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MAINTENANCE FREQUENCY MATRIX
Inspections and Tests
(Frequency in Months)
Multiplier for Inspections and Tests
(Multiply Value by Matrix)
| Section | Description |
Visual |
Visual & |
Visual & Mechanical |
| 7.1 | Switchgear & Switchboard Assemblies |
12 |
12 |
24 |
| 7.2 | Transformers | |||
7.2.1.1 |
Small Dry-Type Transformers |
2 |
12 | 36 |
| 7.2.1.2 | Large Dry-Type Transformers | 1 | 12 | 24 |
| 7.2.2 | Liquid-Filled Transformers | 1 | 12 | 24 |
| Sampling | - | - | 12 | |
| 7.3 | Cables | |||
| 7.3.2 | Low-Voltage Cables | 2 | 12 | 36 |
| 7.3.3 | Medium- and High-Voltage Cables | 2 | 12 | 36 |
| 7.4 | Metal-Enclosed Busways | 2 | 12 | 24 |
| Infrared Only | - | - | 12 | |
| 7.5 | Switches | |||
| 7.5.1.1 | Low-Voltage Air Switches | 2 | 12 | 36 |
| 7.5.1.2 | Medium-Voltage Metal-Enclosed Switches | - | 12 | 24 |
| 7.5.1.3 | Medium- and High-Voltage Open Switches | 1 | 12 | 24 |
| 7.5.2 | Medium-Voltage Oil Switches | 1 | 12 | 24 |
| 7.5.3 | Medium-Voltage Vacuum Switches | 1 | 12 | 24 |
| 7.5.4 | Medium-Voltage SF6 Switches | 1 | 12 | 24 |
| 7.5.5 | Cutouts | 12 | 24 | 24 |
| 7.6 | Circuit Breakers | |||
| 7.6.1.1 | Low-Voltage Insulated-Case/Molded-Case CB | 1 | 12 | 36 |
| 7.6.1.2 | Low-Voltage Power CB | 1 | 12 | 36 |
| 7.6.1.3 | Medium-Voltage Air CB | 1 | 12 | 36 |
| 7.6.2.1 | Medium-Voltage Oil CB | 1 | 12 | 36 |
| Sampling | - | - | 12 | |
| 7.6.2.2 | High-Voltage Oil CB | 1 | 12 | 12 |
| Sampling | - | - | 12 | |
| 7.6.3.1 | Medium-Voltage Vacuum CB | 1 | 12 | 24 |
| 7.6.4.1 | Extra-High-Voltage SF6 | 1 | 12 | 12 |
| 7.7 | Circuit Switchers | 1 | 12 | 12 |
| Section | Description | Visual | Visual & Mechanical |
Visual & Mechanical & Electrical |
| 7.8 | Network Protectors | 12 | 12 | 24 |
| 7.9 | Protective Relays | |||
| Electromechanical | 1 | 12 | 12 | |
| Electronic | 1 | 12 | 12 | |
| 7.10 | Instrument Transformers | 12 | 12 | 36 |
| 7.11 | Metering Devices | 12 | 12 | 36 |
| 7.12 | Regulating Apparatus | |||
| 7.12.1.1 | Step-Voltage Regulators | 1 | 12 | 24 |
| Sample Liquid | - | - | 12 | |
| 7.12.1.2 | Induction Regulators | 12 | 12 | 24 |
| 7.12.2 | Current Regulators | 1 | 12 | 24 |
| 7.12.3 | Load-Tap-changers | 1 | 12 | 24 |
| Sample Liquid | - | - | 12 | |
| 7.13 | Grounding Systems | 2 | 12 | 24 |
| 7.14 | Ground-Fault Protection Systems | 2 | 12 | 12 |
| 7.15 | Rotating Machinery | |||
| 7.15.1 | AC Motors | 1 | 12 | 24 |
| 7.15.2 | DC Motors | 1 | 12 | 24 |
| 7.15.3 | AC Generators | 1 | 12 | 24 |
| 7.15.4 | DC Generators | 1 | 12 | 24 |
| 7.16 | Motor Control | |||
| 7.16.1.1 | Low-Voltage Motor Starters | 2 | 12 | 24 |
| 7.16.1.2 | Medium-Voltage Motor Starters | 2 | 12 | 24 |
| 7.16.2.1 | Low-Voltage Motor Control Centers | 2 | 12 | 24 |
| 7.16.2.2 | Medium-Voltage Motor Control Centers | 2 | 12 | 24 |
| 7.17 | Adjustable Speed Drive Systems | 1 | 12 | 24 |
| 7.18 | Direct-Current Systems | |||
| 7.18.1 | Batteries | 1 | 12 | 12 |
| 7.18.2 | Battery Chargers | 1 | 12 | 12 |
| 7.18.3 | Rectifiers | 1 | 12 | 24 |
| 7.19 | Surge Arresters | |||
| 7.19.1 | Low-Voltage Devices | 2 | 12 | 24 |
| 7.19.2 | Medium- and High-Voltage Devices | 2 | 12 | 24 |
| 7.20 | Capacitors and Reactors | |||
| 7.20.1 | Capacitors | 1 | 12 | 12 |
| 7.20.2 | Capacitor Control Devices | 1 | 12 | 12 |
| 7.20.3.1 | Reactors - Dry-Type | 2 | 12 | 24 |
| 7.20.3.2 | Reactors - Liquid-Filled | 1 | 12 | 24 |
| Sampling | - | - | 12 | |
| 7.21 | Outdoor Bus Structures | 1 | 12 | 36 |
| 7.22 | Emergency Systems | |||
| 7.22.1 | Engine Generator | 1 | 2 | 12 |
| Functional Testing | - | - | 2 | |
| 7.22.2 | Uninterruptible Power Systems | 1 | 12 | 12 |
| Section | Description | Visual |
Visual & Mechanical |
Visual & Mechanical & Electrical |
| Functional Testing | - | - | 2 | |
| 7.22.3 | Automatic Transformer Switches | - | 12 | 12 |
| Functional Testing | - | - | 2 | |
| 7.23 | Telemetry/Pilot Wire SCADA | 1 | 12 | 12 |
| 7.24 | Automatic Circuit Reclosers and Line Sectionalizers | |||
| 7.24.1 | Automatic Circuit Reclosers, Oil/Vacuum | 1 | 12 | 24 |
| Sampling | - | - | 12 | |
| 7.24.2 | Automatic Line Sectionalizers, Oil | 1 | 12 | 24 |
| Sampling | - | - | 12 | |
| 7.27 | EMF Testing | 12 | 12 | 12 |
| NETA recognizes that the ideal maintenance program is
reliability-based, unique to each plant and to each piece of equipment.
In the absence of this information and in response to requests for a
maintenance timetable, NETA’s Standards Review Council presents the
following time-based maintenance schedule and matrix. One should contact DYMAX for a reliability-based evaluation. The following matrix is to be used in conjunction with NETA’s Frequency of Maintenance Tests table. Application of the matrix is recognized as a guide only. Specific condition, criticality, and reliability must be determined to correctly apply the matrix. Application of the matrix, along with the culmination of historical testing data and trending, should provide a quality electrical preventive maintenance program. |
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MAINTENANCE FREQUENCY MATRIX |
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EQUIPMENT CONDITION |
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POOR | AVERAGE | GOOD | |
| EQUIPMENT RELIABILITY REQUIREMENT | LOW | 1.0 | 2.0 | 2.5 |
| MEDIUM | 0.50 | 1.0 | 1.5 | |
| HIGH | 0.25 | 0.50 | 0.75 | |
St. Paul Division – (763)
784-4040
Detroit Division – (248) 477-6066
Canton Division – (330) 484-6801
Ann Arbor Division – (734) 222-9951
