Examples Of Application - ABB SPAJ 131 C User Manual And Technical Description

Examples of
application
10
Fig. 4 shows how the phase overcurrent relay
SPAJ 131 C can be applied for substation pro-
tection. For reasons of clarity the remote control
110/20 kV
Blocking signal
Tripping signal
Fig. 4. Overcurrent relay SPAJ 131 C applied for the protection of a distribution substation.
In example 1 the low-voltage switchgear is pro-
tected by an overcurrent relay SPAJ 131 C. The
trip signal is linked to the HV side circuit
breaker of the distribution transformer.
In example 2 the overcurrent relay SPAJ 131 C
is used for protecting the outgoing feeder of
medium voltage distribution switchgear and in
example 3 it is used for the busbar short circuit
protection.
equipment and possible other protection relays
have been omitted.
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20 kV/380 V
The short circuit protection is based on blockings
between successive protection stages. In such an
arrangement the relay located closer to the fault
gives, when starting, a blocking signal back-
wards to the relay that is closer to the object
supplying the short circuit current. If there is no
blocking, the relay perceives the fault as being in
its own protection area and trips the circuit
breaker. As shown in Fig. 4 the busbar protec-
tion can be extended beyond the power trans-
former feeding the busbar system.
Exemple 3
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Exemple 2
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Exemple 1