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		DEFINITIONS Click on headings below to go to subject Flicker Frequency Conversion Over Voltage or Swells Phase Shift Power Conditioning Power Outages Power Factor Control Regenerative Loads VAR Support Voltage Harmonics Voltage Sags or Dips Voltage Unbalance Voltage Sags or Dips A sag or dip, as defined by IEEE Standard 1159-1995, is a decrease in RMS voltage at the power frequency for durations from 0.5 cycles to 1 minute, reported as the remaining voltage. To clarify: a voltage reduction of 20% from nominal, results in a Sag Voltage to 80%. Typical causes: Faults on utility system Tree branches may strike power lines, particularly in stormy weather Animals/ large birds across insulators, power lines or equipment terminals Vehicle damage to utility poles Bad weather when insulation systems are compromised Within an industrial plant Starting large motors in same or neighbouring facility Typical results: Electronic controls trip or reset, VFDs trip, HID lighting and UV lights go out, computers reset or switch off, plcs trip, electric motors stop Click here for more information on Voltage Sags Over Voltage or Swells Voltage Swell or Surge A voltage swell is an increase in RMS voltage at the power frequency for durations from 0.5 cycles to 1 minute and can occur on any combination of phases. It is typically described by the voltage magnitude and the duration of the swell event. Typical causes: Switching off large motors or switching capacitors on site or on network Typical results: VFDs may trip on overvoltage Potential increased long term deterioration of insulation systems Click here for more information on Voltage Swells Prolonged Over Voltage Is an increase in RMS voltage at the power frequency for more than a few minutes. Typical causes: Capacitors remaining on utility line at times of low electrical demand Typical results: VFDs trip on overvoltage UPS systems go to battery supply and batteries are soon exhausted Potential long term increased deterioration of insulation systems Voltage Unbalance Is defined by NEMA as where all voltages are measured line to line. Typical causes: Unbalanced distribution of single phase loads Phase-to-phase loads Unbalanced 3-phase loads Unequal impedance of cable runs or distribution lines Typical results: Current unbalance in 3-phase induction motors can be several times the value of the voltage unbalance, leading to motor overheating and loss of efficiency Overheating reduces insulation life, causing premature failure of the motor VFDs may be damaged or in some cases trip Click here for more information on Voltage Unbalance Power Outages A power outage is a complete loss of voltage for more than a few minutes. If the interruption is less than a few minutes it is typically called a momentary. Typical causes: Utility lines or equipment damaged by vehicles (e.g. collision with poles), by animals or weather ñ insulators, lines or transformers damaged Typical results: No electrical power for an extended period Flicker The perceived or real change in brilliance of lighting as a direct result of sudden changes in incoming voltage. The closer the voltage variation is to 8.8Hz, the more noticeable the resultant disturbance becomes. Typical causes: Arcing devices such as furnaces or arc welding Cyclo-converters and static frequency converter Large induction motors with rapidly fluctuating loads ñ rock crushers, log chippers, mine hoists. Typical results: Flicker can induce severe headaches and nausea to those exposed to it In extreme cases, can induce epileptic fits in those who may be susceptible Click here for pdf brochure on Flicker Correction Solutions Click here for more information on Flicker Power Conditioning A power line conditioner, as defined by IEEE, is a device that combines one or more "power enhancement" attributes. This implies that the power quality may need enhancement. Typical problems: Voltage Sags Voltage unbalance Over voltage Voltage harmonics Power Outages Typical results: Unplanned production stoppages Long term damage to equipment Voltage Harmonics Voltage Harmonics are voltages occurring at integer multiples of the fundamental frequency. To clarify: If the fundamental frequency is 60Hz, the third harmonic will be at 3X60=180Hz, the fifth at 300Hz, etc. Typical causes: Harmonic currents created by non-linear devices such as rectifiers and power electronics. Arcing devices such as furnaces and welders. Typical results: Waveforms are distorted and in severe cases electronic devices, such as drives, can malfunction or trip. Computer systems and electronic controls can reset causing production stoppage Click here for more information on Voltage Harmonics Frequency Conversion In North America, electrical equipment for use on normal utility supplied power is designed for an AC system with a frequency of 60Hz. In Europe and much of the rest of the world , the standard frequency is 50Hz. While it is possible to design some equipment to run on either frequency this is not always so and it may be necessary to convert power from one voltage and frequency to another voltage and frequency. Traditionally, frequency conversion was achieved using specially designed motor generator sets where the motor ran at one frequency, e.g. 50Hz, and drove a generator at a second frequency, e.g. 60HZ. In some cases it was possible to change voltage to the desired value by this method Modern technology uses rectifier and inverter technology to convert both voltage and frequency Click here for more information on Fequency Conversion Solutions Power Factor Control Power factor can be expressed as the ratio of Usable Power in kW divided by Total Power supplied in kVA so Poor Power Factor kVAR component is significant Typical causes: Significant proportion of electrical load comprises motors & transformers with magnetic coils causing lagging power factor Induction motors are running lightly loaded Typical results Excessive heating of components such as transformers Power bills frequently include penalties for poor power factor Typical Solution Addition of suitable capacitors with leading power factor reduce the net value of the kVAR and allow usable kW to approach kVA value. New Solution Addition of all electronic VAR controller (no capacitors) to correct pf Click here for more information on electronic VAR solutions VAR Support When starting large motors the power factor falls to low levels, typically <0.3 during the first few seconds which can cause voltage sags and system instability for neighbouring circuits. The solution is to provide VAR support either by use of suitable switched capacitors or by use of an all electronic VAR support systems. Click here for more information on VAR support solutions Phase Shift In 3-phase systems the three phases, both current and voltage should be 120 degrees apart. Any variation from 120 degrees especially in the voltage systems will cause instability in the load that it is feeding. In the case of motors they will draw extremely high current that will eventually burn out the windings. Other loads such as rectifiers, drives etc. will suffer different fatal consequences. Controlling the phase balance and hence the phase shift of the electric supply WILL improve the system efficiency and reliability. Regenerative Loads Regeneration is power produced by loads that have high inertia or are driven by some other force such as mechanical loads. In regenerative mode, power flow is from the load to the electric supply. This is unusual as most loads consume power and, hence, most equipment designed to be used with these loads cannot handle this reverse current situation. Equipment such as UPS systems will actually be damaged by a regenerating load.		Power sags and brownouts create serious and costly production problems.

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