Introduction of short-circuit impulse current;
Short-circuit impulse current refers to the relationship between maximum instantaneous current and time when short-circuit fault occurs in power system. Immediately after short circuit, it will cause serious impact and damage to the power system.
Size of short-circuit impulse current:
The magnitude of short-circuit impulse current depends on the impedance, short-circuit type and short-circuit location of power system. When a short circuit occurs, the current will increase rapidly, reach the peak, and then gradually decay. The maximum value of short-circuit impulse current usually appears in the first period of short circuit, and its magnitude is related to short-circuit impedance.
In order to limit the magnitude of short-circuit impulse current, power systems usually take corresponding protective measures, such as installing circuit breakers, fuses and other protective equipment. At the same time, in the design and operation of power system, the influence of short-circuit impulse current should also be considered to ensure the safe and stable operation of power system.
For example, assume that the impedance of the power system is 0.5 ohms and a single-phase short circuit fault occurs. Then, the maximum value of short-circuit impulse current may reach 200 amps. If the power system impedance is large or the short circuit types are different, the maximum value of short circuit impulse current will be different.
Measurement method of short-circuit impulse current;
1, select the appropriate measuring instrument:
Measuring short-circuit impulse current requires special current measuring instruments, such as electromagnetic current transformer or optical current transformer. These instruments can withstand the instantaneous peak value of short-circuit impulse current, and can accurately measure the magnitude and changing trend of current.
2, determine the measurement position:
To measure short-circuit impulse current, it is necessary to set measuring points at appropriate positions in the power system. Usually, the measuring points should be set at the location where short circuit occurs and the key nodes of the power system, such as transformers, circuit breakers, buses, etc.
3, adjust the measuring instrument:
According to the types and specifications of measuring instruments, corresponding adjustment and calibration are needed. This includes setting measurement range, adjusting sensitivity, calibrating time constant, etc.
4, record the impact current data:
When a short circuit occurs, the impulse current will change rapidly. Therefore, it is necessary to quickly record the data of impulse current and record the parameters such as the maximum value, minimum value and average value of current.