Data, data everywhere

Eaton Corporation
Wednesday, 05 December, 2001

In today's dynamic telecoms environment the equipment loads on a DC power system and battery may be regularly increased through its life.

Fortunately, modern DC power systems, with digital control and monitoring systems, give power systems engineers an in-built tool to monitor changes in demand.

Data logging provides the ability to collect system performance regularity for objective analysis.

The Intergy SM50 series supervisory module has a data log feature able to collect detailed performance data for later download. Downloading can be either through a data link to a remote PC or directly by serial link to a local PC.

However, once the data has been downloaded the problem then becomes how to analyse the information efficiently and provide meaningful results.

Invensys Energy Systems has experience of collecting and analysing data from Intergy DC power systems at 'live' telecommunication sites. From that experience three key points have been identified that allow power system engineers to rapidly identify the 'fitness' of a DC power system.

Rectifier capacity

Recording the power demand on the rectifier modules in a system and calculating it as a percentage of their maximum power output, is an effective way to monitor that a DC power system is not overloaded.

This is a particularly important measurement at sites where the load on the DC plant is continually increasing. A percentage figure has the advantage that it takes account of the total number of rectifier modules in the system. An Intergy SM50 supervisory module has the ability to internally calculate percentage output power and display it on the front panel LCD or remotely through the PowerManagerII monitoring software.

Alternatively the figure can be calculated from the voltage and current figures collected in the data log. An analysis of each power system will allow a maximum acceptable percentage output power to be set. This will take account of the required battery recharge current and level of rectifier redundancy.

Any power system that reaches its threshold can then be tagged for further investigation and a possible rectifier expansion.

Battery capacity

This is also an important measurement at sites where the equipment load is continually increasing.

By monitoring any increases in the equipment load current and comparing it to the known battery capacity, it is possible to foresee reductions in the backup time of the battery.

With Intergy DC power systems it is also possible to log battery temperature. This may be critical at a site with a seasonal temperature fluctuation and where a low battery temperature (and therefore reduced capacity) may coincide with an increased equipment load. If unforeseen, these two factors may combine and result in a severely reduced backup time.

Battery performance under load

Finally, the state of health of a battery can be readily assessed from how well it performs under load. When a battery is charged or discharged the Intergy SM50 supervisory module logs the actual performance data of the battery.

This information can be graphed to analyse the real backup time of the battery and any potential problems.

For example, any sudden changes to a battery's output voltage during a discharge may indicate one or more faulty cells.

Data logging is an important tool for power system engineers. In itself, the amount of data collected can be intimidating.

However, a clear strategy and efficient analysis can result in direct improvements to overall network reliability.

The Intergy SM50 series supervisory module has a data log feature enabling downloading of stored performance data either through a data link to a remote PC or directly by serial link to a local PC.

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