attention to,first of all,to be performed on the container operations,washed with distilled water or deionized water,and then clean with cleaning ethanol for container,and will be used in the oven to dry,there is a kind of method is also ensure the accuracy of the results of the analysis,That is to wash directly with water samples,but take samples immediately after washing.

Second,in the use of transformer oil chromatographic analyzer,pay attention to the sampling pipe must be with insulating oil produces chemical reaction,and has strong wear resistance,or you need to be replaced regularly sampling tube,and the material of the sampling pipe can't insulating oil catalytic effect,and also should pass before use of cleaning cleaning,such as ethanol You can also use distilled water and dry it.

Three,when the use of sampling tube in the oil drum sampling,but also pay attention to is to avoid the above oil,as far as possible by sampling,and found or suspected that there is free water in the oil,it is recommended to sample deep at the bottom,which is undoubtedly rigorous,but also after sampling to consider the cleaning of the sampling valve.This is for fear that the residual oil in the sampling valve will enter the sampling pipe and contaminate the sample,so these details should be observed.

Just mentioned is the use of transformer oil chromatography analyzer analysis,sampling process need to pay attention to the place,in fact,the whole sampling process should pay attention to the sample is not polluted,so usually to develop good operation habits,here it is recommended to refer to the equipment with the drug specification to sample,to ensure the results of analysis.

In the customers we have seen,when using frequency conversion power supply(CNZGys),the maintenance of frequency conversion power supply is not a lot,generally is to wipe the outside of the chassis,the ground around the chassis cleaning and so on.In fact,frequency conversion power supply(CNZGYS)maintenance,maintenance is very necessary:

First:it can increase the service life of variable frequency power supply(CNZGys).Originally,a variable frequency power supply(CNZGYS)can be used for 8 years.If your company's variable frequency power supply(CNZGys)is maintained and maintained well,it can be used for several years.In terms of the value of this variable frequency power supply(CNZGys),the service life is long,the cost is reduced,so the value of this variable frequency power supply(CNZGys)is improved.

Second:keep the frequency conversion power supply(CNZGys)stable use,not easy to break down.For example,some of the frequency conversion power supply(CNZGys)like Yangsheng in The use of 8-10 years later,has not been able to carry the full load.Especially when the load type is inductive load,there is a surge current when starting,at the beginning of the time can be directly at least,a long time will not be able to start so many equipment at once.If it is good maintenance,the time of this situation will be relatively late.

Here is how to maintain frequency conversion power supply(CNZGYS):

Time:It is recommended that periodic examinations should be carried out once a year.

Replacement of spare parts of frequency conversion power supply(CNZGys)

Frequency conversion power supply(CNZGys)consists of a variety of components,some of which will gradually reduce their performance and aging after long-term work,which is also the main reason for frequency converter failure,in order to ensure the long-term normal operation of the equipment,the following components should be replaced regularly:

1.Maintenance of cooling fan,which is related to the heat dissipation of frequency conversion power supply(CNZGys),especially in summer,the weather is hot,pay more attention to the heat dissipation problem.Frequency conversion power supply(CNZGys)power module is the most serious heating device,the heat generated by its continuous work must be discharged in time,the life of the general frequency conversion power supply(CNZGys)cooling fan is about 10KH-40KH.According to the frequency conversion power supply(CNZGys)continuous operation converted to 2-3 years to replace a fan,direct cooling fan has two and three points,two line fan one line is positive,the other line is negative,do not replace the wrong;In addition to the positive and negative poles of the three-line fan,there is a detection line,pay attention to the replacement,otherwise it will cause the frequency conversion power supply(CNZGys)overheating alarm.Ac fans are generally divided into 220V and 380V,and the voltage level should not be mistaken when replacing them.

2.Filter capacitor,ensure the normal output of frequency conversion power supply(CNZGys),voltage,sine wave stability.

The filter capacitor of the intermediate circuit:also known as electrolytic capacitor,its main role is to smooth the DC voltage,absorb the low frequency harmonics in the DC,the heat generated by its continuous work and the heat generated by the frequency conversion power supply(CNZGys)itself will accelerate the drying of its electrolyte,directly affecting the size of its capacity.The normal service life of the capacitor is 5 years.It is recommended to check the capacity of the capacitor periodically once a year,and replace the capacitor if the capacity is reduced by more than 20%.

Notes for use of variable frequency power supply(CNZGys)

1,high pressure test please pay attention to safety,strictly in accordance with the specification of high pressure test to operate.Please shut down the system and cut off the power supply before checking/modifying the test wiring.

2.According to the highest voltage of frequency conversion power supply(CNZGys),the actual high voltage can be raised to is determined by the excitation transformer,and the appropriate excitation transformer can be replaced according to the test voltage.

3.If the transformer makes abnormal sound after starting up,please immediately shut down the system and cut off the power supply to check whether the transformer wiring is correct.

4,normal"stop"adopts the way of step-down stop,protection stop direct quick stop,in case of emergency can directly disconnect the air switch directly shut down.

5.If the automatic frequency sweep fails,check the cable connection or reset the frequency sweep range.

Clean and maintain

Clean air filter cooling air duct and dust inside.Check whether screws,bolts and plug-ins are loose,and whether the ground and phase resistance of input and output reactors is short-circuit.Normally,it should be more than tens of megohm.Conductors and insulators should be cleaned with alcohol in time.