Making time for a standardized approach to electrical preventive maintenance programs for renewable projects
By Ben Clark
Many renewable energy projects set time aside for commissioning the project, but very few set aside time in the future for preventive maintenance. Proper preventive maintenance is key to a long-lasting, reliable, and safe renewable energy project.
Steps to Creating a Preventive Maintenance Program:
Qualified Electrical Workers (QEW)
Having Qualified Electrical Workers perform work provides the highest opportunity to providing safe and reliable maintenance practices.
- Unqualified workers may introduce deficiencies that were not present before maintenance.
- Workers should become qualified on the specified equipment through on-the-job training by a qualified worker or through formalized training.
- An important distinction is that a worker can be considered a QEW on certain equipment, but not all.
- Technicians who are certified through industry organizations such as NETA, NFPA, and OSHA are the best prepared to handle highly variable electrical installations.
A standardized approach to electrical preventive maintenance is the most consistent approach to ensuring the maintenance outage goes smoothly.
- NFPA 70B details the Recommended Practice for Electrical Equipment Maintenance.
- NETA (InterNational Electrical Testing Association) has the Maintenance Testing Specification (MTS) which is an ANSI standard that details the appropriate testing that should be performed and their acceptable limits.
- NFPA70B provides Chapter 12 as a reference for the recommended interval for maintenance.
- ANSI/NETA MTS provides Appendix B as a quick table reference for how often equipment should be visually, mechanically, or electrically inspected.
- Environmental conditions and equipment design may change the frequency of required maintenance intervals.
Each component can be electrically tested and thermo-graphically surveyed for deficiencies. Mainly, preventive maintenance is focused on current-carrying conductors and electrical insulation.
Current-carrying conductors such as hard bus, wires, switches, breakers, fuses, and bolted connections are typically intended to provide the lowest path of resistance between the power source and the load.
- These connections are tested with a microOhmeter.
- Thermographic surveying can be performed to find hot spots indicative of poor electrical connection.
- Switches and breakers should be frequently operated and lubricated as applicable.
Electrical insulation systems such as wire insulation and standoffs are intended to allow minimal current to pass through them in service. These devices are typically tested with a MegaOhmeter.
The array itself can be tested with portable load bank devices to ensure it is operating within manufacturer specification. The array performs at its highest when the sun output is high, the array temperatures are low, and the array is free of dust.
They are adversely affected by:
- Lack of Acceptance Testing
- Excessive Mechanical Forces
- Improper Lubrication of Switches
- Improper Torquing of Connections
- Environmental Conditions such as heat, water, and dust/debris.
- NFPA70E is the Standard for Electrical Safety in the Workplace.
- Arc-flash rating at the output side of a solar inverter is typically very high.
- Special attention should be provided for hot gloves; they should be rated for the AC and DC voltage they are being used for. Solar installations could operate up to 1500 VDC.
Ben Clark is the Director of Technical Training at RESA Power. RESA Power Service is a NETA Accredited Company and is a premier national provider of mission-critical solutions for electrical components, systems, and services (www.resapower.com).