Protectionism on the Surge

With the textile export to EU growing at a pace faster than anticipated, the joint efforts to slow down Chinese shipment to this market in a predetermined arrangement known as "bilateral check" seem to be abortive, more and more producers there seem to grow out of their patience with EU’s past deal with China. A new wave of trade protectionism is coming on the surge…

An Active Triggered Surge Protective Gap

A triggered surge protective device is designed and its discharge characteristics axe studied. The experimental results show that the triggered surge protective device has excellent surge protective characteristics. When the gap distance is 5 mm, p. d is 90 Pa.mm and without an active energy trigger circuit, the DC breakdown voltage of the triggered surge protective device is 2.32 kV and the pulse breakdown voltage is 5.75 kV. Therefore, the pulse voltage ratio, which is defined as the specific value of pulse breakdown voltage and DC breakdown voltage, is 2.48. With a semiconductor ZnO flashover trigger device and an active energy coupling trigger circuit, the pulse breakdown voltage can be reduced to 3.32 kV, the pulse voltage ratio is 1.43 and the response time is less than 100 ns. These results are helpful in laying a theoretical foundation for further studies on triggered surge protective devices.

Study of Discharging Characteristics of Hollow Cathode Surge Protective Gap

A hollow cathode surge protective gap （HCSPG） was designed, and the discharge characteristics was investigated in an air and nitrogen gas environment. For both the gap spacing D and the hole diameter Ф of HCSPG of 3 mm, the voltage protective value Up of HCSPG is about 3.5 kV and its converting time tc exceeds 100 ns at an air pressure from 10 Pa to 100 Pa. The maximum converting time tc from glow to arc discharging reaches 1600 ns at an air pressure of 100 Pa, while the minimum converting time tc is 120 ns at 10 Pa. For a triggered HCSPG, Up is reduced to about 1.6 kV while the converting time is 120 ns with a semiconductor trigger device and 50 ns with a dielectric porcelain trigger device under an air pressure of 100 Pa.

DESIGNING A “MODULAR FORTRESS” HOME ON LONG ISLAND SOUND

The challenges of building on an island demanded elements of green building technology.Since there are no utilities for life support systems such as heat,hot water,and electricity,the design approach needed to be comprehensive and efficient.We were commissioned in 2004 to design a 4,200-square-foot vacation house on a small island off Branford Connecticut.This island,less than one acre,is only 10 feet above sea level at the maximum high point.The challenges were not only to produce enough energy as efficiently as possible,but to build a structure resistant to storm surges potentially 11 feet above sea level and 3 foot waves that could inundate the island.The home has seen three severe storms since it was constructed,and indeed,the ocean did completely inundate the island,leaving only the home and the mechanical building to stand alone in the open and violent ocean.The island prior to 1938 had a luxurious mansion built on it constructed of masonry and by conventional means.The 1938 hurricane swept over Long Island Sound in that year making a direct hit to the island.The mansion was leveled,leaving only debris,and for 67 years there was no meaningful building on the island other than a storage shack and lean-to over the remains of the foundation.The only life support brought to the island was a water pipe.The island,named Sumac Island,is only a half mile off the southern Connecticut shoreline in Branford,just a few miles west of a chain of islands called the Thimbles Islands.The owner bought this island in part for the spectacular views-and of course the privacy any island gives-but he knew it presented many challenges,mainly generating its own power.This required sophisticated mechanical systems to be built-off the grid(see Figure 1).

A Novel Crowbar Impulse Current Circuit for Testing the Switch-Type SPD

A crowbar impulse current circuit for testing the switch-type surge protective device （SPD） is presented. The crowbar circuit consists of a computer control circuit, a trigger voltage pulse generator, a main discharging switch, and a crowbar pseudospark switch. The active trigger technology was studied in the crowbar impulse current circuit. The circuit monitors the main discharging current and generates a trigger signal at a proper time for the crowbar pseudospark switch operation. The trigger characteristics of the main discharge switch and the crowbar pseu- dospark switch were investigated. By monitoring the preset applied capacitor voltage, the gap distance of the main discharging switch could be adjusted to ensure a discharging delay time less than 2 μs. Equipped with a surface ttashover trigger device made of high relative perimittivity dielectric material BaTiO3 （εr = 3460）, the discharge delay time of the crowbar pseudospark switch is less than 85 ns, and the minimum operating voltage is less than 1% of its self-breakdown voltage. With a storage capacitor of 9 μF , an inductor of 18 μH and a crowbar pseudospark switch, a load of 30 mΩ and an applied capacitor voltage of 40 kV, an impulse current waveform of maximum 25 kA was generated with a rise time and time to half peak value of 17.2 μs and 336μs respectively.

Protection Distance of Surge Protective Devices in Low Voltage Distribution Systems

Protection distance of surge protective devices (SPDs) is an important problem in designing a good location scheme of SPDs in low voltage distribution systems for protecting electrical equipments against over- voltage caused by lightning stroke. The simplified lumped-parameter circuit model and the circuit method were used to study the protection distance problem of SPDs. The analytical solutions of the load voltage and general equations of the protection distance of SPDs under different load conditions were given. Simulation results of examples proved the validity of the proposed analytical method.