As the computer technology keeps accelerating speed, servers and other important equipment need increasingly higher requirements for power quality, especially the zero-ground voltage of UPS power supply has set a higher standard. In order to guarantee the stable operation of sensitive equipment such as servers, it is particularly important to understand and excel in the zero-ground voltage.
The definition of zero ground voltage
Ground zero voltage refers to the difference in voltage between the ground line (PE) and neutral line (N) of a distribution system. When such a voltage difference lies outside a range, it can result in malfunction or loss of performance of sophisticated devices such as servers. The guaranteed zero ground voltage provided by UPS companies is smaller than a specified value, in fact, it means that their products will not add additional zero ground voltage, that is, if the zero ground voltage on the input side is 0V, the zero ground voltage on the output side should be less than a specified value. But if the user’s power distribution system itself is faulty, such as the zero line current is too large or interphase high order harmonic coupling, it will lead to the rise of the zero ground voltage and affect the normal operation of the equipment.
Method of reducing voltage to zero ground
Optimized neutral line design: Shortening the neutral line length and increasing the cross-sectional area can, in reality, reduce the reactance and consequently reduce the zero-ground voltage. Although the above method involves some operational hindrance, one can consider this while designing the machine room.
Check the grounding resistance: Ensure that the grounding resistance of the grounding body meets the national standard, and check whether the ground cable connector is loose or corroded to reduce the contact resistance.
Balanced three-phase load: For non-isolated dual-conversion pure online UPS, try to balance the three-phase load distribution, which can reduce the zero ground voltage due to load imbalance.
Using an isolation transformer: Installing an isolation transformer on the load side of the UPS source of power and grounding the isolated neutral line is a very effective solution. It not only reduces zero-ground voltage in a very important manner, but it also provides additional security.
Understand the function of power frequency UPS properly: some people wrongly believe that the transformer with power frequency UPS can directly solve the problem of zero ground voltage, but in fact this should include the condition that the bypass is also equipped with an isolation transformer in order to achieve real zero ground voltage isolation.
Briefly, though the above measures are definitely able to reduce the zero-ground voltage to some degree, in the pursuit of ultimate stabilization of the data center, the combination of various methods, especially the implementation of isolation transformers, is one of the most simple and effective methods. Reasonable design and planning not only have the ability to meet high-end server demands for zero-ground voltage, but also can improve the security and reliability of the overall power supply system.