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Sustainable Electric Power for the

Emerging Markets

WHITE PAPER © 2017 AGC Refining & Filtration LLC

AGC REFINING & FILTRATION

SUSTAINABLE ELECTRIC POWER FOR THE EMERGING MARKETS 2

Contents Abstract 3

A Master Plan 3

Transformer Maintenance 9

Summary of Required Equipment and Parameters 13

Security 14

Conclusion 15



Abstract

Lack of power impacts annual growth rates, slowing the development of new businesses and inhibiting new investment. The demand for power can lead to new investments in large-scale power projects in addition to creating markets for smaller generators of power.

The purpose of this white paper is to present a master plan for a practical and cost-effective solution to maintaining the existing power infrastructure in good operating condition. This plan is applicable for all providers of electricity in the local community. The solution centers on the two most important aspects of power transformer maintenance:

A diagnostic program

A preventive maintenance program

The paper will show that these two aspects can be implemented economically without the purchase and use of expensive and complicated equipment.

The solutions presented have been implemented worldwide and have proven effective in reducing the cost of providing electricity.

The Management of the Allen Group

January 2009

A Master Plan

This white paper presents a master plan for the improvement of the reliability of a local community’s power transformers. It consists of:

1. Diagnostic methods (a description of required methods and diagnostic equipment)

a. Infrared scans

b. Moisture detection

c. Fault gases detection

d. Acidity detection

e. PCB detection and elimination

2. Transformer maintenance (a description of a comprehensive maintenance plan)

a. A routine maintenance program and the equipment required

b. Tap changer filter systems

3. A plan for increased security at unmanned substations

a. The installation of perimeter security cameras and lights

b. The installation of a remote sensing network interconnecting the security cameras

Diagnostic Methods

Two of the most important types of maintenance for insuring a long transformer service life are preventative and reactive.

In practice transformer maintenance procedures combine preventive diagnostics with routine and sometimes reactive maintenance. This combination is only effective when:



The necessary diagnostic equipment and skills to operate and interpret the results are available

The routine or reactive maintenance procedures using the proper equipment are applied properly and in time

Such a plan has three elements:

1. Obtaining a baseline operating characteristic of the transformers (signature)

2. Determining the schedule for periodic re-testing or monitoring

3. Obtaining the basic equipment to insure regular monitoring

Transformers from different manufacturers can have great variations in their basic operating characteristics. These differences are due to design, materials, and factory procedures. However, a relatively low-cost preventive maintenance program can be implemented by investing in capital equipment and the training of personnel.

Infrared Scans

If a transformer has been energized for a minimum of twenty-four hours, then a complete infrared scan using an infrared camera should be done.

The complete scan should include:

All wall surfaces

All external bushings and connections

All individual cooling systems

Transition compartments

Load tap changer compartment

Control cabinet

Power supply connections

All other accessory devices

This infrared thermography scan should be performed a minimum of once a year for every transformer. A typical infrared survey scan is shown below:

Figure 1: Typical Infrared Scan Showing a Hot Spot



Figure 2: Typical Thermal Imager

Equipped with a camera and voice recorder and optimized for field use in harsh environments, the thermal imager delivers and stores clear images. Images are stored for download to a PC. A training DVD is included.

Moisture Detection

Moisture is one of the worst contaminants of insulating oil. If the oil is sampled for moisture at all, often a single sample is taken and analyzed by the Karl Fischer Test. This test gives an absolute value of total moisture content in parts per million or its equivalent in milligrams per liter. This value is meaningless even if the oil temperature is recorded at the time the sample was taken. The reasons include the following:

The absolute moisture content of the oil does not reflect the moisture content of the paper insulation

The result of the Karl Fischer test does not reflect the relative saturation of the moisture in the oil

The relative saturation is the percentage of full-water saturation (100%). This is the most representative figure of the amount of moisture available in the oil for transfer into the paper insulation. At equilibrium the relative saturations of both the oil and the paper are equal. (See also the white paper titled, Water Activity In Oil)

The relative saturation must be recorded along with the oil temperature at the sampling point.

Oil temperatures at the top and bottom can also be recorded along with load to determine the temperature in the insulation components. This data can be averaged over time to account for the slow diffusion rate involved in the migration of water between paper and oil.

Figure 3: Hand-Held Moisture Meter

Measurement with the hand-held moisture meter is independent of oil type and temperature. Readings indicate margin to oil saturation. In-line readings can be taken through a ball valve; there is no need to drain the oil. Meters are made of rugged field construction.



Fault Gases Detection

Insulating materials inside a transformer break down and liberate gases into the insulating oil. The types and distribution of these gases can be related to the type of electrical fault. The rate at which the gases are generated can indicate the severity of the fault. This becomes a valuable tool in any preventive maintenance program. After a transformer has been energized for a minimum of twenty-four hours an oil sample should be taken for the dissolved gas analysis (DGA). This should be done at least twice a year. More frequent testing may be needed if the DGA data indicate an increase in the rate of gases generated over time.

Figure 4: A Typical Portable Dissolved Gas Analyzer

Compact and light, the portable dissolved gas analyzer analyzes for six different gases (acetylene, carbon monoxide, hydrogen, methane, ethylene, ethane, and carbon dioxide) as well as total combustible gas (TGA). The unit performs rapid measurements and requires only a small oil sample (50 cc).

Fault gases are generated inside a transformer by:

Arcing

Thermal heating

Corona or partial discharge

The difference in these categories is the amount of energy that is released by the fault per unit time, per unit volume. The most severe intensity of energy dissipation occurs with arcing, less with heating, and least with corona.

Figure 5: Arcing Versus Corona

Arcing

Corona

The fault gases that can be found in a transformer are shown in the following three groups:

1. Hydrocarbons and hydrogen

a. Methane



b. Ethane

c. Ethylene

d. Acetylene

e. Hydrogen

2. Carbon oxides

a. Carbon monoxide

b. Carbon dioxide

3. Non-fault gases

a. Nitrogen

b. Oxygen

Table 1: Typical Amounts of Gases Released During a Particular Fault

Hydrogen Carbon Dioxide

Carbon Monoxide

Methane Ethane Ethylene Acetylene

Arcing in Oil 39% 2% 4% 10% — 6% 35%

Overheating in Oil

16% Trace Trace 16% 6% 41% Trace

Overheating in Cellulose

9% 25% 50% 8% — 4% Trace

Corona in Oil 88% 1% 1% 6% 1% Trace Trace

The concentration of fault gases in oil is dependent upon:

The solubility of the gas in the oil

The temperature of the oil

Hydrogen is the least soluble gas while acetylene is the most soluble gas in oil. Hydrogen can accumulate in the space above the oil and create an explosion hazard.

The majority of these fault gases are generally very soluble in oil, which is very important to take into account. Also, the solubility of gases increases with increased temperatures.

The following table shows the solubility of fault gases in transformer oil at static equilibrium of 30 inHg (760 mmHg) and 77°F (25°C):



Table 2: Solubility of Fault Gases in Transformer Oil at Static Equilibrium of 30 inHg (760 mmHg) and

77°F (25°C)

Solubility Gas % by Volume

Least soluble, most flammable and dangerous

Hydrogen 7

Nitrogen 9

Carbon Monoxide 9

Oxygen 16

Methane 30

Carbon Dioxide 120

Ethane 280

Ethylene 280

Most soluble Acetylene 400

It is important to note that over a temperature range of 0 to 176°F (0 to 80°C) some gases increase in solubility up to 79%, while others decrease their solubility by up to 60%.

Figure 6: A Typical Online Monitor for Dissolved Fault Gases

The monitor measures accurate and repeatable measurements of eight critical fault gases. In addition it correlates moisture-in-oil, oil temperature, and ambient temperature to the transformer load. Supports IEEE and IEC diagnostic tools for rapid warning and diagnosis of developing faults.

Online-dissolved gas analyzers are an excellent means for identifying problems at an early stage before they become critical and irreversible. The information generated by the analyzer can be transmitted to a SCADA system or via the Internet.

Acidity Detection

Moisture reacts with the sulfur in the presence of oxygen and—through a process called hydrolysis—creates acidity. This is shown in a rise in the total acid number (TAN). The acid will promote sludge formation and in turn, will deteriorate the paper insulation.



Figure 7: Dexsil Test to Determine Water Content of Transformer Oil

Quickly and easily quantify water content in oil with the auto-calibrated meter.

PCB Detection and Elimination

The Dexsil PCB/Chloride Analyzer is a field-portable instrument that incorporates an ion-specific electrode to quantify chlorinated compounds. Powered by a rechargeable battery or AC power, it can quantify chlorinated compounds from 3 to 2,000 parts per million (ppm).

Figure 8: A Typical PCB Detection Analyzer

Transformer Maintenance Routine Maintenance

From the information given in the previous pages, it is evident that an economical maintenance program can be simple and does not require a large budget. The most important part of the transformer is the insulating oil. If this oil is correctly and regularly maintained then the transformers will likely last 30 to 40 years or longer.

A basic insulating oil maintenance program requires the removal of the major contaminants such as:

Moisture

Gases

Solids

The only way to remove most if not all of these contaminants is by vacuum distillation.

This is a process whereby the boiling points of the contaminants in the oil are lowered while subjected to filtration, heat, and vacuum.

This causes a phase-separation and a mass transfer, whereby the contaminants are vaporized and discharged into the atmosphere. The resulting clean, dry, and degassed oil is returned to the transformer while the transformer is on-line.



While there are many manufacturers that make a bewildering variety of vacuum systems, only a few have proven to have a long track record of producing successful purification systems. Most are cheap imitations that promise performance—usually at low cost—but fail after a short service life.

The only way to identify a good system is for engineers to become totally familiar with the principles upon which the good quality systems are based. (See also the paper titled, Selection Parameters for Vacuum Distillation Systems)

Equipment Required for Maintenance of Transformers and Tap Changers

Vacuum Distillation Systems

Allen Filters, Inc. manufactures two basic types of vacuum distillation systems:

1. A system for large power transformers

2. A system for medium- to small-sized transformers

A third type of vacuum distillation system is the multi-purpose vacuum distillation system.

The latter system can purify both turbine lubrication oil and transformer insulation oil using a proprietary (patent pending) Allen Filters design. The systems are usually designed for operation in hazardous (explosion-proof) areas.

The oil purification systems for the large transformers and those for the medium- to small-sized transformers differ only in size. The process for both is fundamentally the same.

The process proceeds as follows:

1. While the transformer is on-line, the Oil Conditioner is connected to the transformer in a “kidney loop” fashion, with oil flowing out of the transformer into the Oil Conditioner. After purification—either in a single pass or in multiple passes—the oil goes through the Oil Conditioner and returns to the transformer.

2. During each pass through the system, the oil is first filtered through a solids pre-filter, heated by a low-watt density immersion heater and then subjected to high vacuum.

3. Contaminants are vaporized and ejected while the clean, dry, and degassed oil returns to the transformer.

4. An optional fuller’s earth adsorption filter will neutralize excessive acidity in the oil.

5. In case a fuller’s earth filter is used, a final fine-solids filter is recommended to remove any finer material that may have been generated.

6. Optional accessories are an on-line moisture analyzer and an on-line particle counter with the ability to transmit system information and process data to a central location via the Internet.

7. The interconnectivity can be extended to the diagnostic data which the operator can download on a laptop computer. The computer instantly transmits the data via the Internet to a central location for diagnostic evaluation.

8. Alternatively, the data can be transmitted to Allen Filters, Inc. on a regular basis—via an Internet link—for a no-cost evaluation of the transformer and tap changer conditions.



Figure 9: A Typical Large Transformer Oil Conditioner Mounted in a Trailer

Figure 10: A Large Transformer Being Prepared for Purification

The purifier is inside the trailer.

Figure 11: A Typical Stationary Medium-Sized Transformer Oil Purifier



Figure 12: Typical Multi-Purpose Trailer Mounted Systems

The Vacuum Distillation Process of the Allen Oil Conditioner

The standard process flow diagram for a transformer Oil Conditioner (see figure 13) shows a system that is uncomplicated, fully automatic, requires a minimum of operator attention, and designed for some of the most rugged terrain such as jungle, ocean, and desert conditions. The process is entirely controlled by a programmable logic controller (PLC). All the operator has to do is hook up the inlet and discharge lines to the transformer and then push the start button on the control panel.

A PLC accurately controls the right combination of heat and vacuum which is critical for the mass transfer of contaminants from dissolved phase into the vapor phase.

The contaminants are condensed in the condensate tank upstream of the vacuum pump. This prevents corrosive condensate from destroying the vacuum pump. The discharge pump returns the clean, dry oil to the transformer. Options include a Fuller’s Earth Adsorption Vessel and a final filter. Allen Filters, Inc. Oil Conditioners for transformer oil are fully automatic, reliable, and economical to purchase and operate. Our equipment is at work in 57 countries around the world. In many cases equipment sold in the 1960s is still operational.



Figure 13: Process Flow Diagram of an Allen Filters Oil Conditioner for Transformer Oil

Summary of Required Equipment and Parameters Diagnostic Equipment

Infrared Camera

A test kit for water content in oil

A test kit for TAN

A test kit for PCB detection

Oil Purification Equipment

An Allen Oil Conditioner for transformer oil

Trailer mounted, open, or enclosed

A truck to pull the Oil Conditioner from one transformer to the next on a regular basis

Clean Transformer Oil Purification Parameters

Dielectric strength: 56 kilovolt (kV) minimum, ASTM test no. D1816 with VDE electrodes at 0.08 in (2 mm) gap

Water: 35 ppm maximum, ASTM test no. D1533

Acidity: 0.03 mg KOH/gm oil maximum, ASTM test no. D974

Flash point: 293°F (145°C) minimum, ASTM test no. D92

Viscosity: 12 centistokes (cSt) at 104°F (40°C) maximum, ASTM test no. D88

Specific gravity: 0.91 at 59°F (15°C) maximum, ASTM test no. D1298

Diagnostic Evaluations

Allen Filters provides a free diagnostic service for anyone. Just e-mail your oil quality data to [email protected] and we will provide you with a free analysis and diagnosis.



Security

Perimeter Security

Perimeter security for unmanned substations can be provided by a surveillance systems consisting of outdoor day- and night-vision cameras, which are installed on poles along the four corners of the perimeter fencing.

Video & Infrared Camera Equipment

The recommended system uses the new industry standard H.264 high-quality compression technology for video storage and supports a full 30 frames-per-second live viewing and recording on all cameras.

Interconnectivity

At a resolution of 704 x 480, excellent detail is visible. The cameras provide clear color video during the day and instant night vision in complete darkness. The system allows the ability to remotely view live and recorded video from any high-speed Internet connection or third-generation cell phone. It is possible to connect from any system using Microsoft Internet Explorer without the need to install additional software. A software package is included that provides multiple simultaneous connections. This allows monitoring multiple surveillance sites at the same time from one central location. The following pages show some of the camera models:

Figure 14: Super High-resolution 550-line Bullet Security Camera with Night Vision

See up to 49 ft. (15 m) in complete darkness. Camera is weather proof and designed for outdoor use.

Figure 15: Long Range, High-resolution Zoom

See up to 197 ft. (60 m) during the day in normal color vision and up to 1,427 ft. (435 m) in complete darkness using night vision. Zooms from 8 mm to 40 mm.



Conclusion

Sustainability is the objective of The Allen Group’s business through Allen Filters’s sustainability program of providing our technology, equipment, and training at a reasonable cost to countries with emerging markets.

The program’s objective is the improvement of those countries and communities in developing regions through the transfer of technology for the productive use of affordable electricity and the stimulation of local economic growth.

www.AGCInternational.com

3045 East Elm Street

Springfield, Missouri 65802, USA

Toll Free: +1 800 865 3208

Phone: +1 417 865 2844

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