TRANSMISSION &
DISTRIBUTION
A Division of Global Power
POWER SYSTEM STABILITY CALCULATION TRAINING
D6
AblfStMdl
D
ay
6
-
A
ssem
bl
y o
f

S
ys
t
em
M
o
d
e
l
s
November 22, 2013Prepared by: Mohamed El Chehaly
eBook for You
OUTLINE
2
OUTLINE

 Study system: Buses subject to detailed
study; all components are represented
explicitly
 External system: Buses and branches that
connect to and influence a study system
but do not need to be represented
but

do

not

need

to

be

represented
 Boundary buses: buses in the study
system that connect to external systems
system

that

connect

to

external

If no swing buses assign a generator bus (code
3
.
If

no

swing

buses
,
assign

a

generator

bus

(code

2) in the study system to be a new swing bus
(code 3)
4. Solve the load flow. No changes to the power
levels should be observed
eBook for You
Steps for Equivalent Network
7
REDUCED POWER SYSTEM
Steps


the

power

flows

of

the

tie

lines

that

connect

the

boundary buses to the external system (DO NOT
SOLVE)
3
Di tth ti li th t tth
3
.
Di
sconnec
t

fl
ow
2. The load flow could not be solve due to the large
number of islanded buses
number

of

islanded

buses
3. The following message should appear:
Message for API FDNS
#### buses in island(s) without a swing bus
Use activity TREE
eBook for You
Steps for Equivalent Network
9
REDUCED POWER SYSTEM
Steps

for

Equivalent

Network
4. Islanded buses
1. Write TREE in the CLI window
2. The following message should appear:
3. To disconnect the island, write ‘1’ in the CLI

and single
-
line
-
to
-
ground) at the boundary buses
and

single
line
to
ground)

at

the

boundary

buses

in the original system both in physical output
(MVA and A) and in per unit (pu) and in polar
coordinates
coordinates
2. Add a dummy generator at the boundary bus of
the modified s
y
stem with zero

external system and calculate the short-circuit
level in MVA
5
In the reduced system change the rating of the
5
.
In

the

reduced

system
,
change

the

rating

of

the

equivalent generator to the value found in step 4
6. Chan
g
e the im
p
edances of the

y sys
t
em
1. Verify that the power flows within the study
system match the original power flows
system

match

the

original

power

flows
2. If there is a large difference, add loads that
compensate this difference
3. Check that the power flows should be within 5%
of the original ones found in the complete system
4
Voltages and angles at all buses in the equivalent
4
.
Voltages

and

angles


omp
l
e
t
e
d
equ
i
va
l
en
t
ne
t
wor
k
1. The equivalent network is now completed
2
The buses of the external systems can be
2
.
The

buses

of

the

external

System
 Vietnamese Map
Pl ik
External System
Pl
e
ik
u
Study System
eBook for You
Vietnamese Power System
15
REDUCED POWER SYSTEM
Vietnamese

Power

System
 500 kV system
Boundary bus
External System
Boundary

bus
Study System
eBook for You
Vietnamese Power System
16
REDUCED POWER SYSTEM
Vietnamese


is

chosen

to

be

an

additional swing bus: PMY_1_S4 (bus 52040)
 Solve the load flow
eBook for You
Vietnamese Power System
18
REDUCED POWER SYSTEM
Vietnamese

Power

System
2. Swing buses in the external system
 Change all the other swing buses to generator
buses
 Add loads at the boundary bus corresponding to
the flows in the tie lines
eBook for You
Vietnamese Power System
19

di
sconnec
t
eBook for You
Vietnamese Power System
21
REDUCED POWER SYSTEM
Vietnamese

Power

System
4. Islanded buses

Repeat for all islands

Repeat

for

all

islands
eBook for You
Vietnamese Power System
22
REDUCED POWER SYSTEM
Vietnamese

Power


original

system

is:
eBook for You
Vietnamese Power System
23
REDUCED POWER SYSTEM
Vietnamese

Power

System
5
Sh t
iitll
5
.
Sh
or
t
-c
i
rcu
it

l
eve

iitll
5
.
Sh
or
t
-c
i
rcu
it

l
eve
l
s
 In order to get the impedance of the equivalent
machine the following equations have to be
machine
,
the

following

equations

have

to

be

eBook for You
Vietnamese Power System
25
REDUCED POWER SYSTEM
Vietnamese

Power

System
5
Sh t
iitll
5
.
Sh
or
t
-c
i
rcu
it

l
eve
l
s
 In order to get the impedance of the equivalent
machine the following equations have to be
machine
,

1


Base: 100 MVA
pu
X
04389
.
0
0

eBook for You