Power System Studies
We perform power system studies to ensure the long-term functionality of electrical facilities. Our guiding principle is that your electrical facilities must operate reliably without interruption while maintaining equipment and personnel protection.
Traditional overcurrent protection is insufficient to fully protect your electrical equipment against damage and your personnel against arc flash hazards. We recognize that your facility has unique requirements, such as supplying industrial loads with transient overloading, selectivity to isolate faults within a localized zone, high-speed tripping for optimal equipment protection, and advanced schemes to mitigate arc flash incident energy levels. We are well-versed in the modeling of complex systems utilizing commercial software suites such as SKM, ETAP, EasyPower, ATP-Draw, EMTP, PSCAD, and PSSE. Our deep understanding of complex AC and DC power protection schemes allows you to establish an electrical distribution system that harmoniously fulfills all your functionality requirements.
Our core competencies in Power System Studies:
Short Circuit Study
A short circuit study determines the magnitudes of balanced and unbalanced fault currents at pertinent locations throughout an electrical distribution system. The results from the short circuit study are used to confirm the interrupting ratings of protective devices (circuit breakers, fuses, reclosers, circuit switchers) and the withstanding ratings (SCCR or bus bracing) of electrical equipment.
Coordination Study
A coordination study ascertains the settings of protective devices within the distribution system. Protective settings are determined by plotting time‐current characteristic (TCC) curves to maximize equipment protection and ensure proper device coordination by setting overcurrent devices to trip in sequence, increase facility reliability, and limit the effects of nuisance tripping to smaller areas within the distribution system.
Arc Flash Study
An arc flash analysis is performed to determine the incident energy and arc flash boundary for electrical equipment within the distribution system. The arc flash study results are also used to prepare arc flash labels and determine the appropriate personal protective equipment (PPE) required for performing operation and maintenance of electrical equipment.
Load Flow Study
A load flow study is performed to calculate the voltage drop, the voltage level, and the power flow across all branch and feeder circuits. The study ensures that the power flow throughout the electrical distribution system will allow all loads to successfully operate without causing undesirable system voltage drops and that the system loading of the electrical equipment does not exceed its nominal rating.
Motor Starting Study
A motor starting study is performed to ensure that motors are able to successfully start and operate with minimum impact to the electrical distribution system. The analysis considers the motor inrush current, load torque profile, voltage drop during starting, system frequency during acceleration, and that system stability is maintained to avoid nuisance tripping during transient conditions.
Harmonics Study
A harmonics study determines the total distortion of voltage and current at a given point of common coupling (PCC). The analysis analyzes the effects of harmonic non-linear loads such as variable frequency drives, uninterruptible power supplies, and rectifiers. The analysis compares the effect of the non-linear loads against other system loads to determine the impact on the entire electrical distribution system.
An effective combination of power system studies can provide results to improve personnel safety, maximize distribution system protection, and optimize operational selectivity. Often just called a study, there is more to it than that:
Short Circuit Study. This analysis is performed per IEEE 3002.3 to ensure that the interrupting ratings of protective devices and withstand ratings of electrical equipment are suitable based on the balanced and unbalanced fault currents computed for the system model.
Protective Device Coordination Study. This analysis is performed per IEEE 3004 to yield increased equipment protection and ensure proper selective coordination by setting protective devices to trip in sequence, thereby increasing facility reliability, and limiting the effects of nuisance tripping and disturbances to smaller areas within the distribution system.
Arc Flash Study. When short circuit and coordination studies have been performed, their results help in compliance with IEEE 1584, NFPA 70E, and OSHA requirements regarding arc flash and shock hazards. An arc flash study will help determine incident energy levels, arc flash boundary, limited approach boundary, restricted approach boundary, and arc flash labels and serve as guidance in selecting appropriate PPE.
Load Flow Study. A load flow analysis of the electrical distribution system is performed per IEEE 3002.2 to verify that the system can operate without causing undesirable voltage drops between the source and load and that the overall loading of electrical components does not exceed their nominal ratings.
Harmonics Study. This analysis is performed per IEEE 3002.8 to determine if the total harmonic distortion of voltage and current at the point of common coupling are within the allowable limits of IEEE 519. A harmonic analysis also examines the effects of non-linear loads such as a VFD, UPS, or rectifier, thus determining their overall impact on the electrical system.
Motor Starting Study. This analysis is performed per IEEE 3002.7 to confirm that motor starting can be successfully performed for a given electrical system configuration while considering the overall effect of transient inrush current, voltage flicker, nominal system voltage, and frequency stability.
Grounding Grid Analysis. This analysis is performed per IEEE 80 to validate the adequacy and safety of the subsurface ground system by calculating the earth and conductor potentials for aspects including the ground potential rise, step voltage, and touch voltage profiles.
Cable Pulling Analysis. This analysis is performed per IEEE 1185 to determine the feasibility of pulling cables from the origin to the destination by verifying aspects including jamming, cable clearance, conduit fill, bending radius, sidewall bearing pressure, weight correction factor, and pulling tension.
Battery Sizing Study. This study is performed per IEEE 485 or IEEE 1115 to confirm the adequacy of the battery system equipment by validating the ampere output capacity of the battery chargers and confirming the adequacy of the ampere-hour rating of the batteries; thereby ensuring that the overall battery system is properly sized and rated to suit the operational requirements of the electrical distribution system.
Ductbank Thermal Evaluation. This evaluation is performed per IEEE 3001.2 to verify if cables within a ductbank configuration can support the loading requirements and not cause undesirable conductor overheating by ensuring cable temperatures remain within specified limits based on ambient temperature, conductor grouping, conduit spacing, and peak steady-state loading.
Transient Switching Stability Analysis. This analysis is performed per IEEE 3002.9 to ascertain the impact of voltage transient conditions, current chopping, prestrikes, and restrikes associated with capacitor switching, transformer energization, and fault interruption. Based on the analysis performed, solutions for appropriate surge protection and R-C snubber implementation can be ascertained to reduce undesirable transient conditions.
