Everything you need to know about generators

One has to decide what your priorities or needs are before any decisions can be made as to what to purchase.When considering the above, keep the following in mind:Appliances which contain elements (eg: geysers, kettles and heaters) and the wattage on the item is usually the correct value to use when adding up what wattage is needed from the generator.Add the watts on appliances you wish to run. For example, if the total is 5000 watts, this equals 5kva. Times this by 1.2, which equals 6.5kva, (the size of the generator you will need). Very simply 5500 watts is similar to 5.5kva at sea level.Another important point to remember is that on the Highveld, engines produce 20% less power than they do at sea level, due to the drop in atmospheric pressure with increased altitude
Installation advice:Automatic mains failure (AMF) with UPS: has no delay before the power is restored. It switch’s off your normal power supply and your generator on, without you leaving the comfort of your chair, while watching your favorite television programme.Manual mains failure: will switch off your power supply and requires that you manually start your generator up.Manual change over panel: requires that you switch off your normal supply and start the generator manually.Direct method: This is the simplest method. The appliance is plugged into the generator directly via an extension cord. In this case, the only outlay is the cost of the generator.Use a local electrical contractor to do your installation, remember that if the contractor installs the generator wrongly, the generator can burn out and no company will warrantee the product.Petrol generators vs. Diesel generators:Petrol pro’s:Capital outlay is at least half of the equivalent size.Require slightly less maintenance.More powerful than same sized diesel engines but need to run at higher revs to produce that powerPetrol cons:Highly flammableFuel consumption is high Diesel pro’s:Normally require slightly more maintenance.If the set is used for 24 hours the engine will last a great deal longer than petrolDiesel is more fuel efficient Operating costs are less in the long runDiesel cons:Capital outlay is at least double or more than that of a petrol set.Tips and Hints:Never refuel a petrol generator while the engine is running. A spark from the sparkplug can ignite the fuel and start a fire.Always make sure that the appliances or power tools are switched off before starting up the generator.Do not use an extension which is longer than 15 meters without increasing the diameter of the cable.Always refuel before the tank is empty.Shock and Electrocution Never attach a generator directly to the electrical system of structure (home, office, trailer, etc.) unless a qualified electrician has properly installed the generator with a transfer switch. Always plug electrical appliances directly into the generator using the manufacturer's supplied cords or extension cords that are grounded (3-pronged). Inspect the cord to make sure they are fully intact and not damaged. Never use frayed or damaged extension cords. Keep a generator dry; do not use it in the rain or in wet conditions. If needed, protect a generator with a canopy.Carbon Monoxide PoisoningNever use a generator indoors or in enclosed spaces such as garages, crawl spaces, and basements. Make sure a generator has three to four feet of clear space on all sides and above it to ensure adequate ventilation. Be cautious when using a generator outdoors to ensure it is not placed near doors, windows, and vents could allow carbon monoxide to enter and build up in occupied spaces. If you or others show symptoms of carbon monoxide poisoning (eg: dizziness, headaches, nausea, tiredness) get to fresh air immediately and seek medical attention. Do no re-enter the area until it is determined to be safe by trained and properly equipped personnelFire Hazards Generators become hot while running and remain hot for long periods after they are stopped. Generator fuels (gasoline, kerosene, etc.) can ignite when spilled on hot engine parts. Before refueling, shut down the generator and allow it to cool. Don't overload the generator.Do not operate more appliances and equipment than the output rating of the generator. Overloading your generator can seriously damage your valuable appliances andelectronics. Prioritize your needs.Portable generators:Portable generators can cause electrocution if they are left in the rain or sitting in water. Keep the generator under a canopy where it is protected, but not totally enclosed. It must still have adequate ventilation. Never touch the generator when you are standing in water or your hands are wet. Never run extension cords through water of any kind.DEVICE - TYPICAL WATTAGELight bulb - 60 wattsElectric oven - 3.410 wattsDeep Freezer - 500 wattsDishwasher - 1.500 wattsWashing machine - 1.150 wattsFridge - 1.200 wattsDvd / Cd player - 100 wattsTelevision - 300 wattsComputer and monitor - 400 wattsMicrowave - 350 wattsGeyser - 4.500 watts

Eliminate Voltage Unbalance

Voltage unbalance degrades the performance and shortens the life of a three-phase motor. Voltage unbalance at the motor stator terminals causes phase current unbalance far out of proportion to the voltage unbalance. Unbalanced currents lead to torque pulsations, increased vibrations and mechanical stresses, increased losses, and motor overheating, which results in a shorter winding insulation life.

Voltage unbalance is defined by the National Electrical Manufacturers Association (NEMA) as 100 times the absolute value of the maximum deviation of the line voltage from the average voltage on a three-phase system, divided by the average voltage. For example, if the measured line voltages are 462, 463, and 455 volts, the average is 460 volts. The voltage unbalance is:

 

(460 - 455) x 100 = 1.1%

460

It is recommended that the voltage unbalances at the motor terminals not exceed 1%. Unbalances over 1% require derating of the motor per Figure 20-2 of NEMA MG-1-1993, Rev 3, and will void most manufacturers' warranties. Common causes of voltage unbalance include:

• Faulty operation of power factor correction equipment.
  
• Unbalanced or unstable utility supply.
  
• Unbalanced transformer bank supplying a three-phase load that is too large for the bank.
  
• Unevenly distributed single-phase loads on the same power system.
  
• Unidentified single-phase to ground faults.
  
• An open circuit on the distribution system primary.
  

The efficiency of a rewound, 1800-RPM, 100-hp motor is given as a function of voltage unbalance and motor load in the table. The general trend of efficiency reduction with increased voltage unbalance is observed for all motors at all load conditions.

Voltage unbalance is probably the leading power quality problem that results in motor overheating and premature motor failure. If unbalanced voltages are detected, a thorough investigation should be undertaken to determine the cause. Energy and dollar savings occur when corrective actions are taken.

Example

Assume that the motor tested as shown in the above table was fully loaded and operated for 8000 hours per year, with an unbalanced voltage of 2.5%. With energy priced at $0.05/kWh, the annual energy and dollar savings, after corrective actions are taken, are:

Annual Energy Savings = 100 hp x 0.746 kW/hp x 8000 hrs/yr x (100/93 - 100/94.4) = 9517 kWh

Annual Dollar Savings = 9517 kWh x $0.05/kWh = $476

Memahami Tagihan Biaya Listrik

Dalam kondisi harga minyak yang masih belum stabil, adanya keterbatasan pasokan energi primer, keterbatasan kapasitas pembangkit (beban Jawa dan Bali saat ini lebih kurang sebesar 17.100 MW telah melebihi kapasitas yang tersedia yaitu sebesar 16.000 MW) serta keterbatasan penyediaan subsidi negara, maka untuk mengurangi beban subsidi tersebut langkah penghematan pemakaian energi listrik sudah menjadi suatu "keharusan". Pola perilaku tidak hemat masyarakat didalam mengkonsumsi listrik harus segera kita akhiri. Merubah perilaku masyarakat bukanlah sesuatu yang mudah. Oleh karena itu salah satu cara untuk mengubah perilaku tersebut adalah dengan cara menumbuhkan budaya hemat listrik, baik di lingkungan tempat tinggal maupun di

lingkungan tempat kerja. Langkah awal penghematan yang dapat dilakukan adalah dengan memahami terlebih dahulu bagaimana energi listrik yang telah kita gunakan setiap hari ditagihkan melalui tagihan rekening listrik setiap bulannya. Besarnya penghematan bergantung

kepada dalamnya analisa dan solusi yang diberikan dalam mengatasi masalah pemborosan yang terjadi. Disamping itu keterlibatan dari semua komponen dalam suatu perusahaan/organisasi mutlak diperlukan dalam menentukan berhasil tidaknya suatu perusahaan/organisasi didalam melaksanakan program penghematan. Dalam rangka mendukung tercapainya program penghematan pemakaian energy listrik dan mendorong masyarakat untuk dapat lebih berhemat, PT. PLN (Persero) mengeluarkan kebijakan dengan beberapa prinsip sebagai berikut :

1. Pelanggan yang memakai tenaga listrik sampai batas hemat tertentu (80 % dari pemakaian rata-rata nasional pada kelompok tarifnya) akan dikenakan tariff bersubsidi. Sedangkan bagi pelanggan yang tidak bisa berhemat (memakai melebihi batas hemat), kelebihan pemakaian listriknya akan dikenakan tarif non subsidi.
   
2. Pelanggan-pelanggan kecil dibawah 6.600 VA seperti pelanggan 450 VA, 900 VA, 1.300 VA, dan 2.200 VA tetap membayar rekening seperti biasa serta tidak terkena kebijakan ini, namun mereka dihimbau untuk tetap berhemat.
   
3. Ketentuan ini akan diberlakukan kepada pelanggan Rumah Tangga (R3), Bisnis (B), dan Pemerintah (P) dengan daya mulai dari 6.600 VA. Ketentuan ini mulai diberlakukan untuk rekening yang ditagihkan pada bulan Mei 2008. Pelanggan yang sudah terkena ketentuan "Dayamax Plus" tidak lagi terkena ketentuan ini.
   
4. Dengan ketentuan ini, maka skema kebijakan insentif dan disinsentif yang sebelumnya diusulkan PLN tidak digunakan lagi.
   
5. Basis perhitungan yang digunakan berdasarkan Tarif Dasar Listrik sesuai Keputusan Presiden No.104 tahun 2003, dimana tarif non subsidi merupakan penerapan tarif Mulfiguna (M) sebesar Rp.1380,-/kWh yang diatur dalam Kepres itu.
   

 

Ketentuan "Dayamax Plus" adalah sebagai berikut :

1. Ketentuan "Dayamax Plus" diberlakukan kepada pelanggan besar yang menggunakan listriknya pada saat Waktu Beban Puncak (WBP) apabila melebihi batas yang ditentukan
   
2. Ketentuan "Dayamax Plus" berdasarkan surat Edaran Direksi No. 0016.E/DIR/2005 tanggal 10 Agustus 2005
   
3. Ditujukan kepada kelompok pelanggan besar (tarif B3, I2, I3, I4, P2), agar mereka menghindari pemakaian listriknya pada saat Waktu Beban Puncak (WBP), diberlakukan mulai rekening bulan Oktober 2005
   
4. Ketentuan pembatasan pemakaian pada WBP :
   

• Untuk pemakaian daya : maksimum 50% dari daya kontrak
  
• Untuk pemakaian energi : maksimum 50% dari pemakaian WBP ratarata enam (6) bulan terakhir (rekening bulan Maret–Agustus'05)
  
• Untuk Pelanggan Baru (rekening terbit setelah Sept'05), kWh WBP Max dihitung berdasarkan : daya x Batas Jam Nyala rata2x DJBB
  

1. Berdasarkan pembatasan kWh WBP Max & kVA Max, pelanggan dikenakan Insentif dan Dis-Insentif
   
2. Insentif diberikan kepada Pelanggan apabila :
   

• Pemakaian pada saat WBP Tidak lebih / Sama dengan ( ≤ ) dari batas yaitu: kWh WBP Max dan kVA WBP Max
  
• Jika pelanggan menggunakan alat ukur mekanik, syarat insentif hanya pemakaian kWh WBP Max
  
• Nilai insentif maksimum = 50 % Biaya Beban
  
• Pelanggan yang mengalihkan pemakaian WBP ke LWBP, dapat mengajukan rencana pemakaian daya LWBP sampai dengan maksimum 2 x daya kontrak
  
• Insentif = Nilai Dasar + Nilai Tambahan
  
• Nilai Dasar = 50% kWh WBP Max x 50% tarif LWBP
  
• Nilai Tambahan (Besarnya yang dapat ditekan dari kWh WBP Max) =
  
• (kWh WBP Max – real kWh WBP) x 50% tarif LWBP
  

 

Daftar Istilah yang dipakai dalam Invoice :

1. Stand meter akhir adalah stand meter yang dibaca pada saat sekarang
   
2. Stand meter lalu adalah stand meter yang dibaca pada bulan yang lalu
   
3. Selisih adalah selisih stand meter akhir – stand meter lalu
   
4. Waktu Beban Puncak (WBP) adalah waktu jam 18.00 s/d jam 22.00 waktu setempat
   
5. Luar Waktu Beban Puncak (LWBP) adalah waktu jam 22.00 s/d 18.00 hari berikutnya
   
6. Batas Energi Max LWBP adalah batas energi max LWBP rata-rata selama 6 bulan
   
7. Batas Energi Max WBP adalah 50% rata-rata WBP selama 6 bulan
   
8. Faktor K adalah perbandingan harga kWh WBP dengan kWh LWBP
   
9. Faktor Kali adalah Rasio CT x Rasio VT
   
10. Daya tersambung adalah besarnya daya yang disepakati oleh PLN dan pelanggan dalam perjanjian jual beli Tenaga Listrik
    
11. Batas Daya Max (kVA) adalah 50% x Daya tersambung
    
12. Jam Nyala adalah pemakaian kWh per bulan dibagi dengan kVA tersambung
    
13. Kilo Watt hour (kWh) adalah satuan untuk daya nyata
    
14. Kilo Volt Ampere–reactive hour (kVArh) adalah satuan untuk daya reactive
    

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Writing user-friendly energy audit report

ABSTRACT

Energy audits don't save money and energy for companies unless the recommendations are implemented. Audit reports should be designed to encourage implementation, but often they impede it instead. In this paper, the authors discuss their experience with writing industrial energy audit reports and suggest some ways to make the reports more user-friendly. The goal in writing an audit report should not be the report itself; rather, it should be to achieve implementation of the report recommendations and thus achieve increased energy efficiency and energy cost savings for the customer.

WHAT IS A USER-FRIENDLY AUDIT REPORT?

People generally think of the term "user-friendly" related to something like a computer program. A program that is user-friendly is one that helps you use it with a minimum of difficulty. We apply the same term to audit reports to mean a report that communicates its information to the user (reader) with a minimum amount of effort on the reader's part. We operate on the belief that a reader who is busy will not want to spend his/her valuable time struggling to understand what the report is trying to say. If the report is not clear and easy to follow, the reader is likely to set it down to read later, and "later" may never come!

HOW DO YOU WRITE A USER-FRIENDLY AUDIT REPORT?

From our experience we have identified a number of key points for successfully writing a user-friendly audit report. These points are summarized below.

Know your audience.

The first thing to keep in mind when you start to write anything is to know who your audience is and tailor your writing to that audience. When writing an industrial audit report, your readers can range from the company president to the head of maintenance. If recommendations affect a number of groups in the company, each group leader may be given a copy of the report. Thus, you may have persons of varying backgrounds and degrees of education all looking at the report. Not all of them will necessarily have a technical background. The primary decision maker may not be an engineer; the person who implements the recommendations may not have a college degree.

We deal with this problem by writing a report with three basic sections. We start with an executive summary which briefly describes our recommend-ations and tabulates our results such as the energy and dollar savings and the simple payback times. We follow that with a brief description of a recommended energy management program for our client. Then we provide a detailed section that we call our technical supplement. This section of our report includes the calculations that support our recommend-ations and any specific information relating to implementation. (These sections are described more fully later in this paper.)

Use a simple, direct writing style

Technical writers often feel compelled to write in a third-person, passive, verbose style. Because energy audit reports are technical in nature, they often reflect this writing style. Instead, you should write your audit report in clear, understandable language. As noted above, your reader may not have a technical background. Even one who does will not be offended if the report is easy to read and understand. Some specific suggestions are:

Simplify your writing by using active voice. Writers often are reluctant to take responsibility for their recommendations; they use passive voice to avoid responsibility, saying "It is recommended..." or "It has been shown..." rather than "We recommend..." or "We have shown..."

Consider that you are addressing the report to one or more individuals. Write it as if you were speaking directly to the reader. Use the words "you" and "your." Make the report plain and simple.

Not: Installation of high-efficiency fluorescent lamps in place of the present lamps is recommended.

But: Install high-efficiency fluorescent lamps in place of your present lamps.

Or: We recommend that you install high-efficiency fluorescent lamps in place of your present lamps.

Not: Twelve air leaks were found in the compressor system during the audit of this facility.

But: We found twelve air leaks in the compressor system when we audited your facility.

Or: You have twelve air leaks in the compressor system.

Avoid technical jargon that your reader may not understand. Don't use acronyms such as ECO, EMO or EMR without explaining them. (Energy Conservation Opportunity, Energy Management Opportunity, Energy Management Recommendation.)

Present Information Visually

Often the concepts we are trying to convey in an audit report are not easy to explain in a limited number of words. Therefore, we often use drawings to show what we mean. For example, we have a diagram that shows how to place the lamps in fluorescent lighting fixtures when you are using reflectors and eliminating two of the lamps in a four-lamp fixture. We also have a diagram showing how a heat pipe works.

We present our client's energy use data visually with graphs showing the annual energy and demand usage by month. These graphs give a picture of use patterns. Any discrepancies in use show up clearly.

Make Calculation Sections Helpful.

The methodology and calculations used to develop specific energy management opportunity recommendations are potentially useful in an audit report. Including the methodology and calculations gives technical personnel the ability to check the accuracy of your assumptions and your work. However, not every reader wants to wade through pages describing the methodology and showing the calculations. Therefore, we provide this information in a technical supplement to our audit report. Since this section is clearly labeled as the technical supplement, other readers are put on notice as to the purpose of this section.

Use Commonly Understood Units.

In your report, be sure to use units that your client will understand. Discussing energy savings in terms of BTUs is not meaningful to the average reader. Kilowatt-hours for electricity or therms for natural gas are better units because most energy bills use these units.

Make Your Recommendations Clear.

Some writers assume that their readers will understand their recommendation even if it is not explicitly stated. Although the implied recommendation may often be clear, the better practice is to clearly state your recommendation so that your reader knows exactly what to do.

Not: Install occupancy sensors in the conference room and restrooms.

But: You should purchase 5 occupancy sensors; install one in the conference room and one in each of the four restrooms.

Explain Your Assumptions.

A major problem with many reports is a failure to explain the assumptions underlying the calculations. For example, when we use operating hours in a calculation, we show how we got the number. "Your facility operates from 7:30 am to 8:00 pm, five days a week, 51 weeks per year. Therefore, we will use 3188 hours in our calculations."

When you show your basic assumptions and calculations, the reader can make adjustments if those facts change. In our example above, if the facility decided to operate 24 hours per day, the reader would know where and how to make changes in operating hours because we had clearly labelled that calculation.

We use one section of our report to list our standard assumptions and calculations. That way we do not have to repeat the explanations for each of our recommendations. Some of the standard assumptions/calculations included in this section are operating hours, average cost of electricity, demand rate, off-peak cost of electricity, and the calculation of the fraction of air-conditioning load attributable to lighting.

Be Accurate and Consistent.

The integrity of a report is grounded in its accuracy. This does not just mean correctness of calculations. Clearly, inaccurate calculations will destroy a report's credibility. But other problems can also undermine the value of your report.

Be consistent throughout the report. Use the same terminology so your reader is not confused. Make sure that you use the same values. Don't use two different load factors for the same piece of equipment in different recommendations. This could happen if you calculated the loss of energy due to leaks from a compressor in one recommendation and the energy savings due to replacing the compressor motor with a high efficiency motor in another recommendation.

Proofread your report carefully. Typographical and spelling errors devalue an otherwise good product. With computer spell checkers, there is very little excuse for misspelled words. Your non-technical readers are likely to notice this type of error, and they will wonder if your technical calculations are similarly flawed.

REPORT SECTIONS

We have found that the following report format meets our clients' needs and fits our definition of a user-friendly report.

Executive Summary

The audit report should start with an executive summary which basically lists the recommended energy conservation measures and shows the implementation cost and dollar savings amount. This section is intended for the readers who only want to see the bottom line. Although the executive summary can be as simple as a short table, we add some brief text to explain the recommendations and sometimes include other special information needed to implement the recommendations. We also copy the executive summary on colored paper so that it stands out from the rest of the report.

Energy Management Plan

Following the executive summary, we provide some information to the decision makers on how to set up an energy management program in their facility. We view this section as one which encourages implementation of our report so we try to make it as helpful as possible.

Energy Action Plan. In this subsection, we describe the steps that a company should consider in order to start implementing our recommendations.

Energy Financing Options. We also include a short discussion of the ways that a company can pay for the recommendations. We cover the traditional use of company capital, loans for small businesses, utility incentive programs, and the shared savings approach of the energy service companies.

Maintenance Recommendations. We do not usually make formal maintenance recommendations in the technical supplement because the savings are not often easy to quantify. However, in this section of the report we provide energy-savings maintenance checklists for lighting, heating/ventilation/air-conditioning, and boilers.

The Technical Supplement

The technical supplement is the part of the report which contains the specific information about the facility and the audit recommendations. Our technical supplement has two main sections: one includes our assumptions and general calculations; the other describes the recommendations in detail including the calculations and methodology. We sometimes include a third section which describes measures that we analyzed and have determined are not cost-effective, or that have payback times beyond the client's planning horizon.

Standard Calculations and Assumptions

This section was briefly described above when we discussed the importance of explaining assumptions. Here we provide the reader with the basis for understanding many of our calculations and assumptions. We include a short description of the facility: square footage (both air-conditioned and unconditioned areas); materials of construction; type and level of insulation; etc. If we are breaking the facility down into sub-areas, we describe those areas and assign each an area number which is then used throughout the recommendation section.

Standard values calculated in this section include operating hours, average cost of electricity, demand rate, off-peak cost of electricity, and the calculation of the fraction of air-conditioning load attributable to lighting. When we calculate a value in this section, we label the variable with an identifier that remains consistent throughout the rest of the report.

Audit Recommendations

This section contains a discussion of each of the energy management opportunities we have determined to be cost-effective. Each energy management recommendation (or EMR) which was capsulized in the executive summary is described in depth here.

Again, we try to make the EMRs user-friendly. To do this, we put the narrative discussion at the beginning of a recommendation and leave the technical calculations for the very end. This way, we allow the readers to decide for themselves whether they want to wade through the calculations.

Each EMR starts with a table which summarizes the energy, demand and cost savings, implementation cost and simple payback period. Then we write a short narrative section which provides some brief background information about the recommended measure and explains how it should be implemented at this facility. If we are recommending installation of more than one item (lights, motors, air conditioning units, etc.), we often use a table to break down the savings by unit or by area.

The final section of each EMR is the calculation section. Here we explain the methodology that we use to arrive at our savings estimates. We provide the equations and show how the calculations are performed so that our clients can see what we have done. If they want to change our assumptions, they can. If some of the data we have used is incorrect, they can replace it with the correct data and recalculate the results. However, by placing the calculations away from the rest of the discussion rather than intermingling it, we don't scare off the readers who need to know the other information.

Appendix

We use an appendix for lengthy data tables. For example, we have a motor efficiencies table which we use in several of our EMRs. Instead of repeating it in each EMR, we put it in the appendix. We also include a table showing the facility's monthly energy use history and a table listing the major energy-using equipment. Similar to the calculation section of the EMRs, the appendix allows us to provide backup information with out cluttering up the main body of the report.

SHORT FORM AUDIT REPORT

Many energy auditors use a short form audit report. A short report is essential when the cost of the audit is a factor. Writing a long report can be time-consuming and it increases the cost of an audit.

The short form report is useful when an on-the-spot audit report is required because the auditor can use a lap-top computer to generate it. It is also an excellent format for preliminary audit reports when the company will have to do further analysis before implementing most of the recommendations.

However, some short form audit reports have drawbacks. When a report is ultra-short and only provides the basic numbers, the reader will not have a memory crutch if he returns to the report sometime after the auditor has left. Since some clients do not implement the recommendations immediately, but wait until they gather the necessary capital, an ultra-short form report may lose its value. Therefore, some explanatory text is a critical of a user-friendly short form report. The executive summary described above could serve as a model short form audit report.

FEEDBACK

Customer feedback is as appropriate in energy auditing as in any other endeavor. An easy way to get feedback is to give the customer a questionnaire to evaluate the audit service and the report. We list each section of the report, ask the client to rate each section on a scale of 1-10 with 1 being poor and 10 being excellent. We ask for a rating based on whether the section was easy to read and we ask for a rating of the likelihood that our recommendations will be implemented. (We also ask for any additional comments, but seldom get those.)

It is important that the questionnaire be easy to fill out. If it takes much time to read and fill out, the clients won't take time to return it. We used to send the questionnaire along with the report, but those were seldom returned. Now we wait for a month and then send the questionnaire as a follow up to the audit. We have a much greater return rate on those.

CONCLUSION

Many audit reports are not user-friendly. Most often, they are either lengthy documents full of explanations, justifications and calculations, or they are very short with little backup information. If a report is so long that it intimidates your readers by its very size, they may set it aside to read when they have more time. If it is so short that needed information is lacking, the readers may not believe the results.

Writing a user-friendly audit report is an important step in promoting implementation of audit recommendations. We hope that some of our report writing suggestions and some of our experiences can help others produce their own successful user-friendly energy audit reports.

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Pengujian Karakteristik Minyak Isolasi Trafo

Latar Belakang

• Didalam transformator ada dua bagian yang secara aktif membangkitkan panas yaitu tembaga (kumparan) dan besi (inti). Panas-panas itu bilamana tidak disalurkan atau diadakan pendinginan, akan menyebabkan tembaga atau besi itu mencapai suhu yang terlampau tinggi, sehingga bahan-bahan isolasi yang ada pada tembaga (kertas minyak) akan menjadi rusak.
  
• Untuk hal ini kebanyakan dilakukan dengan memasukkan inti maupun kumparan ke dalam minyak yaitu suatu jenis minyak tertentu yang dinamakan minyak isolasi (trafo).
  

Jenis minyak trafo

• Minyak trafo mineral: Minyak yang berbahan dasar dari pengolahan minyak bumi yaitu antara fraksi minyak diesel dan turbin yang mempunyai struktur kimia yang sangat kompleks.
  
• Minyak trafo sintetis (askarel): Minyak jenis ini mempunyai sifat lebih menguntungkan antara lain tidak mudah terbakar dan tidak mudah teroksidasi. Namun beracun dan dapat melukai kulit.
  

Minyak Mineral	Minyak Sintetis
Diala C, B (USA) Univolt (Esso) Nynas (Swedia) Mictrans (Jepang) Sun Ohm-MU (Korea) Petromin (Dubai) BP-Energol (UK)	Aroclor (USA) Clopen (Jerman) Phenoclor (Perancis) Pyroclor (UK) Fenclor (Itali) Pyralene (Perancis) Pyranol (USA)

Persyaratan Minyak Sebagai isolasi

• Viskositas yang rendah untuk mempermudah sirkulasi
  
• Titik nyala yang tinggi untuk mencegah terjadinya kebakaran
  
• Bebas asam untuk mencegah karat dari tembaga dan kerusakan pada isolasi belitan
  
• Tidak bersifat korosif
  
• Tahan terhadap oksidasi
  
• Mempunyai kekuatan dielektrik (tegangan tembus) yang tinggi
  
• Tidak mengandung sedimen
  

Tingkatan standar minyak trafo

No.			Standar
1.		IEC	International standard
2.		BS, ASTM, JIS, SNI	National specifications
3.		ABB, GEC-Ahlstom, Unindo	Transformer producer specifications
4.		TNB, PLN	Power distributor specifications

Pengujian minyak isolasi

Harga suatu transformator adalah mahal, tetapi memantau unjuk kerja sistem transformator melalui kondisi minyak tidak mahal dibanding dengan biaya jika transformator mengalami kegagalan (failure). Dengan demikian masa hidup transformator diharapkan lama kira-kira 40 tahun, bahkan dengan minyak trafo yang kualitasnya sangat baik diharapkan setara dengan masa hidup transformator.

Menurut studi yang dilakukan US Inspection and Insurance Companies, bahwa 10 % kegagalan transformator tenaga adalah karena deteriosasi bahan isolasi dan kegagalan internal "over load" dalam lilitan tegangan tinggi yang disebabkan bertambahnya deposit/ sludge.

Untuk itu pemantauan dan pemeliharaan kualitas minyak adalah sangat penting guna menjamin keandalan operasi peralatan listrik khususnya transformator, dan para ahli yang berwenang telah menetapkan petunjuk dalam bentuk standar uji dan spesifikasi teknik seperti IEC, ASTM, BS dll.

1. Minyak trafo baru (Unused mineral insulating oil) IEC 60296-2003
   
2. Minyak trafo pakai (Mineral oil in service) SPLN 49-1:1982 IEC 422:1982 diperbahurui menjadi IEC 422:1989
   

Ruang lingkup pengujian

Kimia	Fisika	kelistrikan
Keasaman Kadar air Ketahanan oksidasi Korosi lempengan tembaga Sedimen	Viskositas Densitas Titik nyala Tegangan antar muka Titik tuang	Tegangan tembus Tahanan jenis Faktor kebocoran dielektrik, tan delta

Batasan Minyak Isolasi Baru IEC 60296-2003

No.	Parameter uji	Batasan
1.	Fungsi
1.1	Viskositas pada 40 oC	Max. 12 cSt
1.2	Titik tuang	Max. – 40 oC
1.3	Kadar air	Max. 30 mg/kg
1.4	Tegangan tembus : - Sebelum treatment - Setelah treatment	Min. 30 kV /2.5mm Min. 70 kV /2.5mm
1.5	Densitas pada 20 oC	Max. 0,895 g/ml
1.6	Faktor kebocoran dielektrik, tan d pada 90 oC	Max. 0,0005
2.	Stabilitas
2.1	Keasaman	Max. 0,01 mg KOH/kg
2.2	Tegangan antar muka	Min. 40 dyne/m
2.3	Korosif sulfur	Tidak korosif
2.4	Kadar sulfur	Tidak disyaratkan
2.5	Aditif anti oksidan	U: Tidak terdedeksi T: Max. 0,08 % I: 0,08 % - 0,4 %.
2.6	Kadar furfural	Max. 0,1 mg/kg
3.	Unjuk kerja
3.1	Ketahanan oksidasi : - Sedimen - Keasaman - DDF at 90oC	Max. 0,8 % Max. 1,2 mg KOH/g Max. 0,500
3.2	Gassing tendency	Tidak disyaratkan
4.	Keamanan
4.1	Titik nyala	Min. 135 oC
4.2	PCA	Max. 3 %
4.3	PCB	Tidak terukur

Batasan Minyak Isolasi Bekas Pakai IEC 422:1989

No.	Parameter	Batasan
1	Tegangan tembus	50 kV untuk tegangan > 170 kV 40 kV untuk teg. 70 – 170 kV 30 kV untuk tegangan < 70 kV
2	Kadar air	< 20 mg/kg untuk > 170 kV < 30 mg/kg untuk < 170 kV
3	Angka kenetralan (keasaman)	0,5 mgKOH/g
4	Sedimen	Tidak terukur ( > 0,02% )
5	Tahanan jenis	Min. 1 G Ω.m
No.	Parameter	Batasan
6	Faktor kebocoran dielektrik Tg delta pada 90 oC	Max. 0,2 untuk tegangan > 170 kV Max. 1,0 untuk tegangan < 170 kV
7	Tegangan permukaan	Min. 15 dyne/cm
8	Kandungan gas	IEC 577 dan IEC 599
9	Titik nyala	Max. penurunan 15 oC

Masalah Masalah Hasil Pengujian

1. Teknik sampling tidak sesuai prosedur (50%)
   
2. Human error
   
3. Kesalahan analisis
   

Uji Viskositas

Viskositas adalah suatu ukuran dari besarnya perlawanan yang diberikan oleh minyak untuk mengalir, atau ukuran dari besarnya tekanan geser bagian dalam dari suatu bahan cair. Bila suhu naik maka viskositas akan turun. Uji viskositas hanya dilakukan untuk minyak isolasi baru. Metoda yang dipakai mengacu pada ISO 3104.

Uji Densitas

Densitas adalah berat masa minyak per satuan volume (kg/l) pada suhu 20 ^oC. Uji ini dilakukan hanya untuk minyak minyak isolasi baru. Metode uji densitas mengacu ke standar ISO 3675

Uji titik nyala

Titik nyala adalah adalah suhu terendah dimana uap minyak mulai menyala. Metoda ini dipakai untuk mendeteksi kontaminasi minyak yang berupa bahan bahan yang mudah menguap. Titik nyala rendah mengindikasikan terdapat kandungan yang bersifat volatile combustible. Titik nyala diuji dengan sistem Closed Cup dan mengacu pada standar ISO 2719

Uji tegangan antar muka

Metode ini mencakup pengukuran pada kondisi ketidak seimbangan tegangan antara permukaan minyak mineral yang berlawanan dengan air. Indikasinya ditunjukkan dengan adanya kontaminasi hasil dari oksidasi minyak. Pengujian mengacu pada standar ISO 6295.

Uji warna

Warna adalah banyaknya intensitas sinar yang diteruskan dan dinyatakan dengan angkan yang berdasarkan perbandingan terhadap sederetan standar warna. Bertambahnya intensitas warna menunjukkan bahwa minyak telah terkontaminasi. Metode uji yan dipakai adalah ASTM D 1500.

Uji titik tuang

Titik tuang adalah suhu terendah dimana minyak dapat mengalir pada saat didinginkan dan kondisi suhu tertentu. Sesuai standar pengujian mengacu ke standar ISO 3016.

Uji keasaman (angka kenetralan)

Keasaman (angka kenetralan) dalam minyak isolasi menunjukkan adanya kontaminan hasil oksidasi yang bersifat asam. Uji ini sangat dibutuhkan untuk suatu penggantian minyak. Pengujian mengacu ke standar IEC 296:1982 dan 296: 2003

Uji sedimen

Sedimen merupakan kontaminan pada minyak pakai dan terjadi karena proses oksidasi, pengujian mengacu ke standar IEC 422.

Uji Kadar air

Kandungan air dalam minyak isolasi berasal dari udara (atmosfir), diuji dengan metoda Karl Fisher Coulometric dan mengacu pada standar IEC 814.

Uji oksidasi

Uji ketahanan oksidasi adalah peristiwa oksidasi minyak dengan kondisi dan waktu tertentu atau ukuran baik tidaknya (ketahanan) suatu minyak trafo baru terhadap oksidasi. Dalam proses ini akan menghasilkan sedimen dan asam. Pengujian mengacu kestandar IEC 74.

Uji korosi kepingan tembaga

Uji korosi kepingan tembaga adalah suatu uji kemampuan minyak isolasi untuk mengakibatkan korosi pada kepingan tembaga dengan waktu dan suhu tertentu. Dengan adanya korosif senyawa sulfur yang merugikan akan menghasilkan deteriosasi pada logam yang besarnya tergantung pada jumlah dan tipe korosif, waktu dan suhu. Pengujian mengacu ke standar ASTM 1275 B.

Uji tegangan tembus

Tegangan tembus adalah tegangan dalam kV yang diperlukan untuk menembus lapisan minyak setebal 1 cm diantara 2 buah elektroda dan dinyatakan dalam kv/cm dalam kondisi suhu kamar. Tegangan tembus yang rendah menunjukkan adanya kontaminasi seperti air, kotoran atau partikel yang tidak dikehendaki. Metode uji yang dipakai adalah standar IEC 156.

Uji DGA (Dissolved Gas Analysis)

Metode ini mencakup ekstraksi dan pengukuran gas-gas terlarut dalam minyak isolasi. Gas-gas tersebut dihasilkan dari hasil oksidasi yang berasal dari minyak isolasi dan kertas (selulosa) seperti hidrogen, metan, etan, etilen, asetilen, karbon monoksida, karbon dioksida. Pengujian ini bertujuan untuk mengetahui kondisi dan gangguan (fault) yang terjadi pada operasional trafo.

Gangguan yang terjadi pada trafo yaitu :

• Thermal fault < 300 ^oC, 300 – 700 ^oC dan > 700 ^oC
  
• Electrical fault ( partial discharge, low energi discharge/ sparking & high energy discharge/ arcing ).
  

Standar acuan : ASTM 3612 & IEEE C 57

UJI FAKTOR KEBOCORAN DIELEKTRIK TAN d PADA 90 ^oC DAN TAHANAN JENIS PADA 90 ^oC

Faktor kebocoran dielektrik sangat terpengaruh oleh adanya kontaminan,dan sedimen hasil oksidasi atau koloid. Pengujian dilakukan pada suhu 90 ^oC pada minyak baru ataupun minyak pakai dan mengacu pada standar IEC 247.

Klasifikasi Minyak Isolasi Pakai

KATEGORI 1: Kondisi minyak isolasi sangat memuaskan untuk meneruskan operasi, semua parameter dibawah limit yang direkomendasikan IEC 422-1989

KATEGORI 2: Kondisi minyak isolasi perlu untuk dilakukan reconditioning ( purifier/ vacum filter). Indikasinya kadar air tinggi, tegangan tembus rendah dan parameter yang lain memuaskan

KATEGORI 3 : Kondisi minyak isolasi perlu dilakukan reclaiming, Indikasinya parameter keasaman dan faktor kebocoran dielektrik sudah tinggi.

KATEGORI 4: Kondisi minyak isolasi sudah tidak memenuhi spesifikasi sebagai minyak isolasi pakai dan tidak bisa digunakan lagi.