1. The voltage variation range is too large
The grid power supply is insufficient, and the power supply department
adopts step-down power supply, or it is located in a remote area and suffers
from excessive losses, resulting in low voltage. The power grid uses too little
electricity, causing the voltage to be too high
If the voltage is low, the load will not work properly. If the voltage is
too high, the service life of the load will be shortened or the load will be
burned.
2. Waveform distortion (or harmonic Waveform.DistorTion)
Pervasive waveform distortion refers to the multiple harmonics of the
standard power supply waveform. The cause of grid harmonics is the use of
switching power supplies in power electronics and electrical equipment such as
rectifiers, UPS power supplies, electronic speed control equipment, fluorescent
lighting systems, computers, microwave ovens, energy-saving lamps, dimmers, etc.
or the secondary power supply itself.
The harm of harmonics to public power grids mainly includes:
1) The components in the public power grid generate additional harmonic
losses, which reduces the efficiency of power generation, transmission and
transformation equipment. When a large amount of third harmonics flows through
the neutral line, it will cause overheating of the line or even a fire;
2) Affects the normal operation of various electrical equipment. In
addition to causing additional losses, it can also cause mechanical vibration,
noise and overvoltage in the motor, cause serious local overheating of the
transformer, cause overheating of capacitors, cables and other equipment, cause
insulation aging, and shorten service life. causing damage;
3) It will cause local parallel resonance and series resonance in the
public power grid, thereby amplifying the harmonics, greatly increasing the
aforementioned hazards, and even causing serious accidents;
4) It will cause relay protection and automatic devices to malfunction, and
make electrical measuring instruments inaccurate;
5) It will cause interference to adjacent communication systems. In the
mild case, it will generate noise and reduce the communication quality. In
severe cases, it will cause information loss and make the communication system
unable to work normally.
3. Surges (or PowerSurges)
It means that the effective value of the output voltage is 110% higher than
the rated value in an instant (a few milliseconds) and lasts for one or several
cycles. It is the main culprit of damaging precision electronic equipment. In
addition to being caused by lightning strikes, it is also mainly due to the high
voltage generated by the sudden unloading of the power grid when large
electrical equipment connected to the power grid is turned off and on.
Dangers of power surges:
With the development of computer technology, multi-layer, ultra-large-scale
integrated chips have dense circuits, and the trend is towards higher
integration, smaller gaps between components, and thinner wires. A few years
ago, a square centimeter of computer chip had 2,000 transistors; today's Pentium
machines have over 10,000,000. This increases the probability that the computer
will be damaged by a power surge. Due to the design and structure of the
computer, it should operate within a specific voltage range. When the power
surge exceeds the level that the computer can withstand, the computer will have
garbled data, damaged chips, and premature aging of components. These symptoms
include: unexpected data errors, failure to receive/transmit data, lost
documents, abnormal work, and frequent Needs for repairs, unexplained
malfunctions, hardware problems, etc. Lightning surges far exceed the level that
computers and other electrical equipment can withstand. In most cases, they
cause immediate damage to computers and other electrical equipment, or permanent
loss of data. Even a small 20-horsepower induction engine can generate a
3,000-5,000 volt surge when starting or shutting down, causing damage or
interference to computers that share the same power distribution box with each
surge. The number of surges is very frequent.
The effects of surges on sensitive electronic and electrical equipment
include the following types:
destroy
Voltage Breakdown Semiconductor Device
Destroy the metallized surface of components
Damage to printed circuit board traces or contacts
Destroy triac/thyristor...
interference
Lockup, thyristor or triac loss of control
Data file is partially damaged
Data handler error
Errors and failures in receiving and transmitting data
Unexplained failure...
premature aging
Parts age prematurely and the life of electrical appliances is greatly
shortened.
Output sound quality and picture quality deteriorate
●What electrical equipment will be damaged by power surges?
Electrical equipment containing microprocessors is extremely susceptible to
damage by surges, including computers and auxiliary equipment, program
controllers, PLCs, fax machines, telephones, answering machines, etc.;
program-controlled switches, radio and television transmitters, film and
television equipment, microwaves Relay equipment; products in the home appliance
industry include televisions, stereos, microwave ovens, video recorders, washing
machines, dryers, refrigerators, etc. Survey data shows that 63% of electrical
equipment that has problems during the warranty period are caused by power
surges.
4. Spikes (or high-voltage spikes)
Refers to the voltage with a peak value of 6000V and a duration from one
ten thousandth of a second to one half cycle (10ms). This is mainly caused by
lightning strikes, arcing, static discharge or switching operations of large
electrical equipment.
harm:
This kind of peak interference is particularly harmful in steel mills,
rolling mills or places where thyristor equipment, EDM equipment, electric
locomotives are used extensively. The large amplitude can reach hundreds of
volts or even thousands of volts, and the pulse width is generally on the order
of μS. Lightning also often invades in the form of spikes. When the peak pulse
amplitude is very large, it will destroy the input filter, rectifier and even
the main oscillator of the switching power supply of the industrial computer. In
addition, its spectrum is very wide, and it will also enter the computer and
cause interference.
5. Transient overvoltage and temporary overvoltage
It refers to a pulse voltage with a peak voltage as high as 20,000V but a
duration ranging from one millionth to one thousandth of a second. The main
cause and possible damage is similar to high-voltage spikes, mainly caused by
lightning.
harm:
Advanced electronic equipment such as measurement, monitoring, protection,
communication, and computer networks with large-scale integrated circuits as
core components are widely used in various fields of power, special, special,
communications, radio and television, finance, transportation, petrochemicals,
medical and other modern life. , these electronic devices composed of large CMOS
integrated components generally have the disadvantage of weak tolerance to
transient overvoltage and overcurrent. Transient overvoltage will not only cause
malfunction of electronic equipment, or cause interference to electronic
equipment, Data loss or temporary paralysis; in severe cases, it can cause
component breakdown and circuit board burnout, paralyzing the entire system.
6. Voltage sags/drops (Sags & Brownouts)
It refers to a low-voltage state in which the effective value of the mains
voltage is between 80-85% of the rated value, and lasts for one to several
cycles, or even longer. The causes include: starting and application of large
equipment, starting of large motors, or access to large power transformers, main
power line switching, line overloading, etc.
harm:
Voltage sag is the most common electrical problem, accounting for 87% of
electrical problems. The power supply may cause a short-term voltage drop for
some reason. Its impact on the computer ranges from causing the keyboard and
other interface devices to suspend operations, to causing data loss and file
destruction. The voltage sag will also damage the components in the computer and
shorten its life.
7. Three-phase voltage imbalance
It refers to the unequal voltage or unequal phase angle between phases,
which is caused by the unbalanced load of each phase.
The harm and impact of three-phase imbalance
Three-phase unbalance refers to the voltage asymmetry of each phase of the
three-phase power supply. It is caused by the unbalanced load added by each
phase power supply, which is a fundamental load configuration problem. The
occurrence of three-phase unbalance is related to user load characteristics, and
is also related to the planning and load distribution of the power system.
"Power Quality Three-Phase Voltage Allowable Unbalance" (GB/T15543-1995) is
applicable to AC rated frequency of 50 Hz. In the normal operating mode of the
power system, the voltage imbalance at the PCC point connection point is caused
by the negative sequence component. The standard stipulates that the allowable
value of unbalance in the normal operation mode of the power system public
connection point is 2%, and it shall not exceed 4% in a short period of
time.
Harm to transformers. In production and daily electricity consumption, when
the three-phase load is unbalanced, the transformer will operate in an
asymmetrical state. Causes the loss of the transformer to increase (including
no-load loss and load loss). According to the transformer operating regulations,
the neutral current of the transformer during operation shall not exceed 25% of
the rated current of the low-voltage side of the transformer. In addition,
unbalanced operation of the three-phase load will cause the zero-sequence
current of the transformer to be too large, increase the temperature of local
metal parts, and even cause the transformer to burn out.
Impact on electrical equipment. The occurrence of three-phase voltage
imbalance will lead to the occurrence of current imbalance reaching several
times. It induces an increase in reverse torque in the motor, causing the
temperature of the motor to rise, efficiency to drop, energy consumption to
increase, vibration to occur, and output loss to occur. The imbalance between
phases will shorten the service life of electrical equipment, accelerate the
replacement frequency of equipment parts, and increase the cost of equipment
maintenance. The margin of current allowed by the circuit breaker is reduced,
and overload and short circuit phenomena are prone to occur when the load
changes or alternates. Excessive unbalanced current flows into the neutral wire,
causing the neutral wire to thicken.
Effect on line loss. In the three-phase four-wire connection method, when
the three-phase load is balanced, the line loss is the smallest; when one phase
is heavily loaded and the two-phase load is light, the line loss increment is
small; when one phase is heavily loaded and one phase is lightly loaded, When
the load of the third phase is an average load, the line loss increment is
larger; when one phase is lightly loaded and the two phases are heavily loaded,
the line loss increment is the largest. When the three-phase load is unbalanced,
no matter what the load distribution situation is, the greater the current
imbalance, the greater the line loss increase.
8. Noise interference (or noise Noises)
Refers to radio frequency interference (RFI), electromagnetic interference
(EFI) and other types of high frequency interference. Originated from
electromagnetic wave or high-frequency wave induction, it is a high-frequency
change, ranging from 15-100% potential disturbance at the 50Hz frequency of
normal power. Noise is caused by motor operation, breaker operation, motor
controller operation, broadcast emissions, microwave radiation and electrical
storms.
harm:
Excessive noise may cause the computer CPU to misjudge. In severe cases,
the CPU and other computer accessories may be burned out, and radio transmission
may be interrupted.
The induction is conducted to the surrounding environment, causing other
electronic equipment to fail to work properly.
It can cause civil aviation system failure, poor communication, computer
operation errors, and automatic equipment malfunction.
AQIS AC parametric power comprehensive regulator plays an important role in
improving the power supply quality of the distribution network. The device has
the following functions: (1) Maintain a constant load-side voltage under the
condition of primary-side voltage fluctuation or 2-3 cycle short-term power
outage; (2) Maintain the three-phase load-side voltage under unbalanced and
harmonic conditions of the primary-side voltage. Voltage balance; (3) It can
compensate the current harmonics and reactive power on the load side, so that
the grid side only provides active current; (4) It can compensate the unbalanced
current harmonics on the load side, so that the grid side current is three-phase
balanced;
(5) Various microscopic power interference pollution can be eliminated.
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