PQ Modeling & Simulations

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Electrotek offers extensive experience with respect to utility, industrial, and commercial studies that address power system problems.  These capabilities include site surveys, field measurements, computer simulations, and equipment sensitivity characterizations.  Specific study capabilities include power factor correction analysis, harmonic evaluations, transient analysis, and power quality site surveys involving wiring and ground evaluations.  We have developed a comprehensive approach that includes computer simulations and measurements for analyzing facility power quality problems.  Specific capabilities include:

Power Quality Studies

Electrotek utilizes an integrated approach dealing with all aspects of power quality evaluation for electric utilities and their customers.  Investigations provide customers with solutions to existing plant power quality problems, and new plant power quality design assurance.  Power quality problems are becoming increasingly important because of the changing nature of customer loads.  Manufacturing processes are becoming more automated, and electronic customer loads such as computer equipment are becoming more sensitive to voltage variations – especially voltage sags, momentary interruptions, and transients.  In addition, the increased use of energy efficient power electronic technologies such as adjustable-speed drives (ASDs), along with stricter harmonic standards and limits, are resulting in more harmonic problems than ever before.

We use computer simulations to analyze potential problems at the utility/customer interface.  Analysis results include recommendations for optimum solutions to power quality.  Analysis of various methods and solutions are determined based on economic, control, and technical considerations.  Specifications are determined for required equipment, including power conditioning equipment, custom power devices, harmonic filters, switching devices, current limiting reactors, surge arresters, customer surge control devices such as transient voltage surge suppressors (TVSS), and flexible AC transmission system (FACTS) devices as static var compensators (SVC).....read more

Voltage Variation Analysis

Studies that are completed to determine the probability of nuisance tripping of sensitive loads and evaluate the effectiveness of possible corrective measures.  Voltage sags and momentary interruptions result from faults on the power system.  The extent that voltage sags or momentary interruptions affect plant equipment depends upon the magnitude, and duration of the sag, or interruption and the ride-through capability of the equipment.  Areas generally investigated include:

  • Area of vulnerability determination for transmission system faults
  • Magnitude vs. distance determination for faults on distribution system parallel feeders
  • Estimation of voltage sag frequency of occurrence down to specific levels
  • Process control equipment ride-through capability verification
  • Estimation of expected number of equipment trip-outs
  • Specification of utility solutions to voltage sags, including fault prevention and modification of fault clearing practices
  • Specification of customer solution mitigation techniques including power conditioning equipment and modification of electronic controls
  • Analysis and modernization of customer equipment procurement specifications

Our procedure for evaluating power quality problems is based on the variety of different power quality concerns that can exist and focuses on a combination of monitoring and analysis to characterize these concerns.  Once we characterize the power quality concerns, we can then use the analysis procedures developed to evaluate possible solutions to the power quality problems.  These solutions must then be evaluated from both a technical and an economic perspective.... read more

Distribution Planning

This is an area dealing with computer simulation and analysis of utility transmission and distribution systems.  Supporting this approach is considerable application-based expertise using the Electromagnetic Transients Program (EMTP) and the PSCAD/EMTDC transient analysis program.

We use computer simulations to analyze potential switching problems associated with a variety of utility equipment operations.  Analysis results include, recommendations for optimum solutions, to possible switching problems.  Analysis of various methods for controlling transient overvoltage’s is determined based on economic, control, and technical considerations.  Specifications are determined for equipment required, including switching devices, current-limiting reactors, surge arresters, and customer surge control devices. 

The following is a listing of some of the power system studies that have been performed in the past, including

  • Switching surge studies
    • Capacitor switching
    • Line energizing (deterministic and probabilistic)
    • Single-pole switching / high speed reclosing / line dropping / fault clearing (TRVs)
    • Transformer switching / reactor switching
  • Lightning surges
  • Arrester duties and insulation coordination
  • Shaft torsional stress calculations
  • HVDC and FACTS operation and controls / static-var compensator operation and controls
  • Ferroresonance, parallel resonance
  • Motor starting
  • General control system analysis
  • Series capacitor protection
  • Harmonic propagation analysis

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Harmonic Analysis & Problem Solving

Electrotek has developed a comprehensive approach to solving harmonic problems for customers.  The approach involves a number of important functions in order to meet the variety of needs that exist in this area:

  • Provide training to utilities and customers. Seminars are designed to increase the overall understanding related to power system harmonic analysis
  • Perform harmonic studies to analyze harmonic propagation, system response characteristics, and to predict distortion levels resulting from specific loads
  • Resonance conditions resulting in excessive distortion levels
  • IEEE Standard 519-1992 compliance

In addition to analytical expertise, we have experience in recommending and implementing solutions to power quality problems.  We have worked with utilities, and customers, to implement corrective measures such as dedicated power supply, capacitor banks, harmonic filters, and dynamic static transfer switches.  To address voltage sag concerns, we have experience in the implementation of ride through technologies including uninterruptible power supplies, flywheels, superconducting magnetic energy storage (SMES) devices, and batteries.... read more

Utility Capacitor Switching Analysis

Electrotek has developed a comprehensive approach for analyzing utility capacitor switching events.  The analysis of utility capacitor switching events often requires the use of modeling tools.  Simulations provide a convenient means to characterize transient events, determine resulting power quality problems, and evaluate possible mitigation methods.  Quite often they are performed in conjunction with system monitoring for verification of models and identification of important power quality concerns.  Application considerations include capacitor bank configurations, insulation withstand levels, switchgear capabilities, grounding, overcurrent protection, overvoltage protection, energy duties of protective devices, and unbalance detection.

There are a number of important transient-related concerns when transmission and distribution voltage level capacitor banks are applied.  The transmission system concerns include insulation withstand level, switchgear capabilities, energy duties of protective devices, and system harmonic considerations.  The considerations must also be extended to include distribution systems and power quality evaluations (sensitive customer equipment).  The primary concerns generally evaluated for a capacitor application study include evaluating.

  • Transient overcurrent and overvoltage magnitudes for normal capacitor energizing operations, including the effects of other capacitor banks and system loads
  • The effectiveness (control of energizing transients) of various transient control methods (preinsertion inductors/resistors, synchronous closing control, etc.)
  • Inrush currents for normal and back-to-back switching operations
  • Outrush currents for nearby fault conditions
  • Arrester duties for voltage magnification conditions, and during capacitor bank restrike events
  • Phase-to-phase transients at transformer terminations
  • System frequency response characteristics (resonance)
  • Ferro resonance possibilities
  • The impact of capacitor switching transients on lower voltage systems
    • Magnified transients at lower voltage buses, and within customer facilities
    • Nuisance tripping of customer power electronic equipment, such as adjustable-speed drives

Analytical methods provide the framework for evaluating a variety of power quality phenomena, including the impact of utility capacitor switching on customer systems.  Typically, we develop a simulation of the customer system and important parts of the utility system for transient switching surge analysis.  This model can be used for analyses to predict power quality problems and evaluate possible solutions to problems.  In cooperation with the customer, the data for the model is collected and compiled into a database for convenient reference during the study... read more

Distributed Generation

Deregulation of the electric power industry, along with advances in smaller-scale generation technologies, is paving the way for significant deployment of distributed generation in the United States. The US market for distributed generation equipment alone is forecast to double over the next few years as both electricity users and suppliers take increasing advantage of this “new” – but, actually old – concept for supplying electric power. 

In terms of simple economics, emerging open markets for electricity have created price and supply volatility that makes customer-owned and operated generation financially attractive, but also a potential source of economic risk. From a technical perspective, interconnecting DG to the utility grid raises a number of issues relating to safety, power quality, and impact on power system operations.  These factors dictate careful consideration before implementing DG ... read more

Power Factor Correction

In some situations, it may be necessary to model and simulate power system circuitry inside a customer’s facility such as inside a commercial or industrial plant, or circuitry outside of a facility. Customers routinely operate industrial power systems which must perform even better than utility transmission and distribution circuits. In many cases, it may be necessary to model and simulate specific PQ phenomena occurring on customer power systems. This is especially true when customers are operating a lot of medium- to high-power non-linear loads like variable frequency drives (VFDs) and other non-linear loads.

In other cases, it may be necessary to model and simulate specialized power system circuitry used for specific applications or processes. An example of a system like this is underground 480-volt, three-phase branch circuitry laid down an Interstate for miles that powers the hi-mast highway lighting. Such lighting systems use long conductors running between poles and up poles to fixtures. Fixtures, once of the high-intensity discharge (HID) magnetic core-and-coil ballasts, are now being replaced with electronic ballasts and electronic drivers for LED lighting.

Electrotek's expertise in modeling and simulating can address any of these PQ problems on any circuit type, for any voltage and load. Such exercises can be carried out to identify why PQ disturbances occur, what outside influence must happen to generate a harmful PQ disturbance and what system changes must be put into place to mitigate PQ problems ... read more