Maintenance After an Electrical System Event Has Occurred

DANGER

Hazard of Electric Shock, Explosion, or Arc Flash Apply appropriate personal protective equipment (PPE) and follow safe electrical work practices. See NFPA 70E, NOM-029-STPS-2011, or CSA Z462. This equipment must only be installed and serviced by qualified electrical personnel. Turn off all power supplying this equipment before working on or inside equipment. Always use a properly rated voltage sensing device to confirm power is off. Replace all devices, doors, and covers before turning on power to this equipment. Failure to follow these instructions will result in death or serious injury.

Excessive currents occurring during a short circuit or arcing event may result in structure, component, bus or conductor damage. This damage is caused by mechanical distortion, thermal damage, metal deposits, or smoke from the event. Locate and correct the cause of the event. Inspect all equipment and make any necessary repairs or replacements before putting the equipment into service again. Make sure all replacement parts are rated properly and are suitable for the application. If in doubt, consult your Schneider Electric field sales representative.

After any unusual electrical system event, perform all maintenance procedures, starting in Section 6—Maintaining the MCC and continuing to Insulation Test. Also perform the following procedures after an event:

1. If the event occurred downstream from the MCC, perform appropriate maintenance on all equipment involved.

2. Examine the enclosure. External evidence of enclosure damage usually indicates damage within. Extensive damage requires replacement of the enclosure parts and the enclosed equipment.

3. Replace any parts that are damaged or deformed. Pay particular attention to door hinges and door closing hardware. Inspect the area around any damaged units (both inside and out) for displaced parts from the damaged unit. See Inspecting the Enclosure.

4. Examine bus bars and incoming line compartments; tighten all electrical connections to their proper torques. (Bus Connection Torque Values and Typical Bus Connection Points show typical bus connection points and torque values.) Replace any deformed bus bars or connectors, as well as any showing signs of arcing damage. Inspect all insulators for cracks or burn marks; replace any displaying these characteristics.

   Bus Connection Torque Values

   Bolted Connection Location	Torque Range
   Horizontal bus (all locations)	68–70 lb-ft (92.29–94.54 N•m)
   Horizontal ground bus (all locations)	5–6 lb-ft (6.75–8.44 N•m)
   Splice bars—0.375 in. diameter bolts	31–32 lb-ft (41.64–43.33 N•m)
   Splice bars—0.5 in. diameter bolts	68–70 lb-ft (92.29–94.54 N•m)

   Typical Bus Connection Points
   Typical Top-Located 600 A or 800 A Main Lug Compartment
   Typical Splice Bar Connection	Typical Horizontal Bus Connection

5. If the event occurred between an upstream protection device and the section containing an ArcBlok main device, inspect line-side connections within the ArcBlok and the line-side isolation cable vault. Inspect the interior, looking for evidence of an event, including burn marks and damaged parts. Inspect the front covers, overlapping seals, dampers, springs, and gasket material in and around the vault (Inspection Points After an Event). Replace any parts that are damaged or deformed. If there is evidence of damage in ArcBlok components such as the interphase barriers or phase-line lug connectors, contact Schneider Electric Services before returning the equipment to service.

   Inspection Points After an Event

   

6. Follow maintenance procedures for control units. Begin with Maintaining the Control Unit, and continue to Insulation Test. Also perform the steps listed below:

   Operating Door Interlock Defeat Mechanism

   

   1. Examine the disconnect means for evidence of possible damage. Ensure that the operator mechanism properly turns the disconnect on and off. Exercise the push-to-trip feature on circuit breakers. Make sure that the operator mechanism properly resets the circuit breaker.

   2. Check that the door interlock keeps the unit door from opening while the disconnect is in the on position.

      NOTE: If the unit door must be opened while the unit is energized, only authorized personnel may operate an interlock defeat mechanism (see Operating Door Interlock Defeat Mechanism).

   3. Inspect the motor starters for damage. Replace contacts and contact springs if the contacts are welded or show heat damage. If deterioration extends beyond the contacts, replace the entire contactor or starter.

   4. Replace the complete overload relay if the thermal units are burned out, or if any indications of arcing or burning are present on the relay.

   5. Inspect all fuses and fuse clips. Replace all fuses in a set, even if only one or two are open-circuited.

   6. Check all conductors and other devices within the units for signs of damage.

7. Complete an insulation test (see Insulation Test) before placing the MCC back into service.

8. Complete the Pre-operation Checklist.

9. Re-energize the equipment. See Energizing the MCC.