Relay Channel


9:30 AM–10:15 AM 
The Importance of Overexcitation (V/Hz) Protection for Power Transformers and Generators

Speakers: Drew Welton, Intellirent


In this session we will discuss the importance of overexcitation, or volts per hertz protection of generators, and generator step-up transformers. We will discuss how this potentially catastrophic event can occurs, discuss the coordination of settings, and overall applications based on IEEE, and NERC recommendations and requirements. We will also examine an event capture from an actual overexcitation event.

10:30 AM–11:15 AM
When to Repair/Replace/Upgrade Electromechanical Relays

Speakers: Bruce Horowitz, American Electrical Testing Co., LLC


Electronic relays have been in existence since the early 1980s.  Their popularity and large usage did not occur until the 1990s and early 2000s.  Electromechanical relays have been the staple relay to utilize before the popularity of the microprocessor-based relays.  Many of the electromechanical protective systems, easy 40 and 50 years of age are still in service.  These relays have moving parts, springs, dials and other components impacted by usage and age.  Many have started to fail requiring replacement.  Like in kind replacement relays are either difficult to find or very expensive.  Users (customers) have difficult decisions to make; replace with like in kind or upgrade to microprocessor-based relays.  This document will discuss the pros and cons and some of the costs and issues associated with either repairing, replacing or upgrading from electromechanical relays to modern microprocessor relays.

11:30 AM–12:15 PM
Electromechanical Differential Relays Misoperation and Investigation

Speaker: Alexandro Rangel Werdene, Saber Power Services


Transformer differential protection systems extend the life of the protected transformers and increase the overall reliability of the system. However, lack of, or improper commissioning might cause undesired operations and partial or full blackouts. Successful commissioning of a system requires testing of all new circuits, including instrumentation devices. This paper provides the analysis of a transformer differential protection scheme of two 25 MVA, 138 kV / 12.47 kV transformers feeding a Main – Tie – Main scheme and how improper commissioning of a newly installed tie breaker caused a full outage at this industrial facility.

2:15 PM–3:00 PM
Testing Philosophy: Past, Present, and Future

Speaker: Scott Cooper, OMICRON electronics Corp. USA


Details coming soon.


3:15 PM–4:00 PM
How CT and VT Connection Errors Affect Protection

Speakers: Karl Zimmerman, SEL

Validating proper CT and VT wiring, terminations, and grounding is fundamental to successful performance of the protection system. Occasionally, errors in CT and VT connections can occur, like missing or broken neutral wires, multiple or missing ground connections, physical wiring errors, blown potential fuses or failures within the instrument transformers. These errors can lead to undesired operations of the protection.

This paper reviews fundamentals of CT and VT connections. We then show several actual field events of undesired or unexpected relay performance due to problems in the CT or VT circuit. These events include transmission line protection with distance and directional elements, high-impedance bus differentials, transformer differentials, and distribution feeders. We shall discuss several basic and advanced testing and commissioning approaches that can reduce errors and improve protection performance.

4:15 PM–5:00 PM
Implications of an Improperly Installed On-Load Tap-Changer and Protection Considerations

Speakers: Alexandro Rangel Werdene, Saber Power Services

Details coming soon.