Installation Of Surge Protective Devices Research Articles

Lightning Surge Overvoltage Protection for Low-Voltage Equipment Placed Outdoors in TT System

When a TT system is used for earthing a low-voltage distribution line, the conductive enclosure of the equipment is grounded separately from the system ground for the power line. In such a case, lightning protection depends on the installation of surge protective devices (SPD) on the equipment side. However, in newer systems, a protective earth (PE) line is wired from the power substation for stable operation and connected to the PE line in the outdoor equipment. In this case, the SPD of the distribution board can suppress the overvoltage on the equipment side. In this article, the overvoltage generated between the power and grounded PE lines of the equipment using a vinyl-insulated vinyl-sheathed flat-type cable for a low-voltage distribution line was examined using transient circuit analysis. Then, we demonstrated countermeasures to achieve electric shock and lightning overvoltage protection.

Lightning Performance of Distribution Transformer Feeding GSM Base Station

Data on unscheduled electric service interruptions in an extended distribution network (20/0.4 kV) were analyzed in order to examine the causes contributing to distribution substation failures. A distribution substation feeding a Global System for Mobile Communications base station experienced the highest service interruption rate due to transformer sustained failures, the vast majority of which were categorized as lightning related. Thus, with the aid of detailed Alternate Transients Program-Electromagnetic Transients Program simulations, an investigation on the overvoltages surges impinging on the distribution transformer due to direct lightning strokes to the connected MV overhead line and to the nearby telecommunication tower has been made. Transformer failures are caused solely by fast-front overvoltages exceeding the basic insulation level of the LV side of the transformer. This is substantiated by the good agreement between estimated and reported transformer failure rates. The safe operation of the distribution transformer necessitates the installation of surge protective devices at its low-voltage terminals, also overcoming the need for extremely low values of telecommunication tower grounding resistance. Additional line surge arresters should be installed at the penultimate wood pole of the connected overhead line which, besides improving the lightning performance of the transformer, significantly increases the reliability of the distribution substation.

보호거리와 부하 유형에 따른 SPD의 보호효과에 대한 실험적 고찰

Surge protective devices(SPDs) are widely used as a most effective means protecting the electrical and electronic equipment against overvoltages such as lightning and switching surges. When installing SPDs, it is essential that the voltage protection level provided by SPDs should be lower than the withstand voltage of the equipment being protected. But even the proper selection of SPDs are achieved, the voltage at the equipment terminal may be higher than the residual voltage of SPD due to the reflection and oscillation phenomena. This paper was focused on the investigations of the conditions for which the equipment is protected by an SPD taking into account the influences of the protective distance and type of load. The protective effects of SPD with voltage-limiting component were analyzed as functions of types of load and protective distance between the SPD and load. As a result, in the cases of long protective distances, capacitive loads and loads with high resistance, the voltage at the load terminal was significantly higher than the residual voltage of SPD. It was found that the proper installation of SPDs should be carried out by taking into account the protective distance and type of load to achieve reliable protection of electronic equipments against surges.

Effective Protection Distances of SPDs for Household Electrical Appliances

The installation of surge protective devices (SPDs) is important for the protection of today's household appliances against in-rushing surge. The effective protection distance should be taken into account for the installation to avoid the influence of oscillation phenomenon. For household appliances, their port impedance characteristics are more complex and frequency dependent, and for some appliances, the impedance characteristics are different in operating state and nonoperating state. With the method proposed in this paper, operating state impedance characteristics of 16 different kinds of appliances are measured and the equivalent circuits are obtained by vector fitting and circuit synthesis. The protection effect of SPDs is simulated by electromagnetic transient analysis software using a practical distribution system model, and the effective protection distances of SPDs with different protection level for these appliances are obtained. Several analyses are made about relationships between the protection distance and factors such as the type of appliance, operating condition, and protection level. A case of protection for multiappliance is also analyzed.

A study of modeling of EMTP analysis for indoor distribution line

AbstractDamage to home electric appliances due to lightning surges has recently become more common. The installation of SPDs (surge protective devices) in interior wiring is a countermeasure against damage and is also becoming more widespread after amendment of the regulation on indoor wires in 2005. Past study showed an effective method in which the earth line of the SPD is connected with that of home appliances and is grounded at one place in the home. However, because the methods of installing the distribution line in homes vary, it is difficult to estimate the effect of SPDs in every home, and high‐precision analysis by EMTP for interior wiring and SPD in the home is required. In this study, experiments were conducted with interior wiring and varistors, which constitute SPDs, and this paper reports the results of those experiments and of EMTP analytical models. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 175(4): 24–33, 2011; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21062

Influence of line routing and terminations on transient overvoltages in LV power installations

AbstractIEC 62305‐4 gives the rules for the selection and the installation of surge protective devices (SPDs), where the maximum enhancement factor is considered to be equal to 2 in the worst case of open‐circuit condition. The objective of the present paper is to check this relation for equipment connected to low‐voltage (LV) power system. The LV power system is considered as TN‐S system with different routings in three‐ and six‐storey buildings. The terminals of apparatus are substituted by a variety of different loads, namely, resistances, inductances, and capacitances. All Maxwell's equations are solved by the method of moments (MoM) and the voltage is calculated at the apparatus terminals. The SPD itself is simulated by a voltage source at the ground floor. The results reveal that the voltage at the apparatus terminals may overshoot the SPD protection level by a factor of 3 irrespective of the number of floors and loops. Copyright © 2008 John Wiley & Sons, Ltd.

An Experimental Study of the Effect of SPDs on Protection for Home Electric Appliances against Lightning Surges through a Distribution Line

Damages of home electric appliances from lightning surges through a distribution line have recently increased. Installation of SPDs (Surge Protective Devices) in indoor distribution line is one of countermeasures against the damages. However, installation of SPDs is not prevalent because the effect of it is uncertain and it is expensive.Therefore, to ascertain effects of the SPD, they were verified by means of experiments in various cases. As a result, an SPD in the switchboard wholly suppressed over-voltages in the indoor distribution line and an SPD installed near a home electric appliance did over-voltages in one indoor distribution branch line near the SPD. But the SPD for the appliance did not suppress over-voltages in the other indoor distribution branch lines. Installation of an SPD in the switchboard is one of effective methods to protect home electric appliances against lightning surges through a distribution line.