Oil degassing in step-up transformers is a challenge that wind farm maintenance companies often face. In this article, we will discuss the causes of increased gas generation in wind farm local transformers, as well as technologies and equipment for degassing oil in such transformers.
Purpose of transformers used in wind farms
The share of wind energy in the total global electricity generation is growing every year. This trend is due to the fact that wind energy is safer and more environmentally friendly, as well as inexhaustible, unlike oil, gas or coal.
In the general case, the wind generator converts the kinetic energy of the wind into electrical energy, and then the generated energy is transmitted to the general network to end users. Transformers are the key elements in the power transmission system. In the case of wind turbines, these are two types of step-up transformers. The first type is a local transformer connected to each turbine directly. Previously this transformer was installed at the top of the turbine, but now, for ease of maintenance, such transformers are installed either at the bottom of the turbine or on the site directly next to the turbine. The second type is a transformer that collects the power of several local transformers and increases the voltage to the mains voltage.
Why oil degassing in step-up transformers is necessary
Practical operational experience shows that local transformers connected to the wind turbine directly generate abnormally large amounts of dissolved gases. And the gas content usually increases with time and at the same speed. Excessive gas generation creates risks to the transformer insulation system and can even lead to transformer explosion under adverse conditions. Therefore periodic transformer oil degassing and periodic restoration of the content of dissolved gases in oil to safe values are necessary.
Oil degassing in wind farm step-up transformers
In order to solve this problem the GlobeCore company has developed transformer oil deep degassing technology with an output of 1,000 to 17,000 liters of oil per hour, which is implemented in CMM-type transformer oil degassing machines.
The degassing process in these machines is implemented by means of a two-stage vacuum system, which consists of a fore-vacuum pump and a booster one. This system allows developing a deep vacuum and allows wind turbines local transformers oil degassing to a volume content of gases of no more than 0.1%.
In addition CMM transformer oil degassing machines are equipped with coarse and fine filters and with a heater. This makes transformer oil filtering and dehydration possible. After oil passing through the CMM machine the oil purity corresponds to 16/14/12 class according to ISO 4406 and 6 class according to NAS 1638.
CMM machines may have additional options for the wind turbines local transformers maintenance convenience. In particular, this is the retrofitting of the TOR-8 device, which allows measuring the gas content in the oil before and after processing. Or retrofitting with the TSS safety system, the use of which allows oil to be degassed directly in the functioning transformer. Also CMM machines can be manufactured on a wheeled trailer, due to which the equipment can be delivered quickly even to remote wind farms by road transport.
Wind farms step-up transformers online monitoring
GlobeCore also has a solution for online monitoring of wind turbines local transformers. This is the TOR-5 system. It detects important transformer parameters with the use of sensors and calculation algorithms. These parameters are transformer oil quality factor, cellulose insulation moisture content, oil hydrogen content, oil breakdown voltage. The TOR-5 system transmits the parameters to a special web application. In this application you can detect visually how critical the value of a particular parameter is and make changes to the transformer maintenance program if necessary.
The use of GlobeCore technologies makes it possible to increase the reliability of the wind turbines step-up transformers due to the timely transformer oil degassing. It also reduces the risks of equipment downtime and shortages of power supply.