Tutorial 1: MV Transformer Failure Due to Circuit Breaker Induced Switching Transients
Abstract: Switching transients associated with circuit breakers have been observed for many years. Recently this phenomenon has been attributed to a significant number of transformer failures involving primary circuit breaker switching. These transformer failures had common contributing factors such as 1) primary vacuum or SF-6 breaker, 2) short cable or bus connection to transformer, and 3) application involving dry-type or cast coil transformers and some liquid filled. This paper will review these recent transformer failures due to primary circuit breaker switching transients to show the severity of damage caused by the voltage surge and discuss the common contributing factors. Next, switching transient simulations in the electromagnetic transients program (EMTP) will give case studies which illustrate how breaker characteristics of current chopping and re-strike combine with critical circuit characteristics to cause transformer failure. Design and installation considerations will be addressed, especially the challenges of retrofitting a snubber to an existing facility with limited space. Finally, several techniques and equipment that have proven to successfully mitigate the breaker switching transients will be presented including surge arresters, surge capacitors, snubbers and these in combination.
Presenter: David Shipp, PE – Eaton Electrical (Cutler-Hammer)
Tutorial 2: Electrical Systems Switching Procedures Considerations in Safety, Reliability and Software Applications
- Historically, finding practical methods to operate the safety procedures of LO/TO and integrity procedures for service continuity is not always easy or obvious. The tutorial addresses this difficulty.
- Studies of integrity procedures consider load flow and short circuits analysis.
- Operational procedures are integrated into software programs already in use for power systems.
- General review of lockout tagout (LO/TO) procedures for industrial electrical systems. Structure switching programs to meet safety mandates.
- Safety during system operation and maintenance and includes detailed discussion on important operational procedures, especially for non- automatic operations.
- Introduces computer based tools to assist in such important tasks with examples using current software to solve switching configuration problems.
- Early understanding of such concepts, allows the safety and reliability aspects to be embedded in the electrical design at its earliest stages.
Presenters: Erling Hesla, Giuseppe Parise, Rasheek M. Rifaat, and senior representatives of software suppliers
Tutorial 3: Grounding and Ground Fault Protection of Medium Voltage Industrial Generators
Abstract: Major and significant changes are occurring in the recommended practices for grounding of medium voltage industrial generators. This tutorial is intended to make those who own and operate industrial medium voltage generators aware of these changes and the fact that currently accepted practice will result in unacceptable generator damage for stator ground faults. The grounding changes discussed in the tutorial are being driven by in-service events where generators protected according to established practice (as outline in IAS standards) have suffered catastrophic generator ground fault damage. These events resulted in an extensive investigation by a Working Group of the IAS resulting in major recommendations in generator grounding to reduce damage and repair time. These recommendations are now being implemented into ANSI/IEEE C37.101 and C37.102 standards. The tutorial discusses the results of the Working Group investigation. Specifically it addresses: typical generator grounding practices and ground fault protection methods, damage mechanism during stator ground faults, user examples of stator ground fault damage, a new grounding method called hybrid grounding, installation experience with hybrid grounding, impact of grounding changes on system protection.
Presenters: David Shipp, PE; Eaton Electrical (Cutler-Hammer) with Chuck Mozina, PE; Beckwith Electric
Tutorial 4: Fundamentals of Micro-Processor Based Relay Protection
Abstract: Micro-processor based protective relays provide tremendous versatility. A single relay can provide all of the protective functions that previously would require a panel full of individual relays. But with the added versatility comes added complexity. Which functions should be used for a specific application? The tutorial will provide an overview of the common protective functions available and the purpose for having each of these functions. It will then provide examples of which functions would be appropriate for common applications, such as protecting a transformer, motor and distribution feeder.
Presenter: Suhag Patel, P.E., GE – Multilin