ESTA, spol. s r.o.
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| ESTA, spol. s r.o. Kounická 68 664 91 Ivančice Tel.: +420 546 451 048 |
Tel.: +420 546 211 785 Tel.:/Fax: +420 546 434 161 E-mail: obchod@esta.cz Web: http://www.esta.cz |
Fittings
Fittings for insulated disengaged lines 1 – 45 kV
Partially insulated medium-voltage systems represent an alternative for bare loose leads and they feature many significant advantages in comparison with them. Insulated medium-voltage loose leads as a three-phase system on the basis of separate conductors are more and more extensively used but they do not represent any full-insulation system. They only provide protection against accidental contacts.
Fittings for bare loose leads up to 45 kV
Bare low and medium voltage leads and the most frequently used leads for electric power distribution.
Fittings for light wave conductors
Ground cables are used for grounding of loose leads and their protection against thunder strokes, so as to increase operation safety of the whole device. There are engaged various rope constructions. So as to cover the permanently growing necessity of data transfer, the grounding ropes of loose high voltage leads have been equipped with elements of glass fibres for several years – these allow fast and safe transfers of large data quantities. Initially, these included mainly the internal operation tasks of data transfer and distance control, controlled via glass fibres. At the present time, the fibres are also used by external institutes for diverse transfers. High voltage air leads are used „not only“ for current transfer, but also for national and international telex and data connections. Ground cables (ropes) with glass fibre elements are called light wave conductors with metallic protection (optical ground wire – OPGW). On the basis of sensible internal acts of the conductors it is not possible to apply any national load-bearing or anchoring fittings as they show non-permitted large radial powers referring the conductor. Due to this reason the light wave conductors preferentially use spiral fittings or specially adjusted clamps, e.g. conic anchoring clamps. These do not show any radial powers dangerous to the conductor. Non-metal light wave conductors – air cables with plastic external cover can not be used as ground cables due to their dielectric character. These types of conductors are additionally led in bare lines as a medium for data transfer. There are always used the same fittings as in case of metal – protected light wave conductors , but without additional grounding. Non-metal light wave conductors (LWL) in the medium voltage zone, along train routes or in case of other application with short fields of span are usually lead on pulleys. This technology allows beneficial assemblage costs on one side, as in fact the load-bearing pulley also acts as a an anchoring pulley, while – on the other hand – it allows safe operation of the light wave conductor, as the air cable may – in case of a breach, e.g. a tree fall or in case of hoarfrost – freely move in the pulleys.
Fittings for disengaged insulated lead up to 1 kV
Insulated disengaged lines more and more frequently replace bare leads in low voltage networks and they show some significant benefits to be specified here below:
- the individual conductors are connected by a relatively long winding to one bundle and they can be used in networks up to 1000V of operation voltage
- due to small distances of phases, the induction resistance is much lower than in case of bare conductors. That causes lower voltage drop for conductors of identical cuts
- in case of leads across forest areas there are eliminated majorities of forest paths as well as consequent branch removal
- it is a known fact that frost on plastic is usually very low and so there is significantly reduced the snow and frost loading
- thanks to elimination of phase distances there may be used shorter wooden poles and roof poles, which reduces the costs
- the insulated disengaged lead cover saves costs thanks to installation and regulation of only one bundle instead of four individual conductors
- the operation safety is much higher as falling branches do not cause any short circuits and that is why less repairs are needed
- there may be kept much shorter safety distances which leads to partial cost savings
- the new system may be assembled on existing poles
- full insulation of networks provides maximal protection against inadvertent contacts
In principle, there are used two systems of conductors:
- All the phase conductors and the zero conductor are insulated, they have the same cut and they are of identical material. All the conductors are clamped on suspension and anchoring points
- The zero conductor, which is also used as a load-carrying rope (cable) usually shows smaller cut and but there is used stronger material. The conductor is usually insulated, but non-insulated zero conductors are also quite usual.
Conductors for street lighting may be additionally led together with phase conductors and the zero conductor in most systems.
Should you have any questions, contact us at obchod@esta.cz.