Cutting power bills and improving power quality
Thursday, 22 March, 2018
A majority of energy utility organisations across Australia and New Zealand are now using demand charges calculated in kVA (kilovolt ampere) as opposed to kW (kilowatt) based demand charges which were previously applied.
Demand charges based on kVA (or apparent power) are a more accurate measure of the impact a user’s peak demand has on the respective network, relative to a tariff based on kW (or real power). This pricing change provides an opportunity for the user to take steps in improving the efficiency of electricity used on site and therefore reduce their bill. This can be done by improving the overall power quality.
Apparent Power reflects the true amount of current flowing through the electrical infrastructure and determines the capacity of the lines, cables and transformers required to supply electricity to different end users. Apparent power is a vector representation of real power (kW) and apparent power (kVAR), as shown in figure 1: As you improve your power factor, the angle (Ɵ) within the triangle reduces. This means that the kVA (or apparent power) reduces resulting in lower demand charges, hence why it is now important to improve your power factor on site.
The second major contributor to poor Power Quality is Harmonics. The adoption of non-linear load devices such as variable speed drives, LEDs, PV solar inverters and uninterruptable power supplies has introduced harmonic current ‘pollution’ in the form of damaging harmonic orders.
Some examples of linear systems include motors and heaters. Non-linear loads such electronic devices used to power systems are common in modern industry. These loads affect the true power factor of a site.
For example a Total Harmonic Distortion (THDi) current of approximately 60% effectively reduces the true power factor by around 10–15%. Any system that reduces harmonic currents will improve the true power factor of a site.
Harmonic currents also have a negative impact on the true power factor at sites containing a high percentage of non-linear loads. Passive Harmonic filters will reduce harmonic currents, however only those which have been set manually. Active power filters dynamically mitigate harmonic orders from the 2nd (100 Hz) to the 50th (2500 Hz) simultaneously. This allows sites to achieve very low harmonic THDi% levels and to meet IEEE 519 regulations.
Capacitor banks are one way to target displacement power factor issues, however they do not remove harmful harmonic currents.
Some of the solutions available
Delta has a range of solutions, including:
PQC Modular APF – This solution is suitable for situations in which harmonic currents are present, along with a poor power factor. The PQC APF also has the ability to correct load balancing issues to ensure the highest power quality is present on site.
PQC Modular SVG – This solution is an alternative to the traditional capacitor banks. Its focus is to correct displacement power factor only. The benefit it has over capacitor banks is it has the ability to balance the loads. This ensures a high standard of power quality for sites which have minimal harmonic current concerns. The modular nature also ensures flexibility.
APF2000 – This solution is suitable for many scenarios in the industrial sector, whether it be for harmonic currents and/or a poor power factor and load balancing. This solution starts at 50 Amps all the way up to 300 Amps. Up to 6 units can be placed in parallel, which can provide up to a total of 1800 Amps.
SVG2000 – This solution is suitable for large heavy industrial sites with the primary issues being a poor power factor. This solution is sized in kVAR’s and has two variants, the 300kVAR and the 500kVAR unit. Up to 6 units can be placed in parallel using the same CT’s which allows up to 3000kVAR. The SVG2000 also corrects harmonics from the 2nd order to the 13th order and provides load balancing.
Confused? Help is available
Delta has aligned with skilled contractors and partners across Australia and New Zealand. These relationships allow the end user to gain expertise from very beginning discussion; all the way to post installation and commissioning of the power quality solution.
The detailed stages followed:
- Obtain the sites power quality data via a site audit performed by industry leading and recognised partners.
- Provide a professional analysis of the data by a team of qualified engineers.
- Propose a complete power quality solution to the user including various payment plan options.
- Provide a complete professional installation and commissioning package for the client, ensuring a smooth process.
- Provide a professional post installation site audit to ensure all targets have been met for the user.
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