Monitoring and management method of UPS power supply derating operation state
Downrated operation of UPS: refers to the fact that the actual load capacity of UPS is lower than the rated output capacity. Common reasons include excessive ambient temperature, elevation rise, aging of devices, battery working conditions, abnormal fan heat dissipation, module failure, and redundant module exit. After derating, the maximum output power is allowed to decrease, and if the load remains unchanged, there will be overload risk, which needs monitoring, alarm and operation and maintenance control.
I. Monitoring means for derating operation state
1. UPS local monitoring (local equipment)
Panel/local display screen reads key parameters: rated capacity, currently available output capacity, actual output active/apparent power, derating flag, ambient temperature, internal temperature, altitude setting, and module running status. Many UPS will directly display the "current maximum available power", and compare the nameplate rating to determine whether to downgrade.
Example: 100kVA UPS, this machine shows that the maximum available capacity is 80kVA, indicating that it has been reduced by 20%.
UPS internal status register Intelligent UPS has status bits: temperature derating, altitude derating, module fault derating and rectifier/inverter derating. Read the register through the communication protocol, directly obtain the trigger source of derating, and distinguish whether it is caused by environment or hardware failure.
2. Remote monitoring of communication (mainstream)
Support protocols: Modbus‑RTU/TCP, SNMP and UPS special protocols (such as SDC and Liebert protocols) collect key monitoring indicators:
Basis: rated kVA/kW of UPS, current allowable maximum output capacity, actual output power and load rate.
Environment: internal temperature of cabinet, radiator temperature, inlet air temperature and altitude configuration parameters.
Hardware: online number of power modules, module status, fan speed, rectifier/inverter temperature, battery voltage and current.
Alarm bits: overtemperature derating alarm, module missing derating, altitude derating and device overheating alarm.
Core calculation: actual load ÷ current allowable maximum output capacity = real load rate. You can't just use load ÷ nameplate rating. The nameplate value has become invalid under derating conditions, which is a lot of operation and maintenance errors.
3. Supporting monitoring platform/DCIM data center infrastructure management system
Connect UPS to DCIM to realize:
Continuous recording: rated capacity, real-time available capacity, real load rate and temperature curve;
Set the threshold alarm: when the available capacity is lower than the rated 90%, 80% and other classified alarms;
Correlation trend: temperature rise tracks the decrease of available capacity synchronously, and identifies temperature-type derating;
Event record: record the occurrence time, recovery time and trigger reason of derating, which is used for fault backtracking.
4. Auxiliary external monitoring means
Temperature and humidity sensor: temperature sensors are installed at the air inlet and internal radiator of UPS cabinet to check whether the temperature of UPS machine is accurate; High temperature is the most common cause of derating.
Infrared temperature measurement: periodic inspection, infrared temperature measurement of power module and power device radiator, finding local overheating, and predicting device aging and derating.
Check the field altitude parameters: UPS needs to set altitude parameters in high altitude areas (> 1000 m), and the higher the altitude, the lower the allowable output power; Check whether the internal altitude configuration of UPS matches the actual altitude on site, and the configuration error will cause abnormal derating.
Second, the management measures of UPS derating operation
1. Identify the root cause of derating and deal with it by classification.
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Disposal measures for reasons of derating
If the ambient temperature is too high, clean the filter screen, check the fan, improve the air conditioning in the machine room and reduce the inlet air temperature; The standard operating temperature of UPS is generally 0.40℃, and the higher the temperature, the lower the output capacity.
High altitude derating belongs to the design inherent derating. Recalculate the load and reduce the actual load; If necessary, expand UPS, and the derating cannot be lifted by adjusting the parameters.
The power module is damaged/the offline redundant module fails to exit, which leads to the derating of the whole machine. Replace the failed power module in time and restore the rated capacity of the whole machine.
Power device aging and overheating device performance attenuation, combined with infrared temperature measurement evaluation, choose the opportunity to replace the module
Fan failure and insufficient heat dissipation Replace the failed fan to restore heat dissipation.
Battery-related (some models) battery abnormality will limit the inverter output, and repair the battery pack.
No operation: Do not directly shield the derating protection, and force the full power output, which will trigger the UPS to overheat and shut down, and the device will burn out.
2. Load management
In the derated state, take the current allowable maximum output capacity as the load upper limit, recalculate the load, control the real load rate, and prohibit overload;
If the derating cannot be eliminated in the short term, transfer some non-critical loads in time to reduce the output load of UPS;
Redundant system (N+1): One UPS is derated, so the total available capacity of the whole parallel system should be rechecked to prevent the whole system from being overloaded.
3. Alarm and operation and maintenance system
Configure graded alarms in the monitoring system:
Early warning: in case of derating, but the real load rate is less than 70%, arrange the planned investigation;
Important warning: after derating, the real load rate is greater than 80%, and the risk level rises, which needs to be dealt with immediately;
Emergency alarm: after derating, the load is close to the upper limit of available capacity, and there is a risk of downtime, so the load is urgently reduced.
Regular inspection items:
Read the "currently available output capacity" of UPS, compare the rating of nameplate, and confirm whether there is any hidden derating (some UPS derating may not pop up obvious alarm, but only modify the internal available capacity parameters);
Check the fan, filter screen and air conditioner in the machine room; Check the altitude setting for high altitude stations;
Parallel system: check whether each single machine has derating, so as to avoid single machine derating dragging down the whole system.
4. Special management of parallel UPS system
In parallel system, as long as one UPS is derated, the output capacity of the whole system will decrease.
The monitoring platform needs to collect the available capacity of each single machine, not just the total output;
It is forbidden to only look at the total load rate and ignore the derating of a single unit;
When a parallel unit is derated, isolate the faulty unit if necessary and re-evaluate the power supply capacity of the remaining units.
5. Document and change management
Record the rated capacity of UPS nameplate, the altitude of this machine and the temperature derating curve (refer to UPS manual); The manufacturer's manual will give the maximum output percentage corresponding to different temperatures and altitudes;
Re-check the matching of UPS derating curve and load after the transformation of computer room, air conditioning and relocation to a high altitude location.
Third, common misunderstandings
Only look at the rated capacity of the nameplate to calculate the load rate, ignoring the actual available capacity after derating, resulting in misjudgment of overload risk;
Directly shield the derating alarm and do not investigate the root cause;
In high altitude environment, the inherent derating caused by altitude is ignored and the load configuration is too high;
The parallel scenario only monitors the total output, not the derating status of a single UPS.
