Setup

Monitoring location: 3-phase 3-wire (3P3W2M), 6.6kV circuit

Analysis

This is an example of judging harmonics inflow and outflow based on harmonics measurements. Using a 3-phase 2-wire set up, the overall inflow and outflow of a 3-phase installation are judged by the harmonic voltage-current phase difference (θsum). When it is between –90̊ to 0̊ to +90̊, it is inflow. Conversely, outflow is determined when the sum is between -180̊ to -90̊ or +90̊ to +180̊.

The fundamental wave (brown) is consumption (inflow) as shown below. Most of the 5th harmonic (green) is also inflow.

The 3rd harmonic (red) is outflow as shown in the graph below. The 7th harmonic (blue) is outflow. The data shows with the vertical lines that the phase difference exceeds 180̊ and returns to -180̊ (or vice versa).

We recommend judging the inflow or outflow by using the “θavg” graph in the harmonic time plot graph on the application software Model 9624-50 PQA HiVIEW Pro.

<Judgment Example 1>

<Judgment Example 2>

<Reference> Guideline for the Harmonics of a Distribution Network (Japan)

Official Report from the Ministry of Economics and Industries in Japan “Guideline for Harmonics Deterrence Countermeasures on Demand-Side that receives High Voltage or Extra High-Voltage” (September 30, 1994)

1) Harmonic Voltage (Total Harmonic Voltage Distortion) : 5% at 6.6kV system, 3% at extra high-voltage system

2) Harmonic Current : Upper limit values of harmonic outflow current (mA) per 1kW of Contracted Power

<Reference> Harmonic inflow/outflow judgment on a measuring instrument

1. Judgment based on harmonic power : Judge the inflow or outflow according to the polarity of the harmonic (effective) power. (Judge each phase and each order independently.)

Problem with this method : The higher the order, the smaller the harmonics power level. The smaller level makes it difficult to judge the polarity accurately, thus making it difficult to judge inflow and outflow.

2. Judgment based on the harmonic voltage-current phase difference : Judge the inflow or outflow according to the harmonic voltage-current phase difference (difference between harmonic voltage phase angle and harmonic current phase angle). For 3-phase 3-wire (3P3W2M or 3P3W3M) installations, we recommend using the harmonic voltage-current phase difference of the “sum” value.

Recommendations: Judge to see if the harmonic current amplitude is high or exceeds the limit. Then, judge the inflow or outflow by watching the harmonic voltage-current phase difference.

Source : Guidebook for Power Quality Measurement, HIOKI E.E. Corporation