Transformer Bank Workshop
Voltage Phasor Diagrams

Audience:		Electrical distribution line personnel, engineers, and line supervisors
Average Training Time:		90 to 120 minutes NOTE
Format/ Product Code:		CD-ROM (MPEG Video)/ TBPHSMPG
Content Producer:		Mastery Technologies, Inc.

OVERVIEW
This course is the fourth course in the “Transformer Bank Workshop” series. All the courses in this series use full-screen, full-motion video.
It’s difficult to arrange for power outages to service power distribution systems. Your line personnel will be in situations where they have to parallel two transformer banks to transfer load from one bank to the other— avoiding an outage. To parallel banks, line personnel must be able to determine angular displacement and other facts about the bank. They can’t guess! A solid grasp of voltage phasor diagrams will help your workers understand exactly how a bank is connected, or should be connected.  
This “near hands-on” course will teach your workers how to form voltage phasor diagrams for the delta and the wye. They will combine their diagrams to represent transformations. They will also use phasor diagrams to document an existing transformer bank and to build a bank. And finally they will learn the rules for paralleling two transformer banks and how to test their connections.
The course uses clear and concise presentations, interactions, and 3D animations to actively involve your workers in the instruction and to clarify sometimes difficult concepts.
This course was produced in collaboration with Otter Tail Power Company and Gordon Solee, PE. The program is based on Mr. Solee’s popular and respected “Transformer Hands-On Workshop”.

TOPICS
The course presents interactive instruction covering the following topical areas:

The Diagram

• Forming The Delta and Wye Symbols
• Identifying the Terminals
• Practice Problems

Representing Connections

• Delta-Delta
• Delta-Wye
• Wye-Delta
• Wye-Wye
• Angular Displacement

Diagraming a Bank

• Closed Banks
• Open Banks

Building A Bank

PERFORMANCE OBJECTIVES
This course will measure mastery on each of the following performance objectives. Upon completion, workers will be able to...

Draw a phasor diagram for a delta connection

Draw a phasor diagram for a wye connection

Draw a phasor diagram for a proposed bank

1. Identify a primary connection as a delta or a wye.
2. Identify the R-Y-B phasors on a primary diagram.
3. Identify the three phasors by number according to transformer position for a primary diagram.
4. Place the arrow heads on the primary diagram.
5. Position the H1 bushings on the primary diagram.
6. Position the H2 bushings on the primary diagram.
7. Given the three voltage phasors, identify the X1 end point on the secondary diagram.
8. Given the three voltage phasors, identify the X3 end point on the secondary diagram .
9. Identify the secondary phase connections on the phasors.
10. Position the second voltage phasor in proper relationship to the first on the secondary diagram.
11. Position the third voltage phasor in proper relationship to the second and first on the secondary diagram.

Determine the angular displacement of a bank

1. Define angular displacement.
2. Identify the angular displacement of a given transformer bank as 0, 30, 180, or 210 degrees by inspecting the bank.

Construct a bank from a phasor diagram

1. Connect the primary from a wye diagram, H1 to source.
2. Connect the primary from a wye diagram, H2 to source.
3. Connect the primary from a delta diagram, H1 to source.
4. Connect the primary from a delta diagram, H2 to source.
5. Connect the primary from an open wye diagram.
6. Connect the primary from an open delta diagram.

Draw a phasor diagram for an existing bank

1. Identify a primary connection as a delta or a wye.
2. Identify the R-Y-B phasors on a primary diagram.
3. Identify the three phasors by number according to transformer position for a primary diagram.
4. Place the arrow heads on the primary diagram.
5. Position the H1 bushings on the primary diagram.
6. Position the H2 bushings on the primary diagram.
7. Given the three voltage phasors, identify the X1 end point on the secondary diagram.
8. Given the three voltage phasors, identify the X3 end point on the secondary diagram.
9. Identify the secondary phase connections on the phasors.
10. Position the second voltage phasor in proper relationship to the first on the secondary diagram.
11. Position the third voltage phasor in proper relationship to the second and first on the secondary diagram.

Define requirements to parallel two banks

1. Identify same angular displacement on both banks as a requirement.
2. Identify same voltage ratio on both banks as a requirement.
3. Identify same sequence on both banks as a requirement.
4. Identify the lighting transformer connected to the same phase on both banks as a requirement.

Describe when angular displacement must be considered

1. Cite the need to parallel two banks or substations.

Construct a bank to provide a specific Angular Displacement

1. With a given delta primary, connect a bank for 180 degree angular displacement, 120/240 volt, three-phase, four-wire.
2. With a given wye primary, connect a bank for 210 degree angular displacement, 120/240 volt, three-phase, four-wire.
3. With a given wye primary, connect a bank for 30 degree angular displacement, 120/240 volt, three-phase, four-wire.
4. With a given wye primary, connect a bank for zero degree angular displacement, 120/208 volt, three-phase, four-wire.

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