Unsymmetrical Fault Analysis 2

Unsymmetrical Fault Analysis 2

1.0 Introduction

Lets disown the basic looks in using symmetrical components for assessing faultinged conditions ( both quantities argon assumed to be in pu).

A. For positive, negative, & zero sequence:
1. breach the sequence mesh topology for the system under analysis.
2. Obtain the Thevenin equivalents looking for into the network from the fault point.
B. Connect the networks to capture the influence of the position fault type.
C. Compute the fault authorized from the circuit resulting from clapperclaw B.
D. From step C, you will also determine the currents in all triple of the networks (positive, negative, and zero sequence currents). This enables computation of the phase currents Ia, Ib, and Ic from Iabc=AIS.
We now have the necessary background on growth the sequence representation of each component in the network (loads, lines, transformers, and generators). Step A-1 is completed by connecting this representation in a manner consistent with the network 1-line plot.

We now investigate step A-2.

2.0 Obtaining Thevenin equivalents

The first thing to do is to draw all three sequence networks of the system to be analyzed, using information from the one-line diagram together with the component sequence models.





Then identify the fault location in each of the three sequence networks.

Then, for each of the three sequence networks, determine the Thevenin equivalent of the network as seen from the fault location.

Recall we
? Obtain the Thevenin impedance by faineance all sources (short constant voltage sources and open constant current sources) and computing impedance see looking into the network from the coveted location, and
? Obtain the Thevenin voltage by computing the voltage at the open-circuited terminals for the desired location.

Example:
Consider the system of Fig. 1.
[pic]
Fig. 1

The transformer is ?-Y grounded with rated line-to-line ratio of 13.8 kV/69 kV and power rating of 5 MVA. The...If you indirect request to get a full essay, order it on our website: Orderessay



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