Fault diagnosis and condition based maintenance during transformer operation
Writer： Hengfeng you electric Time：2023-04-07 views：times
Transformer is one of the most important components in the power system. At the same time, it is also the equipment with high failure rate. During the operation of transformer, it is necessary to carry out fault diagnosis and condition based maintenance at any time.
Transformer fault diagnosis
The fault of transformer is complex and involves many aspects, especially in operation. Once a fault occurs, it is difficult to judge which problem occurs. However, the general fault types of transformers can be divided into several types. The most frequent fault is the transformer outlet short-circuit fault, which has the most serious impact on the transformer. These are generally due to overheating or discharge. This paper will focus on the following fault types.
1.1 outlet short circuit fault
Transformer Outlet short-circuit fault refers to that when the outlet is short circuited, the low-voltage winding can pass through a large short-circuit current dozens of times higher than the rated value at the same time, which will produce considerable heat and make the transformer heat. In this case, if the short-circuit current is small and the protection is timely, the damage will be small; If the short-circuit current is large and the protection is not timely, the winding will be seriously deformed. If it continues to operate, it will lead to many faults.
1.2 core failure
The iron core is one of the main equipment for transformer to transform voltage and energy transfer, and the iron core is often prone to failure. It may be caused by improper selection of raw materials or poor technology of the iron core itself, poor contact of the iron core, or damage of the iron core itself. When the transformer is in normal operation, only one point grounding of the iron core is the normal safe grounding. If multiple points grounding, the iron core will discharge in the high-voltage electric field, which may lead to overheating of the winding, damage to the insulation strength of the oil and burn the iron core.
1.3 winding fault
The winding of power transformer is the core component, and the electrical quantity is involved in the transformer. There are also many faults in the winding. Its faults mainly occur in the winding insulation, winding grounding short circuit, winding damp, winding mechanical damage caused by system short circuit, inter turn short circuit between wire turns, winding fracture and short circuit between single-phase or each phase winding.
1.4 tap changer failure
The tap changer plays a role in the high-voltage circuit in the transformer. It is divided into the faults of on load tap changer and off load tap changer. When the insulation distance between the upper tap is not enough and there is damp oil sludge on the insulating material, there may be phase to phase short-circuit fault; In case of poor contact or high resistance, discharge and other faults will occur.
The fault of on load tap changer is mainly in the dialing wheel, contact and other places, and the insulation performance is reduced due to external force; Or the roller is stuck, causing the on load tap changer to be stuck in the transition position, resulting in a short circuit; And deformation of on load tap changer.
Transformer condition based maintenance
2.1 how to carry out condition based maintenance
Firstly, check the transformer, find out the contents and items that need to be repaired, select the maintenance methods scientifically and pertinently, and repair the transformer regularly to improve the safety of the equipment and reduce the maintenance cost. Improve the detection system, maintenance system and information management system.
Condition based maintenance always puts "safety first" in the first place to improve the safety and management level of the transformer. Only by checking at any time and finding problems and faults can the equipment be repaired and the principle of safety be guaranteed.
2.2 three stages of transformer condition based maintenance
The maintenance of transformer should go through three stages: fault diagnosis, regular maintenance and condition based maintenance. Fault diagnosis is to check the transformer after fault, which will lead to low work efficiency and high maintenance cost.
During regular maintenance, according to the characteristics of the transformer and the experience of experts on transformer failure, the equipment shall be inspected and repaired within a certain period planned in advance, but during maintenance, attention must be paid to "appropriate" maintenance. For sealed things, windings, iron cores, etc., timely and careful maintenance shall be carried out, because improper or frequent maintenance may have the opposite effect and lead to transformer failure.
Condition based maintenance is to predict the future state of the transformer, predict the possible faults of the equipment, and analyze the maintenance mode based on the transformer state obtained by comprehensive analysis.
2.3 detection and diagnosis technology and condition based maintenance
The status of the detection transformer is divided into the detection of transformer status, fault analysis, prediction of equipment status, maintenance plan and plan implementation.
2.3.1 find the fault accurately based on fuzzy processing technology. The structure of transformer is complex, so there are many uncertain factors in fault diagnosis, whether it is iron core, winding, insulation, voltage, etc. Therefore, in fuzzy processing technology, we know a roughly range of fault area, and then integrate various technologies and experience to repair the transformer.
2.3.2 at present, most of the condition based maintenance methods of transformers are still decision tree method to collect the relationship between monitoring indicators and faults.
