Oil-Immersed Transformer Iron Core Fault And Detection Method
The detection method for poor grounding of the iron core is usually carried out from two surfaces. In the chromatogram analysis, if the content of methane and acrylic acid in the gas is high, the content of carbon monoxide and carbon dioxide will not change much, if not normal, the overheating of iron oxide carbon will lead to the possibility of multi-point grounding. . Measure whether there is current in the ground wire. On the grounding wire of the iron core grounding pipe of the oil-immersed transformer, the current of the wire can be measured with a clip. When the iron core of the oil-immersed transformer is normally grounded, there is no current circuit. The current on the ground wire is small, at the milliamp level (usually under 0.3 A). When grounded at multiple points, the magnetic flux around the core is equivalent to the existence of short-circuit coils, and the current in the coils flows through the annular flow. Its value depends on the relative position of the fault point to the normal ground point, i.e. the magnetic flux contained in the shorted coil number. Generally, it can reach tens of amperes. By measuring the current of the ground wire, the multi-point grounding obstacle of the iron core can be correctly judged.
Temporary cancellation method when the oil-immersed transformer cannot be stopped: if there is a ground wire, if the fault current is large, the ground wire can be temporarily opened. However, in order to prevent the failure point from disappearing and the floating potential appearing, it is necessary to strengthen the monitoring. If the fault of multi-point grounding is unstable, the sliding resistance can be connected to the working grounding wire to limit the current to less than 1 A. The selection of the sliding resistance is to divide the current of the grounding wire by the measured voltage of the normal working grounding wire. Use T-line chromatographic analysis to monitor the amount of gas at the point of failure. If the correct fault point is found according to the measurement and cannot be dealt with, the normal operating iron core grounding plate can be moved to the same position as the fault point, which greatly reduces the cycle.
Once the oil-immersed transformer finds a multi-point grounding fault, the stopable oil-immersed transformer should be stopped immediately, and the multi-point grounding fault should be completely removed after removal. According to the type and cause of multi-point grounding, take corresponding maintenance measures to eliminate the fault of multi-point grounding. However, if the point of failure cannot be found, the ring core will also be cut off. In order to find the connection address accurately, there are the following methods on site. Open the connector between the DC method iron core and the pliers, inject 6 V DC voltage into the silicon steel plates on both sides of the York, and measure the voltage between the silicon steel plates with a DC voltmeter in turn. When the voltage is zero or the indication of the meter is opposite, it is regarded as a faulty connection place. For the low voltage of the AC oil-immersed transformer, when the coupled AC voltage is 220-380 V, the magnetic flux exists on the iron core. If there is a bad ground, use mA to measure the current (the connector between the ferrite core and the pliers should be open). When the million current is zero, thats the point of failure.
