Past, Present and Future Maintenance Practices: Monitoring of Electrical Equipment Failure Indicators and Alarming

Author: Gabe Paoletti, P.E. Eaton Corporation Senior Member, IEEE gabrieljpaoletti@eaton.com Cell # 609-970-0338

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Past maintenance practices were based on

original equipment manufacturers or

industry standard guidelines. While some

of these guidelines were based on the

number of equipment operations, the

majority resulted in a time-based

maintenance program.

PAST: TIME BASED MAINTENANCE

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TIME-BASED PREVENTATIVE MAINTENANCE (Minimum)

Equipment Type Mechanical Operation

Check

Visual Inspection

Energized

Infrared Inspection

and/or Oil Testing

Outage Preventive

Main.& Testing

Cables Terminations & Connections 1 year 1 year 3 year

Liquid filled transformers 1 year 1 year 3 years

Dry type transformers 1 year 1 year 3 years

Metal-clad switchgear Monthly 1 year 3 years

MV Circuit Breakers 1 year 1 year 1 year 3 years

Buses and Bus ducts 1 year 1 year 3 years

Protective relays 1 year 1 year

Automatic Transfer Equipment 1 year 6 months 1 year 3 years

Low Voltage Equipment 1 year 1 year 3 years

Dry type transformers 1 year 1 year 3 years

Switchgear 6 months 1 year 3 years

LV Circuit Breakers 1 year 1 year 1 year 3 years

Panel boards 1 year 1 year 3 years

Direct-Current Systems: Batteries 3 months 1 year 1 year

Direct-Current Systems: Chargers 3 months 1 year 6 months

Electrical Safety Equipment Per OSHA Per OSHA Per OSHA

Ground-Fault Protection Systems 1 year

Motor Control Centers 1 year 1 year 1 year 3 years

Rotating Machinery: AC Motors 1 year 1 year 1 year 1 year

Rotating Motors & Generators 1 year 1 year 1 year 1 year

Metering 1 year 1 year 3 years

Outdoor Bus Structures 1 year 1 year 3 years

PAST: TIME BASED MAINTENANCE EXAMPLE

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Circuit breaker guidelines would recommend

detailed inspections following a fault

interruption, but when a fault occurs most of

the resources are diverted to identifying

and correcting the down steam fault, and

restoring power as soon as possible,

therefore the circuit breaker was usually

neglected…

Past “Time-Based Maintenance” is

VERY DIFFICULT to properly implement

PAST: TIME BASED MAINTENANCE ISSUES

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Present maintenance has been driven by a

reduction in maintenance budgets, while the

need for electrical uptime has become even

more critical.

Resources reduced, expectations the same

When the equipment is available for

maintenance, there is no funding to perform

the maintenance, and when the funding is

available, the equipment is not accessible to

perform the required maintenance.

PRESENT: MAINTENANCE NEEDS

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PRESENT: MAINTENANCE ISSUES

1 2 3 4 5 6 7 8 9 10 11

0%

20%

40%

60%

80%

100%

Catastrophic

Risk

Resources

Uptime

Expectations

1 2 3 4 5 6 7 8 9 10 11

0%

20%

40%

60%

80%

100%Expectations

Uptime

Resources

Catastrophic

Risk

PAST Reduced Resources

Uptime may be reduced

Potential Failure Risks increase

Management Expectations

expect continuous Uptime

FUTURE

Unique Solutions

Technology

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Review past maintenance records and

observe equipment operating conditions and

determine the level of maintenance

required based on this historical data.

Maintenance work scopes would also be

adapted to “Full-Maintenance” which

involved the traditional maintenance practices

and a lesser level of maintenance, referred to

as “Operational Maintenance.”

PRESENT: NEW MAINTENANCE APPROACHES

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The equipment would be rated and ranked

based on the past maintenance records

and ongoing visual inspections.

Low-resistance (Doctor) measurement

across a circuit breaker contacts

Insulation resistance of electrical

distribution equipment, as well as gas-in-oil

testing results for transformers.

PRESENT: NEW MAINTENANCE APPROACHES

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PRESENT: FULL VS. OPERATIONAL MAINT. LV BREAKERS LV BREAKERS

FULL MAINTENANCE OPERATIONAL MAINTENANCE

INSPECT AND OPERATE INSPECT AND OPERATE

CHECK RACKING CHECK RACKING

LUBRICATE LUBRICATE

MEGGER (INS RESISTANCE) MEGGER (INS RESISTANCE)

HIGH-CURRENT TESTING - ALL PHASES LOW-CURRENT TESTING - ONE PHASE

CLEAN

CONTACT RESISTANCE TESTING

INSPECT ARC CHUTES, CONTACTS

CHECK AUXILIARY DEVICES

CHECK MECHANISM

MAN-HOURS MAN-HOURS

3.2 0.75

Savings exceed 30% during a typical scheduled

outage. In a case study involving 390 low voltage

circuit breakers, 52.8% of the circuit breakers were

candidates for a reduced scope of maintenance

(Operational Maintenance).

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End-User Needs

Fewer Outages Possible

Lower Capital & Maintenance Budgets

Higher reliability required

Unknowns of the current state of the electrical system

My current budget is limited

Let me know that I must do maintenance and when.

Let me know that I must investigate a potential

problem now.

FUTURE: MAINTENANCE REQUIREMENTS

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Continuous monitoring of critical failure

modes, while performing this monitoring in a

cost effective manner

What to monitor? (IEEE Gold Book)

FUTURE: CONTINUOUS MONITORING

Parameter IEEE Failure Causes

Humidity 23.1%

Dust Sensors 14.9%

Temperature 9.0%

Relay Outputs 7.2%

Motion 4.9%

Water 3.6%

Smoke 3.4%

Total 66.1%

App E, Table XVIII, (Ins & Bare Bus Gear)

IEEE Standard 493-1997

Failure Contributing Causes

Gold Book data

from 1970’s on

10-20 old

electrical

equipment.

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IEEE Failure Data (e.g. Switchgear Bus)

Switchgear Bus Failure Contributing Causes (%)

From IEEE Std 493-1997 Ins. Bare Pro-Rated Monitoring Options

Appendix E - Table XVIII Bus Bus Total to 100%

Expected Application 5/15kv 480volt

Thermocycling 6.6% 6.6% 3.4% Temperature 3.4%

Mechanical Structure Failure 3.0% 8.0% 11.0% 5.6%

Mechanical Damage From Foreign Source 6.6% 6.6% 3.4% Motion 3.4%

Shorting by Tools or Metal Objects 0.0% 15.0% 15.0% 7.7%

Shorting by Snakes, Birds, Rodents, etc. 3.0% 3.0% 1.5% Motion 1.5%

Malfunction of Protective Relays 10.0% 4.0% 14.0% 7.2% Relay Trouble Contacts 7.2%

Improper Setting of Protective Device 0.0% 4.0% 4.0% 2.1%

Above Normal Ambient Temperature 3.0% 3.0% 1.5% Temperature 1.5%

Exposure to Chemical or Solvents 3.0% 15.0% 18.0% 9.2%

Exposure to Moisture 30.0% 15.0% 45.0% 23.1% Humidity 23.1%

Exposure to Dust or Other Contaminants 10.0% 19.0% 29.0% 14.9% Special Airborne Sensors 14.9%

Exposure to Non-Electrical Fire or Burning 6.6% 6.6% 3.4% Smoke 3.4%

Obstruction of Ventilation 0.0% 8.0% 8.0% 4.1% Temperature 4.1%

Normal Deterioration from Age 10.0% 4.0% 14.0% 7.2% (Temp is some benefit)

Severe Weather Condition 3.0% 4.0% 7.0% 3.6% Humidity/Temperature/Water 3.6%

Testing Error 0.0% 4.0% 4.0% 2.1%

Total 94.8% 100.0% 194.8% 100.0% 66.1%

Other Relay Outputs;

Surges, Sags, High Loads

Patent Pending

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Switchgear Bus Failure Contributing Causes (%)

From IEEE Std 493-1997 Ins. Bare Pro-Rated Monitoring Options

Appendix E - Table XVIII Bus Bus Total to 100%

Expected Application 5/15kv 480volt

Thermocycling 6.6% 6.6% 3.4% Temperature 3.4%

Mechanical Structure Failure 3.0% 8.0% 11.0% 5.6%

Mechanical Damage From Foreign Source 6.6% 6.6% 3.4% Motion 3.4%

Shorting by Tools or Metal Objects 0.0% 15.0% 15.0% 7.7%

Shorting by Snakes, Birds, Rodents, etc. 3.0% 3.0% 1.5% Motion 1.5%

Malfunction of Protective Relays 10.0% 4.0% 14.0% 7.2% Relay Trouble Contacts 7.2%

Improper Setting of Protective Device 0.0% 4.0% 4.0% 2.1%

Above Normal Ambient Temperature 3.0% 3.0% 1.5% Temperature 1.5%

Exposure to Chemical or Solvents 3.0% 15.0% 18.0% 9.2%

Exposure to Moisture 30.0% 15.0% 45.0% 23.1% Humidity 23.1%

Exposure to Dust or Other Contaminants 10.0% 19.0% 29.0% 14.9% Special Airborne Sensors 14.9%

Exposure to Non-Electrical Fire or Burning 6.6% 6.6% 3.4% Smoke 3.4%

Obstruction of Ventilation 0.0% 8.0% 8.0% 4.1% Temperature 4.1%

Normal Deterioration from Age 10.0% 4.0% 14.0% 7.2% (Temp is some benefit)

Severe Weather Condition 3.0% 4.0% 7.0% 3.6% Humidity/Temperature/Water 3.6%

Testing Error 0.0% 4.0% 4.0% 2.1%

Total 94.8% 100.0% 194.8% 100.0% 66.1%

Other Relay Outputs;

Surges, Sags, High Loads

Patent Pending

Moisture & Dust: 38%

IEEE Failure Data (e.g. Switchgear Bus)

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FUTURE: FAILURE CONTRIBUTING CAUSES

IEEE data was then grouped into sub-sets in three categories:

Humidity/Water-Discharges, Dust-Smoke and Heat-Fire and

correlated against end-user surveys which were conducted at

random IEEE regional meetings

Parameter IEEE Failure Causes IEEE Failure CausesEnd-User Feedback

(April, '08)

Humidity 23.1%

Humidity (LV),

Discharges (MV)

Humidity (LV),

Discharges (MV)

Dust Sensors 14.9% 26.7% 24.9%

Temperature 9.0% Dust, Smoke Dust, Smoke

Relay Outputs 7.2% 18.3% 16.6%

Motion 4.9% Heat, Fire Heat, Fire

Water 3.6% 9.0% 12.5%

Smoke 3.4% Total Total

Total 66.1% 54.0% 54.0%

Failure Contributing Causes

App E, Table XVIII, (Ins & Bare Bus Gear)

IEEE Standard 493-1997

Failure Contributing Causes

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FUTURE: FAILURE CONTRIBUTING CAUSES

IEEE data was then grouped into sub-sets in three categories:

Humidity/Water-Discharges, Dust-Smoke and Heat-Fire and

correlated against end-user surveys which were conducted at

random IEEE regional meetings

Parameter IEEE Failure Causes IEEE Failure CausesEnd-User Feedback

(April, '08)

Humidity 23.1%

Humidity (LV),

Discharges (MV)

Humidity (LV),

Discharges (MV)

Dust Sensors 14.9% 26.7% 24.9%

Temperature 9.0% Dust, Smoke Dust, Smoke

Relay Outputs 7.2% 18.3% 16.6%

Motion 4.9% Heat, Fire Heat, Fire

Water 3.6% 9.0% 12.5%

Smoke 3.4% Total Total

Total 66.1% 54.0% 54.0%

Failure Contributing Causes

App E, Table XVIII, (Ins & Bare Bus Gear)

IEEE Standard 493-1997

Failure Contributing Causes

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FUTURE: MONITORING REQUIREMENTS

Approximately 50% of potential failure contributing

causes of electrical distribution equipment can be

monitored, trended and alarmed to provide the desired

future maintenance mode of operation.

Humidity and the presence of water

Partial Discharges (MV Equipment)

Dust Trending and Smoke Detection

Temperature trending of cubicles, bus-duct, critical cable joints

and/or bus connections

Bus / Cable Connection Point-Temperature sensors

Load Current, Heater and Fan Circuit Currents

Intrusion or motion

Additional Options for rotating apparatus:

Vibration of rotating apparatus

Exert herm IR sensors

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FUTURE: MAINTENANCE REQUIREMENTS

Internal Copper Bus Internal Void Bus Insulating

Sleeve Internal Void

Cubicle Barrier

MV Partial Discharge Detection in MV Gear (13.8 / 34.5kv+)

Partial discharges emit high-frequency radiation and the

application of specifically designed sensors, with filtering and

data analysis equipment allows for the continuous

monitoring of these partial discharges which will lead to

eventual equipment failure

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Partial discharge detection and temperature sensors, when

combined with sensing options such as humidity, floor

water, dust, smoke, load/heater/fan currents, cubicle or

bus-duct temperatures provides a robust predictive

monitoring package for both low voltage and medium

voltage equipment. By adding available vibration sensors

to the above, this is adapted to rotating equipment.

Patented Algorithms, based on historical and designed-

based operating conditions, which will alarm when a

parameter is considered out of the normal

operating range and provide maintenance

recommendations.

FUTURE: MONITORING REQUIREMENTS

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FUTURE: SAFETY & SMART GRID FACTORS

Smart Grid: “Being notified of a potential pending failure,

before it occurs, provides us with a smarter grid.”

Safety: Thermographic surveys require direct viewing of

energized connections, requiring removal of panels and

exposing of energized equipment. With the Arc-Flash

protection requirements, difficult to safely implement.

One safety solution: infra-red viewing windows

Surveys must still be scheduled and therefore do

not provide continuous monitoring

Solution is remote continuous cubicle

temperatures trending with algorithms

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Characteristics

of Air:

With increased

temperature - air

changes from an

insulator to a conductor

- Flashover becomes

self-conducting

“Ionized Air”

Ref: W. Rieder, “Circuit Breakers: Physical and

Engineering Problems”, IEEE Spectrum, July 1970

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“PREVENTABLE” FAILURE CASE STUDIES

Monitor Humidity,

PD, Dust &

Contamination

(Moisture)

Monitor Cubicle

and/or Point

Temperatures

(Overheated

finger cluster)

Monitor Cubicle

Humidity &

Heater Current

(Heater Failure)

Life Ext: Vacuum

Replacements

ANSI Tested

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Monitor Floor

Water (Overhead

water & upstream

breaker failure

Monitor Cubicle

and/or Point

Temperatures

(Improper

Maintenance)

Monitor Cubicle

Temperature

(Finger Cluster

Failure)

Life Ext: ArcFlash

Reduction Switch,

Arc Res MCC’s

“PREVENTABLE” FAILURE CASE STUDIES

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Case Study: Monitoring of the above parameters

would have warned of a pending major equipment

failure due to severe weather conditions and the

subject equipment could have been de-energized

and isolated from the electrical grid.

Since the monitored environmental

parameters where not available to

the remote operator, the equipment

was re-energized in an attempt to

clear an anticipated minor fault and

resulted in the completed melt-down

of the medium voltage circuit breaker

and the associated enclosure.

FUTURE: MONITORING CASE STUDY

Diagnostic Remote Monitoring Automatic Report Example

Yellow Light =

Inspect soon

Red Light =

Alarm

Green Light =

Good

Customized Automatic Reporting

Yellow Light =

Inspect soon

Red Light =

Alarm

Green Light =

Good

Temperature Sensor

Alarm Level:

Text Message

Email

Voice Message

Text Message: “High Temp Cub XX Bus B”

Alarms - Blogs

Global Coverage

Iridium

Satellites

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SUMMARY The future of maintenance is here today

Economic swings are preventing past maintenance practices

Review available IEEE failure contributing causes

Combined with recent end-user surveyed data

Identify parameters to be continuous monitored, trended and alarmed

Application of new technologies (PD, temperature, algorithms)

IT-independent or integrated into a facility monitoring and alarming

Smart-grid systems that can self-predict a pending failure and also

provide for ongoing maintenance recommendations

Technological solutions exist today to support this future maintenance

mode.

Tell me when I need to do maintenance & what maintenance to do.

Tell me that I have a problem now and what I should do about it.

Past, Present and Future Maintenance Practices: Monitoring of Electrical Equipment Failure Indicators and Alarming

Author: Gabe Paoletti, P.E. Eaton Corporation Senior Member, IEEE gabrieljpaoletti@eaton.com Cell # 609-970-0338

Questions?