Breaking Unit NIII_Z_1: Check the Condition of the Breaking Unit - MTZ Basic Standard Maintenance Procedures

Safety Instructions

DANGER
HAZARD OF ELECTRIC SHOCK, EXPLOSION, OR ARC FLASH Apply appropriate personal protective equipment (PPE) and follow safe electrical work practices. See NFPA 70E, CSA Z462, NOM 029-STPS, or local equivalent. This equipment must only be installed and serviced by qualified electrical personnel. Unless specified otherwise in the maintenance procedures, all operations (inspection, test, and preventive maintenance) must be carried out with the device, the chassis, and the auxiliary circuits de-energized. Check that the device and the chassis are de-energized on the upstream and downstream terminals. Always use a properly rated voltage sensing device to confirm that the device, the chassis, and the auxiliary circuits are de-energized. Install safety barriers and display a danger sign. During the tests, it is strictly forbidden for anyone to touch the device, the chassis, or the conductors while voltage is applied. Before turning on power to this equipment, check that all connections are made with the correct tightening torque and the device is open (OFF position). Before turning on power to this equipment, put all devices, doors, and covers back in place. Before turning on power to this equipment, beware of potential hazards and carefully inspect the work area for tools and objects that may have been left inside the equipment. Failure to follow these instructions will result in death or serious injury.

DANGER

HAZARD OF ELECTRIC SHOCK, EXPLOSION, OR ARC FLASH

Apply appropriate personal protective equipment (PPE) and follow safe electrical work practices. See NFPA 70E, CSA Z462, NOM 029-STPS, or local equivalent.
This equipment must only be installed and serviced by qualified electrical personnel.
Unless specified otherwise in the maintenance procedures, all operations (inspection, test, and preventive maintenance) must be carried out with the device, the chassis, and the auxiliary circuits de-energized.
Check that the device and the chassis are de-energized on the upstream and downstream terminals.
Always use a properly rated voltage sensing device to confirm that the device, the chassis, and the auxiliary circuits are de-energized.
Install safety barriers and display a danger sign.
During the tests, it is strictly forbidden for anyone to touch the device, the chassis, or the conductors while voltage is applied.
Before turning on power to this equipment, check that all connections are made with the correct tightening torque and the device is open (OFF position).
Before turning on power to this equipment, put all devices, doors, and covers back in place.
Before turning on power to this equipment, beware of potential hazards and carefully inspect the work area for tools and objects that may have been left inside the equipment.

Failure to follow these instructions will result in death or serious injury.

DANGER
HAZARD OF DEVICE FALLING Be sure that lifting equipment has lifting capacity for the device being lifted. Follow manufacturer’s instructions for use of lifting equipment. Wear hard hat, safety shoes, and heavy gloves. Failure to follow these instructions will result in death or serious injury.

Procedure Definition

Procedure characteristics	Description
Action	Check the condition of the elements of the breaking unit: Separator plates and sides of arc chute assembly. Fixed and moving contact tips. Arcing contacts which protect the contact tips.
Goal	Verify that all subassemblies participating in arc extinction for rated and short-circuit currents correctly operate.
Frequency	Refer to Recommended Frequency for the Intermediate End-User Maintenance Program.
Special indications	This procedure is not applicable to the MasterPacT MTZ1 H3 devices because arc chutes are not removable on MasterPacT MTZ1 H3 devices.
Necessary tools	Torque wrench
Related documents	MasterPacT MTZ1 - IEC Switch-Disconnectors and Circuit Breakers with MicroLogic X Control Unit - User Guide MasterPacT MTZ2/MTZ3 - IEC Switch-Disconnectors and Circuit Breakers with MicroLogic X Control Unit - User Guide MasterPacT MTZ - IEC Switch-Disconnectors and Circuit Breakers with MicroLogic X Control Unit - Maintenance Guide MasterPacT MTZ1 - Arc Chute - Instruction Sheet MasterPacT MTZ2/MTZ3 - Arc Chute - Instruction Sheet

Preliminary Conditions

The device must comply with the conditions specified below. Refer to the MasterPacT MTZ User Guides to find instructions for operating the device.

Device installation type	Position of poles	Mechanism	Device position in the chassis
Fixed	Open	Discharged	N/A
Drawout	Open	Discharged	Removed from chassis

Checking Separator Plates

Execute the following procedure for each arc chute and one arc chute at a time.

Step	Action	Corrective action
1	Remove the fixing screws on one arc chute. NOTE: Do not remove the other arc chutes.
2	Remove the arc chute. NOTE: Do not turn the arc chute upside down when removing it so that the fixing screws do not fall in the arc chamber.
3	Check the separator plates: the separator plates must not be corroded, they may be blackened but must not be significantly damaged. Example: MasterPacT MTZ2 16 H1 with separator plates OK after 7,500 cycles at In.	If damage is extensive, replace the arc chute (refer to MasterPacT MTZ - Arc Chute - Instruction Sheet). Example: MasterPacT MTZ2 16 H1 with new separator plates.
4	Compare the number of electrical operating cycles with the maximum values indicated in MasterPacT MTZ - IEC Switch-Disconnectors and Circuit Breakers with MicroLogic X Control Unit - Maintenance Guide .	Depending on the number of electrical operating cycles and state of separator plates, replace the arc chute (refer to MasterPacT MTZ - Arc Chute - Instruction Sheet). Refer to the MasterPacT MTZ with MicroLogic X Control Unit - Catalog for spare parts.

Checking Surface of Arcing Contact and Fixed and Moving Contact Tips

Step	Action	Corrective action
1	With the arc chute removed, check the surface of the arcing contact and fixed contact tips. Example: MasterPacT MTZ2 16 H1 with arcing contact and fixed contact tips OK after 7,500 operating cycles at In. A Arcing contact B Fixed contact tips	If the arcing contact or fixed contact tips are extensively damaged, contact your Schneider Electric Services representative to replace the breaking unit. Example: MasterPacT MTZ2 16 H1 with new contact tips and arcing contact. A Arcing contact B Fixed contact tips
2	Check the surface of the moving contact tips. Example: MasterPacT MTZ1 with moving contact tips OK after 7,500 operating cycles at In.	If the moving contact tips are extensively damaged, contact your Schneider Electric Services representative to replace the breaking unit. Example: MasterPacT MTZ1 16 H1 with new contact tips.
3	Compare the number of operating cycles at In with the maximum values indicated in MasterPacT MTZ - IEC Switch-Disconnectors and Circuit Breakers with MicroLogic X Control Unit - Maintenance Guide .	If the limit has been reached, contact your Schneider Electric Services representative to replace the breaking unit. Example: For MasterPacT MTZ2 16 H1, the breaking unit must be changed when 1,000 cycles are reached.

Checking Contact-Wear Indicator On MasterPacT MTZ1

DANGER
HAZARD OF ELECTRIC SHOCK, EXPLOSION, OR ARC FLASH The fixed device must be de-energized on the upstream and downstream terminals. Always use a properly rated voltage sensing device to confirm that the device and the auxiliary circuits are de-energized. Failure to follow these instructions will result in death or serious injury.

Step	Action	Corrective action
1	Close the device
2	Check that the distance between the edge of the plastic and the arcing horn is at least 1 mm as shown below: If 1 mm ≤ d < 3 mm, contact tips are OK. If d < 1 mm, contact tips are worn.	If d < 1 mm, the contact tips are worn. Contact your Schneider Electric Services representative to replace the breaking unit.

Step

Action

Corrective action

1

Close the device

2

Check that the distance between the edge of the plastic and the arcing horn is at least 1 mm as shown below:

If 1 mm ≤ d < 3 mm, contact tips are OK.
If d < 1 mm, contact tips are worn.

If d < 1 mm, the contact tips are worn.

Contact your Schneider Electric Services representative to replace the breaking unit.

Checking Contact-Wear Indicator On MasterPacT MTZ2/MTZ3

DANGER
HAZARD OF ELECTRIC SHOCK, EXPLOSION, OR ARC FLASH The fixed device must be de-energized on the upstream and downstream terminals. Always use a properly rated voltage sensing device to confirm that the device and the auxiliary circuits are de-energized. Failure to follow these instructions will result in death or serious injury.

Step	Action	Corrective action
1	Close the device.
2	Check that the channel is covered by the arcing horn for Type A devices: MTZ2 08–40 NA, HA, H1, H2, HA10 MTZ2 08–20 N1 MTZ2 20–40 H3 A Arcing horn B Channel Example: Contact-wear indicator on a MasterPacT MTZ2 device OK after 7,500 operating cycles at In.	If the channel is no longer covered, the contact tips are worn. Contact your Schneider Electric Services representative to replace the breaking unit. Example: Original state of contact-wear indicator on a MasterPacT MTZ2 device. A Channel
3	Check that the channel is covered by the arcing horn for Type B devices: MTZ2 08-20 L1 MTZ3 40-63 H1, H2, HA A Arcing horn B Channel	If the channel is no longer covered, the contact tips are worn. Contact your Schneider Electric Services representative to replace the breaking unit. Example: Original state of contact-wear indicator on a MasterPacT MTZ2 device. A Channel

Step

Action

Corrective action

1

Close the device.

2

Check that the channel is covered by the arcing horn for Type A devices:

MTZ2 08–40 NA, HA, H1, H2, HA10
MTZ2 08–20 N1
MTZ2 20–40 H3

A Arcing horn

B Channel

Example: Contact-wear indicator on a MasterPacT MTZ2 device OK after 7,500 operating cycles at In.

If the channel is no longer covered, the contact tips are worn.

Contact your Schneider Electric Services representative to replace the breaking unit.

Example: Original state of contact-wear indicator on a MasterPacT MTZ2 device.

A Channel

3

Check that the channel is covered by the arcing horn for Type B devices:

MTZ2 08-20 L1
MTZ3 40-63 H1, H2, HA

A Arcing horn

B Channel

If the channel is no longer covered, the contact tips are worn.

Contact your Schneider Electric Services representative to replace the breaking unit.

Example: Original state of contact-wear indicator on a MasterPacT MTZ2 device.

A Channel

Checking Sides of Arc Chamber

Step	Action	Corrective action
1	Check the sides of the arc chamber. The sides of the arc chamber must not be cracked, they may be blackened but must show no traces of burns or holes. A Traces of burns B Blackened parts	If the sides are burned or punctured, contact your Schneider Electric Services representative to replace the breaking unit.
2	Put the arc chute back in place. NOTE: For MasterPacT MTZ1: Make sure that the arrow on the top of the arc chute points towards the mechanism.
3	Tighten the arc chute fixing screws to the recommended value using a torque wrench: For MasterPacT MTZ1: 1.5 N•m For MasterPacT MTZ2/MTZ3: 7 N•m	If a screw cannot be tightened at the recommended value, contact your Schneider Electric Services representative.
4	Do the procedure from the beginning for another arc chute on the device.