# Power Quality Impact and Its Assessment: A Review and a Survey of Lithuanian Industrial Companies
## 4 Results
We suffer economic losses after each dangerous voltage sag.\" * \"When voltage variations occur, the frequency converters are disturbed, and usually are disconnected by the protection thereby protecting themself from breakdown and, as a result, disconnecting the converter-fed electric motors. In more serious situations, the frequency converters break down.\" 5. Comment about MV three-phase generator: * \"After voltage sags, generator protections disconnect the generator from the power grid. The process of electricity generation is halted. Electricity is not sold.\" Contrary to electric machines, most companies acknowledge that voltage sags are not dangerous to heating elements and temperature chambers. However, in the case of a longer supply interruption, it is likely that the temperature regime will no longer be suitable for the process, for example, in the food industry. The answers about heating elements are summed up in Table 15. The following comments were received: * \"[Voltage sags] have an impact on mineral powder production.\" * \"Voltage sags are not dangerous to heating elements.\" * \"Temperature chambers are not sensitive to voltage sags.\" * \"Heating elements are connected with semiconductor relays and thermoregulators. These devices are sensitive to voltage variations, which can interrupt their smooth operation and, in some cases, cause damage.\"* \"All systems operating in the company have programmable controllers. Short-term voltage sags can freeze the controller or delete its settings (and time is wasted to reset them). Our processes are slow and do not require synchronization, thus the losses are minimal.\"
* \"The company's heating elements are very sensitive to voltage sags.\"
* \"Heating elements are not sensitive to voltage sags; however, they are integral part of other equipment. Thus, the entire equipment stops after any dangerous PQ event.\"
* \"The factory is heated only with electricity. During 7 years of operation, three heater controllers failed due to voltage sags. Losses--about EUR 75. Perhaps this contributed to the breakdown of three air conditioners.\"  
The answers about controllers are summed up in Table 16: in this case, one exceptional response (to which the rules set in Section 3.2 do not apply) given in Table 17 was included due to solid argumentation. The following comments were received:  
* \"We have 13 controllers, the work of which is highly influenced by voltage sags.\"
* \"The company has 62 different controllers with UPSes.\"
* \"All production and storage equipment of the company is controlled by more than 300 controllers, and most of the 0.4 kV electric motors have frequency converters (more than 100 units in total).\"
* \"The company's controllers are very sensitive to voltage sags. After each dangerous voltage sag, petrol stations stop working. We lose customers and experience losses.\"
* \"Controllers of two devices (out of 17) are sensitive.\"
* \"Some important controllers are protected with UPS; however, many smaller devices are not protected, therefore they are more sensitive to voltage sags. After the event, our employees must restore the operation of controllers and configure their settings.\"
* \"Most of the company's automation equipment and controllers are sensitive to volt-age variations. Quite a few of them have double-conversion UPS, the rest is fed directly.\"
* \"Voltage sags have a very big influence on controllers.\"
* \"The controllers are fed by pulse power (output voltage is 24 VDC). The controller switches off completely after 5 s from the moment of the voltage loss, and starts without problems when the supply is restored. Obviously, the technological process is affected [by voltage sags].\"
* \"Controllers with pulse power supply are sensitive to voltage sags. If power source is toroidal, such controller has the immunity. We have both. We have approximately 110 machines and all of them have programmable logic controllers.\"
* \"Microcontrollers and electronic devices are very sensitive to voltage sags.