Extention of transformer service life time: how to?

Power transformers are the most widely used elements of power plant and power distribution systems. Operation of transformers is an important factor in reliability of power transformation, distribution and transmission.

Most transformer currently in operation are either nearing their projected service life, or have already exceeded it. Full scale replacement of all such equipment is not feasible due to the obviously prohibitive costs. This makes the issue of transformer service life extension quite important. Is there a solution? The answer is yes.

During operation, the transformer undergoes both irreversible and reversible changes. The former include thermal oxidation of winding insulation, various internal damage, which requires disassembly of the equipment to repair and replace the failed components. However, many performance characteristics can be restored entirely on site.

Care about transformer oil is care about the transformer

Petroleum based transformer oil is widely used as dielectric an heat dissipation agent in many electrical systems. Analysis of transformer failure and damage shows that the service life of transformer is defined by the condition of the insulation.

During operation the oil accumulates various contaminants and aging products. In the presence of oxygen and water the dielectric fluid oxidizes even in ideal conditions. This process causes the formation of acids, which react with carbon and metal, forming aldehydes, alcohols, soaps etc.

Contaminated oil thickens and increases viscosity. This degrades the heat dissipation capability, reducing the transformer life time.

The optimal solution is oil reclamation. The reclamation process removes contaminants and decomposition (aging) products from the oil, restoring the essential operational parameters.

GlobeCore has developed and put into production the CMM-12R units, specifically for extension of transformer life time by restoring the dielectric strength and chemical composition of the electrical insulation oil.

СММ-12R operation principle: fuller’s earth filtration of mineral oil

The CMM-12R units regenerate and restore transformer oil by percolation of the oil through Fuller’s earth sorbent: it’s fuller’s earth filtration. Beside, this system can heat, degas, dry and filter the dielectric fluid. Sorbent reactivation occurs alonig with processing of the oil – inside the unit. After reactivation the Fuller’s earth can be used normally.

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The СММ-12R is connected directly to the transformer tank, forming a closed oil circulation line: the oil to be regenerated flows into the unit, processed oil flows back into the transformer. The flow of oil, along with vibration and heat in the transformer, also facilitates removal of contaminants from cellulose insulation.

After GlobeCore’ oil reclamation process, the oil is chemically identical to new dielectric fluid. Additives improve the oil’s oxidation stability, further extending its service life.

Advantages of СММ-12R unit for oil reclamation:

  • mobility and onsite operation;
  • oil reclamation without taking the transformer offline and setting up tanks for oil transfer and storage;
  • reactivation of sorbent directly in the unit. The sorbent can be reactivated up to 300 times, the equivalent of 1,5-2 years of operation;
  • removal of both solved and unsolved contaminants from the used oil;
  • process automation. The system operates according to the program and does not require operator intervention;
  • operator comfort (separate work place, PC controls, ventilation);
  • optional equipment to control oil level in the transformer, a generator for autonomous operation, inhibitor injection section to add oxidation stabilizer into the oil.

Specifications of CMM-12R for Oil Reclamation

Parameter

Value

1 Capacity, m3/hour, min

4

2 Processed oil parameters:
Moisture by weight, g/t(ppm) as per IEC 733; ASTM D-1533

5

Filtration, µm

5

Volumetric gas content in % as per IEC 60599; ASTM D-3612

0,1

Acid number, mg KOH/g as per IEC 296; ASTM D-664

0,01

Corrosive sulfur, ISO 5662; ASTM D-1275

None

Dielectric strength, kV, IEC 156; ASTM D-1816

70

Interfacial tension, N/m, at 25ºС, ISO 6295; ASTM D-2285

45

Dissipation factor at 90ºС, IEC 247; ASTM D-924

0,001

Oxidation stability

Acid number, mg KOH/g,

IEC 1125А; IEC 1125B; IP-307

0,2

3 Max oil output temperature in heating mode, ºС

90

4 Outlet pressure, bar, not less than

1,5

5 Oil heater power, kW, not more than

54

6 Max power consumption, kW

69

7 Power parameters
voltage, V

380

AC frequency, Hz

50

Client benefits after purchasing the unit for fuller’s earth filtration:

  • complete restoration of transformer oil;
  • extension of transformer life time from 20 to 35 years;
  • significant reduction of storage space required for waste oil;
  • saving on buying new oil and disposing of waste oil;
  • training of client’s personnel;
  • Starting and commissioning of the unit by our engineering team on site (if necessary);
  • qualified consulting by GlobeCore experts during operation of the oil reclamation unit.

GlobeCore equipment can be in stock or custom design. Stock models can be purchased directly from the factory’s warehouse. Custom orders require 45 work days lead time.

обновлено: June 24, 2016 автором: dannik