FR2780898A1 - Treatment of transformer cooling oils by filtration through pre-dried ion exchange resins - Google Patents

Abstract

Treatment of transformer cooling oil with ion exchange resins it has been found possible to alleviate problems from static electrical build up and discharging across insulating paper cartridges. The transformer oil is passed successively through pre-dried cationic and anionic exchange resins

Description

I

  PROCESS FOR TREATING COOLING OILS

  TRANSFORMER BY ION EXCHANGE RESINS.

  The present invention relates to a process for processing transformer cooling oils.

by ion exchange resins.

  Some transformers are cooled by oil, this cooling oil permeates the paper

  and transformer winding insulation boxes.

  In some cases, electrostatic discharges tend to occur on contact with paper or cardboard insulation and oil. When these discharges are too large, serious problems of breakdown of the insulation are encountered, which results in significant production losses. The static electrification of the oil is linked to its circulation speed and its temperature. In order to avoid these problems, several solutions have been considered. First of all, it has been envisaged to completely replace the oil whose characteristics are atypical with new oil. However, it turned out that shortly after replacing the oil in a transformer, new breakdown problems appeared. Another proposed solution therefore consisted no longer in replacing the oil but in treating

  the oil whose characteristics are atypical.

  As a treatment method, attempts have been made to inject benzotriazole into the oil. The results obtained by the Applicant on transformer oils by this treatment are not yet

not entirely satisfactory.

  Transformer oils from refinery and new test oils

  transformers are treated with earth at Foulon.

  However, since Foulon earth cannot be regenerated, its use for treating transformer oil in operation would prove to be costly and difficult to implement. In order to solve this problem of static electrification of transformer cooling oils, the present inventors have found, surprisingly and unexpectedly, that it was possible to treat said oils by passing over anionic resins and

  cationic dried beforehand.

  The process according to the invention is characterized in that the oils to be treated are passed over at least one anionic resin and at least one resin

  cationic, said resins being dried beforehand.

  It is possible to use a single cationic resin and a single anionic resin or else several cationic resins and several anionic resins. The resins are arranged in a bunk bed, the oil therefore passes through a layer of resin of a certain type and then passes through a

resin layer of the other type.

  According to a preferred embodiment, the oils are first treated with anionic resins and

  then by cationic resins.

  In the process according to the invention, the anionic resins are chosen from the group comprising in particular resins whose active groups are

weak weak bases.

  For example, the anionic resin is a resin

  AMBERLYST A21 marketed by ROHM and HAAS.

  As for the cationic resins, they are chosen from the group comprising in particular resins whose active groups are acids, preferably

  sulfonic acid. For example, the LEWATIT S 100H + cationic resin sold by the company BAYER is used.

  In order to prevent the transfer of resin into the oil, after the treatment by passage over the said

resins, oils are filtered.

  The anionic and cationic resins are dried beforehand, for example in an oven, so that their water content is determined so as not to increase the water content of the treated oil by more than approximately 5 ppm. The drying temperature and the drying time are of course determined by a person skilled in the art depending on the nature of the resins used and

l5 of their water content.

  The present invention will now be better understood with the aid of examples given purely by way of illustration.

Examples:

  In the examples below, an anionic resin sold by the company ROHM and HAAS under the brand AMBERLYST YST A21 was used and a cationic resin sold by the company BAYER under the name

LEWATIT S 100 H + brand.

  These resins were dried in an oven for 48 h

at 105 C.

  In the examples below, the following measurements have been made: Measurement of electrostatic discharges by ECT "on site" at 25 C associated with the resistivity and the potential of charges, - Measurement of the dielectric dissipation factor of the oil (tangent 6) at 90 C and in aging, associated with the measurement of the conductivity at 25 C and 90 C, according to the NFC standard

27210,

  - Metal content (copper, iron, lead and tin), - Water content according to standard NFC 27229, - Interface tension, - Dielectric strength according to standard NFC 27221,

- Acidity.

Example 1

  liters of oil (oil 1) were withdrawn from

  transformer with malfunctions.

  The oil before treatment had the characteristics

described in Table 1.

  The first liter of this oil was percolated at ambient temperature and pressure for 3 h 30 on the anionic resin and then for 5 h 30 on the cationic resin. Then the following four liters were percolated under low vacuum (730 mmHg) for 40 minutes on anionic resin and then for 1 hour 15 minutes on cationic resin.

  This oil was then filtered.

  The results of the measurements of the various characteristics of this oil thus treated are taken up

in table 1.

  As can be seen from this table 1, the treatment improves the ECT and the tangent 6.

Table 1:

  OIL I BEFORE TREATMENT AFTER TREATMENT

  EC.T. (pJC / m3) 47 8.2 Resistivity (Ohm. Cm) at 25 C 1.51.1014 0.34.1014 Load potential (A. Ohm.cm) 65000 2620 Water content (ppm) 10 13 Interfacial tension (mN / m ) 33.5 25.3 Dielectric strength (kV) 68 55 Tan. 6 to 90 C 414.104 40.104 Tan. 6 in aging 1348.104 153.10'4 Conductivity (S / m) at 25 C 31.25.10-12 4.10-12 Conductivity (S / m) at 90 C 253.10-12 24.4.10-'2 Copper content (ppm) 5, 41 4.30 Iron cenc (ppm) <0.025 <0.025 Lead content (ppm) <0.025 <0.025 Tin content (ppm) <0.500 <0.500 Sulfur content (ppm) 800 809 Acidity (mg KOH / g 0.042 0.031

Example 2:

  In the same way as in Example 1, liters of an oil (oil 2) drawn off from another transformer were treated. This oil had the

  characteristics defined in table 2 below.

  The characteristics of the oil after treatment in accordance with the invention are also included in the

table 2 below.

Table 2:

  OIL 2 BEFORE TREATMENT AFTER TREATMENT

  E.C.T. (QC / m3) 96 7 Resistivity (Ohm. Cm) 0.037.1014 0.64.10'4 Load potential (A. Ohm.cm) 3272 4035 Water content (ppm) 6 7 Interfacial tension (mN / m) 44.5 42 , 2 Dielectric strength (kV) 79.5 83 Tan. 8 to 90 C 84.104 83.104 Tan.8 in aging 189.104 83.104 Conductivity (S / m) at 25 C 29.6.10-12 1.23. 10'12 Conductivity (S / m) at 90 C 51.1.10-12 51. 10-12 Copper content (ppm) 0.36 0.200 Iron content (ppm) <0.025 <0.025 Lead content ( ppm) <0.025 <0.025 Tin content (ppm) <0.500 <0.500 Sulfur content (ppm) 750 717 Acidity (mg KOH / g of oil) 0.026 0.029

Claims (6)

  1. Process for treating transformer cooling oils, characterized in that said oils are passed over at least one cationic resin and at least one anionic resin,   said resins being dried beforehand.   2. Method according to claim 1, characterized in that said oils first pass through a layer consisting of at least one anionic resin and then a   layer consisting of at least one cationic resin.   3. Method according to any one of   Claims 1 to 2, characterized in that after   passage through anionic and cationic resins, oils are filtered.   4. Method according to any one of   Claims 1 to 3, characterized in that the   anionic resins are chosen from the group comprising in particular resins whose active groups are weak weak bases.   5. Method according to any one of   Claims 1 to 3, characterized in that the   cationic resins are chosen from the group comprising in particular resins whose active groups   are acids, preferably sulfonic acid.   6. Method according to any one of   Claims 1 to 5, characterized in that the   drying is carried out for a sufficient time and at a sufficient temperature so that the water content of the resins is determined so as not to increase the content of   oil water over about 5 ppm.