Basler Electric BE1-47N - Manual (Page 18)

3-2 BE1-47N Functional Description 9170400990 Rev J
Phase Shifting
The respective secondary voltages are phase shifted ±45° each, with respect to signal ground and then
summed to nullify the positive sequence component.
Pickup Scaling
The resolved negative sequence voltage (V
2
) ac signal is then applied to the pickup scaling network
(switch S1 and its associated resistors). The pickup network establishes per-unit (PU) values of negative
sequence voltage for the comparison and timing functions.
Low-Pass Filter
The sensing circuits for negative sequence voltage, overvoltage, and undervoltage are designed to
operate on the fundamental frequencies of 50 or 60 hertz. The low-pass filter passes the fundamental
frequencies and attenuates the higher frequencies.
Negative Sequence Voltage Comparator
The proportionate negative sequence (V
2
) signal is compared to a reference level. When the level of the
per-unit negative sequence voltage exceeds the reference level, the pickup indicator lights and timing is
initiated.
Overvoltage/Undervoltage Comparator
Optional single-phase overvoltage and undervoltage circuits operate on the voltage magnitude. The
single-phase ac signal is low-pass filtered and passed to the respective comparator where it is compared
to the pickup settings for each circuit. If either pickup setting has been exceeded (overvoltage or under-
voltage), the appropriate LED lights and timing is initiated.
Timing
One of three timing characteristics is available for each of the three protection functions: definite, inverse,
or instantaneous. The timing characteristic may be independently selected for each protection function.
Table 3-2 identifies the timing style selections for negative sequence voltage, undervoltage, and over-
voltage protection.
Table 3-2. Timing Characteristic Style Number Selections
Protection Function
Timing Characteristic
Instantaneous Inverse Definite
Undervoltage (27) xxx-xxx-x 1xxx xxx-xxx-x 2xxx xxx-xxx-x 3xxx
Negative Sequence Voltage (47N) xxx- A1x-xxxxx xxx- D1x-xxxxx xxx- E1x-xxxxx
Overvoltage (59) xxx-xxx-xx Rxx xxx-xxx-xx Sxx xxx-xxx-xx Txx
Definite timing is adjustable from 0.1 to 9.9 seconds in increments of 0.1 seconds.
The response time of instantaneous timing is less than 50 milliseconds. When the timing characteristic for
a protection function is definite or inverse and the time delay setting is 00, instantaneous timing is
achieved.
Inverse timing is adjustable from 01 to 99 in increments of 1 (see Figures 3-2 through 3-4 for the inverse
time characteristic curves). When evaluating inverse curves for overvoltage or undervoltage protection,
note that timing is based on the percent difference from the system’s nominal voltage. For example, refer
to Figure 3-4. If the monitored voltage is at a level of 18% below system nominal, the portion of the curves
below 18% (e.g., 13%, 8%, etc.) has no effect on the timing characteristic. In other words, the timing
curve beginning is dependent upon the monitored voltage percent difference from the system’s nominal
voltage. Inverse timing characteristics preceding this defined point are nonexistent.