Wooden supports are undesirable for lightning arresters on account of the fire risk incurred; this, however, may be reduced to a minimum by employing skeleton boards and using sheets of asbestos between the arresters and the wood.
On some switchboards are also mounted small transformers for raising or lowering the voltages, and lightning arresters as a protection from lightning.
These arresters were watched during an entire lightning season to see which bank of arresters on each wire discharged the most lightning to earth.
In general the lines should be provided with lightning arresters at least where they run over hilltops and at any points where lightning strokes are unusually frequent.
Transmission lines, on entering a station or sub-station, should pass to the arresters at once and before connecting with any of the operating machinery.
The number and total length of air-gaps in a bank of arresters necessary to prevent the formation of arcs by the regular line voltage depends on a number of factors besides the amount of that voltage.
If these metals were used for the cylinders of arresters the beads on their surface would quickly bridge the short air-gaps.
Accurate data are lacking as to the amount of this resistance that should be employed with arresters for any given voltage.
At the juncture of the overhead line and the cables there is a terminal house containing lightning arresters, and there are also arresters at the Chambly plant and the Montreal sub-station.
If the buildings are of wood, the arresters had better be outside in weather-proof cases, but in brick or stone buildings the arresters may be properly located near an interior wall and well removed from all other station equipment.
A good earth connection for lightning arresters may be made through large water-pipes, but to do this it is not enough simply to wrap the wire from the lightning arresters about the pipe.
Where a long overhead line joins an underground cable arresters should always be connected, and the same is true as to transformers located on the transmission line.
A small house for arresters and choke-coils was built close to the generating station of this system and they were mounted therein on wooden frames.
Lightning arresters are in some cases connected across high-voltage circuits from wire to wire so that the full line pressure tends to force a current across the air-gaps.
Finally, as the guard wire was not removed after the new lightning arresters were erected, it is possible that this wire prevented some direct discharges over the transmission wires that would have been destructive.
Four choke-coils were connected in series with each line wire, and between these choke-coils three lightning arresters were connected, while a fourth arrester was connected to the line before it reached any of the choke-coils.
The number and ohmic value of the resistance rods used in the various arresters depend upon the voltage and current of the circuit.
For direct connection to busbars, arresters with charging resistance should be used.
Arresters for cable systems differ from arresters for overhead circuits only in the construction of the horn gaps.
In general the construction of lightning arresterscomprise 1.
Opinions on the design of choke coils for use with lightning arresters vary considerably.
These arrestersmay be installed outside on poles or buildings, or indoors on station walls.
In connection with lightning arrester installations, disconnecting switches are particularly useful, providing a simple and effective means for isolating the arresters while cleaning and inspecting.
Kinks and sharp bends in the wire running from the outdoor lines to the arresters and from arresters to ground should be avoided as far as possible.
Lightning arresters used on heavy duty circuits are designed to rupture the arc as soon as formed.
Lightning arresters may be divided into three classes, according as their action depends upon the effects of: 1.
What provision is made to prevent the destruction of arresters by the line current?
Western Electric Air-Gap Arrester] The Kellogg Company regularly equips its magneto telephones with air-gap arresters of the type shown in Fig.
In small magneto exchanges it is not uncommon to employ combined fuse and air-gap arrestersfor central-office line protection, the fuses being of the mica-mounted type already referred to.
For these reasons, a system containing fuses and air-gap arresters only, does not protect against abnormal currents which are continuous and small, though large enough to injure apparatus because continuous.
Carbon Block Arrester] Carbon arresters now are widely used in the general form shown in Fig.
If the carbon arresters are separated by celluloid, it will burn away and allow the carbons to come together, extinguishing the arc.
Usually it discharges across arresters and when this discharge takes place, the line is disturbed in its balance and loud noises are heard in the telephones upon it.
Kellogg Air-Gap Arrester] Vacuum Arresters:--All of the carbon arresters so far mentioned depend on the discharge taking place through air.
The freedom of metal-block arrestersfrom dust troubles gives them a large economical advantage over carbon.
It may slide or turn in many ways and this happily enables many types of arresters to result.
Why is it not necessary to install sneak-current arresters in central-battery subscribers' stations?
In certain regions of the Pacific Coast where the lightning hazard is negligible and the high tension hazard is great, metal-block arresters at the outer ends of cables give acceptable protection.
A defect of most ordinary types of metal air-gap lightning arresters is that heavy discharges tend to melt the teeth or edges of the plates and often to weld them together, requiring special attention to re-establish the necessary gap.
Holtzer-Cabot Arrester] Metallic Electrodes:--Copper or other metal blocks with roughened surfaces separated by an insulating slip may be substituted for the carbon blocks of most of the arresters previously described.
Logging camps must also prevent the destruction of National Forest timber by fire by using spark-arresters on all logging engines.
Railroads are required to use spark-arresters on their locomotives and to provide for keeping their rights-of-way free from inflammable material.
Efficient spark arresters are required on wood and coal burning boilers or locomotives.
While arresters cannot be depended on to eliminate entirely the discharge of sparks under all conditions; yet, when properly built and installed, they materially reduce spark hazard.
Spark Arresters Spark arresters are desirable and, where chimneys are near combustible roofs, lumber, forests, etc.
See Standards for Construction and Installation of Spark Arresters for Chimneys and Stacks, published by the National Fire Protection Association.
Arresters must be kept adjusted in position and renewed when the openings are worn larger than the normal screen openings.
Arresters for domestic purposes should have vertical sides extending upward not less than 9 inches so as to provide a gross area of surface at least twice the net flue area.
Likely Foster would have sent his order out and had those arresters shipped around Cape Horn from New York," he added.
First came a heavy tax for operating the road; and next was an order to put spark arresters on all his engines.
Provide spark arresters for all open-arc lamps in the vicinity of inflammable material.
Spark arresters must so close the upper orifice of the globe that it will be impossible for any sparks, thrown off by the carbons, to escape.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "arresters" in a variety of sentences. We hope that you will now be able to make sentences using this word.
