Permissive Underreach Transfer Trip (Putt) - GE LPS-D Instruction Manual

1.8 PROTECTION SCHEME DESCRIPTIONS
1
Figure 1–11: PUTT LOGIC DIAGRAM on page 1–29 is the logic diagram for the PUTT scheme. A PUTT
scheme requires Zone 1 functions as well as overreaching zone functions. Zone 1 trips directly via OR1,
AND4, OR25, OR3, OR4, AND3, OR13, AND13, OR35, and AND35 and keys the transmitter to the trip fre-
quency via OR5. Tripping for internal faults not seen by the Zone 1 functions occurs when an overreaching
function operates and the receiver(s) produce an output, satisfying the input conditions of the AND1 compara-
tor.
The considerations for receiver connections for a three-terminal line application and 52/b contact keying of the
transmitter with one end open are different from those described above under the POTT scheme. As with a
POTT scheme, a PUTT three-terminal line application requires two receivers and one transmitter at each ter-
minal, with each frequency-shift transmitter operating at a different frequency. However, the two receivers are
ORed together at OR21, rather than ANDed together as with a POTT scheme. This is necessary since the
Zone 1 functions at only one end of the three-terminal line may respond for an internal fault.
For a three-terminal PUTT application, do not use 52/b contact keying of the transmitter. Because the two
receivers are ORed together, a continuous trip signal sent from the open end, when only one end is open,
results in over-tripping for external faults within the reach of the pilot overreaching functions. Unfortunately, this
means a portion of the line is not protected by the pilot scheme. In the LPS-D, 52/b contact keying of the trans-
mitter is automatically prevented if Protection Setting 1201: PICKSCHEME = 2 [PUTT] and Protection Setting
1202: NUMRCVR = 2 [2 RCVRS], as indicated in Figure 1–11: PUTT LOGIC DIAGRAM by the link between
AND5 and OR5. 52/b contact keying of the transmitter should be used for a two-terminal PUTT application.
T Y P E N S 4 0 A
( W I T H R C V R O U T P U T ' T ' )
( R E C E I V E R
O U T P U T )
K 3
( S W I T C H E D P O S I T I V E B A T T E R Y )
K E Y
T R A N S M I T T E R
T O T R I P
( S W I T C H E D N E G A T I V E B A T T E R Y )
Figure 1–10: PUTT/POTT INTERCONNECTION DIAGRAM WITH NS40A
1-
28

1.8.3 PERMISSIVE UNDERREACH TRANSFER TRIP (PUTT)

T B 1
2
1
2 4
2 5
6 0
1 2
U 9
1 1
5 9
LPS-D Line Protection System
( + ) B A T T E R Y
(-) BATTERY
L P S - D S E T F O R P O T T S C H E M E
PICKSCHEME = 1 ( P E R M I S S I V E O V E R R E A C H T R A N S F E R T R I P )
S H O W N F O R T H E D E F A U L T
L P S - D I / O A S S I G M E N T S
B 5
K T 1 K E Y T R A N S M I T T E R
B 2 1
K E Y T R A N S M I T T E R
I N T E R C O N N E C T D I A G R A M
F O R P O T T S C H E M E
U S I N G N S 4 0 A A U D I O T O N E S E T
A N D
L P S - D R E L A Y S Y S T E M
1 PRODUCT DESCRIPTION
L P S - D
D 2
( R E C E I V E D
C C 1
T O N E )
D 1 8
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