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What are the reasons for the failure of high speed 6cylinder diesel engine in the data center?

Views:92     Author:Site Editor     Publish Time: 2021-02-18      Origin:Site

What are the reasons for the failure of high speed 6cylinder diesel engine in the data center?

What are the reasons for the failure of high speed 6cylinder diesel engine in the data center?

 

On April 22, 2016, all equipment in the computer room were powered off and the system was down due to power supply interruption in the process of UPS upgrading of a company's Beijing data center. The core, bank card, counter, payment, online banking and mobile banking businesses of 73 rural banks were all interrupted, involving 12 provinces across the country. In addition, some servers are damaged and the maximum recovery time of banking business is 7 hours and 32 minutes. During this period, three high speed 6cylinder diesel engines have been used for parallel operation to supply power for UPS.

 

Cause description

 

In order to ensure the normal power supply of external power supply, the external power supply is changed to diesel generator to supply power to UPS and the 4stroke 6cylinder diesel engine with false load test has been done before. During the upgrade process, the two old ups were switched to bypass after 50 minutes of operation due to high load (up to 90% of capacity). At this time, the generator directly supplies power to IT equipment. 12 minutes later, the three diesel generators successively gave "loss of excitation" alarm and stopped operation, resulting in power failure of all equipment in the machine room and system outage.

 

Accident analysis

 

Why does UPS switch to bypass due to high load?

 

1) When the power factor is 0.95, the rated capacity of UPS is 400KVA and the terminal load is 710kva. The UPS is overloaded by 15.6% when the two UPS are parallel.

2) The above data reflect that the UPS has been overloaded. Therefore, it's only a matter of time when the old UPS switches to bypass due to too high load. The time of UPS overload operation and the time of switching to bypass cannot be determined, so it is not advisable for operation and maintenance personnel to overload the old UPS. The UPS update operation should be carried out during the low IT load period to avoid this risk.

3) With the increase of UPS usage and operation time, the performance of UPS will also decline. It is not wise to judge the UPS performance only based on test data. It is difficult to determine the overload capacity of the old UPS without professional test.

 

Why does the diesel generator set have "loss of excitation" alarm and finally quit power supply?

 

1) For the 4stroke electric starting diesel engine, the inductive load has "demagnetization effect" and the capacitive load has "demagnetization effect". At this time, the load in the data center is mainly capacitive, so this is not the main factor that causes the "loss of excitation" alarm and finally "de excitation" to exit the power supply.


2) The data center equipment can produce harmonics including switching power supply of control system, rectifier of lighting system, frequency converter, IT equipment, EPS power supply and UPS power supply. It is necessary for the power supply and distribution system in the data center to suppress harmonics.


3) Harmonic will cause electromagnetic torque ripple and serious mechanical vibration of generator, which will affect the life of powerful 12cylinder diesel engine.


4) In general, the internal resistance of a large power grid can be ignored when it is regarded as an infinite power source. The harmonic current produced by the equipment has little influence on the power grid voltage. When the harmonic current flows through the stator winding of the motor, the output voltage of the synchronous generator will be distorted greatly. The distorted output voltage will not only interfere with the normal use of the electrical equipment, but also make the excitation system of the high speed 6cylinder diesel engine generator unable to work normally, resulting in more serious consequences.


5) Therefore, the main reason for the "loss of excitation" alarm and the withdrawal of power supply is caused by harmonics. It is the inducement of the accident that the power supply and distribution system harmonics are intensified by the start-up and update UPS.


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