HIGH VOLTAGE FUSE-LINKS HIGH VOLTAGE FUSE-LINKS WITH THERMAL STRIKER HIGH VOLTAGE FUSES POWER NEEDS CONTROL

Transcription

1 HIGH VOLTAGE FUSE-LINKS HIGH VOLTAGE FUSE-LINKS WITH THERMAL STRIKER HIGH VOLTAGE FUSES POWER NEEDS ONTROL

2 HIGH VOLTAGE FUSE-LINKS 1. General information High voltage fuse-links (hereinafter called HV fuse-links) are intended for protection of high voltage consumers (lines, transformers, motors, capacitors, switching devices etc.) against thermal and dynamic effects which are caused by the current which exceeds the permitted value as regards amplitude and duration. Owing to the low price, simple maintenance and small dimensions HV fuse-links are a good solution in cases when the usage of other sorts of protection would mean an excessive expenditure with regard to the price of the whole system. a. Short description of construction The construction of ETI HV fuse-link is shown on the figure 1. The base(1) of the fuse-links is made of qualitative brown glazed porcelain( 120 acc. to IE 672). A galvanically protected cap(2) of electrolitic copper is rolled by pressing into the groove of the tube. The tightness of this connection is assured by a special seal resistant to ageing and high temperatures. Inside the tube there is centrically installed an asteroid ceramic carrier(3) on which wire or strip melting elements(4) are coiled with precisely worked out weakened spots. As many as possible melting elements of pure silver are connected in a parallel way so that their thickness is as little as possible - and this is one of conditions for the correct function of the melting element in case of overload of the current. Melting elements are welded on both caps by means of a special copper strip. The inside of the tube is filled with quartz sand with exactly determined granulation. The sand guarantees good extinguishing of the electric arc in due time and in this way assures a high breaking capacity. An important element in the construction is also the striker system(5) the part of which is a striking needle - which in case that the melting elements fuses - springs out of the cap. This striking needle can function as an optical indicator in case that the melting element fuses or with its force it actuates some switching mechanism and in this way signals the state of fusing. Dimensions and characteristics of the force depending on the way of the striking needle are shown on the figure 2. ETI offers two versions of fuse-links: A version with the striker system - type (medium type acc. to IE item 4.14, table 11) and a version without striking system - type A. d ø e FIGURE 1 b. Advantages of HV fuse-links of the ETI production are: - high breaking capacity and reliable interruption of critical current - reliable interruption at minimal current - favourable characteristic of cut-off current - low power dissipation - switching voltages during interruption are essentially lower than prescribed - equal design for indoor and outdoor application - quality melting elements - reliable operation of the striker system. Force/Kraft F (N) Travel/W Pot eg (mm) c. Quality control ETI has implemented a system of quality control according to ISO 9001 since 1993 which is certified by BVQI FIGURE 2

3 d. Accordance with standarts - IE (01/2002) urrent limiting fuses - IE 549 (1976) High-voltage fuses for the external protection of shunt power capacitors - IE 644 (1979) Specification for high-voltage fuse-links for motor circuit applications - IE 787 (1983) Application guide for the selection of fuse-links of high-voltage fuses for transformer circuit applications - EN (1983) High-voltage fuses, Part 1: urrent-limiting fuses - VDE 0670 Teil 4 (07/90) Bestimmungen für Wechselstromschaltgeräte für Spannung über 1kV (Sicherung) - VDE 0670 Teil 402 (05/88) Auswahl von strombegrenzenden Sicherungen für Transformatorstromkreise - DIN (11/83) Hochspannungs-Sicherung, Nennspannungen 3/3,6kV bis 30/36kV 2. Technical data onsidering the above mentioned standards there are two main types of HV fuse-links: A: back-up current limiting fuse-links B: general purpose fuse-links The graphical layout of the working regions of both types of fuse-links is shown in figure 3. back-up current limiting fuse links general purpose fuse links I N I TM I 1h I MIN I 1... rated current of HV fuse-link... minimum melting current of HV fuse-link... current which causes fusing of HV fuse-link in 1 hour... minimum breaking current... rated breaking capacity 0 Invv It I1h Im I1 not allowed region of function of HV fuse-link allowed region of function of HV fuse-link FIGURE 3 A. Back-up current limiting fuse-links Back-up current limiting fuse-links are intended for protection in a limited current region from the minimum current of fusing Imin to the rated breaking capacity I1. These fuse-links are not intended for protection of consumers in the current region between In and Imin. Their construction is of such sort that these currents can destroy the complete fuse-link. This type of HV fuse-links has been a standard product of ETI for a long time and therefore a lot of knowledge and experience have been built into it which assures a quality product and reliable protection. Their quality is attested also by positive type tests in ESI, Milan and IEL Warsaw test laboratories. Figure 4 shows an example of the oscilogramme of the test of breaking capacity of the fuse-link a- 24 kv/100a. We can see that the voltage of the arc is only kv (=1.48x 2xUn ) which is essentially less than the upper limit which is permitted by the standard IE (2.2x 2xUn=74.7kV). Figure 5 shows I/t characteristics and figure 6 shows characteristics of cut-off current of back-up current limiting fuse-links. The internal mark of ETI for back-up current limiting fuse-links is a. With regard to the type of the indicator we distinguish between type a-a (without striker system) and type a- (with built-in striker system of medium power). U 20 kv EN 120 kj 2 I T 2 40 ka sec msec ESI - gps :94/ FIGURE

4 Data for ordering and the most important electrical data of back-up current limiting fuse-links. rated voltage rated current type code No. dimens. dimens. rated breaking smallest breaking cold resistance power dissipation weight U N (kv) I N (A) e d capacity (ka) current I 3 = I min (A) R hl (mv) P v (W) (kg) , , , , ,5 20,6 1, ,7 21,1 7, ,8 26, ,6 30, ,7 46, ,2 53, , ,3 70,1 1, ,1 76, ,7 86, , , , , , ,7 34,3 1, ,9 35, ,4 44, , , ,4 88, , , , , , ,8 184

5 Data for ordering and the most important electrical data of back-up current limiting fuse-links. rated voltage rated current type code No. dimens. dimens. rated breaking smallest breaking cold resistance power dissipation weight U N (kv) I N (A) e d capacity (ka) current I 3 = I min (A) R hl (mv) P v (W) (kg) , , , ,4 1, ,3 51, ,6 65,3 17, ,3 74, , , , , , , , , , ,4 2, , , , , , , , , , , , ,

6 B. General purpose fuse-links General purpose fuse-links are new in the production programme of ETI. They are intended for interruption of overload currents - from the ones which cause fusing of the fuse-link within one hour up to rated breaking capacities. This type of fuse-link is used above all in cases when the protected object has no additional protection against overload on the low voltage side and in this way there can appear such overloads on the secondary side which would destroy the ordinary back up fuse-link. The internal mark of ETI for general purpose fuse-links is g. As regards the construction they are completely the same as fuse-links which were described in the item 1.A. It also applies for them that they can be made in version without striker system (g-a) and in version with striker system (g-). The only difference between the two types of the fuse -links is in the melting element which is at the same time also the most important part of the back up current limiting fuse-link. It is made of silver strips (or wires) of high chemical purity and it is additionally weakened on several places. At the same time solder is applied on some spots (M-effect!). With wire melting elements the required function is achived by the correct shaping of Ag wire melting elements which are all treated according to a special procedure. Generally speaking: in the region of overloads between In and ca. 3In the active part of melting element is the one which has built in additional weakenings and solder while in the region of higher overloads the classical melting element operates. By careful design we determined exactly the points where the characteristics of both parts meet. The internal ETI mark for general purpose fuse-links is g. With regard to the type of the indicator we distinguish between the type g-a (without striker system) and the type g- (with built in striker system of medium power). Data for ordering and the most important electrical data of general porpose fuse-links. rated voltage rated current type code No. dimens. dimens. rated breaking smallest breaking cold resistance power dissipation weight U N (kv) I N (A) e d capacity (ka) current I 3 = I min (A) R hl (mv) P v (W) (kg) , , , ,3 19, ,7 23, ,3 37, ,4 50,2 3, ,1 70, ,3 91, , ,1 2, , ,6 39, ,5 46, ,6 75, ,8 4, ,3 140, ,7 182,7

7 HIGH VOLTAGE FUSE-LINKS WITH THERMAL STRIKER ETI, a well recognized manufacturer of low and high voltage fuse links has introduced an innovation to its range of products, the THERMO, a high voltage fuse link which also incorporates thermal protection. For rated currents 160A (rated voltage 12kV) and 100A (rated voltage 24kV) there is a choice of either the standard indicator with firing pin force of 50N and the new indicator with firing pin force of 80N. In addition, this new indicator is also temperature sensitive due to an additional integral element which reacts in cases of temperature increase of the fuse link due to various reasons. The reaction temperature is set at 100. This provides an important additional function to the VW fuse link, with a blow-out indicator which will react in the following circumstances: -In the event of an increase in ambient air temperature, a special integral mechanism will react by releasing the indicator pin (affecting the mechanism connected to the release device even in cases where the fuse link element has not cut out. - In the event of an incorrectly calibrated fuse link in relation to power supply user parameters (transformer..) and in cases where a fuse link is calibrated to react in surroundings close to the minimum breaking current. -In the event of an increase in temperature due to poor contact between the fuse link and its base. The standard function of the indicator mechanism in cases of a fuse link blow-out is completely independent and the thermal indicator does not affect the primary function of the fuse link. rated voltage rated current indicator type code dimension dimension rated breaking minimum breaking cold resistance power dissipation weight U N (kv) I N (A) (, medium) No. e d capacity (ka) current I 3 = I min (A) R hl (m ) P v (W) (kg) A A A ,5 25 2, A , A , , A A , ,9 62 4,0 100 A , , A , A , , A ,7 85 3, , A , ,8 rated voltage rated current indicator type code dimension dimension rated breaking minimum breaking cold resistance power dissipation weight U N (kv) I N (A) (, medium) No. e d capacity (ka) current I 3 = I min (A) R hl (m ) P v (W) (kg) A , A , , A ,5 46 2, , ,5 50 A , , A A , , A , , A , , , A , , A , ,2 76 5,8 80 A , , ,5 190

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