Current Transformers

Type IOSK

Introduction

Trench is a recognized world leader in thedesign and manufacture of high voltageequipment for application on electric utilityand high energy industrial systems. As partof Trench's product scope, the company produces a diversified range of Instrument

Transformers which are installed on69-800 kV electrical systems. Instru-ment Transformers include: Voltage(Potential) Transformers (both induc-tive and capacitive type), CurrentTransformers and Combined Instrument Transformers (voltage and current transformer in one unit).

Current Transformers must converthigh transmission line currents (up to5000 A) to standardized low and ea-sily measurable values, which will beused for metering, protection andcontrol of the high voltage system.As such, the need for accurate andreliable current transformation is es-sential.

This brochure will detail the featuresand characteristics of Trench TypeIOSK Current Transformers. Pleaserefer to Trench brochure E210 for ad-ditional general information concer-ning high voltage Instrument Trans-formers.

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Current Transformers

Fig. 1Type IOSK

Current Transformer

3

• highly refined and processedoil/paper insulation system

• Head type design of low weightand minimum oil volume

• use of high quality mineral oil,PCB free, biological decomposi-tion

• excellent seismic performance as a consequence of optimizeddesign of flanges, porcelain andtheir interconnection

• short, symmetrically arrangedlow reactance bar-type primaryconductor permits higher shortcircuit currents and avoids largevoltage drop across the primarywinding

• excellent control of internal andexternal insulation stressesthrough the use of a proprietaryfinely graded bushing system

• hermetically sealed by stainlesssteel metallic bellows

• welded housing sealed withoutscrews

• uniformly distributed secondarywindings guarantee accuratetransformation at both rated andhigh currents

Features

• essentially unaffected by strayexternal magnetic fields

• stable accuracy over a long period of time

• exclusive use of corrosion resistant materials

• explosion resistant by:

- insulating system with high reliability

- fine graded bushing- weakpoint in the aluminium

headcasting and the metallicbellows serving as pressure release device

• 1:1 A current ratio possible

• Successful field experience sincethe manufacture of the first current instrument transformerin 1924

• maintenance free during a longlifetime of more than 30 years

• composite insulators available onrequest

• Meet all IEC and ANSI meteringand protection classes,including special core classesTPS, TPX, TPY and TPZ(other standards on request)

• Rated primary currents upto 5000 A

• Primary reconnection available

• Rated secondary current1 A, 2 A or 5 A

• Rated short circuit withstandup to 200 kA peak

• Trench Management Systemhas been certified to ISO 9001,ISO 14001 and OHSAS 18001standards

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Construction

Trench type IOSK Current Transfor-mers are defined as "head type"Current Transformers. These CT'sare designed and constructed withthe well proven, highly reliable,oil/paper insulation system. Eachporcelain housed, hermeticallysealed Current Transformer isequipped with stainless steel ex-pansion bellows, calibrated to theinternal oil volume and extremesin ambient and operating temper-atures.

Customer specifications, such asapplication (metering or protect-ion), number of cores, ratings, etc.have a direct bearing on the sizeof the "head" or core housing foreach Current Transformer. For thisreason, the type IOSK is producedwith different size heads, Trenchwill recommend the optimum design based on each individualcustomer specification.

Standard Equipment

• Aluminum flat pad primary terminal and ground terminal

• Lifting lugs

• Bellows position indicator

• Oil filling port

• Oil drain valve

• Secondary terminal box with removable gland plate

Optional Equipment

• Stud type primary terminal

• Primary or ground cable connector

• Anti-corona rings

• Capacitance tap for measure-ment of voltage or tan delta ofbushing

• Gas Detection System (contactTrench for additional details)

• Terminal box heater

• Composite Insulators

Fig.2IOSK 245 Current Transformers

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Fig.3Electrical and mechanical

design details

1

1 Primary terminal 2 Metallic expansion bellows3 Oil filling screw4 Porcelain insulator5 Secondary terminal box6 Secondary terminals7 Oil drain valve8 Grounding terminal9 Gland plate10 Lifting lugs11 Bellows indicator12 High voltage insulation13 Secondary winding

and cores14 Primary winding15 Transformer head

(aluminum)

Without primary reconnection Primary reconnection 1:2

Primary reconnection 1:2:4 Secondary reconnection

1

22

33

4

4

5 56

67

78

89

9

1010

1111

12

1213

13

14 14

15

15

72.5 - 170 kV 245 - 550 kV

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Oil/paper-insulated Current Transformers

Electrical and Mechanical Data (1)

Type Max.continuous Test voltage Impulse Switching Min. Standardoperating voltage 50/60 Hz, withstand impulse sparking creepage

1 min. test voltage test voltage distance distancephase to phase dry/wet full wave 250/2500 µs

1.2/50 µs wetkV kV kV kV mm mm

IOSK 72.5 72.5 140 325 – 700 1815IOSK 123 123 230 550 – 1200 3815

IOSK 145 145 275 650 – 1200 3815

IOSK 170 170 325 750 – 1400 4495

IOSK 245 245 395 950 – 2200 6300

IOSK 245 245 460 1050 – 2200 6300

IOSK 300 300 460 1050 850 2200 6300

IOSK 362 362 570 1300 950 2650 9955

IOSK 420 420 630 1425 1050 3200 115501175 38001050 3200

IOSK 420 420 680 1550 1175 3800 115501300 42001175 3800

IOSK 550 550 680 1550 1175 3800 15125

1300 4200Notes:(1) Other ratings available on request

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Net weight Dimension Weight ofapprox. oil

h1 h2

Fig kg m mm kg

A 160 1630 1215 31A 200 2155 1715 35B 380 2400 1825 70A 200 2155 1715 35B 380 2400 1825 70A 220 2355 1915 44B 390 2600 2025 79B 470 3545 2970 79C 700 3745 3080 158B 470 3545 2970 79C 700 3745 3080 158B 470 3545 2970 79C 700 3745 3080 158C 900 4270 3600 184D 1600 4570 3720 350C 1000 4920 4150 245C 1400 5515 4745 315D 1700 5240 4270 411C 1400 5515 4745 315C 1600 5915 5145 380D 2100 5840 4870 438C 1400 5515 4745 315D 2100 5990 5020 438D 2300 6390 5420 505

� 360 � 450 � 450 � 600

Fig. A Fig.B Fig. C Fig. D

h2 h1 h2 h1 h2 h1 h2 h1

Trench® Austria GmbHPaschinger Strasse 49Postfach 13A-4060 Linz-LeondingAustriaPhone: 43-732-6793-0Fax: 43-732-671341

Trench® Brasil LtdaVia Expressa de Contagem, 2685Contagem, Minas GeraisCEP 32370-485BrazilPhone: 55-31-3391-5959Fax: 55-31-3391-1828

Trench® ChinaMWB (Shanghai) Co., Ltd.No. 3658, Jiancheng RoadMinhang, ShanghaiPeoples Republic of China200245Phone: 86-21-54720088Fax: 86-21-54723118

Trench® High Voltage Products Ltd., ShenyangNo. 2 Zhengliang Er. RoadJing Shen Xi San StreetDao Yi Economic Development ZoneShenyang 110136 P.R. ChinaPhone: 86-24-89722688Fax: 86-24-89737200

Trench® LimitedBushing Division432 Monarch AvenueAjax, OntarioCanada L1S 2G7Phone: 905-426-2665Fax: 905-426-2671

Trench® LimitedCoil Product Division71 Maybrook DriveScarborough, OntarioCanada M1V 4B6Phone: 416-298-8108Fax: 416-298-2209

Trench® LimitedInstrument Transformer Division390 Midwest RoadScarborough, OntarioCanada M1P 3B5Phone: 416-751-8570Fax: 416-751-6952

Trench® LimitedPower Line Carrier Division815 Middlefield Road, Unit 6AScarborough, OntarioCanada M1V 2P9Phone: 416-291-8544Fax: 416-291-5581

Trench® France S.A.16, Rue du Général CassagnouB.P. 70 F-68 302St. Louis, CedexFrancePhone: 33-3 89-70-2323Fax: 33-3 89-67-2663

Trench® Germany GmbHNürnberger Strasse 199D-96050 BambergGermanyPhone: 49-951-1803-0Fax: 49-951-1803-224

Trench® Switzerland AGLehenmattstrasse 353CH-4028BaselSwitzerlandPhone: 41-61-315-51-11Fax: 41-61-315-59-00

Trench® (UK) LimitedSouth DriveHebburnTyne & WearNE 31 1 UWPhone: 44-191-483-4711Fax: 44-191-430-0633

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The Trench Group is your

partner of choice for electrical

power transmission and

distribution solutions today;

and for the development of

your new technology solutions

of tomorrow.

E 217.11Subject to change without notice (05.2006)Printed in Canada.