Environmental Engineering Reference
In-Depth Information
Table 4.1
Electrical power losses of DNOs in the UK
DNO company
1990/1991
1995/1996
2000/2001
Eastern
7.0
6.9
7.1
East Midlands
6.6
6.1
6.0
Hydro Electric
9.3
8.9
9.1
London
7.8
6.7
7.3
Manweb
9.8
8.8
9.1
Northern
7.5
6.8
6.6
Norweb
7.1
4.8
6.2
Scottish Power
8.5
6.7
7.2
Seeboard
7.9
7.1
7.6
Southern
7.1
7.2
7.2
South Wales
8.9
6.7
7.2
South Western
8.6
7.2
7.9
Yorkshire
6.3
6.5
6.6
Average
7.6
6.7
7.0
Overload and fault current capability;
●
Long electrical and mechanical life expectancy.
●
Figure 4.2 shows the different elements conforming an OLTC unit which is
usually located inside a transformer tank and hanging from the transformer cover.
Power to run the OLTC is given by the motor-drive mechanism, that is placed adja-
cent to the transformer, as a consequence power is provided by means of shafts and
gears.
4.1.2 OLTC modelling equations
An ideal transformer connecting nodes
k
and
m
, as illustrated in Figure 4.3, is taken
as a reference to build the relationship between voltages and currents.
To begin with, the voltage ratio between terminals of the ideal transformer
denoted as
k
and
m
can be detailed as:
V
k
V
k
=
1
(4.1)
|
t
| ∠
τ
S
primary
=
S
secondary
(4.2)
V
k
(
I
km
)
∗
V
k
I
km
=
(4.3)
Taking (4.1) and combining it with (4.3) yield the complex control variable for
the OLTC device:
V
k
I
km
(
I
km
)
∗
|
t
| ∠
τ
=
V
k
=
(4.4)
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