Utility Capacitor Switching Analysis

Utilities

Utility capacitor switching events can have negative impacts on power quality, especially for customer power systems.  AC and DC drives, along with other electronic equipment, can be very sensitive to these and other transient voltages.  Utility capacitor switching transients can be magnified at low voltage capacitor locations on customer power systems, causing drives to trip and production and other processes to stop.  They can also cause upset and damage to medical imaging systems and other sensitive electronic equipment such as server power supplies and electronic lighting—indoors and outdoors.  In a time when customers are being allowed to choose their power provider, utilities cannot afford to be seen as the cause of customer power problems.

Studying, analyzing, and preventing utility capacitor switching events often requires the use of sophisticated computer simulation tools. Simulations provide a convenient way to characterize transient events, determine resulting power quality problems, and evaluate possible solutions. Frequently, simulations are performed in conjunction with power system PQ 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.

Electrotek Concepts® has developed a comprehensive approach for computer simulation and analysis of utility capacitor switching events. We use the Electromagnetic Transients Program—Revised Version (EMTP-RV) and PSCAD® to simulate electromagnetic, electromechanical, and control systems transients in multi-phase power systems.

There are a number of important transient-related concerns when transmission voltage level capacitor banks are applied.  Transmission system concerns include insulation withstand level, switchgear capabilities, energy duties of protective devices, and system harmonic considerations.  These considerations must be extended to also include distribution systems and customer facilities.

Capacitor energizing transients are important because capacitor bank energizing is one of the most frequent utility switching operations.  They can produce a high phase-to-phase overvoltage on a terminating transformer, excite circuit resonances creating transient voltage magnification in the secondary voltage networks, or as mentioned before, cause problems with sensitive electronic equipment in customer facilities.

Architecture & Engineering Firms

Industrial plants frequently require some form of power factor correction internal or external to the plant. As a part of the design and upgrade services that A&E firms typically provide, including an analysis focusing on switching power factor correction capacitors through Electrotek will better position A&E firms to win projects. Failing to include such an analysis places the A&E firm and their customers at risk of malfunction and damage to electronic equipment in the plant. New electronic equipment, which is likely part of the design or upgrade, may be sensitive to capacitor switching transients that get into the plant.

Knowing the gamut of capacitor switching transients that can occur at a plant provides information vital to determining if specific or custom PQ mitigation equipment is needed to protect plant equipment. Most PQ investigations involving capacitor switching transients and equipment malfunctions and failures revealed that no transient analysis was conducted prior to the location of new plants and upgrades to existing plants.

Changes to a utility power distribution system, which are typically made without notice to their customers, may suddenly cause these transients to cause malfunction and damage to electronic equipment. Changes include relocation, switching time and capacitor sizing among others. 

Electrotek Concepts® has developed a comprehensive approach for computer simulation and analysis of utility capacitor switching events. We use the Electromagnetic Transients Program—Revised Version (EMTP-RV) and PSCAD® to simulate electromagnetic, electromechanical, and control systems transients in multi-phase power systems.

Equipment Manufacturers

Equipment manufacturers engaging in equipment upgrades to improve their plant operations and reduce energy consumption are increasing their risk of malfunction and damage to electronic equipment, if a capacitor switching analysis is not conducted. Changes to a plant electrical system involving its electrical infrastructure, loads and capacity can alter the characteristics of capacitor switching transients already occurring. Older plants have fewer pieces of electronic equipment and utilize power factor correction capacitors. Such plants can increase their exposure to equipment damage caused by capacitor switching transients when new equipment is installed, the load characteristics change or when utility service entrances are upgraded or added.

Utility capacitor banks that were once static (not switched) may be converted to switching capacitor banks. New capacitor banks may also be added on a distribution circuit if the load changes (i.e., a customer is added to that circuit). Equipment manufacturers who have not previously experienced PQ problems with capacitor switching transients who suddenly develop these problems will want to contact Electrotek Concepts. Electrotek’s unique approach for determining the cause of capacitor switching transients pinpoints their location as well as the approximate size of the bank potentially causing the equipment problems at the manufacturer.

Electrotek Concepts® has developed a comprehensive approach for computer simulation and analysis of utility capacitor switching events. We use the Electromagnetic Transients Program—Revised Version (EMTP-RV) and PSCAD® to simulate electromagnetic, electromechanical, and control systems transients in multi-phase power systems.

End Users

End users operating equipment in the field are relying on a diverse group of electrical environments to operate their equipment. These end users may be contractors who conduct equipment services using some of their own equipment to diagnose and modify equipment owned and operated by larger companies. Service providers of cable television, Internet access and other telecommunications companies rely on power all across the utility power distribution system. Every utility pole is its own unique electrical environment. Every distribution circuit and substation is also its own unique environment.

These end users may experience unexplainable equipment malfunctions and damage. They may also experience limitations in bandwidth. Manufacturers who provide communications equipment to these end users can benefit from understanding how capacitor switching transients affect the operation and reliability of their equipment. Some pole locations are characteristic of more severe transients while others show little to no transient activity.

Electrotek’s unique modeling and simulation capabilities can help manufacturers and service providers determine the characteristics of unmanaged risks resulting from capacitor switching transients that exist today. These end user groups can benefit from knowing more about the characteristics of the electrical environments where they plan on locating their field equipment. They can also benefit from knowing how to properly specify PQ mitigation internal to this equipment to reduce the number of equipment malfunctions and failures as well as improve bandwidth and service to their customers.