CS274062B1

CS274062B1 - Method of model conductors' insulations' discontinuous cross-linking

Info

Publication number: CS274062B1
Application number: CS212689A
Authority: CS
Inventors: Stanislav Ing Rovny; Juraj Ing Csc Kovac
Original assignee: Stanislav Ing Rovny; Juraj Ing Csc Kovac
Priority date: 1989-04-06
Filing date: 1989-04-06
Publication date: 1991-04-11
Also published as: CS212689A1

Abstract

The solution can be used in electrotechnical industry in testing of cable insulation cross linking. By the proposed solution it is possible to achieve a fast heating of a sample to a required temperature, which enables an exact definition of netting time and evaluation of the test and to process of netting. The netting is performed in an atmosphere of inert gas, which eliminates negative influences of the surrounding environment on the insulation characteristics. The model wires are fixed in a pressure tank and then they are connected to a source of electric heating current, while the netting tank is filled with an inert gas. After netting the model wires are cooled to the temperature of the surrounding environment by cooling water.<IMAGE>

Description

Vynález sa týká spůsobu diskontinuálneho sieťovania izolácií modelových vodičov.The invention relates to a method of discontinuous crosslinking of model wire insulations.

Cielom vynálezu je navrhnutie spůsobu, pri ktorom sa odstráni neistota v odmeriavaní času ú sieťovania.It is an object of the invention to provide a method in which the uncertainty in the measurement of the cross-linking time is eliminated.

Doteraz sa pri vývoji izolácií zo zosietených materiálov používali prevažne dva spůsoby sieťovania izolácií modelových vodičov. Při prvom spůsobe sa modely sieťujú priamo na výrobných zariadeniach pre kontinuálnu výrobu. Avšak tento spůsob nevyhovuje z toho důvodu, že příprava takéhoto spůsobu sa ukázala ako neekonomická, pretože spotřeba zosieteného PE na jednu vzorku je asi 300 kg. Při druhom spůsobe sa modelové vodiče uzavru do reaktora, v ktorom sa zohrejú konvexně postupujúcim teplom zo stien reaktora alebo nasýtenou vodnou parou s teplotou okolo 210 °C. Při tomto konvexnom ohřeve je rýchlosť ohřevu i chladnutia daná predovšetkým tepelnou kapacitou zariadenia, čiže zotrvanie vzoriek v určitom teplotnom intervale je velmi neisté. Přestup tepla do vzoriek je prakticky nemožné kontrolovat meraním, pretože akékolvek čidlo, napr. termočlánok, odporový teploměr a pod. vnáša chyby do merania tým, že má vlastnú tepelné kapacitu a spravidla odlišný koeficient sálania. Na vlastnosti zhotovenej izolácie vplýva tiež prostredie, v ktorom sietbvanie prebieha. Pri použití vodnej páry dochádza k nepřiaznivému vplyvu vody na vlastnosti zosieteného materiálu tým, že sa vytvárajú vodné stromčeky.Until now, two types of cross-linking of model wire insulation have been used in the development of cross-linked insulation. In the first method, the models are networked directly on the continuous production equipment. However, this method is unsatisfactory because the preparation of such a method has proven uneconomical, since the consumption of cross-linked PE per sample is about 300 kg. In the second method, the model conductors are enclosed in a reactor in which they are heated by convexly advancing heat from the reactor walls or saturated water vapor at a temperature of about 210 ° C. In this convex heating, the heating and cooling rates are mainly determined by the thermal capacity of the device, so the residence of the samples at a certain temperature interval is very uncertain. The heat transfer to the samples is virtually impossible to control by measurement, since any sensor, e.g. thermocouple, resistance thermometer, etc. it introduces measurement errors by having its own thermal capacity and, as a rule, a different radiation coefficient. The properties of the insulation produced are also influenced by the environment in which the digestion takes place. When using water vapor, water adversely affects the properties of the crosslinked material by forming water trees.

Uvedené nevýhody odstraňuje navrhované riešenie, ktorého podstata spočívá v tom, že modelové vodiče sú po upevnění v tlakovej nádobě a po vyplnění nádoby inertným plynom, připojené na zdroj elektrického vykurovacieho prúdu prechádzajúceho jadrami. Výkon prúdu musí postačovat na to, aby sa teplota potřebná na sieťovanie dosiahla za čas, ktorý je menší ako 20 % doby sieťovania a regulovatelný tak, aby sa teplota počas sieťovania udržiavala konštantná a po uplynutí sieťovacieho času sa modelové vodiče rýchlo ochladia chladiacou vodou pod 90 °C, kedy už neprebieha sieťovanie a následné sa dochladia na teplotu okolia.These disadvantages are overcome by the proposed solution, which is based on the fact that the model conductors are connected to the source of electric heating current passing through the cores after being fixed in the pressure vessel and after filling the vessel with inert gas. The power output must be sufficient to allow the temperature required for crosslinking to reach less than 20% of the crosslinking time and controllable so that the temperature is kept constant during crosslinking and, after the crosslinking time, the model conductors are rapidly cooled with cooling water below 90 ° C, when no crosslinking takes place and then cooled to ambient temperature.

Výhodou riešenia podía vynálezu,je najma to, že sieťovanie prebieha v lubovolnej atmosféře inertného plynu, čo umožňuje vylúčenie negativného vplyvu prostredia na vlastnosti zhotovenej izolácie. Tak isto pri tomto spůsobe tepelná zotrvačnosť zariadenia nespůsobuje neistotu v odmeriavaní času sieťovania, pretože teplo vzniká prechodom elektrického prúdu jadrom modelového vodiča - vzorky a teplota sa zlsťuje z elektrického odporu jadra výpočtom. Uvedený spůsob umožní regulováním příkonu rýchle ohriatie jadra vzorky na požadovanú teplotu a tým aj přesné stanovenie doby sieťovania. Výhodou je tiež to, že sa zvýši přesnost vyhodnotenia skúšky a procesu sieťdvania.The advantage of the solution according to the invention is, in particular, that the crosslinking takes place in any inert gas atmosphere, which makes it possible to eliminate the negative influence of the environment on the properties of the insulation produced. Also, in this manner, the thermal inertia of the device does not cause uncertainty in the measurement of the crosslinking time, since heat is generated by passing the electric current through the core of the model conductor - the sample, and the temperature decomposes from the electrical resistance of the core by calculation. Said method will allow for rapid heating of the sample core to the desired temperature by controlling the power input and thereby accurately determine the crosslinking time. It is also an advantage that the accuracy of the test evaluation and networking process is increased.

V následujúcom příklade je uvedený opis konkrétného prevedenia. Modelová žila s 2 vodivým jadrom s prierezom 4 mm z elektrovodnej médi a s izoláciou z nízkohustotného polyetylénu PELD s přísadami reakčného činidla, peroxidu, ktorý spůsobuje zosietenie antioxidantov tepelne stabilizujúcich PELD a stabilizátormi proti starnutiu, sa navinie na držiak modelových žil v dížke 54,5 m tak, že volná dlžka žily bez dotyku s držiakom, stěnou sieťovacej nádoby alebo susednými vzorkami; umožní získat 62 vzoriek s minimálnou dlžkou 750 mm. Konec žil sa vodivo spoja s kontaktami na držiaku. Držiak so žilami sa vloží do sieťovacej nádoby a nádoba se uzavrie. Vývevou sa vyčerpá vzduch a nádoba sa naplní dusíkom na tlak 0,0 MPa. Vzcrka sa počas dvoch minút vyhřeje na teplotu 210 °C a elektrickým prúdom s hodnotou 94 A sa táto teplota udržuje počas 10 minút. Po uplynutí tohto času sa vypne přívod prúdu a sieťovacia nádoba sa za tlaku zaplní chladiacou vodou a vzorky sa prudko ochladia na 90 °C, potom sa postupné ochladzujú na teplotu okolia, pri ktorej už neprebieha zosietenie izolačnej vrstvy modelovej žily. Po ochladení sa voda vypustí zo sieťovacej nádoby a vyrovná sa tlak s okolím.The following example provides a description of a particular embodiment. Model core with 2 conductive core with 4 mm cross-section of conductive medium and insulation of low-density polyethylene PELD with reagent additives, peroxide, which crosslinks PELD heat-stabilizing antioxidants and anti-aging stabilizers, is wound onto the model cores holder 54 m such that the free length of the vein is without touching the holder, the cross-link vessel wall or adjacent specimens; allows to obtain 62 samples with a minimum length of 750 mm. The end of the cores is conductively connected to the contacts on the holder. The vein holder is placed in a cross-linking vessel and the vessel is closed. The pump is exhausted of air and the vessel is filled with nitrogen to a pressure of 0.0 MPa. The sample was heated to 210 ° C for two minutes and maintained at a temperature of 94 A for 10 minutes. After this time, the power supply is turned off and the crosslinking vessel is filled with cooling water under pressure and the samples are quenched to 90 ° C, then gradually cooled to ambient temperature at which the cross-linking layer of the model vein is no longer crosslinked. After cooling, the water is drained from the crosslinking vessel and the pressure is brought to ambient.

Riešenie podía vynálezu možno využiť v elektrotechnickom priemysle při skúškach zosieťovania káblových izolácií a při stanovovaní optimálneho času zosiefovania pře různé materiály.The solution according to the invention can be used in the electrical industry in cable cross-linking tests and in determining the optimum cross-linking time for various materials.

Claims

Method of discontinuous crosslinking of model conductor insulators mounted in a pressure vessel, characterized in that, after filling the pressure vessel with inert gas, the attached model conductors are connected to an electric current passing through the cores, the power of which is sufficient to achieve the networking temperature over time shorter than 21 µl of sieve time, while the electrolytic power of the electric current keeps the top temperature constant during sieving and after the crosslinking time has elapsed, the model conductors are rapidly cooled with cooling water below 90 ° C, when the crosslinking is no longer crosslinking.