The QJ series gas relay mainly operates by utilizing the characteristic of gas or oil flow generated by oil decomposition during internal faults of transformers. When the transformer is operating normally, the gas relay is filled with transformer oil inside. Once faults such as inter turn short circuits or overheating of the iron core occur inside the transformer, the insulation material will rupture under the action of an arc, producing a large amount of gas. These gases gradually accumulate in the gas collection chamber of the gas relay, and as the gas volume increases, the pressure forces the oil level to drop, driving the float to move.
When the gas reaches a certain volume, such as the alarm gas volume, the light gas action is triggered. Taking common models as an example, such as the QJ4G-25TH type, its float cup (float) descends with the oil level, and the magnet on the cup causes the dry spring contact to close, connecting the signal circuit and issuing an alarm signal to remind the operation and maintenance personnel that there may be a minor fault in the transformer. If the fault is severe, such as a serious turn to turn short circuit, a large amount of gas will be generated, forming oil surges. At this point, the heavy gas comes into play, and the oil flow impacts the baffle. The baffle rotates to a limited position, and the magnet on the baffle attracts another set of dry spring contacts, connecting the trip circuit and directly cutting off the transformer power supply to avoid further expansion of the fault and prevent the accident from causing greater impact on the power system.