Tag Archives: types

The Oil Pump: Types and Varieties

The purpose of the oil pump is self-explanatory. This is a device to exert pressure on the oil to transport it from one place in the system to another.

In terms of control, there are two types of pumps: one type can adjust pressure in the system by changing capacity, others cannot.

There are two types of oil pumps:

  • rotary pumps;
  • gear pumps.

Rotary pumps push the oil by the vanes of the rotor, gear pump do it by gear wheels. Gear pumps can also be of two types: with external and internal gear contact. With the same capacity, the size of internal gear pumps is generally smaller than external ones.

To facilitate circulation of transformer oil, centrifugal pumps are used. They are driven by three phase short-circuited motors. Using pumps  with packless seals allows to avoid contamination of oil. These devices can work with any medium which is not aggressive to the pump construction materials, contains no abrasive particles and has lubricating properties.

Transformer Damage and Oil Regeneration/Oil Reclamation

An electric power transformer Damage is one of the most important elements of the modern electric grid no matter where in the world a particula grid may be located.  Transformer failures result in significant financial expenditures, and will require the transmission company to buy new transforners or repair the damaged ones at significant cost and service interuptions.

Many historians note that there was great industrial boom observed in the first decade followintg the end of World War II.  At that time, there was a rapid increase in electric power consumption.  To meet the growing demand for electric power, new transformers had to constantly be put into operation.  Since that time, mant of the older transformers have become outdated and pose a big risk of unscheduled service interuptions.

Older transformers’ obsolescence however, is not the only problem facing the modern power grids.  The power loads on the obsolete transformers are increasing because of ever increasing power consumption.  It requires significant expenditures to replace the broken or obsolete transformer since the price for a new transformer is very high.

It is therefore, advisable to take measures to extend the service life of transformers already in service.  To succeed in undertaking a sucessful preventive maintenance program, one should understand the nature of the failures that make transformers unserviceable in the first place.

In 2003, the International Association of Engineering Insurers (IMIA) started to explore the reasons for transformer failures servicing the combined USA power grids.  The results were rather interesting.  Table 1 shows the economic losses caused by different types of transformer failures.

Table 1

Economical Losses Caused by Different Transformer failures

Nature of Failure

Amount of Cases

Economical Loss in $

Insulation defects

24%

149,967,277.00

Problems with designing, material or installation

22%

64,969,051.00

Unknown failures

15%

29,776,245.00

Oil contamination

4%

11,836,367.00

Overloading

5%

8,568,768.00

Inflammation/explosion

3%

8,045,771.00

Network overvoltage

4%

4,959,691.00

Operational failures

5%

3,518,783.00

Water ingress

2%

2,240,198.00

Poor contacts

6%

2,186,725.00

Lightning stroke

3%

657,935.00

Insulation moistening

1%

175,000.00

In total

94%

286,628,811.00

It is not an overstatement to say that if proper and timely preventive maintenance of the insulating systems is performed, many, if not all transformer failures can be prevented.  The insulating system of the power transformer consists of bith solid and liquid insulation.  The solid insulation is made of hygroscopic material (cellulose) also known as “Kraft Paper.”  The liquid insulation features a dielectric fluid known as transformer insulating oil.  In general, these two kinds of insulation are interdependent, but also help to contaminate each because degradation products from the solid insulation may get into oil and oil oxidation sludges may penetrate into the solid insulation from the oil.  Simply changing the transformer oil therefore, will not completely resolve the problem of restoring and cleaning the entire insulation system.  Unfortunatelt, oxidation products are accumulated in the cellulose insulation and are not removed when oil is simply changed.  And when only an oil changed is performed, these oxidation products will migrate get into new oil accelerating the aging process of the new oil and shortening its effective service life.  Additionally, the contamination that remains in the solid insulation will continue to degrade and damage the Kraft Paper leading to transformer failure.

This problem may be solved with the advanced GlobeCore regeneration technologies.  The GlobeCore mobile oil recycling stations, designated as the CMM-R line of equipment may be connected to either an energized or non-energized transformer.  In such a way, oil is circulated through a closed path: used oil flows to the oil treatment station and goes back to the transformer being cleaned and restored.  The contaminants resulting from the aging process are washed out due to the constant circulation. This advanced type of equipment performs a complete oil regeneration service and removes all contamination for the transformer core, windings and solid insulation.

GlobeCore mobile oil stations perform  the following operations:

  1. filtration with or without heating (processed oil is of 9th ISO 4406 purity class and with nominal filtration fineness, ranging from 0.5…1 micron);
  2. dehydration (the moisture content of the processed oil is no more than 5 g/t (5ppm);
  3. degassing (volumetric gas content of the processed oil is no more than 0.1 %);
  4. increase the dielectric breakdown voltage (no less than  70 kV (kilovolt));
  5. drying of electrical equipment and oil purification simultaneously;
  6. regenerate insulating oil, using bleaching clay;
  7. vacuum transformers and other electrical equipment;
  8. remove acids;
  9. remove soluble oil decomposition products;
  10. lighten insulating oil; and
  11. restore oxidation and gasification stability;

The GlоbeCоre technologies provide for service life extension of transformers and reduction of financial expenditures on maintenance.  Save money with GlоbeCоre!

Oil Filled Electric Power Transformer Repairs: Types and Causes

According to international standards, oil filled electric power transformer repairs are divided into three types: (1) minor repairs; (2) moderate repairs (Intermediate Maintenance); and (3) complete overhaul (Depot Maintenance).  Minor repairs usually include only preventive maintenance, although some minor corrective maintenance may be included in this category.  Minor repairs, including preventive maintenance, can be and usually are performed on site.  In this category of maintenance, the transformer is not opened and the external power supply is not disconnected from the transformer.  Minor repairs are usually performed by local service personnel.

The time needed to perform minor repairs and preventive maintenance will depend on the power of the transformer and may vary from several hours to as much as 1– 5 days.

Moderate repairs, or intermediate maintenance, includes all the operations of minor repairs and above, but usually requires the of opening of the transformer, lifting of the core, replacement of terminals (as required), coolant, switches, valves, oil pumps etc.  Another major difference between moderate repairs and minor repairs is that it is always performed on a transformer that is disconnected from the power supply and performed at special repair sites known as depot maintenance facilities.

A complete overhaul includes the operations of moderate repairs with the addition of core repairs (with dis-assembly and restoration), replacement of the windings and the solid insulation.  In some cases, the magnetic system is also repaired.  The most common causes, that require a complete overhaul, is severe damage to the core, the windings and the paper insulation, usually as a result of surges and insulation failure.   Insulating paper failure is usually due to a combination of age and degradation due to neglected preventive maintenance.

In order to avoid failures and the need to perform intermediate maintenance or a complete overhaul, it is important to routinely perform timely preventive maintenance.  “Preventive Maintenance” serves to assess the service condition of the equipment and is designed prevent failures, service interruptions, and most importantly, it is designed to extend the service life of the transformer.  Preventive maintenance is performed on transformers of 110 kV and above and 80 MVA.  Preventive maintenance should be performed on transformers within 10 years of being placed into service and as necessary thereafter.  The decision to perform preventive maintenance is made depending on the current condition, years of service, and test results from minor repairs including oil sampling and analysis.

Over time, the transformer’s insulating oil will degrade and lose its performance qualities and capabilities.  Once an oil has reached an “Acid Number” of 0.08, the oil must be regenerated with the GlobeCore Process to prevent damage of the core and the insulating paper.  GlobeCore offers its clients a unique solution: the UVR type regeneration units.  The UVR Units are versatile and can regenerate and restore not only transformer oils, but other types of oil as well including hydraulic fluid, turbine oil, and other industrial oils and fluids.  The UVR regeneration system lightens diesel and heavy fuel oil, gas condensate, petroleum and kerosene.

The UVR plants can be used by any related facility since they require no special placement, are easily transported and do not generate noise during operation.

Its time to get with the Process, The GlobeCore Process!