Ieee std 1159-1995, ieee recommended Practice for Monitoring Electric Power Quality

5.5.5 Waveform distortion
Harmonic current injection from customer loads into the utility supply system can cause harmonic voltage
distortion to appear on the utility system supply voltage. This harmonic current and voltage distortion can
cause overheating of rotating equipment, transformers, and current-carrying conductors, premature failure or
operation of protective devices (such as fuses), harmonic resonance conditions on the customerÕs electric
power system, which can further deteriorate electrical system operation, and metering inaccuracies. Har-
monic voltage distortion on a utility system can cause the same problems to a customerÕs equipment and can
cause overheating of utility transformers, power-carrying conductors, and other power equipment. [B13]
outlines typical harmonic current limits for customers and harmonic voltage limits for utility supply voltage
that customers and utilities in general should attempt to operate within in order to minimize the effects of
harmonic distortion on the supply and end-user systems. 

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IEEE
MONITORING ELECTRIC POWER QUALITY
Std 1159-1995
29
5.5.6 Voltage ßuctuations
Fluctuations in the supply voltage are most often manifested in nuisance variations in light output from
incandescent and discharge lighting sources. A sudden voltage decrease of less than 1/2% can cause a
noticeable reduction in light output of an incandescent lamp and a less noticeable reduction in light output of
gaseous discharge lighting equipment. Voltage ßuctuations less than 7% in magnitude have little effect on
other types of customer loads [B11].
5.5.7 Power-frequency variations
In general, utilities maintain very close control of the power system frequency. Slight variations in frequency
on an electric system can cause severe damage to generator and turbine shafts due to the subsequent large
torques developed. In addition, cascading system separations can result with even slight deviations in
frequency since electric systems are closely connected and operate in synchronism. Frequency variations are
more common on customer-owned generation equipment systems. Generator over-speed can result in a
frequency increase on small systems operating independent of utility sources.
Frequency synchronization errors can sometimes occur on a customer feeder that serves large rectiÞer loads.
These loads can cause voltage notching severe enough to register extra zero crossing events on electronic
loads that count zero crossings of the ac voltage to obtain frequency. While these events are recorded as fre-
quency errors by electronic controllers, the fundamental frequency has not changed.