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8/10/2019 Electrical-Engineering-portal.com-Main and Transfer Inspection Bus Arrangement Commonly Used in AIS (1)
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electrical-engineering-portal.com
http://electrical-engineering-portal.com/main-and-transfer-bus-arrangement-commonly-used-in-ais
Main and Transfer (Inspection) Bus Arrangement commonly
used in AIS
Main and Transfer (Inspection) Bus Arrangement commonly used in AIS (on photo: Air insulated substation in Kuwait; credit: ABB)
For low reliability requirement situations
The main and transfer bus configuration connects all circuits between the main bus and a transfer bus
(sometimes referred to as an inspection bus). Some arrangements include a bus tie breaker and others simply
utilize switches for the tie between the two buses.
This configuration is similar to the single bus arrangement; in that during normal operations, all circuits are
connected to the main bus.
So the operating reliability is low; a main bus fault will de-energize all circuits.
However, the transfer bus is used to improve the maintenance process by moving the line of the circuit breaker
to be maintained to the transfer bus. Some systems are operated with the transfer bus normally de-energized.
When a circuit breaker needs to be maintained, the transfer bus is energized through the tie breaker.
Then the switch, nearest the transfer bus, on the circuit to be maintained is closed and its breaker and associated
isolation switches are opened. Thus transferring the line of the circuit breaker to be maintained to the bus tie
breaker and avoiding interruption to the circuit load.
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Figure 1 – Main and transfer bus arrangement.
Without a bus tie breaker and only bus tie
switches, there are two options:
1st option
The first option is by transferring the circuit to
be maintained to one of the remaining circuits
by closing that circuit’s switch (nearest to the
transfer bus) and carrying both circuit loads onthe one breaker.
This arrangement most likely will require
special relay settings for the circuit breaker
to carry the transferred load.
2nd option
The second option is by transferring the
circuit to be maintained directly to the main bus
with no relay protection from the substation.
Obviously in the latter arrangement, relay
protection (recloser or fuse) immediately
outside the substation should be considered to
minimizefaults on the maintained line circuit
from causing extensive station outages.
The cost of the main and transfer bus arrangement is more than the single bus arrangement because of the
added transfer bus and switching devices. In addition, if a low-profile configuration is used, land requirements are
substantially more.
Connections of lines to the station should not be very complicated. If a bus tie breaker is not installed,
consideration as to normal line loading is important for transfers during maintenance. If lines are normally
operated at or close to their capability, loads will need to be transferred or temporary generators provided similar
to the single bus arrangement maintenance scenario.
The main and transfer bus arrangement is an initial stage configuration, since a single main bus failure can
cause an outage of the entire station.
As load levels at the station rise, consideration of a main bus tie breaker should be made to
minimize the amount of load dropped for a single contingency.
Another operational capability of this configuration is that the main bus can be taken out-of-service without an
outage to the circuits by supplying from the transfer bus, but obviously, relay protection (recloser or fuse)
immediately outside the substation should be considered to minimize faults on any of the line circuit from causing
station outages.
Application of this type of configuration should be limited to low reliability requirement situations.
Switching operation
1. First close the isolators at both side of the bus coupler breaker.
2. Then close the bypass isolator of the feeder which is to be transferred to transfer bus.
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3. Now energized the transfer bus by dosing the bus coupler circuit breaker from remote.
4. After bus coupler breaker is closed, now the power from main bus flows to the feeder line through its main
breaker as well as bus coupler breaker viatransfer bus.
5. Now if main breaker of the feeder is switched off, total power flow will instantaneously shift to the bus
coupler breaker and hence this breaker will serve the purpose of protection for the feeder.
6. At last the operating personnel open the isolators at both sides of the main circuit breaker to make it
isolated from rest of the live system.
References:
Air-Insulated Substations — Bus Switching Configurations / Michael J. Bio
Substation layout and accessories and busbar arrangement – Amit Kumar, Nejamul Hoque and
Hemendra Kumar Rajput
About Author //
Edvard Csanyi
Edvard - Electrical engineer, programmer and founder of EEP. Highly specialized for
design of LV high power busbar trunking (<6300A) in power substations, buildings and
industry fascilities. Designing of LV/MV switchgears. Professional in AutoCAD
programming and web-design. Present on Google+
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3 Comments
1.
V Sivakumar Reddy
Nov 22, 2014
Thank you very much for all your efforts and valuable info.
(reply)
2.Lakshma Reddy
Sep 04, 2014
Very useful info..
(reply)
3.
Pankaj Vitthal Chavan
Aug 14, 2014
Very Good & usefull Articlefor me & everyone
(reply)
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