Presco AG CT-N1K0 User manual
Presco AG
Zürcherstrasse 70 -CH 8104 Weiningen Tel. + 41 44 750 63 63 Fax + 41 44 750 63 66
Internet : www.prescoag.com
Ma_CT1000_englisch1.DOC/ PO/ 10.07.2006 Page 1 of 6
Standard Current Transformer
up to 1000 A
Type CT-N1K0
Instruction Manual
Table of contents
1 Safety precautions
1.1 Safety
1.2 Safety precautions
1.3 Impaired Safety Precautions
2. Introduction
2.1 Function Principle
3. Technical Data
4. Operation
4.1 Connections
5. Secondary connection
6. Servicing
Presco AG
Ma_CT1000_englisch1.DOC/ PO/ 10.07.2006 Page 2 of 6
1 Safety precautions
1.1 Safety
The instrument described in this manual is designed to be used by properly trained per-
sonnel only. Adjustment, maintenance and repair of the exposed equipment should be
carried out only by qualified personnel aware of the hazards involved.
1.2 Safety precautions
For correct and safe use of this instrument it is essential that both operation and service
personnel follow generally accepted safety procedures in addition to the safety precau-
tions specified in the manual. Specific warning and caution statements, where they apply,
will be found throughout the manual. Safety is the responsibility of the user.
Warning!
The Instrument is an electronic system foreseen and de-
signed for low voltage operation. The whole equipment works
in high voltage environment and therefore all instructions and
precautions which apply for such operations have to be con-
sidered working with the measuring instrument.
1.3 Impaired safety precautions
Whenever it is likely that safety protection has been impaired, the instrument must be
made inoperative and be secured against any unintended operation. Safety protection is
likely to be impaired if, for example, the instrument fails to perform the intended meas-
urements or shows visible damage.
Presco AG
Ma_CT1000_englisch1.DOC/ PO/ 10.07.2006 Page 3 of 6
2. Introduction
2.1 Function Principle
The unit is made from a magnetic current transformer/comparator and an electronic com-
pensation unit:
The primary current flows in the winding Np and magnetizes all the three cores:
Qw Working core
Qk Compensation core
Qi Indicator core
The secondary working winding (Ns) sends a current to the Burden of the transformer. The
magnetizing effect of the secondary current is subtracted from the magnetizing of primary.
The Ni "Indicator winding" detects a voltage proportional to the difference of magnetizing and
with the high gain amplifier A0 sends a compensating current to the compensating winding
Nk.
This regulation loop trends to reduce the overall magnetizing in the cores Nk and Ni and be-
cause the Ik is fed to the output, the overall input current makes a "zero flux" CT. This "zero
flux" leads to very low errors.
Working Core
Compensation Core
Indicator Core
Primary Winding Np
Working secondary winding,Ns
Compensation winding, Nk
Indicator winding,Ni
Aw
Bw
m
w
Ak, Bk, k
m
Ai
Bi
m
i
Ip
Is Rs
Np
Ns
Nk
Ni
Rk
Ik
Ui
UA
A0
f
0
ZB
Q
w
Qk
Qi
Bw
Bk
Bi
I
B
U
B
Presco AG
Ma_CT1000_englisch1.DOC/ PO/ 10.07.2006 Page 4 of 6
3. Technical Data
3.1. Specification under Reference Conditions
Nominal primary currents (IN):) 1'000, 500, 250, 125, 100, 50, 25, 12.5, 10, 5 A
Nominal Secondary current 5 A
Rated Burden 5 VA
Working range 1 ... 200 % of nominal current
Frequency 50 /60 Hz
Uncertainty of ratio 0.001 %
Uncertainty of phase 0.05 Min.
Overload protection with indication
Mains 230 V 50 / 60 Hz
Dimensions T 330 x B 490 x H 610 mm
Hole diameter 40 mm (for 1'000 A range)
Weight approx. 30 kg
Reference Conditions
Temperature 23oC ± 2oC
Humidity 45 ... 75 %
Air Pressure 101.3 kPa
Rated range of use
according to Standard IEC 359
Temperature 5oC ... 40oC
Humidity, not condensing 10 ... 90 %
Air Pressure 70 ... 106 kPa
Presco AG
Ma_CT1000_englisch1.DOC/ PO/ 10.07.2006 Page 5 of 6
4 Operation
4.1 Connections
Legend:
1. "L1/5A" Primary 5A
2. "L2/10A" Primary 10A
3. "L3/12.5 A" Primary 12.5A
4. "L4/25A" Primary 25A
5. "L5/50A" Primary 50A
6. "L6/100A" Primary 100A
7. "L7/125A" Primary 125A
8. "L8/250A" Primary 250A
9. "L9/500A" Primary 500A
10. "K" Common Terminal of Primary
11. Trough hole for 1000A
12. "l/5A" l terminal of Secondary (5A): proposed as grounded terminal.
13. "k/5A" k terminal of Secondary (5A)
14. Ground connection from line
15. Guard connection: Screen of the CT. Must be grounded.
16. Power ON light
17. Overload lamp: If green = no overload. If red= overload.
18. Power line connector and switch
1
2
3456
7
8
9
10 11 12
13
14
15
16
17
18
Presco AG
Ma_CT1000_englisch1.DOC/ PO/ 10.07.2006 Page 6 of 6
5. Secondary Connection
Connect secondary to the CT testing instrument using min. 6.5 mm2cables.
The total burden on the Standard CT must not exceed 5 VA!
6. Servicing
Repair work and maintenance can only be done by qualified personnel of Presco AG. In
case of problems please contact the representative which delivered the instrument or
Presco AG directly.
Table of contents
