Costing the electrical energy losses in industrial installations is a smart idea. Three reasons:

• one--- It provides a cost reference for future improvements AND permits payback calculations on new investment;

• two--- you are able to identify high consumption loads and therefore look at reducing their energy consumption; and

• three--- by reducing energy loss your business is becoming greener.

In manufacturing, attention is focused on production shrinkage, as rejection numbers come straight off the gross margin. Depending on business costing policies, energy consumption may be considered as fixed, or fixed PLUS variable. The latter is of course only possible if there is in-plant metering installed. More about this later.
 
This article focuses in particular on transformers, switchboards, busbars and cabling, as well as motor-driven production equipment. No electrical engineering expertise is needed to make sense of recommendations—although it may well be smart to involve a consulting engineer.
 
Motors

Motor efficiency is very important! Rather than replacing a motor that has blown up, or worn out with the same rating, or looking for a cheaper alternative, modern, high efficiency motors can have pay-back periods as short as 7 months. The savings occur in reduced electricity consumption as motors, over their practical life usually consume far more dollars in energy than their acquisition cost. For detailed analyses your technical personnel should visit www.copper.org/applications/electrical/energy/sys_motor.html
The website is that of the national Copper Development Association, and will also guide the reader to the energy savings to be achieved in wiring AND transformers.

Because electrical installations are usually not reviewed unless there is a major breakdown, there are many instances where excess energy usage is undetected. There are great advantages in monitoring, on a continuous basis, the energy consumption (as well as other electrical parameters) of important parts of the production plant in order to allocate direct costs. Individual metering can indicate incipient problems, thus avoiding sudden interruptions to the production line.

DIN-rail mounted meters
DIN-rail mounting, Janitza Power Quality Analyser (model UMG 604) performs comprehensive power and power quality analyses, and can communicate, utilizing a large number of protocols, with SCADAs, PLCs, ProfiBus, and Modbus systems as well as building management systems such as BACnet and providing demand control. The Janitza UMG 604 Power Quality Analyser is provided with digital inputs and outputs as well a temperature sensor. RS 232 and RS 485 ports are provided, the latter supporting Modbus TCP/IP, Profibus DP40 and BACnet. In addition Ethernet 10/100 Base TX, FTP/TFTP are supported.

Switchboards, busbars and wiring
 
The more physically extensive the production plant is the more severe electrical energy losses become. The use of power electronics (induction heaters, electroplating, welding robots, palletizing and conveyor lines, etc) entails disproportionate energy losses in the factory electrical distribution cabling. This is caused by ‘harmonics’, which can cause additional current load between 40 and 100 % (technical information will be found at www.copper.org/applications/electrical/pq/issues.html and useful basic information at
www.rose-hulman.edu/class/ee/HTML/ECE471/PDFs/Lect15.pdf ).

Reduction of harmonics can be achieved through the use of filters. By grouping harmonics-causing equipment in a circuit with a harmonics filter in its input, a highly cost-effective energy conservation measure is made. In larger factories with a substation transformer, the pay-off is in more reliable and cooler transformer operation—and the spare capacity for factory expansion made available by ‘unloading’ the harmonics components before they affect the transformer.

Power Factor
The first thing here to consider is your electricity bill as to tariffs applied. In addition to kilowatt-hours, you may also be charged a maximum demand in kilovolt-amps (kVA). So far energy loss (in kilowatt-hours) has been the main subject. Many industrial installations have a large kVA demand compared to the useful power required (kilowatts) and pay more as a result. Power factor connect the two and is the ratio of kilowatts to kilovolt-amps. Active power factor correction, which reduces the kVA, can also be a part of harmonics filtering mentioned above. For kVA demand installations there is, as a rule, a very short payback period for power factor correction equipment through the reduction in demand tariff charges.

Active filters
ECOSine Active filters from Schaffner are suited to harmonic distortion mitigation as well as power factor correction for three phase circuits (three and four wire). Utilising Fast Fourier Transform (FFT) analysis to the 50th order, and performing the operation and consequent corrective current injection within 300 microseconds, the Schaffner ECOSine active filters provide a tailored solution to harmonics compensation. The response time is extremely fast so that the ECOSine filters combine the advantages attaching to FFT methodology with the response speed associated with so-called broadband active filters. The disadavantage of the latter is that they are unable to provide harmonic detail, merely correcting as far as possible overall current distortion. ECOSine Active filters are provided with Ethernet, RS485 and Modbus interfaces.
 

Finger on the pulse
 
Flying blind takes no skill but is hazardous. This article is an invitation to put your finger on the pulse. To test the electrical health of your plant, an analysis must be made using instrumentation such as power line analyzer. Such equipment can be rented, purchased or a suitable consultant can be engaged. There is considerable value, though, in building up your own capability because it allows regular review and therefore timely intervention.
 
Cost accounting for production processes is as good as the input data. Allocation of electrical energy costs can be critical in the P&L. Individual machine energy usage provides transparency as well the onset of problems through increased consumption. In this time of focus on energy conservation and reduction of greenhouse gas emission, knowing what is going on electricity consumption-wise in your factory is highly desirable.

Analyzer with harmonics analysis capability
The Voltech PM6000 is a fully floating wattmeter with high accuracy, bandwidth and rejection of common mode signals (CMRR). Up to 6 channels may be fitted into a PM6000 chassis, which has an embedded PC running the Linux operating system for trouble-free operation. The VGA display provides numeric and graphic measurements and shows the intuitive measurement menu. Connectivity includes RS232, printer and Ethernet. The display may be split to show numeric and graphical information at various zoom levels. Colour is used to identify measurements form one particular phase or group of phases. Communications options include RS232, IEEE488 and printer.


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