Power Quality Analyser / Power Analyzer

When looking for a power quality analyzer or power measuring device, the question about application comes first. Here it is important to distinguish whether a temporary measurement or a continuous long-term measurement should be carried out with a power quality analyser. Furthermore, it must be found out whether it goes about 1-phase or 3-phase measurement. In the 3-phase power measurement, it is also necessary to differentiate between symmetrical and asymmetrical power measurement.

1-phase power measurement
In principle, power quality analysers which are used for 1-phase measurement can also be used for 3-phase applications if the load is symmetrical. This is because the current taken off at all three phases is always the same. The power quality analyzer then calculates the total power itself. In the power quality analysers for single-phase measurement for permanent installation, a multiplier for the displayed measured value can be deposited and the display will always show the correct measured value.

The power quality analysers for this application are often kept very simple and are used only for temporary measurement. They have no memory and a measuring range is relatively limited.

3-phase power quality analyser
Multiple phase power quality analyzers have at least 3 current clamps or Rogowski coils to measure the current through the connecting cables of the phases. These power quality analysers are often used for permanent monitoring of network parameters. For energy audits or for determination of energy needs of the industrial companies, power quality analysers are indispensable. As well as the power quality analysers for single-phase applications, these power quality analysers also have voltage measurement cables that are connected directly to the terminal points. The power quality analyser measures then, in combination with the current clamps, the parameters: current, voltage, mains frequency and phase angle. From these parameters, the three-phase power quality analyzers then calculate all power parameters such as active, apparent and reactive power.

Power quality analysers of this type are usually equipped with a memory function / data logger. The datalogger enables continuous storage of the network data, thus helping to determine the energy needs or consumption of machines and systems. The memory is then often read out via a corresponding reading software. Besides, there are also power quality analysers available that store the measurement data on a SD memory card. This simplifies the analysis of the measurement data to such an extent that no other software is needed for tabular measurement data evaluation. Another extension level of the power quality analyser is the network analyzer.

Network analyzers / power quality analyzers with network analysis function
Power quality analysers with network analysis function are based on the principle similar to the "normal" power quality analysers. However, the network analyzers possess, as another option, the function of determining the network distortion / harmonics. Simpler network analyzers can determine the harmonics up to the 25th order. High-quality power quality analysers with network analysis function can easily do this up to the 50th order. In addition, these power quality analysers can determine start-up currents, flicker, DC components, etc. These power quality analysers also have a memory that can be evaluated by the user.

power quality analyzer Clamp or Rogowski coil?
At the beginning of this purchase advice, we briefly mentioned that there are power quality analysers with current clamps and / or Rogowski coils. What is the difference between them?

The difference lies essentially in the design. A current clamp is rigid and can be successfully used anywhere where there is a possibility to easily access and measure the current-carrying power of a machine or system. Current clamps are often used for measurements when the currents that should be measured by the gauge are relatively low. Current clamps can usually be used at maximum 1200 A per phase. Due to the rigid design, current clamps are rather difficult to use in sub-distribution and control cabinets. For this purpose, power quality analysers with flexible Rogowski coils are applied. This power quality analyzer is excellently suitable for power measurements where the space for current clamps is insufficient. Furthermore, the coils can be used for significantly higher currents per phase. So, Rogowski coils can accurately determine up to 10,000 A.

Should you have further questions about our power quality analysers, our technicians are always ready to provide help and advice under our phone number: +44 (0) 2380 987 035 for PCE Instruments UK or +1 (561) 320-9162 for PCE Americas Inc.

If you have a special application need, it will be our pleasure to consult you and find the right power quality analyser for you.

In the power measurements of voltage networks, power is the result of the formula P = U * I; which means the product of the voltage U and electric current I. In the case of measuring alternating current (i.e. line voltage of 50 Hz) a phase angle between current and voltage is generated. You should take it into account in measuring effective power. Therefore, the power quality analyzer shows the combined measurement of electrical power, a tour of the voltage and current. The value P (effective power) is equivalent, as described above, to the product of both values.

In practice there are three different power classes:

- Apparent power S measured in W (watt- amps)
- Effective power P (and equivalent power) measured as W (watts)
- Idle power Q as VAR (watt, amps and reagents)

In general we have to differ between two measuring methods.

direct current measurement: For this current measurement, the circuit must be opened. It is not possible to measure in an active circuit.
indirect current measurement: The current is measured by a current transformer clamp. This can be easily clicked around the wire. It is not necessary to open the circuit.

All PCE power quality analysers provide the indirect measurement system.

Power Analysers are available as several types and versions. Depending on the field of operation, several Power analysers are advisable. For maintenance and inspections power analysers with clamps are available. These power analysers will measure current indirectly so you don't have to take action in the current circuit. Electric power is able to be measured and described with power analysers, too.

Three phase power quality analysers are able to measure simultaneously via power analysers with three clamps. The possibility to measure power is also given with several special constructed power analysers. These power analysers are not only able to measure power but also values like current, voltage and resistance. Power analysers are available for mobile needs and stationary operation for example in form of laboratory power analysers.

Applications for power quality analyzers:

In General the Power analysers are used to measure the power and to calculate the energy cost depending on the measurement. Other Customers measure the output from a transformer and the decide if they can add on more devices on the transformer or not. In the past couple years the Power analyser are also used in the photovoltaic area.

DIN EN ISO 50001 / DIN EN 16247-1
ISO 50001 is an international standard for energy management. Every year, new prognosis is made for energy consumption in the future. Of course, the energy consumption is likely to increase. Saving energy is actually very simple.

For example, if one thinks about what energy consumption in a private environment is absolutely unnecessary, potential savings can be quickly clearly defined.

If we think on a larger scale, for example in the area of industry, commerce or organisations, we quickly detect much larger energy-saving potentials.

Of course, for example, the companies can be certified according to the ISO 50001 standard, or they can just consider this standard as an impulse to think about how to achieve an improvement economically. It is clear that who saves the energy can immediately achieve positive results in financial terms.

And whenever money is involved, everyone becomes more attentive, or rather, money is the real driving force for the innovations or, as in this case, the impetus to check electrical consumers in operation by means of a power analyzer. Of course, anyone can easily add up the electrical consumption based on nameplates, but that is usually not enough. If you want to save energy on machines and systems in your business or if you want to reduce the costs for air conditioning and cooling in your hotel, you have to use the power analyzer. If you have qualified personnel who can measure, evaluate and analyse the data themselves – it is good. But you can also hire an energy consultant to work on your problem as a service provider.

The power analyzer, regardless of whether it measures single or three phases, can be described as a small energy management system when equipped with the appropriate evaluation software.

Following DIN ISO 16247-1, a company can have an initial energy audit carried out as a first step towards reducing the energy consumption. It can be carried out e.g. by the TÜV or by the energy consultant certified by the TÜV. This expert always uses the power analyzer to record the data. The energy audit is basically a part of the ISO 50001 standard. With this first part, the basis is created for the energetic consideration of the consumers.

PCE Instruments provides the appropriate power analyzer for every application. You also can start identifying large savings potentials today and use such a power analyzer or hire an external energy consultant to prepare the first stage of ISO 50001, the energy audit.

For quality and safety-related measurements, the current clamp used must be calibrated regularly. Calibration is a technical term for checking the accuracy of a measuring device or measuring equipment through comparative measurements. The minimum requirements for the procedures for calibrating the current measuring clamps for direct current and low-frequency alternating current are described in the guideline VDI/ VDE/ DKD/ DGQ 2622 - Sheet 23.1.

Equipment for calibrating the current clamp
Multifunction calibrators are often used to calibrate the measuring devices for electrical quantities. These calibrators produce adjustable stable output values that can be directly compared to the displayed current clamp readings. The calibrator used must be checked regularly with the help of more precise calibration standards, i.e. it must also be calibrated itself. This ensures that the accuracy of the generated quantities meets the requirements.

To calibrate the power analyzer, the calibrator does not have to be designed to deliver the highest desired current value. The current output can easily be multiplied by several windings of the connected current-carrying conductor or by special measuring coils. The same amount of current flows through each of the windings. If 50 windings are simultaneously enclosed with the current clamp, the measured current intensity increases 50-fold. This means that instead of measuring for the delivered 10 amps, the measurement accuracy can be measured at 500 amps. This applies to both alternating current and direct current.

Defining the tolerances
For each power quality analyzer, the technical specifications indicate the tolerance for the accuracy of the measurements. However, the user of the current clamp requires proof that the measuring device meets the accuracy required for the respective application. The permissible tolerance for the measurement task can be smaller or larger than the tolerance that is confirmed by the manufacturer for the device type used.

Therefore, in order to evaluate the calibration results, it must be precisely defined which deviations are permissible for the individual measuring ranges of the power analyzer to be tested. If the calibration laboratory does not receive any other specifications, it uses the accuracy information from the device specifications. If the expected accuracy is not achieved during the calibration, the current clamp may no longer be used, or only to a limited extent, for further measurements.

Defining the reference points
The number and position of the selected reference points are important for the meaningfulness of the calibration results. The current clamp that has only been calibrated for direct current must not be used as the calibrated current clamp for the alternating current measurements. A device that is used for measuring direct currents, alternating currents and inrush currents should also be calibrated for these three measuring ranges. At least three measurement points should be checked for each of the separate current measurement functions. The measuring points should cover the complete range of values for which the current clamp is used. The more measuring points are checked, the more detailed the detected deviations can be evaluated.

Power Analyzers can be divided according to the working principle into:

• Analog Quality Analyzer
• Digital power Quality Analyzer with direct current measurement
• Digital power Quality Analyzer with indirect current measurement

Measuring with the analogue power analyzer
The analogue power Quality Analzer measures current and voltage simultaneously and directly. The measured value is shown on an analogue display.

Digital power analyzers with direct current measurement
The measurement is made directly as with the analogue power analyzer.

The only difference here is in the display of the measured values. The readings are shown on a digital display. Often these power meters already have a data memory integrated. This allows the user to document even small occurring power. These power quality analyzers are often designed as a desktop device or in the form of a multimeter, since the field of application is often in the laboratory or in the workshop.

Digital power analyzers with indirect current measurement
In the indirect measurement of power with the power analyzer, the current is determined via current transformers. The current clamp functions as a coil. When the current-carrying conductor induces a current into the current clamp, the current in the conductor can be determined from its strength.

Current clamps or Rogowski coils are used to measure the induced current and determine the actual current from it. By offsetting the indirectly measured current and the directly measured voltage, the power meter determines the power with the formula P = U * I.

The method of indirect current measurement in the power analyzers is always used when high currents occur or it is not possible to cut the conductor. The measurement with current clamps has further advantages: it is possible to measure several phases at the same time and the power can be determined by the power analyzer.

Here it often does not matter whether the phase is symmetrically or asymmetrically loaded.