Law and characteristics of electrical equipment overheating and prediction methods - News - Global IC Trade Starts Here Free Join

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1. External thermal fault

The external thermal fault of electrical equipment mainly refers to the bare joint due to poor crimping, etc., under the action of large current, the joint temperature increases, the contact resistance increases, and the vicious circle causes hidden dangers. Such failures account for more than 90% of external thermal faults. Counting the thousands of data of external thermal faults detected in recent years, it can be seen that the thermal faults of the clamps and the blade contacts account for 77% of the total external thermal faults, and their average temperature rise is about 30 °C. The average temperature rise of the external joint is between 20-25 °C. Combined with the experience of testing in recent years, the external fault can be divided into slight, general and severe according to the temperature rise.

2, internal thermal fault

The internal thermal fault of high-voltage electrical equipment is characterized by the fact that the fault point is sealed in an insulating material or a metal casing. For example, a cable, internal thermal faults generally have a long heating time and are relatively stable, and heat transfer occurs with the conductor or insulating material around the fault point, so that the local temperature It rises so that internal faults in high-voltage electrical equipment (such as cables) can be diagnosed by detecting the temperature rise of the material around it.

3. The part of the cable overheating fault

According to the analysis of electric power accidents, cable overheating failure can cause large-area cable burning due to fire, resulting in forced shutdown, unable to resume production in a short time, causing major economic losses. Through the analysis of the accident, the overheating of the cable joint is the direct cause of the cable fire. The cable joint is overheated because the joint pressure is not tight, the joint oxidation is excessive, and the contact resistance is too large. The long-term high temperature operation causes the insulation to fall and break down, eventually leading to The occurrence of a cable fire.

4. Prediction method for cable overheat fault

According to the analysis of cable overheat fault characteristics, an effective method to prevent cable overheating and fire occurrence is to timely monitor the cable joint temperature, analyze the aging degree of the cable joint according to the change trend of the joint temperature, and issue an alarm before the cable joint actually fails.

Most of the cables with overheating of the joint are high-voltage cables of 6KV or higher. Due to the high voltage level, the conventional temperature sensor can not meet the safety requirements. However, the traditional optical fiber temperature measuring system has the disadvantage of long scanning time. PIONEER-P fiber The grating temperature measurement system is the best choice for monitoring the overheat fault of high voltage live equipment.