Protecting Power System Infrastructures

Transients, low power factor and harmonics are costing American businesses and hence consumers $Billions each year. This white paper explains how Voltage / Current Imbalances and Transients are harming your electrical system from the source to the end user and why prevention is critical to the efficiency of components and their lifespan.

Prevention is Critical:

Reliance upon electrical power has never been greater in human history. The Grid, its generating capability, its distribution and end user systems are all vulnerable from major imbalances, low power factors and harmonics and damages that can be caused by everyday usage, by its customers, terrestrial, weather events, geomagnetic disturbances and in rare cases from enemy attack.

At present the systems offered to solve the power problems from transients, low power factor and harmonics are only providing limited reductions and are not capable of eliminating the problems. Designing prevention-based solutions is the best way to eliminate the massive costs that effect every part of America’s economy which is according to the latest studies over $150 Billion each year.

Common Power Problems

To effectively protect all power systems, at first one must be able to identify the cause of most pervasive power problems and know how they impact power systems. While these problems are most applicable to end users at the low voltage range; they can be found in utility generation and distribution systems as well.

IEEE defines the most common issues in a power system

• Transients Interruptions
• Low power factors
• Sag / Under-voltage
• Swell / Over-voltage
• Frequency variations
• Arc Flash
• Electro-Magnetic pulse
• Harmonics
• Frequency variations

Transients

An impulsive transient is what most people are referring to when they say they have experienced a surge or a spike. Many different terms, such as bump, glitch, power surge, and spike have been used to describe impulsive transients.

Causes of impulsive transients include lightning, poor grounding, the switching of inductive loads, utility fault clearing, and Electrostatic Discharge (ESD). The results can range from the loss (or corruption) of data to physical damage of equipment. Lightning is probably the most damaging of these causes.

Interruptions

An interruption is defined as the complete loss of supply voltage or load current. The causes of interruptions can vary but are usually the result of some type of electrical supply grid damage, such as lightning strikes, animals, trees, vehicle accidents, destructive weather (high winds, heavy snow or ice on lines, etc.), equipment failure, or a basic circuit breaker tripping. While the utility infrastructure is designed to automatically compensate for many of these problems, it is not infallible.

Low Power Factor

Power factor measures how effectively a specific load consumes electrical energy to produce work and is the ratio of real power (kW) and apparent power (kVA) and is a dimensionless number between 0 and 1. Higher power factors translate into more effective usage of electrical power consumed.

 Low power factors mean more electricity is consumed to produce the same amount of work. Electrical utilities often add a penalty charge to lower power factor consumers.

Sag / Under-voltage

A sag is a reduction of AC voltage at a given frequency for the duration of 0.5 cycles to 1 minute’s time. Sags are usually caused by system faults and are also often the result f switching on loads with heavy startup currents.

Swell / Over-voltage:

A swell is the reverse form of a sag, having an increase in AC voltage for a duration of 0.5 cycles to 1 minute’s time. For swells, high-impedance neutral connections, sudden (especially large) load reductions, and a single- phase fault on a three-phase system are com- mon sources.

Harmonics

Harmonics are the result of electrical device's nonlinear responses. In other words Harmonics create non-sinusoidal line currents in the form of pulses or distortions which are by-products of nonlinear loads. Harmonics add strains to electrical systems that can lead to equipment damage, power supply failures, and plant downtime. A variety of situations can create harmonics in a facility:

• Electrical equipment with microprocessors and electronic circuits
• LED lighting
• Nonlinear magnetic fields in transformers and rotating air gaps
• Transformer core, eddy current, and winding skin effect losses increase with frequency
• DC current components, which create additional non-sinusoidal currents
• Any high frequency losses occur throughout the plant.

Frequency Variations:

There are many kinds of frequency issues from offsets, notching, harmonics, and inter-harmonics; but these are all conditions that occur largely in the end user’s power system. These variations happen because harmonics from loads are more likely in smaller wye type systems.

The high frequency variations that may lead to massive interconnected grid failure would come from the sun or enemy attack. Damage to only a few key infrastructure components could result in prolonged blackouts and collateral dam- age to adjoining devices.

Solar flares are natural occurrences that vary in severity and direction. This “solar weather” is sent out from the surface of the sun throughout our solar system in all directions. These flares contain large amounts of magnetic energy and depending on how they hit the earth can cause component damage on the surface or by temporarily changing the properties of the planet’s magnetic core. Either way, a direct hit of large proportion could cause equipment failure and black out entire regions.Electromagnetic Pulses (EMP) can be used in similar fashion but directed.

A well-executed detonation over Cincinnati, Ohio could black out 70% of the American population. Damage to large power transformers or generators could take months to repair. The high frequency disturbance of microwave explosions can destroy unprotected components much like an opera singer’s voice can break a glass.

The magnitude of each disturbance may depend on the source, but each can be mitigated effectively through the use of a phased voltage stabilization systems

Arc Flash

Arc Flash is caused by unrestrained ground faults that allow copper to heat to plasma stage and after several milliseconds it becomes an unquenchable plasma fire. One cubic inch of copper will expand almost instantly into seven cubic feet of 35,000-degree F super-heated gas. The resulting pressure wave can crush a worker’s chest. A Department of Labor 7-year study showed that 2,576 U.S. workers died and another 32,807 sustained lost-time injuries – losing an average of 13 days away from work.

Prevention is the best suppression

Facility and plant manger’s can assign personnel and budgets to detect and prevent these disturbances.  This is performed by examining the utility charges, utilizing power monitoring devices, integration of power monitoring devices and minimize the distortions.

References:

Approaches for Minimizing Risks to Power System Infrastructure due to Geomagnetic Disturbances. EPRI, Palo Alto, CA: October 2010. Kramer, Miriam. “Scientists Work to Protect Earth’s Power Grid from Extreme Solar Storms”; Space.com, July 2, 2013.

Hinton, William. “Phaseback VSGR Scalability”; Applied Energy White Paper, December 2013. “This is Phaseback”; Applied Energy White Paper, January 2013.

Electromagnetic Pulse: Effects on the US Power Grid. Environmental & Energy News. August 8,2011.

National Research Council: Terrorism and the Electric Power Delivery System. The National Academies Press, Washington DC: 2012.

James William Nilsson and Susan A. Riedel (2008). Electric circuits. Prentice Hall.