contain current sample values, time information, trip signals, block signals, alarm
signals and 8 binary signals, which can be used for any purpose. Each IED can
have a maximum of two communication channels.
On a two terminal line there is a need for one communication channel provided that
there is only one CT at each line end (see Figure
IED
Protected zone
IEC05000437-2-en.vsdx
IED
IEC05000437 V2 EN-US
Figure 34:
Two-terminal line
In case of 1½ breaker arrangements or ring buses, a line end has two CTs (see
Figure
).
IED
Protected zone
IED
IEC05000438-2-en.vsdx
IEC05000438 V2 EN-US
Figure 35:
Two-terminal line with 1½ breaker
, both local CTs on the left side are treated as separate
ends by the line differential protection function.
Current values from two CTs in double breakers, ring main or 1½ breaker system
ends with dual breaker arrangements need to be sent to the remote end. As a 64
kbit/s LDCM only has capacity for one three-phase current (duplex), this implies
that two communication channels are needed at both ends, and this is also the
normal solution.
To reduce the number of communication channels needed, it is also possible to sum
up the two local currents before sending by using a software in the IED. However,
this is not recommended as it reduces information about bias currents. Bias current
is considered the greatest phase current at any line end, and it is common for all
three phases. When sending full information from both local CTs to the remote
end, the principle works, but when the two local currents are summed up before
1MRK 505 393-UEN B
Section 6
Differential protection
Line differential protection RED650 2.2 IEC
83
Application manual
Summary of Contents for RED650
Page 1: ...RELION 650 SERIES Line differential protection RED650 Version 2 2 Application manual ...
Page 2: ......
Page 22: ...16 ...
Page 32: ...26 ...
Page 82: ...76 ...
Page 112: ...106 ...
Page 152: ...146 ...
Page 208: ...202 ...
Page 214: ...208 ...
Page 282: ...276 ...
Page 356: ...350 ...
Page 404: ...398 ...
Page 408: ...402 ...
Page 442: ...436 ...
Page 452: ...446 ...
Page 453: ...447 ...