Hierarchy of Electrical Equipment Operations and Maintenance

May 5, 2023

When it comes to industrial power systems, ensuring that they remain operational and reliable is critical for business continuity. Power outages and equipment failures can lead to production downtime, resulting in lost revenue and missed deadlines. To prevent such issues, companies must implement a comprehensive maintenance strategy that takes into account the hierarchy of criticality for their power systems.

The electrical System can be broken down into 3 distinct parts: Critical Power, Power Distribution, and Utilization Equipment.

Critical Power (UPS equipment, Substation Batteries, Emergency Generators & Batteries, Battery Chargers)

Critical power equipment has the highest criticality and impact to ongoing operations. Failure can result in loss of process control likely, life safety hazards likely, major environmental impacts, and large business impacts.

Systems should be designed to be highly reliable and redundant with a focus on maintainability. These systems in a typical plant should be industrial grade with a life cycle of 25 years or greater. Maintenance, operations, and budgeting for the critical power systems should fall under the electrical department and electricians or an electrical operations team should be solely responsible for operating critical power equipment. While not achievable in many industrial plants that have been built over time, homogeneity in the type of equipment, operational procedures, and vendors is an important part of developing a design and maintenance plan for critical power equipment. The electrical maintenance department should have a high degree of influence in the selection of equipment types and configuration for this type of equipment and should be consulted by capital projects team whenever critical power equipment is being utilized, replaced, or installed.

When developing a maintenance program these equipment types should be focused on initially because they have the highest impact and criticality.

-Focus on HVAC maintenance and redundancy it is important.

-Depending on the geographic location of the plant. Overheating of electrical equipment is a major concern and should not be overlooked. The heat load in the building or substation should be assessed and full redundancy in the system is critical. HVAC systems that are “special” such as classified HVAC systems should be avoided as lead times on parts can be many weeks. Instead design the system so that the equipment is outside the area classification. Install Alarming on all HVAC systems so that workorders can be written in a timely manner.

-Valve Regulated Batteries should be avoided.

-Populations of equipment should homogenous when possible

-Maintainability should be required and thought through with input from the electrician supervisors or leads.

-Avoid small UPS’s in lieu of centralized UPS’s whenever possible.

-Fight the installation of small suitcase UPS systems at all costs as they are not tracked and not maintained.

-Avoid commercial critical power equipment and install industrial equipment.

-Develop UPS Power philosophy so that only equipment that absolutely requires UPS power is connected.

-Utilize Vendor (OEM) service and support for specialized equipment instead of trying to train internal experts. Focus on operating the equipment and basic troubleshooting competency of the equipment instead.

-Your electricians are electrical operators first and technicians second.

Power Distribution (Incoming Main breakers, tie breakers, Switchgear, MCC horizontal and vertical busses, Service Power Transformers, Service Power Cables, Bus Duct, Medium voltage equipment, overhead distribution, grounding systems, grounding resistors, switchyards, generators)

Power distribution equipment has the second highest criticality and impact on ongoing operations. Failure results in operational impact, limited life safety hazards, environmental impacts are likely, large business impacts are also likely. System reliability, redundancy, and maintainability should be considered during the design process.

Electricians or electrical operators are responsible for operating power distribution equipment. Control of the maintenance budgeting for power distribution equipment should be part of the electrical department so it can be stewarded by the in-house subject matter experts. For medium voltage equipment it is recommended that control systems and equipment types have homogeneity to simplify operations for electricians and help electricians build confidence in operating the electrical distribution equipment.

-Focusing on HVAC maintenance and redundancy is important. (See notes on HVAC in Critical Power Section)

-Avoid overly complicated systems. The goal should be that the layout and design of the equipment should allow the Electrical Staff to safely operate the equipment even if they have never seen or been trained on the specific piece of equipment.

-Look and Feel of power distribution controls should be as homogenous as possible so that electricians build confidence in operating electrical equipment at medium voltages or critical equipment.

-Maintainability should be required and thought through with input from the electrician supervisors or leads.

-Redundant equipment should be on separate buses on a typical MTM. Load separation is very important for overall system reliability and for being able to plan and execute maintenance outages.

-Maintenance planning requires input from operations, and they should be engaged early. Operating Power distribution equipment for preventative maintenance in a process environment requires gaining confidence from process owners. Misoperation resulting in an unplanned outage quickly erodes that confidence and should be avoided at all costs

-Avoid Switchracks and outdoor switchgear when possible.

When developing a maintenance program power distribution equipment is lower priority after the critical power category. Focus on critical power should come first.

Utilization Equipment (Motors, Motor Starters, VFDs, Lighting, Lighting Panels, lighting transformers, Power Panels, power transformers)

Utilization equipment normally has the lowest criticality and impact on ongoing operations. Failure results in some operational impact, normally no life safety hazards, environmental impacts are possible, and large business impacts are possible but not likely. System reliability, redundancy, and maintainability should be considered during the design process. For severe duty equipment or environments where MTBF will be low special consideration of increased redundancy is recommended so that maintenance can be performed without operational impact.

Equipment owners are responsible for operating the utilization equipment. Process Operators can operate 480V breakers and below. Electricians operate equipment above 480V or critical power or power distribution equipment.  Control of the maintenance budgeting for utilization equipment should be part of the process owner’s budget.

When developing a maintenance program these equipment types have the lowest impact and criticality and should be focused on after Critical Power and Power Distribution.

-Motor Criticality Impact study should be done by mechanical and process with electrical involvement. Electrical then uses this information for maintenance planning and warehousing capital spares when necessary.

-Motor Cable Replacement plan

-IR Thermography is a leading indicator of failure. Low cost. Highly predictive.

-Keep your equipment clean and dry.

Types of Maintenance Strategies:

Preventive Maintenance (PM) – This strategy involves conducting regular inspections and maintenance on equipment to prevent failures from occurring. PM tasks may include cleaning, lubrication, and parts replacement. The frequency of PM tasks should be determined based on the criticality of the equipment. This type maintenance is scheduled on a calendar basis.

Predictive Maintenance (PdM) – PdM uses data analysis techniques to predict when equipment failures are likely to occur. This strategy can help companies detect potential issues before they result in equipment failures and production downtime.

Condition-Based Maintenance (CBM) – CBM uses sensors and monitoring equipment to detect changes in equipment condition that may indicate a potential failure. This strategy can help companies optimize maintenance schedules by performing maintenance tasks only when necessary.

Run-to-Failure Maintenance (RTF) – RTF involves allowing equipment to run until it fails, at which point it is repaired or replaced. This strategy is typically only used for non-critical equipment or components that are nearing the end of their useful life.

Choosing the Right Maintenance Strategy

Choosing the right maintenance strategy for a company's power system depends on a variety of factors, including the criticality of the equipment, the age of the equipment, and the availability of maintenance resources. Companies should also consider the cost of downtime and lost production when selecting a maintenance strategy.

For example, a company with critical equipment that is expensive to repair or replace may opt for a PdM strategy, as it can help detect potential issues before they lead to equipment failures. On the other hand, a company with older, non-critical equipment may choose an RTF strategy to avoid the cost of unnecessary maintenance tasks.


Implementing a comprehensive maintenance strategy for an industrial power system is critical to ensuring that the system remains operational and reliable. By identifying the criticality of the different components of the system and choosing the right maintenance strategy, companies can reduce the risk of power outages and equipment failures that can result in lost revenue and missed deadlines.

Focused on bringing power to your Vision.
Contact Site Electric Services to design and construct your next project
get in touch