ABB COM600 series User's & Technical Manual page 19

1MRS758734 COM600 series 5.1
Substation Analytics Technical Manual
In case of evenly distributed load, Equivalent load Dis ~ 0.5. When the load is tapped
at the end of the line, Equivalent load Dis = 1.0. If nothing else is known, a good initial
guess for Equivalent load Dis is 0.5.
When "Load modelling" algorithm is used, the user can select with the EF algorithm
current setting whether the I0 or I2-current based algorithm is used. The difference
between I0 and I2 is that I2 does not require the settings Ph capacitive React and Ph
leakage Ris. In case of I0, these settings are required in order to compensate for the
influence of line charging capacitances. This typically improves the accuracy of a fault
location estimate when fault resistance is involved in the fault.
Under certain restrictions, the EF algorithm Sel value "Load modelling" can also be
applied to unearthed networks. In these networks, the ratio of the earth-fault current
magnitude to the pre-fault load current magnitude is calculated.
Based on simulation and field tests, when Rfault = 0 ohm, the calculated
Figure 4.3-11 (Equation 8)
The low ratio affects also the validity estimate of calculated fault distance, which can
be read from the EF_VALIDITY output. Sufficient fault current magnitude can be
achieved, for example, with proper switching operations in the background network,
which increases the fault current. After the switching operation, a re-energizing of the
faulted line is done and a new estimate obtained. The fault resistance decreases the fault
location accuracy and it should not be too large, maximum a few hundreds of ohms.
The range of the setting Equivalent load Dis is 0.01...1.00. Any value of S_CALC outside
this range needs to be ignored.
Fault loops "AB Fault", "BC Fault" or "CA Fault"
Fault loops "AB Fault", "BC Fault" or "CA Fault" are used for phase-to-phase short
circuit faults as well as in the case of a phase-to-phase-to-earth fault if the individual
earth faults are located at the same feeder. Figure 4.3-15 shows the measured impedances
Figure 4.3-12 (Equation 9)
equation_8.png
equation_9.png
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