• Transactions on Electrical and Electronic Materials
• /
• v.16 no.6
• /
• pp.317-322
• /
• 2015

The metal oxide varistor (MOV) is a major component of the surge protection devices (SPDs) currently in use. The device is judged to be faulty when fatigue caused by the continuous inflow of lightning accumulates and reaches the damage limit. In many cases, induced lightning resulting from lightning strikes flows in to the device several times per second in succession. Therefore, the frequency or the rate at which the SPD is actually exposed to stress, called a surge, is outside the range of human perception. For this reason, the protective device should be replaced if it actually approaches the end of its life even though it is not faulty at present, currently no basis exists for making the judgment of remaining lifetime. Up to now, the life of an MOV has been predicted solely based on the number of inflow surges, irrespective of the magnitude of the surge current or the amount of energy that has flowed through the device. In this study, nonlinear data that shows the damage to an MOV depending on the count of surge and the amount of input current were collected through a high-voltage test. Then, a failure prediction algorithm was proposed by preparing a look-up table using the results of the test. The proposed method was experimentally verified using an impulse surge generator

• Proceedings of the KIEE Conference
• /
• 2003.10a
• /
• pp.186-188
• /
• 2003

The ZnO surge arrester is the protective device for limiting surge voltages on equipment by diverting surge current and returning the device to its original status. The occurrence of overvoltage appears in any phase to AC power supply system and it appears in mixing AC and impulse voltages, moreover because HVDC power supply system uses converter in semiconductor, it makes mixed DC and high harmonics voltages. In this study, the various mixed AC and DC voltages was made for investigating the degradation effect of ZnO arrester according to mixed voltage. As a result, the increase of DC component to mixed voltages causes the increase of resistive component of total leakage current to ZnO block. In changing V-I curve for mixed voltages, the cross-over point acts a factor as making the proper capacitor size of an equivalent circuit for ZnO block.

• Proceedings of the KIEE Conference
• /
• 2009.07a
• /
• pp.2065_2066
• /
• 2009

In this paper, we have developed high performance SPD(surge protective device) and evaluated the characteristics in comparison with typical SPD used in the inside and outside of the country. The new SPD was composed of MOV(metal oxide varistor), GDT(gas discharge tube) and impedance such as resistors, capacitors or varistors. To estimate operating the characteristic of the SPD which was developed, it was measured surge voltage caused by fault current or surge according to IEC 61000-4-5. As a result it was found that the power supply was cut off by high performance SPD when caused a short-circuit. In addition we could know that it could prevent ELB(earth leakage breaker)'s malfunction caused by surge.

• Proceedings of the KIEE Conference
• /
• 1998.07e
• /
• pp.1675-1677
• /
• 1998

It is currently increasing to use surge protection devices in the protection of various electronic circuits from the transient overvoltages such as lightning strikes and switching surges. For this reason, the simulation methods, which can easily predict the protection performance of the devices, are strongly required in order to design the adequate surge protection circuits in lightning surge cut-off performance and economic aspects. This paper deals with ZnO varistor modeling method for designing a surge protection circuit and suggests the Pspice simulation model which takes the characteristic of varying clamping voltage into consideration during the time-to-crest, in range of $8{\sim}30{\mu}s$, of surge current applied to a ZnO varistor. The ZnO varistor Pspice simulation data introduced in this paper has produced almost same values as the measured results experimentally.

• Journal of the Korean Society of Safety
• /
• v.28 no.5
• /
• pp.15-20
• /
• 2013

This paper dealt with melting characteristics of low-voltage miniature cartridge fuse used for 220 V electronic equipment. The experimental sample is low-voltage miniature cartridge fuse with rating of 250 V(3A) and size of $5{\times}20$ mm. In order to evaluate melting and scattering characteristics of the fuse, we applied to 8/20 ${\mu}s$ surge current, overload current and external thermal stress such as flame of fire. From the experimental results, the fuse element was melted and scattered by applied surge current(above 0.79 kA) and overload current(above 4.5 A). It was also attached to the inner surface of the fuse tube. The fuse element was attached as a thin film on inner surface of fuse tube when large surge current was applied. It was confirmed, however, the fuse element was not changed by external thermal stress such as flame and hot-air.

• Journal of the Korean Society for Railway
• /
• v.10 no.2 s.39
• /
• pp.112-116
• /
• 2007

In this paper, we proposed a selection and application recommendations of ZnO arresters for DC electric traction vehicles. To decide the Continuous Operating Voltage($U_C$), the Rated Voltage($U_r$), and the Nominal Discharge Current(In), we measured and analyzed system voltages and surge currents flowing the arrester installed on a DC electric traction vehicle under running state. System voltages measured up to 1,800 V in 1,500 V-system, and surge currents were recorded up to 3 times per a running-service-route and their magnitudes were ranges of $150A{\sim}2kA$. From these results and a standard EN50163, we could proposed $U_C$, $U_r$, and In available for the 1,500 VDC electric traction vehicles.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2002.07b
• /
• pp.890-893
• /
• 2002

Since 1970s, varistors using metal-oxide resistors have been applied to Gapless surge arresters for power system. In the paper, the structure of metal-oxide surge arresters without gaps for 362kV GIS which is developed the first in korea has been introduced. And the main evaluation items for the metal-oxide resistors which are reference voltage test, residual voltage test, long duration current impulse withstand test and operating duty test is tested and evaluated.

• Proceedings of the KIEE Conference
• /
• 1996.07c
• /
• pp.1876-1878
• /
• 1996

This paper describes the combination surge generator for applying performance tests of surge protective devices. The $8/20{\mu}s$ waveform applies to low impedance circuits and components and is commonly used to determine the characteristics of surge protective devices. And the $1.2/50{\mu}s$ waveform applies to high impedance circuits and components and is used for testing dielectric behavior. Therefore, the combination surge generator, which generates $1.2/50{\mu}s$ voltage waveform under open-circuit conditions and $8/20{\mu}s$ current waveform under short-circuit condition, was proposed. Also this generator can produce $10/1000{\mu}s$ as well as $0.5{\mu}s/100kHz$ ring waveform.

• The Transactions of the Korean Institute of Electrical Engineers P
• /
• v.58 no.3
• /
• pp.328-333
• /
• 2009

In this paper, we have developed high performance SPD(surge protective device) and evaluated the characteristics in comparison with typical SPD used in the inside and outside of the country. The new SPD was composed of MOV(metal oxide varistor), GDT(gas discharge tube) and impedance such as resistors, capacitors or varistors. To estimate operating the characteristic of the SPD which was developed, it was measured surge voltage caused by fault current or surge according to IEC 61000-4-5. As a result it was found that the power supply was cut off by high performance SPD when caused a short-circuit. In addition we could know that it could prevent ELB(earth leakage breaker)'s malfunction caused by surge.

• Proceedings of the KIEE Conference
• /
• 2003.11b
• /
• pp.87-90
• /
• 2003

There are generally two temperature control methods using ac voltage regulators - the phase control method and the on-off control method. The phase control method uses thyristor's angles of extinction for the output power regulation and the on-off control method uses the control of on and off times for the output power regulation. Both of methods have the problems that are the unbalance of the three phase and surge current caused system's destruction. The main object of this study proposes a solution of problems of surge currents and unbalance of three phase when thyristor voltage regulator is switching. To solve the problem, It is proposes that the solution of surge currents is using a tap transformer and an additional switch with adjustable resistance and applies zero crossing of switching voltage of two input line to power load. This method is discuss and verified by computer simulations and experiments.