Gas Filled Capacitor Technology

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  • 1. Web: www.circutor.comVIAL SANT JORDI, S/N E-mail: central@circutor.es08232 VILADECAVALLS (BARCELONA) Tel: (+34) 93 745 29 00ESPAÑA / SPAIN Fax: (+34) 93 745 29 14 NEW RANGE OF CYLINDRICAL CAPACITORS FILLED WITH INERT GAS Ongoing technological improvement of our productsSince its incorporation 35 years ago, CIRCUTOR S.A. has focussed all its efforts on producingequipment that helps make rational use of electric energy, that is to say, to improve ENERGYEFFICIENCY, a very popular concept at the moment, and one which has become a global targetworldwide.Power capacitors are among the products that have always contributed to achieving high levels ofenergy efficiency. They are used, individually or in automatic arrays of capacitors, to compensatereactive energy in facilities. CIRCUTOR has developed ongoing innovations and technologicalimprovements in this field, ranging from the first intelligent, micro-processor-based regulators tocurrent regulators which can compensate not only by measuring the three phases, but also phaseby phase to guarantee perfect correction of the fi cosine, also including automatic arrays withstatic operation (thyristors), which enable instant compensation regardless of load variations. Onemore step in this continuous technological improvement is the market launch of the new three-phase capacitors, enclosed in a cylindrical aluminium case filled with inert gas.These new capacitors correspond to the models of the CLZ-FP range (Fig. 1), with powercomprised between 10 kVAR with 3 x 440 V / 50 Hz (8 kVAR with 3 x 400 V / 50 Hz) and 30 kVARwith 3 x 440 V / 50 Hz (25 kVAR with 3 x 400 V / 50 Hz), which offers a large number ofcombinations for setting up automatic arrays of capacitors, as in the case of the new STD series ofautomatic arrays from CIRCUTOR (Fig. 2). 1
  • 2. Web: www.circutor.comVIAL SANT JORDI, S/N E-mail: central@circutor.es08232 VILADECAVALLS (BARCELONA) Tel: (+34) 93 745 29 00ESPAÑA / SPAIN Fax: (+34) 93 745 29 14 Fig. 1 Fig. 2Main advantages of this type of capacitorsThese capacitors are naturally developed using the latest technology commonly applied to theproduction of power capacitors, essentially designed to compensate reactive energy, which isbased on using a film of metallized polypropylene as a dielectric (MKP technology), granting thecapacitors a series of advantages over former technology based on a metallized paper dielectricand the use of impregnating agents consisting of polychlorobiphenyls (PCB), including mainly thefollowing among others: fewer losses, greater capacitance stability, smaller size and weight, self-healing capability of the dielectric in the event of a failure in any of the capacitive elements, theabsence of highly flammable impregnating agents and, obviously, the use of non-toxic,biodegradable materials.The use in this case of impregnation by inert gas offers a number of important advantages inaddition to those listed, the main ones being:• Complete elimination of the risk of leaks that exists with capacitors impregnated with oil and, therefore of the possibility of said oil catching on fire. The absence of leaks also allows for a greater diversity of installation positions, which can be adapted to different types of enclosures.• Less weight compared with other cylindrical capacitors with similar power, thus reducing the transport costs of the capacitors and the automatic arrays equipped with the latter. 2
  • 3. Web: www.circutor.comVIAL SANT JORDI, S/N E-mail: central@circutor.es08232 VILADECAVALLS (BARCELONA) Tel: (+34) 93 745 29 00ESPAÑA / SPAIN Fax: (+34) 93 745 29 14• Increased efficiency of the protection system with an internal relief valve, since the gases emitted in the event of a failure of the capacitive elements act on said system, since there is no liquid (oil) or solid (thermosetting resin) impregnating agent inside the capacitor.• Higher specific capacitance compared with those filled with liquid oil.• Guarantee of full environmental protection, since the capacitors are free from oils and other impregnating agents and filled with a completely harmless and inert gas.All these features are achieved while also maintaining an internal cooling level of the capacitorsimilar to that achieved with liquid oils.Safety systemsThe degradation of polypropylene-film capacitors basically occurs due to the loss of capacitance inthe capacitor caused by the self-healing phenomena of the polypropylene film, when the latterhas been subject to states of thermal or electric overload, which can include mains voltage surgescenarios, high ambient temperature, presence of harmonic currents on the network to becompensated or even a high number of connection operations. Furthermore, with the passage oftime, the polypropylene also suffers chemical degradation, which adds to the previously listednegative effects.It is therefore of utmost importance to equip the capacitors with suitable protection systems inorder to guarantee, whenever necessary, that they can be disconnected without causing anydamage to the adjoining elements (other capacitors, handling equipment, regulator, etc.). In thisway, CLZ-FP capacitors include a system for protection against voltage surges, which acts in theevent of an increase in its internal pressure by a value of more than approximately 506 hPa (0.5bar), disconnecting the capacitor from the mains as shown in Fig. 3. 3
  • 4. Web: www.circutor.comVIAL SANT JORDI, S/N E-mail: central@circutor.es08232 VILADECAVALLS (BARCELONA) Tel: (+34) 93 745 29 00ESPAÑA / SPAIN Fax: (+34) 93 745 29 14 Fig. 3Production processThe main components of the CLZ-FP gas-filled capacitors can be seen in Fig. 4. Fig. 4 4
  • 5. Web: www.circutor.comVIAL SANT JORDI, S/N E-mail: central@circutor.es08232 VILADECAVALLS (BARCELONA) Tel: (+34) 93 745 29 00ESPAÑA / SPAIN Fax: (+34) 93 745 29 14Its manufacturing process includes, as a main premise for the production of any CIRCUTORproduct, the achievement of maximum quality and reliability guarantees. In this way and given thespecial nature of these capacitors, their production process includes a number of aspects thatdeserve to be highlighted:• Once the coils are installed inside the aluminium tube, it is essential to ensure the removal of any possible moisture from the elements that make it up, for which reason each capacitor is subjected to a long, exhaustive vacuum process, in autoclaves such as shown in Fig. 5. It is essential to make sure that no trace of moisture or oxygen remains inside the capacitor to avoid rusting of the metallized part of the polypropylene film, which would cause rapid degradation of the capacitor, increasing its dielectric losses and internal discharges and reducing its capacitance. Fig. 5• Having completed the vacuum process, the capacitors are filled with a mix of gases N2 (nitrogen) and He4 (helium gas isotope with an atomic mass of 4; a natural element which has very low density and is colourless, odourless and flavourless), again under vacuum conditions, to achieve an internal pressure in the capacitor of slightly more than 1013 hPa (1 atm). Fig.6 shows a detail of this filling process. 5
  • 6. Web: www.circutor.comVIAL SANT JORDI, S/N E-mail: central@circutor.es08232 VILADECAVALLS (BARCELONA) Tel: (+34) 93 745 29 00ESPAÑA / SPAIN Fax: (+34) 93 745 29 14 Fig. 6• As can be seen in Fig. 6, during the capacitor filling and sealing process, the lid already comprises the terminals required for its connection to the mains. These terminals already include the discharge resistors required to discharge the capacitor to a value of less than 75 V three minutes after it is disconnected from the mains (Fig. 7), as specified in applicable standard IEC 60831-1. Fig. 7 6
  • 7. Web: www.circutor.comVIAL SANT JORDI, S/N E-mail: central@circutor.es08232 VILADECAVALLS (BARCELONA) Tel: (+34) 93 745 29 00ESPAÑA / SPAIN Fax: (+34) 93 745 29 14• The production process ends with the performance of a basic test to guarantee the quality and full reliability of each capacitor, which consists of checking that the sealing process was performed correctly and that there are no leaks of the internal gas. To perform this test, each capacitor is individually inserted in a machine that checks for the presence of helium gas (He4). The detection of this gas would indicate a leak in this capacitor, which would obviously be removed from the subsequent final packaging process. Fig. 8 shows various parts of said process to test for He4 gas. Fig. 8ConclusionsThe new CLZ-FP capacitors filled with inert gas are the perfect complement for the well-knownprismatic capacitors filled with vermiculite developed more than twenty years ago by CIRCUTOR,offering maximum performance in terms of reliability and sturdiness, and with a very low price. Inaddition, these capacitors can be used in association with reactors to avoid amplifying harmoniccurrents in facilities with high levels of harmonic pollution, and even in applications intended forfiltering harmonics by means of passive filtering devices. 7