What is Power Quality in a data center?

Power Quality describes the quality and stability of the electrical voltage and current used to power IT equipment.

A stable electrical infrastructure is not just about sufficient power. Deviations in voltage, current, frequency, and waveform can also be relevant to the operation of connected equipment.

Important Power Quality parameters include:

• Total Harmonic Distortion (THD)
• harmonic distortion
• Crest Factor
• Power Factor
• voltage and voltage spikes
• current and power surges
• voltage dips
• frequency
• phase load
• residual current

Continuously monitoring these values provides a much more complete picture of what is happening electrically in a rack than kWh measurement alone.

Why is Power Quality becoming more important due to AI and high-density racks?

AI and HPC infrastructures change the electrical load of data centers.

GPU systems can demand very high power, and their load can vary significantly depending on the workload. Recent technical literature describes modern AI training racks with significantly higher and more dynamic power profiles than traditional server racks; such rapidly changing loads can cause harmonic distortion and voltage flicker, among other things.

Therefore, other PDU manufacturers are also explicitly focusing their latest intelligent rack PDUs on Power Quality Monitoring for AI data centers, including THD and voltage/current disturbances.

For data center operators, this means only looking at:

“This rack uses 40 kW”

provides less and less information.

You also want to be able to investigate:

Is the voltage stable?
Are there power surges?
Does harmonic distortion occur?
How does the Power Factor behave?
Are deviations incidental or structural?
When exactly did an electric event take place?

That is where Power Quality Monitoring comes into play.

What is Total Harmonic Distortion (THD)?

Total Harmonic Distortion, usually abbreviated as THD, is a measure of the harmonic distortion of an electrical voltage or current waveform.

In an ideal situation, alternating voltage and alternating current have a pure sinusoidal shape. Non-linear electrical loads can distort this waveform.

Servers, for example, contain switching power supplies. As a result, harmonics can arise in the electrical load. THD makes visible how much distortion is present relative to the fundamental frequency.

For a data center, therefore, both voltage THD as current THD provide relevant information.

Power Quality specialists and PDU manufacturers use THD monitoring, among other things, to visualize anomalies close to the IT load.

Why monitor harmonics in a data center?

Harmonics are frequency components that distort the normal sinusoidal shape of voltage or current.

That is relevant because a modern data center contains many non-linear electrical loads.

When harmonic distortion increases, this may, for example, be a reason to further investigate what is happening in a rack or electrical distribution chain.

In this regard, the location of the measurement is particularly interesting.

A measurement at the beginning of the electrical infrastructure tells what is happening there. An intelligent rack PDU can measure. close to the IT equipment that actually uses the electricity.

That makes rack-level Power Quality Monitoring interesting for locating and analyzing anomalies.

What is Crest Factor?

Crest Factor describes the ratio between the peak value and the RMS value of an electric waveform.

With this, Crest Factor provides information about the magnitude of peaks in a current or voltage signal relative to the effective value.

A deviating Crest Factor can provide additional information about the shape of the electrical load and possible deformation.

In combination with THD, current, voltage, and Power Factor, this provides a more complete picture than when only average energy consumption is considered.

What are voltage dips and voltage spikes?

A voltage dip is a temporary drop in voltage.

A voltage spike is actually a temporary increase in the measured voltage.

Because such events can be brief, they are not always visible when only looking at current or average values.

Therefore, event registration is important.

When a Power Quality system has a deviation including timestamp if registered, an operator can investigate afterwards when the event occurred and compare this with other events in the data center.

Why monitor power peaks?

Electricity can also exhibit short-term peaks.

Especially with dynamic IT loads, it is interesting not only to know the average current but also to record peak values.

After all, a high average load and a short power peak tell different stories.

By means of current peaks Analyzing this together with other measured values provides greater insight into the actual electrical behavior of a rack.

What is Power Factor?

Power Factor represents the ratio between the actual active power used and the total apparent power.

A Power Factor close to 1 means that a large portion of the input power is effectively used as active power.

Power Factor can therefore provide useful additional information about the electrical load of IT equipment.

In combination with active power (W), apparent power (VA), reactive power (VAR), THD, and Crest Factor, a more comprehensive picture of the load emerges.

Why monitor the frequency?

In European data centers, the electrical infrastructure normally operates around 50 Hz.

Frequency monitoring makes changes in this electrical fundamental frequency visible.

Although frequency is usually very stable, this parameter is part of a complete Power Quality picture and can be used together with other measurements for the analysis of electrical events.

What is Residual Current Monitoring?

Residual Current Monitoring (RCM) measures residual or leakage currents in the electrical installation.

A residual flow arises when the outgoing and return flows are not fully in balance.

Continuous monitoring can help operators detect changes and deviations and subsequently investigate them in a targeted manner.

Schleifenbauer PDU 5.0 can optionally be equipped with IEC/EN 62020 RCM Type B measurement, including total, peak, AC and DC residual current measurements.

This can be particularly interesting in critical data center environments where operators want more insight into the electrical condition per rack or phase.

Why measure Power Quality at the rack level?

A data center has measuring equipment at various points in the electrical infrastructure.

But ultimately, the IT load is located in the server rack.

The The rack PDU forms one of the final links between the electrical infrastructure and the connected IT equipment.. Therefore, Power Quality Monitoring at the PDU level can provide information about what is actually happening close to the IT load. Other specialized PDU vendors also position rack-level monitoring as valuable for analysis and troubleshooting for precisely that reason.

This makes it possible, for example, to compare a deviation in one rack with other racks or measurements at other levels in the infrastructure.

Which Power Quality values can an intelligent PDU measure?

Not every intelligent PDU measures the same parameters.

Schleifenbauer PDU 5.0 can measure inputs and branches, among other things:

• Voltage
• Voltage dip / peak
• Current
• Current peak
• Active Power (W)
• Apparent Power (VA)
• Reactive Power (VAR)
• Energy
• Total Harmonic Distortion (THD)
• Crest Factor
• Frequency
• Power Factor
• optional Residual Current

Depending on the PDU version, different values may also be available at the outlet level.

As a result, an intelligent rack PDU can be much more than just a power distributor or kWh meter: it also becomes a measuring point for the electrical condition close to the IT load.

Power Quality Monitoring with Schleifenbauer PDU 5.0 and EnerTree

At Schleifenbauer, the desired PDU functionality is independent of the chosen management architecture.

After the choice for a Metered, Monitored, Switched or Managed PDU it is possible to choose how the intelligence and Power Quality data are managed.

Two main architectures are available for this.

Controller Module with EnerTree Lite

A PDU with Controller Module contains the intelligence locally in the PDU.

EnerTree Lite is embedded software that runs directly on the Controller Module.

Measured values can be viewed and managed locally via the web interface. EnerTree Lite supports, among other things, Power Quality measurements such as THD, Crest Factor and voltage and current peaks with time stamping. Historical data, trending, alerts, and integration via SNMP, Modbus, and REST, among others, are also available.

This architecture aligns with the conventional way in which intelligent PDUs are managed and is suitable for smaller or locally managed installations.

Gateway Module with EnerTree Platform

For larger environments, the same intelligent PDU can be equipped with a Gateway Module.

The intelligence is then not hosted locally in every PDU, but managed centrally with EnerTree Platform.

EnerTree Platform runs as software in a separate virtual machine (VM) and is designed for central monitoring and management of up to 10,000 PDUs.

As a result, Power Quality data from large numbers of racks can be centrally collected, analyzed, and compared.

In addition, the EnerTree Platform offers, among other things:

• real-time monitoring
• extensive historical data
• trends and Power Quality analysis
• dashboards
• reporting & analytics
• scheduled reports
• thresholds and alerts
• database and data export
• mass management
• Zero Touch Provisioning
• integration with DCIM, BMS, and ERP systems

This makes Power Quality Monitoring part of a broader Data Center Energy Management (DCEM)-environment.

From one rack to thousands of PDUs

The difference, therefore, lies not only in what the PDU can measure.

The choice lies mainly in how you want to manage that information.

A Controller Module with EnerTree Lite provides a conventional, local intelligent PDU architecture.

A Gateway Module with the EnerTree Platform makes the same PDU functionality part of a central and scalable energy and Power Quality management platform.

Moreover, with the modular PDU 5.0 architecture, this choice can be changed later by replacing the communication module, without having to replace the entire PDU.

Power Quality Monitoring without separate software licenses

EnerTree Lite and EnerTree Platform are part of the Schleifenbauer PDU 5.0 architecture and require no recurring software license fees.

This allows data center operators to use Power Quality data, energy measurements, alerts, historical data, and, with the EnerTree Platform, advanced central DCEM functionality, without software costs increasing with every additional PDU.

For large PDU installations, that can make a significant difference in the total costs of monitoring and management.

Power Quality becomes part of rack energy management

The increasing power density of AI, GPU, and HPC infrastructure makes it increasingly relevant to look beyond just kWh and rack load.

THD, harmonics, crest factor, power factor, voltage dips, voltage and current peaks, frequency, and residual current each provide a different piece of information about what is happening electrically in and around a rack.

By measuring these values close to the IT load and analyzing them centrally, data center operators gain more information to investigate anomalies, identify trends, and better understand the electrical infrastructure.

Of Schleifenbauer PDU 5.0, EnerTree Lite and EnerTree Platform Power Quality Monitoring can be integrated into the same infrastructure used for rack power distribution, energy metering, and PDU management.

Want to know more about Power Quality Monitoring?

Look at EnerTree DCEM for PDU monitoring and energy management or contact Schleifenbauer to discuss which PDU and management architecture suits your data center.

The post Power Quality in Data Centers: Monitoring THD, Harmonics, and Power Quality appeared first on Schleifenbauer – PDUs.

Source: https://www.schleifenbauer.eu/nl/power-quality-datacenter/