Normally, the primary current ratings for phase current transformers are 10 A, 12.5 A, 15 A, 20 A, 25
A, 30 A, 40 A, 50 A, 60 A and 75 A as well as their decimal multiples, while the secondary current
ratings are 1 A and 5 A. Other, non-standard ratings can be directly connected as the scaling settings
are flexible and have large ranges. For example, the ring core current transformer ratings may vary.
Ring core current transformers are commonly used for sensitive earth fault protection and their rated
secondary may be as low as 0.2 A in some cases.
The following chapter is an example on how to set the scaling of the current measurements for the
selected current transformer and system load.
Example of CT scaling
The following gure presents how CTs are connected to the relay's measurement inputs. It also shows
example CT ratings and nominal current of the load.
Figure. 5.2.1. - 31. Connections.
The following table presents the initial data of the connection.
Table. 5.2.1. - 4. Initial data.
Phase current CT
- CT primary: 100 A
- CT secondary: 5 A
Ring core CT in Input I02
- I0CT primary: 10 A
- I0CT secondary: 1 A
Load (nominal)
36 A
- the phase currents are connected to the I01 residual via a Holmgren connection
- the starpoint of the phase current CT's secondary current is towards the line
AQ-E215
Instruction manual
Version: 2.01
© Arcteq Relays Ltd
34
Содержание AQ-E215
Страница 1: ...AQ E215 Energy management IED Instruction manual ...
Страница 4: ...206 11 Contact and reference information AQ E215 Instruction manual Version 2 01 3 Arcteq Relays Ltd ...
Страница 186: ...Figure 8 13 113 Device installation AQ E215 Instruction manual Version 2 01 185 Arcteq Relays Ltd ...
Страница 206: ... Pt100 1000 Balco500 Ni power module AQ E215 Instruction manual Version 2 01 205 Arcteq Relays Ltd ...