RFL 9300 RFL Electronics Inc.
August 9, 2001 4 - 10 (973) 334-3100
4.2.19 OVHD/UGD - OVERHEAD OR UNDERGROUND CABLE
Parameter #38 (OVHD/UGD) sets the RFL 9300 for use with overhead or underground cables.
This parameter only has meaning if the Bias Control Function (parameter #22) is enabled. It
should be set to "OVHD" if the protected line is an overhead line, or an underground line that is
shorter than about 10 miles (16 km). This parameter should be set to "UGD" if the RFL 9300 is
protecting an underground line that is longer than about 10 miles (16 km).
The "UGD" setting adds another 1.5 amperes of desensitization to the bias control, or a total of
3.0 amperes. This increment applies to both the phase bias and the ground bias. The following
example shows how this works:
Phase Ground
Bias Setting: 2.0A 1.5A
Bias Control Increment:
OVHD Setting: 1.5A 1.5A
UGD Setting: 3.0A 3.0A
Actual Bias During Bias Control Interval:
OVHD Setting: 3.5A 3.0A
UGD Setting: 5.0A 4.5A
4.2.20 OPEN CON - OPEN CONDUCTOR
Parameter #39 (OPEN CON) determines how the RFL 9300 responds to open conductors in the
protected line. It can be set to either ALARM or TRIP.
As explained in paragraph 3.16 of this manual, most open conductors also involve a ground
fault. These conditions are detected by charge comparison. The rare case of an open conductor
without a ground fault is detected in the RFL 9300 by a loss-of-load condition that persists for
Zone 2 time (which is factory set at 500 ms).
In most applications, this parameter should be set to "TRIP." The exposure to an overtrip is very
rare: an open conductor, not involving ground, on an adjacent line that has no other load or gen-
eration connected to the remote bus.
4.2.21 CM ALM D - COMMUNICATIONS ALARM DELAY
Parameter #41 (CM ALM D) controls the action of the RFL 9300's communications alarm relay.
It does this be enabling or disabling a 5-second delay timer in the relay drive circuit.
If this parameter is set to ENABLE, the TX/RX indicator on the RFL 93 SV Supervisor Controller
will light as soon as a communications failure is detected. Five seconds later, the communica-
tions alarm relay will change state; indicating the alarm. If this parameter is set to DISABLE, the
indicator and relay will change state at the same time.
4.2.22 DC FILT - DC FILTER
Parameter #42 (DC FILT), when enabled, blocks operation for wide half-cycles (greater than 10
ms). For heavy tapped load applications, this parameter should be enabled. DC FILT is not dis-
played when the RFL 9300 is configured for 3-terminal operation.
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