I.L. 40-386.3
(10/94) 1-3
1.2.2 Standard Features for REL 302 (Pilot)
• All features listed as standard for the REL 301 are included in the REL 302 also
• Independent pilot phase and ground distance units
• Permissive Overreach Transfer Trip (POTT) /Simplified Unblocking
• Permissive Underreach Transfer Trip
• Directional Comparison Blocking Scheme
• POTT or Simplified Unblocking Weakfeed Terminal Logic
• Instantaneous Forward Directional Overcurrent Function for High Resistance
Ground Fault Supplement to Overreach Pilot
• Instantaneous Reverse Directional Overcurrent Ground Function for Carrier Start
on Blocking Scheme
• Reclose Block on Breaker Failure Squelch
• 3-Terminal Line Application
1.2.3 Optional Features for the Non-Pilot REL 301 and Pilot REL 302
• Self-polarized ground distance characteristics (Version 1.7X)
• RS-232C front communications port
• 5 programmable contact outputs
• Man Machine Interface (LCD Display)
• Reclosing with or without synchronism/Voltage Check
• 0 to 4 reclose attempts
• Instantaneous or time delay
• Reset Timer
• Live-Line Dead-Bus/Dead-Line Live-Bus logic
• Synchronism check
•120 Volt phase-to-phase synchronism voltage input (reference VS, VSR,
Figure 4-2)
1. 3. REL 301/302 CONSTRUCTION
All of the relay circuitry, with the exception of the first-line surge protection, is mount-
ed on the inner chassis, to which the front panel is attached. The outer chassis has a
backplate, which is a receptacle for all external connections, including a communica-
tion interface. The FT-10 switches permit convenient and safe disconnection of trip, ac
and dc input circuits, and provide for injection of test signals.
1.3.1 REL 301/302 Outer Chassis
This is an FT-42 case, where all the input/output signals are surge protected. All ex-
ternal connections are made through the rear of the case.
The outer chassis (Figure 1-4) consists of 2 surge protection modules, a backplane
surge protection module, a metal case, FT-switches and an communication interface
consisting of a Product Operated Network Interface (PONI) INCOM
®
or RS-232C that
is mounted on the back of the case from the inside on the backplane module.
1.3.2 REL 301/302 Inner Chassis
The inner chassis (Figure 1-5) consists of a frame, 2 switchjaws and the following mod-
ules. Each module is identified by silk screen label.
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