Electrical Energy Management

Electricity is a powerful form of energy that is essential to the operation of virtually every facility in the world. It is also an expensive form of energy that can represent a significant portion of a manufacturing facility’s cost of production.

This energy management primer is intended to introduce applications that that can be performed by and values that can be derived from a well-designed EPMS (Electrical Power Monitoring System). Additionally, it covers some electricity billing fundamentals, especially focusing on the two major aspects of the electric bill, demand, and energy. This section also highlights key aspects of identifying energy-saving opportunities among major industrial processes and equipment.

Just like any other process in a facility, electrical distribution systems are complex with many devices, and potential detected failures can occur at different locations.

Considering the critical nature of the continuity of an electrical power supply, having the capacity to quickly view, analyze, and understand where the loss has occurred, like our car dashboards, is key for facility managers.

The facility manager needs to:

• Gain visibility of the status and relevant information of the entire electrical system.

• Receive alarms on abnormal conditions or events.

• Monitor and report on peak demand, loading of equipment like transformers, generators, breakers, UPSs.

• Know, analyze, and understand and quickly pinpoint where issues of the electrical distribution network come from.

The Electrical Distribution Monitoring and Alarming application collects data from connected products to provide on-site access to consolidated views of electrical measurements, status information, and individual device details. It also provides remote control actions.

The digital architecture of the Electrical Distribution Monitoring and Alarming application involves collecting the input data from the different products, either directly over Ethernet or via gateways. This data is then used by the local monitoring software package for on-premises visualization analysis and reporting.

A properly designed Electrical Distribution Monitoring and Alarming application includes the following suggested outputs:

Alarms and Events

• Chronological display of alarms/events with sorting and filtering capabilities.

• Intelligent alarm grouping into summary incidents.

• Simplified operator alarm dashboard.

• Remote even notification via email or SMS.

• Disturbance direction detection to help quickly identify the root cause of power quality incidents.

• High-speed waveform capture and analysis.

Trends

• Real-time and historical data can be viewed on a trend viewer.

• Thresholds to indicate when trend is getting close or exceeding a setpoint.

Dashboards

• Configurable dashboards for visualizing historical power system data.

Reports

• Historical data reporting.

Notifications

• SMS notification and/or email can be sent for fast analysis and action.

• Email notifications are also available to send reports and noncritical information.

Analysis Tools

Electrical Distribution Monitoring and Alarming provides an incident timeline with advanced functions:

• Alarm/event data according to their date and time.

• Detailed breakdown and sequence of alarms, waveforms and trends involved in the incident.

• Disturbance direction detection to indicate upstream / downstream root cause of an incident.

Cloud-Based Analytics and Services

As an option, a connected advisory service can perform cloud-based analytics for electrical network health, with recommendations from expert service engineers.

BMS Integration

EcoStruxure Power enables integration of electrical data and alarms at the Edge Control layer with BMS software for better decision making.

One of the leading causes of electrical fires in low and medium voltage installations are non-operational cable power connections, busbars, and withdrawable circuit breakers, in particular when the connections are made on site. A non-operational power connection can lead to an increase of its electrical contact resistance which induces a thermal runaway that can lead, in the worst case, to destruction of switchgear and severe injury to the operator.

Increase of contact resistance can result from:

• Loose connections due to improper installation or maintenance (improper tightening torque, connection loosening due to vibrations).

• Damaged surface (due to corrosion, excessive pressure, excessive friction).

A common remedy is provided by infrared inspections which must be performed manually, are tedious, and only identify issues on a periodic basis.

A properly designed Continuous Thermal Monitoring system provides the following: live data display, alarms and events, notifications, trends, and reports 24/7 without the need for external infrared inspections.

In the past, equipment maintenance for circuit breakers, UPSs, and motors, was performed using a preventative approach. This means, circuit breakers were serviced periodically, typically every one to two years.

By leveraging asset diagnostics data, preventative and condition-based maintenance models can help facilitate maintenance planning to reduce risk of early degradation, optimize maintenance activities and optimize maintenance related spending.

The Facility Manager needs to:

• Move from reactive or preventative to condition based (predictive) maintenance strategies for critical assets like circuit breakers, gensets, transformers.

• Gain visibility into critical assets health and maintain them when necessary.

• Enhance their maintenance strategy with expert services to determine the optimal time to maintain critical assets.

• Streamline and optimize maintenance spending.

This application helps the Facility Manager by providing the following:

Live Data Display

• Circuit breaker asset monitoring diagram (% of electrical and mechanical wear, % of environmental and control unit aging, number of operations, load and temperature profiles).

• UPS monitoring diagrams (measurements, UPS status, battery information, pre-alarms and alarms).

• Power Quality mitigation equipment, generator status diagrams.

Reports and Dashboards

• Circuit Breaker Aging report

• UPS Health report

• Generator Battery Health report

These reports provide the right information to help decide when to maintain circuit breakers, UPSs and generator start batteries.

Many facilities are in a constant state of flux. Areas are being renovated, equipment is being moved, new production lines are brought online, old equipment is being upgraded.

Capacity of the electrical distribution infrastructure must evolve per these changing environments while not exceeding the rating of electrical distribution equipment.

This is a problem for circuit breakers, UPSs, generators, ATSs, transformers, capacitor banks, bus bars, conductors, fuses. Often, exceeding the rated capacity means nuisance trips, but it can also result in overheating or fires.

The Facility Manager needs to:

• Understand the capacity needs of the electrical distribution infrastructure to plan for expansions or modifications of the facility environment.

• Upgrade the facility while not exceeding the rated capacity of equipment and mitigating potential risks to the electrical infrastructure (For example, Nuisance trips, overheating, fires).

This application provides the following for the Facility Manager:

Live Data Display

• Electrical Health diagram

Trends

• Real-time and historical data can be viewed on a trend viewer.

Reports

• Branch Circuit Capacity report

• Generator Power report

• UPS Power report

• Equipment Capacity report

• Generator Capacity report

• Power Losses report

Critical buildings such as hospitals and data centers rely on emergency power systems to supply the facility with power during an interruption of the utility incomer(s). During an interruption, power is transferred from the utility supply to the alternate power source using automatic transfer switches (ATS).

In fact, according to the Electric Power Research Institute (EPRI), backup power systems fail to start 20% to 30% of the time. Common causes include starter battery issues, low fuel levels, wet-stacking, controls in wrong state.

Also, the Joint Commission (also known as JCAHO) requires healthcare facility to test their emergency power supply system monthly with specific guidelines on the test procedure as well as data collection and reporting the results.

The Facility Manager needs to:

• Ensure the reliability and availability of backup power supply systems in the event of unexpected power outages.

• Save time, improve productivity, and ensure accuracy of testing process and documentation per standards or manufacturer recommendations.

Purpose of Backup Power Testing application is to provide the following:

• Centralized remote operator control and testing:

• Remotely test Automatic Transfer Switch transfer, re-transfer and bypass

• Start, run, stop, and cool down emergency generators

• Remotely control Load Banks for engine-generator and UPS loading

• Conduct system test of emergency generator paralleling

• Remotely test Fire Pump Controls emergency power

• Monitor, automatically record and report backup power tests

• Automatic transfer switches

• Back-up generators

• UPS

• Emergency generator paralleling system

• Load Banks

• Fire Pump Control Systems

• Record key legislated parameters for compliance reports including:

• Transfer time for Automatic Transfer Systems and generators.

• Generator run time, engine loading, exhaust and engine temperature, fuel levels and battery health.

• UPS’s ability to sustain critical loads during power outage, and UPS battery health.

• Load bank loading on emergency generator paralleling, engine-generators and UPS systems.

This application provides the following outputs:

Live Data Display

• Animated device diagrams with status and analog values of ATS, generators, power control systems, load banks, fire pump controls system and UPS.

Reports

• Generator Test (EPSS) report

• Generator Battery Health report

• Generator Load Summary report

• UPS Auto-test report

• UPS Battery Health report

• Automatic Transfer Switch performance report

• Utility power outage report

There are many different power quality disturbances which can adversely affect critical or sensitive equipment, processes and buildings. To promote seamless and uninterrupted functioning of these assets, it is very important to continuously measure, understand and act on any power quality issues that could affect uninterrupted operation.

The Facility Manager needs to:

• Understand which power quality events could adversely affect their processes or operations.

• Be able to monitor persistent power quality disturbances.

• Analyze and determine actions needed to correct issues.

Power Quality Monitoring application helps with the following:

• Monitor steady-state and event-based disturbances.

• Harmonics, current unbalance, flicker and over/under voltage conditions, transients, interruptions.

• Better understand power quality disturbances.

• Trends and reports to understand potential issues that could affect operations.

• Capture and study event details such as waveforms.

• Disturbance Direction Detection to locate the directionality of events.

• Deep-dive analysis of power quality issues.

• Advanced dashboards and reports.

• Analytics-based advisory services to improve performance across the system.

The following are the outputs of the Power Quality Monitoring application:

Live Data Display

• Steady state disturbances such as harmonics, unbalance, and frequency, can be visualized in real time.

Events and Alarms

• Onboard events and alarms with timestamps.

Trends

Steady state disturbances such as harmonics, unbalance, frequency can be visualized as trends to monitor their evolution over time.

Analysis Tools

• Power Events Incident Timeline

• Waveform viewer

Dashboards

• Power Quality Status Panel diagrams

• Power Quality dashboards

Reports

• Power Quality report, Power Quality Analysis, and Impact reports.

• Harmonics Compliance report, IEC 61000-4-30 report, EN 50160-2000 and EN 50160-2010 reports.

Cloud-based Analytics and Services

• Cloud-based advisory service can perform cloud-based analytics on power quality data.

Most electric utilities serve a designated geographic territory, largely without other competitors having access to their customers. As such, utility prices have often been set by local, state, or federal regulators, entities that review electric utility costs, revenues, investment decisions, fuel prices, and other factors to arrive at a target rate of return. This approved rate of return, coupled with the utility’s cost structure, determine prices customers pay.

These prices are established in electric utility tariffs, or rate schedules. Rate tariffs are usually established for different classes or sizes of customers. Common class types may include industrial, commercial, residential, municipal, and agricultural. Each customer class may have one or more rate schedules available, and it is common for the electric utility to allow a facility to choose the rate schedule within its class that offers the lowest price.

Electricity Metering

Electric utilities meter both the real and reactive power consumption of a facility. The real power consumption, and its integral -- energy, usually comprise the largest portion of the electric bill. Reactive power requirements, usually expressed in power factor, can also be a significant cost and is discussed later.

Demand

Real power consumption, typically expressed in kilowatts or megawatts, varies instantaneously over the course of a day as facility loads change. While instantaneous power fluctuations can be significant, electric utilities have found that average power consumption over a time interval of 15, 30, or 60 minutes is a better indicator of the “demand” on electrical distribution equipment.

Transformers, for example, can be selected based on average power requirements of the load. Short-duration fluctuations in load current may cause corresponding drops in load voltage, but these drops are within the normal operating tolerances of typical machines and within the design parameters of the transformer.

The demand rate, in $/kW, may also be referred to as a capacity charge, since it has historically been related to the necessary construction of new generating stations, transmission lines, and other utility capital projects. Demand charges often represent 40% or more of an industrial customer’s monthly bill.

“Demand” is the average instantaneous power consumption over a set time interval, usually 15, 30, or 60 minutes.

Load Factor – Demand/Energy Relationship

One useful parameter to calculate each month is the ratio of the average demand to the peak demand. This unit-less number is a useful parameter that tracks the effectiveness of demand management techniques. A load factor of 100% means that the facility operated at the same demand the entire month, a so-called “flat” profile. This type of usage results in the lowest unit cost of electricity.

Few facilities operate at a load factor of 100%, and that is not likely to represent an economical goal for most facilities. But a facility can calculate its historical load factor and seek to improve it by reducing usage at peak times, moving batch processes to times of lower demand, and so forth. Load factor can be calculated from values reported on practically every electric bill:

LF = kWh / (kW * days * 24);

Where LF is Load Factor, kWh is the total energy consumption for the billing period, kW is the peak demand set during the billing period, and days is the number of billing days in the month (typically 28-32). “24”, of course is the number of hours in a day.

Time-of-Use customers may prefer to track load factor only during on-peak time periods. In that case, the kWh, kW, days, and hours/day in the formula are changed to reflect the parameters established only during the on-peak periods.

Typical load factor for an industrial facility depends to a great degree on the number of shifts the plant operates. One shift, five-day operations typical record a load factor of 20-30%, while two-shifts yield 40-50%, and three shift, 24/7 facilities may reach load factors of 70-90%.

Power Factor

The relationship of real, reactive, and total power has been introduced previously, and described as the “power triangle”. For effective electricity cost reduction, it is important to understand how the customer’s electric utility recoups its costs associated with reactive power requirements of its system. Many utilities include power factor billing provisions in rate schedules, either directly in the form of penalties, or indirectly in the form of real-power billing demand that is higher than the actual measured peak.

Even if a utility does not charge directly for poor power factor, there are at least three other reasons that a customer may find it economical to install equipment to improve power factor within its facility, thereby reducing the reactive power requirements of the utility:

• Reduce power factor penalties.

• Release capacity of an existing circuit.

• Reduce heating losses associated with power distribution (often called I²R losses).

• Improve voltage regulation.

Fixed capacitor banks are best suited for use on electrical systems with no voltage or current harmonics. In the presence of harmonics, Active Harmonic Filters (AHF) are a better solution.

An important initial step in evaluating energy saving opportunities is to estimate both:

• The contribution to peak billing demand, and

• The amount of energy consumption.

Of each major load or process within the facility being evaluated.

This Facility Energy Profile helps to focus the energy optimization efforts on those processes or loads that have the most savings potential. This profile also may identify batch processes or discretionary loads that may be scheduled at times of low demand for the rest of the facility, or during times of off-peak utility prices.

The Facility Energy Profile identifies the major energy consuming processes and equipment in the facility.

The FEP is best developed using actual power measurements from existing facility-wide monitoring systems. Some types of loads, lighting, for instance, may comprise part of the usage of every major circuit in the facility. This fact would suggest that the meter measuring the power consumption of a feeder serving the building’s centrifugal water chillers.

Actual power monitoring data from existing Circuit Monitors measuring the power consumption of individual feeders is the best basis for establishing the Facility Energy Profile.

Demand analysis is the methodology used to determine if there are opportunities for a given facility to reduce peak demand charges. Demand analysis involves manipulation of historical demand interval data to determine which major processes or loads are operating at times of highest demand; how “steep” or “flat” the facility’s load profile appears; and what times of day these peaks are occurring. Armed with this information, the energy auditor can better evaluate the potential for a variety of demand reduction techniques.

The Demand Sort Table is produced by rearranging individual integrated demand readings for a given billing period. Meters record demand readings chronologically, 3000 or so readings for a 30-day billing period at 15-minute demand intervals; the demand sort utilizes a software tool to distribute the readings from highest to lowest, so that times and values of peak usage are easily analyzed.

The Demand Sort Table facilitates demand analysis by depicting the number of intervals (or hours) during which the plant’s peak electrical demand exceeded certain levels.

Using the Demand Reduction Table, the engineer can determine that a reduction in peak demand to 2200 kW at this example facility would have required a demand reduction of 122 kW for 25 fifteen-minute intervals, or 6.25 hours, in August of the sample year.

Peak-day Load Profiles from actual power monitoring data can show consistency, or, as in this case, a single-day aberration in peak demand that set the demand minimum billing level (ratchet) for the remainder of the year.

Demand controls systems are available that perform these basic functions:

• Measure power consumption (demand) in real time.

• Predict demand level based on rate of instantaneous usage.

• Compare predicted value to target setpoint.

• Transmit signals to pre-determined equipment to turn off or curtail power usage if demand is predicted to exceed target kW.

These demand controls systems are intended to reduce peak demand for a facility to some predetermined level.

The design engineer’s foremost demand control system challenge is to identify loads in the facility that can be controlled effectively. Ideal load candidates include those machines or processes that are (1) currently contributing to the facility’s load at peak times, and (2) whose function can be delayed or curtailed at times of peak.

Most facilities lack equipment or processes that fit this ideal description, despite the numerous machines and processes that may be operating at peak times. In fact, successful demand control is usually the exception rather than the rule.

One common candidate for the demand control system is the air conditioning system. Buildings equipped with multiple packaged direct-expansion air conditioning systems are typical targets of demand control sales efforts. Unfortunately, demand control of air conditioning compressors usually leads to loss of temperature or humidity control within the conditioned space, or lack of demand savings.

The reason for this paradox is twofold. One, natural diversity among multiple air conditioning compressors maximizes the chance that all compressors are not operating at full load at the same time. Strangely, this fact is often highlighted in the demand control system sales pitch: “Not all compressors are running at the same time, so you should turn some off for short periods of time”.

Secondly, basic thermodynamic principles of moist air and vapor-compression refrigeration systems require compressor power consumption to reduce air temperature and condense moisture. This process is controlled by thermostats and humidistats within the facility. When cooling or dehumidification is removed or reduced at times when these devices are “calling for” them, temperature and humidity rises in the conditioned space.

So, if not air conditioning equipment, what loads have been successful demand control candidates? An electrolysis process providing chemicals for a paper mill was able to reduce peak demand and flatten the demand profile for the overall facility. A battery-charging system for forklift vehicles in an automotive facility could produce real demand savings during peak times. Finally, a large induction furnace melting scrap metal proved to be an effective candidate for the rolling mill at a steel plant.

Chilled Water Supply and Return Temperatures increase over the course of a day due to demand control of inlet guide vanes on a centrifugal water chiller. Space conditions could not be maintained because of the demand control.

How, the engineer might ask, can a facility save money by producing their own energy (PV, battery, diesel generator.) that costs more per kWh than the energy they purchase from the utility? Very carefully, is the expected – and accurate - response.

The key to economic peak shaving is to understand and optimize the demand savings associated with onsite generation operation. That is, the onsite generation must be operated the absolute minimum time necessary to reduce peak demand the maximum amount. Because the overall average unit price of electricity is not necessarily equivalent to the effective price of electricity at the plant’s peak.

For example, the facility that pays an overall average unit price of 8 ¢/kWh probably pays only about 3-4 ¢/kWh for actual energy consumption, yet an additional $10-$20/kW for demand. At the end of the month, the total billing amount divided by the total kWh usage might yield 8 ¢/kWh average, but the actual cost of power at its peak – when demand charges are included – may equate to an effective unit price of 20 ¢/kWh or higher. For the facility with a sharp demand peak, when the peak for the month is set in a few hours or less and the remainder of the time demand is low, peak-shaving at 12 ¢/kWh can be preferable to paying 20 ¢/kWh.

Costs of Generated Power

Onsite generators typically utilize natural gas, wood, fuel oil, or steam derived from a fossil fuel or as a part of a production process. Unit fuel costs for fossil fuels are usually calculated based on the fuel’s heating value, an estimated efficiency of the generator system, and the fuel cost.

Cost/kWh = fuel price/gal * 3413 / HV / efficiency

In the equation above, HV is the heating value of fuel oil in BTU/gal, and 3413 is the conversion from BTU to kWh. Internal combustion diesel generators typically range in efficiency from 25-30%.

For a typical example, #2 fuel oil may be burned in an IC engine. For a fuel-oil price of $3.00/gal, and a generator efficiency of 25%, the fuel cost/kWh is:

Cost/kWh = $3.00 * 3413 / 108,000 BTU/gal / 0.25

Cost/kWh = 38 ¢/kWh.

Obviously, peak-shaving is much less attractive at a fuel cost of $3.00/gal, unless required generator operation can be predicted accurately and electricity charges are comparably high as well.

Utility Rates Affecting Peak-shaving Generation

Electric utility rates must be analyzed carefully prior to implementing peak shaving or cogeneration opportunities. Some utilities have special interconnection and protective relaying requirements so that onsite generation does not pose a safety hazard for utility workers. In addition, many utility rate schedules impose standby charges for onsite generation.

These charges are intended to recoup the utility’s investment in transformers and other equipment necessary to serve the facility’s entire load when the onsite generation equipment is not operating. Without this standby equipment, utilities often reserve the right to replace service equipment with smaller facilities, at risk to the facility of overloading the smaller equipment when onsite generation is not operating.

Facilities with onsite generation may be able to operate this equipment to reduce purchased power requirements during periods of high demand, or high utility prices.

Savings, or losses, associated with operation of peak-shaving generators is dependent on fuel prices, on-peak electricity prices, the amount of time the generator must operate for a given peak-reduction target, and, most importantly, the accuracy with which plant personnel can predict these variables.

Electricity generation and peak shaving can also be accomplished with steam cogeneration systems typical of paper mills, refineries, and other large industrial processes.

WAGES is the acronym for the complete power and energy monitoring system in a typical industrial facility. Industrials are concerned about the costs of Water, Air (compressed), Gas (natural gas), Electricity, and Steam. These systems are often interrelated to the degree that reductions in one utility can increase usage in another. The power monitoring system used by industrials must have the capability of monitoring each of these parameters accurately, and of posting this information in a common, preferably web-based, format for use by the local site and by remote engineers and managers.

Web-based power monitoring systems allow energy managers to monitor all their utilities (Water, Air, Gas, Electricity, Steam) and verify the results of their energy reduction techniques to facilitate identification of new opportunities. Such systems can also convert the energy consumption to dollars by applying a tariff.