Medium Voltage Product. KOFA Indoor current transformers

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1 Medium Voltage Product KOFA Indoor current transformers

2 Technical parameters Rated frequency Rated secondary current Rated burdens Accuracy class Mechanical strength of primary terminals Standards other data will be offered on request Value 0; 60 Hz (.) A.; ; 7.; ; ; ; ; VA ; 0.; ; P; P kn IEC, BS, ANSI,... Description The primary winding, core and secondary winding of the transformer are encapsulated in cast-resin. cooling of the transformers as well as the required creepage & free air distance to earth and between phases. The manufacturer should be consulted in such cases. The problem with creepage and free air distance can be solved by choosing a transformer type designed for higher voltages. The requirement for impulse test voltage (BIL-level) should preferably NOT be higher than normal for the service voltage used as this may have a negative effect on the available output from the secondaries. Isulation levels for KOFA models /8/7 kv 7./8/9 kv 4()/0/ kv Secondary conductors The fixing screws in the light alloy base are positioned within easy reach also from above. The conduit used for the secondary conductors can be fixed into a U-shape slot entry in the secondary terminal box. This design obviates the drawing of the secondary conductor through an entrance hole into the terminal box.when specified on order the box can be provided with a threaded entry for cable termination accessories. One... sq. mm or two...6 sq. mm (in case of three core transformer one...6 sq. mm ) conductors can be directly connected to the secondary terminals. The terminal cover is sealable. Degree of protection by enclosure is IP. Primary terminals M size screws are used in primary terminals. Primary connection can be changed without removing the already fitted primary conductors. The transformer specification can in such a case be for example: Type KOFA 4 D Service voltage 7. kv Test voltages 8 kv min./9 kv impulse The normal transformer type KOFA 4 D would have been suitable if used below 000 m. Permissable torques for screw connections M max. Nm min.8 Nm M8 max Nm min 6 Nm M max 70 Nm min 6 Nm Environment and altitudes The KOFA transformers are made for indoor mounting. IEC recommandation gives requirement for ambient temperature between - C and +40 C. The transformers, however, may be used at a temperature as low as -40 C. The transformers must be protected against unusually heavy deposits of dust or similar pollution, as well as against direct sunshine. In mountaineous areas the height above sea level may be higher than the height specified in the IEC standards as design criteria ( 000 m). The thin air at high altitudes affects the Preferred transformers for ; 7. and 4 kv Technical data and ordering information Description for preferred transformers A limited selection of the KOFA-type current transformers are available as preferred types, which gives two advantages:. Having factory documentation and material ready for the most frequent ratings thus offering short delivery times for urgent needs.. Simplifying the choice and ordering by giving each standard c.t. a specific order code. On ordering transformers according to the table below please give only the order code, observing the voltage code. Available preferred current transformers: Type: KOFA D for kv KOFA 4 D for 4 kv Secondary current: A Number of cores: Weight: 7 and 9 kg Standards: International standard IEC 44- Normally not labelled: R ct (winding resistance at 7 C), U k (knee-point voltage) and I o (exciting current). Example how to order: Requirements: 6.6 kv, stand. IEC 44- I th /I dyn = -/-0 ka 0-0// A Core : VA cl. 0., Fs = Core : VA cl. P Frequency: 0Hz Gives the ordering code: KOFA D - L0 KOFA Indoor current transformers

3 PREFERRED CURRENT TRANSFORMERS, 0 Hz Commercial code Rated primary current Short-circuit strength Core S Core S Short-time current, s Surge current Class 0. [A] [ka] r.m.s. [ka] peak Ω VA F s R ct Class P R ct Ω U k I om kv 4 kv 4 KOFA _ D-H0 KOFA _ D-H0 KOFA _ D-J0 KOFA _ D-J0 KOFA _ D-L0 KOFA _ D-L0 KOFA _ D-N0 KOFA _ D-N0 KOFA _ D-R0 KOFA _ D-R KOFA _ D-S KOFA _ D-T0 Selection of custom designed transformers Technical data and ordering information 0 Hz (60 Hz) Highest system voltage The transformer design is for kv and 7. kv types KOFA _ and for 4 kv types KOFA 4_. Short circuit strength, primary current, core selection symbol The primary table on page 6 shows the available short circuit strengths and rated primary currents. The table also gives the core selection symbol. The larger the chosen core symbol, the smaller the cores and transformers become in size. In case of transformers with two primary connections the table is applicable for the lower rated current. At the double rated current the thermal and dynamic strengths are also doubled. The cores The core selection tables on page 7 and 8 show how the core size is determined by the chosen core symbol, burden and accuracy. Only the most common accuracy classes and burdens are indicated in the table, the secondary current being A. The core size obtained from the table, decides the size of transformer frame lenghtwise. For both and 4 kv are three different transformer lenghts available: types KOFA _, KOFA _ and KOFA _ which can accommondate number of cores as shown on page 6. Cantilever strength: kn Frequency The transformers can be manufactured for different frequencies. The tables here are made for 0 Hz. The same tables may be used also for 60 Hz taking into account that the FSvalue of measuring cores will be % higher at 60 Hz. KOFA Indoor current transformers

4 Custom designed transformers Primary and type selection tables Selection tables Primary table, 7. and 4 kv I th/ka s I dyn/ka peak Connections for two primary currents Single ratio I th/ka s I dyn/ka peak Rated primary current I pn/a Core selection symbol Rated primary current I pn/a () 00 () (only kv) Max. continuous current () at kv x 00 A () at 4 kv. x 000 A () and ( ) only with A secondary current Type selection, 7. and 4 kv Transformers for two primary current connections Core size total No. of cores 4, 7. kv 4 k V Type Weight Type Weight Core size total No. of cores K O F A kg K O F A kg B D B D F B D F,...6, , B 4 D 4 B 4 D 4 F 4 B 4 D 4 F 4 9 Single ratio transformers () A C E,... 4 A 4 C 4 E 4 () for primary currents 000 A and 00 A 4 KOFA Indoor current transformers

5 KOFA Indoor current transformers Custom designed transformers Core selection table, 7. and 4 kv Selection tables Rated burden. VA VA 7. VA VA VA VA VA VA Selection Class Size Fs < Size Fs < Size Fs < Size Fs < Size Fs < Size Fs < Size Fs < Size Fs < P P P P P P P P P P P P P P P P P P P P P P

6 Custom designed transformers Core selection table, 7. and 4 kv Selection tables Rated burden. VA VA 7. VA VA VA VA VA VA Selection Class Size Fs < Size Fs < Size Fs < Size Fs < Size Fs < Size Fs < Size Fs < Size Fs < P P 0. P P P P P P P P P P P P P P P P P P P P P P KOFA Indoor current transformers

7 Rated burden. VA VA 7. VA VA VA VA VA VA Selection Class Size Fs < Size Fs < Size Fs < Size Fs < Size Fs < Size Fs < Size Fs < Size Fs < 0 0. P P P P 0. P P P P Example Requirements: 6.6 kv 0// A I th ( sec) = ka, I dyn = ka Core : VA, class 0. Core : VA, class P. The primary table shows that a transformer having I pn = 0-0 A, I th = - ka and I dyn = -60 ka will meet the set requirements for I th and I dyn.. Hence the core selection symbol at 0-0 A rated current will be. The core sizes are obtained from the core selection table which for core symbol are:. Core : VA, class 0. Core : VA, class P Total 76 (P acc. the table gives better accuracy than P) 4. kv transformer, type KOFA, will be used at 6.6 kv. The type selection table gives type KOFA D for the transformer size. If the transformer is later connected to a ratio 0// A the corresponding short circuit strengths are I th = ka and I dyn = 60 ka. It is not advisable to choose unnecessarily high values for I th (and I dyn ). The higher short circuit strength decreases the available burden and increases transformer price. KOFA Indoor current transformers 7

8 Dimensional Drawings KOFA A, C, E A M KOFA A, C, E KOFA 4 A, C, E A [mm] KOFA Indoor current transformers

9 KOFA B, D, F 60 A 76 B C D E E E M 40 M8 6 4 KOFA B, D KOFA KOFA B, D, F B, D, F KOFA 4 B, D KOFA 4 KOFA 4 B, D, F B, D, F A [mm] B [mm] C [mm] 4 4 D [mm] E [mm] KOFA Indoor current transformers 9

10 Contact us ABB s.r.o. EPMV Brno Videnska 7, 9 00 Brno, Czech Republic Tel.: Fax: info.ejf@cz.abb.com VLC000 Rev, en 7, The data and illustrations are not binding. We reserve the right to make changes without notice in the course of technical development of the product. Copyright 6 ABB. All rights reserved.