Basler Electric BE1-700 - Manual (Page 42)

Zero-Sequence Voltage
When four-wire VT connections are used, the BE1-700 calculates the zero-sequence voltage (3V
0
). Zero-
sequence voltage measurement is not available when single-phase or three-wire VT connections are
used. The 27X and 59X can be set to monitor the zero-sequence voltage.
Negative-Sequence (V
2
) Voltage
Negative-sequence (V
2
) voltage is calculated from the fundamental component of the three-phase voltage
inputs. It is only available on three-phase, three-wire, or three-phase, four-wire systems. V
2
is calibrated
to the phase-to-neutral base. Negative-sequence measurements can accommodate either ABC or ACB
phase-sequence.
Frequency Measurement (BE1-700V)
Power system frequency is monitored on the A-phase voltage input or the AB voltage input when in three-
wire mode. When the applied voltage is greater than 10 volts, the BE1-700 measures the frequency. The
measured frequency is used by the 81 function and applies to all measurements and calculations.
Frequency Compensation
After measuring the frequency, the BE1-700 varies the sampling rate to maintain 12 samples per cycle
over a frequency of 10 to 75 hertz. If the voltage is too low for accurate frequency measurement or if the
measured frequency is out of range, the ADC defaults to a sampling rate appropriate for the relay nominal
frequency setting. The sampling rate is adjusted every 50 milliseconds.
Nominal Frequency
Nominal frequency (F
nom
) can be set for 25 to 60 hertz power systems. When the voltage and current are
too low for reliable frequency measurement, the ADC sample rate defaults to operation at the nominal
frequency setting. Nominal frequency is also used in the volts/hertz (24) overexcitation calculation.
Measurement Functions Setup
The BE1-700 requires information about the power system and its current and voltage transformers to
provide metering, fault reporting, fault location, and protective relaying. This information is entered using
BESTCOMS
™. Alternately, it may be entered at the HMI (see Section 10, Human-Machine Interface) or
through the communication port using the following ASCII commands: SG-CT, SG-VTP, SG-VTX, SG-
FREQ, SG-NOM, and SG-PHROT.
Power System Settings
To enter power system settings, select General Operation from the Screens pull-down menu. Then select
the Power System tab.
Use the pull down buttons and menus to make the power systems settings. Nominal Frequency can be
set for 25 to 60 hertz power systems. Nominal Phase Rotation can be set for either ABC rotation or ACB
rotation.
Nominal Secondary Voltage and Current Settings, V
nom
and I
nom
, are used by the 60FL function. V
nom
is
also used in the volts/hertz (24) calculation, and I
nom
is also used in the 46 time curve calculation (K factor)
of the negative-sequence current (51Q) element.
Nominal Voltage (V
nom
) is defined as the secondary phase-neutral voltage for all sensing connections.
That is, even if the user has selected 3-wire, AB, BC, or CA phase-phase sensing connections, V
nom
must
be set for the phase-neutral equivalent. For example, if a 3-wire open delta voltage source with a phase-
phase voltage rating of 120 volts is connected, the nominal voltage must be set at 120/
3 or 69.3 volts.
I
nom
can be either the secondary rating of the CT (1 or 5 amp) or the secondary current allowed by the CT
ratio.
In BESTCOMS for the BE1-700, under General Operation screen Power System tab, are settings for
Nominal Voltage and Current. Nominal Voltage (V
nom
) is the nominal voltage rating corresponding to 1 pu
volts and is configured as a phase-neutral secondary value.
Nominal Current (I
nom
) is the nominal phase current rating for the system corresponding to 1 pu current
and is configured in secondary amps. If 1 pu secondary current is unknown, then setting I
nom
to the
secondary CT rating (1 or 5 A) is acceptable for most applications. However, this could degrade the
expectation (not accuracy) of the time curve for the 51Q element as I
nom
is used to directly compute
multiple of pickup (MOP) and time delay.
3-2 BE1-700 Input and Output Functions 9376700990 Rev M