Establish maintenance practices and provide general guidelines for switchgear maintenance. Maintenance programs can range from continuous online monitoring to run-to-failure approaches, with most combining predictive and preventive maintenance. Key aspects include inspection of components for abnormalities, maintenance of breakers and feeders, protection relay testing, and condition monitoring through load monitoring and thermography. Reliability concerns include issues with insulation, operating mechanisms, protective devices, and controls that are integral to breakers. Common failure modes include failure to close or open and spurious operation.

1. switchgear

2. “ Establish maintenance practices and provide general guidelines for switch
gear maintenance”
PM - practices
 Establish maintenance practice
 from continuous online monitoring to “run-to-failure”
 Predictive and preventive maintenance programs—including most of
the NFPA and InterNational Electrical Testing Association (NETA)
recommendations—fall in the middle of this range.
 Most real-world maintenance programs are a combination of these
approaches. Eg replace indicating lamp when fail, but do predictive
for breaker.
 Decide maintenance frequency
 Finalize preventive & diagnostic maintenance practices & schedule

3. Maintenance check points
Panel / Feeder
– Inspection of components, terminations, hardware for any
abnormality
– Ensure Panel vermin proofing
– Site specific checklist
Support Insulators
– Inspection for tracking, condensation
– Inspection for damages caused by overheating
Breaker
– PM & overhauling as per standard practice and
manufacturer guidelines

4. Maintenance check points
Protection relay and protection schemes
 Cleaning / Functional test of individual relay
 Follow specific instructions from OEM
 Protection scheme check after PM
Bus maintenance
 Cleaning / tightness / Insulation test
Condition monitoring
 Load monitoring
 Thermography

5. ELECTRICAL PARAMETERS TO CHECK
a) Insulation resistance to be measured
b) If facility is available then measure opening and closing time of
breaker .This shall be once in a year even through outside agency .
c) Measurement of contact resistance .
d) Checking of control circuit
e) Taking trial in test position for closing
and tripping .
f) Checking of indicating devices .
g) Checking of closing and tripping coils .
h) Checking of contacts
i) Checking of operating mechanism
j) Checking of auxiliary switches
k)) Checking of tightness of bolts and nuts
During Periodic Maintenance

6. Simple maintenance tips that work
Few key considerations:
Visually inspect the external condition of the switchboard on a
regular basis for foreign matter, dust and hot spots, and when
planned the inside of the cable termination chambers and other
sections within the switchboard
Annually check using infrared detection for internal electrical hot
spots
Examine the main/arcing contacts for excessive burning/damage
and recondition or renew as requirede
Check and adjust the spring contact force and contact alignment
as required
Remove, examine and clean the arc chutes and renew if damaged
Inspect, adjust and lubricate mechanisms

7. Simple maintenance tips that work
On withdrawable equipment examine the primary isolating
contacts for damage, burning, corrosion and clean and refurb
where necessary.
Check the lubrication of the circuit-breaker isolating mechanism
Check that the position indicators and interlocks work properly
Examine and check the voltage transformer if applicable
Plan for frequent trip-testing of the circuit-breakers via the
protection relay system
Never work on live equipment. Or when absolutely necessary,
use properly insulated tools to prevent risk of flashover
Check operation of interlocks and safety shutters
Carry out ductor, megger and secondary injection tests and

8. Maintenance and CM schedule
SN Activity Frequency
1 Monitor and record load current and voltage Daily
2 Thermography survey 6 months
Maintenance
Condition monitoring / Diagnostic
1 PM of breaker and feeder 6 months
2 Overhauling of breaker 3 to 4 years / OEM
recommendation
3 PM of bus bars Opportunity
4 Relay testing As per criticality of service
1 year to 4 years
5 Functional testing of protection scheme After carrying out PM / relay
testing

9. reliability concerns
Reliability concerns to not only insulation but also to the
correct functioning of the operating mechanism, protective
devices, and control that are integral to the breaker.
switchgear breakers are active elements that can fail by acting
spuriously or by not functioning upon command

10. Failure modes for medium-voltage
circuit breakers
• Failure to close
• Failure to open
• Spurious opening
• Spurious closure
• Failure to operate as required
• Failure to recharge closing spring
• Slow operation
• Short circuit to ground
• Out of calibration
• Intermittent operation

11. failure symptom categories
The following failure symptom categories were identified as being
important:
• Movement of the breaker mechanism is impeded by insuffi cient or
inadequate lubrication
• Movement of the breaker mechanism is impeded by broken, bent,
or loose parts, friction, binding, resulting from excessive stress,
wear, or faulty installation
• Operation of the breaker is impeded by incorrect adjustment of set
points/limit switches
• Various electrical problems caused, e.g., by defective coils,
defective command circuits, wiring faults, loose wires, poor
contacts, and blown fuses
• Others (e.g., dirt, pollution, and corrosion)

13. MAINTENANCE OF POWER TRANSFORMER
 General maintenance of transformer requires …..
 HALF YEARLY CHECKS:
 Check & clean bushings.
 Check OLTC mechanism for smooth operation. Check
motor & its control.
 Check dielectric strength of oil.
 Check cooling system i.e. cooling fan working and its
operating controls.
 Service fans and replace if not working.
 Check earthing of transformer.

14. MAINTENANCE OF POWER TRANSFORMER
 General maintenance of transformer requires …..
 YEARLY CHECKS:
 Check & clean bushings.
 Check OLTC mechanism for smooth operation.
 Check OLTC motor & its control.
 Check dielectric strength of oil.
 Check water content in oil.
 Check earthing of transformer.
 Check control & protection system and Tighten all
connections.
 Take routine test on transformer.

15.  General maintenance of Distribution transformer
 HALF YEARLY CHECKS:
 Check proper size of DO fuse.
 Check colour of silica gel.
 Tight all incoming / out going connections.
 Check earthing of transformer.
 Check oil leakage & attend if any.
 Clean main tank, radiator & bushings.
 YEARLY CHECKS:
 Measure IR value.
 Measure dielectric strength of oil.

16. • AFTER SERVICE OF 5 – 7 YEARS:
 Preferably, the manufacturer’s engineer may
be called at site.
 Replace all ageing gaskets.
 The existing oil in the transformer should be
filtered continuously to attain dielectric
strength of 60 kV for 1 min. or more with
improvement in the IR value.
 The procedure could also be as per the
manufacturer’s manual.

17. • AFTER SERVICE OF 5 – 7 YEARS:
 Filtration would remove sludge, dirt, moisture,
etc. from the oil.
 If condition of existing oil is found extremely
deteriorated upon testing prior to
maintenance, fresh oil should be filled in the
transformer under vacuum.
 The values of IR and PI should be taken
again to ensure the healthiness of
transformer.

18. ■ Transformer Body
 Main Tank
 Conservator tank
 Load Tap Changer
 Bushings
 Core
 Winding
■ Cooling Media / system
 Oil
 Radiator
 Radiator Fans
 Oil Pumps
Accessories
 Breather
 Buchholtz relay
 Oil and Winding Temp. indicator
 Explosion vent
 Pressure release valve
 MOG
 OSR
 Marshaling box