Thermal oil circulation treatment
Why need a thermal oil circulation?
After running transformers and other oil-filled power equipment for a period of time, both thermal and electrical failures will cause the insulation medium to decompose and release distinct characteristic gases. Because the bonding energy of carbon and hydrogen bonds in transformer oil and paper insulation structure is low, hydrogen is usually created first in the decomposition process, making hydrogen one of the main components of various fault characteristic gases.
The following are the reasons why hydrogen gas will be created in transformer oil and the usual treatment methods(thermal oil circulation):
To begin, there are three primary methods for producing hydrogen through breakdown.
1．Water electrolysis and chemical reaction with iron
2．Alkane cracking reaction
3．Cyclohexane dehydrogenation reaction
Second, what therapy procedures are used for the three reasons stated above?
1、The hydrogen produced by the electrolysis of water and the chemical reaction with iron can be eliminated using either the hot oil circulation method or the oil change method to re-inject vacuum oil (the latter is more expensive).
2、The hydrogen and hydrocarbon produced by the cracking reaction of alkane should be identified using chromatographic analysis, three ratios, inspection, and other means of comprehensive judgment to determine the nature of the defect and then treated accordingly.
3、The vacuum degassing method/thermal oil circulation method can be used to remove excess hydrogen gas created by the dehydrogenation reaction of cyclohexane.
The thermal oil circulation method is the treatment method of transformer oil for hydrogen exceeding standard. What are the precise operation procedures of the thermal oil circulation technique?
(1). The oil purifier machine inlet line is connected to the transformer’s bottom valve, and the oil purifier machine outlet line is connected to the transformer’s top oil injection valve.
(2). After vacuuming the oil purifier machine inlet pipe, start the vacuum pump, open the oil purifier machine inlet valve, and open the transformer bottom valve to prepare the oil purifier inlet for self-circulation heating of heated oil. Open the top of the transformer’s oil injection valve, discharge the air in the oil injection tube through the vacuum pump, and open the oil purifier machine discharge valve for thermal oil circulation heating.
(3). When the oil purifier outlet pipeline is connected, use the bleeder plug on the oil injection valve at the top of the transformer body to discharge the gas in the pipeline, filling the oil pipeline with oil, and then open the valve at the top of the body to perform thermal oil circulation.
(4). Before starting the oil circulation, ensure that the moisture absorber is appropriately mounted and that it may breathe freely.
(5). When the oil purifier machine exit oil temperature is less than 50 °C, the temperature in the oil tank shall not be less than 40 °C. After the hot oil cycle, the oil should be sampled and tested to ensure that it meets the handover test parameters.
(6). After the hot oil cycle is completed, the voltage should be permitted to stand for at least 24 hours, 220 and 330kV for at least 48 hours, and 500kV for at least 72 hours.
(7). After resting, the transformer should be emptied multiple times from the casing, elevated seat, cooling device, gas relay, and pressure release mechanism, among other things, and the submerged oil pump should be started until the associated gas is exhausted.
(8). The exhaust in the oil storage cabinet must comply with the manufacturer’s specifications.
If other specific circumstances exist, thermal oil circulation operation steps can be agreed upon in conjunction with the creation of particular technical solutions.
In summary, the thermal oil circulation process should prioritize temperature, valves, static, exhaust, and oil quality.
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