dr audih - bau.edu.jo isolator for circuit breaker maintenance circuit breaker isolator feeder...
Post on 06-Feb-2018
Embed Size (px)
Dr Audih 1
Sub-stations are important part of power system ,its
responsible to transfer some characteristic such as (voltage,
frequency, p.f. etc.) of electric supply.
The important points must take in consideration while laying
out a sub-station ,the substation should be:
Located at a proper site ( At the load centre ).
Provide safe and reliable arrangement.
Easily operated and maintained.
Minimum capital cost.
The sub-station has many components (e.g. circuit breakers,
switches, fuses, instruments etc.) which ensure continuous
and reliable service.
2 Dr Audih
Low tension oil circuit breaker
3 Dr Audih
The sub-stations are classified as :
1- Pole-mounted sub-station
4 Dr Audih
The underground sub-station requires more careful
consideration than other types of sub-stations:
(i) The size of the station should be as minimum as possible.
(ii) Reasonable access for equipment and personnel.
(iii) Lighting secured and protection against fire.
(iv) Good ventilation.
(v) Remote indication of the rise in temperature so H.V.
supply can be disconnected.
(vi) The transformers, switches and fuses should be air
5 Dr Audih
Dr Audih 6
3- Outdoor sub-station
Dr Audih 7
4- Indoor sub-station
8 Dr Audih
Symbols for Equipment in Sub-Stations
9 Dr Audih
10 Dr Audih
1- Security of supply:
Security of supply (reliability) : In terms of the effect of the loss
of supply. The British Code for the design of high voltage open
terminal substations BS 7354 categorizes substation service
as the following categories:
Category 1: No outage (maximum security of supply).
Category 2 : Short outage to transfer the load to an alternative
circuit in case of maintenance or fault conditions.
Category 3: Loss of a circuit or section.
Category 4: Loss of substation.
11 Dr Audih
Three switch mesh
Mesh arrangement (three switch mesh.)
1-only three circuit breakers controlling
2-Any circuit breaker may be maintained
at any time without disconnecting that
circuit. **Note: (all busbars, circuit breakers (CB)and
disconnectors must be capable of carrying the
combined loads of both transformers and line circuit
3-Normal operation is with the bypass
disconnectors and optional circuit
breaker open so in case of
maintenance or fault we transfer using
12 Dr Audih
4-In case of a fault on one transformer circuit, we can disconnect,
and the healthy transformer circuit continue the supply without
affecting the feeders.
5-A fault on the bus section circuit breaker causes complete
substation shutdown until isolate the fault and power restored.
full mesh circuit:
Is composed from three switch's arrangement for multiple
circuit sub-stations is the full mesh layout as shown in Fig.
section circuit breaker
13 Dr Audih
1- Operation of two circuit breakers is required to connect or
disconnect a circuit and disconnection involves opening
2- Line or transformer circuit disconnectors may then be
used to isolate the particular circuit and the mesh
3- Circuit breakers may be maintained without loss of supply .
4- Busbar faults will only cause the loss of one circuit.
14 Dr Audih
The ring busbar offers increased security compared to the
single busbar arrangement. A typical scheme which would
occupy more space than the single busbar arrangement is
shown in Fig.
15 Dr Audih
Category 1 :
For maximum security of supply within the substation for
maintenance or fault , the ( one and half ) 1 and 12 circuit
breaker scheme is used .
Bypass isolator for circuit breaker maintenance
16 Dr Audih
GIS 132kV substation double switchyard arrangement indoor
17 Dr Audih
This scheme is used at important high voltage sub-stations
and large generating.
1- Additional costs of circuit breakers are involved together
with complex protection arrangements.
2- It is possible to operate with any one pair of circuits, or
group of the circuits separated from the remaining circuits.
3- The circuit breakers and other system components must be
rated for the sum of the load currents of two circuits.
4- High security against loss of supply.
5- High cost
18 Dr Audih
Tow schemes are Used :
1-Double busbar arrangement with transfer busbar
arrangement . This arrangement consists of:
Two bus-bars, a main bus-bar and a spare bus-bar. Its
the most popular open terminal outdoor substation. Which
offering the flexibility to allow the grouping of circuits onto
separate busbars to transfer one busbar to another for
-When circuit breakers are
under maintenance the
protection is arranged to
trip the bus coupler
-The system less flexibility.
19 Dr Audih
2- Double busbar scheme with bypass disconnector and bus-
Each circuit may be connected to either busbar using the
busbar selector disconnectors.
On-load busbar selection may be done using the bus-coupler
20 Dr Audih
21 Dr Audih
- Motorized busbar selector disconnectors may be used to
reduce the time to reconfigure the circuit arrangements.
- Busbar and busbar disconnector maintenance may be
carried out without loss of supply to more than one circuit.
- The use of circuit breaker bypass isolator facilities is not
considered to offer substantial benefits since modern
circuit breaker maintenance times are short and in highly
interconnected systems alternative feeder arrangements
are normally possible.
22 Dr Audih
Single busbar scheme is use
Simple to operate, in figure we illustrates a five circuit breaker
single busbar arrangement with four feeder circuits, one bus
section and ten disconnectors.
- Each circuit is protected by
its own circuit breaker.
- A fault on a feeder or
transformer circuit breaker
causes loss of the
transformer and feeder
circuit which may be
restored after isolating the
faulty circuit breaker.
23 Dr Audih
24 Dr Audih
O.C.B oil circuit breaker C.T current transformer L.A lightning arrester P.T. Power transformer
25 Dr Audih
- A fault on a bus section circuit breaker causes complete
shutdown of the sub-station. All circuits may be restored
after isolating the faulty circuit breaker .
- A busbar fault causes loss of one transformer and one
feeder. Maintenance of one busbar section or disconnector
will cause the temporary outage of two circuits.
- Maintenance of a feeder or transformer circuit breaker
involves loss of that circuit. The introduction of bypass
isolators between the busbar and circuit isolator as in
( Fig.a) allows circuit breaker
maintenance without loss of the
circuit. Bypass may also be
obtained by using a
disconnector on the out-going
ways between two switchgear
bays (Fig. b). Fig.a Fig. b
26 Dr Audih
Single bus bar without by pass section in busbar is used.
- Radial busbar arrangement is used this decreased security
compared to the double busbar arrangement since no
alternative power flow routes are available.
- This scheme occupy less space than the
other arrangements and is cheaper.
- A fault on a feeder or transformer circuit breaker
causes loss of the transformer and feeder circuit.
27 Dr Audih
2 Extendibility :-
The design should allow for future extendibility (bays known
as skeleton bays for switchgear ,overhead line or cable
Note :Gas insulated switchgear (GIS) not permit to add any
future extension work.
In open terminal switchyard arrangement allows the user a
choice of switchgear for future extension work.
The design must take into account the electricity supply
company system planning and operations procedures of
reliability and maintenance requirements for the proposed
28 Dr Audih
Portable earthing points and earthing switch/interlock requirements will
also need careful consideration. Similarly standard minimum clearances