MEDIUM VOLTAGE BREAKER (600VOLTS AND ABOVE)
The medium voltage gear in any plant is usually 2.4KV to 13.2 and is used as your main incoming voltage
equipment. It is imperative that this particular equipment always be in first class condition. The protective relays
must always be operative and set within your power study curves. The tripping voltage must always be present.
The failure to maintain this gear in first class condition can and will result in total loss of all of your electrical power.
There are complete books written on the maintenance testing and care for this particular gear. I will outline the most
important things to do in the testing and checking of this gear. These few steps are carefully and completely
adhered to by Southern Substation, Inc., technicians and in over twelve years of this practice the industries using
our techniques have not had a single failure.
TEST PROCEDURE FOR MEDIUM VOLTAGE BREAKER
The following is a step by step procedure taken by and recommended by Southern Substation, Inc., technicians on
the testing, cleaning and inspection of medium voltage (600 volts of more) air breakers.
A) Breaker is removed from cubicle and thoroughly cleaned.
B) Cubicle is cleaned of all excess dirt and dust.
C) Inspect and check all mechanical and/or hydraulic linkages for proper operation.
D) Inspect and check interior and exterior hardware including sliding tracks, fittings, catches, barriers,
discoloration, looseness, fatigue and wear.
E) All rollers associated equipment are cleaned and lubricated.
F) Inspect and check insulation, insulating tapes, insulated epoxy for damage, tracking and wear.
G) Check switches and fuse holders for freedom of movement and proper contact pressure.
H) Check safety and electrical interlocks for correct operation.
I) The following items must be checked and measured to assure that they are within the manufacturers
specifications. These items each have different measurements according to each breaker and each
manufacturer. The tolerances given in each manufacturers bulletin must be clearly adhered to.
1. Primary contact wipe
2. Arcing contact wipe
3. Primary contact gap
4. Trip latch wipe
5. Trip latch clearance
6. Prop clearance
7. Release latch wipe
8. Release latch monitoring switch
9. Motor and relay switch (cut off and cut on)
10. Interlock switch
11. Auxiliary switch
12. Driving latching pawl
13. Latching checking switch
14. Plunger interlock
J) Puffer assembly must be checked to assure that it will blow out arc.
K) Arc chutes assemblies must be checked to assure they are free of foreign matter and properly connected.
L) Inspect buss and support insulators (torque all buss and bolted connections to ASA standards).
M) Using minimum 1,000 VDC, megger breaker and buss, phase to phase, and phase to ground.
N) Inspect, check and clean all controls and metering transformers.
O) Inspect all wiring to make sure that no damage has resulted during installation and/or usage and test for
possible grounds or short circuits.
P) Operate breakers slowly with manual closing wrench and note that there is no excessive binding or function
and that the breaker can be moved to the fully opened and fully closed position.
Q) Check the trip coil plunger and the release coil plunger to see that they move freely.
R) Return breaker to test position. Using the owners board sequence of operation assure that the breaker will
open and close electrically and by the manual handle and will trip using the relays. The acceptance testing
and routine maintenance of this equipment should be foremost in any preventative maintenance program in
your plant.
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The medium voltage gear in any plant is usually 2.4KV to 13.2 and is used as your main incoming voltage
equipment. It is imperative that this particular equipment always be in first class condition. The protective relays
must always be operative and set within your power study curves. The tripping voltage must always be present.
The failure to maintain this gear in first class condition can and will result in total loss of all of your electrical power.
There are complete books written on the maintenance testing and care for this particular gear. I will outline the most
important things to do in the testing and checking of this gear. These few steps are carefully and completely
adhered to by Southern Substation, Inc., technicians and in over twelve years of this practice the industries using
our techniques have not had a single failure.
TEST PROCEDURE FOR MEDIUM VOLTAGE BREAKER
The following is a step by step procedure taken by and recommended by Southern Substation, Inc., technicians on
the testing, cleaning and inspection of medium voltage (600 volts of more) air breakers.
A) Breaker is removed from cubicle and thoroughly cleaned.
B) Cubicle is cleaned of all excess dirt and dust.
C) Inspect and check all mechanical and/or hydraulic linkages for proper operation.
D) Inspect and check interior and exterior hardware including sliding tracks, fittings, catches, barriers,
discoloration, looseness, fatigue and wear.
E) All rollers associated equipment are cleaned and lubricated.
F) Inspect and check insulation, insulating tapes, insulated epoxy for damage, tracking and wear.
G) Check switches and fuse holders for freedom of movement and proper contact pressure.
H) Check safety and electrical interlocks for correct operation.
I) The following items must be checked and measured to assure that they are within the manufacturers
specifications. These items each have different measurements according to each breaker and each
manufacturer. The tolerances given in each manufacturers bulletin must be clearly adhered to.
1. Primary contact wipe
2. Arcing contact wipe
3. Primary contact gap
4. Trip latch wipe
5. Trip latch clearance
6. Prop clearance
7. Release latch wipe
8. Release latch monitoring switch
9. Motor and relay switch (cut off and cut on)
10. Interlock switch
11. Auxiliary switch
12. Driving latching pawl
13. Latching checking switch
14. Plunger interlock
J) Puffer assembly must be checked to assure that it will blow out arc.
K) Arc chutes assemblies must be checked to assure they are free of foreign matter and properly connected.
L) Inspect buss and support insulators (torque all buss and bolted connections to ASA standards).
M) Using minimum 1,000 VDC, megger breaker and buss, phase to phase, and phase to ground.
N) Inspect, check and clean all controls and metering transformers.
O) Inspect all wiring to make sure that no damage has resulted during installation and/or usage and test for
possible grounds or short circuits.
P) Operate breakers slowly with manual closing wrench and note that there is no excessive binding or function
and that the breaker can be moved to the fully opened and fully closed position.
Q) Check the trip coil plunger and the release coil plunger to see that they move freely.
R) Return breaker to test position. Using the owners board sequence of operation assure that the breaker will
open and close electrically and by the manual handle and will trip using the relays. The acceptance testing
and routine maintenance of this equipment should be foremost in any preventative maintenance program in
your plant.
<PREVIOUS
Medium Voltage Breakers
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