INMR: January/Febuary 2000 - New Desig...ymeric Arresters Introduced by Siemens
Volume 8 Number 1
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January/Febuary 2000
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Companies in Transition
New Design of Polymeric Arresters
Introduced by Siemens
“The field of transmission and distribution tends to have
very long innovation cycles,” says Harald Fien referring
to exactly such a cycle now taking place for surge
arresters. “In the past, the major technological change in
this component involved the transition from silicon
carbide to zinc oxide. Over the past ten or more years,
another change has been taking place but this time
related to insulation.”
Fien. Siemens philosophy is to offer several
arrester technologies in parallel.
Fien, General Manager of Siemens’ Surge Arrester &
Limiters business located in Berlin, is referring to the
almost wholesale changeover which has been taking
place from porcelain to polymers as the housing
material for MV arresters. He and R&D Director Volker
Hinrichsen, offer their explanations for this development
and also discuss why they believe this changeover is
not yet occuring quite so rapidly in the case of HV
arresters.
“Traditionally, many models of distribution
arresters have tended to fail due to problems with
sealing” says Hinrichsen. “Therefore the benefits
of a leak-tight design using polymers have been
easy for customers to accept. Another factor,” he
notes “is lower cost, particularly at distribution
levels and this has been important since most
customers today focus solely on price and not on
technical benefits. The simple fact is that at
present polymeric-housed arresters are cheaper
than those made with porcelain housings.”
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R&D Director Hinrichsen. Arresters monitored
throughout entire assembly process using bar codes.
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However, for a variety of reasons, Fien and Hinrichsen state that porcelain still
predominates as the housing material for HV arresters and they claim that this is
currently the case not only within Siemens in particular but also within this industry in
general. Major among these reasons has been what they say is a continued lack of
confidence in how polymeric materials age under service conditions.
Actually, according to Hinrichsen, Siemens was one
of the first suppliers to utilize silicone housings for
HV arresters. “Initially,” he says, “our company was
approached by a German utility with a request for a
mechanically strong arrester design which also
provided for greater safety in the event of failure.
From this work, we became convinced that
composite material technology offered advantages
to customers in regard to better pollution
performance as well as mechanical characteristics.”
This past September, Siemens introduced a new
line of silicone-housed MV arresters but with a
much different design concept than was employed
during development of the earlier HV arresters,
which incidentally will continue to be offered in
parallel with the new designs. Hinrichsen explains
why: “we have learned that there is a large segment of the market where cost is really
the only issue and this segment favours a design where the housing is molded directly
onto the internal parts. This differs from our original design concept which employs a
relatively costly hollow tube onto which molding of the housing takes place.”
Fien states that when the development process for the new MV arrester line began
two years ago, there were three major objectives: to be cost competitive with other
manufacturers, especially since Siemens was relatively late in entering this segment
of the market; to offer technical advantages in terms of short circuit performance; and
to offer good performance in regard to minimum flammability of components.
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January/Febuary 2000
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In terms of the first objective - cost, Hinrichsen explains
that, for the market segment covering arresters up to
170 kV, price is very important. This fact has made
direct molding the most practical method for
manufacturing arresters in this range and he speculates
that as more is learned about this type of processing he
foresees possibilities to use it increasingly for HV
applications as well. For example, Siemens is planning
to unveil new directly-molded arresters for voltages up to
170 kV at the Hannover Fair in late March.
With regard to the pressure relief performance objective,
Siemens developed an open cage design principle
which is similar in concept to that used elsewhere in the
industry but different in other aspects. The exact
process of manufacturing the fiberglass rods whch
Open cage design of Siemens line of new
directly-molded polymeric arresters.
comprise the cage and their method of attachment to
the end fittings is considered confidential. However, Hinrichsen claims that this design
is a very effective means of ensuring that all internal parts are kept inside the
structure in the event of failure.
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Hinrichsen notes that this safety aspect is particularly
important to customers in Europe where overhead lines
often pass very close to population centers. “This new
design” he says “gives a high safety against ejection of
internal parts but, unlike our hollow tube design, this
cannot be 100 per cent guaranteed.” He also contrasts the
concept of the open cage design with various wrapping
processes used to enclose the metal oxide blocks and
claims that, by comparison, the open cage offers better
safety under overload conditions.
As regards the third objective - flammability, Hinrichsen
indicates that a minimum of epoxy material has been used
in constructing the components of the open cage and he
again contrasts this with other designs which utilize epoxy
resin-impregnated wrapping material. “There is really no
way to use no epoxy in these arresters,” he observes, “but
the key to prevent excessive flammability is to avoid epoxy
resin as much as possible.”
Porcelain HV arresters still dominate
sales at Siemens by a factor of some 9 to
1. Columns of zinc oxide blocks being
inserted into porcelain housing.
The polymeric material molded onto the open cage of the new Siemens arrester is a
high-temperature vulcanizing (HTV) silicone rubber. Hinrichsen indicates that the
reason to go this route in place of the liquid silicone rubber (LSR) utilized by some
competitors relates both to economy and to the location where final manufacturing is
now taking place. He says that HTV silicone is a less costly material and also points
out that he has noticed a tendency in the market for LSRs to rise in price.
“Perhaps,” he observes, “had we started from the very
beginning with a whole new production facility, we may
have gone the LSR route since the machinery required
is less expensive.” But, instead Siemens has elected to
contract the manufacturing of these arresters to a
Swiss-based supplier of insulators and line hardware
who already had all the equipment in place to
manufacture using HTV silicone. “By going this route,”
explains Hinrichsen, “we have the benefit of using a
lower cost material without having to directly incur the
higher investment costs required.”
General Manager Fien states that a decision was made
to use silicone for the external housing of the new MV
arresters although it was recognized that there is much
competition today from molded arresters with housings
Shaker-table tests conducted on Siemens
HV arresters with composite housings at the
made from EPDM. “We think there will be a movement
Jülich Laboratory in Aachen.
toward silicone,” he notes “and we already know from
our customers that they prefer this material.” According to Hinrichsen, from the very
beginning Siemens decided not to look at EPDM since it was felt that this material had
no real future over the next ten years.
Indeed Sales Director, Jörg Pelmer points out that customers in Europe are willing to
pay a somewhat higher price for superior technical characteristics as for example
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might be offered by a silicone housing. “There is a different philosophy in Europe than
in other areas,” he notes, “since customers here expect distribution arresters to have
a longer lifetime in service. But, this price premium can only be in the area of about 10
per cent.”
INMR®
P.O. Box 95, Westmount (Montréal), Québec, Canada, H3Z 2T1
Telephone: (514) 939-9540 Telefax (514) 939-6151 Email:insunews@odyssee.net
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Volume 8 Number 1
January/Febuary 2000
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High Voltage Arresters a Different Picture
According to Siemens management, the market situation
for HV arresters is quite different from that of distribution
arresters. Here, they state that sales of porcelain arresters
still predominate and outsell polymers by a factor of some
9 to 1. Fien believes the major consideration affecting this
ratio is simply price.
He and Hinrichsen talk about the fact that the Siemens HV
arrester design for silicone housings utilizes a hollow FRP
tube to contain the zinc oxide blocks, meaning that both
the tube and the silicone rubber are important
components of the final cost. He also indicates that
Siemens is working with material and tube suppliers to
reduce the costs of these components as much as
possible. “If we could succeed in bringing the price of our
HV polymeric arresters to match that of porcelain” says
Fien, “then we believe there would be a dramatic change”.
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Pelmer. European-based customers
expect distribution arresters to have a
longer lifetime.
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INMR: January/Febuary 2000 - New Desig...ymeric Arresters Introduced by Siemens
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At the same time, Fien notes that there are still some
applications where the market is shifting to polymeric
HV arresters such as in cases where two or more large
porcelain shells can be replaced by a single hollow core
composite housing. In these instances, the price
comparison of the alternative technologies is similar and
he says that sales arguments tend to be
technically-focused instead of solely based on price.
Says Fien, “if we look at the technical performance of a
single housing composite arrester design versus using
two or more porcelains connected by flanges, it is much
better, as for example in polluted environments.”
Sales Director Pelmer explains that having a focus on
special applications for HV arresters has allowed
Housings of polymeric HV arresters utilize a Siemens to persuade some customers to accept
hollow tube onto which silicone sheds are
composite housings even for normal applications. He
molded.
points out that one example where composite-housed
HV arresters have apparently been well-accepted is where they can also serve as
support insulators. As such they offer cost savings associated with the foundation
work which would be needed for installing a separate station post insulator.
Hinrichsen comments that he has also noticed a trend
on the market to make station equipment as compact as
possible and he notes that solutions integrating arresters
with disconnectors and earthing switches help meet
customer’s evolving needs in this respect. “One such
instance where an arrester has been integrated with a
HV disconnector involved a large German utility which
encountered problems protecting instrument
transformers and circuit breakers at the line entrance as
a result of shielding failures due to multiple lightning
strokes.
The solution here was to install an arrester at the line
entrance to the station to protect both pieces of
equipment. Since an arrester usually has only a limited
protection zone, in this case it was placed where the
Cementing of flanges to porcelain employs
a sulphur-based cement which becomes
disconnector is situated. The final arrester used for this
mechanically strong in only 5 minutes.
application is basically a standard model but with
different grading rings. “This whole area of innovative ideas to help reduce costs at
substations could well become a major market tendency for arresters,” remarks Fien.
Fien and Hinrichsen take INMR on a brief visit through the production facility located
within Siemensstadt in Berlin. The plant is primarliy an assembly operation as the
various components are manufactured by Siemens’ partners or affiliates at different
locations. For example, zinc oxide elements are produced in Austria by a firm in which
Siemens was a founding partner but which is today independent. Hinrichsen stops
briefly and points out that the close co-operation with this supplier has resulted in
development of 100 mm diameter blocks, allowing Siemens to replace two columns of
70 mm blocks in HV arresters with only one column.
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January/Febuary 2000
Issue Preview » Companies in Transition » New Design of Polymeric…
One of the interesting developments now taking
place at Siemens relates to condition monitoring
of arresters utilizing temperature. Among other
applications, this type of system has been utilized
in a special HVDC application where it was
required to decrease the protection level for
expensive thyristor valves and therefore where
monitoring the arrester was deemed especially
important. Special sensors, which do not require
External monitoring box can receive data from up to
a power supply or leads and which have been
three antennas transmitting temperatures from special
developed by another Siemens division, are
sensors installed in arresters.
incorporated into the arrester housing. These sensors transmit information to a
separate, external monitoring unit using an antenna. Apparently, each antenna can be
used for up to five sensors and each monitoring box has the electronics to serve up to
three antennas. This way, a single box can be used to monitor one complete set of
three 500 kV arresters.
Says Hinrichsen stopping in the area where testing of
this development is underway, “we feel that leakage
current analysis is basically not a reliable method to
evaluate degradation or stress on an arrester. Since
ageing and energy absorbtion will both affect
temperature of the apparatus, monitoring this
parameter can be more valuable.”
“More and more stations today are remote-controlled,”
adds Fien “and this means remote-control for all
devices, including arresters. We are convinced that
monitoring temperature is better than relying on
conventional monitoring systems such as either surge
counters, which do not really tell you the effect of the
surges, or leakage current detectors.” According to
Hinrichsen, there is already a high interest in this
technology from both European and U.S.-based utilities
for application on 420 kV, 550 kV and 800kV networks.
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In-house mechanical test facility to verify
breaking loads of porcelain and composite
arrester housings.
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Downstairs in the plant is an area where accelerated ageing tests are performed on
zinc oxide blocks. Since ageing is influenced by the surrounding medium, such testing
is done under SF6 and CO2 environments. Continuous operating voltage along with a
temperature of 115· C is used to provide an acceleration factor whereby 1000 hours
of testing is equivalent to about 100 years of service.
Accelerated ageing tests to measure power loss of zinc
oxide blocks at 115° C and with continuous operating
voltage.
Stopping briefly at a display of HV arresters near
the plant’s entrance, Hinrichsen notes that many
of the silicone-housed units have accumulated
dust on their sheds. This makes him remark that
there is still a job to be done in terms of
educating substation maintenance personnel not
to clean such housings simply because they may
appear dirty. “I am convinced,” he says, “that
even here in Germany there are cases where
these arresters are being cleaned when they
should not be.”
Looking toward the future, Fien states that Siemens will continue to offer its
alternative arrester designs in parallel to one another. “Our philosophy for many
years,” he notes, “is that we do not want to restrict ourselves to only one technology
but rather to offer several. This makes it easier to have discussions with customers to
find the best solution for their specific needs. We did this during the transition from
silicone carbide to zinc oxide and it has proven to be the correct strategy. As far as
porcelain and composite housings, we will continue to offer both and now, within the
polymeric-housed arresters, we will have two alternative designs. Each will offer its
own different design and technical performance.”
INMR®
P.O. Box 95, Westmount (Montréal), Québec, Canada, H3Z 2T1
Telephone: (514) 939-9540 Telefax (514) 939-6151 Email:insunews@odyssee.net
Current Issue| Back Issues | Subscription Information | Index of Articles | Contact Information |
Guestbook | 2000 Buyer's Guide & Directory | 2000 Worldwide Directory of High Voltage & High
Power Laboratories | Insulator 2000 World Congress Barcelona Spain | International Symposium
on Modern Insulator Technology | Media Kit | Site Map
Copyright© 2000 INSULATOR NEWS & MARKET REPORT
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