Power risk assessments done right

How well is your power distribution system performing? Here’s how to find out.

By Frank Waterer, Schneider Electric

All cultural and economic activities in any modern society depend upon the availability and use of reliable electrical power. Businesses cannot afford even momentary unscheduled interruptions; dependable and reliable electrical power systems are crucial. And it’s not only critical facilities such as hospitals, data centers, and financial institutions, as well as national defense partners, that require consistent and reliable power – even small businesses in your communities and townships depend on “always-available/always-on” capabilities to be successful.

A power distribution system’s (PDS) reliability is directly related to the original quality, age, and history of maintenance for each piece of equipment that makes up the entire system. Statistically, older electrical equipment is more likely to cause power disruptions, and power disruptions can cause costly inoperable conditions, damages, and downtime. Some outages may even pose safety risks to facility staff. Because of how important electrical infrastructure reliability is to businesses, electrical facility staff face a great deal of pressure to ensure that their equipment is well-maintained, reliable, and adequately updated.

One effective way to ensure optimal performance of the electrical infrastructure is through routine inspections and assessments of the risks to electrical equipment and systems that identify weaknesses or potential points of malfunction that can negatively affect the entire PDS. Professional assessments determine which equipment may need additional attention, maintenance, testing, or replacement, as well as the order and timing of necessary activities. Conducting professional risk assessments of a PDS and following up on the issues and recommendations identified can help safeguard against inefficiencies and failures. Here, we’ll examine why assessments are important and how to conduct them.

Performing risk assessments


Risk assessments are critical to evaluating a PDS’s reliability and are most effective when facility managers are conducting them proactively. However, the unfortunate reality is that many assessments are conducted reactively, with managers commissioning inspections of their electrical infrastructure only after an event that has seriously affected personnel or operations has occurred. Such an event may be an arc-flash incident, a ground fault occurrence, an electrical fire, a shock event, or an unexpected power outage.

To avoid negative and unsafe events, electrical power engineers recommend conducting comprehensive assessments of electrical systems every five years. Because most electrical equipment has an average life span of 20 years, it is good practice to assess the entire PDS every five years to determine the present state and deterioration rate of each piece of equipment. Also, because electrical equipment deteriorates at different rates, the inspections and risk assessments provide facility managers a firm understanding concerning the present state of their PDS and information as to where or when they may need to replace or modernize a piece of equipment or enhance equipment maintenance. Understanding a PDS’s maintenance or upgrade requirements will give a better picture of the system’s reliability and risks.

Reliability and risk are companions. Qualified electrical power engineers are professional engineers registered by the state within which the assessments are performed. They determine the equipment’s age, type, operational purposes, and environmental conditions to assess its present state. Professional risk assessments not only evaluate how often equipment has been maintained, but also they consider:

  • Are the circuit breakers in an adequate state to provide protection? Are they overdutied, underrated, or overused?
  • Have the system voltages been stable over time?
  • Is any power circuit overloaded or imbalanced?
  • Are the conductors and circuit breakers the correct type and ampere rating?
  • Is there effective ground fault protection?
  • What’s the state of the bonding and grounding systems?
  • Are there effective protections against surge events and lightning strikes?

After performing the assessments, the power engineers employ mathematical formulas and calculations to give the system numeric reliability ratings for each piece of equipment and the power circuits. Once the engineers determine the reliability of each piece, additional calculations determine the entire PDS’s reliability. This data helps facility managers make critical maintenance and upgrade decisions.

Preparing and performing the assessment


Few electrical power engineers possess the unique skill set required to conduct reliable risk assessments of power distribution systems. It is the seasoned electrical engineers who have years of experience working with power distribution systems who tend to perform the most accurate assessments. It’s important for facility managers to employ a registered professional electrical engineer who has industry experience with the design, construction, and operation of each piece of electrical equipment (transformers, generators, switchboard, and switchgear, etc.) that will be inspected. This person also must understand how all pieces function and interact. Facility managers must also recognize their role in obtaining an accurate and thorough assessment. The power engineers are responsible for conducting the assessments, but cooperation between the engineers and facility managers is vital to delivering the most accurate assessment possible.

Facility managers need to make sure power engineers have total access to each piece of equipment. Important pieces of electrical equipment often can be located in restricted areas or have hazardous materials blocking access, meaning that the power engineer should be escorted around the facility and provide access. The power engineer may also need access to the equipment’s interior. While power engineers can get a limited view of equipment status by assessing external material, contaminants such as dust, dirt, or water may be permeating the interior of the equipment, and so internal inspections are of the utmost importance in ensuring that engineers get a clear picture of the equipment’s state. Keeping this in mind, facility managers will need to de-energize electrical equipment.

The facilities manager will need to provide the most recent one-line diagrams to the power engineer. These electrical diagrams and other associated documents will provide valuable information concerning each different piece of electrical equipment and will indicate exactly where and how they are connected and operate with other equipment. One-line diagrams provide information about the sources of all electrical power to all loads  within a facility. These drawings and associated electrical documents also outline the operational sequences for each piece of equipment. Creating this holistic view of the system will provide the power engineer with a clear understanding of what within the PDS-affected equipment is least reliable.

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