Protection Of Substation Busbars - GE P741 Technical Manual

Application Notes
MiCOM P741, P742, P743
1. INTRODUCTION
Before carrying out any work on the equipment, the user should be familiar with the contents
of the safety section/safety guide Pxxx-SG-4LM-2 or later issue, the technical data section
and the ratings on the equipment rating label.
1.1

Protection of Substation Busbars

The busbars in a substation are possibly one of the most critical elements in a power
system. If a fault is not cleared or isolated quickly, not only could substantial damage to the
busbars and primary plant result, but also a substantial loss of supply to all consumers who
depend upon the substation for their electricity. It is therefore essential that the protection
associated with them provide reliable, fast and discriminative operation.
As with any power system the continuity of supply is of the utmost importance, however,
faults that occur on substation busbars are rarely transient but more usually of a permanent
nature. Circuit breakers should, therefore, be tripped and not subject to any auto-reclosure.
The busbar protection must also remain stable for faults that occur outside of the protected
zone as these faults will usually be cleared by external protection devices. In the case of a
circuit breaker failure, it may be necessary to open all of the adjacent circuit breakers, this
can be achieved by issuing a backtrip to the busbar protection. Security and stability are key
requirements of a busbar protection scheme. Should the busbar protection maloperate under
such conditions substantial loss of supply could result unnecessarily.
Many different busbar configurations exist.
substation with a transfer bar. The positioning of the primary plant can also vary and also
needs to be considered which in turn introduces endless variations, all of which have to be
able to be accommodated within the busbar protection scheme.
Backup protection is also an important feature of any protection scheme. In the event of
equipment failure, such as signalling equipment or switchgear for example it is necessary to
provide alternative forms of fault clearance. It is desirable to provide backup protection,
which can operate with minimum time delay and yet discriminate with other protection
elsewhere on the system.
A typical arrangement is a double busbar
P74x/EN AP/Na7
(AP) 6-3
AP