Good Practices in Power Quality to build sustainable energy systems
INTRODUCTION TO POWER QUALITY
David Chapman, February 2012
- It is unlikely that a single solution will be effective or a site suffering from poor power quality
- Careful design of a solutions mix is needed
- This mix should be tailored to the problems and based on a detailed understanding of their causes
THE COST OF POOR POWER QUALITY
Roman Targosz, May 2012
- It is worthwhile investigating whether an industrial production site is suffering from poor power quality, especially in sensitive sectors
- No two companies, even when operating in the same sector, will be equally vulnerable to PQ disturbances; individual checks are therefore needed
Stefan Fassbinder, November 2014
- Dominant harmonics can be mitigated easily together with the mitigation of reactive power
- Even with filtering, harmonics should still be taken into account for the up-sizing of neutral wires and for the rating of cables and other equipment
- Keeping the system’s impedance low is of vital importance, with or without filtering
Marcel Didden, December 2011
- Standard extrusion machines have hardly any sag immunity
- Retrofitting existing textile extrusion lines is sometimes possible
- Retrofitting should always start with a proper data collection
- Whether immunization is best realized within the process, between the process and the grid, or
- within the grid, is case specific.
NUISANCE TRIPPING (TRUE RMS)
David Chapman, March 2014
- Many measurement instruments, even modern ones, use an averaging technique that does not measure harmonics correctly.
- Circuit breakers and cable sizes may be underrated as a result.
- True RMS meters, which take the complete distorted waveform into account, should be used instead.
NEW LOADS O N OLD SWITCHES, RELAYS AND CONTACTORS
Stefan Fassbinder, October 2014
- Electricians have to verify the right tables to know the maximum number of lamps that can be connected.
- In residential installations, they have to be alert for the overload of relays.
- In tertiary and industrial applications, they have to verify the characteristics of contactors.
- Fabricators may be confronted with challenges when a substantial part of lighting will go to LED.
VOLTAGE FLUCTUATIONS IN POWER NETWORKS
Zbigniew Hanzelka, November 2014
- Voltage fluctuations cause flickering lights (= “flicker”). The source of voltage fluctuations can be found among fluctuating loads of which the short circuit capacity at the network connection point is insufficient. The severity of this phenomenon depends both on the characteristics of those fluctuations and on the lighting type.
- Voltage fluctuations should be mitigated, since they have negative effects on rotating electrical machines, increase energy losses, and reduce the performance of electrolysis and electrical heating equipment.
HARMONICS:CAUSES AND EFFECTS
David Chapman, November 2011
- A range of design strategies and mitigation techniques are available to mitigate the effects of harmonics
- The four main mitigation solutions are passive shunt filters, passive series filters, isolation transformers, and active harmonic conditioners.
- Good design practice, the right electrical equipment, and good maintenance are the keys to preventing future problems.
Zbigniew Hanzelka, February 2012
- Do not search for coherent standards concerning interharmonics – they do not exist.
- Values and frequencies of interharmonics are mostly stochastic, depending on complex parameters of transient processes, and should therefore be assessed for each particular process separately.
EN50160 STANDARD ON PQ
Antoni Klajn, March 2013
- It is the task of the electricity regulator to set a minimum quality level that is achievable by the supplier without the need to raise prices
- If the customer has higher requirements, he should foresee in his own mitigation measures, or
- negotiate a separate agreement with the supplier.
ACTIVE HARMONIC CONDITIONERS
David Chapman, May 2015
- The use of filters against harmonics can improve the power factor and reduce the investment cost of the electrical installation.
- Active filters (AHC) have better performance and betterresistance against e.g. frequency variations and overload.
- The AHC is a flexible solution, making it easy to cope with changes of building layout and use.
CAPACITORS IN HARMONIC RICH ENVIRONMENTS
Stefan Fassbinder, September 2011
- Compensating the inductive load should be done properly to avoid over-compensation
- Variable compensation units should be designed using semiconductor switches and intelligent control algorithms to avoid interference with equipment
- Compensation capacitors should be detuned in order to avoid resonance with harmonics and overload by high frequency currents
- Technical and financial arguments can be in advantage of either centralized or dispersed compensation depending on the situation.
TRANSIENTS AND TEMPORARY OVER-VOLTAGES
UIE, July 2015
- The desired level of protection against transient over voltages and currents can vary greatly depending upon the application
- Equipment sensitivities should be selected in accordance with the desired protection level.
- Investing in surge protection may be chosen as a conservative approach, ensuring excellent
- performance while not significantly affecting overall system cost