Technical requirements of power system for UPS

Due to the high reliability requirement of power plant, the reliability and service life of ups are very high. Lightning protection requirements are relatively high, generally requires two-level lightning protection.

Reliability requirements:

Due to the high reliability requirement of power plant, the reliability and service life of ups are very high. Lightning protection requirements are relatively high, generally requires two-level lightning protection.

Load type:

Because most of the DCS system load is single-phase load, the single-phase load distribution line is simple and easy to maintain. Therefore, most of the UPS power supply for power plant is small and medium power ups with three-phase input / single-phase input and single-phase output, and the capacity is generally within 60 kVA.

AC input requirements:

Due to the wide fluctuation range of auxiliary power voltage and large harmonic voltage, the input range of UPS is required to be wide. Because the power plant requires AC and DC isolation, the ups input and output must be equipped with isolation transformer. The quality of auxiliary power in general power plant is poor, so there is no high requirement for input THDi of ups.

Bypass requirements:

The static switching switch shall have two working modes, automatic and manual, to realize uninterrupted switching. In order to improve the quality of power supply under bypass operation mode and remove the influence of interference and power fluctuation. Generally, the bypass needs to increase isolation voltage regulator, which mainly plays the role of isolation and voltage stabilization. Generally, it is also necessary to maintain the bypass. When maintaining the ups, it is necessary to completely disconnect the ups cabinet from the power supply system, and the operation of the switch must ensure that the output is not powered off.

DC system:

Because the power plant has a 220 V (187 ~ 253v, rated as 18 12 V batteries) or 110 V (93 ~ 126 V, rated as 9 12 V batteries) DC system; in order to save cost, the DC system is directly used as the DC input of UPS; the power plant has a special DC operation panel to charge the battery; the DC input voltage of UPS is required to be 220 V or more

110V, and does not require the ups to have charging function. The battery pack for normal UPS operation is used alone, and its DC input end has a large noise of reverse irrigation. If the battery is directly integrated into the bus of UPS, the battery pack is used separately,

Ups will produce large electromagnetic interference on the battery, which will affect the normal operation of the DC system seriously. However, the DC input end of the power dedicated UPS is generally required to be equipped with a back filling noise suppressor, such as a check-in diode, so that the impact of ups on the DC bus is minimal.

Communication requirements:

UPS host needs to provide RS-232 and RS-485 interfaces. UPS operation status and main alarm signals should be able to provide passive dry contact. The main operation status and alarm signals generally include:

A) UPS working state: UPS working / battery power supply / bypass power supply;

B) Comprehensive fault signals of various devices;

C) Status of AC incoming circuit breaker / DC switch; auxiliary contact of switch is required.

D) Feeder switch status, generally need to provide switch auxiliary contact and alarm contact.

E) The output voltage, current and frequency of UPS shall be converted into analog signal of 4 ~ 20mA through transmitter, so as to be directly sent into analog quantity sampling system of DCS of power plant.