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Transient Recovery Voltage

Transient Recovery Voltage

Transient Recovery Voltage (TRV) is perhaps an inevitable and un-welcomed problem of the Power Gird. In medium and high voltage networks, the circuit breaker interrupts the current flow to the system during either normal switching operation or fault interruption. This leads to a rapid increase in the voltage across the breaker poles, as it become almost twice as high as operating.

 

Despite having an interrupting chamber with sufficient dielectric strength inside the breaker, the problem needs a timely solution since the recovery voltage rise results are overwhelming of the insulating medium.

 

Transient Recovery Voltage can lead to breaker failure; therefore, understanding the concept and its effect is important. We will be discussing the following.

 

1: Transient

2: Transient Recovery Voltage on Systems

3: Factors affecting TRV

4: What are the effects of TRV on a Circuit Breaker?

Transient

Transient voltage occurs whenever there is a sudden change in the state of the current. It is safe to say that the transient voltage across the circuit breaker poles is Transient Recovery voltage. Since TRV has can damage the circuit breaker to a great extent, therefore, it is important to learn about its effects.

Transient Recovery Voltage on Systems

TRV is the transient voltage that appears across a circuit breaker poles after a switching action.

The figure below shows how a sudden change of current can lead to a transient restriking voltage that oscillates to values higher than the nominal operating voltage of the system until it is finally damped (recovered) to the operating voltage.

Factors Affecting Transient Recovery Voltage

There are several factors of the system that have a direct or indirect impact of the TRV, however, below we have listed the most prominent ones:

  1. System Grounding
  2. Internal factors like the first pole to clear the fault.
  3. The number of transmission lines that tend to be terminated at a bus, along with their ability to resist the altering current.
  4. Bushing capacitance of voltage transformers, circuit breaks, etc.
  5. The level of the fault current at the time of the TRV Study.
  6. Capacitance and the Inductance in the system

 

What are the effects of TRV on a Circuit Breaker?

Despite the fact that Transient Recovery voltage occurs in a system for a very short time, it does increase rapidly. The fast increase leads to a number of adverse effects on system components. Below are some of these effects.

Insulation Failures

The transient recovery voltage comes into play due to the system’s inability to provide a constant flow of current. Things become more complicated due to the interruption of short circuits. Therefore, some precautionary measures should be in place to avoid a bigger problem.

Unchecked TRV will lead to insulation breakdown because it will stress out the circuit breaker insulation.  Common examples of circuit breaker’ insulation breakdown are flashover between one phase and another or external flashover between the phase and the ground.

Re-ignition

The arching in the interrupting medium occurs during circuit breaker switching. At this time, the focus of the arching medium is to regain the insulation property.  When the interrupting medium is able to withstand the rapidly increasing voltage, it means the interruption was successful.

To ensure the success of the interruption, the speed of the medium to go from conducting state to the insulating state should be higher than the rate of rising in the Transient Recovery Voltage. However, in case the rate of rise in TRV is more than the speed at which the medium returns to the insulating state, the current will keep on flowing into the circuit.

The establishment of the current is referred to as the re-ignition. The main reason for re-ignition is the arc plasma that has the conducting ions that reestablish the current. Re-ignition always occurs right after the current zero. A high TRV will force the medium to return to the insulating state, thus making it more stressed.

Restrike

When there is a dielectric breakdown that occurs because of the high field created across contacts, it allows the medium to not only become conductive but also to carry the current. This results in the reestablishment of the current.

Restrike is the process of establishing the current. It mostly occurs almost about half a cycle after there has been a current interruption.

Summary

A TRV leads to both re-ignition as well as restrike. When TRV challenges the longitudinal voltage between the poles of the breakers and it reaches the maximum voltage that the gaps can withstand, there will be a longitudinal breakdown or re-ignition.  Restrike on the other hand is when a break down takes place about half a quarter cycle after the current interruption.

 

Since both concepts can lead to failure, therefore it is imperative to avoid them by design. Ensure that you get a thorough TRV analysis done with functionalities and built-in standards to get a seamless comparison of a system’s prospect of having a TRV along with breaker innate TRV envelope and obtained simulation.

 

The team at Mechatronica Engineering Research & Development Ltd. Has vast experience in performing TRV studies for power systems during normal switching and when the system is subject to fault in accordance with IEEE C37.011. Our studies are not only conducted using well known transient analysis software packages such as EMTP and ATP, but we also have our own tools that were developed in-house by our experienced engineers to perform these studies for cases not covered by these softwares.

Lightning Protection System: A General Overview

Lightning Protection System

Despite intensive research, there are safety mangers and companies that fail to understand the magnitude of damage lightning can have on their assets. About 2.34 million cloud-to-ground lightning occurs in just Canada and it hits their economy hard.

According to reports, the Canadian economy suffers a loss between $600 million to $1 billion each year, and about 40 percent of this amount is allocated to property damage. In addition, one percent of the building fire is also due to the Lightning.

Since lightning tends to pose a significant threat to the building structure, electronics, and its occupants, thus it is important to understand all the key concepts. In the course of this article, we will be covering the following

  • What is lightning?
  • Lightning Protection System
  • Five important Elements for an Effective Lightning Protection System

With vast practical experience supported by theoretical knowledge, Mechtronica design and engineering team can provide analytical and detailed studies for the design of lightning protection system by;

  • Calculating the expected lightning strike frequency based on sire geographic location
  • Evaluating the permissible risk based on buildings’ construction, contents, occupancy, and immediate surroundings.

If the above studies reveal that the site needs protection against lightning, our team will proceed with designing the system considering CAN/CSA-B72-M87, NFPA 780, IEC 62305, or any other applicable local Standards and Regulations.

What is Lightning?

Lightning is a natural phenomenon, it is a short-lived electric arc or a spark discharge. Lightning can take place between clouds or between the ground and the cloud.  You come across lightning during a thunderstorm and it involves an exchange of electric charges.

In simple words, we can that lightning is a flow of electric current. Sometimes lightning starts from the ground, however, this mainly depends upon the polarity of the electrostatic charge. The most common lightning discharge negative cloud to ground discharge.

About 90 percent of the lightning discharge between the cloud and the ground is negative. Other less common types of discharge include positive ground to cloud lightning, positive cloud to ground lightning and negative ground to cloud lightning.

 

Lightning Protection System

Voltage surges and lightning put assets and people at risk. The discharge can occur in both rural as well as urban areas; therefore, it is imperative to have a lightning protection system in place in order to save people, assets and millions of dollars.

A lightning protection system provides protection against lightning by providing a safe path for the lightning to reach the ground. It consists of both external and internal lightning protection measures. A good lightning protection system tends to protect buildings from damage, people from death or injuries and electrical equipment from failure.

Five Important Elements for an Effective Lightning Protection System

Effective lightning systems need to have the following elements.

Air Terminals

Air terminals or better known as the lightning rods are metal tubes that a lightning protection company place on the projecting high point of a building including a water tank, a flagpole, a dormer, or the peak. This allows the system to intercept the lightning bolt.

Copper and aluminum are the most favored metals for the lightning rods. However, it is important to have the right thickness. For solid aluminum rods, the minimum diameter should be ½ inch and in case of solid copper, the rod should have a minimum of 3/8 inches diameter. These rods should be extended above the projecting object; the distance should be between 10 to 36 inches.

Usually, the maximum length of a rod is 24 inches, but if a longer rod is used, it will require extra support. The best spacing is to place the rod 20 feet apart if it is less than 24 inches, and 25 feet apart when it is longer than 24 inches. Placing the rods strategically will ensure that lightning strikes on these rods, instead of the building.

Conductors

In order to direct the lightning strike deep into the earth, you need to use conductors connected to the air terminals. These conductors can be either aluminum or copper. Once the lightning enters the earth, it is safely dissipated.

A good practice is to use either a copper conductor or an aluminum one. Using a conductor made out of copper and aluminum may lead to a chemically corrosive action or galvanic between the two elements.  The lightning rods form a connection between the main conductor and the down conductors. These rods then connect the down conductors to the ground connections.

Ground Connection

Ground connections come in play to safely, dissipate the lightning charge. The type of ground connection depends upon the soil conductivity of a respective area. An effective ground electrode should be 10-foot long solid copper or copper-clad steel. It should have a minimum ½-inch diameter and needs to be put at least 8 feet into the ground.

Bonding

Bonding includes branch conductors that form a connection between the metal objects including water pipes, ventilation fan, etc. and the ground system to provide protection against side-flashes. To ensure effective grounding and to eliminate lightning side-flashes, it is important to connect underground metal piping, telephone systems, and electrical systems to the lightning protection system.

Lightning Arrestors

Lightning Arrestors ensures the safety of your electrical devices as it provides protection against the lightning, that enters the building via the electrical wiring system. For effective results, it is important to install the lightning arrestors either the interior service entrance or at the building’s exterior electrical service entrance.

Conclusion

Both lightning and voltage surges endanger people and their assets. About 1,500,000,000 lightning strikes every year, and the number is going up. Therefore, it is important to have an effective and efficient lightning protection system intact.

Implementation of lightning protection system requires artisanship and technological intuition.  The industry has its own standards that need to be met to ensure a positive outcome.  A well-designed, well-analyzed and well-implemented lightning system will make it possible to avoid casualties, injuries, and damages to a great extent.

Latest Trends in Electrical Field Engineering Services

Field Engineering Services

The world keeps on changing and developing at a faster rate. To cope-up with this fast-growing world, everything needs to be upgraded enough. With the coming of the latest superpowers, a lot of change has occurred in the engineering field as well. Hence, we can see a complete makeover in commercial infrastructures as well as in the transportation sectors. This makeover calls the need for new and highly upgraded technologies and there comes the primary role of electrical field engineering services to perform. Let’s have a brief discussion on some of the emerging trends in this service.

Trends that Make Field Engineering Services more Upgraded

As per the above conversation, there are a lot of changes we can see in the field of electrical engineering. The job of the field engineers has undergone a great change than that of earlier. Here are certain factors on which tremendous change has occurred.

Sustainable Design

Taking the environment as one of the important things to consider, today, the engineers need to search for designs that can preserve the environment well. Once it has been realized the harmful effect on the environment through the toxic gases emitted from high-performance machines, the concern is given highly on the reduction of such damage to the environment. In short, today, electrical engineers focus on getting a perfect balance between the utility and consumption of such emission.

Project Design Time

Another important factor that an electric field engineer needs to prioritize the most is the time required to design a project. Here we are talking about complex designs for huge projects that require a number of electrical lines. Such designs need a lot of time, and it becomes impossible to complete it in a short span. But the project owners prefer to get the design within a limited period and start the project as early as possible. That is why engineers are in adoption to reduce project design time especially complex designs for heavy projects.

3D Laser Scanning

Generally, 3D laser scanning is widely used to study the dimensional information for any surface or object. Today, field engineers are looking for more possible options to set the electrical line designs within the existing lines through this 3D laser scanning process. This is not only advantageous for prioritizing goals to obtain designs with high accuracy but also to take all the benefits of the existing lines.

Cloud Sharing

There are many organizations whose clients stay faraway places, and it becomes difficult to communicate with them for making an effective design. That is why engineers are focusing more on building strong cloud sharing option to make the design-related communication easier. It is not only convenient to use but also secure than emails and is also free from hassle-some security breaches than other mediums.

Mechatronica is a member of many Technical Standard Organizations, and with our years of experience in the field, we have the best technologies to qualify our client’s projects within the promised time period. We offer impeccable solutions to make complex processes simple and less time-consuming. Get in touch with professional field engineering technicians from us and resolve your works done perfectly and accurately at the same time.