Gas Filled Capacitor Technology

Web: www.circutor.com

VIAL SANT JORDI, S/N E-mail: central@circutor.es

08232 VILADECAVALLS (BARCELONA) Tel: (+34) 93 745 29 00

ESPAÑA / SPAIN Fax: (+34) 93 745 29 14

NEW RANGE OF CYLINDRICAL CAPACITORS FILLED WITH INERT GAS
Ongoing technological improvement of our products

Since its incorporation 35 years ago, CIRCUTOR S.A. has focussed all its efforts on producing
equipment that helps make rational use of electric energy, that is to say, to improve ENERGY
EFFICIENCY, a very popular concept at the moment, and one which has become a global target
worldwide.

Power capacitors are among the products that have always contributed to achieving high levels of
energy efficiency. They are used, individually or in automatic arrays of capacitors, to compensate
reactive energy in facilities. CIRCUTOR has developed ongoing innovations and technological
improvements in this field, ranging from the first intelligent, micro-processor-based regulators to
current regulators which can compensate not only by measuring the three phases, but also phase
by phase to guarantee perfect correction of the fi cosine, also including automatic arrays with
static operation (thyristors), which enable instant compensation regardless of load variations. One
more 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 power
comprised between 10 kVAR with 3 x 440 V / 50 Hz (8 kVAR with 3 x 400 V / 50 Hz) and 30 kVAR
with 3 x 440 V / 50 Hz (25 kVAR with 3 x 400 V / 50 Hz), which offers a large number of
combinations for setting up automatic arrays of capacitors, as in the case of the new STD series of
automatic arrays from CIRCUTOR (Fig. 2).

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Fig. 1 Fig. 2

Main advantages of this type of capacitors

These capacitors are naturally developed using the latest technology commonly applied to the
production of power capacitors, essentially designed to compensate reactive energy, which is
based on using a film of metallized polypropylene as a dielectric (MKP technology), granting the
capacitors a series of advantages over former technology based on a metallized paper dielectric
and the use of impregnating agents consisting of polychlorobiphenyls (PCB), including mainly the
following 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, the
absence 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 in
addition 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.

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• 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 capacitor
similar to that achieved with liquid oils.

Safety systems

The degradation of polypropylene-film capacitors basically occurs due to the loss of capacitance in
the capacitor caused by the self-healing phenomena of the polypropylene film, when the latter
has been subject to states of thermal or electric overload, which can include mains voltage surge
scenarios, high ambient temperature, presence of harmonic currents on the network to be
compensated or even a high number of connection operations. Furthermore, with the passage of
time, the polypropylene also suffers chemical degradation, which adds to the previously listed
negative effects.

It is therefore of utmost importance to equip the capacitors with suitable protection systems in
order to guarantee, whenever necessary, that they can be disconnected without causing any
damage to the adjoining elements (other capacitors, handling equipment, regulator, etc.). In this
way, CLZ-FP capacitors include a system for protection against voltage surges, which acts in the
event of an increase in its internal pressure by a value of more than approximately 506 hPa (0.5
bar), disconnecting the capacitor from the mains as shown in Fig. 3.

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Fig. 3

Production process

The main components of the CLZ-FP gas-filled capacitors can be seen in Fig. 4.

Fig. 4

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Its manufacturing process includes, as a main premise for the production of any CIRCUTOR
product, the achievement of maximum quality and reliability guarantees. In this way and given the
special nature of these capacitors, their production process includes a number of aspects that
deserve 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.

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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

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• 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. 8

Conclusions

The new CLZ-FP capacitors filled with inert gas are the perfect complement for the well-known
prismatic 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. In
addition, these capacitors can be used in association with reactors to avoid amplifying harmonic
currents in facilities with high levels of harmonic pollution, and even in applications intended for
filtering harmonics by means of passive filtering devices.

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Gas Filled Capacitor Technology

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