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UPS’s primary role within a data center or ICT room is to provide instant battery backup if the mains power fails. Sometimes, this backup resource is designed to support the load for extended periods. More usually, though, its purpose is to buy time before the generator to start up and come online.
The UPS therefore must communicate some type of warning signal to trigger an action as soon as the mains fails; otherwise, if a blackout exceeds the battery autonomy time, a system crash is inevitable.
Communication between the UPS and the ICT system comes in different categories based on the need of the organization and how critical the system is.
However, there’s no point in investing in a communications capability beyond the realistic needs of an application; accordingly, this article looks at the various options available today.
At the simplest level, ‘True/Not True’ information can be obtained from volt-free contacts that can communicate UPS status and alarms to other equipment on the same site as the UPS. Windows, and other PC or network operating system support software that can detect these alarms and alert the technical staff in order to take action. It could also be configured to automatically react by initiating a generator startup or alternatively an orderly system shutdown. The signals from the UPS could include
- mains failure/mains present
- battery low/battery ok
- load on mains /load on the battery
A more sophisticated communications strategy can be implemented which allows more detailed information to be transmitted, including data generated by UPS self-diagnostic activities. This can be implemented using the RS-232 connection available on many UPSs. Examples of analog values that can be measured and transmitted include:
- The inverter output voltage, frequency, current, kVA and kW
- Bypass voltage, frequency, current, kVA and kW
- Battery voltage, charge/discharge current and remaining battery time
- Statistics regarding mains failures and UPS operation
This allows real-time monitoring of the UPS real-time as a remote computer can continuously poll it for updates and then log the operational status data while
critical alarms are communicated to the systems administrators as needed. The exact information profile obtained in this way from a UPS depends on the individual UPS supplier, and the software they provide to handle the serial data stream. The monitoring software is available for most operating systems, and its facilities may include:
- A graphical display of UPS status, voltage, current, load, battery voltage, and frequency and more
- Configurable responses to certain alarms, which can include broadcasts to users
Scheduled diagnostic checks and data logging
RS-485 or full-duplex RS-422 communications can be used for longer distances, and modern UPS equipment also provides a USB port. Modbus, an application-layer serial communications protocol that operates over either RS-485 or IP links, can also be used to communicate with up to 240 devices across a common network.
Network Based System
This is required for organisations with a large branch network spread ou in many cities eg a commercial bank These present monitoring, management and maintenance challenges that can only be addressed with a full IP-based Wide Area Network (WAN) solution. In some cases, of the sites within the network like ATM are unmanned, or without a network manager. Any problems they experience could cause a damage to system or lead to operational failure.
The solution is to equip devices like UPSs with Simple Network Management Protocol (SNMP) capabilities, as this allows monitoring and control of every device on a WAN from a central location. SNMP is a standard protocol and part of the Transmission Control Protocol/Internet Protocol (TCP/IP) suite which allows all network devices to transmit management variables across enterprise-wide networks. SNMP is vendor- and platform-independent, and establishes guidelines for how information is collected and managed. Network devices gather information into a management information base (MIB), from where it can be accessed by SNMP management software running within the user’s operating system.
An SNMP-enabled UPS is an intelligent device that can log events, continuously monitor power quality, report on battery status, load and temperature, and perform self-diagnostics – but this built-in intelligence creates other management opportunities as well. The UPS can handle incoming commands to control the individual devices it supplies; for example, to isolate sections of a system for security purposes, shut down some devices to save power, and manage redundancy.
Predictive maintenance also becomes possible. The UPS can log power disturbances, track battery usage, alert managers to low battery problems, and track power level history. Through SNMP, this information is available across the network for immediate analysis and to detect potential problems before they cause downtime or damage.
At Niteo Limited we design and implement an efficient communication technology that can also be expanded to encompass multiple UPSs for optimum efficiency in load management. Information can be collected from, say, several dozen UPSs into a central network console to allow an integrated, large-scale control strategy. This includes preventative and corrective maintenance by our team of well-trained engineers who can perform remote diagnostics, followed if necessary by a site visit to rectify the fault – all within any contractually agreed time frame.