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Zhejiang ERG Technology Joint Stock Co.,Ltd

Mobile: 86-18257346462

Tel: 86-576-83200088


Contacts: Wu Nick/Bella Cheng

Add: 135 Haisha Road, Shaliu Economic DevelopmentZone, Sanmen County, Zhejiang, P.R.China

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Failure Analysis Of Main Transformer Oil Flow Relay
- Jul 03, 2017 -

After the production were found oil flow relay pointer has a more serious jitter phenomenon. The initial operation of two or three months, did not find other anomalies. But with the extension of the running time gradually appeared in the oil relay contacts often poor contact, resulting in frequent cooler frequent cast, retreat phenomenon, easily lead to submersible pump motor and fan motor burned. More serious is in March 2000, No. 1 main transformer third group cooler oil flow relay tubing parts all shake off, there are four M6 × 20 screw and its anti-loose elastic pad was shiny The tubing was washed away.

Although the main transformer is still running on the 1st, but these a few screws and gasket to the main transformer on the 1st of the safe operation caused a great hidden dangers. This phenomenon has brought a warning, immediately on the two main transformer all the oil relay for a careful inspection. The results of the inspection were surprising: the shafts and bearings of all the relay baffles were severely worn, and the most severe shaft was worn away by 1/4, and the bearing was ground into an oval hole with its long and short axis Ratio of 1.5 to 2, the bearing material for the copper or aluminum alloy, the ground metal powder was rushed into the transformer, which gives the safe operation of the transformer caused a great threat.

Why the two main transformer oil flow relay in the operation of the pointer will be jitter and other transformers do not have this phenomenon? Power plant made the following investigation and analysis:

Two main transformer with the submersible pump for the Hunan Yuejin Machinery Plant production 4B135-7 / 4V disc motor transformer submersible pump, power 4kW, speed of 1380r / min, head for the 7m, flow of 135m3 / h, The oil flow relay is YJ-150/135, which has a nominal diameter of 150mm, a flow rate of 135m 3 / h, an action oil flow of 101 + 10%, and an oil flow rate of 75 + 10%. The rated flow of the submersible pump and the flow of the oil flow relay are matched. Check the oil flow relay in addition to wear, the other anomalies were not found, and the relay wear is caused by the relay moving board jitter. There is no reason to doubt the nameplate of the two manufacturers, then where is the title?

Relay and pump manufacturers nameplate value should be tested, the transformer factory with the diameter of the joint is also 150mm, from the transformer factory to understand the transformer factory did not cooler and transformer body connection test, will not be What is the problem on the pipeline?

Oil pump outlet cross section: 100mm × 100mm = 10000mm2,

Cross-sectional area of the joint: LR 2 = 3.14 × (150/2) 2 = 3.14 × 75 2 = 17662.5 mm 2

(V) = flow rate (Q) ÷ cross section (S) = 135 m 3 / h / 1000 mm 2 = 3.75 m / s,

(V) = flow rate (Q) ÷ cross section (S) = m 3 / h / (3600 s1217662.5 mm 2 = 2.1 m / s

The flow rate of the oil pump outlet oil is 1.78 times, and the oil pump outlet is only 300mm from the oil flow relay plate. The flow rate of the oil pump outlet can not be reduced to the theoretical flow velocity calculation in the joint, Force only with the flow rate, and flow does not matter.

The actual flow rate of the position where the moving plate of the relay is located is greater than the rated flow rate required by the oil flow relay. This is the oil flow relay jitter in the main reason. How to solve it? As the transformer and the cooler has been installed between the positioning, it is impossible to increase the oil pump outlet and oil flow between the relay, which can only play on the oil relay idea, think of a way.

The working principle is: the oil pump after the start of the pipeline to produce oil flow, when the oil flow reaches a certain value (action oil flow), the relay within the moving plate rotation, through the magnetic force to synchronize the instructions, signal contact connected, issued a normal signal. When the oil quantity is reduced to a certain value (return oil flow), the moving plate returns and sends a fault signal. The relay plate can only be fixed in one position (ie, the needle is stationary) when the momentum of the oil on the moving plate is balanced with the reaction force of the damping spring.