PowerMonitor 5000 Family Advanced Metering Functionality

Steve Lombardi, Rockwell Automation

The PowerMonitor™ 5000 is the new generation of high-end electrical power metering products from Rockwell Automation. This new family of power monitors provides advanced technology, new functionality, and market leading capabilities in response time and accuracy.

The PowerMonitor 5000 family provides three levels of functionality: the M5, M6, and M8. The 5000 M5 is the base model and provides an extensive range of basic metering functions. The 5000 M6 and 5000 M8 add additional metering and power quality capabilities. Rockwell publication 1426-WP001, “PowerMonitor 5000 – The Next Generation,” discusses the new, underlying technologies in the PowerMonitor 5000 M5 and compares it to the technology in the PowerMonitor 3000 M5. This publication focuses on the base functionality in the 5000 M5 and how the 5000 M6 expands the metering and power quality capabilities.

PowerMonitor 5000 M5 Metering FunctionsThe PowerMonitor 5000 M5 provides the following metering functions:

• Frequency

• Phase rotation

• Voltage, per phase and average, line-to-line and line-to-neutral

• Voltage, neutral-to-ground

• Current, per phase and average

• Current, neutral or ground

• Power/energy/demand (real, reactive, and apparent), meets class 0.2% accuracy for both ANSI C12.20 and EN 62053-22

• Power factor, true and displacement

• Symmetrical component analysis values for both voltage and current

• Voltage and current unbalance

• Crest factor

• THD for both voltage and current

• K-factor

• Direct connect to 690V AC

• Data Logs (add logs supported)

• ADD (definition of increased volume for logs)

2 | PowerMonitor 5000 Family Advanced Metering Functionality

The 5000 M5 metering functions are updated every line cycle. The fast, accurate readings are excellent for monitoring power system conditions, monitoring energy usage, and controlling industrial manufacturing systems based on the measured electrical data. In addition to the real-time data, there are also numerous logs available to provide historical information.

With the PowerMonitor 5000 M5, you can configure up to 10 setpoints to identify when a measured parameter goes above or below a set threshold. Whenever a setpoint is activated, the event time and the measured parameters pertinent to the event are recorded in a log. The setpoint capability transitions a status bit and can be used to actuate a relay output for control purposes or to identify an abnormal condition. In addition to the user-configurable setpoints, the 5000 M5 provides status bits that identify the occurrence of a voltage sag or swell condition.

The PowerMonitor 5000 uses an internal clock to time-stamp the metered values, the occurrence of a setpoint event, and all data log entries. To improve consistency between clocks in multiple power monitors or with the utility, the clock can be sourced by an SNTP time source. For the ultimate in clock synchronization, the PowerMonitor 5000 can use the IEEE 1588 precision time protocol over Ethernet. This provides very precise synchronization among all of the participating meters.

There are two time elements to consider when evaluating time protocol; relative time accuracy and absolute time accuracy. Relative accuracy is the time error between different devices on the network. Absolute accuracy is the time error between a device on the network and a precision reference clock such as a GPS clock. The IEEE 1588 precision time protocol lets devices on the network determine the highest quality clock available and to use that clock to source time to all participating devices.

A PowerMonitor 5000 can be used as the clock source if absolute accuracy is not required. Excellent relative time accuracy between devices on a properly designed network results by using the IEEE 1588 protocol. When synchronization is required between geographically separate meters or with the utility, absolute accuracy depends on source clock quality. A GPS clock source with IEEE 1588 capability provides very precise time to the power monitors on the network for excellent relative accuracy and absolute accuracy. If neither relative nor absolute time accuracy is required, use the PowerMonitor 5000 local clock.

PowerMonitor 5000 M6 OverviewThe PowerMonitor 5000 M6 retains all functionality of the 5000 M5 plus the following:

• Additional setpoint capability

• User configurable voltage sag/swell settings

• A power quality log that details detected sag/swell events, oscillography, and harmonic analysis

• IEEE 519 pass/fail capability

• Ability to synchronize detected events between multiple power monitors

If a user has a PowerMonitor 5000 M5 and wants the additional functionality of the 5000 M6, the M5 can be field upgraded to a M6 by purchasing a firmware upgrade.

PowerMonitor 5000 Family Advanced Metering Functionality | 3

PowerMonitor 5000 M6 New Setpoint CapabilitiesThe 5000 M6 improves how to identify and capture power system issues by increasing the number of configurable setpoints from 10 to 20 so more conditions are identified and more control options are provided. The 20 setpoints in the M6 includes two new types of setpoints, relative setpoints and logical setpoints.

Relative setpoints are similar to standard setpoints except for the definition of the reference value. A fixed reference value is specified when a standard setpoint is defined. For example, a setpoint in a 480 VRMS system can be defined to activate when the measured voltage is less than 90% or 432 VRMS. However, the nominal utility-supplied voltage level can vary by the time of day due to power system loading changes. If you wish to identify a reduction to 90% of the actual supplied voltage, then a fixed reference voltage cannot provide the intended result; a relative setpoint must be used. In this example, a rolling average of the utility-supplied voltage is computed over a sliding interval with user configured duration. The rolling average value is now used as the reference value for the setpoint. If the rolling average of the actual supplied voltage falls to 460 VRMS the 90% value now becomes 414 VRMS. The choice between a fixed setpoint and a relative setpoint gives you the ability to identify when the system hits a “critical” value or to identify when an unexpected change in the system occurs.

The PowerMonitor 5000 M6 also sets logical setpoints, which use the results of other user configured standard or relative setpoints as inputs. The configuration uses one level of logic with up to four inputs. The logic supports AND, NAND, OR, NOR, XOR, and XNOR logic functions. The output of the logic function is a setpoint result that can be used in the same manner as other setpoint results. Logical setpoints allow users to create a more complex condition for creating a setpoint action.

Power Quality Phenomena per IEEE 1159The PowerMonitor 5000 M5 provides a considerable amount of metering data so you can monitor the operating condition of their facility’s power distribution system and thus manage their energy costs and consumption. To further increase the efficiency and robustness of the power system and the reliability of the control systems connected to it, monitor the system should also be monitored for power quality issues. A good reference for defining and categorizing power quality phenomena is IEEE 1159-2009, IEEE Recommended Practice for Monitoring Electric Power Quality. This document categorizes power quality events and conditions into seven different types with various sub-types where appropriate. The main categories are:

• Transients

• Root-mean-square (RMS) variations (short duration or long duration)

• Imbalance

• Waveform distortion

• Voltage fluctuation

• Power frequency variation

A transient is a very short event with a typical duration between 5 micro-seconds and 50 milliseconds. Transients are usually characterized by either rise time or frequency, and they are either impulsive or oscillatory. Transients are typically the result of lightning strikes, system switching events, fault conditions, or intermittent connections.

4 | PowerMonitor 5000 Family Advanced Metering Functionality

Short duration RMS variations are events characterized by voltage magnitude changes between 10 percent and 180 percent of their nominal value. Changes that result in a voltage less than normal are defined as “sags” and changes that result in a voltage greater than normal are defined as “swells.” Typical duration is between one-half cycle and one minute. Voltage sags in a power system can be caused by a variety of conditions such as: a fault to ground or another phase either directly or through some impedance, circuit breaker/re-closer operation, a blown fuse, the energization of a large load, the removal of power factor correction capacitors, an overloaded conductor, or a poor connection. Voltage sags that result in a level less than 10 percent of normal are referred to as interruptions. Voltage swell events are typically the result of a fault to ground or another phase either directly or through some impedance, a blown fuse, the de-energization of a large load, the addition of power factor correction capacitors, or a poor connection. Voltage level changes that have similar magnitude changes but last longer than one minute are referred to as sustained interruptions, over-voltages, or under-voltages.

In addition to these power quality issues, IEEE 1159 also defines “steady state” power quality concerns. The presence of an unbalance condition, voltage or current, is one of these concerns. This condition is only defined for three-phase systems and occurs when the voltage magnitudes and phase angles for each of the phases are not equal. The imbalance percentages represent the ratio of the negative sequence component to the positive sequence component as derived through symmetrical component analysis. Voltage and current imbalance are usually the result of uneven distribution of single-phase loads on a three-phase system or a blown fuse. Imbalance conditions adversely affect AC induction motors by producing excess heat in the rotor winding and causing premature failure, by creating unwanted torque oscillations causing possible motor bearing failure, and a reduction in full-load torque capability. Imbalance conditions also create excess current in the neutral conductor of a three-phase wye system.

Waveform distortion is comprised of any DC offset that can be present, such as harmonics or inter-harmonics, line notching, and broadband noise. DC offset is a concern because it results in magnetic saturation and unwanted heating of motors and transformers. The causes of DC offset are half-wave rectification and geomagnetic interference. Harmonic AC voltages or currents have a frequency that is an integer multiple of the fundamental frequency. Harmonic currents are caused by non-linear loads on the power system. These are typically variable frequency drives, switched-mode power supplies, or other power electronic switching devices. Harmonic voltages result from harmonic currents flowing through system impedances. The effects of the harmonic current can be transferred to other parts of the power distribution system and the loads connected to it by the resulting harmonic voltage. Inter-harmonics are voltages or currents at frequencies that are not integer multiples of the fundamental frequency. Inter-harmonics are caused by static frequency converters, cyclo-converters, induction furnaces, arc furnaces, and arc welders. Both harmonics and inter-harmonics result in the overheating of conductors, power factor correction capacitors, AC induction motors, chokes, and transformers. Extra care must be exercised when power factor correction capacitors are present. The interaction of the system inductance, capacitance, and one of the frequency components can create a resonant condition with uncontrolled voltage and current oscillations that can damage equipment and shut down the power distribution system.

The presence of harmonics and/or inter-harmonics can also disrupt communications and control information. An additional voltage waveform distortion issue is line-notching. Notching occurs due to line commutation of SCRs used in three-phase to DC converters. When the current through the SCR commutates to zero, there is a short instant of time where a line-to-line short occurs. The depth and duration of the notch is a function of the actual commutation time and the system impedance. The Total Harmonic Distortion (THD) calculation is one method used to detect the presence of line notching. However, this is not completely reliable because the harmonics in the system can be created by other

PowerMonitor 5000 Family Advanced Metering Functionality | 5

factors besides notching. Line notching is also easily identified by inspection of the time domain waveform.

Voltage fluctuation (also known as “flicker”) is either systematic or random changes in voltage magnitude, which are typically in the range of ± 5% of the fundamental magnitude and occur within a frequency range that goes from about two-thirds of the fundamental frequency to just over DC. Then the voltage waveform usually appears as a modulated fundamental frequency similar to an AM radio signal. Analogous to harmonic voltage distortion, voltage fluctuations are caused by the resulting voltage drop from load current passing through the system impedance. Any load that has significant current variation can cause voltage fluctuation to occur. The voltage fluctuation is the actual electromagnetic phenomena. Voltage fluctuation of this magnitude is of little concern to the operation of the power system. However, the fluctuation can cause variation in the light output of lamps energized by the power system. When the variation occurs at an appropriate level and frequency, the variation in light output becomes perceptible and irritating to people. It is this perceptible variation in light output that is called flicker. When the flicker occurs at the right frequency, it can induce seizures in some individuals. Because the variation of the light intensity is the real item of concern, voltage fluctuation is only defined for the typical lighting circuit voltage of 120V or 230V AC. The most common cause of voltage fluctuation is arc furnaces. Analysis of the voltage fluctuation involves computing a human perceptibility index to indicate the level of human sensitivity. The

actual computation of the index is a fairly complicated procedure that models the sensitivity of the human eye to how the light output varies with voltage fluctuation.

System power frequency is set by the rotational speed of the generators supplying the system. As the load on the system changes, small variation in generator speed can occur, which is power frequency variation. These instantaneous changes occur constantly but any changes that exceed the established limits are usually caused by faults on the utility power transmission system, a significant generation source going off-line, or a large block of loads being disconnected from the system. Significant frequency variation is rare in today’s interconnected power grid. Power

frequency variations are more common when a power distribution system is supplied by local generation that is not connected to the grid (islanded).

New PowerMonitor 5000 M6 Power Quality FunctionsThe PowerMonitor 5000 M5 provides an alarm bit for when a voltage sag or voltage swell occurs. The threshold is fixed at 90 % of configured nominal voltage for sag and 110% for swell. When one of these events occurs, the associated alarm bit is set and maintains for 90 seconds after the system voltage has returned to normal. No other data is available regarding the event. The 5000 M6 model expands on this capability by addressing the most common power quality events identified by IEEE 1159. The 5000 M6 provides five configurable threshold values for voltage sags and four values for voltage swells. The following are recorded in the Power Quality Log when a sag or swell is detected:

• The event time

• The event duration

• The configured threshold

• The minimum sag value or the maximum swell value

The PowerMonitor 5000 M6 expands on the 5000 M5 capability by addressing the most common power quality events identified by IEEE 1159.

6 | PowerMonitor 5000 Family Advanced Metering Functionality

The additional data helps you to more fully understand the event that affected the power system and if any action is needed to minimize the effect of a similar event in the future. The data also provides sufficient information to classify the event per the IEEE 1159 recommended practice discussed above.

The PowerMonitor 5000 can implement the IEEE 1588 Precision Time Protocol over its EtherNet I/P network connection. With an appropriately designed network, the metering results from multiple meters can be precisely aligned in time. This capability lets you determine a very precise sequence of events to see how a power quality event propagates through the power distribution system. The meters can be in a local facility or they can be dispersed across multiple geographic locations. For dispersed meters GPS satellite receivers are used to supply the time clock. The ability to provide precisely aligned measurements is further enhanced by a unique feature of the PowerMonitor 5000 M6. The monitors can be configured to alert other monitors in the system whenever a power quality event is triggered. Upon receipt of the alert the other monitors use the embedded time stamp to capture their local conditions at that point in time. The data is stored in each monitor’s power quality log and waveform capture log even if the local magnitude of the event was not sufficient to activate the locally configured trigger. This ensures that when an event occurs, a complete “system” picture is captured and an enhanced view of system performance is obtained.

The parameters recorded during a power quality event are useful for quantifying, categorizing and analyzing the event. However, a visual image of the waveforms before, during, and after the event provides valuable additional information. The waveform shape and its relation to the other waveforms at a particular device and across the power distribution system provides additional diagnostic information to help you analyze an event to determine what caused it and how to prevent it in the future. When a short or long duration RMS voltage variation occurs or when a manual waveform capture command is issued, the PowerMonitor 5000 M6 automatically records the waveforms for the three phase current inputs, the neutral or ground current

input, the three phase voltages, and the neutral to ground voltage. The number of cycles captured before and after the event is user configurable. The complete duration of the event is recorded unless the detected event lasts longer than one minute. In that case, it is considered a steady-state condition and the waveform can stop recording. However, the end of the event can still be recorded in the power quality log.

A waveform record can consist of multiple events. For example, a sag event where the voltage decreased to 90% of nominal triggers a power quality event and starts a waveform capture. Before the event ends, a second sag event occurs where the voltage decreased to 80% of nominal. The second sag is considered to be part of the same event and the waveform capture can contain both events. Whenever a waveform capture is in process, it can be extended to include subsequent events as long as the subsequent events occur before completion of the post-event capture or the one minute limit has not been reached, whichever occurs first. In addition to short or long duration RMS voltage variations, a waveform record can also be trigger by receiving an alert from another PowerMonitor 5000 in the system. This capability is used to obtain a system wide waveform capture from every monitor in the system, regardless of whether or not a trigger threshold occurred at every location, when an event occurs at one or more locations in the distribution system. To take advantage of this capability, the Precision Time Protocol mentioned earlier must be configured and operating.

PowerMonitor 5000 Family Advanced Metering Functionality | 7

The PowerMonitor 5000 is capable of recording a large number of waveforms. The exact number of waveforms varies based on the cumulative duration of the events recorded. Additionally, when Rockwell Automation’s FactoryTalk® EnergyMetrix™ software is used to configure and extract data from the monitors, it automatically detects when there are waveform records available and download them from the monitors. This lets individual monitors maximize their waveform capture capabilities and create virtual infinite storage ability. Factory Talk EnergyMetrix software acquires all waveform information from different monitors, properly align the waveforms, and provide a unified display of them. The software can also be used to create various types of reports, such as monthly/annual consumption or power quality reports.

The PowerMonitor 5000 M6 also measures the harmonic content of the voltage and current inputs up through the 63rd harmonic. This measurement is computed and updated every line cycle. The measurement data provides both the magnitude and angle for each of the

harmonics, the total harmonic distortion (THD), and the power flow at each harmonic. This lets you analyze the harmonic content to determine what harmonics are present and whether or not they are of sufficient magnitude to cause issues in your power distribution system. If action is warranted, you can install filters or other mitigating technologies to reduce the problematic harmonics and then verify the effectiveness of the solution.

The harmonic information is also used to measure compliance to the requirements of IEEE 519, Recommended Practices and Requirements for Harmonic Control in Electrical Power Systems. The intent of IEEE 519 is to provide recommended limits for the level of harmonic current injection due to loads at your facility and to provide recommended limits for the level of harmonic content present in the voltage supplied by the utility. The measurement of these two quantities is to be made at the point of common coupling (PCC) between the utility and you. The PCC is usually defined as the location in the power distribution system where the utility meters are connected.

IEEE 519 is not intended to be applied to individual loads or groups of loads in your facility. Rather, IEEE 519 provides limits to the total amount of harmonic content and to the magnitude of individual harmonics. There are different limits for short term and long term intervals. When properly configured, the PowerMonitor 5000 uses the measured harmonics to provide a pass/fail indication for the limits in IEEE 519. The monitor also provides detailed information so you can precisely determine the limits that are being exceeded.

Harmonic Number

Perce

nt of

Fund

amen

tal

Publication 1426-WP002A-EN-P – October 2013 Copyright © 2013 Rockwell Automation, Inc. All Rights Reserved. Printed in the U.S.A. Supersedes Publication XXX-XXXXXX-XX-X – Month 201X

Allen-Bradley, EnergyMatrix, FactoryTalk, LISTEN. THINK. SOLVE., PowerMonitor, Rockwell, Rockwell Automation, and Rockwell Software are trademarks of Rockwell Automation, Inc. Trademarks not belonging to Rockwell Automation are property of their respective companies.

PowerMonitor 5000 M8 OverviewWhen available, the PowerMonitor 5000 M8 includes all functionality of the M5 and M6 models, and also implements metering and power quality capabilities as defined in EN 61000-4-30, EN 61000-4-7, EN 61000-4-15, and EN 50160. These new capabilities provide a standardized method for measuring and reporting system harmonics as well as measuring both inter-harmonics and sub-harmonics in the power system. The 5000 M8 also measures and reports system voltage fluctuation (flicker). It can also detect and capture sub-cycle transient events.