A device for attaching to an electric power line conductor includes an electrically conductive housing with an opening for accepting the power line conductor and configured to be grounded to the power line conductor. At least one magnetic core is configured to surround the power line conductor and power a power supply electronics module. An ambient temperature measuring assembly is mounted inside and near the bottom of the electrically conductive housing. The ambient temperature measuring assembly is thermally insulated from the housing for thermally separating the ambient temperature measuring assembly from the housing.

Portable self powered line mountable device for measuring and transmitting ambient temperature

The unprecedented proliferation of electronic devices in critical applications, such as smart grid and communication systems, has brought new challenges in system reliability. Electronic circuits and components are especially sensitive to transient overvoltages and lightning surges, and design must consider operation under these worst case situations. To address these transients, Metal Oxide Varistors (MOVs) are widely used in electronic circuits and power supplies. They absorb surges in the circuit input and maintain the voltage within acceptable limits. However, these surges and overvoltage transients can degrade MOVs over time. Reliability of an MOV depends on maintaining its Energy Absorption Capability (EAC) in an acceptable range. In this paper, for the first time, the effect of degradation is investigated on Energy Absorption Capability (EAC) of low voltage MOVs by experimental test in a UL-certified lab. The results show that EAC is decreasing with degradation due to surges. Furthermore, it is shown that Time-to-Failure (TtF) of the degraded MOVs is longer than that of new MOVs in some transient overvoltage (TOV) incidents. This helps explain the actual mechanism of MOV failures in real life applications and questions whether the widely accepted design guideline that a 10% change in varistor voltage at 1 mA is a degradation indicator. Finally, a nonlinear resistive - capacitor model is proposed for degraded MOVs.

Degradation of low voltage metal oxide varistors in power supplies

This letter provides evidence of a peculiar behavior of metal-oxide varistors under DC overvoltages. It stresses the need for extending the V–I characteristic of varistors in the time domain so as to accurately predict the dynamic performance of varistor-based surge protective devices under temporary overvoltages. Observations and mathematical formulation of DC overload behavior of metal-oxide varistors may have significant implications in energy absorption requirements for low-voltage surge protective devices and unlocks possible monitoring strategies in emerging DC distribution smart grids.

DC Overload Behavior of Low-Voltage Varistor-Based Surge Protective Devices

https://onlinelibrary.wiley.com/doi/pdf/10.1002/tee.22649

Lightning striking characteristics to tall structures

Alleviation of the transients induced in large photovoltaic power plants by direct lightning stroke

The invention relates to a single- or multi-pole switching device, in particular for DC applications, having at least one rotating switching element (2) which is connected to a drive, and also comprising switching contacts (4, 5), connection pieces (7) and connection poles or connection terminals (8) and a housing arrangement which accommodates the abovementioned parts. According to the invention, a movably guided rotary cylinder (2) is formed in the housing arrangement, said rotary cylinder being located in a body which is designed as a rotary cylinder holder (1). The rotary cylinder (2) has at least one contact pin (3) which passes radially or tangentially or eccentrically through the rotary cylinder and has, at its end, a contact piece (4) in each case. Mating contact pieces (5) are arranged in the rotary cylinder holder (1), said mating contact pieces being electrically connected to the connection pieces (7) or connection poles or connection terminals (8). A narrow, arc-influencing gap is present between the rotary cylinder (2) and the rotary cylinder holder (1), wherein, as a result of the movement of the rotary cylinder (2), the electrical connection between the contact pieces (4) and the mating contact pieces (5) can be broken by way of the contact pin (3) and the resulting disconnection arcs (11) enter the air gap subject to an extension and are rapidly extinguished there.

Single- or multi-pole switching device, in particular for dc applications

The increased use of renewable energy sources and connection of energy storage systems to energy distribution networks of the future on the basis of DC voltage demands new power electronic modules with a higher degree of efficiency, reliability and with materials saving. In this article, the overvoltage protection concept on the basis of metal oxide varistors (MOV) for such network components as pulse-width modulation (PWM) modules and DC-to-DC converters as well as a new patented, innovative power-electronic topology concept [1, 2], which allows the regenerative energy sources connect direct to the medium-voltage distribution system is introduced. The distorted voltages from converters and from other power electronic network components are characterized by high-frequency pulsating voltages which generate leakage currents because of MOV capacitance. This leakage current in its turn can overheat the MOV and accelerate its thermal ageing. The main focus of this work is to study the distorted voltages in already mentioned network concepts and its influence on installed MOV and vice versa. The concept of overvoltage protection for some network components is presented. Additionally, an effort to combine the overvoltage protection system with some other useful functions for converter, such as definition of reference potential of the internal ground, was fulfilled.

Applying of surge arresters in power electronic network components

Wind turbines are very exposed structures to lightning due to their height and installation in unshielded areas and are therefore expected to influence the local lightning activity. However, it is unknown in what quality and quantity lightning is influenced. The following paper presents a study conducted at wind farms in Germany showing to what extent lightning activity is influenced by wind turbines. Conducting the analysis all lightning strokes of more than 50 wind farms over the period of 10 years were analyzed before and after the construction of the considered wind farms using the lightning detection system BLIDS [1]. Thereby both onshore and offshore wind farms are investigated. Examining lightning density, amplitudes and probability distributions of the considered wind farms a significant increase in lightning frequency was observed inside the impact area of the wind turbines both for onshore and offshore wind farms. With regard to amplitudes of negative lightning strokes no specific conclusion could be drawn for onshore wind turbines while amplitudes at offshore wind farm increased extremely. The data obtained during current initial investigation can be used for further study to estimate the average number of lightning flashes to a single or a group of wind turbines. That can help to design a sufficient lightning and overvoltage protection system for wind turbines. However, one should take into account that detection efficiency (DE) of lightning detection systems for ground-to-cloud flashes (upward lightning) in special cases is reduced compared to cloud-to-ground flashes (downward lightning). In [2] a DE of 43 % is reported and explained by the fact that the ground-to-cloud lightning currents often are an initial continuous current only (ICCOnly), free from any superimposed impulse currents and therefore cannot be detected by lightning detection system at all. However, this type of flashes could pose a risk to wind turbines because of their enormous high transfered charge values which can easily exceed 300 As. This specific type of ground-to-cloud flashes cannot be considered in this study because of reason mentioned above.

Initial investigation of influence of wind farms to lightning events

The impact of space point definition on dynamic electro-geometrical model of lightning strike probability

This paper validates the performance of low-cost lightning protection systems for small structures proposed by researchers in the past. Such structures have an acute demand in the countries with very high lightning ground flash density, yet the affordability of the mass public is quite limited due to the struggling economies of the countries. The protection systems for small housing structure, and a standalone protection structure for one or few people have been investigated by implementing the structures in HFSS/ANSYS software which employs finite element method. By applying current waveforms to represent first negative return stroke, subsequent negative return stroke and positive return stroke, the electric field and potential gradient of the entire space and the current density and the thermal profile of the protective structure have been computed. The objectives were to find whether the voltage distribution in the wake of a lightning strike could initiate side flashes, generate touch potential and step potentials that exceed dangerous levels, drive current densities due to which the structure collapse under thermal effects. It has been found that the proposed protective structures could suppress side flashes and harmful effects due to step potential while the structure will be able to withstand the heat generated. However, the touch potential could still be beyond the human injury thresholds, thus a minimum separation from the lightning current passage should be advised to the occupants.

/pdf/evaluation-of-lightning-protection-systems-proposed-for-g8siwvavi7.pdf

Michael Rock

Papers

Single- or multi-pole switching device, in particular for dc applications

Applying of surge arresters in power electronic network components

Initial investigation of influence of wind farms to lightning events

The impact of space point definition on dynamic electro-geometrical model of lightning strike probability

Evaluation of lightning protection systems proposed for small structures by electromagnetic simulation