Power System Modeling & analysis Capabilities

PBE offers extensive experience with respect to utility, industrial, and commercial studies for engineering firms & customers 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 (PQ) site surveys involving wiring and ground evaluations.  PBE has developed a comprehensive approach that includes computer simulations and measurements for analyzing facility PQ problems. Specific capabilities include:

PQ Studies

PBE utilizes an integrated approach dealing with all aspects of PQ evaluation for electric utilities and their customers. Investigations provide customers with solutions to existing plant PQ problems and new plant PQ design assurance. PQ 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 variable frequency drives (VFDs), along with stricter harmonic standards and limits are resulting in more harmonic problems than ever before.

PBE uses computer simulations to analyze potential problems at the utility/customer interface.  Analysis results include recommendations for optimum solutions to PQ.  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). 

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

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

Utility Transmission and Distribution Analysis

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.

PBE uses 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 over-voltages 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

Harmonic Analysis and Problem Solving

PBE 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 519-2014 compliance

In addition to analytical expertise, we have experience in recommending and implementing solutions to PQ 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. 

Utility Capacitor Switching Analysis

PBE 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 PQ problems, and evaluate possible mitigation methods.  Quite often they are performed in conjunction with system monitoring for verification of models and identification of important PQ 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 PQ 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 (pre-insertion 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)
  • Ferroresonance 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 PQ 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 PQ 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.