Alstom MiCOM P846, Technical Manual

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P846/EN OP/D Operation
(OP) 5-12
MiCOM P846
2. OPERATION OF NON PROTECTION FUNCTIONS
2.1 Trip LED logic
As previously mentioned in section 1.1, the DLO is made for monitoring the status of a
transmission line. Upon detection of an open line, the DLO will close its Output contact R3
and will keep it open when the line is closed. As required by the application, a Programmable
Scheme Logic (PSL) may also be used to process this output towards auxiliary LEDs or
output contacts.
nitoring relay, the DLO is not subject to trip or close the line breaker in
.
Being essentially a mo
its normal operation. However, it may be useful to manually control the breaker directly from
the relay. The trip LED logic provides the indication during these operations.
The trip LED can be reset when the flags for the last event are displayed. These are
displayed automatically after a trip occurs, or can be selected in the fault record menu. The
reset of trip LED and the fault records is performed by pressing the ( ) key once the fault
record has been read
Setting "Sys.Fn.Links" (SYSTEM DATA Column) to logic "1" sets the trip LED to automatic
reset. Resetting will occur when the circuit is treclosd and the "Any Pole Dead" signal (DDB
358) has been reset for three seconds. Resetting however, will be prevented if the "Any
start" signal is active after the breaker closes.
OP
Any Pole Dead
Any Start
Trip LED
ENABLE
DISABLE
Tr3Ph (Any Trip)
Reset (Command)
Reset (Logic Input)
SETTING:
SELF RESET
&
3s
0
1
S
R
Q
P2129ENa
Figure 9: Trip LED logic diagram
2.2 Voltage transformer supervision (VTS)
The voltage transformer supervision (VTS) feature is used to detect failure of the ac voltage
inputs to the relay. This may be caused by internal voltage transformer faults, overloading, or
faults on the interconnecting wiring to relays. This usually results in one or more VT fuses
blowing. Following a failure of the ac voltage input there would be a misrepresentation of the
phase voltages on the power system, as measured by the relay, which may result in
maloperation.
The VTS logic in the relay is designed to detect the voltage failure, and automatically adjust
the configuration of protection elements whose stability would otherwise be compromised. A
time-delayed alarm output is also available. There are three main aspects to consider
regarding the failure of the VT supply. These are defined below:
1. Loss of one or two phase voltages
2. Loss of all three phase voltages under load conditions
3. Absence of three phase voltages upon line energization