What is IEEE C37.20.2? 

IEEE C37.20.2 is a standard that outlines construction and testing requirements for metal-clad medium-voltage switchgear to ensure gear is safe, reliable and maintainable. The standard applies to equipment with voltage ratings of up to 38 kV and main bus current ratings up to 4000 A. It maintains that switchgear must include specific design elements for safe and consistent operations, as well as pass testing for dielectric withstand, temperature rise, mechanical operations, and ground and test device.  

What is the difference between metal-clad and metal-enclosed switchgear? 

Metal-clad and metal-enclosed switchgear serve the same functional purpose as medium-voltage power distribution agents. The main difference between the two is that metal-clad equipment has a compartmentalized design with separate enclosures for different components, while metal-enclosed equipment has a single enclosure that contains all components. Due to its compartmentalized construction, metal-clad switchgear provides a more robust design with more features available. It also maintains a current rating of up to 4000 A, while metal-enclosed operates up to 2000 A. Factors such as initial cost and total cost of ownership, maintenance, footprint and specific operating needs should also be taken into consideration when deciding between metal-clad and metal-enclosed switchgear. More information can be found in the application paper AP083010EN — A comparison of metal-enclosed load interrupter (ME) switchgear and metal-clad (MC) switchgear. 

What is the difference between air-insulated and gas-insulated switchgear? 

Air-insulated and gas-insulated switchgear each offer specific advantages, making them suitable for a wide range of differing applications. Air-insulated switchgear provides a lower initial cost and several customizable features including local utility metering sections. It is an environmentally friendly option, highly suitable for rural, outdoor and cost-sensitive applications. Gas-insulated gear offers a reduced footprint, specialized safety provisions and low maintenance costs, making it suitable for footprint-constrained installations, urban applications and environments with harsh conditions. To decide which is right for you, more information can be found in white paper WP022006EN — Tips for selecting between air-insulated and gas-insulated switchgear. 

How does arc-resistant design differ from standard metal-clad equipment? 

Eaton’s arc-resistant design for metal-clad medium-voltage switchgear is designed to withstand the effects of internal arcing faults by safely containing and redirecting the thermal energy/blast force caused by an arc fault, regardless of its original location. Our offerings include Type 2 and Type 2B arc-resistant switchgear manufactured and tested in accordance with IEEE C37.20.7. Type 2 accessibility means arc-resistant designs and features are available at the front, back and side exteriors of switchgear, and Type 2B adds on to this by including arc-resistance in front of the instrument/control compartment with that compartment door opened. More information on arc-resistant designs and standards can be found in design guides DG022003EN — VacClad-W 5–15 kV, arc-resistant, metal-clad medium-voltage switchgear and DG022005EN — VacClad-W 27 kV, arc-resistant, metal-clad medium-voltage switchgear. 

What is the difference between main-main and main-tie-main automatic transfer?  

A main-main automatic transfer scheme uses one main device as the primary source for incoming power. If that source fails, the entire load is shifted over to the backup main source, such as a generator or second utility feed. Using a main-main configuration, you can install a UL 1008A automatic transfer switch in equipment up to 15 kV. 

Main-tie-main automatic transfer applications typically split the load between two incoming sources with a tie breaker in-between that is normally open. If one of the sources fail, all the feeders on that side of the system are transferred to the remaining source via the tie breaker closing. These systems can be incredibly intelligent, with both open and closed transfer scheme solutions available. With a main-tie-main configuration, isolation of one side of a system is available via that tie breaker, allowing for safe maintenance activities. 

What is the difference between manual racking, electric levering, and integral racking, and what options are available? 

Manual racking of breakers and auxiliary compartments involves an operator manually cranking the lever to rack in breakers and auxiliary compartments and requires local operation to open and close the breaker. Electric levering builds upon the foundation of manual racking via an attached motor at the front door performing racking operations, making racking quicker and safer by allowing the user to be outside the arc-flash boundary during the racking of the device. Both of these options require operators to interact closely with live equipment, posing safety risks to even highly trained individuals. Eaton’s MR2 integral remote racking provides a solution to this safety risk by installing a motor on all breaker and auxiliary pans to allow the operator to rack devices without ever having to enter the arc-flash boundary. Integral racking is the safest and most robust racking option. You can learn more about the benefits of Eaton’s integral racking solution at Eaton.com/MR2. 

Does Eaton offer a solution for voltage sensing? How does it compare to traditional VTs/PTs? 

Yes! Eaton’s Ohmic voltage sensing (OVS) for metal-clad and load interrupter switchgear is a proven, intelligent, modern solution to mitigate transient overvoltage, a harmful power anomaly in your switchgear. OVS employs resistive voltage dividers in place of standard VTs to increase voltage sensing reliability, improve operational efficiency and save space traditionally inhabited by VT compartments. This solution works with all devices and is vendor agnostic to meet your switchgear installation needs. Learn more about the benefits of OVS at Eaton.com/OVS. 

What solution does Eaton provide for thermal monitoring? 

Eaton’s continuous thermal monitoring in metal-clad equipment provides users with a comprehensive, real-time view of switchgear health. The system uses hardwired sensors installed directly in the gear to monitor thermal data of critical gear components such as bus connections and cable compartments, tracking temperature trends to help detect potential issues (loose connections, overloads, etc.) before they lead to equipment failure. This system greatly reduces downtime and costs incurred by periodic manual inspection necessary with IR windows, and it significantly reduces arc flash risk by eliminating the need to open panels. This solution is UL listed and has been verified in our test lab for consistent and accurate sensor placement and system readings. 

Can I only use Eaton meters and relays with Eaton’s medium voltage switchgear? 

No! Eaton partners with a variety of meter and relay manufacturers to offer quality support based on each customer’s individual needs and preferences.  

Do I need surge protection in my switchgear, and what options are available? 

Throughout their lives, switchgear assemblies may be subjected to voltage transients caused by lightning, switching, etc. Eaton metal-clad equipment is designed in consideration of surge protection guidelines outlined by ANSI/IEEE. Due to the wide variety of applications and ratings applicable to different elements of power systems, any given circuit may or may not require surge protection, hence the recommended surge protection measures for metal-clad switchgear are dependent upon the customer’s specifications for circuit characteristics and cost. Eaton’s recommendations for surge protection can be found in the application paper AP083011EN — Surge protection guidelines for VacClad-W metal-clad switchgear.