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had 62 circuits and a fortnightly intensity
of 29.1 E. The measured traffic volume
exceeded 250 MEh. The complete study
is published in [5].
Concerning one circuit-group, the first
year’s peak load time was identified, and
the expected time and intensity 26 fortnights
later were searched. The expected
values were compared with the real second
year’s peak load time and intensity.
The timing error dt and the intensity loss
y % characterise that circuit-group, Figure
1.
If the ElCo about seasons were valid, all
the circuit-groups were concentrated to
point dt = 0, y % = 0. In fact, the ElCo
about seasons was fulfilled only in a
minority of cases, the rest indicating a
wide scattering in dt-y %-plane, Figure 2.
An analysis was done by projecting the
points in Figure 2 to the dt-axis, one by
one. The dt-axis projection of these numbers,
Figure 3, indicates that
- the full validity of ElCo about seasons
realised in 305 of 2728 circuit-groups,
i.e. 11.1 % of cases; a random result
would be 1/26 = 3.8 %;
- the moderate validity of ElCo about
seasons by timing error of dt being at
least two fortnights realised in 31 % of
the circuit-groups, the random being
5/26 = 19.2 %, and
- measurements have to last for six fortnights
(three months) in order to discover
the highest fortnight of at least
every second circuit-group.
The y %-axis projection, Figure 4, indicates
that
- the average intensity error is 7.6 %,
being large (14 %) for low, up to ten
erlangs, and low (5 %) for high traffic,
at least one hundred erlangs
- if a reliability of 90 % is aimed at, the
pre-selected fortnight intensity must be
exceeded by 25 %. It means corresponding
overdimensioning on an
average, leaving, however, every tenth
intensity value underestimated.
The average intensity error in classes of
timing error is presented in Figure 5. It
indicates that when deviating from the
perfect timing, the intensity error suddenly
jumps to the rather constant high
values, i.e. the highest fortnight does not
stay in the neighbourhood of the earlier
peak season, but appears at an arbitrary
number of fortnights apart.
n
300
250
200
150
100
50
0
(%)
20
15
10
5
0.0-0.0
2.0-2.9
4.0-4.9
8.0-8.9
12.0-12.9
16.0-16.9
20.0-20.9
24.0-24.9
Figure 4 Distribution of intensity errors y % [5]
4
9
19
15
10
12
15
22
23
32
19
30
33
36
34
49
43
70
57
67
69
64
64
98
157
305
159
122
79
64
64
73
60
86
94
49
75
48
39
20
28
31
34
51
44
24
37
28
25
21
8
0
-25 -20 -15 -10 -5 -1 01 5 10 15 20 25
Fortnightly scale
[2 weeks]
Figure 5 Average intensity errors in different timing error classes [5]
The validity of ElCo about seasons is less
than 50 %. The high season thus cannot
be nominated in advance, but intensities
of consecutive fortnights can vary
strongly. Only the low loads during summer
vacations can be identified, the
decrease being on an average of 30 %.
Since the high load timing is not predictable,
the measurement has to last for
periods totalling at least six months,
uninterrupted or in shorter periods.
28.0-28.9
32.0-32.9
36.0-36.9
40.0-40.9
44.0-44.9
4 The stability of the
peak-hour in
measurement rounds
The ElCo about measurement rounds is
that the peak-hour of the average day in
a measurement round of a circuit-group
is stable from season to season. If the
ElCo about measurement round is valid,
the intensity measurements can be con-
71