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Fire causes and preventive measures of phase-shifting capacitor

phase-shifting capacitor is a common reactive power compensation device. It improves power, saves electricity, is simple to install, and is easy to operate and maintain. It is widely used in industrial and agricultural production. At the same time, it has the characteristics of short service life, inconvenient to repair after damage, and suitable for fire and explosion accidents. On March 9, 1995, the metal door and window factory in Lucun, Yiyuan County caught fire due to the explosion of capacitors, resulting in a direct economic loss of 91730 yuan. The Timken ring of the capacitor is installed on a mandrel. Fires often occur when the power supply is restored, especially at night, often causing greater losses

fire causes of phase-shifting capacitor

1. The dielectric coefficient of insulating oil between components and shell in capacitor is low, the ignition point is not high, and combustion is easy to occur

2. the energy loss of the capacitor is mainly the dielectric loss between the plates and the heat loss of the conductive part, which will cause the capacitor to heat up. If the cooling conditions are not changed with the loss of energy, the temperature will inevitably rise, especially when the capacitor elements are arranged in layers, the heat dissipation problem should be considered to avoid the device damage, dielectric breakdown, explosion and fire caused by the increase of the thermal dissociation of the medium due to the high temperature

3. the disconnection and connection of capacitor devices involve the transition process during operation, and overvoltage and inrush current will occur. During disconnection, because the movement speed of the opening contact is not necessarily fast, it will cause the switch contact to reignite and cause overvoltage. Each reignition will increase the voltage on the capacitor by 2 times. When the capacitor is connected, it will cause great inrush current, especially when the capacitor is charged, which will bring more serious consequences. In short, in the process of capacitor disconnection and connection, due to the existence of overvoltage and inrush current, it will cause short circuit, device breakdown, capacitor explosion, and most capacitor fires occur at this time

4. the capacitor shall be equipped with automatic heat release device. When it discharges, the stored electric field energy will be transformed into the heat energy on the discharge resistance. Its heat is not consistent in each discharge circuit, but is proportional to the ratio of their resistance value to the total resistance of the whole discharge circuit. Although the discharge process is very fast, the heat released is still far from enough to make the fuse act. When a short circuit occurs in a capacitor, all shunt capacitors must discharge it. At this time, if the automatic discharge device is damaged, the heat in the capacitor will increase sharply, causing the oil tank to rupture, explosion and fire. When encountering combustibles, the fire will arc high: spread, causing great losses

preventive measures for fire of phase-shifting capacitor:

1. The fire resistance rating of the capacitor room equipped with combustible medium high-voltage capacitor should not be lower than grade II. The room should have good ventilation to ensure that the indoor temperature is lower than 45 ℃, and take measures to prevent rain, snow and small animals from crawling in

2. the arrangement of capacitor banks should not exceed three layers, the bottom of the lower layer should not be less than 0.3m from the ground, and the clear distance of the shell should not be less than 0.5m

3. before the capacitor is put into operation, it must be checked and hand over tested. It can be put into use only after passing the test

4. Train operators and establish inspection system. Capacitor operators must be trained and qualified to take up their posts with certificates, and the operation procedure at this time is to cut off and open the output signal of the power unit first. The daily patrol inspection, regular power outage inspection and special patrol inspection system should be established. The inspection record book should be filled in, and the problems should be handled in a detailed, timely and timely manner

5. As a fire supervisor, when carrying out fire inspection, we should focus on finding the following phenomena and faults and deal with them in time:

when we find the leakage of oil from the capacitor, the expansion of the shell, the sound inside the capacitor, the sparks outside, etc., we should immediately disconnect the capacitor from the line, and maintain or replace the capacitor in time

when the indoor temperature of the capacitor is found to be too high, ventilation and heat dissipation measures should be taken in time. When dust is found on the surface of capacitor shell, insulation, support, etc., regular cleaning shall be urged to prevent sparks and short circuits. If the discharge device is found damaged, it should be repaired in time. Check whether the oil circuit breaker and switch are complete and easy to use

in addition, attention should also be paid to the correct operation of capacitors and their electrical equipment. During power transmission, turn on the electrical switches of all outgoing lines first, and then the capacitor switches; In case of power failure, first open the switch of the capacitance Jinan gold assay paper packaging detection instrument, and then open the electrical switches of all outgoing lines. It is strictly forbidden to send power to charged capacitors