20 April 2015
Overstrain, including pulse overstrain, any overvoltage of the relatively most admissible for this network is called.
These are such network hindrances as: an overstrain connected with a distortion of phases of rather big duration, and an overstrain, caused by lightning discharges lasting from tens to hundreds microseconds. Methods and means of fight depend on duration and amplitude of retension. In this regard pulse an overstrain it is possible to allocate in separate group.
The pulse overstrain is understood as short-term, extremely high voltage between phases or a phase and the earth with duration, as a rule, to 1 ms.
Lightning discharges – powerful pulse an overstrain, the lightnings resulting from a direct hit in power supply network, the lightning rod or an impulse from a lightning discharge at distance to 1,5 km leading to failure of electric equipment or failure in operation of the equipment. The direct hit is characterized by instant pulse currents to 100 kA lasting category up to 1 ms.
In the presence of system of the lightning rod the impulse of the category is distributed between the lightning rod, a food network, communication lines and household communications. Nature of distribution in many respects depends on a design of the building, laying of lines and communications.
Switchings in a power network cause a series of pulse retension of various power which is followed by radio-frequency hindrances of a wide range. The nature of emergence of hindrances is given on an example below.
Example of the nature of emergence of hindrances.
For example, at disconnection of the 1kva 220/220 V dividing transformer from a network all energy reserved by the transformer "jumps out" loading in the form of a high-voltage impulse up to 2 kV.
Capacities of transformers in a power network much more, are more powerful also emissions. Except that switching are followed by emergence of the arch which is a source of radio-frequency hindrances.
The electrostatic charge collecting during the work of processing equipment is interesting to that though has small energy, but is discharged in an unpredictable place.
The form and amplitude of a pulse overstrain depend not only on a hindrance source, but also on parameters of the network. There are no two identical cases of a pulse overstrain, but for production and test of devices of protection standardization of a number of characteristics of current, tension and a form of an overstrain for various cases of application is entered.
So for imitation of current of a lightning discharge the impulse of current of 10/350 microsec, and is applied to imitation of indirect influence of a lightning and various switching retension a current impulse with temporary characteristics of 8/20 microsec.
Thus, if to compare two devices to the maximum pulse current of the category of 20 kA at 10/350 microsec and 20 kA at an impulse of 8/20 microsec at the second, real "power" of the first approximately in 20 times more.
These are such network hindrances as: an overstrain connected with a distortion of phases of rather big duration, and an overstrain, caused by lightning discharges lasting from tens to hundreds microseconds. Methods and means of fight depend on duration and amplitude of retension. In this regard pulse an overstrain it is possible to allocate in separate group.
The pulse overstrain is understood as short-term, extremely high voltage between phases or a phase and the earth with duration, as a rule, to 1 ms.
Lightning discharges – powerful pulse an overstrain, the lightnings resulting from a direct hit in power supply network, the lightning rod or an impulse from a lightning discharge at distance to 1,5 km leading to failure of electric equipment or failure in operation of the equipment. The direct hit is characterized by instant pulse currents to 100 kA lasting category up to 1 ms.
In the presence of system of the lightning rod the impulse of the category is distributed between the lightning rod, a food network, communication lines and household communications. Nature of distribution in many respects depends on a design of the building, laying of lines and communications.
Switchings in a power network cause a series of pulse retension of various power which is followed by radio-frequency hindrances of a wide range. The nature of emergence of hindrances is given on an example below.
Example of the nature of emergence of hindrances.
For example, at disconnection of the 1kva 220/220 V dividing transformer from a network all energy reserved by the transformer "jumps out" loading in the form of a high-voltage impulse up to 2 kV.
Capacities of transformers in a power network much more, are more powerful also emissions. Except that switching are followed by emergence of the arch which is a source of radio-frequency hindrances.
The electrostatic charge collecting during the work of processing equipment is interesting to that though has small energy, but is discharged in an unpredictable place.
The form and amplitude of a pulse overstrain depend not only on a hindrance source, but also on parameters of the network. There are no two identical cases of a pulse overstrain, but for production and test of devices of protection standardization of a number of characteristics of current, tension and a form of an overstrain for various cases of application is entered.
So for imitation of current of a lightning discharge the impulse of current of 10/350 microsec, and is applied to imitation of indirect influence of a lightning and various switching retension a current impulse with temporary characteristics of 8/20 microsec.
Thus, if to compare two devices to the maximum pulse current of the category of 20 kA at 10/350 microsec and 20 kA at an impulse of 8/20 microsec at the second, real "power" of the first approximately in 20 times more.
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