Table of Contents
Advertisement
I.L. 40-385.5
(a)
Tripping Logic
The tripping logic for the PUTT scheme is exactly the
same as for the POTT scheme. (Figures 26, 29)
(b)
Carrier Keying Logic
(1)
Forward fault keying (Figure 29)
For a forward end zone fault, the PUTT
scheme will not key unless the internal
fault is within the Zone-1 reach. This
means that the PUTT scheme keys only
on Zone-1 faults. The keying will occur
via AND-46, OR-18 and AND-35.
(2)
Signal continuation (Figure 29)
Same as for POTT scheme.
Note: For open breaker condition, the echo key-
ing will not work due to lack of the "SEND"
signal from the remote terminal for an end
zone fault. The remote terminal relies on
Zone-2 to clear the fault.
(c)
Carrier receiving logic (Figure 29)
Similar to POTT scheme.
(d)
Channel indicators
Similar to POTT scheme.
(e)
Channel simulation
Similar to POTT scheme.
(f)
TBM
There is no power reversal problem on PUTT
scheme.
(g)
Programmable Reclosing Initiation (Figure 24)
Same as for POTT scheme.
10.1.3 Directional Comparison Blocking System
(BLK)
If the functional display "STYP" is selected to BLK,
the MDAR (REL-300) will perform the blocking
scheme.
The following IMPORTANT settings are recom-
mended for blocking system:
OSC
=
Z2Z3
FDAT
=
TRIP
PLT
=
YES (must)
STYP
=
BLK (must)
FDGT
>
3 cycles
Z3FR
=
REV (must)
The basic operating principles of a directional com-
parison blocking system, BLK, are:
10-4
(a)
The pilot relays, PLTP/PLTG, are set to over-
reach,
(b)
The Zone-3 relays, Z3P/Z3G, should be set in
the reverse direction (Z3FR = REV) to detect
the reverse external faults and for carrier start.
Referring to Figure 30, the MDAR (REL-300)
blocking scheme also uses ∆I, ∆V and RDOG
information to start the carrier. The use of high
speed ∆I and ∆V signals for carrier start pro-
vides more security to the scheme.
(c)
Pilot channel is an ON-OFF type power line
carrier. Transmitter frequency at each terminal
can be the same.
(d)
Channel is normally OFF until the carrier start
unit(s) senses the fault and starts the transmit-
ter.
(e)
Pilot trip is performed when the pilot relay(s)
operates and a carrier blocking signal is not
received.
The operating principle of the pilot distance measure-
ment units, PLTP/PLTG are the same as the non-pilot
zone distance measurement units, and are super-
vised by the same LOPB, OSB, FDOP, FDOG, IM
and I
units as shown in Figure 26.
oM
For more dependability on high R
ground PLTG trip logic is supplement with the FDOG
and I
units, as shown in Figure 26. The direction of
oM
the forward directional overcurrent ground unit,
FDOG, is determined by setting the DIRU to ZSEQ,
NSEQ or DUAL. The delay timer FDGT has a range
of 0 to 15 cycles, in 1.0 cycle steps. It can be blocked
by setting the FDGT to BLK.
The pilot distance unit, PLTG, is always active and
has the priority for tripping, therefore, practically, the
FDGT timer should be set to 3 cycles or longer for
security reason.
The pilot phase and/or pilot ground function(s) can
be disabled by selecting the PLTP and/or PLTG to
OUT. (note, the FDOG pilot trip function will also be
disabled when PLTG set to OUT).
The BLK system, as shown in Figure 30, includes the
following portions:
(a)
Tripping Logic (Figure 26
(1)
For a forward internal fault, the local pilot
relay(s), PLTP and/or PLTG, sees the
fault. Output signal of OR-40 disables
and stops the carrier start circuit (note,
the ∆I and ∆V starts the carrier before
faults, the pilot
f
Advertisement
Table of Contents
