Maintenance Requirements for Distributed Energy Resources
To encourage safer electrical systems, the 2023 update to National Fire Protection Association (NFPA) Standard 70B shifted from a “recommended practice” to a “standard” that contains mandatory requirements for the development, implementation, and operation of an electrical maintenance program (EMP).
In addition to covering all common electrical system components, the 2023 update to NFPA 70B includes specific guidance for the maintenance of:
- Photovoltaic (PV) systems (Chapter 30)
- Wind power systems and associated equipment (Chapter 31)
- Battery energy storage systems (Chapter 32)
- Electric vehicle (EV) power transfer systems and associated equipment (Chapter 33)
This new standard can help electrical system owners ensure they are getting the most out of their investments in energy transition technologies while protecting people and personnel. But what does the new standard entail? And how can you ensure your preventive maintenance plan is compliant? The first important thing to understand is how to properly assess the condition of your equipment.
Equipment condition assessment drives efficient preventive maintenance
Chapter 10 of the NFPA 70B standard prescribes maintenance intervals for specific pieces of electrical componentry based on equipment condition assessment. This is an evolution of the table that previously existed in Annex L but goes a step further to consider the condition of the equipment being maintained, with factors including:
- Equipment physical condition
- Criticality
- Operating environment
The equipment condition assessment (ECA) is driven by the highest value of these three conditions. For example, if the equipment is designated “Condition 1” for electrical equipment and criticality, but a “Condition 3” for the operating environment, it would use “Condition 3” durations for the ECA maintenance intervals.
NFPA 70B also requires a condition of maintenance indication to communicate the serviceability of the electrical equipment to electrical workers.
Maintenance intervals guide routine preventive maintenance.
Once the equipment condition assessment is performed, Chapter 10 of NFPA 70B provides mandatory scopes of work and maintenance intervals broken out by product type. These requirements can be referenced in Table 10.1.2.1, which is in alphabetical order and provides the corresponding reference chapter for the scope of work specifics.
It is important to note that these maintenance intervals do not supersede the manufacturer’s guidelines; they provide guidance only in the absence of information from the manufacturer.
For example, the following maintenance intervals would be required for a PV system classified under the corresponding condition assessments (see Table).
This means if a PV system received an ECA rating of Condition 3 because it could be supporting a microgrid or emergency power system, the PV system requires visual inspection and regular electrical testing at an interval of every 12 months unless manufacturer guidelines advise otherwise.
What is electrical testing?
As mentioned above, NFPA 70B requires detailed, prescriptive testing processes for preventive maintenance program compliance. These guidelines are described in Chapter 8: Field Testing and Test Methods.
Compared to previous versions of 70B, the update clearly defines testing category types in Section 8.3:
- 1 — online standard test: Performed while the electrical equipment or device is connected to the source of supply.
- 1A — online enhanced test: Not typically performed in normal electrical maintenance activities, and provides additional diagnostic information.
- 2 — offline standard test: Performed while the electrical equipment or device is disconnected from the source of supply or is connected to an external test voltage source of supply.”
- 2A — offline enhanced test: Typically not required, but may be useful based on the application of the equipment or if there is a problem with the equipment. For example, a “rated hold-in” test per NEMA AB-4 might be performed on a molded case circuit breaker if the circuit breaker has been tripping under normal load conditions.
It is important to note that NFPA 70B provides the minimum requirements for preventive maintenance, which are superseded by manufacturer guidelines. For instance, NFPA 70B states that testing trip functions is optional for circuit breakers 250A or less. Circuit breakers with electronic trip units that are rated or can be adjusted to 250A or over only require verification of the calibration of all the functions of the trip unit using the manufacturer’s specified test set. Modern electronic trip units feature built-in communications via USB connection for verification of the calibration of the trip functions being used, saving time and the cost of expensive test kits.
Intelligence and digitalization can help simplify electrical testing
In the 2023 NFPA 70B standard, language was added to allow continuous monitoring and predictive techniques to drive maintenance intervals compared to the tables provided.
For example, when considering trip function testing, modern advancements in intelligent trip units are revolutionizing the ability to monitor overall circuit breaker health. These trip units dramatically streamline traditional breaker inspection procedures, with an at-a-glance health indicator and powerful data analytics that detail the health condition of the breaker. The health analytics provide predictive maintenance diagnostics along with detailed reports on operations, short-circuits, overloads, temperature, and more to help enhance system reliability.
These technologies can be applied in EV charging applications to provide remote load testing, time-stamped event summaries, and high-speed event waveform captures with detailed event logging to simplify preventive maintenance.
Additionally, there are add-on devices you can implement to provide continuous, non-invasive online monitoring for switchgear, transformers, bus ducts, and cable connections commonly found in alternative energy applications. These devices provide predictive monitoring to help users make more informed safety and maintenance decisions.
Preventive maintenance supports a safer, more sustainable future
It’s been half a century since the first version of NFPA 70B was issued as a recommended practice. Today, the transition to a standard provides more enforceability for what shall be done when it comes to electrical equipment maintenance. That is a win-win for the reliability of electrical equipment and the overall safety of the electrical system for those individuals tasked with working on it.
