# Power Quality Impact and Its Assessment: A Review and a Survey of Lithuanian Industrial Companies
## 4 Results
After each dangerous voltage sag, the company suffers a loss of EUR 1000-11,000.\" * \"Short-term voltage sags do not have a significant impact on the work.\" * \"We cannot say exactly because we do not have PQ analyzers and we do not have any experience in voltage sag analysis.\" * \"The motors are controlled with CNC machines, and therefore are very sensitive to voltage sags. Each time we experience losses.\" * \"The electric motors of individual technological equipment are sensitive to voltage sags.\" * \"[Voltage sags] are the most dangerous for refrigeration compressors. The protection turns them off.\" * \"Electric motors are very sensitive; the company suffers a loss of EUR 5000-20,000 after each voltage sag.\" * \"Voltage sags shorten the service life of pumps, sometimes affect the impellers\". * \"After each voltage sag (duration 200-5000 ms), the compressors disconnect and the technology stops.\" * \"Voltage sags can cause the malfunctioning of railroad switches--it is possible that the switches will not switch to the right position and, as a result, the train will be delayed.\" * \"The company's electric motors are very sensitive to voltage sags. After each dangerous voltage sag, the company suffers a loss of about EUR 15,000.\" * \"Electric motors and servomechanisms are very sensitive to voltage sags. After each dangerous voltage sag, the company can suffer a loss of up to EUR 28,000.\" * \"The ventilation systems and pumps cease operating, resulting in production stoppage. Losses--EUR 3000 per hour.\" 3. Comments about LV single-phase electric motors: * \"The effect [of voltage sags] was not noticed, because the motors are disconnected by the automation of control panels.\" * \"The effect of voltage sags\" was not noticed, because the motors are disconnected by the automation of control panels. * \"Voltage sags can cause the malfunctioning of railroad switches--it is possible that the switches will not switch to the right position and, as a result, the train will be delayed.\"
* \"We have a large number of units that use a variety of single-phase motors. Their reactions to voltage sags are different. Each voltage sag has an impact.\"
4. Comments about variable-frequency drives: * \"[Variable-frequency drives are] very sensitive [to voltage sags], because they hand or are irreparably damaged.\" * \"When voltage sag occurs, the variable-frequency drives, which tries to execute the com-mand of the controller regardless of the circumstances, stop at first. The voltage drops, the current increases until it reaches the threshold limits, and the unit fails with the overload error flag. Then, the controller stops the entire technological line.\" * \"The frequency converters are damaged if supply interruption is between 0.2 s and 2 s. If its duration is longer, the communication with controller is usually lost, which leads to the interruption of the technological process and product damage. The equipment can al-so be damaged: for example, if supply interruption occurs, ammonia [NH\({}_{3}\)] and carbonic acid [H\({}_{2}\)CO\({}_{3}\)] compressors working at 100% capacity damage (crush) their filters due to the pressure, which causes 1-2 h of outage.\" * \"Longer voltage variations are dangerous to the equipment which has frequency converters. These devices stop in the case of inappropriate voltage parameters, and then need to be restarted. But before that, when the process stops, it is necessary to remove the unprocessed (raw) material that is no longer suitable for the production.\" * \"Momentary voltage variations cause voltage transients that can damage the equipment.\" * \"We cannot accurately assess the danger, because the operation of frequency converters also depends on the shape of voltage sag [e.g., single-stage or multi-stage]. The company has many frequency converters, which are sensitive to voltage sags.