Seg WIC1-W3 User Manual

SEG Electronics GmbH Technical Manual WIC1
18 DOK-TD-WIC1E, Rev. M
4.3 CTs for the WIC1
There are different wide-range CTs for the protection system WIC1. (See also 8.3 “Order form”.)
CT Type
(Order Code)
Rated CT
current IS
Max. measurable
Short-circuit Current
Thermal Withstand
IS
min
IS
max
(20IS
max
= 70IS
min
)
Primary current max.:
WIC1WE1AS1
8 A
… 28 A
560 A
20 kA for 3 seconds,
and
25 kA for 1 second
WIC1W2AS1
16 A
… 56 A
1120 A
WIC1WE2AS1
16 A
… 56 A
1120 A
WIC1W3AS1
32 A
… 112 A
2240 A
WIC1W4AS1
64 A
… 224 A
4480 A
WIC1W5AS1
128 A
… 448 A
8960 A
WIC1W6AS1
256 A
… 896 A
17920 A
The optimum CT is selected depending on the rated primary power and voltage of the system. A detailed
discussion can be found in chapter 5.11 “Selection of the CT transformation voltage ratio”.
The protection relay can be set to the respective operating current of the switchboard by parameter Is. Reference
on the calculation of the protective setting values resulting from this is made in chapter 5.9 “Description of the
Application”.
Current transformer WIC1WE1AS1, WIC1WE2AS1
In case of small values of the primary currents there are special “E”-labeled CTs available that feature a mixed core
based on MU metal and offer an optimized characteristics of transmission: WIC1WE1AS1, WIC1WE2AS1.
It is typical of self-powered protection relays such as the WIC1 that small primary currents cause a non-linear
transmission characteristic of the relay. The “E” CTs improve the accuracy of the whole system if the primary
current values are less than 20 A (WIC1WE2AS1), or less than 10 A (WIC1WE1AS1).
A worse accuracy can often be accepted for an application without earth current protection so that the
WIC1W2AS1 (i.e. without „E“) represents an inexpensive alternative.
(For the lowest range 8 – 28 A, however, SEG Electronics GmbH decided for quality reasons to not offer such an
alternative.)
If a higher accuracy is needed, or in case of a required earth current protection element it is recommended to
always use an “E”-type CT (i.e. prefer WIC1WE2AS1 over WIC1W2AS1), because in the lower operation range
this CT type is more precise than the WIC1W2AS1.

Seg WIC1-W3 Specifications

General

Brand	Seg
Model	WIC1-W3
Category	Relays
Language	English