Basler BE1-25/79TR, Instruction Manual, Page: 34 / 78

BE1-25/79TR Functional Description
3-7
Figure 3-3. Allowable Closing Zone
Voltage Difference
Voltage difference (delta voltage) is typically used to reduce the amount of possible system shock or
transients when closing a breaker. Delta voltage compares the magnitude of the voltage between the line
and bus against a selected limit. If the delta voltage is less than the set limit, the BE1-25/79TR relay
generates an enable signal for the sync-check logic. This function narrows the phasor voltage across the
breaker contacts (as compared to a simple sync-check acting alone). Figure 3-2 shows the allowable
closing zone obtained by combining voltage difference, phase angle difference, and line and bus live/dead
voltage limits. Available parameters are:
Delta ( ) V
Condition Adjustable from 1 to 135 Vac.
Blocks closing when difference between the magnitude of the bus and line potentials is greater than this
setting.
Indicated by front panel LED's (LL and LB) when LED's are flashing ON and OFF.
NOTE:For 3 phase line and 3 phase bus type relays, only phase B is used for voltage difference check.
Voltage Monitor
Voltage monitoring checks the voltage magnitude difference between the two inputs (line and bus). This
can be used to prevent the closure of a generator breaker if the voltage difference is too great (even if the
phase angle and voltage level monitoring circuits indicate that proper closing conditions are present).
Parameters for determining live or dead conditions are set at the front panel. Line and bus conditions are
indicated by front panel LEDs. Available parameters (refer to Figures 3-3 and 3-4) are: