2.1 General
39
7SD5 Manual
C53000-G1176-C169-1
Differential
Protection
The differential protection and the distance protection can each be configured as the
main protection function.
If the differential protection is the main protection function of the device,
DIFF.PROTECTION
(address
112
) is set to
Enabled
. This also implies the supple-
mentary functions of the differential protection such as breaker intertrip.
For the transmission of the protection signals to one (or two) device(s) each device is
equipped with one or two protection data interfaces (order option). The assignment of
the protection data interfaces is essential for the line protection system, i.e. the inter-
action of the devices at the ends of the protected object. Enable protection data inter-
face 1
P. INTERFACE 1
in address
145
, and protection data interface 2 (if available)
P. INTERFACE 2
in address
146
, if you want to use them. At least one protection
data interface at the is required to make use of the differential protection function. A
protected object with two ends requires at least one protection data interface in each
device. If there are more ends, it must be guaranteed that all devices that belong to-
gether are interconnected directly or indirectly (via other devices). Section 2.2.1 Pro-
tection Data Topology provides more information.
The number of relays (address
147
NUMBER OF RELAY
) must be equal to the number
of measuring locations at the ends of the protected object. Please observe that only
current transformer sets that limit the protected object are counted. The line in Figure
2-1, for instance, has three ends and three devices. It is limited by three current trans-
former sets. Two devices would normally be sufficient if current transformers 1 and 2
are connected in parallel at the secondary side and connected to a device. However,
in the event of an external fault causing a high short-circuit current to pass through the
current transformers 1 and 2, the restraint of the differential protection would be insuf-
ficient.
Figure 2-1
Protected object with 3 ends and 3 devices
If the device is connected to voltage transformers, set this condition in address
144
V-TRANSFORMER
. The voltage dependent functions such as e.g. distance protection
can be used if voltage transformers are connected.
If a power transformer is located within the protected zone, set this condition in
address
143
TRANSFORMER
order option). The actual transformer data will be re-
quested when the general protection data are set (see Section 2.1.4.1 under margin
heading „Topological Data for Transformers“ (optional)).
If you want to configure differential protection with charging current compensation, set
this condition in address
149
charge I comp.
.
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