By: Brent Purdy and David Saenz, Automation Direct

Introduction

Is your facility plagued by high energy costs, frequent nuisance trips, and repeated asset failures? Power monitoring could be just solution you need. Without data, it’s impossible to make informed decisions. After all, you can’t fix it if you can’t see it. Power monitors, or power quality analyzers, deliver simple, actionable insights.

Power monitoring can be used to identify common power problems. It can help organizations minimize unscheduled downtime, reduce premature equipment failures, and lower the time and money spent on maintenance. In manufacturing, power monitoring can be used to improve productivity and quality. It can help data center operators meet service-level agreements. Last, but definitely not least, power monitoring can lead to substantial savings in overall energy costs. Whether you’re running a factory, a process facility, or an AI data center, power monitoring is an essential technology.

Tools and techniques

To get a holistic picture of a facility’s power, install monitors/meters at both the distribution (panelboards and switchboards) and at the distributed loads (industrial control panels, motor control centers (MCCs), and drives). Functionality varies but devices typically measure parameters like voltage, frequency, current, active power (kW), reactive power (kVAr), apparent power (kVA), and power factor. Meters frequently also calculate quantities like active energy (+kWh) and reactive energy (+kVArh). Many devices also perform harmonic analysis to determine total harmonic distortion (THD; see Figure 1).

Figure 1: The Socomec DIRIS A20 is a configurable panel-mounted power meter that gives easy access to key metrics like current, voltage, power factor, energy, and THD.

Power meters need to be installed by an electrician but the process is straightforward. These devices are  often bundled with software tools for ease of configuration. Cloud-based versions can store and analyze data off-site for ease of use and remote access.

Power monitoring in action

Idle/standby energy waste

One of the easiest and most effective applications of power monitoring is to identify equipment that is kept running continuously, even when not performing work. Think pumps or fans left on overnight, or air compressors running unloaded. Idle/standby energy waste is frequently caught by energy monitoring during audits and can add up to big savings This represents low hanging fruit that can provide some easy wins to help build momentum for instrumenting more broadly across the facility.

What you see: Significant energy consumption (kWh) during nights/weekends

Corrective actions:

• Implement shutdown procedures for idle equipment.
• Add automatic controls (timers, occupancy sensors, PLC interlocks, etc.).
• Use variable frequency drives (VFDs) to match the operation of pumps, fans, and compressors to demand, rather than running them at top speed and using a mechanical valve/choke to adjust output. VFDs can extend motor lifetime and provide energy savings when sequenced effectively.

Inrush current on motor startup

Current draw in the first few milliseconds of AC induction motor operation, while windings are being energized, can be up to 10 times as high as steady-state current. High inrush current on large inductive loads can lead to voltage sags that can impact other equipment throughout the facility.

What you see: High current (A) inrush events recorded during startup

Corrective actions:

• Add soft starters or VFDs. These devices suppress inrush current, decreasing the magnitude of the voltage sag seen by other devices.
• Oversized motors, a common design flaw, draw excessive current. Check motor specifications with your vendors to be sure that they are sized appropriately.

High peak demand/load profile spikes

Utilities frequently scale energy rates for industrial customers by maximum peak demand for a given time interval. Depending on the circumstances, just a few load spikes could affect energy pricing for an entire quarter.

What you see: Demand graph showing sharp peaks during shift start, motor startups, or batch processes

Corrective actions:

• Stagger equipment startup times.
• Use soft starters/VFDs on large motors to reduce inrush currents.
• Apply demand control systems to shed or shift non-critical loads to off-peak hours with lower rates.

Poor power factor (Low PF < 0.9)

Power factor (PF) is the ratio of the real power absorbed by the load (kW) to the apparent power flowing in the circuit (kVA):

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Power factor is essentially a measure of how effectively an electrical system converts power into work. A good analogy for power factor is a glass of beer. The total glass of beer represents the apparent power – the total power supplied by the utility. The beer in the glass represents real power – the part that does useful work (like quenching your thirst). The foam symbolizes the reactive power – it takes up space in the glass, adding to apparent power, but does no useful work.

Power factor is a key metric for assessing efficiency. A power factor PF < 0.9 means that the electrical system is wasting power, which affects utility costs in two ways. First, there’s the obvious expense of inflated apparent power, but in addition, utility companies typically assess a surcharge on facilities with power factors below a specified level, to compensate for the cost of supplying excessive reactive power. The lower the power factor, the higher the surcharge; depending on the operation, this recurring surcharge can be substantial.

Low power factor stresses equipment, shortening lifetime. It increases line losses and voltage drop. It can also cause transformer heating and lead to wasted capacity in transformers/cables.

Correcting the problem starts with identifying it. Power meters generally offer power factor functionality (see Figure 2).

Figure 2: In addition to basics like current and voltage monitoring, the Trumeter ADM100W-HPS graphical power meter includes advanced functions like power factor, THD, and energy monitoring. Modbus connectivity provides expanded reading of data values, like phase angle or alarm(s).

What you see: Low power factor reading due to inductive loads (motors, welding processes, HVAC)

Corrective actions:

• Install capacitor banks or active harmonic filters..
• Add synchronous condensers (synchronous motors whose shafts are not connected to a load) to cancel out lagging PF.
• Use VFDs with active front ends or 12-pulse or 18-pulse rectifiers.

Voltage transients – sags/dips, surges, and swells

The term voltage transient refers to variations of voltage levels supplied to a load as a result of the startup, shutdown, or operation of another load on the distribution system. Voltage sags, or dips, are defined as a drop of 10% to 90% from steady-state voltage. Voltage swells and surges are voltage increases classified by duration: Voltage surges involve brief (microseconds to milliseconds) spikes, while voltage swells can last for as long as a minute.

Voltage transients can have a variety of negative outcomes ranging from nuisance trips to premature failure of equipment. The damage from voltage spikes, in particular, can be both immediate and also cumulative, degrading and damaging equipment over time. They can also reduce product quality and throughput, impacting OEE.

What you see: Dips when large motors start, or spikes when equipment shuts off

Corrective action:

• Add motor soft starters or VFD ramping.
• Use uninterruptible power supplies (UPS) for critical loads.
• Install surge protection devices (SPD) on main panels.
• Upsize transformers or drives to reduce current draw.
• Stage startups of problem equipment or diversify feeder circuits for critical or problematic loads.

Harmonics and total harmonic distortion (THD)

Total harmonic distortion (THD) refers to the degradation of a perfect sinusoidal voltage or current waveform as a result of higher-order harmonics. THD is effectively a measure of how distorted or “dirty” the power is with respect to the reference sinusoidal wave. Common sources of harmonics include nonlinear loads such as VFDs, switching power supplies, and LED or fluorescent lighting. This isn’t just a problem for factories. Data centers are filled with nonlinear loads, including servers, UPS, and the VFD-driven AC induction motors that power the HVAC units.

High THD can lead to overheating and premature failure of assets, as well as strange behavior and premature failure of sensitive equipment like PLCs. It can also decrease power factor and introduce voltage transients. For more information on THD levels and their impact on distribution systems and equipment, see IEEE 519.

What you see: High harmonic distortion from drives, servers, UPSs, LED lighting, welders, etc.

Corrective actions:

• Install harmonic filters (passive or active).
• Use 12-pulse or 18-pulse drives where possible.
• Use K-rated or harmonic-mitigation transformers to keep loads that are sensitive to high THD on dedicated circuits.
• Balance loads by putting nonlinear loads and other troublesome assets onto different circuits.

Voltage imbalance/unbalance

Voltage imbalance refers to the differences between the phase voltages in multi-phase electrical systems or networks compared to the average voltage. On motors, a voltage imbalance of 2% or more can cause overheated windings, premature failure, and performance degradation such as counter torque. On transformers, unbalanced loading can lead to hot spots and overheat windings, which may cause premature failure. In addition, voltage imbalance can lead to current imbalance, a problem in its own right.

What you see: Unequal line-to-line voltages (typically >2% imbalance)

Corrective actions:

• Redistribute loads between phases.
• Inspect supply transformers for tap settings or winding issues.
• Fix loose or corroded connections.

Current imbalance/overloaded circuits

Current imbalance refers to differences in the phase currents for each phase of a three-phase system compared to the average. In three-phase motors, current imbalance can cause overheating, torque variations, and premature failure. But it’s a bigger problem than that. In the three-phase power system running the facility, even modest current imbalances can raise neutral currents. It can create problems across the entire facility, for example overheating panels and transformers, particularly if the system already has high THD.

IEEE 141 recommends current imbalances of <5% for small industrial facilities and <4% for large facilities, noting that for some sensitive equipment, even 2% is too much.

Current imbalance has a variety of causes ranging from unbalanced loads in the distribution system to loose or corroded contacts.

What you see: One phase of a three-circuit carries much higher current

Corrective actions:

• Rebalance load distribution across phases.
• Identify failing motors or drives pulling uneven current.
• Upgrade wiring or breakers if they are consistently overloaded.
• Fix loose or corroded contacts.

Conclusion

It’s easy to assume that power issues are caused by the utility and there’s nothing to be done about it. In reality, many power quality issues, and the headaches they create, originate within the facility and can be corrected – once they’re identified. Power monitoring makes the invisible visible through granular data that reveals exactly what’s going on. The insights it delivers can slash energy costs through eliminating waste peak demand and power factor penalties. Power monitoring can help identify troubled assets and prevent productivity-killing repeat failures and the costly downtime they cause. Most fixes are straightforward, such as load balancing, filtering, improving controls, or making equipment upgrades like switching to VFDs. From factories to process industries to the AI data centers springing up around the world, power monitoring can improve efficiency, reliability, and profitability. Find out more at wtwh.me/powerquality.

About the authors

Brent Purdy is product manager, and David Saenz is product engineer, for the Power & Circuit Protection at Automation Direct.

Tips for Getting Started

1. Design power monitoring systems into expansions and new builds – it’s easier to include in the budget upfront.
2. For retrofits, look for an internal champion to help drive the initiative.
3. Emphasize that data from meters will reduce unscheduled downtime and speed troubleshooting in the event of failures. This can be used to justify the expense of installing the monitors and fixing the system.
4. Don’t try to instrument the entire floor all at once – look for low-hanging fruit where you can get short-term wins. Examples include assets that fail frequently, and equipment subject to nuisance trips.
5. Conversely, you do need enough granularity to obtain actionable insights – one power meter at the main might be able to show a general problem but won’t help with troubleshooting.
6. Tap the expertise of your vendors and integrators. They’ve guided other organizations through this transition.