7SG164 Ohmega 400 Series Stub Protection
1 Stub Protection
The Stub protection function in the relay is used to protect a short section of bus bar when the plant configuration
is such that the line V.T. is switched out of circuit. The relay uses an over current element who’s output is gated
with a status input.
When a disconnector is opened the status input is energised enabling the output or the over current detector. This
current detector is arranged to measure any current in unprotected zone. Typical CT arrangements are shown in
figures 1 & 2.
If the setting is exceeded an LED is illuminated displaying stub protection trip or alarm.
Data storage can only be initiated from a trip condition.
The current elements are instantaneous transient free elements, which have an independent DTL timer. The
output can be set to 0s for instantaneous operation or time delayed up to 1000 ms.
To switch on the stub protection function it has to be enabled in the AUXILLIARY PROTECTION MENU. If the
function is not enabled any applied settings for that function is ignored.
2 Settings
The current setting can be selected between 10 – 200% of In.
The alarm function can be mapped to any of the output contacts. The trip function will operate whichever
contact(s), has been set to cause a trip.
21
Un protected
zone
Figure 1
©2011 Siemens Protection Devices Limited
Chapter 12 Page 3 of 4