K. Udayakumar

Bio: K. Udayakumar is an academic researcher from College of Engineering, Guindy. The author has contributed to research in topics: Overvoltage & Lightning arrester. The author has an hindex of 2, co-authored 5 publications receiving 37 citations.

Modelling of metal oxide arrester for very fast transients

Abstract: At present metal oxide arresters find limited applications against very fast transient overvoltages (VFTOs). To enable these arresters to function effectively against VFTOs, it becomes necessary to study its design aspects and improve it. With this in view, modelling of arrester under VFTO has been performed. Experimental studies have been conducted to determine the behaviour of one 12 kV arrester assembly under VFTO. It is observed that there is a delay in the initial response of the arrester, which increases with steepness of the current surge because of stray capacitance effect. Based on this study, an innovative arrester model (198 kV) with distributed parameters for VFTO is proposed by incorporating the block and stray capacitance values, which are calculated using finite element method (FEM). The dynamic performance of arrester is successfully obtained using electromagnetic transient program (EMTP) for current surges of different front times. A dynamic hysteresis curve is constructed using proposed arrester model to verify the relative delays between the residual voltage and current surge. A few modifications in the arrester have been suggested to improve the dynamic performance and also for the new testing procedure of arrester under VFTO.

Simulation of faults during impulse tests

Abstract: Experimental results on fault simulations during impulse tests across windings and other specifically designed networks are reported. Both breakdown and partial discharge studies are conducted with digital acquisition of fault records.

Effect of Stray Capacitance on Surge Arrester Performance

Abstract: This paper presents the effect of stray capacitance on voltage distribution. The voltage distribution studies during non-conduction and conduction modes of surge arrester are made. This study analyses effect of stray capacitance on non-uniformity in the voltage distribution and utilization factor. As the voltage distribution during non-conduction mode is important for the insulation design, the capacitance distribution for higher rated arrester is studied. The role of stray capacitance during conduction mode is also analysed by computing the residual voltage of arrester for current surges of different front times. The effect of steepness of current surges on voltage distribution is also discussed. earthed structures, number, size and location of grading rings and a presence of internal corrective grading circuits or elements (3). The arrester acts as capacitance in non-conduction mode. The behaviour of metal oxide surge arrester during non-conduction mode is only based on voltage distribution. But during conduction mode, in addition to voltage distribution, computation of initial rise time of the residual voltage is also important for transient study (4).

Study of overvoltage protection of a microwave repeater station

Abstract: Ever since inception, the electric power and communication systems are exposed to dangerous overvoltage surges starting from lightning to service frequency temporary overvoltage waves with disastrous consequences. The operation of electronic devices in this environment had led to a situation wherein they are severely affected. All sorts of electronic equipment are at risk: this calls for an effective protection against transient overvoltages. It includes adequate equipment protection, inherent capability of the equipment to withstand overvolage surges, good installation and a sound earthing arrangement. This paper describes an incident involving the exposure of wireless equipment and the operating personnel to frequent lightning activities in a hilly place and the need of a good installation practice, better earthing and adequate protection against direct lightning strokes.

Study of overvoltage protection of a microwave repeater station

Abstract: Ever since inception, the electric power and communication systems are exposed to dangerous overvoltage surges starting from lightning to service frequency temporary overvoltage waves with disastrous consequences The operation of electronic devices in this environment had led to a situation wherein they are severely affected All sorts of electronic equipment are at risk: this calls for an effective protection against transient overvoltages It includes adequate equipment protection, inherent capability of the equipment to withstand overvoltage surges, good installation and a sound earthing arrangement This paper describes an incident involving the exposure of wireless equipment and the operating personnel to frequent lightning activities in a hilly place and the need of a good installation practice, bette r earthing and adequate protection against direct lightning strokes

Virtual Instrument for Lightning Impulse Tests

Abstract: We propose an objective formulation of the impulse analysis problem from a signal analysis viewpoint. The winding response is quintessentially that of a deterministic network to a finite energy signal, with breakdown and partial discharge being inherently nonlinear events. A significant improvement to the acquisition of waveforms is demonstrated by a virtual instrument approach. It retains the advantages of the time- and frequency-domain methods. The drawbacks of the transfer function method are highlighted and a new piecewise linear approach is proposed for analysis. Experiments on a discrete lumped parameter model of the winding are used to validate the PXI based instrument.

Lightning Performance of Distribution Transformer Feeding GSM Base Station

Abstract: 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.

Behavior Comparison of Metal Oxide Arrester Blocks When Excited by VFTO and Lightning

Abstract: With the development of the ultrahigh voltage (UHV) and extra high voltage (EHV) electric power industry in China, gas insulated substation (GIS) is applied widely. Very fast transient overvoltage (VFTO) caused by disconnector operations in GIS may damage the insulation of equipment due to its high frequency and amplitude. As one of the main overvoltage protection equipments, the protection behavior of surge arresters has received extensive attention. In this paper, the residual voltage behavior, the impedance behavior, and the response behavior of five different representative arrester blocks when excited by VFTO and lightning are investigated, respectively. Experimental results present that when the current peak keeps constant, the residual voltage under VFTO is approximately 14.7%–18.2% higher than under the standard lightning impulse voltage (8/20 μs, LI). The arrester block presents different impedance behavior under VFTO and LI. It behaves dominantly inductively under LI and expresses an impedance converting behavior under VFTO. Furthermore, the diameter and the shape of arrester blocks have little impact on the ratio of $V_{0}$ to $V_{{\rm 1mA}}$ under VFTO. Therefore, the protective effect of arresters varies slightly under VFTO and LI. Investigating behavior of arrester blocks under VFTO in comparison with under LI could be applied not only in VFTO simulation and insulation coordination but also in the design and the operating of metal oxide surge arrester in GIS.

Determination of surge arrester discharge energy using finite element analysis method

Abstract: Surge arrester is widely used as a protective device to reduce possibility of flashover during transient overvoltage event. The device needs to withstand high energy discharged by the overvoltage which may increase the degradation rate of its characteristics. In this study, a set of transmission line surge arresters with different dimensions and ratings was simulated to investigate their discharge energy capabilities during fast-front surge events using the finite element analysis method. To validate the accuracy of the method, the arrester models were also simulated by the use of PSCAD/EMTDC and EMTP-RV software and compared with the specifications provided by the manufacturer. In spite of distinctive representations of the arrester models in COMSOL Multiphysics, EMTP-RV and PSCAD, the comparison made between the simulation results indicates a satisfactory agreement. The manufacturers’ data were used to validate that the proposed simulation model is acceptable. It was found that the simulation results were comparable with the manufacturer's test data of the discharge voltages and energy withstand capability, thus proving that all studied cases were adequately modelled. Parametric analyses were also conducted using finite element method to study the effects of varying the design geometry of the ZnO blocks and the arrester's housing on the energy absorption, which cannot be evaluated using PSCAD and EMTP-RV software.

Response of metal oxide arrester in gas-insulated substation and methods to improve its dynamic characteristics

Abstract: It is well known that the metal oxide arrester (MOA) has the inability to operate against very fast transient overvoltage (VFTO). The aim of this paper is to study the dynamic performance of MOA in gas-insulated substation (GIS). A 230 kV GIS is taken from a local utility and the system is modelled for very fast transients. The dynamic performance of arrester is analysed for current surges of different front times, varying from microsecond to nanosecond using electromagnetic transient program. The dynamic characteristics can be obtained for front time, more than 1 µs. However, there is a deviation in it when front time is less than 1 µs, showing failure of arrester conduction because of delay in its initial response, especially under VFTO. The dynamic characteristic is improved by making modifications in the system as well as in the arrester. A dynamic hysteresis curve is constructed to confirm the delay between the residual voltage and current surge. By decreasing the delay, it is possible to improve the dynamic characteristics of the arrester so that the effective utilisation of MOA can be enhanced in VFTO applications.