MAINTENANCE AND REPAIR

NEPSI provides field technicians and engineers for preventive maintenance and repair of new and existing capacitor banks and harmonic filter banks. Because NEPSI designs, engineers, and manufacturers medium voltage harmonic filter and capacitor banks, we have the expertise and knowledge required to repair, maintain, or upgrade virtually any bank, no matter who the manufacturer and degree of complexity.


Standard Maintenance Checklist

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Enclosure Exterior

• Ensure enclosure is receiving adequate ventilation. Check to see if filters are clean and airflow is not restricted. Replace filters and remove obstacles as required.
• Ensure enclosure, enclosure doors, louvers, and rodent guards are adequate to prevent entry of liquids, insects, and rodents. Clean and correct as required.
• Inspect operation and adjustment of key interlock systems to determine if security features are working properly. Correct deficiencies.
• Examine enclosure for corrosion and paint adherence. Repaint scratched or marred exterior surfaces to closely match original finish, as required.
• Examine warning signs and placards. If not legible, replace.
• Clean all enclosure windows.

Enclosure Interior

• Remove accumulated dust and dirt.
• Remove insects, nests, or animal material. Inspect for condensation. Clean and inspect strip heaters and check thermostats.
• Check proper operation of ventilation equipment (fans) and thermostats. Correct as required.
• Examine enclosure for corrosion and paint adherence. Repaint scratched or marred exterior surfaces to closely match original finish, as required.
• Examine warning signs and placards. If not legible, replace.
• Clean all enclosure windows.

Bus Bar & Wiring

• Inspect for loose bus bar connections and discoloration. Tighten as required.
• Inspect for proper phase to phase and phase to ground clearance.
• Remove excess surface oxides from aluminum connectors.
• Inspect control wire connections, tighten as required.
• Inspect wire insulation for cuts, breakdown, or burns. Replace as required.

Component Inspection Checklist

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Capacitors

• Check for physical damage, leaks, bulges, or discoloration. Replace as required.
• Clean capacitor case, insulation bushings, and any connectors that are dirty or corroded.
• Check each capacitor for capacitive reactance by applying 120 volts to each phase and measuring corresponding current. Verify with specification.
• Confirm kVar, voltage, and BIL rating for each capacitor. Verify with specification.
• Verify internal discharge resistors are working properly. Replace cells as required.

Insulators

• Check for cracks, chips, and signs of arc tracking. Replace as required.
• Clean insulators and barriers.
• Check all mounting hardware, tighten as required.

Fuses

• Check all capacitor fuses, control fuses, and PT fuses for blown fuses. Replace as required.
• Check all mounting hardware, tighten as required.
• Confirm proper fuse rating. Verify with specification.
• Check functioning of neutral unbalance sensor.
• Clean contact area of fuses and fuse holders.

Controls

• Perform several manual switching operations of each capacitor stage to ensure equipment is in proper working order.
• Check all indicator lights to ensure proper functioning. Replace lights as required.
• Check controller for proper functionality to specification.
• Check for physical damage and proper operation of ammeters and voltmeters.
• Check that blown fuse detection system is working properly. Correct as required.
• Check that all alarms and indicators are per specification.

Air Disconnect Switch

• Check torque on all bolts. Tighten as required.
• Apply contact grease as required.
• Check chains for proper tension.
• Check for proper operation (perform 10 full operations).
• Check that all contact are free of pitting and corrosion.
• Check that all moving parts are free of binding and libricate moveable parts.

Vacuum Switches

• Check for proper rating.
• Check for physical damage and leaks.
• Check torque on all bolts. Tighten as required.
• Check for continuity when closed and discontinuity when opened.
• Physically check contacts on oil switches, clean as required.
• Perform high pot testing on vacuum bottles.

Harmonic Filter Reactors

• Confirm nameplate rating.
• Check torque on all bolts. Tighten as required.
• Check for physical damage.
• Measure inductance of each reactor phase by applying 35 volts across each reactor and measuring corresponding current.
• Calculate tuning point of each phase by using capacitive and inductive reactance.

Surge Arresters

• Check for physical damage. Replace as required.
• Check torque on all bolts. Tighten as required.
• Check for proper rating of surge arrester.

High Pot/Insulation Test

• Check phase to ground insulation level. Perform high pot test at IEEE recommended voltage levels, with application of voltage for 15 minutes. Note: If possible, cable supply bank should be connected during this test. This can only be accomplished if there is an upstream disconnect switch that can be opened. If not possible, the high pot test will be performed on the capacitor bank alone.