The safe operation and management of transformers is the focus of everyone’s daily work. Based on the experience exchange of abnormal operation conditions and common problems analysis of transformers, it will be helpful to immediately and accurately determine the causes and characteristics of common faults, and take immediate measures to ensure The safe operation of machinery and equipment. The variable frequency series resonance test equipment adopts the method of multi-level accumulation. Several series reactors can be applied in parallel or series. The voltage divider can be used to accurately measure the experimental working voltage, and can also be used as a reactive power compensation cabinet for small-capacity samples to promote series connection. Resonance can be completed in the range of 30 to 300 Hz.
Transformer
Transformers are vital electrical equipment in the power transmission and distribution system. According to the operation and maintenance management regulations, transformers must be inspected on time to facilitate timely understanding and grasp of the operating conditions of the transformers, and timely measures and countermeasures to eliminate common faults in the budding period. , Thereby ensuring the safe operation of the transformer. Now let’s talk about the common fault relay protection action, the characteristics of the current transformer and the impact of the importance on the fault.
Reasons for light gas action
Common faults in the secondary circuit of protection equipment
Based on the equivalent circuit diagram of the current transformer, the basic principles and characteristics of the two current transformer ratio inspection methods (current method and voltage method) are discussed. A simple and reliable current transformer ratio inspection field experiment is strongly recommended. Method-voltage method. From the perspective of application, this article summarizes several types of wiring methods of current transformers in the differential protection of dual-coil transformers based on the analysis of the basic principles of wiring; at the same time, it introduces the situation in which the polarity of the current transformer is unknown. Next, the wiring method of the current transformer in the dual-coil transformer differential protection.
- Based on the equivalent principle diagram of the current transformer, discuss the basic principles and characteristics of the two current transformer transformation ratio inspection methods (current measurement method and working voltage method), and strongly recommend a simple and reliable current transformer transformer Compare and check on-the-spot experiment method-voltage method.
The on-site transformation ratio inspection experiment during the work handover of the current transformer and after the winding is dismantled and replaced is included in the important test items. Although the accuracy of the transformation ratio of the current transformer should be ensured by the manufacturer, for various reasons, errors can occasionally be checked during field tests (most of which are tapped errors). Therefore, the on-site transformation ratio inspection experiment has become a constant project for many years.
The principle of the current transformer is about the same as that of the transformer. The difference is that the alternating main magnetic flux in the transformer core is formed by the alternating voltage across the primary coil, while the alternating main magnetic flux in the current transformer core is formed by the primary Formed by the current in the coil, the primary main magnetic flux magnetically induces a secondary electric potential in the secondary coil to form a secondary current.
From the principle of current transformer, it is known that it is the ratio of the number of primary turns and the number of secondary turns that determines the transformation ratio of the current transformer. The main reasons affecting the deviation of the transformation ratio of the current transformer are: (1) The magnitude of the current, the ratio difference and the The angle difference expands with the decrease of the secondary current; (2) the size of the secondary load, the ratio difference and the angle difference decrease with the decrease of the secondary load; (3) the secondary load power factor, which is accompanied by the secondary load power factor Expansion, the ratio difference is reduced and the angle difference is enlarged; (4) the influence of switching power supply frequency; (5) other factors. The main internal parameters of the current transformer are also likely to cause the transformation ratio deviation, such as the characteristic impedance of the secondary electromagnetic coil, the core cross section, the core material, the number of secondary turns, etc., but it is determined by the design and manufacturing.
The deviation test of the current transformer change should be carried out by the manufacturer during the factory test or in the laboratory. The field test of the current transformer ratio is attributable to the nature of inspection, that is, it is important to check the turns ratio without considering the above-mentioned hazards to the deviation of the current transformer ratio. According to the basic principles of electric welders, the coil turns ratio is equivalent to the reciprocal of the voltage ratio or the current ratio. Therefore, measuring the working voltage ratio and accurately measuring the current ratio can measure the coil turns ratio.
