In the maintenance and overhaul of power system, the voltage test of cable is an important link to ensure its safe operation. In order to achieve this goal, the series resonance test device is widely used in the cable withstand voltage test. One of the core components of the device is the reactor, the selection of which directly affects the effect and safety of the test. It is of great significance to know the selection criteria and methods of reactors in depth for improving the effectiveness of cable voltage test.
The basic function of the reactor
The reactor mainly plays the role of limiting current, increasing voltage and adjusting resonant frequency in series resonance test device. Through series with cables and other electrical equipment, the reactor can form a resonant loop, so that the test voltage is significantly increased at a specific frequency, so that the voltage of the cable can be tested. The selection of reactor should not only consider its electrical parameters, but also pay attention to its mechanical characteristics and thermal stability.
Type of reactor
In the cable withstand voltage test, the commonly used reactors are mainly air reactors and oil immersed reactors. Air reactors are favored because of their simple structure and good heat dissipation performance, but in some high voltage tests, their volume is large and their portability is poor. The relatively small size of oil-immersed reactors makes them suitable for high-pressure, high-power applications, but their maintenance requirements are high and there may be a risk of leakage under extreme conditions. Therefore, when choosing a reactor, it is necessary to consider factors such as the test environment, equipment specifications and economy.
Parameter selection of reactor
The selection of reactor involves several parameters, including rated voltage, rated current, inductive value, resonant frequency, etc. First of all, the rated voltage should be greater than the rated voltage of the test cable to avoid overload during the test. Secondly, the rated current should be reasonably calculated according to the capacity of the cable and the test requirements to ensure that the reactor can withstand the current generated during the test. In addition, the selection of the inductive value should match the test frequency to achieve a better resonance effect.
When selecting the resonant frequency, a value near the resonant frequency of the cable should usually be selected to achieve a better resonant state. In practical applications, the tester needs to adjust the connection mode and parameter setting of the reactor to achieve a better match with the cable.
Selection precautions
In the reactor selection, the tester needs to fully consider the following aspects:
1. Environmental adaptability: The reactor must have good environmental adaptability and can work normally in a high temperature, wet or dusty environment.
2. Safety: The design and manufacture of reactors should meet the relevant safety standards to ensure that no accidents will occur during the test.
3. Maintenance convenience: Choosing a reactor that is easy to maintain and overhaul can reduce the maintenance cost in the later period and improve the use efficiency of the equipment.
Practical application case
An oil-immersed reactor with a fixed voltage of 35kV and a rated current of 200A was selected in a cable voltage test conducted by a power company. After more accurate calculation, the resonant frequency is finally determined to be 50Hz. During the test, the cable showed good insulation characteristics under the applied high voltage, without any abnormal phenomenon. This successful case shows that reasonable reactor selection is very important for the success of cable withstand voltage test.