1. Introduction
1.1 Purpose and Intended Users
1.2 Scope
2. Definitions
3. Safety Measures
4. PM Instruments
5. Recommended Schedule of Minor PM
5.1 UPS Equipment
5.2 Batteries
5.3 Operating Conditions
6. Recommended Schedule of Major PM
6.1 UPS Equipment
6.2 Batteries
6.3 Operating Conditions
7. Investigation of Disturbances
Appendix A – UPS Minor PM Checklist
Appendix B – UPS Major PM Checklist
Appendix C – UPS PM Battery Data
Guidelines for Minor and Major UPS System Preventive Maintenance
1. Introduction UPS System Preventive Maintenance
1.1 Purpose and Intended Users
The purpose of this article is to provide guidelines to trained maintenance guy to perform minor and major preventive maintenance on Uninterruptible Power Supply (UPS) equipment and associated batteries. The intended users may include trained engineers and technicians in the field of UPS and DC Systems, or people who are involved in repair of power electronics based systems.
1.2 Scope
This article is designed for time based preventive maintenance tasks during UPS system operation for minor maintenance and UPS system shutdown for major maintenance.
2 Definitions UPS System Preventive Maintenance
Synchronize date and time on modules: have all UPS modules and including bypass to display identical date
UPS system: static uninterruptible power supply, double conversion technology, including backup batteries
ac: alternate current
dc: direct current
Electrical measurement: Electrical output at specified point
UPS rectifier/charger: Power electronics based device that converts mains ac to dc
UPS inverter: power electronics based device that converts dc from UPS rectifier/charger to ac
3. Safety Measures During UPS System Preventive Maintenance
UPS equipment and batteries contain high voltage, thus only qualified/certified servicemen should attempt preventive maintenance and/or repair. Nonetheless, end users may provide PM support such as replacement of air filters when dirty and insurance of meeting specified environment conditions. Hence, make sure that he following safety equipment is provided near stationary batteries during UPS PM:
3.1 Safety face shields and goggles
3.2 Safety aprons
3.3 Acid resistant rubber gloves
3.4 Safety shoes
3.5 Eye washing facilities
3.6 Neutralizing agent:
3.6.1 To neutralize lead acid battery: Mix 0.1 kg bicarbonate of soda to one liter of water.
3.6.2 To neutralize nickel cadmium battery spillage: Mix 50 grams boric acid solution to one liter of water.
3.6.3 Or use other suitable neutralizing agent recommended by the manufacturer for acid electrolyte spillage or the manufacturer of alkaline electrolyte spillage, whichever applicable. In addition to the above, apply the following safety measures during the complete UPS PM process:
3.7 Use adequately insulated tools.
3.8 Be cautious when working on UPS and batteries since they represent electric shock hazard.
3.9 Prohibit smoking and open flames, and avoid arcing in the immediate vicinity of batteries.
3.10 Ensure the UPS and battery rooms’ ventilation systems are operational and rooms’ temperature is maintained at 25°C.
3.11 Ensure unobstructed egress from the battery room area.
3.12 Do not wear metallic object such as jewelry.
3.13 Ensure that all connections to load test equipment include short-circuit protection.
3.14 Neutralize static buildup before working on a battery by having personnel contact nearest effectively grounded surface.
3.15 Make sure that all vents of the cells/batteries are closed tightly before starting any battery testing process.
3.16 Make sure that all battery inter-cell connectors and terminals are closed tightly before starting any battery testing process.
4. UPS Preventive Maintenance Instruments
4.1 True RMS multi-meter: range up to 600 Vac, 600 Vdc
4.2 Clamp meter: range up to 4 kA
4.3 Industrial air extractor/vacuum cleaner
4.4 Thermo vision inspection tool: higher temperature reading than similar connections around it indicates a loose connection. This theory suits both ac and dc electrical connections.
4.5 Tools: insulated where applicable
a. Screwdriver set
b. Hex lobe bits set
c. Spanner set
d. Hydrometer
e. Thermometer
f. PVC electrical insulation tape
4.6 Battery safety equipment: see Section 3 above
a. Apron
b. Goggles
c. Face shield
d. Rubber boots
e. Acid resistant gloves
4.7 Load bank: Required during major maintenance only
– Rate current to match UPS rated kVA
5. Recommended Schedule of Minor UPS Preventive Maintenance
Perform quarterly – UPS System in operation.
5.1 UPS Equipment
1. Adjust and synchronize ‘date’ and ‘time’ display on all modules
2. Check physical status of enclosure(s)
3. Visual check on the internal components
4. Check operability of cooling fans; check unusual noise
5. Check and verify operability of displays, meters and signalization
6. Visual checks on electrical connections; use a thermo vision inspection tool where applicable
a. main power cables
b. output feeders
c. ground connections
7. Make electrical measurements; compare with normal operation ref values
a. Inverter output: kVALoad, PFLoad, voltage(s), current(s), freq. & %Load
b. Primary and alternative power supplies: kVAInput, PFInput, voltage(s), freq. and current(s)
c. dc float charge voltage and current (measure), and number of battery cells
8. Examine status of ac and dc filter capacitors every 7 years utmost: replace if capacitance is out of the +/-10% tolerance, and/or physically damaged and/or leaking
9. External cleaning: Enclosures and dust filters
– Do not blow air directly to PCBs
– Use air extractor / vacuum cleaner
5.2 Batteries
Do quarterly maintenance.
5.3 Operating Conditions
UPS and Battery Rooms – Have particular attention to:
1. Environmental conditions: UPS and battery rooms’ temperature and relative humidity
2. Air exchanges: UPS and battery rooms ventilation and exhaust fans
– Check for unusual noise and odor
3. Safety shower and eyewash (if applicable): Check operability and water temperature.
6 Recommended Schedule of Major UPS Preventive Maintenance
Perform annually – UPS system shutdown.
6.1 UPS Equipment
1. Adjust and synchronize ‘date’ and ‘time’ display on all modules
2. Check physical status of enclosure(s)
3. Visual check on the internal components
4. Verify all PCBs are securely mounted to their standoffs: Visually check PCBs integrity. Ensure control harnesses to and from each PCB are securely connected and neatly routed.
5. Visual checks on electrical connections; use a thermo vision inspection tool where applicable: main power cables, output feeders and ground connections
6. Check operability of cooling fans; check for unusual noise
7. Check and verify operability of displays, meters and signalization
8. Make electrical measurements; compare with normal operation ref values
a. Inverter output: kVALoad, PFLoad, voltage(s), current(s), freq. & %Load
b. Primary and alternative power supplies: kVAInput, PFInput, voltage(s), freq. and current(s)
c. dc float charge voltage and current (measure), and number of battery cells
9. Examine status of ac and dc filter capacitors every 7 years utmost: replace if capacitance is out of the +/-10% tolerance, and/or physically damaged and/or leaking
10. External cleaning – enclosures and dust filters: Do not blow air directly to PCBs
– Use air extractor / vacuum cleaner
11. Verify load transfer between inverter output and bypass line
12. Check operability of manual bypass
13. Simulate mains failures and emergencies
6.2 Batteries
Do annual maintenance.
6.3 Operating Conditions
UPS and Battery Rooms – Have particular attention to:
1. Environmental conditions: UPS and battery rooms’ temperature and relative humidity
2. Air exchanges: UPS and battery rooms ventilation and exhaust fans
3. Check for unusual noise and odor
4. Safety shower and eyewash (if applicable): Check operability and water temperature.
7. Investigation of UPS Disturbances
7.1 Ensure that a copy of all reports has been printed, stabled together and left with the UPS unit for future reference.
7.2 Do not clear the event history, as such data can be useful to servicemen after PM.
7.3 Review collected data and inspection findings against the values/conditions recorded during the commissioning phase.
7.4 Discuss any abnormality with the vendor(s).
7.5 Do immediate corrective action(s) if deemed necessary.