How to control the problem of shaking electricity to ensure the continuous operation of production

1.
Preface With the technological update of electrical equipment, especially the large-scale application of digital automatic control technology in industrial production, such as the large use of frequency converters, PLCs, automated production lines and computer systems and other electrical equipment, higher requirements
are put forward for the voltage quality of the power supply system.
A short period of voltage reduction may lead to the shutdown of electrical equipment, causing enterprises to suffer huge economic losses
.
Voltage sag and short-term interruption have become more important power quality problems faced by developed countries in Europe and the United States, and the impact of such problems is becoming more and more prominent
in China's industrial enterprises.
Keywords: voltage sag; shaking; Motor protection 2.
The hazard of voltage sag The scientific name of sloshing electricity is voltage sag (voltage sag/dip), which refers to the phenomenon
that the reasonable value of the power supply voltage suddenly drops in a short period of time and then returns to normal operation.
For the index of voltage sag, there is no unified standard definition
in the world.
The International Institute of Electrical and Electronics Engineers (IEEE) defines voltage sag as the reasonable value of the supply voltage falling to 90%~10% of the rated value, and the duration is 10ms~1min; The International Electrotechnical Commission (IEC) defines it as dropping to 90%~1% of the rated value and lasting 10ms~1min
.
Some users and facilities that are very sensitive to voltage dips (such as semiconductor industry, electronic numerical control equipment, variable speed transmission motor devices, IT industry equipment companies, etc.
) once the voltage dip occurs, the loss will be huge
.
As an important control switch device of low-voltage distribution network, contactor bears an important responsibility
in the continuous and stable operation of enterprises.
In the terminal low-voltage motor circuit, the contactor contacts may spring open during the voltage drop, and cause the associated locking equipment to act, resulting in the production line stopping, causing huge economic losses
to the enterprise.
For petroleum, chemical and other industries with a large number of continuous production equipment, shaking electricity produces a series of consequences
such as safety, environmental protection, waste, raw material waste, reduced output, and low efficiency.
The power quality problems caused by the phenomenon of shaking electricity have been paid more and more attention
by electricity enterprises in recent years.
3.
The inevitability of voltage sag There are many reasons for voltage sudging, such as unpredictable lightning strikes
on the power system.
Accidental collision of animals and foreign objects, line failures caused by strong winds and other natural environmental factors, and phenomena caused by power supply failure
.
The transient power failure or voltage dip caused by these faults is still not completely avoidable in the current power system, and the probability of voltage dip is much higher than that of a complete power failure
.
Power users are beginning to realize that blindly asking power companies to improve power supply reliability from the power supply side is of little significance to solve voltage sags
.
Therefore, the focus is gradually on the equipment provided by equipment manufacturers to have good resistance to voltage sag, and strive to solve the impact
of power dip from the equipment inside the enterprise user.
4.
Electricity control The voltage plummet from the source of power supply to the treatment of the entire production line, the treatment of the equipment level, and then to the treatment of the equipment control level, and the treatment cost has decreased
in an order of magnitude.
Therefore, from the perspective of treatment cost and rationality, it is more recommended to treat at the end of the equipment, and even the electrical control components that go deep into the equipment are buried
.
The closer to the end of treatment, the less cost is spent and the same treatment effect
can be achieved.
This article introduces the solutions of Accuray motor protection products and anti-shaking devices to resist the shaking of terminal equipment, and reasonably avoid the shutdown of motor equipment due to shaking
.
5.
The current anti-shaking solution for the end contactor is mainly divided into two types
: shaking hold and shaking restart.
The holding type can be implemented
by online UPS or a stand-alone module.
The use of UPS centralized power processing, the reliability of UPS requirements are high, once there is a problem, will lead to the failure
of the entire power network.
The advantages of adopting a stand-alone module method will not affect the control voltage of other circuits if the problem problem occurs
.
Re-start type is a compensation scheme, when the voltage sag time is long, the motor has been stopped, you can use batch delay to start the motor again, to avoid simultaneous starting caused by system voltage shock
.
5.
1 Motor protector with anti-shaking function For motor circuits that require comprehensive measurement and protection, a motor protector with anti-shaking function can be selected, with the function code "SU"
.
While realizing electrical parameter measurement, protection, control and communication networking, the protector continuously supplies power
to the protector when shaking occurs.
The output of the protector relay can be maintained for a period of time (0.
0-10.
0s adjustable) after release, during which the voltage is restored, the contactor is automatically sucted, otherwise it enters the re-start stage, the voltage is restored within the preset allowable time, and the starting relay is closed with a delay to make the contactor re-close to realize the motor re-start
.
By setting the restart parameters reasonably, the motor can be delayed and started again in batches
.
Typical Secondary Wiring Diagram Product Picture ARD3M Motor Protector 5.
2 Anti-sloshing device For circuits that only need to realize anti-sloshing protection or have installed a motor protector without anti-sloshing function, ARD-KHD-S03 series anti-sloshing device
is optional 。 ARD-KHD-S03A has the function of "shaking hold + restarting", when shaking occurs, the device continues to supply power to the contactor coil to maintain its continuous pull-in, during which the voltage is restored and the motor continues to run; After the holding time is exceeded, the contactor is released, entering the "restart start" stage, and when the voltage is restored within the set time, the device outputs a restart start signal, so that the contactor is re-engaged to achieve restart start
.
The device has an energy-saving output mode to reduce power consumption and noise
in the control loop.
Typical secondary wiring diagram product picture ARD-KHD-S03A anti-shaking device 6.
Conclusion The motor protector with anti-shaking function and the ARD-KHD-S03A anti-sloshing device can reasonably resist the equipment shutdown caused by shaking, each with its own advantages, and compared with source control, the cost is lower and more targeted, which is an ideal choice for enterprise governance anti-shaking problem and ensuring production continuity
。 References: (1) Enterprise Microgrid Design and Application Manual 2020.
06(2)GB 14048.
4-2020 "Low-voltage switchgear and control equipment Part 4-1: Contactors and motor starters Motor contactors and motor starters (including motor protectors)" (3)JB/T 10736-2007 《Low-voltage motor protector》