Following the title page are reports of one or more short circuit simulation. In OneLiner, the solutions are in the order they were simulated. The output for each fault begins and ends with a long line of equal signs. The electrical quantities in the report are in amperes, kilovolts, and ohms if you requested the output to be in physical units. Otherwise, they are in per-unit. All current and voltage quantities are RMS values.
Fault Summary:
The fault summary at the beginning of each fault solution contains the following:
• Fault description: This includes the fault type, fault location, outage list if any and fault impedance if non-zero. For an intermediate fault on a transmission line with tap buses, the fault location is specified by two percentages. The percentage in parentheses refers to the whole line and the other one refers to the segment.
• Fault current in the sequence and phase domain: This is the total current at the fault point.
• Thevenin impedance: This is the Thevenin impedance of the system at the fault location before the fault is applied.
• Short circuit MVA: The short circuit MVA is shown for 3-phase, 2-line-to-ground, single-line-to-ground and line-to-line faults. The short circuit MVA can be defined as (1) the product of current and prefault voltage or (2) the product of current and nominal voltage. You can state your preference in the Fault Simulation tab of the File | Preferences dialog box.
• X/R ratio: This is the complex X/R ratio at the fault location, computed using the Thevenin impedances. Here, R and X are the real and imaginary part of the total impedance seen by the equivalent positive-sequence voltage source. For example, for a single-line-to-ground fault, R+jX is given by Z1+Z2+Zo, where Z1, Z2 and Zo are the positive-, negative- and zero-sequence Thevenin impedances.
• ANSI X/R ratio: This is the X/R ratio computed according to the ANSI/IEEE standard C37. The value X is the Thevenin impedance computed using only the reactance of the network elements. The value R is computed using only the resistance of the network elements. The ANSI X/R is not shown if you elected not to compute it in the Faults | X/R Ratio Parameters dialog box.
• Ratios Ro/X1 and Xo/X1: Ro+jXo is the zero-sequence Thevenin impedance, and X1 is the imaginary part of the positive-sequence Thevenin impedance. These two ratios give a measure of the effectiveness of grounding at the fault location.
The fault summary ends with a line of dashes. A fault summary for an intermediate fault is shown below:
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2. Interm. Fault on: 6 NEVADA 132.kV - 8 REUSENS 132.kV 1L 1LG 5.00% Type=A
FAULT CURRENT (A @ DEG
+ SEQ - SEQ 0 SEQ A PHASE B PHASE C PHAS
2421.4@ -84.3 2421.4@ -84.3 2421.4@ -84.3 7264.2@ -84.3 0.0@ 0.0 0.0@ 0.
THEVENIN IMPEDANCE (OHM
1.27292+j9.86679 1.27292+j9.86679 1.43721+j11.541
SHORT CIRCUIT MVA= 1663.7 X/R RATIO= 7.85206 R0/X1= 0.14566 X0/X1= 1.1697
ANSI X/R RATIO= 79.206
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A number of bus-oriented outputs follow.
Bus-Oriented Output
The remaining output for a fault is organized by buses. The output for each bus begins and ends with a long line of dashes. The output for each bus includes:
• The bus identifiers and prefault voltage.
• Bus voltage in sequence and phase domain.
• Generator, load and shunt currents in sequence and phase domain, if any.
• Branch currents in sequence and phase domain.
The number of buses in the output depends on the tier limit you specified. If the fault solution covers more than one bus, the bus-oriented outputs are arranged by the tier number, or the proximity to the fault. Buses that are closest to the fault are shown first. Buses that are within the same tier are arranged in ascending order of the bus name.
The following is a sample output for the two buses: NEVADA and CLAYTOR. A more detailed explanation is given below.
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BUS 6 NEVADA 132.0KV AREA AA TIER 0 (PREFAULT V=1.000@ 0.0 PU)
+ SEQ - SEQ 0 SEQ A PHASE B PHASE C PHASE
VOLTAGE (KV, L-G) > 51.744@ 0.0 24.466@ 180.0 27.278@-180.0 0.000@ 0.0 77.680@-121.8 77.628@ 121.8
BRANCH CURRENT (A) TO >
28 ARIZONA 132.0 1L 130.5@ 102.1 130.2@ 108.6 90.9@ 108.9 351.1@ 106.3 52.6@ -80.6 27.2@ -87.2
8 REUSENS 132.0 1L 544.7@ 95.5 544.0@ 95.9 656.9@ 96.0 1745.6@ 95.8 110.1@ 97.4 115.3@ 98.0
7 OHIO 132.0 1L 448.0@ 106.4 446.8@ 107.0 505.0@ 107.1 1399.8@ 106.9 53.7@ 109.5 61.8@ 111.2
2 CLAYTOR 132.0 1L 424.8@ 100.4 418.5@ 103.3 498.5@ 103.6 1341.4@ 102.5 59.2@ 111.5 97.4@ 114.2
10 NEW HAMPSHR 33.0 1X 277.8@ 89.4 275.3@ 98.2 362.6@ 93.0 914.1@ 93.4 50.4@ 85.5 123.9@ 92.4
11 ROANOKE 13.8 1X
AUTO NEUTRAL CURRENT = 1477.5 @ 74.8 A
4 TENNESSEE 132.0 1P 705.2@ 104.1 713.8@ 94.7 390.0@ 97.6 1804.0@ 99.0 216.7@ -79.5 418.3@ -78.0
10 NEW HAMPSHR 33.0 1T 105.8@ 88.8 105.8@ 105.2 130.7@ 96.3 340.1@ 96.7 1.7@ 1.0 52.1@ 95.2
CURRENT TO FAULT (A) > 2623.8@ -80.1 2623.8@ -80.1 2623.8@ -80.1 7871.3@ -80.1 0.0@ 0.0 0.0@ 0.0
THEVENIN IMPEDANCE (OHM) > 9.32488@ 80.1 9.32488@ 80.1 10.3965@ 80.2
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BUS 2 CLAYTOR 132.0KV AREA AA TIER 1 (PREFAULT V=1.000@ 0.0 PU)
+ SEQ - SEQ 0 SEQ A PHASE B PHASE C PHASE
VOLTAGE (KV, L-G) > 65.423@ -1.6 11.003@-173.9 11.242@-173.2 43.515@ -5.8 76.596@-120.6 76.304@ 119.7
SHUNT CURRENTS (A) >
FROM GENERATOR 315.0@ -80.2 315.7@ -83.9 322.6@ -83.2 952.9@ -82.4 25.8@ -95.0 12.6@ 132.2
TO LOAD 94.4@ -32.0 15.9@ 155.8 16.2@ 156.5 62.8@ -36.1 110.5@-150.9 110.1@ 89.3
FROM FICT. CURR. SOURCE 110.0@ -30.3 0.0@ 0.0 0.0@ 0.0 110.0@ -30.3 110.0@-150.3 110.0@ 89.7
BRANCH CURRENT (A) TO >
6 NEVADA 132.0 1L 426.7@ -79.6 420.4@ -76.8 500.5@ -76.4 1347.2@ -77.6 59.4@ -68.5 97.5@ -65.8
5 FIELDALE 132.0 1L 68.1@ 113.4 69.6@ 100.8 55.7@ 100.6 192.3@ 105.2 5.0@ 17.3 27.2@ -56.8
4 TENNESSEE 132.0 1L 260.5@ -72.1 267.1@ -84.1 128.3@ -92.8 649.7@ -81.1 94.2@ 118.2 189.9@ 113.4
1 GLEN LYN 132.0 2L 147.8@ 101.9 146.4@ 102.3 119.0@ 101.5 413.2@ 101.9 29.1@ -73.2 27.3@ -77.9
1 GLEN LYN 132.0 1L 147.8@ 101.9 146.4@ 102.3 119.0@ 101.5 413.2@ 101.9 29.1@ -73.2 27.3@ -77.9
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1. Bus identifier and prefault voltage: The identifier includes the bus number, the bus name, the nominal kV and the area number. Buses whose name starts with the '#' character are new buses created by the program when simulating line-end and line-out faults. The new buses are given non-positive bus numbers. In the example below, the program creates the new bus #NEVADA, next to the bus NEVADA, for a line-end fault.
Buses whose name contains the '$$' characters are new buses created by the program when simulating intermediate faults. These buses also have non-positive bus numbers. See example below.
On the same line with the bus name is the tier number. Tier 0 includes the faulted bus. Tier 1 includes buses that are 1 bus away from the fault, etc.
The prefault voltage is the last item on the first line. The prefault voltage is always set equal to a fixed value at 0 degree if you requested the flat-bus-voltage option. The prefault voltage is a computed quantity if you requested the “From a linear network solution” option.
Because the fault currents are dependent on the prefault voltages, it is important that you check the prefault voltages when using the flat-generator-voltage option.
2. Post-fault voltage: The post-fault voltage of the bus is located on the line that begins with the word 'Voltage'.
3. Shunt currents: You will see a 'Shunt Currents' section if there are generators, loads or shunts attached to the bus. You will see an entry labeled "From Fict. Current Source" if: 1) there is a load or a positive-sequence shunt on the bus and 2) you are using the flat-bus-voltage option. The fictitious current source is an ideal current source whose output is required to establish a flat bus profile in the presence of shunts and loads.
4. Branch Currents: This section lists the currents flowing on all the branches attached to the bus. The current is considered positive if it flows away from the bus. You can deduce the current direction from its phase angle (with the assumption that the system is primarily reactive): The current is leaving the bus if its angle is in the vicinity of -90 degrees. The current is coming into the bus if its angle is in the vicinity of 90 degrees.
For all branches except 3-winding transformers, the branch current takes only one line in the report. For a 3-winding transformer, the branch current takes two lines. See above example for the 3-winding transformer between buses NEVADA, NEW HAMPSHR and ROANOKE. In the branch-current section for bus NEVADA, NEW HAMPSHR and ROANOKE appear on two separate lines. The current on the first line is the total current leaving NEVADA, going to the other two end buses. No current is shown on the second line.
For 2- and 3-winding autotransformers, you will see an additional entry labeled "AUTO NEUTRAL CURRENT" on the following line. This is total zero-sequence current (3Io) flowing to the ground from the transformer neutral.
For the tertiary bus of a 3-winding transformer, you will see an additional entry labeled "CIRCULATING CURRENT". This is the zero sequence current (Iot) circulating in the delta winding. The current is calculated as:
Iot = Iop * Tpt + Ios * Tst
Where:
Iop , Ios Zero sequence current at transformer P and S terminals respectively.
Tpt Turn ratio between transformer P and T terminals.
Tst Turn ratio between transformer S and T terminals.
Note: If you are simulating a close-in fault, the branch current on the faulted branch will not match that on the one-line-diagram display. The reason is that the branch current in the textual report is for a bus fault; the current in the one-line diagram is for a close-in fault in front of the relay.
5. Monitored Branch Summary: The monitored branch is the branch on which you highlighted a relay group before specifying the fault. This section shows the relay current and the bus voltage on the two ends of the branch. At the end of the summary are some derived quantities such as 3Io, Va/Ia, etc.
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MONITORED BRANCH: 6 NEVADA 132.0KV -> -8 #REUSENS 132.0KV 1L
+ SEQ - SEQ 0 SEQ A PHASE B PHASE C PHASE
RELAY CURRENT (A) 1604.2@ -79.8 1604.2@ -79.8 1604.3@ -79.8 4812.8@ -79.8 0.1@ -81.5 0.1@ -81.5
BUS VOLTAGES (KV, L-G)
6 NEVADA 132.0 51.637@ 0.1 24.574@ 179.7 27.064@-179.5 0.000@ 0.0 77.802@-121.5 77.168@ 121.7
-8 #REUSENS 132.0 51.634@ 0.1 24.576@ 179.7 27.066@-179.5 0.007@ 164.1 77.802@-121.5 77.168@ 121.7
3Io= 4812.9@ -79.8 A Va/Ia= 2.25e-015@ -90.7 Ohms (Va-Vb)/(Ia-Ib)= 16.2@ 138.3 Ohms
(Zo-Z1)/3Z1 = 0.0000 @ 0.0
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