A traction transformer is one of the important equipment that ensures the continuity of railway traffic. It powers the AC traction motors of electric trains and electric locomotives, and it also powers auxiliary electrical systems such as electric heating and lighting of the carriages. In this article, we will focus on the specifics of traction transformer maintenance and, in particular, transformer oil purification.
Basic requirements for electric train traction transformers
Traction transformers, unlike stationary ones, must function reliably and without additional repairs in the interval between scheduled periodic repairs. They must function with a significant deviation of the voltage on the pantograph above the nominal value. They must be resistant to vibrations and shocks, and significant dynamic loads also. They must withstand the effects of switching overvoltages on the windings. Traction transformers heat up during functioning. The releasing heat is removed due to the circulation of special oil in the cooling system. The oil temperature should not exceed 85 degrees Celsius.
Only high-quality oil with a breakdown voltage of at least 35 kilovolts and with an absence of mechanical impurities and water, can provide reliable heat removal without overheating itself.
The use of a traction transformer with low-quality oil can lead to a sudden stop of an electric train halfway or lead to a fire in the transformer, which threatens the passengers’ lives and threatens the railway with great financial losses.
In this article we will look at GlobeCore’s complex solutions that make it possible to treat oil before filling a traction transformer with it, to monitor oil parameters online, to improve the oil quality during operation and, if necessary, to regenerate such oil when its acid number exceeds the value of 0.2 mg KOH/g.
Oil purification in the electric train traction transformer
The task of processing the oil before filling the traction transformer with it and periodical oil purification during transformer functioning is solved with the use of the CMM series machines and, in particular, the CMM-600CF model, which was manufactured on a special order from the German railway operator Deutsche Bahn.
The CMM-600CF transformer oil purification machine is compact and mounted on a wheeled platform, which allows you to move it easily from one carriage to another inside the locomotive depot. CMM-600CF has two hose winding coils for the convenience of the connection machine to the traction transformer.
Complex traction transformer oil purification includes multi-stage filtration, dehydrating, and degassing with an output of 600 liters per hour. The quality of the oil at the machine outlet corresponds to the 16/13 purity class according to the ISO 4406 standard.
To drain the used oil from the traction transformer and fill it with new transformer oil, two tanks for used oil and for new oil with a volume of 200 liters each are provided in the machine design.
Traction transformer monitoring system
The need to purify oil is determined with the use of the TOR-5 online monitoring system, which is installed next to the traction transformer. TOR-5 measures and calculates important transformer parameters in real-time, in particular, the humidity and quality factor of the transformer oil. The TOR-5 system transfers the abovementioned parameters to a special web application, where it is determined to which range of values this or that parameter belongs – “excellent condition”, “condition needs attention” or “unsatisfactory condition”. The timelines for transformer oil purification with the use of the CMM-600CF machine are determined by the dynamics of oil parameters changes.
Oil regeneration in the electric train traction transformer
When the oil acid number reaches a value of 0.2 mg KOH/g, GlobeCore recommends regenerating the oil of traction transformers with the use of CMM-R machines. The oil is pumped through a special sorbent in these machines. All oil decomposition and aging products are absorbed into sorbent granules. As a result, the parameters of the purified oil at the machine outlet correspond to the parameters of new oils, so purified oil can be reused with traction transformers.
Thus the use of complex GlobeCore technologies makes it possible to maintain traction transformers of the electric trains and electric locomotives promptly and timely. Due to this the reliability of transformers functioning is increased, the safety of passengers is improved and the continuity of railway traffic is ensured.