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Best Way to Transformer oil degassing?

Transformer oil degassing

Transformer oil degasification

Oxygen found in transformer oil leads to oxidation and significantly reduces the dielectric strength of the oil and the insulating system.  In general, under normal atmospheric pressure, the insulating oil contains approximately 10% of atmospheric air.  The higher the temperature, the better the dissolution of air in oil wll be.  It is highly important to understand that the composition of atmospheric air and the air dissolved in oil, differ greatly.  Atmospheric air is comprised of 78% nitrogen and 21% oxygen.  When that same air is dissolved in oil, it becomes comprised of 69.8% nitrogen and 30.2 oxygen.

Transformer oil degassing is a complex of processes targeted at the removal of water, gasses, and mechanical impurities from the dielectric oil.  The following methods may be used for drying the oil:

  • centrifugation  In this case, mechanical impurities and water are removed from oil, influenced by centrifugal forces.  In practice, this method is applied mainly for oils that will be used for equipment with a voltage of no less than 35 kV.
  • adsorption  Water and impurities are removed by using mineral and synthetic adsorbents.  This method allows for the removal of water dissolved in the oil;
  • vacuum drying  Oil is heated up and then is pumped through a degasifier.

Vacuum processing is considered to be the most effective method since it removes dissolved water and gasses from  the oil.  This process is realized either by spraying oil in vacuum chambers or using special heaters that are evenly distributed in the vacuum chamber utilizing Raschig rings and grid packings.  There are special oil degassing units used to perform the degassing and vacuumizing processes.

The main part of such equipment is a degasifier that consists of two tanks.  The vacuum in the tanks is created by vacuum pump system.  Additionally, there are spraying devices on the tank cap that distribute oil evenly in the vacuum chamber.  Oil Degassing takes place when oil flows in thin streams on the surface of Raschig rings.

The method of vacuum spraying is based on the spraying of the oil and water solution in the vacuum by a pulverizing jet into a special tank.  These processes allow for the removal of free and dissolved moisture as well as dissolved air.  If the level of oil dispersion is adequately thin, it easily gets rid of moisture.

Vacuum drying includes three main stages such as:

(1) breakdown voltage increases very sharply due to the removal of emulsion water;

(2) there are minor changes of the breakdown voltage of oil (60 kV) At this time dissolved and loosely-coupled water is removed; and

(3) breakdown voltage increases slowly due to the removal of bound water.

The efficiency of vacuum drying of transformer oil is improved when it is warmed up because the amount of evaporable moisture is increased.

GlobeCore has developed the CMM line of vacuum units for transformer oil purification to solve the problems that arise when mounting, repairing and servicing oil-filled equipment with a voltage up to 1150 kV.

To meet the needs of our customers, each unit is custom made and can be puchased in may come in pad-mounted version, or placed on single axle or tandem trailers.  The technical characteristics of the CMM units are described below.

Transformer oil degassing

 

 

CMM hot dry air supply system

The unit can be operated in three operation modes:

  • air drying and heating mode
  • adsorbent (other equipment filled with) regeneration mode.
  • adsorbent regeneration (the unit filled with) mode – (regeneration of technical specifications of damp synthetic zeolite by means of hot air heating up to the temperature of 380 – 400 °С).

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cmm degassing

 

CMM transformer evacuation units

The unit pumps air, non-aggressive gases, vapors and air-steam mixtures out of the transformers and hermetical vacuum systems.

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iney degas system

 

INEY: Transformer oil degasification unit

The company manufactures three types of units, which differ in components, mode of operation and specifications, but are equally efficient. First type – single module unit consisting of two-stage refrigerator, designed for generation of process cold (to negative 70оС); Second type – twin module unit with vacuum backing pump:

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Servicing Transformer Substations: Emergency Response

Servicing of transformer substations is a very important process which facilitates reliable transmission and distribution of power. A part of this service is a possible emergency response.

During the service life of equipment most of defects do not appear immediately, but develop gradually. An example would be the destruction of cable terminals by high temperature. Another cause of accidents is excessive vibration, which has a gradual effect. The other causes of breakdowns are contamination of insulation, leakage of oil from transformers and circuit breakers, water contact in switchgear and controls.

Also, there are cases of negligence by operators that results in failures. The responsibility of the staff is to make decisions on restoring normal operation of equipment, while adhering to relevant requirements and regulations.

The guide to be taken when an electrical emergency arises: (Electrical Safety Regulations for Employees)

  1. Remove hazard to personnel and equipment, if it exists. Disable damaged equipment.
  2. Exclude human intervention in automatic operation of devices.
  3. Ensure operation of devices with power backup.
  4. Determine the nature and extent of damage with measuring devices.
  5. Inform an operator, who calls the maintenance personnel or a service crew.

With no communication with an operator on duty, the staff should eliminate or contain an accident. It is necessary to inform the neighboring facility about a shutdown of power for consumers for the duration of the emergency response.

Electric power companies are obliged to periodically organize staff training for emergency response in emergency simulators, and train employees in the basic steps of accident prevention and how to behave properly in extreme situations.

Integral Transformer Substations for Indoor Installation

substations

Integral transformer substations are built for indoor and outdoor installations. This article looks at indoor substations.

It is designed for unheated premises of industrial enterprises. The substations with one transformer (right and left) and two transformers (in single line and parallel)  are very common. In the two transformer substations the sections are connected by double busbar systems. Depending on the requirements of the distance between the opposite fronts (according to order) it  may be 1800, 2300 or 2800 mm.

Standard components of integral transformer substations:

  • circuit breakers and switchgear devices;
  • transformer;
  • capacitors and voltage regulators.

Integral transformer substations use dry transformers and oil-filled transformers.  The choice of a particular type of transformer depends on the power of the substation.

Low voltage switchgear consists of a steel frame (a cabinet) containing a bus, a power cell with a circuit breaker, disconnect switches, earthing devices and current transformers. For prompt service the cabinets can be accessed from the front. The bus assembly and cable connections are serviced from the rear side of the cabinet. The door is provided for convenience of installation and maintenance, and is generally closed.

Indoor high voltage switchgear also contains circuit breakers and relay protection.

Indoor low voltage switchgear has the busbar systems without additional joint assemblies.

AC power is measured by active and reactive meters. They are usually placed on the meter cabinet door.  The customer can request a heated meter cabinet.

Substations with two transformers are equipped with an automatic transfer switch (ATS), which is necessary to turn off the disconnect switch and bus-section breaker. The ATS changes between equipment for an emergency source of power. Also the ATS is used when normal power source fails, and when automatic operation is at fault.

Electric Purification of oil

purification of oil

Purification of oil. Mechanical impurities in oil are removed by an electric field. This approach is not entirely new, but it is not widely used at this time due to insufficient studies of the processes occurring during the interaction of the electric field and oil.

Electro-cleaning sediments suspended particles under the influence of an electrostatic field, which appears between the electrode and the particles. Particles acquire a charge as a result of electrical charging. At the same time a number of phenomena is observed in the space between the electrodes: a partial electrical leakage, recharge of some particles and electric liquid convection, etc.

The particles are influenced by hydraulic resistance forces and electrostatic forces causing the particles to precipitate on the electrode.

The main advantages of electric cleaning of oil are:

  • Compact size of equipment, compared to settling tanks;
  • No moving parts, compared to the centrifuge;
  • Stable capacity and hydraulic resistance;
  • Automatic performance.

However, there are several other issues. In particular, this process is not fully studied, especially the electrodes coated with an insulating material, which can recharge particles and lose them from the cleaning process. As a result, the device loses its effectiveness. Also, electro-cleaning devices are complex in design and require highly qualified operators. These aspects prevent the widespread use of electro-cleaning units in oil purification.

Compressor Oil for Piston-type and Rotary Compressors

compressor oil

Compressor oils are divided into classes depending on their application and requirements. The most common classifications is:

  • Oils for rotary and piston-type compressors;
  • Oils for refrigeration compressors;
  • Oils for turbo machines.

Let us consider in full detail the oil of the first type. It is used for lubrication of compressors in transportation and various industries. Requirements for the rotary and piston type compressor oils are defined by the composition and properties of the compressed gas which contacts the oil.

Apart from being used as a lubricant for the valves and cylinders of piston-type compressors, the oil is also used as a sealing medium for the compression chamber.

The main property of compressor oil is the thermal oxidation stability and the ability to prevent formation of coke deposits on the injection lines of compressors. The discharge temperature affects thermal oxidation stability.

Viscosity is also an important property of compressor oils. It determines the loss of energy through friction and wear of the surfaces of parts and seals of piston rings

Purity of compressor oils

Due to the fact that the application of compressor oils is similar to application of piston engine oils, the requirements for both oils are similar. Both are subjected to abrasion in a cylinder-piston group and in a crank mechanism.

The presence of water in compressor oil is determined by the Dean-Stark method, and is not allowed.

Cleaning of compressor oils

Contaminated with mechanical impurities and water, the compressor oil can not be used for its intended purpose.

The oil purification units by GlobeCore remove mechanical impurities, water and gas from compressor oils. Clean oil increases the performance of compressor equipment and reduces potential downtime. GlobeCore plants extend the life of both the oil and the compressor.

To receive advice on compressor oil purification plants, please call the numbers on our website in the “Contacts” section.

Heating oil: properties and uses

Compared with diesel fuel, heating oil has a wide range of applications due to its composition.

Heating oil is produced from used diesel fractions in direct fraction distillation. Fractional composition of heating oil can be harder than fractional composition of diesel fuel. The viscosity of heating oil is 8 mm2/sec, and diesel is 6 mm2/sec.

To date there are no regulations that impose restrictions on the cetane number and iodine, or a cloud point of heating oil. The sulfur content of this petroleum product can be up to 1.1% by weight.

Table 1 compares the hydrocarbons content of diesel fuel and heating oil.

Table 1

The average hydrocarbon composition of diesel fuel and heating oil

Hydrocarbons

Hydrocarbon content,% vol.

Heating oil

Diesel fuel

Paraffin

3,62

32,49

Naphthenes

7,51

31,72

Indanes, tetralines

26,61

6,69

Alkyl benzene

23,52

11,65

Indene

7,4

1,74

Naphthalene

15,29

0,59

Naphthalenes

5,42

7,11

Acenaphthene

4,93

4,06

Acenaphthylene

3,24

2,76

Еricyclic aromatics

2,26

1,18

Total

100

100

Heating oil is used in stationary steam boilers and industrial furnaces. It is also used as fuel in marine power plants. In agriculture, heating oil is used in forage preparation, also in food preservation in canning and drying of fruit and grain.

Transformer oil testing: determining moisture content

transformer oil testing

Transformer oil testing. Technical requirements for transformer oils are stated by the standards. At the same time, these standards do not directly regulate the moisture content of oil. The regulation in this case is done indirectly by a number of parameters, such as density, flash point, viscosity, content of KOH, dielectric strength, and others.

The moisture content in insulating oil is now determined by a visual inspection, calcium carbide method and liquid chromatography method, known as the Fischer method. The first method is purely subjective and only allows to determine the fact of moisture presence in transformer oil. Other methods are rather cumbersome and time-consuming and require oil sampling.

At this moment, there are no direct methods for determining the intensity of aging of insulating liquid. Therefore it is necessary to use indirect methods of oil condition monitoring such as estimating oil absorption capacity, conductivity, polarization or ionisation. The oil is rejected when its parameters exceed the  specified values.

The new methods to control the level of moisture in the isolation without switching the equipment offline improve the efficiency of diagnosis, and make the monitoring process more automated.

Combined Methods for Waste Oil Purification

Waste Oil Purification

Waste Oil Purification. Waste oil treatment uses a combination of approaches based on different methods (force field and porous membrane).

Centrifuges use a combination of electric and centrifugal fields. The electric field is generated by the outside power source or the triboelectric effect, creating a non-uniform field that improves the efficiency of cleaning.

The cleaning efficiency of waste oil can be increased with ferromagnetic particles in magnetic and centrifugal fields. For this purpose the centrifuge rotor is equipped with permanent magnets. Also, purification is improved by combining force fields and porous filters.

Waste Oil Purification. There are also hydrodynamic filters which combine the inertial forces and filtration. The filter cleans itself in the process, when the oil flows along the filter membrane or the membrane is moved against the oil flow. The character of the movement may vary: recurrent, rotary or reciprocating.

The main advantage of the hydrodynamic filters with a fixed filter element is their simple design and minimal maintenance. But their drawback is losing some of the cleaned oil along with waste. In general, we have the following pattern: the higher the degree of purification, the greater the losses. The solution would be to move a filter against the oil stream, but this complicates the design of the cleaner and the use of mechanical, pneumatic or hydraulic gear system. The cleaning efficiency of the hydrodynamic filters can be improved with electric precipitation devices.

Filtering centrifuges combine centrifugal force and filtration. The wall of the rotor is made of porous material. The pressure difference across the filter is created by the centrifugal force, and the impurities get trapped in the filter material.

Magnetic filters combine filter elements for non-magnetic particles with a permanent magnet for ferromagnetic contaminants. The filter elements, beside the main function, also protect the magnets from oil aging products. Such devices can clean waste oil with a lot of metal particles.

110 kV Transformers: Structural Features

110 kV Transformers

Power transformer is an important part of the electrical power transmission system. It converts one voltage to another, starting from 110 kV transformers to 220 kV transformers. In this article we will talk about the design of 110 kV transformers.

In 110 kV transformers there are bushings at the top and the neutral wire at the bottom; the core is made from windings of low-voltage and high-voltage and the pole. It uses two insulating cylinders 6 mm thick. The windings are pressed together with the pressing rings and angular washers are made from electro cardboard.

The thickness of insulation barriers that separate high-voltage windings are 8 mm.

The surge protection for high-voltage windings is ensured by the voltage-controlling capacitor bushing. The binding is made of half dry glass material.

In case you need to move a 110 kV transformer, its tank is provided with four roller bearings positioned between carriages. High-voltage bushings of oil-paper insulation are installed on the mounting flange. The lower part of these bushings is covered by synthetic resin bonded paper cylinders and by a covering plate made of magnetic material to align electric fields.

The structure of the cooling system consists of a straight-tube heat exchanger, which is fan cooled. The fans are powered by distribution boxes that are connected to the main line.

The other parts of the 110 kV transformer are similar to other transformers and are only different in weight and size.

Where Does Used Industrial Oil Go?

Industrial Oil

Industrial Oil. Industrial oils are widely used in industry for lubricating friction parts.

In adverse operating conditions, with increasing running speeds, loads and temperatures, there are higher requirements to the quality of industrial oils. Even the liquids of the highest quality do not guarantee that they maintain their properties for the duration of the service life. They are contaminated with metal particles, particles of rubber seals and other impurities as well as oxidation products. These cause failures of expensive machinery and equipment. Therefore, it is necessary to maintain the purity of industrial oil, and replace it when its properties deteriorate.

There is a logical question. Where do we put used industrial oil, as it can accumulate over time? It cannot be drained into the soil and waterways, because it causes serious environmental problems. It also causes health problems for people exposed to waste oils.

It is recommended to regenerate waste industrial oil and reuse it for its original purpose, or use it for production of new commercial oils.

In practice, regeneration of industrial oils uses physical, chemical and physico-chemical methods. In this article we will focus on the physical methods.

The most commonly used method is filtration through porous septum, made of high quality filtering materials. In coarse filtering of industrial oil the filtration fineness is generally 70 … 100 micron, medium filtration is 20 … 60 micron, fine filtration 1 … 20 micron, and ultra-fine filtration less than 0.1 microns.

Flexible filter elements may be made of fabrics and fibers. Rigid filters are made of powder from different grains processed by baking and pressing. Other filters are bulk filters and precoat filters

Also there are slot filters used for oil purification (plate-type filters, belt filters, wire mesh filters and channel filters).

The filter is selected according to the necessary degree of purification. The industrial waste oil is generally cleaned by intermittent filters that have a simple design and can operate at different pressures. Their disadvantage is the necessity to stop for replacement and washing.