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Relation between Production and Energy Consumption

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Every manufacturing facility has different stages between raw material and finished commercial product. These different stages have individual motor circuit control (MCC) units, supplied from the ACB in primary control panel. Energy consumed by each area of a manufacturing plant can thus be calculated through regular monitoring. With production data, the energy consumed at any stage during the process can be normalized on units of production at the same stage. Performing this exercise continuously with a fixed time frequency will give a relation between units of production and energy consumed. Such production and energy correlation can be used by the top management to do bottom line analysis on how to improve the overall productivity while keeping the energy cost low.

Taking the time frequency of 1 hour, energy consumed in 1 hour window and number of units produced during the same period can be accounted. This will give 24 windows for one day but we also have to take plant shut hours into consideration as during these times, it can result in erroneous readings. Analysis of energy/unit for these 24 windows will give us the time of day during which more energy is being consumed. Looking deeper into such hours and capturing the root cause will lead to trapping energy wastages and will improve plant efficiency.

Doing such an analysis on regular basis, a baseline can be drawn for the whole manufacturing cycle. After attending the initial variation in energy consumed per unit at different time windows and achieving the best possible number for each time, the mean and standard deviation for each window can be taken as its baseline. Using this baseline, any deviation from it can be recorded to take counter measures.

At Zenatix, we integrate the energy meters of the facility with our software system which can record high resolution power data. Energy consumed within a 1 hour window can then be calculated on an on-going basis. Additionally, Zenatix platform can take the production data, which can either be provided in the form of excel file records uploaded through web interface or directly collected by interfacing with the machines that are capable of communicating with standard open protocols. Correspondingly, energy per unit can be calculated for 24 windows of the day.

Sample Plot-

Based on the analysis mentioned, plot of the energy consumed for producing one unit is plotted on hourly basis for 2 days. This analysis is done for one of the Zenatix’s client for the whole month. 24 such readings for all the days of a month will give a baseline. Considering loads other than only of machine which can be varying on hourly basis, baseline for each hour should be set separately. Taking average of 30 such readings for every hour in one month, the result can be used as the baseline for that hour for future considerations.

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As is evident from the plot, energy per unit of consumption is not consistent across the day as well as in comparison with the baseline. This requires deeper analysis by the customer which is currently ongoing. Without this information the customer was just unaware if any such discrepancy exists and thus never sought out to find answers to why is this happening.

Transformer Efficiency- Effect of Loading

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Distribution transformer is a part of every electrical power network at user end. If a facility is being supplied on HT from the utility, transformer and its losses comes under user’s responsibility. Like any other equipment its efficiency is calculated as the ratio of output power and input power. As transformer operates on the magnetizing phenomenon and it has no rotating parts, its efficiency is very high. It usually stays above 95% but as the power flow across a transformer is very high even small changes in terms of efficiency percentage gives significant energy savings.

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K-Factor for Transformer

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Kfactor for an electrical network primarily relates to non-linear loads and isdefined as a number representing the effect of harmonics on heating oftransformer. For calculating the K-factor all the harmonics up to a predefinedlimit are considered.

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Current and Voltage Unbalance- causes and counter measures

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Any deviation in voltage and current waveform from perfect sinusoidal, in terms of magnitude or phase shift is termed as unbalance. In ideal conditions i.e. with only linear loads connected to the system, the phases of power supply are 120 degree apart in terms of phase angle and magnitude of their peaks should be same. On distribution level, the load imperfections cause current unbalance which travel to transformer and cause unbalance in the three phase voltage. Even minor unbalance in the voltage at transformer level disturbs the current waveform significantly on all the loads connected to it. Not only in the distribution side but through the transformer, voltage unbalances disturbs the high voltage power system as well.

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Tackling Electricity Theft in India

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Indian government has announced an ambitious plan of setting up hundreds of smart cities across the country. However, no city can be called a smart city unless government can provide uninterrupted power. One of the major reasons behind long power cuts and huge losses for electricity distribution companies is electricity theft. India is one of the worst affected countries and controlling theft is imperative to provide uninterrupted power to the entire country.

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Tracking your Energy Management KPI

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I recently met an old friend who is currently managing operations at one of the hospitals of a large healthcare company. One of his KPIs is to reduce his energy bill on a month-on-month basis. He told me that he knows how to do this, but he does not know how to keep a track without spending too much time.

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Energy Data and Production Schedule

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The smart meters are providing energy data that is being used not only to monitor and analyse the energy consumption, but also to draw insights about other business areas. For example, an MD of a large manufacturing unit in India is using high resolution energy data (provided by Zenatix Solutions) to monitor the production schedules at his plant.

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Why Energy Intelligence Software

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The cost of electricity has been increasing rapidly – both because of increased prices and increased demand. Since electricity spend is one of the major operating costs for both commercial and industrial consumers, reducing and keeping a tight control on electricity costs is increasingly becoming a key performance indicator.

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Demystifying Power Factor Compensation

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What is power factor?

Power Factor (P.F.) can be viewed as the percentage of total apparent power that is converted into real or useful power. Mathematically, we can say that the active power (P)

can be represented as: Power_Factor

It is also seen as the displacement between the voltage and the current waveforms as shown below:

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Following relationships and terms are often used when dealing with power factor:

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where S = apparent power, P = active (real) power, Q = reactive power and Φ is the power factor angle.

While the above is typically called as displacement power factor (cosine of angle between the fundamental voltage and current waveforms), presence of harmonics results in waveform distortions and hence result in true power factor being different from displacement power factor. Utilities usually calculate true power factor (on which penalties are levied) as:

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Appliances usually have motors that result in lagging power factor (current lags the voltage thus resulting in positive Φ). To compensate for this lagging power factor, capacitor banks are put in place that provide leading power factor (current leads the voltage thus resulting in negative Φ).

Power factor compensation: Savings from reduced KVAh consumption

Let us understand power factor compensation by working out an example. Assume that you have a 2 MVA transformer that is loaded on average to 1.5 MVA. Consider your power factor to be 0.85 (this is typically lagging power factor). Let us first calculate the leading KVAR (required from capacitor bank) to correct the power factor to 0.99.

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So the capacitor bank should switch on capacitors worth 620 KVAR to compensate the power factor and bring it to 0.99. Following figure illustrates the different power units pictorially.

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With this improved power factor, the new apparent power S2 will be tumblr_inline_n6yx33LTyX1shjvod

In India since the commercial consumers are charged at KVAh and now KWh consumption, total savings you will get due to reduced KVA consumption = (1.5 – 1.29) X 1000 X 24 = 5040 KWhr/day

Assuming the commercial unit price of Rs 8, total amount saved due to reduced KVA consumption = 5040 X 8 X 365 = Rs 1.47 crores

Additional reduction due to reduced transformer losses:

Now if the transformer has rated conductor loss of 1% of transformer rating, total energy saved assuming that 1.5 MVA is the operating load can be calculated as follows.

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Total energy saved with reduction in transformer losses = 0.41/100 X 2000 X 24 = 196.8 KWhr/day

Assuming a unit price of Rs 8, the total amount saved = 196.8 X 8 X 365 = Rs 5.75 Lakhs.

While the primary saving of Rs 1.47 crores (as calculated above) is what people often quote and calculate, the savings due to reduced percentage loss in transformer is often neglected.

Other advantages of power factor correction:

Besides getting financial benefits, correcting the power factor has several other benefits, including increased equipment life and reduced heating for the equipment. Additionally, the freed up power (1500 – 1290 = 210 KVA) is now available for supply to other consumers.

Selection of capacitor banks:

Large power factor correction capacitors can result in flow of capacitive current eventually resulting in increased voltage. Therefore, careful switching of capacitors is important to not just maintain the right power factor but also for avoiding large voltage fluctuations. Especially, if the demand is heavily varying throughout the day, a fixed set of capacitors always turned on can be damaging. In such cases, a switched capacitor bank, which contains a power factor controller that senses the load and regulates the power factor by switching blocks of capacitors in and out, is worth the investment.

Harmonics and Capacitor Banks:

Capacitor banks are designed to operate at a maximum voltage of 110% of their rated voltage and 135% of their rated KVARs. Large voltage and current harmonics result in ratings getting exceeded and hence significant loss. Reactance of capacitors is inversely proportional to its frequency so high frequency harmonics easily find a low reactance path into the capacitor banks causing overload and subsequent failures. A more serious condition with potential for much larger damage is harmonic resonance which happens when the inductive and the capacitive reactance become equal on one of the harmonic frequencies.

Ref: Power Quality, C Sankaran