Excellence in Instrument Transformers
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Excellence in Instrument Transformers
The Trench Group
The Trench Group is well represented
throughout the world with
manufacturing plants in North America,
South America, Europe and Asia having
a combined expertise of more than 170 Trench® Austria GmbH Trench® China - Shenyang
years. A worldwide sales network ensures
efficient, knowledgeable communications
with our customers.
TRENCH: A specialized manufacturer Trench® Brasil Ltda Trench® China - Shanghai
of high voltage electrical equipment
dedicated to serving the electrical
industry world-wide through
engineering, service and commitment.
Many reasons exist to explain why power
companies, research institutes and Trench® Canada - Ajax Trench® France S.A.
electrical engineering companies in many
nations rely on superior technologies of
Trench. Our product line is based on in-
depth competence in development and
manufacturing. A highly significant fact
in this concept is the independence of Trench® Canada - Scarborough Trench® Germany GmbH
Trench in all of its key core competencies
including: insulation, windings,
capacitors, electronics and systems
engineering technologies. We develop
and master these key technologies in-
house, which provides a significant Trench® Canada - Scarborough Trench® Switzerland AG
quality factor and increases our ability to
solve customer problems.
Trench® Canada - Scarborough Trench® (UK) Limited
2
Was Formed by
Three Member Companies
In instrument transformers, All of these products are Our policies of design
the expertise, experience and characterized by high quality conservatism and quality
technology of each of the three standards, superior technical assurance are a direct result of
forming companies has been features and a first class price/ our commitment to meet or
brought together and focused on performance relationship. exceed these requirements.
technology specialists acting as a Competent customer service is
In our day-to-day business we
team for the global market: available worldwide.
endeavor to always focus on the
• the former Trench Electric Our customers have highest needs of our customers. We treat
focusing on capacitive products requirements regarding: our customers with fairness and
respect and our target is long-
• the former Haefely specializing • life expectancy
term partnership.
in oil-insulated inductive • reliability
instrument transformers •operational security.
• the former MWB focusing on
SF6-insulated inductive
instrument transformers.
Throughout the Trench
Group, excellence is built on a
foundation of:
• in-depth technical knowledge
and experienced people
• close business and technical
relationships built with our
customers over many years
• global service
• strong innovation and quality
assurance demands
• widely supported technology
base.
Our collective product
scope comprises instrument
transformers for metering,
protection and control on HV and
EHV systems:
• Current Transformers
• Voltage Transformers
• Combined Instrument Quality remains paramount for Trench.
Transformers All products are manufactured with
compliance to international
Quality Standard ISO 9001.
3
Instrument Transformer Technology
Metering, Protection
and Control
Electrical instrument transformers For the above applications,
transform high currents and the Trench Group supplies:
voltages to standardized low
and easily measurable values Current Transformers
which are isolated from the high 72.5 kV through 800 kV and
voltage. primary currents to 5000 A.
When used for metering pur- Inductive and Capacitive
poses, instrument transformers Voltage Transformers
provide voltage or current 72.5 kV through 800 kV.
signals which are very accurate
representations of their Combined Instrument
transmission line values in Transformers 72.5 kV through 800
both magnitude and phase. kV and rated primary currents up
These signals allow accurate to 4000 A.
determination of revenue billing.
Highest Metering Accuracy
When used for protection pur- Requirements Verified by:
poses, the instrument transformer
outputs must accurately represent • CCAC in Canada
their transmission line values •N ational Grid Company in
during both steady-state and England
transient conditions. These critical • EdF in France
signals provide the basis for • PTB in Germany
circuit breaker operation under • SEV in Switzerland
fault conditions and as such are
fundamental to network reliability Highest Protection
and security. Performance Requirements:
Instrument transformers used for In addition to both IEC and
network control supply important ANSI standard protection cores,
information as to the state of inductive current transformers
the operating conditions of the can be provided with TPS, TPX,
network. TPY and TPZ cores in accordance
with IEC standards, and Class X
cores in accordance with British
standards.
The requirements of many other
national standards are also fully
satisfied on request.
4
Reliability and Security
Reliability of an instrument Security, refers to the
transformer refers to its ability acceptability and consequences
to consistently satisfy prescribed of the instrument transformer
performance criteria over its failure mode in the event that it
expected useful lifetime under does fail, due either to reaching
specified operating conditions. the end of its expected service
life or a result of being subjected
to stresses in excess of those for
which it was designed.
The reliability and security
characteristics of an instrument
transformer are governed by
the electrical and insulation
design, the manufacturing and
processing technology used and
the specific physical arrangement.
The partial discharge
performance under in-service
conditions is a key determining
factor in the life expectancy
and long-term relibility of an
instrument transformer.
IEC Standards require a P.D. value
of less than 10 pC at 1,2 3 Umax.
Due to the demanding
requirements of today‘s HV and
EHV networks, the Trench Group
has elected to adopt even more
stringent internal requirements.
As such, Trench instrument
transformers typically perform
much better than required by
these standards.
5
The Reliability and Security of
Oil-immersed Instrument Transformers.
The reliability and security of Should arcing occur, due to relief points to rupture at very
Trench oil-insulated instrument damaged insulation, the best moderate pressures.
transformers is based on the protection against severe
following features: pressure build-up is guaranteed For the ultimate in security
• in-service experience spanning by the: inductive type oil-insulated
up to 50 year • very thin welded elastic housing instrument transformers can be
• in the event of internal • metal bellows for the oil equipped with a special additional
insulation failure, a secure expansion monitoring systems:
failure mode is achieved
through: Both the welded seam, which Gas Detection System GDS
connects the upper and lower
For Inductive Type portions of the head housing, The gas detection system GDS
and the metallic bellows are de- monitors the amount of gas
The formation of fibre bridges signed to act as pressure relief collected at a specific collection
in the free oil between high points in the event of severe tank located in the head of the
voltage and ground electrodes is internal pressure buildup. unit.
a known potential failure mode
of instrument transformers. In Since the unit has a normal For CVT‘s
the Trench design this failure internal oil pressure of
mode is eliminated through the approximately 1 bar absolute, it is Pressure relief is provided by a
use of a «barrier construction» possible to design these pressure bellows puncture pin and through
design in the free oil section. This the use of porcelain which is
approach consists of inserting sufficiently strong as to result
insulating barriers at strategic in any rapid pressure rise being
points through the free oil space, released through the seal plates
thereby preventing the formation at the ends of the porcelain
of fibre bridges. rather than via explosion of the
porcelain itself.
The behaviour of the instrument
transformer in the case of Upon request oil-immersed
overvoltage, e.g. being struck instrument transformers can
by lightning: A rupture of also be supplied with composite
the housing, in particular of insulators.
the hollow insulator with
built-in finely graded
capacitor bushing is
improbable because of
the overdimensioning
of the bushing and the
solid electrical connection
between the core housing and
the ground.
6
The Reliability and Security of
Gas-insulated Instrument Transformers
The reliability and security of Most reliable Insulation All the above features guarantee
Trench gas-insulated instrument Properties an operation period over many
transformers is based on: years without any control of the
SF6-gas is the main insulation insulation condition.
• 50 years experience as a medium between high voltage
manufacturer of instrument and ground potential. This gas, Full functional Security and
transformers covering epoxy- due to its excellent features, is a Monitoring
resin, oil-paper and finally gas- must for all GIS manufacturers of
insulated units high voltage equipment. The guaranteed SF6-leakage rate
is less than 1% per year.
• more than 10,000 gas-insulated A stable quality can be guaranteed
instrument transformers in by the use of SF6-gas acc. to ANSI/ The gas pressure can be checked
service under most different DIN and the fact that this inert at site or by means of a remote
environmental conditions gas shows no ageing even under control device, i. e. a densimeter
the highest electrical and thermal with contacts for remote control.
• an explosion-proof design stresses. The insulation properties In the case of loss of SF6-pressure,
providing maximum safety due remain unchanged throughout its the transformer still operates at
to the combination of SF6-gas lifetime. rated pressure.
with a composite insulator
Environmentally beneficial under
Explosion-proof Design most severe conditions
The present Trench gas-insulated SF6-gas is physiologically
instrument transformers are the absolutely safe. It bears no
result of the development of an ecologically toxic potential and
explosion-proof design, which its decomposition products have
many customers asked for. Gas- no endangering effects on the
insulation is particularly suitable environment, e.g. ground water
for this, as, in the event of an pollution.
internal flashover, the pressure
increase will be linear and hence This SF6-gas insulation
technically manageable. medium allows an easy waste
management of the transformers.
A controlled pressure relief
device at the head of the Furthermore the hydrophobic
transformer (rupture disc) features of the composite
eliminates unacceptable insulator result in a problem-free
mechanical stresses in the service even under salt-fog or
housing; i. e. only the polluted conditions.
rupture disc is released,
gas escapes, but the complete
transformer remains intact – no
explosion occurs.
7
8
9
Current Transformers
Oil-immersed Type
Features
• Head type design of low weight
and minimum oil volume
• excellent seismic performance as
a consequence of the optimized
design of flanges, porcelain and
their interconnection
• short, symmetrically arranged
low reactance bar-type primary
conductor permits higher short
circuit currents and avoids large
voltage drop across the primary
winding
• excellent control of internal
and external insulation stresses
through the use of a proprietary
finely graded bushing system
• hermetically sealed by stainless
steel metallic bellows
• uniformly distributed secondary
windings guarantee accurate
transformation at both rated
and high currents
• essentially unaffected by stray
external magnetic fields
• stable accuracy over a long
period of time
• exclusive use of corrosion
resistant materials
• Composite insulators available
on request
• 1:1 A current ratio possible.
10Current Transformer Gas-insulated
Features
• head type design
• explosion-proof design by the
compressible insulation medium
SF6-gas and rupture disc
• excellent seismic performance
due to the properties of the
composite insulator
• available for the full voltage
range 72.5 kV up to 800 kV and
full current range 100 A up to
4800 A
• low reactance bar type primary
providing optimal short-circuit
performance
• optimum field grading is
accomplished by a fine
condenser grading system
especially developed for this
application
• multiple-turn primaries for
small primary currents
• uniformly distributed secondary
windings guarantee accurate
transformation at both rated
and high currents
• stable accuracy over a long
period of time
• perfect transient performance
• exclusive use of corrosion
resistant materials
• core changes after assembly do
not require the destruction of
the high voltage insulation
11Inductive Voltage Transformer
Oil-immersed
Features
• Low weight and minimum oil
volume
• excellent seismic performance
as a consequence of optimized
designs of flanges, porcelain
and their interconnection
• excellent control of internal
and external insulation stresses
through the use of a proprietary
finely graded bushing system
• essentially unaffected by stray
external magnetic fields
• hermetically sealed stainless
steel metallic bellows for units
rated 123 kV and above
• stable accuracy over a long
period of time
• perfect transient performance
• suitable for line discharging
• exclusive use of corrosion-
resistant materials.
• Composite insulator available
on request
12Voltage Transformer
Gas-insulated
Features
• explosion-proof design by the
compressible insulation medium
SF6-gas and rupture disc
• excellent seismic performance
due to the properties of the
composite insulator
• available for the full voltage
range 72.5 kV up to 800 kV
• optimum field grading is
accomplished by a fine
condenser grading system
especially developed for this
application
• wide range ferroresonance free
design without the use of an
external damping device
(please ask for details)
• essentially unaffected by
external stray magnetic fields
• stable accuracy over a long
period of time
• suitable for line-discharging
• optimized high voltage coil
assures identical electric stresses
under both transient and steady
state conditions
• exclusive use of corrosion-
resistant materials
13Capacitor
Voltage Transformer
Features
• Capable of carrier coupling PLC • oil expansion by way of
signals to the network hermetically sealed stainless
steel bellows assures the
• optimized insulation system integrity of the insulation
design utilizing state-of-the- system over time
art processing techniques with
either mineral oil or synthetic • bellows puncture pin
insulating fluids provides for release of
internal pressure in the event
• stability of capacitance and of severe service conditions
accuracy over a long period of leading to internal discharges
time due to superior clamping
system design • extra high strength porcelains
provide both superior seismic
performance and the ability
to mount large line traps
directly on the CVT with
corresponding savings in
installed cost
• maintenance-free oil filled
cast aluminum basebox
• superior transient response
characteristics
• internal company routine
test and quality requirements
exceed those of international
standards with impulse tests
and partial discharge test
being performed on a routine
basis
• not subject to ferroresonance
oscillations with the network
or breaker capacitator
• high capacitance CVT‘s, when
installed in close proximity
to EHV circuit breakers, can
pro-vide enhanced circuit
breaker short line fault/TRV
performance.
14Electronic Voltage Measuring
System for HVDC
The Trench Group offers special
voltage transformers for HVDC
systems.
These units are primarly used
to control the HV valves of the
rectifiers or inverse rectifiers.
The measuring system consists
of an RC voltage divider which
provides inputs to a specially
designed electronic power
amplifier.
The High Voltage Divider can
be supplied either for outdoor
operation or for installation into
SF6 gas-insulated switchgear
(GIS).
The resulting system can
accurately transform voltages
within a defined burden range
with linear frequency response
up to approximately 10 kHz.
As such, the system is ideal
for measurement for dynamic
and transient phenomena and
harmonics associated with HVDC
systems.
15Combined Instrument Transformer
Oil-immersed
Features
• Low weight and minimum oil
volume
• short symmetrically arranged
low reactance bar-type primary
conductor permits higher short
circuit currents and avoids large
voltage drop across primary
winding
• excellent control of internal
and external insulation stresses
through the use of a proprietary
finely graded bushing system
• excellent seismic capability as
a consequence of optimized
design of flanges, porcelain and
their interconnection
• hermetically sealed by stainless
steel metallic bellows
• only one foundation required in
the switchyard as a consequence
of combining the voltage and
current sensing functions in one
transformer
• uniformly distributed secondary
windings guarantee accurate
transformation at both rated
and high current
• essentially unaffected by stray
external magnetic fields
• stable accuracy over a long
period of time
• perfect transient performance
• suitable for line discharging
• exclusive use of corrosion-
resistant materials.
• composite insulators available
on request
16Combined Transformer
Gas-insulated
Features
• head type design with voltage
transformer section located on
top of the current transformer
• low weight and compact SF6-
design
• explosion-proof design by the
compressible insulation medium
SF6-gas and rupture disc
• excellent seismic performance
due to the properties of the
composite insulator
• the single-section high voltage
coil (not cascaded) of the
voltage transformer section
enables a product range
for combined instrument
transformers up to 800 kV
• optimum field grading is
accomplished by a fine
condenser grading system
especially developed for this
application
• wide range ferroresonance free
design without the use of an
external damping device (please
ask for details)
• low reactance type primary
conductor allows for high short-
circuit currents and covers all
core standards
• less foundation space required
compared to the use of
individual current transformers
and voltage transformers
• suitable for line-discharging
• essentially unaffected by
external stray magnetic fields
• exclusive use of corrosion-
resistant materials
17Instrument Transformer
for GIS Switchgear
Inductive Type RC Type
• in addition to the measurement • guaranteed SF6-leakage rate of • RC divider for voltage
of the voltages and currents less than 1% per year measurements
best discharge capabilities for
• equipped with pressure relief • conform to microprocessor
HV-lines
disc and deflection device based secondary technology
• custom-designed instrument
• all components are designed • ferresonance free
transformers for each specific
and tested for mechanical stress
application and extended • able to sustend voltage test on
to withstand up to at least 20 g
function designs comply with site
dimensional restrictions, flange • accuracy classes in accordance to
DIN VDE 0414, IEC 60044, ANSI: • 1 phase or 3 phase system
sizes and insulator requirements
IEEE C57.13, AS 1243 (other • significant size and weight
• standard designs for single- and
standards or classes on request) reduction
three-phase units
• shock indicators warning
• meets all national and
against inadmissible
international standards with
acceleration during
regard to pressure vessel codes
transportation
• prevention of occurrence of
stable ferroresonances by Voltage transducer 145 kV
series RCT (active part) for HV GIS
integrated ferroresonance
suppression
• shielded against transient
overvoltages in accordance with
IEC standards. Special additional
shielding is available.
18LoPo
The Low Power Transducers
The low power current and voltage transducers can
be used for a wide range of medium and high voltage
applications where they replace the conventional
measuring transformers for measurement and
protection purposes.
• The Voltage Transducers are
based on resistive as well as
resistive-capacitive dividers
• The Current Transducers are
based on an iron core or an
air core design and provide a
secondary voltage which
represents the primary current
• Standard cables and connectors; Voltage transducer principle Voltage transducer 24 kV Voltage transducer 36 kV
diagram series LPVT series LPVTG for MV metalclad
twisted pair and double switchgears
shielded cable
• Connection capability for
multiple protection and
measuring devices
• Metalclad housing ensuring
operator safety
• Immune to all methods of
on-line switchgear and cable
testing Current transducer principle diagram, iron core design Current transducer for MV
applications,
• Current Transducers provide a series LPCT and LPLS
linear transmission up to short
circuit current
Advantages
• Completely EMC shielded,
immune to RFI/EMI • System conforms to low power digital microprocessor based
technology for protection and metering
• Simple assembly with compact size and low weight
• No secondary circuit problems; Voltage Transducers are short circuit
proof, Current Transducers can have an open secondary
• Voltage Transducers are ferroresonance free
• Environment friendly (no oil)
19Trench Facilities
Trench® Austria GmbH Trench® Limited
Paschinger Strasse 49 Instrument Transformer Division
Postfach 13 390 Midwest Road
A-4060 Linz-Leonding Scarborough, Ontario
Austria Canada M1P 3B5
Phone: 43-732-6793-0 Phone: 416-751-8570
Fax: 43-732-671341 Fax: 416-751-6952
Trench® Brasil Ltda Trench® Limited
Via Expressa de Contagem, 2685 Power Line Carrier Division
Contagem, Minas Gerais 815 Middlefield Road, Unit 6A
CEP 32370-485 Scarborough, Ontario
Brazil Canada M1V 2P9
Phone: 55-31-3391-5959 Phone: 416-291-8544
Fax: 55-31-3391-1828 Fax: 416-291-5581
Trench® China Trench® France S.A.
MWB (Shanghai) Co., Ltd. 16, Rue du Général Cassagnou
No. 3658, Jiancheng Road B.P. 70 F-68 302
Minhang, Shanghai St. Louis, Cedex, France
Peoples Republic of China Phone: 33-3 89-70-2323
200245 Fax: 33-3 89-67-2663
Phone: 86-21-54720088
Fax: 86-21-54723118 Trench® Germany GmbH
Nürnberger Strasse 199
Trench® Shenyang D-96050 Bamberg, Germany
The Trench Group is your Trench High Voltage Phone: 49-951-1803-0
Products Ltd., Shenyang Fax: 49-951-1803-224
Dao Yi Economic Development Zone
partner of choice for electrical Shenyang 110136 Trench® Switzerland AG
Peoples Republic of China Lehenmattstrasse 353
Phone: 86-24-89725308 CH-4028
power transmission and Fax: 86-24-89737200 Basel, Switzerland
Phone: 41-61-315-51-11
Trench® Limited Fax: 41-61-315-59-00
distribution solutions today; Bushing Division
432 Monarch Avenue Trench® (UK) Limited
and for the development of Ajax, Ontario South Drive
Canada L1S 2G7 Hebburn, Tyne & Wear
Phone: 905-426-2665 NE 31 1 UW
your new technology solutions Fax: 905-426-2671 Phone: 44-191-483-4711
Fax: 44-191-430-0633
Trench® Limited
of tomorrow. Coil Product Division Trench® Italia
71 Maybrook Drive Strada Curagnata
Scarborough, Ontario 37 Bragno-Cairo
Canada M1V 4B6 17014, Italy
Phone: 416-298-8108 Phone: 39-019-5161-111
Fax: 416-298-2209 Fax: 39-019-5161-401
www.trenchgroup.com
E 210.10
Subject to change without notice (07.2010)
Printed in Canada.
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