Block N - Power System Operation

Objectives

Power up and operate a small interconnected power network.
Develop and test an emergency plan for preserving the small network following an outage.

Background

In the previous experiments, we have studied many of the individual elements that make up a power system. Basic elements such as resistors, capacitors, and inductors are part of many power systems. The machines we have studied, DC machines, and single-phase and three-phase AC induction machines, are also present in most power systems. In this lab we will put many of these elements together to form a small power system.

A system is just a group of interconnected elements that work together in some fashion. If you think about it, you can probably name a number of different types of systems. Computer systems, biological systems, communication systems, power systems, etc. are all examples of different systems.

Power systems come in many different sizes and shapes. Some small power systems would include the supply network in a building, the network in your car, the power system on a airplane, and our lab system. The power systems that typically come to mind are the large ones. Did you know that all of the United States, plus much of Canada and part of Mexico are all interconnected in one large power system?

Interconnection provides a means for selling power from one location to another and helps to keep the system frequency very close to constant. It also means that one company can seriously affect the other. During this lab, you will see how interconnected power companies can affect each other and get a taste for some of the problems they may encounter.

Overview of The Alphabet Companies Power Pool

3 Power Companies: A, B, and C
Equipment Resources by Company

- Company A
2 Power Generation Plants
1 Transmission Line
2 Harmonic Analyzers
Various switches and meters

- Company B
1 Power Generation Plant
1 3-phase Induction Motor Load
3 1-phase Variable-Resistance Lighting Loads
2 Harmonic Analyzers
Various switches and meters

- Company C
1 Connection to External Power Grid
1 Transmission Line
2 3-phase Induction Motor Loads
1 3-phase Resistance Loads
1 3-phase Capacitor Bank
1 3-phase Transformer Bank
2 Harmonic Analyzers
Various switches and meters
Job Descriptions

Power Plant Engineers
In charge of operating generator.
In charge of synchronizing.
Keep it safe from overload.
Find ways to make sure it sells power.

Transmission Engineers
Keep line safe from overload.
Oversee connection to other companies.
Communicate with other companies.

Operations Planning Engineer
Oversee emergency plan.
Coordinate engineers in your company.
Communicate with other companies.
Monitor and control loads.
Monitor grid connections.
Personnel Resources by Company

- Company A Personnel
2 Power Plant Engineers
1 Transmission Engineer
0-1 Operations Planning Engineer

- Company B Personnel
1 Power Plant Engineer
1 Transmission Engineer
2-3 Operations Planning Engineers

- Company C Personnel
1 Transmission Engineer
2-3 Operations Planning Engineers
Government & Regulating Agencies (Role played by Lab Instructors)
All are responsible for personnel SAFETY FIRST!
All are responsible for equipment safety second.
Goal of companies with generation is to sell as much power as they can safely.
Goal for loads is to stay online as much as possible, have a high power factor, have the three phases balanced, and have a low THD.

Discussion and Calculations

Read the introductory material and the descriptions of the "Companies"
Review the job descriptions & tentatively decide which you'd prefer to be.
Write down some ideas for an emergency plan.
- What factors should you consider?
- Should you worry about the other companies?
- How can you keep your customers happy?

Instructional Activity in Class

Stage 1: All companies do the same things

Pick a name for your company that starts with your company's letter
Pick jobs for each person in your company. Fill positions in order listed. Review each person's responsibilities
Identify equipment and verify your company circuit diagram. Familiarize yourselves with the overall power pool diagrams.
Determine and record the rated values of all of your machines, loads, and lines.
Develop an emergency plan.

Put it in writing

Assume your company is up & running and connected to the system.
How will you disconnect if needed?
How will you decide you need to disconnect?
Who will monitor critical variables?
Who will be responsible for which switches?
Make sure your company is disconnected from all the other companies.
Get instructor permission before powering anything up.

Stage 2: Each company follows individual instructions

Company A: - Review Block M material on synchronous machines; - Bring both DC machines up to 1800 rpm.; - Make sure CB connecting the generators is open (off).; - Turn on DC supplies to the fields of the synchronous machines. Bring the AC voltage output from your generators up to 114 Volts line-to-line.; - Check the synchronizing lights. If your phases are connected correctly, they should go on and off in unison. If they do not, power-down both plants and switch any 2 generator leads on one side only.; - Adjust the field voltage and DC machine speed as necessary to get all lights to go on & off slowly. When all of the lights are out, the voltage across the lights (& the switch) is approximately zero, so the switch can be closed safely.; - When all of the lights are out, close the CB. Make sure to monitor your generator speeds, currents, and voltages to make sure they are operating safely. All variables should remain close to constant with no major oscillations or surges.; - Note the synchronizing lights on your transmission line. Is the phase sequence correct? If not, coordinate with Company B for one of you to shut down & switch 2 of your generator phases.; - Since you have no load, your only way to make money (sell power) is by passing power through the transmission line. Discuss ways you can control the amount of power that flows in your line.; - Wait until Company B is ready to synchronize.; - Work with Company B to adjust voltages as necessary to synchronize and close the line that connects you. Try to keep your voltages as near to rated as possible.; - Once Companies A & B are connected, try your plan to increase the flow on your transmission line. Try to keep the current load evenly divided between your two generators at all times. Also keep the generator output voltages equal.; - Once Company B has the lighting load balanced, work with them to prepare for synchronization with Company C. Your frequency must be 60 Hz and the voltage must match that of the low side of Company C's transformer bank. You may need to adjust the speed of your machines to get the frequency up to 60 Hz. Make sure all generators in A & B are operating at the same speed. You may need to turn off the lighting load if you can't get the voltage high enough with it on.

Company B: - Review Block M material on synchronous machines; - Bring your DC machine up to 1800 rpm.; - Make sure CB connecting the generator to the grid is open (off).; - Turn on DC supply to the field of the synchronous machines. Bring the AC voltage output from your generator up to 114 Volts line-to-line.; - Close the CB to bring your generator online.; - Your induction motor load is rated at about 1 A and your lighting load is rated at 0.5 A. Can your generator supply both of these loads at the same time?; - Turn on your induction machine. Measure and record the current it draws.; - Adjust your generator field to get the AC voltage back to 114 V line-to-line. Can you get to 114 V? If yes, leave the induction load online to synchronize to Company A. If not, disconnect it until you are connected to Company A.; - Note the synchronizing lights on your transmission line. Is the phase sequence correct? If not, coordinate with Company A for one of you to shut down & switch 2 of your generator phases.; - Wait until Company A is ready to synchronize.; - Work with Company A to adjust voltages as necessary to synchronize and close the line that connects you. Try to keep your voltages as near to rated as possible.; - Once Companies A & B are connected, turn on your induction load (if needed) and your lights. Adjust the knob to get all three currents balanced. Record the current levels, note the current waveshapes, and record the THD at balanced conditions.; - Once you have the lighting load balanced, work with Company A to prepare for synchronization with Company C. Your frequency must be 60 Hz and the voltage must match that of the low side of Company C's transformer bank. You may need to adjust the speed of your machines to get the frequency up to 60 Hz. Make sure all generators in A & B are operating at the same speed. You may need to turn off the lighting load if you can't get the voltage high enough with it on.

Company C: - Turn on your connection to the KSU grid.; - Turn on your induction loads. Measure & record total company pf, P, and I.; - Turn on your resistor load. Measure & record total company pf, P, and I.; - Turn on your capacitor bank. Measure & record total company pf, P, and I.; - Turn off your resistor load. Measure & record total company pf, P, and I.; - Discuss how you could improve your pf even more.; - Measure the line-to-line voltage at the low side of your transformer bank with a harmonic analyzer and report the value to Company B.; - Work with Companies A & B to synchronize to their grid.

Stage 3: Each company follows individual instructions

Company A:: Work to bring the flow on line B-C to near rated. Record the state of each element in your system in terms of I, V, P and pf.
Company B:: Work to bring the flow on line A-B to near rated. Record the state of each element in your system in terms of I, V, P and pf.
Company C:: Record the state of each element in your system in terms of I, V, P and pf.

Stage 4: Everyone prepare for an EMERGENCY!

Conclusion

Discuss the questions asked of your company in the lab procedure
Summarize and discuss your company's emergency plan, how well it worked, & how it changed after the emergency.
Describe what happened to your company during the emergency.
Give at least one way in which your company could be improved by adding additional equipment or by redesign or reconnection of existing equipment.
Describe any additional observations you made.