AC Power line disturbances consist of these types in order of importance as an approximate %:
- RMS sags (dips) and swells (80%)
- Harmonics (harmonic distortion) (10%)
- Transients (impulses) (10%)
- High-Frequency Noise (<1%)
The PowerSight High Frequency Analysis Option (FAO) works with the PS4500 and PS4000 power quality analyzers and the HA1000 current probes. It is a combination of hardware, firmware, and software that allows you to analyze the presence of high-frequency power line noise content from 3,000 Hz to 100,000 Hz, and < 1 volt peak. The FAO option extends the capability of the PS4000 or PS4500 PowerSight power quality analyzer meter into a hand-held spectrum analyzer. This option is useful in determining whether power-line noise is present that may cause disruption of those equipment that are especially sensitive to such high-frequency noise.
The FAO is designed to measure continuous high-frequency noise. This is distinct from transient events that can be captured by the PS4500 Power Quality Analyzer impulse measurement system. The PS4500 captures transients as fast as 8us and up to 1000 volts peak. Example: Impulsive Transient
The PS4500/PS4000 measures harmonic content to the 63rd harmonic, or 3.8kHz. Harmonic Spectrum Example High-frequency noise however describes frequencies above this range of power harmonics - in the tens of kHz and higher. High-frequency noise is generated by certain types of loads (sources) that is subsequently conducted along power conductors and circuits. It is usually of very low voltage levels (note that high frequencies become attenuated rapidly over long distances) but the potential exists in rare situations for HF noise to affect sensitive devices. Most electronic devices have EMI/RF filtering at the front end of their power supplies that prevents ingress of conducted HF noise. However in rare situations where such filtering is not present, or if the noise couples into electronics via another route, then those equipment that are susceptible could be adversely affected causing disruption and mis-operation.
Continuous high-frequency noise generation usually comes from electronic sources such as lighting systems, adjustable speed drives, and UPS systems. Other devices that perform rectification of AC into DC also have the potential to generate high-frequency noise continuously. Non-electronic sources are poor wiring, or poor connections, bad contact problems. For example, intermittent connections, or loose fuse or breaker connections at panels can generate continuous high-frequency noise from arcing- or corona-type emission as infrastructure ages and devices and wiring degrade. Switch contacts that have deteriorated with age often have imperfect mating of contact surfaces (due to pitting) that will arc and spark as contacts come together during switching cycles. The contacts bounce and chatter generating impulsive noise but this is a transient phenomena that occurs only during a brief switching event. (Impulsive phenomena are best measured with the PS4500/PS4000 transient measuring system.) Transient events are distinct from a continuous source of high frequency noise such as on-going arcing or corona discharge phenomena.
We have supplied the FAO option in Applications where high-frequency noise can affect sensitive electronics, or affect precise measurements, or interfere with specialized manufacturing processes, or communication signals. This includes sensitive bio-medical measurement equipment, military communication Applications, and industrial control in manufacturing plants that have high populations of adjustable speed drives. (High levels of high-frequency noise can occur inside a manufacturing plant as a result of the aggregation of the noise from many individual drives. Our partner Environmental Potentials has more information on this type of application here: Variable Frequency Drives Application Note:)
Utility power supply is generally is not a major source of high-frequency noise.
It would be a rare situation if a power utility was a source of high-frequency noise. Plus, the source of noise would have to be close by and be continuous. The long line lengths of power distribution cables would rapidly attenuate any high frequencies. Any HF noise occurring on utility distribution systems (such as corona-type discharge or similar arcing) that would then find its way into low voltage circuits with any appreciable amplitude via conduction is very unlikely. HF noise generation, should it occur, is internal to a facility or operation.
For specialized Applications where continuous high-frequency noise needs to be evaluated, use the FAO option - along with a PS4500 Power Quality Analyzer and specifically with the HA1000 Current Probes: only.
With the FAO option the high-frequency content of both voltage and current can be evaluated simultaneously. To analyze the high-frequency content of power circuits you will need to plug voltage leads into the FAO voltage conditioning accessory and connect the FAO to a PS4500/PS4000. To analyze the high-frequency content of current, connect an HA1000 current probe into a special adapter cable that then plugs into your PowerSight PS4500/PS4000 meter.