Preface The design considerations for large-scale three-phase UPS monitoring systems differ from those for typical small single-phase UPS systems. This is because three-phase UPS systems power a wide range of devices, including not only computer workstations but also network equipment, manufacturing equipment, medical equipment, precision instruments, etc. Furthermore, the three-phase UPS units are often scattered throughout the building, some distance from the monitoring room. Based on actual design examples, the following outlines the key design considerations. Simultaneous Connection with Multiple UPS Units: Due to the wide distribution of the three-phase UPS units, to avoid managers wasting time traveling between multiple UPS units, the system must have centralized monitoring capabilities. All UPS information should be centralized in one system, sharing a consistent alarm interface so that managers can manage all UPS units through a single system. When any power event occurs, the system should proactively notify relevant personnel via network broadcast, pagers, email, and voice alarms. This not only eliminates the need for frequent inspections but also ensures immediate notification from the monitoring system after a power event, effectively reducing the workload of management personnel. The primary function of a UPS (Uninterruptible Power Supply ) is to provide a clean and reliable power supply to the load immediately when the mains power is interrupted. To ensure the UPS functions properly during power outages, the battery must be in good condition so that the UPS can smoothly switch to battery power when the mains power is interrupted. Therefore, the system must be able to perform battery tests at user-defined times (usually during off-peak hours, mostly at night or early morning) to ensure the battery is available when needed. If the battery test fails, the monitoring system should notify management to check or replace the battery. Historical Data Storage and Printing Based on experience, most companies retain historical data files and event logs; some even back up the entire year's data to CDs for analysis by the monitoring system when needed. Therefore, the system must not only provide real-time information but also have the ability to read and analyze backup data, helping management quickly obtain the information they need. Furthermore, generating routine reports from the stored data can save considerable time. Remote Monitoring When the monitoring system notifies the manager of an abnormal power event, the manager may not be at the monitoring center. In this case, a channel is needed to allow them to remotely connect to the three-phase UPS monitoring system to obtain more complete information and take appropriate action. For remote areas without network access, we use a point-to-point modem for remote monitoring. If the system already has a network connection, we use a TCP/IP network for connection. We also provide HTTP access, allowing managers to connect to the monitoring system using only a web browser, obtaining the most complete power information anytime, anywhere. Protecting Operating Systems in Power Supply Units Although we focus on monitoring the three-phase UPS, the main unit and workstations are still important loads on the three-phase UPS. Therefore, protecting various operating systems and ensuring their safe shutdown during power outages is also a key design consideration. For this, we have developed a small program for each operating system. This program obtains the UPS status from the three-phase monitoring program via the network. When it detects a mains power outage or a low battery voltage, it issues warning signals according to the user's previous settings. When the shutdown time is reached, it safely shuts down the operating system. This feature can alleviate the workload of IT administrators, eliminating the need to rush back to the server room to shut down the mainframes during power outages. Communication Cabling Traditionally, cabling involved connecting each UPS unit in series using RS485 or RS422. However, this method not only consumes a lot of cabling over long distances but also makes communication susceptible to interference. Nowadays, most factory areas have extensive network cabling. Utilizing existing network cables to connect the UPS to the monitoring system nearby not only saves on cabling costs but also improves communication quality.