I.L. 40-386.3
(10/94) 2-13
Zone2, Zone3
(Z2Z3) — start data taken if Zone2 or Zone3 units pick up, or any trip action
occurs.
∆V or ∆I (∆V∆I) — start data taken if ∆I, ∆V, Zone2 or Zone3 units pick up, or any
trip action occurs.
NOTE: See 2.4.10 for ∆V ∆I setting.
2. 5 REL 302 PILOT SYSTEM
NOTE: The external Pilot Enable Switch (Terminals TB4/9 and TB4/10) must
be used in conjunction with the Pilot setting to enable the pilot system.
2.5.1 Pilot System Type
The REL 302 functional display (see Section 4, Table 4-1, Sheet 2 of 4) Function Field
“SystType” is used for pilot system selection, as follows:
• Non-pilot, 3 Zone distance
• Zone1 extension (non-pilot)
• POTT (Permissive Overreach Transfer Trip/Simplified Unblocking).....(pilot)
• PUTT (Permissive Underreach Transfer Trip).....
(pilot)
• Blocking .....(pilot)
The following settings are recommended for POTT and BLOCKING systems:
OSC Date - Zone2, Zone3
Flt Data - Trip
FDOG Time - longer than 3 cycles
Pilot Ø/Pilot G - 150% overreach the next bus
Zone1Ø/Zone1G - 80% of the protected line
Zone3Ø/Zone3G - 100% of the reversed line
Zone3 - Reverse dir.
2.5.1.1 Permissive Overreach Transfer Trip/Simplified Unblocking
If the functional display “SystType” is set at the POTT position, REL 302 will perform
either the POTT scheme or the Simplified Unblocking scheme, depending on the ap-
plied pilot channel.
The basic operating concepts of a POTT scheme are:
1) Pilot relays, pilot phase and pilot ground (Pilot Ø/and PLTG) are set to overreach the
next bus.
2) Pilot channel is a frequency shift type device; its signal may be through either
metallic wire, leased telephone circuits, power line carrier, microwave, or fiber
optic channels.
3) Transmitter frequency should be different at each terminal: channel is normally
operated on a guard frequency; and the channel frequency will be shifted from
guard to trip when the pilot relay(s) are operated. Pilot tripping is performed
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