How to calculate Harmonic Filter, Power quality analyzer and active power fitler
Jul 08,2020

How to calculate Harmonic Filter

In power supply systems based on alternating current (AC) -- such as the main power distribution network from electric utilities -- non-linear loads can feed some amount of power back into the wiring. This feedback typically occurs in the form of harmonics: multiples of the frequency of the original AC wave. Harmonics need to be eliminated from a power circuit by a harmonic filter to prevent them from causing voltage distortions and excessive currents in grounding connections. A harmonic filter consists of a power capacitor connected in series with a tuned reactor, with both of them placed between the power line and ground. The parameters for a harmonic filter depend on the electrical circuit in which harmonic elimination needs to happen.

Voltage waveform
voltage harmonics THDU
voltage waveform voltage harmoncis waveform THDv

Step 1

Measure, using the harmonic analyzer on the circuit at 30% load, the load LD in kilowatts and the power factor PF.

Step 2

Calculate the phase angles for both the actual and desired power factors (a typically desirable power factor is 0.97) by evaluating: PAActual = arccos(PF) PADesired = arccos(0.97)

Step 3

Calculate KVAR, the kilo-volt-amperes required to raise the power factor from PF to, for example, 0.97 by evaluating: KVAR = LD x (tan(PAActual) - tan(PADesired))

Step 4

Calculate the capacitance required for the capacitor in the harmonic filter by evaluating: C = KVAR / ((KV)^2 x 2 x Pi x F x 0.001) Replace KV by the power line's voltage in kilovolts, and F by the power line's frequency in Hertz.

Calculate the reactance required for the tuning reactor in the harmonic filter by evaluating: X = 1 / (2 x Pi x F x C)

current waveform in networks
THDi current harmonics
Current waveform current harmoncis waveform THDi

Power Qaulity Analyzer

The Fluke 434-II Energy Analyzer and 435-II Power Quality and Energy Analyzer are designed to help you minimize downtime, quickly trouble shoot power quality issues and easily discover the costs of wasted energy. Downtime is expensive and getting the data you need to solve to critical power quality problems quickly is key. The 434-II and 435-II Analyzer’s measurement process and data output have been optimized to help you access the most critical information easily.

active power filter applied in 50hz networks
50Hz power grid

Multiple parameters are measured simultaneously and displayed in formats that quickly describe overall power quality health. The detailed information helps you make better maintenance decisions—whether you’re trying to reduce energy waste, find the source of power quality issues or see how motor startups are affecting your electrical system. Data can be accessed as simple digital values, trend graphs (for fast insight into changes over time), waveforms, or phasor diagrams. The data can also be analyzed and organized into tabular formats. Detailed event data allows you to see the magnitude, duration and time stamping of anomalies enabling you to rapidly correlate the problems you are experiencing in your facility.

active power filter for 60Hz power grid system
60hz power grid
Active Power Filter

Active Power Filter APF is connected in parallel with non-linear loads, and uses one set of CT to detect the load current. It calculates each order harmonic current by FFT algorithms in its DSP microchips, and then generates a compensating current with the same amplitude but opposite phase angles to the detected harmonic current, which cancels out the original load harmonics. APF not only eliminates harmonic current from the load side, but it also mitigates harmonic voltage caused by harmonic currents. The APF system can also improve power factor (PF) and correct load imbalances in the power system.

active power fitler modular
interface of active power fitler

ZDDQ Active Power Filter

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active power filter applied in chemical factory

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