Eliminate harmonics and save energy

The EN 50160 power quality standard for industrial electricity supplies

Structural changes in the production of energy and the growing use of power electronics and digital components is increasingly leading to network faults such as frequency and amplitude gains in harmonics — especially in higher frequency ranges. This results in increased energy consumption and premature wear due to rising temperatures. As a rule of thumb, an additional load of 10% caused by heat will reduce service life by 50%.

The cause of problems in network quality can be very diverse and complex: frequency converters, switching power supplies, reactive power compensation systems, an undersized neutral conductor or current peaks. In fact, the majority of industrial firms have been using compensation systems that limit harmonics for many years. Nevertheless, this measure is often not effective enough because conventional compensation systems reduce the reactive power only by adjusting the displacement factor, cos φ; this measure does not eliminate the harmonics.An initial sign of an overload caused by harmonics or unbalance can be represented by defective capacitors, for example.

Left: Strongly distorted current profile

Right: Separation of the signal into the harmonics sections (fundamental oscillation and third, fifth, seventh harmonic)

Analysis of the actual state

In Europe, network quality is predominantly standardised via the EN 50160 standard. This standard ensures that, at the very least, the following parameters are measured using a network analyser:

Voltage curve (10 minutes)
Unbalance
Frequency (10 seconds)
Long-term flicker (2 hours)
Harmonics, up to the 25th harmonic
THD (total harmonic distortion)

These parameters are recorded over a period of at least one week. Long-term recording is necessary for factoring in low loading periods during shift operation or at the weekend. Changes in operating cycles lead to constantly changing harmonic currents. Special power quality data loggers (see below) automatically record the parameters and also simplify the subsequent analysis process.

Photo:
Long-term recording of all phases using the Power Quality Analyzer

Video:
"How to Use a Harmonics Test in a 435 Power Quality Analyzer" (Fluke)

Typical issues

Almost half of all electrical equipment in energy-intensive operations or in intensively used office buildings suffer from two or more network quality issues:

Computer crashes
Flicker
Failure of equipment at partial loads

Overloaded capacitors
Problems when switching large loads
Overheating of neutral conductors

Actions

If the test on the system using the network analyser reveals that there are faults in the network, you must take the appropriate action. First check whether the problems originate from beyond the electricity meter, i.e. the issue is the responsibility of the network operator, or if it originates from behind the supply point. The second step is to localise the sources of the fault. In most cases, additional small-scale measurements are required to localise the source of the fault, if necessary by shutting down or isolating the circuit.If the current status of the system is known, there are several fault elimination options to consider:

Realignment of the existing compensation
system to the harmonics
Use of EMC filters at the cause
Use of active compensation systems

Use of an active power factor
Use of modern UPS systems
Replacement of old frequency converters

Recommendations

Fluke 430 series — Power Quality Analyzer

Comprehensive power quality analysis tool for three-phase networks.

Tektronix PA3000 Power Analyzer

The PA3000 series is also perfectly suited for product development.

Fluke 1730 series — Energy Logger

Three-phase logger for analysing currents, voltages and power.