METREL VoltScanner MI 2130, Руководство пользователя

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MI 2130 VoltScanner Setting Up the VoltScanner
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Voltage Transient
A voltage transient is a short duration overvoltage which lasts a few milliseconds or
less. The VoltScanner records transients both on L-N and N-PE inputs, which are
above the set threshold and last at least 1us. It records magnitude and phase of a
transient. If there are more transients in one half cycle, the VoltScanner records
magnitude and phase of the highest transient and the number of transients that
occured.
Transients are usually caused by lightning, electrostatic discharges, load switching or
faulty wiring. Transients can erase or alter computer data and, in extreme cases, they
can even destroy electronic circuitry and damage the electrical equipment. Generally
speaking, transients can be classified into two categories:
•
An impulsive transient is a sudden, non-power frequency change in the steady state
condition of voltage, which is unidirectional in polarity (either positive or negative).
The most common cause of impulsive transients is lightning. They are generally not
conducted far from the source of where they enter the power system, although they
may, in some cases, be conducted for quite some distance along utility lines.
•
An oscillatory transient is a sudden, non-power frequency change in the steady state
condition of voltage which includes both positive and negative polarity values.
Impulsive Transient
Frequency Variations
Frequency Variations are defined as a deviation of the power system fundamental
frequency from its specified nominal value (e.g. 50 Hz or 60 Hz).
The power system frequency is directly related to the rotational speed of the generators
supplying the system. There are slight variations in frequency when the dynamic
balance between load and generator changes. The size of the frequency shift and its
duration depends on the load characteristics and the response of the generation control
system to load changes.
Frequency variations that go outside the accepted limits for normal steady state
operation of the power system can be caused by faults on the bulk power transmission
system, a large block of load being disconnected, or a large source of generation going
off- line.
The VoltScanner records frequency events whether the frequency goes above or