9328900990 Rev L BE1-951 Protection and Control 4-39
Table 4-22. Operating Settings for Phase Undervoltage/Overvoltage
Setting Range Increment Unit of Measure Default
Pickup
0 = Disabled
10 to 300
0.1 for 0 to 99.9
1.0 for 100 to 300
Secondary Volts †
0
50 to 999 milliseconds 1 Milliseconds
0.1 for 1.0 to 9.9 Seconds
1 to 600 seconds
1.0 for 10 to 600 Seconds
3 to 36,000 cycles (60 Hz)
Time Delay
2.5 to 30,000 cycles (50 Hz)
∗
Cycles
50 ms
∗ Time delays less than 10 cycles can be entered to the nearest 0.1 cycles from the front panel HMI. All
time delays can be entered to the nearest 0.01 cycles from the ASCII command interface. Time delays
entered in cycles are converted to milliseconds or seconds. Increment precision after conversion is limited
to that appropriate for each of those units of measure.
† Unit of measure is secondary VPP or secondary VPN depending on the VTP connection settings.
Time delay settings entered in cycles are converted to seconds or milliseconds (per the nominal
frequency setting stored in EEPROM) before being stored. See Section 3, Input and Output Functions,
Power System Inputs, Voltage Measurement for more information about this setting. If the nominal
frequency setting is being changed from the default (60 hertz) and time delay settings are being set in
cycles, the frequency setting should be entered and saved before making any time delay settings
changes.
27X/59X - Auxiliary Undervoltage/Overvoltage Protection
Figure 4-32 illustrates the inputs and outputs of the auxiliary under/overvoltage elements. Element
operation is described in the following paragraphs.
D2871-21
05/13/02
159XT
159XPU
BLK
159X
Mode
BLK
27XT
27XPU
AUX
UNDER-
VOLTAGE
(27X)
Mode
0-Disable
1-Fundamental Vx Input
2-3VO - 3ph VT Input
3-Harmonic Vx Input
BLK
59XT
59XP
AUX
OVER-
VOLTAGE
(59X)
Mode
0-Disable
1-Fundamental Vx Input
2-3VO - 3ph VT Input
3-Harmonic Vx Input
Figure 4-32. Auxiliary Undervoltage/Overvoltage Logic Blocks
The auxiliary elements have two outputs: 27X/59X/159XPU (pickup) and 27X/59X/159XT (trip). When the
monitored voltage increases above the pickup setting, the pickup output becomes TRUE and the element
starts timing toward a trip. The trip output becomes TRUE when the element timer times out.
The Block (BLK) input is used to disable protection. A BESTlogic expression defines how the BLK input
functions. When this expression is TRUE, the element is disabled by forcing the outputs to logic 0 and
resetting the timer. This feature functions in a similar way to the torque control contact of an
electromechanical relay.
The 27X, 59X, and the 159X elements are enabled or disabled by the Mode input. Four modes are
available. Selecting Mode 0 disables protection. Mode 1, 2, 3 enables the element, as described in this
section under BESTlogic Settings for Auxiliary Undervoltage/Overvoltage.
The pickup setting determines the voltage pickup level of the element. The time delay setting controls
how long it takes for the trip output to become TRUE after the pickup output becomes TRUE. When the
monitored voltage increases above the pickup threshold, the pickup output becomes TRUE and the timer
starts. If the voltage remains above the pickup threshold for the duration of the time delay setting, the trip
output becomes TRUE. If the voltage decreases below the 59X/159X dropout ratio of 98% or increases
above the 27X dropout ratio of 100%, the timer is reset to zero.
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