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Circuit breaker and switchgear repair fundamentals 

Can a circuit breaker be repaired?

 

Circuit breakers are mechanical devices with moving parts and therefore they are the most likely switchgear component to wear out and cause unintended outages. While not all circuit breakers can be repaired, there are options. Switchgear modernization is the process of repairing, reconditioning or replacing power circuit breakers used in switchgear, typically with little to no changes to the enclosure and busbar. Modernizing switchgear also includes the option to upgrade protective relaying, control components and wiring.

Why is switchgear modernization important? 

Reliable switchgear systems are vital for facility operations, but completely replacing these units can represent a significant capital investment; however, upgrading to modern circuit protection results in minimal downtime, can yield dramatic operational improvement and may extend the useful life of the equipment by up to 30 years. 

It’s prudent to choose modernization solutions instead of purchasing new equipment when faced with the following limitations: 

  • Electrical maintenance department’s bandwidth or expertise
  • Space available for new switchgear
  • Funding for the removal of existing equipment plus the purchase and installation of new equipment
  • Ability to withstand the extensive downtime required for major system improvements

What are the options for modernizing power circuit breakers in switchgear? 

The types of modernization solutions include conversions, replacements, retrofits, retrofills, remanufacturing and reconditioning. It’s important to understand the different switchgear upgrade options and the applicable industry standards.

What is a power switchgear conversion? | What is a retrofit? | What is a replacement?What is a retrofill?What is remanufacturing and reconditioning?

 

What is a power switchgear conversion?

power switchgear conversion is defined as any type of modification or replacement of any device within existing switchgear from the original tested design.  Examples  include replacing circuit breakers with another type of breaker (e.g. air magnetic to vacuum), upgrading existing bus bracing, and using a power-operated contactor instead of a power circuit breaker for switching duties.  The Institute of Electrical and Electronic Engineers (IEEE) maintains the IEEE Standard Requirements for Conversion of Power Switchgear Equipment, IEEE Standard C37.59-2018.

What is a retrofit?

Retrofit is a very commonly heard term in the industry, but the term is often used incorrectly.  Many use the term retrofit when referencing replacement circuit breakers or the alteration of a piece of existing equipment in some way.  When thinking about “retroactively” changing something from the original, retrofit is the first word that comes to mind.  Eaton does not recommend “retrofitting” switchgear because it can impact safety and reliability when altering components that perform a critical function (interrupting mechanism, interlocks) or reusing components with questionable integrity (primary bushings and disconnects).  

The prevalence of the so-called retrofit was one of the main drivers of the development of IEEE Std. C37.59, a standard which provides directions and requirements for the conversion of qualified power switchgear equipment.  There were incidents of accidents, injuries, equipment damage and even death being reported from retrofitted circuit breakers in the field.  Upon further investigation of these retrofitted circuit breakers, it was discovered that these devices didn’t undergo design verification testing such as high-power lab tests, BIL tests, mechanical interlock tests and di-electric tests.  As a result, IEEE created guidelines and processes to ensure the safety of users with converted circuit breakers and published IEEE Std C37.59-1991.  There are very few providers of "retrofit" circuit breakers within the market.

What is a replacement?

A replacement swaps the existing device with a new, but identical version of the same device
IEEE Std C37.59-2018, clause 3 offers two definitions for replacement circuit breakers.

  • Replacement interchangeable circuit breaker is “a circuit breaker that utilizes all new parts, has been design tested to IEEE Std C37.09 or to ANSI C37.50 or IEEE Std C37.14 as applicable for the equipment type and ratings, and requires no conversion of existing switchgear to maintain proper operation.”
  • Replacement non-interchangeable circuit breaker is “a circuit breaker that utilizes all new parts, has been design tested to IEEE Std C37.09 or to ANSI C37.50 or IEEE Std C37.14 as applicable for the equipment type and ratings but requires conversion of existing switchgear to maintain proper operation.”

There are two key differences between the types of replacement circuit breakers:

1)  The interchangeable replacement circuit breaker doesn’t require any modifications or changes to the existing switchgear to install and operate that replacement circuit breaker.  This sometimes is referred to as a direct replacement.

2) The non-interchangeable replacement requires some type of change to operate properly. Some replacement circuit breakers are classified as non-interchangeable because there may also be control wiring changes required to defeat external “52X” and “52Y” control relays as new and current circuit breakers have these features built into them and don’t need the old external relays.  These older control relays also may affect the timing of the control scheme and introduce timing delays to the overall protection scheme as these relays are just as old as the circuit breaker being replaced.  When it’s necessary to defeat these control relays, it is also necessary to prevent the old air circuit breaker from being applied in that switchgear cubicle. 

Eaton does this by placing a rejection bar in the switchgear cubicle which physically prevents the air breaker from entering but allows the MVVR to enter and operate normally.  When this change is required, it would then define the MVVR as a non-interchangeable replacement circuit breaker.

What is a retrofill?

A retrofill is a custom engineered solution used when a replacement is not available or is not practical.  The retrofill process is typically non-reversible and permanently modifies the switchgear cubicle.  The modifications may involve cutting or drilling, new primary circuit conductors, new doors or panels and new secondary control wiring. 

 

Retrofills are performed on medium-voltage and low-voltage switchgear and require the switchgear to be completely de-energized during installation and commissioning.  Eaton has performed many retrofill conversions that consist of the VCP-W or VCP-T circuit breaker for medium-voltage applications and the Magnum DS circuit breaker for low-voltage applications.  Each type includes its related components such as a cassette or compartment adaptor and qualifies these by the requirements set forth in IEEE Std C37.59-2018 and relevant IEEE standards.  Once the retrofill is completed, the switchgear circuit breaker compartment resembles equipment currently in production and has all the advantages of today’s technology and safety improvements.

Retrofills are excellent solutions for fixed-mount type circuit breakers and medium-voltage station class switchgear conversions.  The retrofill converts these fixed-mount designs to draw-out which enables more efficient maintenance, increased safety benefits and overall reliability improvements.

Reconditioning process 

The process of maintaining, repairing, rebuilding and refreshing existing equipment such as power circuit breakers may be referred to as reconditioning, remanufacturing, rebuilding, refresh, overhaul and refurbishment, and providers of these services are not the same. IEEE Std C37.59-2018 has only one definition for this process, and that is reconditioning.
 
 
Reconditioning as defined by IEEE Std C37.59-2018, is “the process of maintaining existing power switchgear equipment in operating condition as recommended by the original equipment manufacturer’s instructions."
 
 
Eaton has an extensive reconditioning process that involves complete inspection, documentation, total disassembly, carefully cleaning, reassembly, testing and ongoing tracking within our databases. However, where disassembly is not practical, replace component with new or reconditioned.  The process for this level of reconditioning is described as Class 1 Reconditioning. Visit www.eaton.com\class1 for additional information.

This level of reconditioning cannot be performed effectively on-site because it requires specific machinery as well as dedicated personnel and processes at a facility equipped for this high quality, procedure-based servicing. 

 

IEEE Std C37.59-2018 doesn’t include a definite clause for reconditioning but there are some strict requirements concerning reconditioning that should be followed. One of the most important requirements concerns changing a part during reconditioning from the qualified design. If a part is no longer available and is replaced with a reverse engineered part or some other design, then the converted circuit breaker must undergo design verification as stated in IEEE Std C37.59-2018. Depending on the part and complexity, this may involve re-testing the circuit breaker at the high-power test lab. 

 

A common trend during reconditioning of low-voltage power circuit breakers is converting the trip unit to a newer, solid-state type device. The new trip unit must be qualified on the circuit breaker to determine if it can still satisfy the short-circuit interruption rating(s). The new trip unit may alter the current carrying structure, the sensor mounting, and possibly the operating mechanism to integrate the new trip actuator, along with the new trip unit itself. IEEE Std C37.59-2018 clause 6.2.5.4 addresses trip unit conversion and the required design tests to validate the conversion.

Maintenance, troubleshooting and training

After installing a replacement circuit breaker, it is important to implement proper and continued maintenance, service and testing procedures. Eaton provides interactive, virtual instruction books for facility engineers and maintenance teams in facilities that have Eaton medium-voltage vacuum replacement breakers installed. These documents give clear instruction, through an interactive online tool, on how to conduct routine maintenance, change out common parts and monitor the health of the circuit breaker. The Visual Instruction Book Essentials, or VIBE, also covers instructions on the following tests for Eaton MV VR or MV VR+: 

  • Vacuum interrupter integrity
  • Insulation integrity
  • Current path resistance
  • Vacuum bottle contact inspection
  • Element lubrication
  • Component replacement and CloSure test (which monitors the ability of the mechanism to close the circuit breaker contacts fully