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| e-mail stedipower@tvss.net ::: Phone: 678.546.6780 |
| Impulse Transient | |
| A sudden and short-duration disturbance caused by a very rapid change in the steady-state condition of voltage, current, or both, that is unidirectional in polarity. | |
| Frequency range: >5 kHz (high frequency) | |
| Duration: 30-200 uSec | |
| Low-frequency transients: <500 Hz | |
| Duration: <30 cycles | |
| Causes: | •Capacitor switching |
| Impacts: | •Tripping of ASDs and other sensitive equipment |
| •Voltage magnification at customer capacitors | |
| Oscillatory Transient | |
| A sudden and short-duration disturbance caused by a very rapid change in the steady-state condition of voltage, current, or both, that is bi-directional in polarity. | |
| Medium-frequency transients (500 Hz-2 kHz) | |
| Duration: < 3 cycles) | |
| Causes: | •Traveling waves from lightning impulses |
| •Capacitor and circuit switching transients | |
| Impacts: | •Failure of customer equipment |
| High frequency Transients >2 kHz | |
| Duration: < 0.5 cycle | |
| Causes: | •Switching on secondary systems |
| •Lightning-induced ringing | |
| •Local ferroresonance | |
| Impacts: | •Radiated noise may disrupt sensitive electronic equipment |
| •High rate of rise oscillations may cause low-voltage power supplies to fail | |
| •Short-duration voltage variations | |
| Dips | |
| Decrease between 0.1 and 0.9 pu in rms voltage or current at the power frequency for duration from 0.5 cycles to 1 minute | |
| Causes: | •Local and remote faults |
| Impacts: | •Dropouts of sensitive customer equipment |
| Voltage Swells/Surges | |
| Increase to between 1.1 and 1.8 pu in the rms voltage or current at the power frequency for durations from 0.5 cycle to 1 min | |
| Causes: | •Single-line-to-ground faults |
| •Equipment overvoltage | |
| Impacts: | •Failure of MOVs forced into conduction |
| •Long-duration voltage variations | |
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| Overvoltage | |
| Increase in the rms ac voltage greater than 110% at the power fre quency for a duration longer than 1 min. | |
| Causes: | •Load switching off |
| •Capacitor switching on | |
| •System voltage regulation | |
| Impacts: | •Problems with equipment that require constant steady-state voltage |
| Under-Voltage | |
Decrease in the rms ac voltage to less than 90% at the power frequency for a duration longer than 1 minute | |
| Causes: | •Load switching on |
| •Capacitor switching off | |
| Impacts: | •Problems with equipment that require constant steady-state voltage, system voltage regulation |
| Waveform distortion / Harmonics | |
| Nonlinear loads, such as power electronic equipment, produce non-sinusoidal current waveforms when energized with a sinusoidal voltage. They inject currents at harmonic (integer multiple of the fundamental frequency) frequencies into the system. Harmonic currents, and the voltage distortion they create as they flow through the system impedance. | |
| Causes: | •Nonlinear loads |
| Impacts: | •Improper operation of sensitive equipment |
| •Reduction of equipment operating reliability and service life (0-100th harmonic) | |
| •Capacitor failures or fuse blowing | |
| •Telephone interference | |
| Notching | |
| Periodic voltage disturbance caused by the normal operation of power electronics devices when current is commutated from one phase to another | |
| Causes: | •Normal operation of electronic equipment |
| Impacts: | •Improper operation of equipment |
| •Equipment failure | |
| Noise | |
| Any unwanted electrical signals with broadband spectral content lower than 200 kHz superimposed upon the power system voltage or current in phase conductors, or found on neutral conductors or signal lines | |
| Causes: | •Improper grounding |
| •Normal operation of electronic equipment | |
| •Arcing devices | |
| •Switching power supplies | |
| Impacts: | •Interference with electronic devices such as microcomputer and programmable controllers |
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PHONE: (678) 546-6780 FAX: (678) 546-6782 | ||
Technical Support | Stedi-Power, Inc. | |
General Inquiries |
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Stedi-Power, Inc
5044 B U Bowman Drive #102
Buford, Georgia 30518
PHONE: (678) 546-6780
Last Updated: 07 Jun 2004
©1997-2004 Stedi-Power, Inc.
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All other rights reserved.
