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IB02602004E
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Instructional Literature
Effective: May 2008
Page
95
Instructions for the FP-6000 Protective Relay
Once the voltage restraint is enabled, the effective phase time
overcurrent pickup threshold will be the calculated P% times the
phase time overcurrent pickup setting. The effective pickup
threshold must be within the setting range allowed and if it’s less
the minimum pickup value will be used (see Figure 20).
Figure 20. Voltage Restraint Characteristic.
50P-1 PH IOC 1 and 50P-2 PH IOC 2
These are the two 50 device phase instantaneous overcurrent
settings, which are two independent elements. Both units have
time delay settings available. One element could be used for a
“Short Time” element (with a short time delay) and the other as
“Instantaneous” element (with zero time delay) to improve
flexibility and coordination of the OC curves. The pickup setting
(range of 0.1 to 20.0 per unit in 0.01 steps). The time delay may
be set from zero to 9999 cycles in 1 cycle steps. The cycle time is
based on power system frequency. The direction setting
operates the same as described above in the 51P PH TOC Curve
Settings.
5.4.2.2 IX Measured OC Settings
51X IX TOC Curve
This includes is the 51 device Inverse Time Overcurrent Curve
Setting based on the measured fourth CT input which is usually
used for neutral or ground overcurrent protection. It is
independent from the phase elements and may have its
measurement from a ground CT, neutral CT or residual
connection of the phase CTs for ground current measurement.
The user selects the shape, the reset of the TOC curve and the
direction setting. The available settings and setting ranges are
the same as the 51P PH TOC settings described above.
51X IX TOC Setting
This is the 51 device Time Overcurrent pickup and time multiplier
settings based on the measured fourth CT input. The user selects
the pickup and the time multiplier of the TOC curve. The available
settings and setting ranges are the same as the 51P PH TOC
Settings shown above. The pickup settings are in per unit and are
based on the connected CT ratio. If a ground CT is used then the
ratio may be different than the phase CT ratio. If a residual
ground current connection is used then the CT ratio is the same
as the phase CT ratio.
50X-1 IX IOC 1 and 50X-2 IX IOC 2
These are the two 50 device IX instantaneous overcurrent
settings, which are two independent elements. The settings
operate the same as the 50P-1 PH OC 1 and 50P-2 PH OC 2
Settings.
5.4.2.3 IR Residual OC Settings
51R IR TOC Curve
This is the 51 device Residual Inverse Time Overcurrent Curve
Setting, which is a residual ground overcurrent protection
function. This is a calculated ground current from the sum of the
measured phase currents. For a 3-phase, 3-wire system, this
current is: IR = IA + IB + IC. This calculated value is affected by
the CT Connect Setting in the System Config. Settings. In most
applications this function is redundant to the 51X functions
described above but does not require a ground current
connection. The user selects the shape, the reset of the TOC
curve and direction. The available settings and setting ranges
are the same as the 51P PH TOC settings.
51R IR TOC Setting
This is the 51 device setting Residual Inverse Time Overcurrent
pickup and time multiplier settings. The user selects the pickup
and the time multiplier of the TOC curve. The available settings
and setting ranges are the same as the 51P PH TOC settings. The
pickup settings are in per unit and are based on the connected
phase CT ratio.
50R-1 IR IOC 1 and 50R-2 IR IOC 2
These are the two 50 device residual IR instantaneous
overcurrent settings, which are two independent elements. The
settings operate the same as described in the 51P PH TOC
settings. The pickup settings are in per unit and are based on the
connected phase CT ratio. The direction setting operates in the
same manner.
V
max
25%V
max
Pickup%
100%
25%
V