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Section 10. OPERATION OF MDAR (REL-300) VERSION 2.60
10.1 PILOT SCHEMES
If the MDAR (REL-300) with pilot optional function
and its functional display "STYP" is not selected to
"3ZNP" or "Z1E", it will perform one of the other three
pilot schemes shown below, depending on the set-
ting.
For activate the pilot logic, an external rated voltage
should be connected to the "Pilot Enable" terminals
(Figure 6, TB5/9 and TB5/10), and the setting of PLT
should be set to YES.
Whether the pilot system is in-service or not, the 3-
zone non-pilot function of the assembly is at a sup-
porting backup mode.
STYP
Setting
Scheme
3ZNP
Non-pilot 3-Zone distance
Z1E
Zone-1 extension
POTT
Permissive overreach transfer
trip/unblocking
PUTT
Permissive underreach transfer trip
BLK
Blocking
10.1.1 Permissive overreach transfer trip/simpli-
fied unblocking
If the functional display "STYP" is selected to POTT,
the MDAR (REL-300) will perform either the POTT
scheme or the Simplified Unblocking scheme,
depending on the applied pilot channel.
The following IMPORTANT settings are recom-
mended for POTT and Unblocking system:
OSC
FDAT
PLT
STYP
FDGT
RBSW
Z3FR
The basic operating principles of a POTT system are:
(a)
The pilot relays, PLTP/PLTG, are set to over-
reach the next bus.
(b)
The pilot channel is a frequency shift type
device. Its signal may be through either metallic
wire or microwave.
PILOT AND OPTIONAL FUNCTIONS
=
Z2Z3
=
TRIP
=
YES
=
POTT
>
3 cycles
(blank)
=
REV (must)
(c)
Transmitter frequency should be different at
each terminal. The channel is normally oper-
ated on a guard frequency, and
(d)
the channel frequency will be shifted from
guard to trip when the pilot relay(s) is operated,
and
(e)
pilot trip is performed when the pilot relay(s)
operates and a pilot trip frequency signal from
the remote end is received.
The basic operating principles of a simplified
unblocking system are the same as the POTT sys-
tem, except it is slightly different in application.
(a)
The pilot channel is a frequent shift type power
line carrier. The transmitter frequency must be
different at each terminal. It is normally oper-
ated on a blocking frequency and will be shifted
to an unblocking frequency when the pilot
relay(s) operates, and
(b)
The carrier receiver should provide a logic
which in the event of loss-of-channel or low
SNR ratio, the pilot trip circuit is automatically
locked out after a short time delay. Pilot trip is
provided, however, if the tripping distance
relay(s) operates during this short time period
between loss-of-channel and pilot trip lockout.
(W) type TCF-10B receiver provides this logic.
It provides 150 ms trip window, then automati-
cally locks out after loss-of-channel.
(c)
The function of "indication for low signal and
loss-of-channel" condition will not be provided
on the MDAR (REL-300) simplified unblocking
scheme. It would normally be incorporated in
the power line carrier equipment.
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 and
Iom units as shown in Figure 26.
For more dependability on high R
ground PLTG trip logic is supplemented with the
FDOG and I
units, as shown in Figure 26. The
OM
FDOG directional unit is determined by the setting of
DIRU to ZSEQ, NSEQ OR DUAL. The delay timer
I.L. 40-385.5
faults, the pilot
f
10-1
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