• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2009.10a
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• pp.339-341
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• 2009

Surge Protective Device(SPD) is installed by increasing information and communication equipments and home network equipments by individual home, and the amount of SPD used is increasing by revision industry regulations and strengthening equipotential grounding system. Parts of SPD installed in residential distribution board has ZnO varistor, voltage constraint type devices, but it is exposed to Temporary Overvoltage Characteristic. This thesis analyzes products through Thermal Stability test for SPD for general house and suggests the better method. As results of analysis, Gas Discharge Tube(GDT) to cut off from a leakage current and more than two kinds of safety devices to protect Thermal Runaway were needed.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.1
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• pp.71-77
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• 2010

Protection against lightning surge is an essential part of almost any electrical and electronic equipment today. Metal Oxide Varistor(MOV) is the single most important component in the overwhelming majority of the Surge Protective Devices(SPD) designated to provide such protection. In this paperr various types of MOV based SPD are inspected and experiments are carried out on the side effects of the low Measured Limiting Voltage(MLV) characteristics. Experiment results show that a lower MLV could cause a higher Temporary Overvoltage(TOV)-induced SPD failure rate in the field, and SPD are more likely to be victims rather than protectors in a TOV scenario. This means that from a safety perspective, the SPD should be specified with higher TOV withstand capability(UT) and faster SPD disconnector.

• Journal of Electrical Engineering and Technology
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• v.10 no.3
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• pp.1293-1297
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• 2015

This paper introduces the insulation coordination study results for UHV AC systems which was performed by CIGRE working group. The study results will be discussed within IEC technical committee in order to amend the IEC Insulation Coordination 60071-1 Ed. 8 2010 and 60071-2 Ed. 3, 1996. This paper includes the insulation coordination of transformer, gas insulated switchgear, metal oxide arresters and clearances of transmission towers. This article also illustrates the overvoltage specific to UHV systems such as TOV(temporary overvoltage), switching overvoltage, lightning overvoltage and VFTO(very fast transient overvoltage).

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2009.05a
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• pp.344-347
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• 2009

Surge protective devices (SPD) have a special position because of the expectation that they perform an effective protective function against various kinds of surges. However, there exists a misconception that the SPD satisfying lower measured limiting voltage (MLV) should also protect equipment against temporary overvoltages (TOVs) as well. This paper inspects various types of MOV based SPDs and carry out experiments on the side effects of the low MLV characteristics. The experiment results show that a low MLV could cause a higher TOV-induced SPD failure rate in the field.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.541-542
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• 2007

The paper also introduces a new Distribution Class ground lead disconnector design that not only extends the claimable detonation range well below the 20 amps specified in industry standards, but is very durable when exposed to severe arrester durability tests. Finally. this paper shows how this next generation disconnector interacts with the connected arrester to improve the overvoltage withstand capability of the arrester assembly. The interaction of the disconnector grading capacitor with the series-connected arrester metal oxide disc elements actually improves the arrester assembly temporary overvoltage withstand capability, making the design less vulnerable to TOV failures. Since the vast majority of distribution class arresters are sold domestically with ground lead disconnectors, this design improvement in the disconnector to improve detonation reliability also translates into a significantly improved distribution class arrester design.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.2
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• pp.120-125
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• 2011

SPDs are increasingly being used against lightning and switching surge according to the applicable revised standard and equipotential grounding system. SPDs are equipped usually with a MOV voltage regulating element. The MOV, however, always is exposed to the danger of thermal runaway resulting from inrushing temporary overvoltage and deterioration. In this paper, the authors made two prototype SPDs built-in Instantaneous trip device and analyzed their limiting voltage through test of the MOV breakdown. As the result of the analysis, the SPDs built-in Instantaneous trip device was proven to be effective for protecting MOV against thermal runaway and Instantaneous trip device react for limiting voltage is considered that is applicable to SPD.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.890-893
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• 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 Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.05b
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• pp.216-221
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• 2000

This paper describes the analysis results on the PT ferroresonance at 154 kV GIS (gas Insulated substation by EMTP(Electro- magnetic Transient Program). We had simulated the PT ferroresonance between a potential transformer(PT) and an open circuit breaker's grading capacitance. The ferroresonance leads to very large power frequency overvoltages on PT bus and subsequent insulation failure. The large power can be supplied to the PT by the high voltage on the opened circuit due to the grading capacitance and equivalent capacitance of the buses during the ferroresonance. The damping circuit connected on the secondary winding were considered in the model. The actual countermeasure include a saturable inductor and a resistor series-mounted, but the 2 ohms of damping resistance was used in the computationl model.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.140-143
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• 2000

The primary function of ZnO lightning arrester is to protect transmission and distribution equipment from overvoltages and to absorb electrical energy resulting from lightning or switching surges and form temporary overvoltage. However, ZnO lightning arrester are known to exhibit an increases in resistive current with time, the rate of increase being exacerbated with increasing applied voltage and ambient temperature. So, it is important to the leakage current measurement of ZnO lightning arrester. In addition, since the resistive leakage current caused by deterioration of ZnO lightning arrester mainly caused an increase of the third harmonic component, thereby it is possible the arrester degradation diagnosis by measuring the third harmonic component in the total leakage current. The leakage current and third harmonic component are measured and used to investigate the degradation diagnosis of ZnO element of arrester. Also the SEM photography is used to investigate the change of crystal structure of ZnO element with degradation.

• Proceedings of the KIEE Conference
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• 2002.07a
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• pp.262-264
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• 2002

This paper shows the design standard of KEPCO on the contamination design for 345 kV and 154 kV transmission tower. Up to now, because the design standard of KEPCO on the insulation design contains 154 kV transmission system only, we had investigated the 343 kV system for the revision of design standard, with respect to the contamination design, we have used the same design philosophy which were adopted to the 765 kV transmission tower. In order to determine the number of insulator discs, we had investigated the withstand voltage of discs according to the level of ESDD(Equivalent Salt Deposit Density) and kinds of disc types. The TOV(Power Frequency Temporary Overvoltage) were estimated by EMTP(Electromagnetic Transient Program) for both 154 kV and 345 kV transmission system. The overvoltage level was appeared 1.35 p.u. between phase to ground for both 154 kV and 345 kV transmission system, but finally this factor was not applied to the design standard considering current design standard and economic point of view. With regard to classification of contamination area of 345 kV transmission system, we added the clean area which was not specified in the current design practise.