The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
Ferroresonance is a widely studied phenomenon but it is still not well understood because of its complex behavior. It is “fuzzy-resonance.” A simple graphical approach using fundamental frequency phasors has been presented to elevate the readers understanding. Its occurrence and how it appears is extremely sensitive to the transformer characteristics, system parameters, transient voltages and initial...
The application and connection of current transformers for electromechanical differential circuits creates vulnerability for mis-operation under rare but identified scenarios. As a lesson learned from a real-world incident, discovery of the vulnerability occurred during the investigation of a generating unit trip from a nearby switchyard fault immediately outside a generator step-up transformer (GSU)...
This paper discusses the potential misoperation of a high-impedance bus differential relay when surge arresters are located within the relay zone of protection. Transient overvoltage caused by a circuit breaker restrike during shunt capacitor bank de-energization can cause the surge arresters to conduct. The relay interprets the current flowing through the surge arrester as fault current within its...
These new test methods are a new tool that can be used to verify the stability of differential relays for external faults. By simulating real time events, one can discovered errors that were not possible using single phase test methods. As a result, it is encouraged that new microprocessor relays be tested as close to real system events as possible.
Distance relays provide good dependability for bolted faults but they can face problems detecting resistive faults, specially in short lines. The fault resistance can also affect the security of the relay.
Accurate fault location in distribution networks of power systems is an essential technology, yet faces more challenges than that in transmission systems. This paper presents a novel method for feeder fault location using current/voltage sensors sparsely deployed in the network. Depending on the available sensor locations relative to the fault and the lateral conditions, the algorithm searches every...
This paper reviews the application of multi-function motor protection relays to motors that are connected by variable frequency drives (VFD). Typical VFD internal motor protection functions are reviewed to understand the required roles of external motor protection relays. Applications discussed include protection requirements when the relay is located on the source side of the VFD and the motor side...
Distribution Automation (DA) is part of today's evolution of the distribution system. Many utilities already have some Distribution Automation applications (e.g., remote controlling of feeder switches and breakers, automatic reconfiguration, fault detection, fault location, voltage and reactive power control, Advanced Metering Infrastructure (AMI), etc.) and the trend is undeniable and expanding.
This paper discusses the increasing interest in performing End to End testing on modern protection systems. There are many and varied approaches to this test method, from simplistic to overly complex. What is really required and what really makes this test method valuable? What are the technical challenges and how to resolve them? These and other questions are answered. This paper makes a comparison...
This paper presents a review of powersystem synchronization. When two sources are paralleled, it is crucial to close the interconnecting circuit breaker when both sources are in voltage, frequency, and phase coincidence.
Choosing the right number and configuration of test access points is a necessity for smooth maintenance and testing operations throughout the usage time of a panel.
This paper is a summary of an IEEE/PES Power System Relaying Committee (PSRC) report [2] on the design and testing of selected System Integrity Protection Schemes (SIPS). The report includes high level general considerations in SIPS design and testing, and the industry practice in design and testing of the following selected SIPS with example implemented schemes: (1) Generator rejection; (2) Load...
Delta-Wye transformer connections create discontinuities in the zero-sequence network as the zero-sequence current can flow at one side of the transformer without flowing at the other side. This effect generates a zero-sequence differential current that can make the differential unit trip. Traditional solutions applied to remove the zero sequence differential current where based on delta connected...
Modular protection and control using process bus is really only the first step in modular design of substations. Once the field wiring problem for protection and control systems is solved, then the design of substations can be addressed. Some examples of where the industry can go when are as follows.
We have discussed many practical aspects of directional comparison blocking schemes; its basic implementation with PLC, the pros and cons of non-directional vs. directional starting, coordination time of blocking signal and FP tripping elements, carrier holes, and as well a few of the multitude of implementations seen in practice. We have shown the complexities and necessary considerations for the...
Deploying line current differential protection over Ethernet packet switched transport is more than just making the connections, as the application demands certain deterministic characteristics from the communication channel. Packet switched traffic by its very nature of statistical multiplexing is subject to variances in propagation time due to queuing delays, which can impact the performance of...
This paper briefly describes line current differential schemes, and focuses on their dependencies on communication channels. Dependencies on bit error rate and transmission latency are discussed. Effect of time synchronization accuracy on sensitivity of line current differential scheme is explained in details. Types of communication channels are discussed including dedicated, multiplexed and packet-based...
The integrity and reliability of the bulk power electrical systems could be significantly enhanced by providing redundant or back up protection for the bus differentials, unit differentials, feeder differentials, and transformer differentials applied in generating station high voltage switchyards. These additions could be provided at a modest cost as outlined in the paper. Many existing large generating...
Differential protection is often touted as being The protection for generator stator windings. In this paper, we examine the degree of protection afforded by the various types of differential elements (phase, negative, and zero sequence) for stator winding faults.
Very few devices are currently installed in substations without some form of communications connection. There is a clear trend toward establishing data connectivity via Ethernet due to generally higher data rates, and cost effective connections. Whether an application is for Supervisory Control and Data Acquisition (SCADA), line relaying, remote engineering access or Synchrophasors, the Intelligent...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.