1 status of UPS power supply system in front-end equipment room
Due to the nature of broadcasters and television stations and the 24-hour power supply of the TV center, the station has applied to the Power Supply Bureau for dual-channel power supply (different substation power supply), that is, the power center power distribution room uses two 10kV high-voltage inlets. , And equipped with two transformers, in this way, two transformers (rated output voltage 380V) divided into the front-end power distribution box, respectively to two 40kWUPS power supply, two UPS are three in three out, one UPS is responsible to All devices of the digital TV platform are powered, and the other is responsible for supplying power to other equipment in the equipment room (except for lighting and air conditioning). The UPS load does not exceed 60%.
2UPS Working Principles and Potential Risks 2.1 How UPS Works
As shown in Fig. 1, when the utility power is normal, both the rectifier and the inverter work, and at the same time, the load and the battery float are supplied with power. When the utility power is interrupted, the rectifier stops working. The battery supplies power to the load via the inverter to achieve uninterrupted power supply. If the battery fails or the battery energy is exhausted, the UPS transfers to the bypass power supply.
2.2 Potential Risks
Firstly, two three-input and three-out UPS units in the Zhuhai front-end equipment room belong to the single-unit work. No matter which one is faulty, it will directly affect the output power supply and the reliability is low.
Second, because the relationship between the working principle of UPS and the input mode of mains was not fully understood in the early stage, there was no isolation between the UPS main circuit input and the bypass input. Therefore, both inputs were introduced by the same AC distribution panel. The inside of the machine is connected for processing. As shown in Figure 1, the power supply method has serious risks. The bypass and the main circuit are the same input power supply. When the main circuit input power is abnormal and the battery is faulty or the battery energy is exhausted, the output is Power supply will be interrupted.
Third, the status quo of the two UPSs has prevented the UPS from being overhauled and replaced safely and reliably. When the UPS needs to be repaired or replaced, it is generally transferred to the internal maintenance bypass of the UPS. Actually, the incoming and outgoing power passes through the UPS. The maintenance personnel still has the power to overhaul. If there is slight inadvertence, it may cause personnel and equipment accidents.
3 UPS transformation program
In order to standardize the distribution system of UPS, eliminate the above-mentioned safety hazards and improve the safety of the power supply system, the input power distribution transformation of the UPS shall be implemented. Considering Zhuhai Radio's front-end equipment room space and bearing capacity are limited, it is impossible to use a two-machine parallel method to improve the reliability of the UPS power supply system. Therefore, the following simple retrofit scheme is proposed:
3.1 Remove the internal short wiring
After the transformation of the wiring principle shown in Figure 2, an additional three-phase input cable, as the main input, plus an input switch, as the main input switch, the original three-phase input cable as a bypass input. It can be seen that the modified connection mode cuts off the short circuit between the main and bypass inputs, thus greatly improving the reliability of the system.
3.2 Add UPS bypass power cabinet
In order to eliminate the potential safety hazards of working personnel when repairing and replacing the UPS, a simple and reliable method is to add a bypass power cabinet to the UPS, as shown in Figure 3.
The normal operation mode of the bypass power cabinet is that K3 is disconnected, K1, K2, K4 are closed, and the load is supplied by the UPS. When the UPS is overhauled or replaced for any reason, first turn the UPS into the maintenance bypass, close the Q3, disconnect the Q4, Q1 and battery pack switches, and disconnect the main power switch K1 of the upper level of Q1, and close the K3. The load is supplied by the bypass cabinet. The UPS has been completely powered off and can be safely repaired or replaced. After the work is completed, operate in the opposite direction as described above to restore the normal operation of the UPS.
After the UPS power supply system of the Zhuhai front-end room was transformed and implemented in accordance with the above plan, it became more standardized and reasonable. It not only resolved the output interruption caused by the battery failure when the power supply to the main circuit was lost, but also improved the staff's overhaul and replacement of the UPS. safety.
4Usage and maintenance of UPS
At present, most UPSs use sealed lead-acid batteries that do not require maintenance. On the surface, such batteries do not require maintenance. However, this is not the case. According to statistics, the proportion of UPS failures due to battery failure is about 30%. Therefore, it is important to properly use and maintain the battery.
4.1 UPS should not be full or excessive light load
Each UPS is marked with rated power. Under normal circumstances, online UPS should not exceed the rated power of 80% of the load, therefore, it is best not to use it in accordance with the rated power of the UPS, long-term at full load, will cause UPS inverter The overheating of the rectifier and rectifier affects the service life of the UPS. Similarly, it is not advisable to operate the UPS under excessively light load condition. Because the UPS is too light, it may cause deep discharge of the battery during a power outage, and it will also significantly reduce the service life of the battery.
4.2 Keep UPS batteries away from heat
The influence of ambient temperature on UPS is very important. Studies have found that it is advisable to operate the battery in the UPS at a temperature of 10°C to 25°C. When the ambient temperature rises, the inherent “storage life†of the battery will gradually decrease. For example, the expected life of the battery is 5 years when the ambient temperature is 20° C.-25° C., and the service life is only 2.5 when the temperature rises to 35° C. Years, but the temperature rises to 45 °C when its life is only 1 to 1.5 years. Therefore, UPS should avoid heat sources such as heating and avoid direct sunlight. The ambient temperature should not be too low. If the temperature is too low (for example, less than 5°C), the amount of electricity discharged by the battery will be greatly reduced.
In addition, it is also important to keep the UPS's working environment clean. When the UPS is operating in a turbid environment, harmful dust floating in the air once it enters the UPS will cause corrosion or short circuit to its internal components, thus affecting the normal operation of the UPS. In severe cases, the UPS may be damaged.
4.3 UPS needs regular maintenance
Under normal circumstances, the UPS must be checked once every 4 to 6 months to measure the terminal voltage and internal resistance of the battery. If the voltage of a single battery is lower than its minimum threshold voltage or if the internal resistance of the battery is greater than 80mΩ, charge equalization or replace the battery. If there is no power outage for a long period of time, the power supply needs to be periodically powered down for a period of time to allow the UPS to discharge the load. The best discharge rate is between 30% and 50%. This will allow the UPS to operate in the inverter state for a period of time. Activates the battery's charge and discharge capabilities and extends its service life.
Due to the nature of broadcasters and television stations and the 24-hour power supply of the TV center, the station has applied to the Power Supply Bureau for dual-channel power supply (different substation power supply), that is, the power center power distribution room uses two 10kV high-voltage inlets. , And equipped with two transformers, in this way, two transformers (rated output voltage 380V) divided into the front-end power distribution box, respectively to two 40kWUPS power supply, two UPS are three in three out, one UPS is responsible to All devices of the digital TV platform are powered, and the other is responsible for supplying power to other equipment in the equipment room (except for lighting and air conditioning). The UPS load does not exceed 60%.
2UPS Working Principles and Potential Risks 2.1 How UPS Works
As shown in Fig. 1, when the utility power is normal, both the rectifier and the inverter work, and at the same time, the load and the battery float are supplied with power. When the utility power is interrupted, the rectifier stops working. The battery supplies power to the load via the inverter to achieve uninterrupted power supply. If the battery fails or the battery energy is exhausted, the UPS transfers to the bypass power supply.
2.2 Potential Risks
Firstly, two three-input and three-out UPS units in the Zhuhai front-end equipment room belong to the single-unit work. No matter which one is faulty, it will directly affect the output power supply and the reliability is low.
Second, because the relationship between the working principle of UPS and the input mode of mains was not fully understood in the early stage, there was no isolation between the UPS main circuit input and the bypass input. Therefore, both inputs were introduced by the same AC distribution panel. The inside of the machine is connected for processing. As shown in Figure 1, the power supply method has serious risks. The bypass and the main circuit are the same input power supply. When the main circuit input power is abnormal and the battery is faulty or the battery energy is exhausted, the output is Power supply will be interrupted.
Third, the status quo of the two UPSs has prevented the UPS from being overhauled and replaced safely and reliably. When the UPS needs to be repaired or replaced, it is generally transferred to the internal maintenance bypass of the UPS. Actually, the incoming and outgoing power passes through the UPS. The maintenance personnel still has the power to overhaul. If there is slight inadvertence, it may cause personnel and equipment accidents.
3 UPS transformation program
In order to standardize the distribution system of UPS, eliminate the above-mentioned safety hazards and improve the safety of the power supply system, the input power distribution transformation of the UPS shall be implemented. Considering Zhuhai Radio's front-end equipment room space and bearing capacity are limited, it is impossible to use a two-machine parallel method to improve the reliability of the UPS power supply system. Therefore, the following simple retrofit scheme is proposed:
3.1 Remove the internal short wiring
After the transformation of the wiring principle shown in Figure 2, an additional three-phase input cable, as the main input, plus an input switch, as the main input switch, the original three-phase input cable as a bypass input. It can be seen that the modified connection mode cuts off the short circuit between the main and bypass inputs, thus greatly improving the reliability of the system.
3.2 Add UPS bypass power cabinet
In order to eliminate the potential safety hazards of working personnel when repairing and replacing the UPS, a simple and reliable method is to add a bypass power cabinet to the UPS, as shown in Figure 3.
The normal operation mode of the bypass power cabinet is that K3 is disconnected, K1, K2, K4 are closed, and the load is supplied by the UPS. When the UPS is overhauled or replaced for any reason, first turn the UPS into the maintenance bypass, close the Q3, disconnect the Q4, Q1 and battery pack switches, and disconnect the main power switch K1 of the upper level of Q1, and close the K3. The load is supplied by the bypass cabinet. The UPS has been completely powered off and can be safely repaired or replaced. After the work is completed, operate in the opposite direction as described above to restore the normal operation of the UPS.
After the UPS power supply system of the Zhuhai front-end room was transformed and implemented in accordance with the above plan, it became more standardized and reasonable. It not only resolved the output interruption caused by the battery failure when the power supply to the main circuit was lost, but also improved the staff's overhaul and replacement of the UPS. safety.
4Usage and maintenance of UPS
At present, most UPSs use sealed lead-acid batteries that do not require maintenance. On the surface, such batteries do not require maintenance. However, this is not the case. According to statistics, the proportion of UPS failures due to battery failure is about 30%. Therefore, it is important to properly use and maintain the battery.
4.1 UPS should not be full or excessive light load
Each UPS is marked with rated power. Under normal circumstances, online UPS should not exceed the rated power of 80% of the load, therefore, it is best not to use it in accordance with the rated power of the UPS, long-term at full load, will cause UPS inverter The overheating of the rectifier and rectifier affects the service life of the UPS. Similarly, it is not advisable to operate the UPS under excessively light load condition. Because the UPS is too light, it may cause deep discharge of the battery during a power outage, and it will also significantly reduce the service life of the battery.
4.2 Keep UPS batteries away from heat
The influence of ambient temperature on UPS is very important. Studies have found that it is advisable to operate the battery in the UPS at a temperature of 10°C to 25°C. When the ambient temperature rises, the inherent “storage life†of the battery will gradually decrease. For example, the expected life of the battery is 5 years when the ambient temperature is 20° C.-25° C., and the service life is only 2.5 when the temperature rises to 35° C. Years, but the temperature rises to 45 °C when its life is only 1 to 1.5 years. Therefore, UPS should avoid heat sources such as heating and avoid direct sunlight. The ambient temperature should not be too low. If the temperature is too low (for example, less than 5°C), the amount of electricity discharged by the battery will be greatly reduced.
In addition, it is also important to keep the UPS's working environment clean. When the UPS is operating in a turbid environment, harmful dust floating in the air once it enters the UPS will cause corrosion or short circuit to its internal components, thus affecting the normal operation of the UPS. In severe cases, the UPS may be damaged.
4.3 UPS needs regular maintenance
Under normal circumstances, the UPS must be checked once every 4 to 6 months to measure the terminal voltage and internal resistance of the battery. If the voltage of a single battery is lower than its minimum threshold voltage or if the internal resistance of the battery is greater than 80mΩ, charge equalization or replace the battery. If there is no power outage for a long period of time, the power supply needs to be periodically powered down for a period of time to allow the UPS to discharge the load. The best discharge rate is between 30% and 50%. This will allow the UPS to operate in the inverter state for a period of time. Activates the battery's charge and discharge capabilities and extends its service life.
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