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Upon determining that voltage sags, especially during thunderstorms, had been the primary cause of these stoppages, it was found that these voltage sags led to current surges when normal voltage was restored. This current inrush exceeded the ratings of critical power electronics components like rectifier diodes, circuit traces, in the printing equipment. The resulting overloading compromised their integrity and could cause equipment failure.
In a collaborative effort with Omniverter, the bakery utilized power quality monitors to investigate the source of these disruptions. The facility, supplied by the local electrical utility at medium voltage 20kV and relying on several transformers to achieve an operating voltage of 480V, discovered that voltage sags during storms and adverse weather were the primary culprits. This issue was especially critical for a line producing several million cookies per week.
The company requested help from their electrical utility which installed power quality meters at the site. The utility determined that the site was experiencing multiple voltage sags, especially in stormy weather and that while some of these sags originated from local conditions such as tree branches contacting power lines the plant was also seeing the effect of voltage sags created on the high voltage transmission lines. The utility concluded that in some months there were over 20 voltage sags below 90% of nominal voltage and some of these were very deep.
The Dairy management believed that the problems were due to poor electrical power quality. They approached their electrical utility which installed power quality analyzers. They concluded that the Dairy was suffering not only from voltage sags but also from occasional complete loss of power for short periods. The dairy is fed at 480V but is located downstream from a utility 12.5kV medium voltage recloser so, whenever the recloser operated, the dairy experienced loss of power. Omniverter was invited to offer a solution. After analysis of the data and discussions with the utility it was found that any movement of the medium voltage recloser to a position downstream of the Dairy to reduce power loss was not economically feasible. The solution would need to correct both voltage sags and short term loss of power in an industrial environment with no clean room space available for a conventional UPS system. In most cases the loss of power lasted for only a few seconds
The Company installed power quality analyzers and worked with their local electrical utility to acquire data. They determined that almost all of the events were due to voltage sags and there was very little actual loss of power. Omniverter analyzed the data and learned from the customer that a solution should provide continuous voltage correction and voltage phase balance to keep the voltage in as tight a tolerance as possible to optimize their production runs.
The utility installed power quality monitoring equipment and determined that there were neighborhood power fluctuations and electrical flicker which they traced back to the quarry. When starting the rock crushers at the start of a work shift there would be a requirement for reactive power (kVAR) input that exceeded the capacity of the utility supply, resulting in a voltage sag on the network. This could also happen occasionally during the day if large rocks were being crushed or if both rock crushers came under peak load simultaneously. Wide variations in load resulted in the creation of electrical flicker
The data was shared with Omniverter and it was clear that almost all events recorded were due to voltage sags which occur most frequently during stormy weather. The hospital had started building a new dedicated cancer treatment center on a separate site and required protection against voltage sags for their new suite which included several LINAC’s.
The company had installed several power quality monitors throughout its facility, so it had several years of data on the electrical supply power quality. The plant is supplied at medium voltage 27.6kV to a transformer located inside the building which supplies an operational voltage of 600V to production areas. Omniverter was invited to help the company find a suitable solution to correct the voltage sags and improve production. Analysis of the data showed that over a 5 year period there had been only one power outage but many voltage sags. Omniverter was able to calculate the depth of voltage sags that cause a production stoppage.
Powered by a 35kV underground cable and stepped down to 480V for production, the facility's power quality meters, installed in collaboration with their utility, traced the operational disruptions to voltage sags. These sags, mostly single-phase events likely caused by lightning strikes, could lead to wire tension issues, damaging the wafers or breaking the wire.