Triple/Single Modes Of Operation - Siemens 7SR224 Technical Manual

7SR224 Argus Applications
valley C; all with single phase to Neutral loads. A permanent phase to neutral fault and single pole Recloser
sequence to Lockout on pole A will not, therefore, affect the supply to customers in valleys B and C.
For a fault at the position shown on Phase A, the A pole CB/Source Recloser will go through a sequence of Fast
plus Delayed Trips to attempt to clear the A-G(N) fault. For a permanent A-G fault the outcome will be that pole A
goes to Lockout and phase A will be left totally dead. Customers on Phases B and C will continue to receive
uninterrupted supply, they will not suffer interruptions.
It should be noted that Single/Triple operation of Reclosers is applied to Rural Feeders and for these Loss Of
Voltage (LOV) automation is not applied, (to do so would require a very complex LOV scheme requiring single
pole closure of the NOP (TIE) and Feeder Reclosers with resultant single pole back-feed.). In the MLFB LOV
Automation is not to be made available with Single /Triple Software.
Single-phase Tripping/Reclosing improves system reliability by maintaining supply to customers who are not on
the faulted phase of a feeder. When a permanent fault occurs on one of the phases e.g. on the B phase, only the
B pole Recloser performs a Trip and Reclose sequence, A and C phases, if unaffected, stay Closed maintaining
supply to the Customers on poles A and C. If a single-phase reclosing sequence is unsuccessful because of a
permanent fault, only the customers on the B phase are left without power, rather than all three-phases locking
out. Single-phase operation will be applied, especially in rural areas where the majority of loads are single phase
L-N and manual restoration can take longer because of the greater travel distances.
Note:- All unbalance Protection elements i.e. NPS, Broken Conductor, Loss of Phase, VTS, CTS, etc. algorithms
have to be inhibited or pre-set to a long ride-through delay, BEFORE a single pole Recloser Trip is issued to
prevent false operation during single-phase sequence Dead-Times, or inhibited when a single-phase Lockout
state is reached. Because of the inherent unbalanced nature of three poles of single pole to neutral loads the NPS
levels will be high on such systems and even higher when one pole trips out leaving only two poles energized,
therefore, when Single pole Trip is selected all Unbalance protection elements are usually Inhibited. The ZPS will
also be high, same level, but a considerable percentage will return via the Neutral conductor, therefore, a Neutral
CT is essential, the rest via the multiple Ground paths.
4.4.2

Triple/Single Modes of Operation

The User may select one of three modes for the Single/Triple operation to suit the system load characteristics and
thus avoid subjecting loads to conditions which could cause damage to plant. The settings of the Trip-Reclose-
Lockout operation modes for the Recloser provide for three Modes of Trip Sequences to Lockout for a permanent
fault. Mode selection can be via Settings menu to provide default mode, via Control Mode Menu, or via Settings
Group change either in response to a General Command via SCADA or by Binary Input selection. If more than
one mode is selected simultaneously, the priority is Mode A over B over C with Modes as defined below. When a
binary input mapped to this function is energised, the setting is changed to the selected Mode. The setting does
not revert to its previous state when the input is reset. The additional LEDs available on E12 Controllers can be
used to show which Mode is ON. Only the selected Mode LED will be ON. Single Pole Reclosers can be operated
by the User in any one of the following modes as and when the application requires it. Three single pole
Reclosers connected in a full single pole wired scheme may thus be operated individually or together as a three
pole Recloser as system operations require.
[It should be noted that Single/Triple operation only applies to Phase Fault elements and not to Earth Faults nor to
Sensitive Earth faults. The use of three CTs, one per pole, and a single neutral CT i.e. 4 CTs, only allows
detection that an SEF/Earth Fault has occurred but not on which pole. This determination is only possible if a
Phase to Earth Fault current is above the Phase Fault Overcurrent setting, it is then possible to single pole trip
and reclose as per the logic shown in tables in the Description of Operation section of this manual. Therefore, in
the absence of any supplementary data, an SEF trip and/or Earth fault trip must cause Three pole Trip and Three
pole Reclose.
MODE A 3PTrip-3PLO
This is the standard Three pole only mode of operation, only three pole Trip/Close sequences are performed and
all three poles are Locked Out together when the Lockout state is reached. This mode is used where three phase
loads such as motors cannot be allowed to on two phases, even for the duration of the autoreclose deadtime.
In this mode any pole CB Trip or CB Close Command must operate all three Reclosers.
In this mode a Line Check Trip or Trip & Lockout Command causes a 3PTrip-3PLO .
In this mode any single manual Lockout Lever Command causes a 3PTrip-3PLO .
In this mode the Hot Line On Command primes a single 3PTrip-3PLO .
©2010 Siemens Protection Devices Limited Chapter 7 Page 41 of 50