Classes

Harlow Engineering Associates offers two classes:

LTC Control and Transformer Paralleling

The control of LTC Transformers and Step-voltage regulators evolved from electromechanical, to electronic analog, to digital in the span of 40 years. As a result, most users now operate with a mix of controls produced by many vendors representing varied technologies. The material presented in this class is unique for its study of controls without bias for any particular product. The class is structured for student discussion of many important topics such as:

? The basis of line drop compensation and the realities of using it ... considerations for when shunt capacitors are involved on the feeder.
? Operational differences in analog and digital controls ... how setpoints may differ.
? Arguments for updating old controls with new digital controls.
? SCADA communications ... using the LTC control as the sensing point.

The paralleling of LTC power transformers is commonly understood to be practical only with “identical” transformers … so what constitutes identical and how can dissimilar transformers also frequently be operated in parallel? In this section the student will become familiar with several alternative methods of paralleling, most especially the circulating currrent method as is
used about 90% of the time in U. S. installations. Discussion of other techniques includes the long neglected Negative Reactice method which for some has been found to be a very cost effective alternative.

Class instruction and notes treat the following topics:

Basic Control: Common system configurations, control voltage and current inputs and phasing considerations, bus and line regulation, line drop compensation.
Extended Control: Voltage limit control, voltage reduction control, reverse power flow operation - differences for transformers and regulators, SCADA communications.
Paralleling Control: Master-follower, conventional circulating current, equal power factor circulating current, negative reactance, VAr matching. Detailed analysis of the common circulating current method (used in about 90% of U. S. installations); trouble shooting of field installations.
Tap changer technologies: Resistive, reactive and vacuum types.

This 12 hour class is structured for engineers and senior technicians. It is in discussion format and includes numerous student “quizzes” which are designed to have those being trained satisfy themselves as to their level of knowledge – distinctly not to be a grading or pass/fail criteria. All participants are rewarded with a certificate attesting to participation in the course; this often becomes part of a company record of the individuals’ training. It has been qualified for PDH requirements for professional engineering continuing education, depending on particular state requirements.

Step-voltage Regulators - Principles, Construction and Application

There are some aspects of the design of a regulator which are confusing to many users, e.g., why does a ±10% regulator test at more like ±10.5%, or perhaps not even the same nominal range in buck and boost and why are some regulators Type A (“straight”) and others are Type B (“inverted”)?
Should a user be concerned?

What about the installation? The topic of by-passing is critical. Many line personnel report having witnessed a case of bypassing an energized regulator while off Neutral where the regulator was destroyed but no one was hurt. But what happened in particular cases when the operator was badly burned or, in-fact, killed?

Often the topic of most interest to operators is that of the new digital controls now supplied as standard on all regulators. Some are so frustrated with all of the operational, metering and communications capability that they really wish it were not there. But consider: Digital controls are much more accurate than predecessor models and give a great deal of extra capability at no additional cost. Discussion will include this capability and how it may be usefully applied. The class will contrast the operational aspects of the major vendors’ products.