Basler Electric BE1-851 - Manual (Page 45)

Negative-Sequence Current
Negative-Sequence components are measured from the fundamental component of the three-phase
current inputs. The relay can be set to accommodate ABC or ACB phase-sequence when calculating the
negative-sequence component.
Neutral Current
The current entering “D7” and leaving “D8” will be understood by the relay to be the neutral current. If
nothing is connected, the relay will understand the neutral current to be zero. No neutral current will be
calculated from any phase imbalance.
Fast-Dropout Current Detector
A separate, fast-dropout current measurement algorithm is used by the breaker failure function and the
breaker trip-speed monitoring function. This measurement algorithm has a sensitivity of 10 percent of
nominal rating and detects current interruption in the circuit breaker much more quickly than the regular
current measurement functions.
Current Measurement Functions Setup
Current Input Circuit Settings. The BE1-851 requires information on the nominal system frequency, DSP
filtering, CT ratio, and phase rotation. These settings are used by the metering and fault reporting
functions to display measured quantities in primary units. The se settings can be entered at the HMI, see
Section 10, Human-Machine Interface, or through the communication ports using the SG-FREQ, SG-
DSP, SG-CT, and SG-PHROT setting general commands. Settings relating to current measurement are
summarized in Table 3-1.
Table 3-1. Current Measurement Function Settings
Settings
Password
Access
Range Default
Unit of
Measure
Nominal Frequency Privilege G or S 50 or 60 60 Hertz
Digital Signal Processing for
Phase and Neutral Response Privilege G or S
Average, Fundamental,
RMS
Fundamental N/A
Normal Phase Rotation None ABC or ACB ABC N/A
CT Ratio, Phase, and Neutral None
1 to 50,000
(Increment of 1)
1 Turns
CT ratio for phase and neutral, as shown in the table above, uses turns as its unit of measure. Note that
the CT ratio can also be input as a ratio as in the example below (50:5). BESTCOMS™ will calculate
either turns or primary amps depending on which value is entered. BESTCOMS does not calculate
secondary amps.
To make the settings using BESTCOMS, select General Operation from the Screens pull-down menu.
Then select the Power System tab. Make selections for the above settings by using the appropriate pull-
down menus and buttons on the Power System tab.
Example 1. Make the following settings in BESTCOMS (refer to Figure 3-3):
Nominal Frequency: 60 Hz
Digital Signal Processing, Phase Response: RMS
Digital Signal Processing, Neutral Response: Fundamental
Normal Phase Rotation: ACB
CT Ratio, Phase: 800:5
CT Ratio, Neutral: 50:5
9289900990 Rev R
BE1-851 Input and Output Functions 3-3