Assignment: PROTECTION PROJECT

1. Problem and Report

Enclosed as Figure 1 is a diagram of an Arizona looped 230 kV transmission system which is typical of a system serving a large city. There is remote generation whose power is input to the loop over 2 - 345 kV lines. The voltage is transformed from 345 kV to 230 kV by 3-phase transformer banks T3 and T4. Transformer T1 and T2 step the voltage up at the remote generating site. Figure 2 is a single line diagram of the 230 kV and 345 kV systems, including the series impedance. Note that the data is in per unit on a 100 MVA base, 230 kV and 345 kV bases. The generator and transformer data is given in Section 2.

The Project is divided into 3 parts as follows:

1.0 Build the above system using PowerWorld

Build a simulation of the above system using PowerWorld.

1.1 Time-Over-Current Relay Scheme for a 69 kV Radial System

Design a coordinated time-over-current relay scheme for the radial 69 kV system shown in Figure 3. This radial system is connected to bus 5 of the system shown in Figures 1 and 2. The 69 kV structure configuration and line data is shown in Figure 4. Assume the zero sequence impedance is three times the positive sequence impedance. For minimum fault current calculations assume that the line from bus 5 and bus 9 is out.

Include:

The necessary short circuit studies.

The breaker ratings for B11-B13.

The CT ratios associated with B11-B13.

The tap and time dial settings for CO-8 relays associated with B11-B13.

The basis for the selections in the form of a report.

Figure 4. 69kV line layout.

1.2 Distance Relay Protection System

Design a distance (impedance) protection system to protect the 230 kV line between busses 5 and 9 and to provide remote backup protection for line from bus 5 to bus 6. The 230 kV lines have 954 KCM ACSR conductors. You will need both an impedance ground fault relay and an impedance phase relay. Use mho units.

Include:

Circuit breaker selection.

Instrument transformer selection and connections.

Relay selections and settings.

Validation of your settings for all fault types by calculating the apparent impedance at bus 9 from computer studies for faults at bus 5. Revise your initial settings, if required.

The basis for the selections in the form of an engineering report.

Pertinent computer studies.

2. Generator and Transformer Data

Gen. No.      MVA          kV___    ____x"d=X₁=X₂__    _____x₀______      Connection
      1          333         22kV          .08 pu                       .10 pu                       Note 2
      2             "              "               "                                "                              "
      3          210         230kV       .14 pu (Note 1)         .24 pu (Note 1)         Note 3
      4            "             "                "                               "                              "
      5            "             "                "                               "                              "
      6          353           "             .34 pu (Note 1)         .28 pu (Note 1)             "
      7            "             "                "                               "                              "

Notes:

1. This impedance includes the step-up transformer impedance on the generator MVA bases.

2. Ungrounded wye for generators 1 and 2.

3. Assume generators are connected grounded wye and the generator step-up transformers are connected grounded wye - grounded wye.

Transformers:

Transformers 1 and 2 are 3-phase rated at 350 MVA, 22 kV delta to 345 kV grounded wye, 8% reactance.

Transformers 3 and 4 are 3-phase rated at 400 MVA, 345 kV grounded wye to 230 kV grounded wye, 6% reactance

The template for the report is included in a separate file. Include all the material asked for in the project in the provided template.