Single breaker vs multi breaker outfits

[mbrooke]

What is the advantage of single breaker double / triple buss over ring, breaker-and-a-half and double breaker double buss? In the North America most 345kv and 115kv substations are ring buss or breaker and a half, while single breaker double bus and single breaker triple bus is common through out the rest of the world. Why do EEs go through all the trouble of 3 bus bars and 3 isolaters for a single breaker rather than simply going ring or breaker and a half?

 

[kingpb]

What is the advantage of single breaker double / triple buss over ring, breaker-and-a-half and double breaker double buss? In the North America most 345kv and 115kv substations are ring buss or breaker and a half, while single breaker double bus and single breaker triple bus is common through out the rest of the world. Why do EE's go through all the trouble of 3 bus bars and 3 isolators for a single breaker rather than simply going ring or breaker and a half?

A little long but good info-

Single Bus Advantages:
• Lowest cost
• Small land area
• Easily expandable
• Simple in concept and operation
• Relatively simple for the application of protective relaying

Single Bus Disadvantages:
• Single bus arrangement has the lowest reliability
• Failure of a circuit breaker or a bus fault causes loss of entire substation
• Maintenance switching can complicate and disable some of the protection schemes and
overall relay coordination

Sectionalized Bus - Is an extension of the Single Bus

Sectionalized Bus Advantages:
• Flexible operation
• Isolation of bus sections for maintenance
• Loss of only part of the substation for a breaker failure or bus fault

Sectionalized Bus Disadvantages:
• Additional circuit breakers needed for sectionalizing, thus higher cost
• Sectionalizing may cause interruption of non-faulted circuits

Main and Transfer Bus - These are two separate and independent Buses, normally all connected to main bus, breakers can be isolated for maintenance by using the transfer bus.

Main and Transfer Bus Advantages:
• Maintain service and protection during circuit breaker maintenance
• Reasonable in cost
• Fairly small land area
• Easily expandable

Main and Transfer Bus Disadvantages:
• Additional circuit breaker needed for bus tie
• Protection and relaying may become complicated
• Bus fault causes loss of the entire substation

Ring Bus - This is an extension of the sectionalized bus. it provided greater reliability and flexible operation by being able to isolated.

Ring Bus Advantages:
• Flexible operation
• High reliability
• Double feed to each circuit
• No main buses
• Expandable to breaker-and-a-half configuration
• Isolation of bus sections and circuit breakers for maintenance without circuit disruption

Ring Bus Disadvantages:
• During fault, splitting of the ring may leave undesirable circuit combinations
• Each circuit has to have its own potential source for relaying
• Usually limited to 4 circuit positions, although larger sizes up to 10 are in service. 6 is
usually the maximum terminals for a ring bus

Breaker-and-a-half - has two buses but unlike main and transfer, both buses are always energized. For every two circuit there are 3 breakers. any breaker can be removed without service. Ring buses are often updated to this.

Breaker-and-a-Half Advantages:
• Flexible operation and high reliability
• Isolation of either bus without service disruption
• Isolation of any breaker for maintenance without service disruption
• Double feed to each circuit
• Bus fault does not interrupt service to any circuits
• All switching is done with circuit breakers

Breaker-and-a-Half Disadvantages:
• One-and-a-half breakers needed for each circuit
• More complicated relaying as the center breaker has to act on faults for either of the 2
circuits it is associated with
• Each circuit should have its own potential source for relaying

Double Bus/Double Breaker - 2 main buses normally energized. each circuit require 2 breakers; any breaker can fail an only affect one circuit. Double

Breaker-Double Bus Advantages:
• Flexible operation and very high reliability
• Isolation of either bus, or any breaker without disrupting service
• Double feed to each circuit
• No interruption of service to any circuit from a bus fault
• Loss of one circuit per breaker failure
• All switching with circuit breakers

Double Breaker-Double Bus Disadvantages:
• Very high cost – 2 breakers per circuit

 

[mbrooke]

Thank you, this is a big help, very worth it!


But in regards to protective relaying, how do these schemes pan out? Is having dynamic buss zones really less complicated then having relaying take into account two breakers?

 

[mbrooke]

Reading the info I am wondering about what is meant by this in regards to main and transfer:

Protection and relaying may become complicated

How so, isn't main and transfer like relaying a single buss? :?