According to statistics, the faults of the on-load pressure regulating switch mainly include two aspects: one is the failure of the driving mechanism of the pressure regulating switch, which mainly includes the linkage of the electric mechanism, water in the case, oil leakage of the gear box, and insufficient spring energy storage. The second is the failure of the switch body, mainly including oil leakage in the oil chamber, loose fasteners, stuck contact movement, and poor contact caused by contact wear. The following lists and analyzes the common fault types of on-load voltage regulator switches.
1. Failure of switch drive mechanism
① Motor failure. When the operating power supply is out of power or there is a problem with the motor circuit, it will cause the switch motor mechanism to fail, causing the lifting contact to fail to move.
②The elasticity of the spring energy storage mechanism becomes weaker. The long-term deformation operation of the spring, coupled with the thermal effect of the current, weakens the elasticity of the spring, causing the transmission mechanism to fail to drive.
2. The switch body is faulty.
①The contact hair is hot and worn. On-load voltage regulating switch brings load current to realize voltage regulation. In the process of voltage regulation, the gears are changed, causing problems such as mechanical wear and electrical corrosion of the contacts. The contact resistance of the contact increases and the heat generation increases, which accelerates the corrosion and mechanical deformation of the contact surface, resulting in damage to the switch.
②The switch refuses to move or the switch is not in place. The switch is not in place due to insufficient power or obstruction, and staying in the middle position for a long time can cause the transition resistance to continue to heat up, cause the transformer to trip, and cause the power supply to be interrupted.
③Oil leakage in the oil chamber. The oil compartment of the on-load tap-changer is an independent oil tank. During operation, the oil in the oil chamber of the on-load tap-changer is not allowed to enter the transformer body. An arc is generated when the switch is operating, which makes the oil in the oil chamber worse, and this oil cannot enter the transformer body.
④The oil quality has deteriorated. The arc generated during the operation of the on-load voltage regulating switch causes the deterioration of the oil quality, and the insulation level of the switch drops. Transformer oil has the functions of insulation, arc extinguishing, cooling, lubrication and corrosion prevention. The deterioration of oil quality will produce free carbon, hydrogen, acetylene and other gases and grease. Most of the gas is generally discharged from the insulating oil, but some of the free carbon particles and grease will be mixed in the insulating oil, and the other part will accumulate on the surface of the insulating parts of the switch, which reduces the insulation level of the switch. The voltage regulating switch of the transformer is the only rotatable part of the transformer. It is easy to cause the machine to heat up and cause failures due to poor contact. For this type of switch failure that is easy to occur, we must be prepared to deal with this type of failure. To check and judge the following aspects:
(1) Whether there are burn marks (singeing) and poor contact on the fixed and movable contact surface, and whether there is sludge deposit on the contact surface.
(2) Whether the transmission mechanism of the voltage regulating switch is flexible; whether the transmission mechanism is too loose and the pointer tip on the cover is indicated on the position mark, and the contacts are not closed at this time; whether the three-phase contacts of the switch are simultaneously closed Check whether the tightness of the spring is the same.
(3) Whether the seam between the operating lever of the switch and the box cover is tightly connected, and whether the liner is complete; whether there is water stains under the hole of the box cover aligned with the operating lever.
(4) If a terminal plate type tap is used, check the tightness of the terminal bolt pile heads, whether there is sludge accumulation between the wiring pile heads, and ensure that the pile heads are clean and intact, otherwise it is easy to short-circuit or flash. Network traces.
(5) When inspecting the on-load switch of the transformer, the core part of the switch should be taken out and turned back and forth to observe whether its contact limit action is smooth and continuous. At the same time, check its transition resistance to determine whether its connection is stable and reliable.