IL17569C
Page 5-44
FP-5000
Effective Date: 12/05
Page 5-44
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Effective Date: 12/05
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.
5.4.2.4 Unbalance Settings
47-1 Voltage Unbal
This is the 47 device Voltage Unbalance setting, which consists of
the Threshold, %(V2/V1), and Delay settings. The voltage unbalance
function is based on the Main VT system 3-phase voltages. The
positive and negative sequence voltages are calculated from the
3-phase voltages.
The Threshold setting defines a minimum operating voltage magnitude
of either V1 or V2 for the 47 function to operate, which ensures that
the relay has a solid basis for initiating a voltage unbalance trip. This
is a supervisory function and not a trip level.
The %(V2/V1) setting is the unbalance trip pickup setting. It is
defined by the ratio of negative sequence voltage to positive
sequence voltage (% Unbalance=V2/V1), or %(V2/V1) for ABC
rotation and %(V1/V2) for ACB rotation. The FP-5000 will automati-
cally select the correct ratio based on the Phase Sequence setting in
the System Configuration group described above.
The time delay is a definite time delay adjustable from 0 to 9999
cycles in 1 cycle steps.
This function requires positive or negative sequence voltage
magnitude above the threshold setting and the percentage voltage
unbalance above the %(V2/V1) setting before allowing a voltage
unbalance trip. Therefore, both the threshold and percent settings
must be met for the specified Delay time setting before the relay
initiates a trip for voltage unbalance.
The voltage unbalance pickup and trip functions are reset when the
positive and negative sequence voltages V1 and V2 drop below the
Threshold setting or (V2/V1) drops below the %(V2/V1) setting
minus 1%.
threshold must be within the setting range allowed and if it’s less the
minimum pickup value will be used, see figure 5-6.
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 “Instanta-
neous” 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.
V
m a x
2 5 % V
m a x
u p %
Figure 5-6. Voltage Restraint Characteristic
