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Date：07-08-2021
Transformer is a continuous operation of static equipment, more reliable operation, less chance of failure.But because the vast majority of transformers are installed outdoors, and are affected by the operation of the load and the influence of the power system short circuit fault, in the process of operation, there are inevitably all kinds of faults and abnormal circumstances.
1. Common faults and anomalies of transformers
2. Configuration of transformer protection
3. Non-electricity protection
(1) Gas protection
(2) Pressure protection
(3) Temperature and oil level protection
(4) Cooler full stop protection
4. Differential protection
(1) Magnetizing inrush current of transformer
(2) Principle of second harmonic restraint
(3) Differential quick-break protection
Briefly introduce these on the main protection of the transformer, and continue to introduce the backup protection of the transformer. There are many types of backup protection configurations for transformers. Here is a brief introduction to the two types of backup protections, the overcurrent protection and the grounding protection of the transformer.
1. Overcurrent protection with re-pressure lockout
2. Grounding protection of transformer
The backup protection for grounding short-circuit faults of large and medium-sized transformers usually includes: zero sequence overcurrent protection, zero sequence overvoltage protection, gap protection, etc. The following is a brief introduction based on the three different grounding methods of the neutral point.
(1) The neutral point is directly grounded
(2) The neutral point is not grounded
(3) The neutral point is grounded through the discharge gap
The ultra-high voltage transformers are all semi-insulated transformers, and the ground insulation of the neutral point coil is weaker than other parts. The neutral point insulation is easily broken down. Therefore, gap protection needs to be configured.
The function of the gap protection is to protect the insulation safety of the neutral point of the ungrounded neutral point of the transformer.
The gap protection is realized by using the gap current 3I0 flowing through the neutral point of the transformer and the open delta voltage 3U0 of the busbar PT as the criterion.
If the neutral point of the fault rises to the location, the gap breaks down and a large gap current 3I0 is generated. At this time, the gap protection is activated and the transformer is cut off after a delay. In addition, when a ground fault occurs in the system, the neutral point is grounded and the zero sequence protection of the transformer is operated, and the neutral point is grounded first. After the system loses the grounding point, if the fault still exists, the open delta voltage 3U0 of the busbar PT will be very large, and the gap protection will also operate at this time.
