Ken West of Fluke explains the benefits of using thermal imagers and power loggers

Regular use of portable and handheld test tools can prove very beneficial in the efficient and safe use of a facility’s electrical power and for troubleshooting problems. For example, a power logger can be used in electrical load studies to determine if an existing power distribution system can cope with new loads, to verify cable and system capacity, to balance load distribution over three phases, to keep track of power factor, and to quantify energy consumption before and after improvements to justify energy saving devices. Thermographic surveys with one of the latest low cost, handheld thermal imagers can also provide a lot of information about electrical systems, as well as a building’s structural elements, plumbing installations and HVAC.

Electrical load studies

When an installation requires the addition of new loads to an existing service or set of feeders, the first thing that must be determined is whether the existing system will support the new loads. To answer this question begs another question: What is the highest load the system carries now? This is of course essential information prior to additional equipment being installed, and it is also important to have a comprehensive understanding of the existing loading in order to evaluate the new system, once installed.

To determine the capacity of the existing equipment, the incoming conductor size, the ratings of the equipment and space for new circuits must all be factored in. The demand over a 30-day period should be measured along with the maximum demand in that period to give a total picture of the loading (this may vary dependent on application).

Avoiding financial penalties

Power factor is one important measurement collected in a load study. Electrical utilities often impose fines if the power factor drops below a contractually agreed value. The addition of new equipment may cause the power factor to drop. A load study taken before and after the installation will help pin-point this equipment as the source of the power factor change and enable appropriate power factor correction to be made, thus avoiding financial penalties. A load study is therefore also a powerful aid for ensuring that an energy consumer is being charged for what he actually uses.

Recording electrical power

A portable Power Logger, with flexible current probes for connecting around multiple conductors or bus bars, is an excellent tool for performing load studies, especially if it has a PC interface and software for downloading and interpreting measurements. It should be able to measure voltage and current on all three phases plus neutral, and record multiple parameters that can help determine system load, including voltage, current, frequency, real power (kW), apparent power (kVA), reactive power (kVAR), power factor, and energy (kWh).

Performing a load study takes just five steps

1. First, the power logger should be hooked up to the feeders or service. For a 3-phase system there will be eight connections: three phase voltages, neutral voltage, three phase currents and neutral.
2. Then the power system parameters and network topology should be set on the logger to match the system being recorded. The nominal voltage (mains voltage) and line frequency should be verified as correct.
3. Next, the recording times should be set, for example a 15-minute averaging interval and a 30-day recording duration.
4. Then the recording can be started, typically with 15 minute intervals, measuring:
   Power (in Watts for each phase and total)
   Reactive power (in VAR for each phase and total)
   Apparent power (in VA for each phase and total)
   Power factor (for each phase and average)
   Average energy (in kWh)
   Reactive energy (in kVARh).
5. Then after say 30 days, it can be disconnected from the source. The recorded data can then be downloaded to a PC, typically to create a graph of this data and thus making it possible to see the maximum current or power on each phase, to compare the three phases and to report the largest number. With the best equipment there will be a software report generator that will reproduce graphs of current and real power, as well as maximum average current on a bar chart.

Of course this work should only be undertaken by qualified personnel who will know and understand all the necessary safety aspects. Also the choice of power logger and ancillary equipment such as Clamp Meters should be carefully made to ensure they comply with the necessary over-voltage category requirements for the situations in which they are handled.

Thermography surveys

Problems that are otherwise invisible to the naked eye are suddenly clear when looked at through the infrared lens of a thermal imager. Over-heating electrical circuits, missing/damaged thermal insulation, evaluation of building materials, air leakage, moisture accumulation, blockages in pipes and structural features behind walls can all be detected with handheld thermal imaging cameras. By scanning surfaces, temperature variations can be quickly located: these are often indications of underlying problems, and they can be documented with detailed images in reports when using the best troubleshooting equipment.

Pinpointing potential sources of problems also saves valuable inspection time and leads to repairs of only what needs to be fixed. Repeated temperature measurements of the same targets can determine whether repairs were successful and will help anticipate future repairs.

Thermal imaging cameras immediately indicate the hot and cold spots in the form of thermal images from a safe distance. Traditionally, the high price tag of thermal imagers has been prohibitive, leading many facilities to outsource thermography inspections only once a year. However, new lower-cost high-performance cameras make it possible to bring thermal imaging in-house. Thermal surveys can identify and establish the extent of ther-mal anomalies within new or existing buildings.


For further information:

Ken West, UK Regional Marketing Manager - Industrial Tools
Fluke (U.K.) Ltd., 52 Hurricane Way, Norwich, Norfolk NR6 6JB

Tel: 0207 942 0700. Fax: 01603 256 606

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