The role of Low Voltage Switchgear

National and international standards define the manner in which electric circuits of low voltage installations must be realized. Standards determine the capabilities and limitations of the various switching devices which are collectively referred to as switchgear. The main functions of switchgear are:

• Electrical protection
• Electrical isolation of sections of an installation
• Local or remote switching

Electrical protection at low voltage is normally incorporated in circuit breakers, such as thermal magnetic devices and/or residual current operated tripping devices. In addition, circuit breakers provide:

• Over-voltage protection
• Under-voltage protection

The aim of protection is to avoid or to limit the destructive or dangerous consequences of excessive (short-circuit) currents, or those due to overloading and insulation failure. The circuit breaker will separate the defective circuit from the rest of the installation.

The operation of switchgear is an important part of power-system control. Functional control Switchgear-control functions allow system operating personnel to modify a loaded system at any moment, according to requirements, and include:

• Functional control (routine switching, etc.)
• Emergency switching
• Maintenance operations on the power system

The operation and maintenance of your electrical switchgear equipment can be complicated and dangerous for the inexperienced. Rely on Carolina Precision Switchgear’s reputation and over 100 years of experience to handle your company’s service requirements.

Copyright 2009 cpswitchgear.com Electrical Switchgear Consulting, Repair & Testing Services

Electrical Switchgear services provided by Carolina Precision Switchgear

As a manager of technical services, or a maintenance supervisor, you may find yourself dealing with your company’s power plant. In this day of budget cutbacks, loss of revenue and the state of our economy, you have to make decisions that affect your bottom line. Should you buy new equipment or should you continue to repair and refurbish existing plant? It’s a Buy vs. Repair question.

At Carolina Precision Switchgear, we offer help to managers faced with these types of decisions. You must know when to squeeze out extra production or invest in new. We can help. In some cases, we actually service electrical switchgear equipment more frequently than recommended to keep it operating in peak condition.

One of the best times to determine these factors is before an annual or semiannual plant shutdown. Proper planning gives maintenance staff time to determine if switchgear equipment and other plant facilities are upgraded or equipment is overhauled during these planned shutdowns. The key word is “planned,” especially when it comes to the electrical distribution system. A maintenance shutdown is an excellent time to consider what other work needs to be done on the distribution system, avoiding the necessity of performing energized work during the rest of the year, and avoiding the risk of an arc flash accident. Obviously, working on de-energized equipment is preferable to working on energized equipment.

At CP Switchgear, we offer consulting services for low & medium voltage switchgear, primary injection relay testing and transformer testing. Do not face the issues alone when faced with challenges of replacement or repair. We can help you make decisions concerning the age of your electrical system and its components, safety, cost, reliability and the feasibility of modernization. With over 100 years of combined service in the power industry we are the ones to call to make your job easier.

Copyright 2009 cpswitchgear.com Electrical Switchgear Consulting, Repair & Testing Services

CB-7745 with a new Mac 20 digital upgrade. Electrical Switchgear Test Set

Carolina Precision Switchgear now operates with one of the premier pieces of electrical switchgear test equipment available today. This primary injection test set is a model CB-7745 with a new MAC-20 digital upgrade. The MAC-20 has a serial port to connect to a PC so a computer read out of the tests can be captured. The CB-7745 is widely used by Carolina Precision Switchgear in our work at Duke Energy. This is one of the most durable and accurate circuit breaker test sets on the market. We firmly believe the only way to accurately test a relay on a low voltage circuit breaker is to use primary injection. Secondary injection will only test the relay and does not use the entire circuit for opening the breaker. Primary current injection goes through the entire circuit of the breaker, including the current transformer’s, ( CT’s). This is extremely important to verify the current transformer will recognize the current overload which will then trip the breaker on a relay timeout.

Loading up the CB-7745 and taking it home

The CB-7745 current breaker test set is capable of pumping out 40,000 continuous amps. Amps of this magnitude are essential for proper testing of low voltage 480/600 volt circuit breaker relays on the instantaneous test.

If you would like information about the electrical switchgear services we provide, please use our convenient contact form at the top of the page, or call Doug Weaver directly at 704-596-7124.

Copyright 2009 cpswitchgear.com Electrical Switchgear Maintenance Services

Carolina Precision Switchgear adds CB-7745, High Current Relay Test Set

It was time to hit the road for Doug Weaver and Barry Welch and head for Maryland to pick up the latest in Carolina Precision Switchgear’s arsenal of test equipment. In an effort to better serve our clients from a mobile service perspective, it is necessary to have the proper electrical switchgear test equipment. After a full day of driving from Charlotte, NC to New Windsor, Maryland, the two arrived at the ETI test facility.

Doug & Barry were there to oversee and watch the calibration of the CB-7745 low voltage circuit breaker test set. The first task was to change the tap setting from 208v to the 480v setting. The test set is also capable of being energized from a 600v source. The high current relay test set performed flawlessly during the calibration process. Once all of the tests were performed, the CB-7745 was readied for transport in the new Carolina Precision Switchgear mobile enclosed trailer.

The primary injection test set is a model CB-7745 with a new MAC-20 digital upgrade. The MAC-20 has a serial port to connect to a PC so a computer read out of the tests can be captured. The CPS owners used the type of relay test set and MAC-20 upgrade during their service with Duke Energy. Carolina Precision Switchgear has served the needs of Duke Energy for years. You can be assured that if Duke Energy uses CPS services that your company can also trust the electrical switchgear services that we provide. This is one of the most durable and accurate circuit breaker test sets on the market. We firmly believe the only way to accurately test a relay on a low voltage circuit breaker is to use primary injection. Secondary injection will only test the relay and does not use the entire circuit for opening the breaker. Primary current injection goes through the entire circuit of the breaker, including the current transformer’s, ( CT’s). This is extremely important to verify the CT’s will recognize the current overload which will then trip the breaker on a relay timeout.

To understand how Carolina Precision Switchgear can provide electrical switchgear services for your company, please use the convenient contact form at the top of the page. Or you can call Doug Weaver directly at 704-596-4242.

Electrical Switchgear and Distribution

Electrical distribution equipment is certainly the heart of any industrial facility. Without a reliable electrical distribution system, the operation of any facility would be impossible. From lighting, security, manufacturing and environmental controls, nothing happens without electricity.

Electrical switchgear is usually specified in heavy industrial applications where the demands on the equipment require more robust construction. Perhaps somewhat surprisingly, the condition of this equipment (including regularly scheduled maintenance) has not been a primary concern in most facilities. Facility managers have a lot on their mind and sometimes do not consider that electrical switchgear equipment requires regular maintenance. Facility managers must consider this to avoid a failure in the electrical distribution system. A failure could lead to process interruption, and it creates an elevated safety and property risk as well. Maintenance of electrical equipment like switchgear is critical for proper protective functioning and reliability of the distribution system.

Electrical switchgear and switchboard components such as overcurrent protective devices, which include fuses, circuit breakers and protective relays, are fundamental to the task of protecting the system as well as reducing hazards for electrical workers. When these devices are maintained well, they operate optimally to clear any fault condition – from a simple overcurrent event to a bolted or potentially hazardous arcing fault.

While fuse technology has not changed substantially over the past two decades, power circuit breaker and protective relay technology have undergone significant design improvements since the early to mid-1980s. Older power circuit beakers were designed around an open iron frame structure with electromechanical trip units. These devices needed iron frame construction in order to have the ability to withstand the fault current conditions present in many facilities, and were designed with an open-style construction to allow the extensive maintenance that was required to keep the devices functioning properly. Often, older power circuit breaker designs required the use of limiter fuses added to the circuit breaker to protect the breaker at fault current levels higher than those for which the breaker was rated. These limiter fuses added significantly to the size of the device, and consequently to the overall size of the switchgear.

Modern power circuit breakers are designed using space-age materials in very compact formats with digital trip units. They are also designed for significantly reduced maintenance requirements. These products now offer very high fault-current withstand capabilities without the use of limiter fuses. Since power circuit breakers provide such a vital function in protecting the electrical system, as well as reducing the risk to electrical workers from arcing faults, these design improvements are a quantum leap forward in equipment and personnel protection. They have very low maintenance requirements and allow new switchgear to be much more compact than older open iron frame circuit breaker designs.

Retrofit options are now available to extend the life of existing switchgear, which could be a more cost-effective choice for some facilities.

Electrical Switchgear Options Available:

Facility managers faced with the choice of replacing or retrofitting their existing obsolete switchgear to take advantage of the capabilities of the newer generation of circuit protection technology should make an informed choice; there are many factors to consider in this decision. One of these factors, of course, is the initial capital cost, along with potential disruption to the facility’s processes and workflow during the course of changing out the equipment.

Carolina Precision Switchgear can help Facility Managers facing these types of decisions through our consulting services. Call us today and we will help you to make an informed cost effective decision for your company.