Power Systems Analysis
The reliable and efficient operation of a power system — from a low voltage commercial system serving less than 100kW to a high voltage transmission system delivering hundreds of megawatts — requires a thorough understanding of how the system will perform in both normal operation and during contingencies. The proper and thorough analysis of power systems is required, in both the design and operation stages, in order to maximize safety, reliability, and performance all while minimizing cost.
Because power systems consist of the interconnection of thousands of individual components — transformers, transmission lines, capacitors, voltage regulators, insulators, surge suppressors, switches, and a variety of loads — the analysis of such systems requires an expertise in both the individual components as well as in the complex interaction of these components to form an interconnected system. This requires the proper application of engineering fundamentals developed over a hundred years ago as well as the latest in software tools to quickly and accurately understand complex systems.
ELECT, P.C. has the expertise, experience, and tools to accurately analyze power systems from the design and planning stage to failure analysis, and from the smallest coordination problem to complex transmission loadflow and stability issues, generator interconnection and control, transient disturbances, protective relaying, and more. ELECT, P.C. has developed an expertise and broad experience base in the following areas:
Short Circuit and Protective Coordination
Regardless of how well a power system is designed, built, or maintained, all power systems are vulnerable to faults. This may be due to aged or worn equipment in an industrial facility, or a storm-related fault on a utility feeder. A faulted system usually, but not always, results in a relatively large short circuit current.
Regardless of the nature of the fault, the reliability and safety of an electrical system requires an understanding of how that system will perform when a short circuit occurs, and a system that is designed and configured to properly respond to the fault.
A properly coordinated system will respond to faults by:
- interrupting the fault current to limit equipment damage and minimize hazards to people, and
- minimize the portion of the system that is impacted by the fault.
Utility Distribution Sectionalizing Studies
A utility distribution system differs significantly from an industrial distribution system in several aspects — the loads are more distributed, circuits are constructed and grounded differently, the fault exposure is greater, and there are cold load and reclosing issues.
Consequently, the protection of a utility distribution feeder is more involved than for an industrial feeder as the engineer must not only coordinate overcurrent devices, but also optimize device location and consider several other factors such as reclosing intervals, outage exposure, distributed generation, and utility service philosophies.
ELECT, P.C. has performed numerous utility distribution sectionalizing studies on a wide variety of systems. We have been successful in helping several utilities improve system reliability by implementing improved sectionalizing schemes. ELECT, P.C. has also assisted in sectionalizing studies which incorporate the use of distribution automation, distribution circuit ties with multiple settings groups in microprocessor based controls and fast bus transfer schemes for sensitive large industrial customers.
Load Flow Studies
The function of a power system is to supply distributed loads with energy in a usable form. When a power system grows in scope or serves additional loads, its ability to maintain a stable, acceptable voltage at all of its load locations may be compromised, and portions of the system may become overloaded or unstable. Solutions to loadflow problems may involve the replacement of equipment, installation of capacitor banks, remote generation, the use of voltage regulators, or other solutions. ELECT, P.C. utilizes both internally developed as well as commercially available software to solve these complex problems.
Where multiple generators are applied on a large or isolated system, the response of the system to a fault must be understood so that the overall system returns quickly to a regulated, steady state condition. Dynamic stability analyses allow the modeling of systems in order to predict system performance under various conditions. The results of these analyses can be used to assist to making recommendations for protective relay settings or simply to determine if a design concept is sound. ELECT, P.C. uses commercially available software to perform dynamic stability analyses.
Arc Flash Risk Assessment
Recently, the hazards associated with electrical arcing events have come under new scrutiny in order to reduce the number of injuries and fatalities associated with these events. An arc flash is a sudden, explosive release of energy that results when a temporary short circuit initiates the formation of a plasma that dissipates large amounts of energy is a short time. Until a protective device operates, energy may be released in the form of extreme heat, sound, and shock, creating an extreme hazard to unprotected workers in the immediate vicinity.
Per the National Electrical Code, an arc flash risk assessment is required to be performed for electrical equipment that is likely to require examination, servicing, or maintenance while energized, in order to warn qualified persons of potential electric arc hazards. NFPA 70E requires that such equipment be labeled with specific information relevant to the potential hazard.
The purpose of an arc flash hazard analysis is to determine the incident energy to which a worker might be exposed during an arc flash event, to establish an arc flash boundary, and to determine a worker’s required personal protective equipment (PPE). The PPE is intended to provide a level of protection against arc flash burns, shock hazards, and eye and hearing damage. The use of the required PPE does not necessarily provide protection against all burns, but any burns experienced should be survivable.
ELECT, P.C. also provides personnel training, both awareness training for general employees and qualified worker training for electrical personnel. Arc flash hazard training is a key component of an overall safety program for your employees.
ELECT, P.C. provides complete substation design services, encompassing the entire process from conceptual design to equipment specifications, final BOMs, construction drawings, and commissioning and testing services.
ELECT, P.C. has designed over 50 complete distribution substations, ranging from 15kV, 5MVA to 230x115kV 50MVA.
Protective Relaying Design
Protective relays have been called the “silent sentinels” of the electric power system. As such, these devices continually monitor the electric power system for abnormal events and issue trip signals to breakers to isolate faulted portions of the system while minimizing damage and downtime for other equipment. The proper design of a protective system is the first step to ensuring appropriate system protection.
ELECT, P.C. has designed protective relaying systems for utility transmission, substations, distribution and generation. We have also designed numerous large scale industrial protective relaying systems. ELECT, P.C. has the expertise to design a protective relaying system that ensures equipment is well protected.
Relay Panel Replacement
Historically, the relays that provide critical protection to electrical distribution circuits, generators, and industrial customers were of an electromechanical design. In the mid-1980’s and 1990’s solid state protective relays became the preferred solution. Both of these designs are often nearing the end of their service life, are unreliable or inaccurate, and/or lack desired functionality. Microprocessor based relays are now the preferred solution, offering not only increased reliability, but also, far greater capabilities for monitoring, control, and analysis.
ELECT, P.C. can provide a turn-key replacement for outdated systems – we will analyze an existing protective relay system and design a new, completely tested system that provides superior protection, reliability, and functionality using state-of-the art electronic equipment. We can also assist with installation and commissioning of these systems.
Generators installed on utility or industrial systems for peak shaving, co-generation, or backup present several engineering, financial, and regulatory challenges. From planning to implementation, these issues must be understood and properly addressed in order for the system to perform as intended.
Generator controls must be properly configured to achieve the desired regulation characteristics, communicate with existing control and protective systems, and properly respond to system load variations.
The protective devices installed as part of a generation package must be properly coordinated with the existing system to adequately protect both the generator and existing distribution equipment, while avoiding problems associated with backfeeding into faults, undesirable system islanding, and negatively impacting existing coordination and control systems.
From small, locally operated generators to multi-unit, fully automatic PLC-controlled power plants, ELECT, P.C. can design the generator system to meet your needs.
SCADA, Control, Metering
In today’s interconnected world, Supervisory Control and Data Acquisition (SCADA) is becoming increasingly prevalent. Generation, transmission, and distribution stations are being monitored and controlled remotely to improve system uptime and to remove utility personnel from potentially dangerous situations. Touchscreen computers in power plants and substations, using Human-Machine Interface (HMI) screens to graphically represent the station, provide a convenient and intuitive means of local monitoring and control. Historical data is maintained to aid in the troubleshooting of equipment or operational issues.
Remote or off-site control is achieved by integrating the station equipment into the existing SCADA system, providing devices that serve HMI screens via any standard web browser. This allows the owner to monitor and control the system from virtually anywhere.
Using commonly available hardware and software, ELECT, P.C. can provide a SCADA solution for any application. Our knowledge of the industry standard protocols, communications, and custom logic design mean we can integrate into your existing SCADA system or design a new system from the ground up.
Power Quality Investigations
Power quality is, roughly defined, the ability of an electrical system to support loads without the introduction of variations in the source that negatively affect the loads or power system.
If a system was capable of providing a perfectly regulated, continuous, sinusoidal voltage to an electrical load under all conditions, the power quality of that system might be considered perfect. However, in the real world, this is not the case. Voltages vary over the course of the day. Faults on the system result in momentary deep reductions in voltage. The switching of capacitor banks and some types of faults can result in harmful overvoltages. Poor wiring practices within a facility may compromise the grounding integrity. All of these can result in mis-operation, damage, or nuisance operation of equipment.
The investigation of a power quality problem must go beyond the ability to connect a meter and compile reams of data into a report with little analysis or understanding of the root problem. ELECT, P.C.’s experienced staff will investigate your power quality problem with an understanding of the factors that are and are not relevant, and how changes in the system or remedial equipment will affect the problem. ELECT, P.C.’s diagnostic process will minimizing metering and on-site disruptions, and arrive at a concise recommendation for the most practical and economic solution.
As a result of lightning strikes, system faults, switching events, and other anomalies, power systems are often subjected to voltages far greater than the system’s nominal, steady state voltages. While these overvoltages typically last for a only very brief period, usually far less than a millisecond, they can result in equipment misoperation and expensive equipment damage or accelerated aging. For this reason, transient surge suppressors and lightning arrestors are almost always located at critical locations in a power system, and where sensitive equipment is located. These devices, when properly applied, are very effective in limiting the maximum voltage on a system and protecting equipment.
However, if a system is not properly protected, protective devices have failed, or transient events are not severe enough to be clamped, a well-designed system can still experience problems. Because transients are often unpredictable, the metering and diagnosis of the exact problem is often very difficult.
ELECT, P.C. can identify and measure power system transients and model these using software, if necessary, in order to diagnose or solve transient-related power systems problems.
Harmonic Analysis Studies
The proliferation of electronic and other “nonlinear” loads has resulted in the introduction of harmonic currents and voltages into typical power systems. While often harmless, these higher frequency components can sometimes create problems with equipment capacity, power factor correction capacitors, and occasionally, equipment mis-operation. ELECT, P.C. can characterize a system with respect to the sources and effects of power system harmonics and recommend remedial measures if required.
Motor Starting Studies
Starting large motors can cause severe disturbances to electrical power systems due to the large current drawn by motors when starting. ELECT, P.C. performs motor starting studies to determine the ability of an electric power system, either the utility or local generation, to start a given motor without collapsing the system voltage or resulting in unacceptable starting torque. IEEE Standard 399 recommends motor starting studies be performed if a given motor horsepower exceeds 30% of the base transformer kVA rating of the supplying transformer or if the horsepower exceeds 10-15% of a generator intended to run the motor. These studies can identify the cause of observed problems or determine the performance of a proposed design or solution.