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The work horse of low-impedance bus differential protection is the restrained percent differential element but many modern microprocessor relays also include an unrestrained (AKA: high-set or instantaneous) element which, when not properly applied, can cause false trips. In this paper, we explore the advantages and disadvantages of the use of unrestrained low-impedance bus differential protection...
The operational technologies that support critical infrastructure industries, such as manufacturing, transportation, and energy, depend heavily on information systems for their monitoring and control. Industrial control system (ICS) is a general term that is used to represent systems such as supervisory control and data acquisition (SCADA) systems, distributed control systems (DCS), and other control...
Transmission and Distribution (T&D) Companies tie to several generation plants and other utilities to make an electric transmission grid. Each of the interconnection facilities is governed by the Guidelines that ensure smooth operation of the Power System. However, the Interconnection guidelines are generally limited to equipment at the Point of Interconnection (POI), therefore a thorough investigation...
This paper is presenting how teleprotection applications via packet switched wide area networks can be implemented guaranteeing required application specific performance parameters. The following different approaches are analyzed for differential protection: a. ITU-T compliant standard circuit emulation (CE) using SAToP/ CESoPSN. b. A novel approach of CE technology, using explicit clocks, developed...
The critical nature of the power transmission system today makes it imperative that utilities keep up with the demand of routine maintenance of the protection system, as well as, monitoring the health of the system. In this manner, the reliability of the system can be assured. This paper will describe methods by which the system can be monitored and how the data can be used to predict the need for...
A rigorous thermal monitoring regiment is considered standard by those responsible for maintaining critical electrical infrastructure. As thermal imaging technologies mature and infrared (IR) cameras become increasingly ubiquitous, it becomes necessary to understand any limitations that may be imposed by methods that capture data infrequently. This paper will frame the benefits of thermal monitoring...
On December 23, 2015, a “temporary malfunction of the power supply” in three provinces in Ukraine resulted in power outages that lasted up to six hours and affected 225,000 customers. Following the event, an investigation identified evidence that several regional Ukraine power control systems had been compromised by cyber attacks. This was the first publicly documented successful cyber attack on an...
Static VAR Compensators (SVCs) are an increasingly common solution for power system voltage stability problems by providing rapid var support following system disturbances. From a protection perspective, an extensive protection system is typically necessary to ensure the SVC's operating range is available to provide rapid and reliable var support to the power system. SVC protection often involves...
The Duke Energy McAlpine Creek Substation in Charlotte, North Carolina, has been a test bed for smart grid and renewable generation technology since 2006. The area just outside the substation fence houses a 50 kW photovoltaic installation as well as a 240 kW, 500 kWh battery energy storage system (BESS). These two assets are connected in parallel to import and export energy to a distribution circuit...
In the spring of 2016, a fault occurred in a large single phase auto-transformer on the transmission system of a major US electric utility. The fault was cleared in a time that met standard operating speeds of both relaying and the circuit breaker but a tank failure occurred that caused the spill of a large amount of oil. Significant damage to the core and coils of the transformer also occurred.
IEC 61850 Generic Object-Oriented Substation Event (GOOSE) systems can be designed in a manner that allows testing personnel to easily identify problems and verify system functionality. This paper provides procedures and guidelines for successfully designing and integrating GOOSE protection schemes while keeping the feasibility of initial commissioning and maintenance testing in mind. The paper addresses...
Generators are expensive and important components of the power system. It is important to avoid or minimize the damage of the generator in case of stator ground faults. Traditionally, 100% stator ground fault protection on high impedance grounded generators is accomplished using the 59G and 27TN functions. The 59G function provides 95% coverage and the 27TN function provides an overlapping 15% coverage...
NERC Critical Infrastructure Protection (CIP) Reliability Standards apply to utilities that support the bulk electrical grid in North America and are meant to protect the Grid from cyber-attack. While Industrial facilities are not bound by the regulations outlined in NERC CIP a review of those regulations can help industrial facilities protect their infrastructure from cyber-attack. This paper reviews...
With proper maintenance, users of older technology electromechanical (EM) relays have considered 50+ years as the normal life cycle for these devices. When applying microprocessor relays new considerations must be taken into account for lifecycle expectations. This paper proposes to examine microprocessor relay life cycle and the sometimes unexpected costs associated with their use. During the course...
The paper is a continuation in a series that identifies more of the developing issues in relay testing - what was once well understood in a protection element's response is today a challenge in testing modern protection systems. Modern algorithms and the complexity of the combined protection element(s) scheme logic creates variable and sometimes unacceptable testing results when compared to manufacturer...
Utilities have hundreds of circuit breakers that they plan to monitor for the purpose of accurately assessing health and performance. As circuit breakers age over time, improper operations can become more likely and cause problems on the power system. Utilities are making efforts to develop automated circuit breaker monitoring systems that diagnose the electrical and mechanical health of their circuit...
According to a recent draft IEEE PC 57.156 Guide for Tank Rupture Mitigation of Liquid Immersed Power Transformers and Reactors published by the IEEE PES Transformer committee “There are combinations of arc energy, location, and duration which overwhelm the capacity of the standard pressure relief to protect the tank. It has also been demonstrated, theoretically and from field tests, that for low...
Increased demand and economic constraints often cause the power system to be operated near its thermal limits and sometimes beyond. One way to mitigate this problem is to use the thermal overload protection functions built in to today's modern IED (Intelligent Electronic Device) relays that continuously monitor the thermal load in real time. These functions (ANSI 49) use very sophisticated algorithms...
This paper is a summary of the C37.243 IEEE Guide for Application of Digital Line Current Differential Relays Using Digital Communication which has recently been developed in accordance with the following scope: This guide presents practical line current differential schemes using digital communications. Operating principles, synchronization methods, channel requirements, current transformer (CT)...
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