In order to study the operating characteristics of current transformers and determine whether they will be saturated and affect maintenance operations when subjected to high currents outside their maintenance, some testing methods can be used.
The direct testing method is to apply current from the primary side and measure the secondary current to find the saturation point of the current transformer when it is loaded on the secondary side. However, for maintenance-level current transformers, their saturation point may exceed the rated current by 15 to 20 times.
As the current transformers get bigger, it may be difficult to perform the test on site. In addition, the saturation point of the current transformer can also be measured through the volt-ampere characteristic test.
The saturation of the current transformer is calculated based on the excessive magnetic flux density of its iron core.
The volt-ampere characteristic testing method is: disconnect the primary side, apply current from the secondary side, and measure the voltage drop on the secondary winding. Since the primary side of the current transformer is open, the primary current has no demagnetization effect, and the iron core is easily saturated under low current.
Current transformers measure small currents based on the excessive magnetic flux density of their iron cores. The current flows in from the secondary winding and is measured.
Due to the absence of demagnetization effect on the primary side of small current transformers during the measurement process, the iron core is easily saturated under relatively low current. Therefore, optical current characteristic experiments do not necessarily require very large current flows.
During the use of current transformers, it is important to prevent them from burning out. This is primarily achieved by installing isolation switches to prevent problems with support systems from causing power outages along the entire line, especially by ensuring that the isolation switches can jump reliably. Next, the current transformer is placed behind the isolation switch to ensure that the high-voltage transformer and surge arrester are properly removed if there are problems.
Secondly, it is necessary to improve the insulation test of the customer's current transformers and high-voltage surge arresters, detect the degree of embrittlement of the insulation layer of the voltage transformer and surge arrester as early as possible, immediately replace them, and prevent power outages caused by burned-out voltage transformers. Regular cleaning of the customer's equipment should also be carried out to reduce environmental pollution and prevent insulation degradation.
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