Introduction

If the power supply of equipment includes a semiconductor control device, high frequency noise (higher than several kHz) may be generated by distorted voltage and current waveforms.  The RMS value of such a noise is called “high-order harmonics”.  It may contain various frequency components, and becomes a noise higher than multiples of 10V once it is affected by resonance of cables, etc. This voltage noise causes equipment to malfunction or become damaged, and may also be received by TVs and radios in the same building or neighborhood.

Setup

Monitoring location: 1-phase 2-wire, 100V circuit

Problem

• Equipment malfunction or damage
• Receiving problems with TV and radio signals in the neighborhood

Analysis

High-order harmonics are often higher in frequency than the 50th order harmonic, so it cannot be detected by conventional harmonic analysis. By using the high-order harmonic function of Model PW3198, the sum of high frequency noise can be easily detected. The critical frequency varies, but such noise may exceed 10V in resonance due to the resistance, capacitance or inductance component of the cables.

Usually, the noise generated by equipment, and particularly its power supply, is regulated by the IEC61000-3-3 (Flicker), IEC61000-3-2 (Harmonics), IEC61000-3-12 (Total harmonic distortion), etc. However, the measurement object is up to the 40th order (2kHz on 50Hz, 2.4kHz on 60Hz) only. Also, the frequency regulated by the power supply terminal disturbance voltage (CISPR 22/EN55022, etc.) is 150kHz or higher. As such, there is no standard or regulation for noise in the several 10kHz range.

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