Basler Electric BE1-11t - Manual (Page 293)

9424200995 Rev H 281
Configuration
BE1-11t inputs consist of two sets of three-phase current inputs and ground, three-phase voltage inputs,
and one auxiliary voltage input. Each input is isolated and terminated at separate terminal blocks. This
section describes the function and setup of each input, and provides the equations that the BE1-11t uses
for calculating the power quantities.
Power System Measurements
Power system inputs, as described in the introduction, are sampled 32 times per cycle by the BE1-11t.
The BE1-11t measures the voltage and current from these samples and uses those measurements to
calculate other quantities. Frequency is measured from a zero-crossing detector. Measured inputs are
then recorded every quarter-cycle. If the applied voltage is greater than 10 volts, the BE1-11t measures
the frequency and varies the sampling rate to maintain 32 samples per cycle. Frequency compensation
applies to all power system measurements. Power system inputs are described in the paragraphs under
the following headings: Current Measurement, Voltage Measurement, Frequency Measurement, and
Power Measurement.
Current Measurement
Secondary current from power system equipment CTs is applied to current transformers inside the BE1-
11t. These internal transformers provide isolation and reduce the monitored current to levels compatible
with BE1-11t circuitry. Secondary current from each internal CT is converted to a voltage signal and then
filtered by an analog, low-pass, anti-aliasing filter.
Current Measurement Functions
Input waveforms are sampled by an analog-to-digital converter (ADC) at 32 samples per cycle. The
BE1-11t extracts the magnitude and angle of the fundamental components of each three-phase current
input and the magnitude and angle of the independent ground current input.
Positive-Sequence, Neutral and Negative-Sequence Current Measurement
Positive-sequence (I1), neutral (3I0), and negative-sequence (I2) components are calculated from the
fundamental component of the three-phase current inputs. The BE1-11t can be set to accommodate ABC
or ACB phase-sequence when calculating the positive- or negative-sequence component.
Fast Current Detector
A separate, fast current measurement algorithm is used by the breaker failure function and the breaker
trip-speed monitoring function. This measurement algorithm has a sensitivity of 5% of the CT rating (5A or
1A depending on style number) and detects current interruption in the circuit breaker much more quickly
than the regular current measurement functions. This measurement algorithm monitors only the phase
current.
Voltage Measurement
Three-phase voltage inputs are reduced to internal signal levels by a precision resistor divider network. If
the BE1-11t is set for single-phase or four-wire VT operation, the measuring elements are configured in
wye. If the BE1-11t is set for three-wire VT operation, the measuring elements are configured in delta.
Voltage Measurement Functions
Input waveforms are sampled by an analog-to-digital converter (ADC) at 32 samples per cycle. The
BE1-11t extracts the magnitude and angle of the fundamental components of each three-phase voltage
input and the magnitude of the auxiliary voltage input.
BE1-11t Configuration