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EFFECTS VOLTAGE SAG ON SINGLE-PHASE DOMESTIC AND OFFICE LOADS
Mahendra V Chilukuri, Lee Ming Yong and Phang Yoke Yin
Faculty of Engineering, Multimedia University, Cyberjaya 63100, Malaysia
Abstract: This paper presents the effects of voltage sags on domestic and office
equipment and provides equipment sensitive curves for safe and reliable operation based
on the experimental results. With the increase usage of sensitive electronic equipments in
various industries, offices and household appliances, it is important to protect them from
any power quality disturbances to avoid unnecessary losses of any kind. From the several
types of power quality disturbances, the most frequent and concern for electric utilities
from customer point of view was voltage sag. Though a lot of research has been done
voltage sag characteristics and its effects on industrial equipment there is not much
literature available on the effect of voltage sags on single-phase loads, especially office
and home equipment. This project investigates the behavior of domestic and office
appliances for different magnitude, duration and angle of incidence of voltage sag.
Studies were conducted to obtain the sag tolerance curves which might or might not
comply with the voltage sag immunity standards. Industrial power corruptor was used to
generate voltage sag on one phase to observe the effects on the test equipment.
Experiments were conducted on common office and household appliances using
Industrial Power Corruptor (IPC) to monitor the equipment function and performance
before, during and after the sag. The current and voltage waveforms obtained from the
IPC software were analyzed and reported. The results seem to be useful and informative
for OEMs, Utilities and Emergency Power Supply Manufacturers.
Index Terms—Power Quality, Voltage Sag, Industrial Power Corruptor, Power System Faults.
1 INTRODUCTION
Deregulation and privatization of electricity industry lead to the open competition to
provide electricity at higher reliability and quality then ever before to growing
automotive industry. The increased use of ICT and semiconductor devices at home and
1
offices has increased the challenges for utility and industry to focus on power quality.
Though there are many types of power quality disturbances arising in electric
transmission and distribution system some of them or more frequent than other. Voltage
sag is one of the major power quality problem faced by the customers and requires
solutions at utility and customer level along with some radical changes at design of
equipment. Voltage sag is defined as more than 10% reduction in rms voltage from 0.5
cycles to 1 minute. The IEC definition for this phenomenon is dip [1]. Many high-tech
electricity-dependent devices and equipment used in commercial and industrial facilities
are sensitive to many types of power quality disturbances. On the other hand, the
increasing use of power electronics devices contributes further to the arising power
quality problems.
1.1 Voltage Sag Standards
Standards are needed for the effects of voltage sags on sensitive electronic equipment as
reference documents describing single equipment or component and systems in power
system. Both buyers and manufacturers use these standards to meet better power
compatibility. Manufacturers refer to the standard to manufacture products complying
requirement of the standard and buyers demand from the manufacturers that the product
should comply with the standard. The most common standards dealing with power
quality are IEEE, IEC, CBEMA and SEMI. Brief description of each standard is provided
as following.
1.2 IEEE Standards
IEEE Standard P1346 - Electric Power System Compatibility with Electronic Process
Equipment. This standard contains indices that will allow industrial engineers to evaluate
how sensitive their industrial processes will be to voltage sags. In addition, “IEEE
Standard 446-1995 - Recommended practice for emergency and standby power systems
for industrial and commercial applications range of sensibility loads”, includes the
CBEMA curve to show the equipment susceptibility to voltage sags. Due to the increase
of sensitive equipments, the voltage sag limit in the CBEMA curve might not be
restrictive enough to protect some type of sensitive equipments. IEEE Standard 1159 -
Recommended Practice for Monitoring Electric Power Quality defines a sustained
interruption as reduction in the rms voltage to less than 10% of the nominal voltage for
2
longer than 1 minute. Sustained interruptions must be taken seriously as the fault will
cause disturbances and affect all the customers on the faulted section [8].
1.3 SEMI
The SEMI International Program is a service offered by Semiconductor Equipment and
Materials International (SEMI). It represents the semiconductor and flat panel display
equipment and materials industries with the goal of helping members expand global
marketing opportunities and improve customer access. The SEMI F47-0200 standard,
entitled “Specification for Semiconductor Processing Equipment Voltage Sag Immunity”
defines the desired voltage sag immunity for single and two-phase voltage sag events. It
only specifies voltage sags with duration from 50ms up to 1s. The specification states that
Semiconductor processing, metrology and automated test equipment must be designed
and built to conform to the voltage sag ride through capability per the defined curve in
the figure 1.1.
Figure 1.1 Required Semiconductor Equipment Voltage Sag Ride through Capability Curve (SEMI F47) [9]
1.4 Causes of Voltage Sag
The causes of voltage sag can be divided into two categories, depending on the location
of the source in relationship to the power meter. Faults can happen on the utility side of
the meter which includes switching operations, power system faults, regulator
dysfunction and lightning. While on the end user side of the meter, the faults include
nonlinear loads, poor grounding, electromagnetic interference and static electricity.
1.4.1 Utility side of the meter
3
Voltage sag caused by the utility side of the meter usually involve some type of activity
on the utility’s electrical power system either man made (switching operation) or natural
(lightning) events where both involve interruption of the voltage. Utilities switch
equipment on and off by the use of circuit breakers, disconnecting switches or reclosers.
Breaker trips when there is a fault on the power system or when breaker is due for
maintenance such as to insert capacitor for power factor improvement. As for natural
causes, lightning striking power line or substation equipment, tree or animal touching a
power line, car hitting a power pole, construction work may be cause of the faults. The
tripping of the breakers and the initiating fault will cause voltage to sag or swell
depending on the magnitude of the voltage and duration when it occurs. Faults on utility
side are usually categorized by single phase to ground faults, phase to phase faults or
three-phase to ground faults. The most common occurring faults is single phase to ground
and the possibility of three-phase fault occurring is very low.
1.4.2 End user side of the meter
Problems on the end user side of the meter usually happen when a disruption of
sinusoidal voltage and current is delivered to them by the utility. Faults also occur when
there’s excessive use of nonlinear load, starting of big motor which draws large amount
of current and causes voltage sag. These disturbances will affect the performance of
sensitive equipment but won’t damage them except for faults caused by transient that will
damage the equipments.
2 EXPERIMENTAL HARDWARE SETUP
2.1 Experimental Setup
In studying the effect of voltage sag on motor load domestic and IT-based equipment, a
voltage sag generator is required to initiate voltage sags. The voltage sags are generated
using the Industrial Power Corrupter (ITC) combined with a built in data acquisition
system. By using IPC, the user can control the depth and duration of voltage sags while
monitoring voltages, currents and other signals. Besides that, there were also 9 built in
standards in the IPC which are SEMI 47, CBEMA, ITIC, IEC 4-11, IEC 4-34, MIL1399,
Samsung, FAA1.3.2, FAA IPTE and F47 RQRD [11]. Among the 9 standards readily
available in the IPC, only 5 standards were used for testing in this study. SEMI 47 is an
industry standard for voltage sag immunity. Industrial equipment must tolerate voltage
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sags on the AC mains supply to specific depths and duration. ITIC and CBEMA is used
for voltage sag immunity on computer, telecommunications, business equipments,
software and IT services. As for IEC 4-11 and IEC 4-34, both standards specify the same
depths and durations of voltage sags which test the toleration of equipments rated up to
16A and more than 16A per phase separately. The 3-phase supply from the utility is
connected to the IPC and from the IPC, the 3-phase output is connected to load as shown
in Figure 2.1. Three single phase socket for each phase is also fed by the IPC. True
phase-to-phase sags can be generated. It must be connected to a computer running the
IPC software and is controllable from the computer using graphical software that is based
on a Windows operating system. The main functions of the software are:
Figure 2.1 IPC connected to 3 phase power supply
1. Control the sag magnitude
2. Control the sag duration
3. Trigger a sag event
4. Download and display data that was acquired on selected channels during the sag
events for further analysis.
2.2 Test Procedure
The following are the test procedure followed to perform testing on motor, domestic and
IT-based loads to study the effect of voltage sags.
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1. Define “Pass” and “Fail” for each equipment before conducting test
2. Connect the load to the 3 pin power supply socket
3. Select the suitable standard to be used for testing the equipments
4. Follow each pre-defined steps of the standards and trigger each sag event
5. Vary the sag duration and magnitude to find the threshold of the equipment where
it fails.
6. For each sag event triggered, voltage and current is recorded and the data can be
viewed using the Channel Scope software.
7. Plot a threshold vs. standard to compare whether the equipments tested complied
to the standard or not.
The recorded waveforms are analyzed and conclusions are derived based on the
waveforms and observations recorded.
2.3 Computation for Power Quality Parameters
The computation for some of the power quality parameters are explained as follows:
a) Voltage sag and swell detection:
Sag detection method used in this project was based on IEEE standard 1159 [1],
where RMS voltage below 0.9 p.u. of the system voltage is considered as voltage sag.
The sag duration was calculated from the time either one of the phases dropped below
the minimum voltage limit until all of the three phases recovered within voltage limit.
6
Figure 2.2 Type of fault observed from TNB PQMS data.
Figure 2.3 The occurrence of fault for 1 year from Jun 2005 – July 2006 at one PQ monitoring site (UKM, Bangi).
3 Experimental Results
The main purpose of conducting experiments on various equipments is to study the
effects of voltage sags on their operation and determine voltage tolerance curve for
equipment. For this experiment, the equipments are divided into the following categories:
a) Industrial equipment: 3 phase induction motor, VSD
b) Domestic equipment: electric kettle, electric oven, automatic rice cooker, television,
lightings, decoder, massager, fan, microwave oven, blender and UPS.
c) IT equipment: Hub, inkjet printer, laser printer, LCD monitor, scanner, computer and
CRO
The voltage sag magnitude and duration based on the pre-determined steps in each
standard had been investigated. As mentioned in the chapter No, the sags were generated
using IPC. The sag thresholds where the equipments fail were also determined by
adjusting sag magnitude and duration on the front panel of IPC.
7
3.1 Experiments on PC
Voltage sag doesn’t show any significant problem to personal computers. In such case, it
is easy to prevent the problem by installing uninterruptible power supply (UPS) for a
small cost which will provide sufficient time to save all the data before shutting down.
However it is not the same especially for PC-based offices which rely entirely on data
processing through PC in their work. An interruption will cause great losses; some
examples are financial trading and telecommunication offices.
a) Computer A
Intel Pentium II Processor
128MB RAM
4GB Hard Disk
Windows 98 OS
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Figure 3.1(a) Corresponding current and voltage of computer during voltage sag period
for 70% depth and 10-cycle duration, computer didn’t restart due to sag.
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Figure 3.2(b) Corresponding current and voltage waveform of computer during voltage
sag period for 40% depth and 30-cycle duration, computer restarts due to sag.
Figure 5.3(a) shows the current and voltage waveform when computer A is running and
during the application of sag. Its load current before sag value is 2.5A. The restart of
computer A is marked by high current surge of 9 times the normal current, which is
indicated at the end of sag which can be seen in figure 5.3(b), for sag depth 40% and
duration of 30 cycles. It is observed that the value of current surge at the end of the sag is
higher compared to the case which computer A is not affected by sags. The value of the
spike is 22A in figure 5.3(b) when the computer restarts as compare to 14A in figure
5.3(a) when there is no effect of sag on the computer.
3.2 Computer B
Pentium (R) 4
504 MB RAM
80GB Hard Disk
Windows XP OS
Figure 5.4(a) shows the current and voltage waveform when computer B is running and
when sag is applied. Its load current before sag value is 1.5A. Computer B restarts at a
sag depth of 15% and 18-cycle duration. It is observed that there is a current surge at the
end of the sag when computer B restarts and no current surge in figure 5.4(b) when
computer B is not affected to sag. The value of the spike is 15A in figure 5.4(b) when the
computer restarts as compare to 5.5A in figure 5.4(a) when there is no effect of sag on
computer B.
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Figure 5.4(a) Corresponding current and voltage waveform of computer during voltage
sag period for 70% depth and 1-cycle duration, computer didn’t restart due to sag.
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Figure 5.4(b) Corresponding current and voltage waveform of computer during voltage
sag period for 15% depth and 18-cycle duration, computer restart due to sag
Voltage sag can cause computers to restart and lose data. If the depth of voltage sag is larger than 40% and duration is more than 5 cycles for computer A, it will restart. Computer B will restart if the depth of sag is larger than 15% and a duration of more that 18-cycles. Voltage sag has no effect on computer for voltage sag and duration before the indicated value. From the experiment, it can be concluded that the specification of the computer plays an important role on the sag effect. It is shown that the latest model of the computer has higher ride through capability of voltage sag than the later model. Both computers comply with the voltage sag immunity standards. Similar experiments were conducted and on various domestic an office appliances and the following sag immunity table were obtained to analyze the behavior and function of the equipment.
TABLE 1: EFFECT OF VOLTAGE SAG ON THE RESTARTING OF COMPUTER A COMPARISON
Sag Depth
(%)
Sag Duration (in cycles)
5 10 20 30 40 60
10
70 N N N N N N
60 N N N N N N
50 N N N N N N
40 N Y Y Y Y Y
N: Computer does not restart due to sag
Y: Computer restarts due to sag
TABLE 2: EFFECT OF VOLTAGE SAG ON THE RESTARTING OF COMPUTER B
Sag Depth (%)
Sag Duration (in cycles)
5 10 20 30 40 60
25 N N N N N N
20 N N N N N N
15 N N Y Y Y Y
10 N N Y Y Y Y
N: Computer does not restart due to sag
Y: Computer restarts due to sag
TABLE 3: EFFECT OF VOLTAGE SAG ON THE PRINTER A
Sag
Depth
(%)
Sag Duration (in cycles)
5 10 20 30 40 60
30 N N N N N N
20 N N N N N N
10 N N N N N N
11
0 N Y Y Y Y Y
N: Printer doesn’t switch off due to sag
Y: Printer switches off due to sag
TABLE 4: EFFECT OF VOLTAGE SAG ON THE PRINTER B
Sag
Depth
(%)
Sag Duration (in cycles)
5 10 20 30 40 60
25 N N N N N N
20 N N N N N N
15 N N Y Y Y Y
10 N N Y Y Y Y
N: Printer doesn’t switch off due to sag
Y: Printer switches off due to sag
TABLE 5: EFFECT OF VOLTAGE SAG ON THE NETWORK HUB
Sag
Depth
(%)
Sag Duration (in cycles)
5 10 20 30 40 60
30 N N N N N N
20 N N N N N N
10 N N N N N Y
12
0 Y Y Y Y Y Y
N: Hub doesn’t switch off due to sag
Y: Hub switches off due to sag
TABLE 6: EFFECT OF VOLTAGE SAG ON LCD MONITOR
Sag
Depth
(%)
Sag Duration (in cycles)
5 10 20 30 40 60
25 N N N N N N
20 N N N N N N
15 N N Y Y Y Y
10 N N Y Y Y Y
N: LCD monitor doesn’t switch off due to sag
Y: LCD monitor switches off due to sag
TABLE 7: EFFECT OF VOLTAGE SAG ON THE SCANNER
Sag
Depth
(%)
Sag Duration (in cycles)
5 10 20 30 40 60
25 N N N N N N
20 N N N N N N
15 N N N N N N
13
10 N N Y Y Y Y
N: No effect on scanner due to sag
Y: Scanner stops operating and operation had to be restarted
TABLE 8: EFFECT OF VOLTAGE SAG ON L INCANDESCENT LAMP
Depth
(%)
Sag Duration (in cycles)
5 10 20 30 40 60
40 N N N N N N
30 N N N N N N
20 N N Y Y Y Y
10 N N Y Y Y Y
N: No effect on lamp due to sag
Y: Lamp switches off due to sag
TABLE 9: EFFECT OF VOLTAGE SAG ON ELECTRIC RICE COOKER
Sag
Depth
(%)
Sag Duration (in cycles)
5 10 20 30 40 60
50 N N N N N N
40 N N N N N N
30 N N N N N N
14
20 N Y Y Y Y Y
N: No effect on rice cooker due to sag
Y: Rice cooker switches off due to sag
TABLE 10: EFFECT OF VOLTAGE SAG ON TELEVISION
Sag
Depth
(%)
Sag Duration (in cycles)
5 10 20 30 40 60
40 N N N N N N
30 N N N N N N
20 N N N N N N
10 N N Y Y Y Y
N: No effect on television due to sag
Y: Television switches off due to sag
TABLE 11: EFFECT OF VOLTAGE SAG ON MICROWAVE
Depth
(%)
Duration (in cycles)
5 10 20 30 40 60
45 N N N N N N
40 N N N N N N
35 N Y Y Y Y Y
15
30 N Y Y Y Y Y
N: No effect on microwave due to sag
Y: Microwave switches off and operation had to be restarted due to sag
TABLE 12: EFFECT OF VOLTAGE SAG ON ASTRO DECODER
Depth
(%)
Duration (in cycles)
5 10 20 30 40 60
30 N N N N N N
20 N N N N N N
10 N N Y Y Y Y
0 N N Y Y Y Y
N: No effect on decoder due to sag
Y: Decoder switches off due to sag
TABLE 13: EFFECT OF VOLTAGE SAG ON MASSAGER
Depth
(%)
Duration (in cycles)
5 10 20 30 40 60
30 N N N N N N
20 N N N N Y Y
10 N N N N Y Y
16
0 N N N N Y Y
N: No effect on massager due to sag
Y: Massager stops operating and operation had to be restarted due to sag
4. Conclusion
Voltage sags are one of the most frequently occurring important power quality problems
in the industry process which can cost billions of production losses annually and the cost
is rising every year. It is important for the utilities and customers to understand the
effects of low power quality. This problem needs to be solved due to the increased use of
power quality-sensitive equipments, the increased use of equipments that generate power
quality problems, the increased interconnectedness of the power system and the
deregulation of the power industry. Recent hike in the electricity tariff increase by the
TNB, Malaysian government makes mandatory reason for the utilities & IPPs to improve
the power quality to residential & industrial customers and also manufacturers to design
equipment with sufficient immunity for power quality disturbances in order to satisfy the
customers and reduce damage [24].
1) From the data provided by TNB, the type of sag that occurs most is single stage dip
due to fault. This type of sag commonly affects residential areas as they are supplied
by single phase supply. As for industrial areas which are supplied by three phase
supply, the impact of sag on three phase motors is less severe if the fault is single
phase to ground fault. Tripping of motor might be avoided but operation of the
process might be affected as motor may decrease in speed and heat up; the life span
of the motor itself may decreases in the long run.
2) The experiment on equipments is divided into three categories; motor loads tested
against SEMI F47 standard, domestic loads tested against ICE 4-11 standard and IT
equipments tested against ITIC and CBEMA standards.
3) The conclusion of voltage sag on lightings and resistive loads by observing all the
waveforms are, during sag period the current is proportional to the sag voltage as the
load is resistive. Once the sag is over, the current returns to its normal value without a
current spike. There is no severe effect of sag on all the resistive equipments tested
but sag might shorten the life span of the equipments on a long haul.
17
4) The conclusion that can be made on non linear and IT equipments by observing the
waveforms are, when sag is applied there is a current surge at the end of sag when
voltage is about to be restored to its nominal value. This high current surge will trip
the protection in the equipment and cause the equipment to switch off, this is shown
through the waveform obtained from the experiment and through physical
observation. Some of the equipments may continue its operation when voltage is
restored and those equipments that had to be restarted will pose a problem for the
user.
5) There are a few factors to be considered to find the most efficient solution to the
voltage sag; the occurrence of sag, the sensitivity of the equipment, the place to install
the protection, the type of protection and cost. Installation of power conditioning
equipment helps reduce or eliminate power quality disturbances.
This project gives a more detail insight of the importance of voltage sag and how it will
affect industrial, office and home appliances. Household appliances do not get damaged
due to voltage sag and this has been observed from experimental results on domestic
appliances. This information is important as the usage of sensitive equipment is
increasing in all the areas and the effect of voltage sag would be a nuisance and unwanted
losses in time and money can be avoided. However, it is recommended to repeat the
performed experiment every few years to keep abreast with the latest technology
especially IT and non linear equipments which are more susceptible to sag.
5 Acknowledgment
The authors gratefully acknowledge the technical support of Faculty Lab Staff.
6 References
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2. C. Radhakrishna, M. Eshwardas, Gokul Chebiyam “Impact of Voltage Sags in Practical Power System Networks”, Transmission and Distribution Conference and Exposition, 2001 IEEE/PES, Volume: 1, pp567-572, 28 Oct – 2 Nov 2001.
3. N.Abu Bakar, A. Mohaned, M. Ismail “A Case Study of Voltage Sag Analysis in a Utility Distribution System”, 2003.
18
4. E.Randolph Collins, Jr, Arshad Mansoor, “Effects of Voltage Sags on AC Motor Drives”, 1997.
5. Richard P. Bingham, “Sags and Swells” February 16, 1998. 6. George G Karady, “Effects of Voltage Sags on Loads in a Distribution System”,
October 2005.7. Math H.J. Bollen, “Understanding Power Quality Problems Voltage sags and
Interruptions”, 2000. 8. IEEE Std. 1159-1995, Recommended Practice on Monitoring Electric Power Quality,
Working Group on Monitoring Electrical Power Quality of SCC22- Power Quality, Draft 6, November, 1994.
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bsp:2:2:3 [2006, June 20]11. http://www.powerstandards.com/IPCSpecs.htm [2006, June 22]12. J.C. Das, “Effects of momentary voltage sags on the operation of induction and
synchronous motors,” IEEE Trans. Ind. Application, v.26, 1990, pp. 711-718. 13. PQWeb 3.1 Report Selection.
http://www.powermonitoring.com/pqwebdemo/query.asp [2006, July 8]14. Mark McGranaghan, Dave Mueller, “Effects Of Voltage Sags In Process Industry
Applications. [Online] 15. http://www.dranetz-bmi.com/pdf/processIndustryApplications.pdf [2006, June 18]16. Toshiba Lamp Catalogue17. http://en.wikipedia.org/wiki/Halogen_lamp#The_halogen_lamp18. Emmanouil Styvaktakis, Math H. J. Bollen and Irene Y. H. Gu, “Expert System for
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23. Voltage-Dip Proofing Inverters & Voltage-Dip Compensators Booklet24. Pacific Gas and Electric Company, “Voltage Sag Ride-through Mitigation in
Sequence by Increasing Cost”, December 1999.25. Daily Express News (2006, May 25). “Power tariff hike in line with overall price
trend” [Online].http://feeds.kualalumpurnews.net/?rid=106c07de33d0249f&cat=48cba686fe041718&f=1 [2006, August 18].
26. Emmanouil Styvaktakis and Math H. J. Bollen, “Signatures of Voltage Dips: Transformer Saturation and Multistage
27. V. Gosbell, S. Perera, V. Smith, Voltage Sag Measurement and Characterization, Power Quality Centre Technical Note No. 4, Power Quality Centre, June 2001, pp. 8.
28. P. Parihar, E. Liu, Identification, Classification and Correlation of Monitored Power Quality Events, IEEE Power Engineering Society 1999 Winter Meeting, Vol. 1: 437-441, 1999
29. Ferrero and S. Salicone, An Easy VI Program to Detect Transient Disturbances in the Supply Voltage, IEEE Transactions on Instrumentation and Measurement, Vol. 54, No. 4: 1471 – 1474, 2005
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30. M. Kubis, C. S .Choo. (No date) .Real-Time Monitoring and Analysis System for Power Quality. [Online]. National Instruments. http://sine.ni.com/csol/cds/item/vw/p/id/134/nid/124400[10 June 2006].
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APPENDIX
Table 8 Summary of the performance of individual loads on voltage sag
Depth
Duration in cycles
10 20 30 40 50 60 Observations
70 No Effects No Effects No Effects No Effects No Effects No Effects
Noticeable decrease in speed in motor accompanied by sound, no effect on VSD, no effect on IT-based equipment, dimness in lighting loads, no effect on electric kettle, oven and rice cooker, blender and fan stops operating and continue when voltage is restored, no effect on non-linear equipment and massager.
60 No EffectsFluorescent lamp switches off
Fluorescent lamp switches off
Fluorescent lamp switches off
Fluorescent lamp switches off
Fluorescent lamp switches off
Noticeable decreased in speed in motor accompanied by sound, no effect on VSD, no effect on IT-based equipment, increase dimness in lighting loads, fluorescent lamp A switches off and recovers after sag, no effect on electric kettle , oven and rice cooker, blender and fan stops operating and continue when voltage is restored, no effect on non-linear equipment and massager.
50Fluorescent lamp switches off
Fluorescent lamp switches off
Fluorescent lamp switches off
Fluorescent lamp switches off
Fluorescent lamp switches off
Fluorescent lamp switches off
Noticeable decreased in speed in motor accompanied by sound, no effect on VSD, no effect on IT-based equipment, increase dimness in lighting loads, fluorescent lamp switches off and recovers after sag, no effect on electric kettle, oven and rice cooker, blender and fan stops operating and continue when voltage is restored, image of TV distorted and recovers after sag, LED light in microwave dimmed, no effects on decoder and massager.
20
40
Fluorescent lamp switches off, computer A restarted
Fluorescent lamp switches off, computer A restarted
Fluorescent lamp switches off, computer A restarted
Fluorescent lamp switches off, computer A restarted
Fluorescent lamp switches off, computer A restarted
Fluorescent lamp switches off, computer A restarted
Noticeable decreased in speed in motor accompanied by sound, no effect on VSD, no effect on IT-based equipment except for computer A restarted, increase dimness in lighting loads, fluorescent lamp A switches off and recovers after sag, no effect on electric kettle, oven and rice cooker, blender and fan stops operating and continue when voltage is restored, increase in severity of distortion of TV image and recovers after sag, LED light in microwave dimmed, no effects on decoder and massager stops operating and recovers after sag.
30
Fluorescent lamps switches off, computer A restarted, microwave and electric kettle switched off
Fluorescent lamps switches off, computer A restarted, microwave and electric kettle switched off
Fluorescent lamps switches off, computer A restarted, microwave and electric kettle switched off
Fluorescent lamps switches off, computer A restarted, microwave and electric kettle switched off
Fluorescent lamps switches off, computer A restarted, microwave and electric kettle switched off
Fluorescent lamps switches off, computer A restarted, microwave and electric kettle switched off
Noticeable decreased in speed in motor accompanied by sound, no effect on VSD, no effect on IT-based equipment except for computer A restarted, increase dimness in lighting loads, fluorescent lamp A and B switches off and recovers after sag, electric kettle switches off and recovers after sag, no effect of sag on oven and rice cooker, blender and fan stops operating and continue when voltage is restored, image of TV distorted and recovers after sag, microwave switches off and operation had to be restarted, no effects on decoder and massager stops operating and recovers after sag.
20
Fluorescent lamp switches off, computer A restarted, microwave and electric kettle switched off
Fluorescent and incandescent lamp switches off, computer A restarted, microwave and electric kettle switched off
Fluorescent and incandescent lamp switches off, computer A restarted, microwave and electric kettle switched off
Fluorescent and incandescent lamp switches off, computer A restarted, microwave and electric kettle switched off
All lighting loads switches off, computer A restarted, microwave, electric kettle and massager switched off
All lighting loads switches off, computer A restarted, microwave, electric kettle and massager switched off
Noticeable decreased in speed in motor accompanied by sound, no effect on VSD, no effect on IT-based equipment except for computer A restarted, all lighting loads switches off and recovers after sag electric kettle and rice cooker switches off and recover after sag, no effect of sag on oven, blender and fan stops operating and continue when voltage is restored, image of TV distorted and recovers after sag, microwave switches off and operation had to be restarted, no effects on decoder and massager switches off and had to be restarted.
10
Fluorescent lamp switches off, all IT-based equipment switches off, microwave, electric kettle and all non-linear equipments switched off
Fluorescent and incandescent lamp switches off, all IT-based equipment switches off, microwave, electric kettle and all non-linear equipments switched off
Fluorescent and incandescent lamp switches off, all IT-based equipment switches off, microwave, electric kettle and all non-linear equipments switched off
Fluorescent and incandescent lamp switches off, all IT-based equipment switches off, microwave, electric kettle and all non-linear equipments switched off
All lighting loads switches off, all IT-based equipment switches off, microwave, electric kettle, all non-linear equipments switched off and massager switched off
All lighting loads switches off, all IT-based equipment switches off, microwave, electric kettle, all non-linear equipments switched off and massager switched off
Noticeable decreased in speed in motor accompanied by sound, no effect on VSD, computers restarted, printers and scanner switches off and operation have to be restarted, hub and LCD monitor switches off and recovers after sag, all lighting loads switches off and recovers after sag electric kettle and rice cooker switches off and recover after sag, no effect of sag on oven, blender and fan stops operating and continue when voltage is restored, TV switches off and recovers after sag, microwave switches off and operation had to be restarted, decoder switches off and recovers after sag and massager switches off and had to be restarted.
21
0
Fluorescent lamp switches off, all IT-based equipment switches off, microwave, electric kettle and all non-linear equipments switched off
Fluorescent and incandescent lamp switches off, all IT-based equipment switches off, microwave, electric kettle and all non-linear equipments switched off
Fluorescent and incandescent lamp switches off, all IT-based equipment switches off, microwave, electric kettle and all non-linear equipments switched off
Fluorescent and incandescent lamp switches off, all IT-based equipment switches off, microwave, electric kettle and all non-linear equipments switched off
All lighting loads switches off, all IT-based equipment switches off, microwave, electric kettle, all non-linear equipments switched off and massager switched off
All lighting loads switches off, all IT-based equipment switches off, microwave, electric kettle, all non-linear equipments switched off and massager switched off
Noticeable decreased in speed in motor accompanied by sound, no effect on VSD, computers restarted, printers and scanner switches off and operation have to be restarted, hub and LCD monitor switches off and recovers after sag, all lighting loads switches off and recovers after sag electric kettle and rice cooker switches off and recover after sag, no effect of sag on oven, blender and fan stops operating and continue when voltage is restored, TV switches off and recovers after sag, microwave switches off and operation had to be restarted, decoder switches off and recovers after sag and massager switches off and had to be restarted.
22