Mv Switchgear

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TMMB

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I Would Like To Know What Is The Different Between Metalclad & Metal Enclosed Mv Switchgear .

Regards
 
TMMB said:
I Would Like To Know What Is The Different Between Metalclad & Metal Enclosed Mv Switchgear .

Regards
Click to expand...

Quick and dirty explanation.

Metal enclosed gear construction looks just like 600V gear only it is bigger. The busbars are exposed inside of the gear and there is little if any compartmentalization. most, but not all, MV fusible switchgear is metal enclosed.

Metal clad switchgear (also called ANSI gear) is built with many individual compartments. The busing is normally insulated and contained in its own compartment. There are a separate incoming line and outgoing load wiring compartments. Most, but not all, MV circuit breaker switchgear is metal clad.
 
Thanx for ur answer , but i didnt got it well , can u calrify more pls
 
The best way is to look at Metal Clad, then compare that to Metal Enclosed. First off though, keep in mind that Switchgear in general is where you are switching large loads. So the energy involved in the switching / protection devices is extreme when compared to panelboards or switchboards or MCCs.

Metal Clad gear has separate compartments for each switching / protection element in the lineup. They are separate from each other, they are also separate from the bus structure. The switching / protection devices are enclosed in what are referred to as "Cells". Each cell has a bus stab assembly that allows connection, at the back of the cell, into the bus structure to both take power from the line and allow for load connections in another isolated compartment. These connections are done with a racking mechanism that ensures positive solid connection to the bus.

With all that isolation, if a fault happens in the circuit of one cell, that energy involved in that fault is contained in that cell. If something explodes (and it does explode on occasion), then the destructive forces are held in check by the multiple layers of metal enclosures. A catastrophe in one cell does not necessarily spread to adjacent cells, so the entire plant is not taken down. Vice-versa, if something happens on the line side, it does not take out all the cells as well, so once that problem is fixed, you are up and running again as quickly as possible. One side benefit of this type of equipment is that it can be built with circuit breakers as the switching / protection devices. CBs are smaller than Fused Load Interruptor Switches (FLIS) so you can stack multiple CBs in a single section. The entire concept is referred to as "Fault Tolerance". That is the up side.


The downside(s) of Metal Clad:
  • Large; Even though you can stack cells, the bus structures and racking mechanisms make it very very deep. Some as much as 96" deep, the shallowest are I think 54" deep.
  • Access; In addition, the line and load connections are all made at the back, so you cannot put MC gear up against a wall. Then the cells need a racking mechanism and a lift or small crane system to handle them, so you need a lot of room in front of them, usually more than the minimum switchgear clearance required by the NEC. That means a LOT of real estate.
  • Expensive; Metal Clad is the most expensive method available.

Metal Enclosed Insulated Switchgear (MEIS) on the other hand does not necessarily come with the same levels of isolation. There is little more than a thin sheet metal wall between one section and the next. As a result, the concept of fault tolerance is limited. To reduce the risk of collateral damage then, MEIS is almost always limited to using FLIS devices as the switching / protection units. That means, because of the size of the fuses involved, one "cell" per section. But the sections can be as shallow as 36", some even 30". In addition, MEIS is usually designed so that all service and connection can be doen from the front, so it can go up against a wall. So in general, MEIS can take up a little less overall real estate, but can fit in smaller rooms because of the shallower depth. As a result, MEIS is usually a lot less expensive.


The downside(s) of MEIS:
  • Less fault tolerance; If you have a catastrophic event somewhere, chances are good it will cause collateral damage and shut down a bigger part of your operation. In some cases, that is not much of an issue because if one part goes down, the rest MUST shut down anyway. But it warrants consideration. Sometimes the cheapest option up front ends up being the most expensive later on.
  • No Circuit Breakers; Some people like circuit breakers instead of fuses because they can be reset vs replaced. That is a longer argument than I will indulge in here, but it is a difference.
  • Less Flexible; If something changes, you can't just swap out or add a cell. You have to shut down, change or add on to the bus, then re-energize.
 
Last edited:
Jraef said:
The best way is to look at Metal Clad, then compare that to Metal Enclosed. First off though, keep in mind that Switchgear in general is where you are switching large loads. So the energy involved in the switching / protection devices is extreme when compared to panelboards or switchboards or MCCs.

Metal Clad gear has separate compartments for each switching / protection element in the lineup. They are separate from each other, they are also separate from the bus structure. The switching / protection devices are enclosed in what are referred to as "Cells". Each cell has a bus stab assembly that allows connection, at the back of the cell, into the bus structure to both take power from the line and allow for load connections in another isolated compartment. These connections are done with a racking mechanism that ensures positive solid connection to the bus.

With all that isolation, if a fault happens in the circuit of one cell, that energy involved in that fault is contained in that cell. If something explodes (and it does explode on occasion), then the destructive forces are held in check by the multiple layers of metal enclosures. A catastrophe in one cell does not necessarily spread to adjacent cells, so the entire plant is not taken down. Vice-versa, if something happens on the line side, it does not take out all the cells as well, so once that problem is fixed, you are up and running again as quickly as possible. One side benefit of this type of equipment is that it can be built with circuit breakers as the switching / protection devices. CBs are smaller than Fused Load Interruptor Switches (FLIS) so you can stack multiple CBs in a single section. The entire concept is referred to as "Fault Tolerance". That is the up side.


The downside(s) of Metal Clad:
  • Large; Even though you can stack cells, the bus structures and racking mechanisms make it very very deep. Some as much as 96" deep, the shallowest are I think 54" deep.
  • Access; In addition, the line and load connections are all made at the back, so you cannot put MC gear up against a wall. Then the cells need a racking mechanism and a lift or small crane system to handle them, so you need a lot of room in front of them, usually more than the minimum switchgear clearance required by the NEC. That means a LOT of real estate.
  • Expensive; Metal Clad is the most expensive method available.

Metal Enclosed Insulated Switchgear (MEIS) on the other hand does not necessarily come with the same levels of isolation. There is little more than a thin sheet metal wall between one section and the next. As a result, the concept of fault tolerance is limited. To reduce the risk of collateral damage then, MEIS is almost always limited to using FLIS devices as the switching / protection units. That means, because of the size of the fuses involved, one "cell" per section. But the sections can be as shallow as 36", some even 30". In addition, MEIS is usually designed so that all service and connection can be doen from the front, so it can go up against a wall. So in general, MEIS can take up a little less overall real estate, but can fit in smaller rooms because of the shallower depth. As a result, MEIS is usually a lot less expensive.


The downside(s) of MEIS:
  • Less fault tolerance; If you have a catastrophic event somewhere, chances are good it will cause collateral damage and shut down a bigger part of your operation. In some cases, that is not much of an issue because if one part goes down, the rest MUST shut down anyway. But it warrants consideration. Sometimes the cheapest option up front ends up being the most expensive later on.
  • No Circuit Breakers; Some people like circuit breakers instead of fuses because they can be reset vs replaced. That is a longer argument than I will indulge in here, but it is a difference.
  • Less Flexible; If something changes, you can't just swap out or add a cell. You have to shut down, change or add on to the bus, then re-energize.
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jraef, your writing is so articulate, you must a been an english major, or writer or maybe just a dang good engineer/technician:D

thanks for the time you take to explain the important side if this work!:D
 
steveng said:
... you must a been an english major, or writer ...
Click to expand...

No, in fact I absolutely HATED English courses. I had to take English 101 in college 4 times before I passed it.

Lots of editing and a good spell checker... but thanks.

In my previous job I complained one day about how all of the literature was written by Engineers who, although brilliant, couldn't explain to an Eskimo how to make a snowball. So naturally, I got "elected" to rewrite all of the technical literature and training courses. Took me 10 years, I guess I developed a knack for it after a lot of review and reworking.

LOL, I just re-read it and found a spelling error anyway.
 
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