Analysis of Abnormal Operation and Common Faults of Transformers

 The safe operation management of transformers is the focus of our daily work. Through the experience summary of abnormal operation conditions and common fault analysis of transformers, it will be beneficial to timely and accurately judge the cause and nature of faults, take effective measures in time, and ensure the safe operation of equipment.Variable frequency series resonance test device adopts multi-stage superposition method. Multiple reactors can be used in parallel or series. The voltage divider is used not only to measure the test voltage, but also as a compensation capacitor for small-capacity test objects, so that the resonance frequency can be completed within the range of 30-300Hz.

Transformers are extremely important electrical equipment in power transmission and distribution systems. According to operation and maintenance management regulations, transformers must be inspected regularly to timely understand and grasp the operation status of transformers, take effective measures in time, and strive to eliminate faults in the bud, thereby ensuring the safe operation of transformers. Based on the experience of transformer operation and maintenance management, the abnormal operation and common faults of transformers are analyzed and summarized as follows:

   1. Abnormal sound of transformer

   1. When single-phase grounding occurs in the power grid or resonance overvoltage occurs, the sound of the transformer is sharper than usual;

   2. When a large-capacity power equipment starts, the load changes greatly, causing the transformer sound to increase. For example, when the transformer has loads such as arc furnace and silicon controlled rectifier, due to harmonic components, the transformer will momentarily emit a "wah wah" sound or a "ge ge" intermittent sound;

   3. Overload causes the transformer to emit a very high and heavy "humming" sound; 

   4. If individual parts are loose, such as the core clamping bolts not being tightened properly or missing parts on the core, the transformer emits strong and uneven "noise" or sounds like "hammering" and "blowing";

   5. Poor internal contact or insulation breakdown in the transformer causes the transformer to emit "crackling" or "squeaking" sounds, and the sound changes with the distance from the fault point;

   6. When the system short-circuits or grounds, a large short-circuit current flows, causing the transformer to emit "crackling" noise, and in severe cases, there will be a huge roar;

   7. When ferroresonance occurs in the system, the transformer emits uneven noise.

  2. Under normal load and normal cooling methods, the transformer oil temperature continuously rises

   1. Both eddy currents and insulation damage of the core clamping bolts can cause the transformer oil temperature to rise. After the insulation of the clamping bolts is damaged, the insulation between the bolts and the silicon steel sheets is destroyed, and a large current flows through the bolts, causing them to heat up and also raising the oil temperature.

   2. Partial interlayer or inter-turn short circuits in windings, faults in internal contacts, increased contact resistance, and large resistance short circuits on the secondary line can also cause the oil temperature to rise.

  3. Significant change in the color of transformer insulating oil

  During operation, insulating oil may come into contact with air and gradually absorb moisture from the air, thereby reducing insulation performance. At the same time, insulating oil may also absorb and dissolve a large amount of air. Since the oil often operates at higher temperatures, it reacts with oxygen in the air to generate various oxides, and these oxides are acidic, which can easily corrode the metal and insulating materials inside the transformer, increase the dielectric loss of the oil, subsequently reduce the insulation strength, cause flashover inside the transformer, and easily lead to breakdown between windings and the shell.

  4. Oil spray from oil conservator or explosion-proof pipe

  When the secondary system suddenly short-circuits and the protection refuses to operate, or there is an internal short-circuit fault and the vent and explosion-proof pipe are blocked, the internal high temperature and heat will cause the transformer oil to suddenly spray out. After spraying, the oil level drops, which may cause the gas protection to operate.

  5. Three-phase voltage imbalance

   1. Unbalanced three-phase load causes neutral point displacement, resulting in three-phase voltage imbalance;

   2. ... (truncated)