2. KONTRAK PERKULIAHAN
KEHADIRAN 75 % DARI TOTAL PERKULIAHAN ( 16 x atau 14 x)
TUGAS DIKUMPUL TEPAT WAKTU / tidak boleh kopian tugas temannya
PEMBAGIAN NILAI
Tugas harian (Total 10 %)
Tugas lainnya (15 % ) = Quiz, presentasi jurnal
UTS (20 %)
UAS (20 %)
Absensi (5 %) =
3. SILABUS
FENOMENA PETIR
MEKANISME BREAKDOWN PADA zat GAS, CAIRAN, dan PADAT
MEKANISME BREAKDOWN PADA vacuum
PEMBANGKITAN TEGANGAN AC DAN DC
PEMBANGKITAN TEGANGAN IMPULS
PENGUKURAN TEGANGAN TINGGI
PENGUJIAN TEGANGAN TINGGI
PENGUJIAN INSULASI TEGANGAN TINGGI TIDAK MERUSAK
4. DAFTAR PERPUSTAKAAN
High Voltage Engineering, C.L Cadwa
High Voltage Engineering : Fundamental , E.Kuffel dkk
Advances in High Voltage Engineering , A .Haddad dkk
9. History BENJAMIN Franklin
1706 = Born
1732 = founded Library Company in Philadelphia. Achieved a new insight
Into electrical science with his definition of a ‘single electric fire’
1750 = a needle brought near to a charged conductor caused a spark,
but when further away discharged the conductor silently (a
mechanism today known as a glow corona).
1752 = famous Philadelphia Experiment (performed under Franklin’s direction by
d’Alibard in France in 1752) point discharges were used to prove the
electrification of the thundercloud and to identify correctly the
direction of the field formed by the cloud charges
10. History BENJAMIN Franklin
Franklin, in fact, had envisaged from his laboratory tests two complementary
concepts for the function of a lightning rod:
• the possible harmless discharge of the cloud
• the attraction of the flash and the conduction of the charge safely to
ground.
11. Next Step about Lightning
1777 = Benjamin Wilson indeed suggested that sharp points might be too attractive to
the flash, and he favoured spheres.
18th = Preece proposed a quantification of the zone of protection that is afforded by a
vertical mast; he anticipated the modern rolling sphere concept, and set the
sphere
radius equal to the striking distance, which was itself equated to the mast
height.
This leads to a protection angle of 45◦.
1920s and 1930s = Schonland made electric field measurements and, having
collected data f rom some 23 storms, showed the cloud base to be
negatively charged as Franklin had proposed.
1974 = The statistics of the lightning current and its rate of rise, on the other
hand, determine the severity of the resultant strike by Berger at Mt San Salvatore in Italy
12. Karakteristik SAMBARAN
Data from Anderson and Eriksson, Berger, Gary, Uman and many others have
quantified lightning parameter characteristics in respect of:
1 incidence of ground flashes
2 flash polarity
3 structure height
4 multiple strokes
5 flash duration
6 peak currents in first and subsequent strokes
7 current shapes.
13. 1. INCIDENCE
Data on ground flash density
Ng = Flashes per square kilometer per annum)
Td = Mean Number Thunderstorm Days
Td between 4 and 80, in Indonesia Td = 270
14. 1. INCIDENCE
The number of ground flashes in a given region can be greatly increased by the
frequency of strikes to tall structures.
Structures of h > 400 m involved 95 per cent upward flashes (where the lightning
flash was initiated by a leader from the structure).
For h < 100 m, upward leaders caused initiation of only ten per cent of strikes.
For structure greater than 100 m Nu represented by equation :
16. 2.Polarity
In the first place, field studies suggest that the highest peak currents are associated with
positive flashes.
Second, analogies with the long laboratory spark, and some generic models of the
mechanism of strikes to grounded structures , both indicate that the protection of
structures from positive direct strikes with standard air terminations may sometimes be
much less effective than for the more common negative flash.
Over 29 years of observation, Berger recorded 1466 negative flashes and 222 positive
flashes.
At Peissenberg, Fuchs found that 95 per cent were of negative polarity. There is
evidence that winter storms in some regions (e.g. Japan and northeast USA [25, 26]) or
lightning to high altitude locations may more commonly result in positive flashes
17. 3.Flash Component
Schonland and Collens [7] showed from electric field change measurements that
the flash often comprised multiple successive strokes. The mean strokes/flash
value was 2.3, and the points of strike to ground of individual strokes may be
significantly displaced (They found probability values of:
In Schonland’s work the mean flash duration was estimated to be 200 ms, and:
18. 4. Peak Current
Berger’s measurements of the peak current probability distributions for return
strokes preceded by negative stepped and dart leaders, and for positive lightning,
were of log-normal form and ranged from a few kA to above l00 kA with a median
value of about 30 kA.
The overall median peak current in the first stroke of a flash was 34 kA, and for
high current flashes:
On the basis of recent data from such systems, Darveniza [37] has suggested that
a median current of about 20 kA is more appropriate than the long accepted values
of 31 kA (CIGRE) or 33 kA (IEC)
19. 5.Current Shape
The rate of change of current measured by Berger in the first and later strokes of
the flash may be represented by:
Berger’s measurements also provide mean values for the current tail duration and
its statistical range:
20. 6.Electric Fields
The electric field at ground level is observed to change from the fair weather value
of about +130 V/m (created by the -0.6 MC negative charge on the earth) to a
maximum -15 or -20 kV/m below the bipolar charge of a thundercloud, the negative
charge centre being at a lower altitude (about 5 km) than the main positive charge
(10 km).
These are large charges of about ±40 C, which create a cloud to ground potential
of the order of 100 MV
22. 7. Spatial Development
The overall behaviour of a negative strike to
ground, as summarised by Berger [24] is that
in most cases a down-coming first negative
leader is initiated at an altitude of about 5 to
10 km, advancing apparently discontinuously
in steps of 10–200 m length (mean value 25
m) at intervals of 10–100 μs (mean 50 μs),
and establishes a path for the ensuing
upwardly-directed first return stroke.
