CAEDS - Customer Aspects of Electric Distribution Systems
Who Should Attend?
It is imperative that managers not send people to this class who do not have formal electrical training in the form of PTS's Electric Utility System Operation (EUSO) class, or an engineering degree, an electronics degree, or completion of an apprenticeship program.
The CAEDS class is targeted to those employees who have direct customer contact and their support staff. This includes those in marketing, sales and customer service. (This class is not targeted towards those individuals who are responsible for the utility's distribution system such as line and ground crews, substation crews, designers and construction crews. PTS's 2-day Electrical Distribution Systems class is designed for these groups.)
The CAEDS class assumes a solid understanding of the generation, transmission and distribution aspects of a utility including both theory and actual practices. In particular, it assumes an in-depth understanding of transformers and how current flows in a 3-phase system.
What Does the CAEDS Class Cover?
The first day of the CAEDS class covers the electrical system on the utility side of the meter. The second day of the class covers the electrical system inside the customer.
The CAEDS class begins with the utility's distribution system where the EUSO class ends. It covers the various systems that a customer might request including single-phase 120/240, and 3-phase systems that include 120/240 delta, 120/240 open delta, 208Y/120, and 480Y/277. It covers the principles behind selecting a service including the advantages, disadvantages and limitations of each of the services. In the open delta system, the wild leg (also called the power leg, the bastard leg, the stinger, and the high leg) is described including the danger it poses to customer equipment. The reliability aspects regarding transformers connections include open neutrals that result in high voltages that destroy electronics, and stray voltages associated with bad connections and with bad grounding.
The details of both overhead and underground distribution systems are covered. Particular emphasis is placed on the necessity of shield cables above 5 kV. Various types of shielding are described including concentric neutrals. The design concept behind an open-loop underground distribution system is described showing how it can be used to quickly and easily isolate faults and then restore power to customers. The role of fault-current indicators is emphasized in this process.
The design philosophy behind ground fault circuit interrupters is described and how they can cause customers numerous headaches until they realize how they operate, and how they are connected.
Faults are explained. Students see how fault current can be many times more than normal full load current. The role of transformer impedance in determining fault current is covered in the area of fault current studies. Equipment fault current bracing is covered.
Surges caused when disconnecting underground cables is fully described, along with MOV arrestors that can be used to protect against these surges.
Once the utility's part of the distribution system is covered, the course moves into the customer's facility and covers the customer's equipment.
It begins with motors and motor controls. The various types and applications of AC motors are described with emphasis on the most common type, those with squirrel cage rotors. The application criteria for synchronous motors is described as well as how these motors can be used instead of capacitors for power factor correction.
DC motors are also covered included their unique applications. The method of control DC motor speed is provided. AC motor controls include full-voltage starting and various types of reduced-voltage starting.
Variable frequency drives are fully covered including the operations of the electronics that produce the variable frequency and how varying frequency varies motor speed. The risk of motor failure when applying variable frequency controls to an older motor is also discussed.
In addition to covering the electronics used in variable frequency drives, the electronics used in AC to DC conversion, and in other key industrial and large commercial electrical systems are covered. Once the electronics are covered, the reliabililty aspects associated with the electronics are described. Particular emphasis is placed on the harmonics caused by high-speed electronic switching in equipment such as computers, fax and copy machines, dimmers, electronic ballasts in lighting fixtures and variable speed drives.
Other reliabililty includes sags, swells, blinks and flicker. Remedies to these problems include UPS systems, harmonic filters, isolation transformers and superconductor energy storage systems.
The class ends with state of the art technology including written pole motors, microturbines and fuel cells. Application of these technologies includes the economics of decision making.