Overview about research project “Energy handling capability”
Transcript of Overview about research project “Energy handling capability”
TUD High-Voltage Lab | Cigré WG A3.25 meeting | San Diego, October 16, 2012 | 1
Overview about research project “Energy handling capability”
Cigré WG A3.25 meetingSan Diego October 16, 2012Max Tuczek, Volker Hinrichsen, TU Darmstadt
Note: all information beginning from slide 21 are provisional results in the frame of Cigré WG A3.25 work, subject to possible corrections and extensions and not yet published. They shall, therefore, be used for personal or internal information only and not be further distributed. Care should be taken when conclusions shall be drawn.
Overview about research project “Energy handling capability”
Contents
Single impulse energy handling capability (A3.17)Energy handling capability for double impulse stressesRepeated AC energy impactsRepeated AC versus 90/200 µs energy impactsThermal stability of complete arresters and related simulation
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Max1's project
Max2's project
Overview about research project “Energy handling capability”
MO resistors, Size 1• Diameter (55…65) mm Typical for a Class 3 station arrester• Height (35…45) mm
MO resistors, Size 2• Diameter (37….45) mm Typical for a Class 1/10-kA arrester• Height (35…45) mm
Different aspect ratios
different failure mechanisms
• Several thousand samples from seven manufacturers worldwide• Most extensive energy handling research program on MO resistors so far
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Overview about research project “Energy handling capability”
Test current impulse shapes standard currents as per IEC 60099-4
Long duration current impulse• 1 ms• 2 ms• 4 ms
• Lightning discharge current 90/200 µs• High current impulse 4/10 µs: 65 kA … 200 kA
... plus non-standard stress:
Alternating current 50 Hz• î ≈ 10 A• î ≈ 100 A• î ≈ 300 A
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Overview about research project “Energy handling capability”
initial measurementUch1 at Ich = 0.12 mA/cm² (after 5 s)Pct1 at 0.8 x Uch1 (after 1 min)Ures1 at I = IN
exit measurementUch2 at Ich = 0.12 mA/cm² (after 5 s)Pct2 at 0.8 x Uch1 (after 1 min)Ures2 at I = INUres3 at I = 1.5 kA/cm²
Flowchart of the Test Procedure
Uch ... "characteristic" voltage; indicates changes of the U-I-characteristic in the continuous operating range; may be Uref
energy test with impulse
No
OK failed
Yes
initial measurement
exit measurement
mechanicallyfailed
New approach!
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Overview about research project “Energy handling capability”
Failure modes important for manufacturers
The different physical failure modes under single impulse stress (puncture, cracking, flashover, change of U-I-characteristics) are usually not of interest to the end-user.
But they do allow the manufacturers to assess their material and to design and optimize it with regard to particular aspects of energy handling capability.TUD High-Voltage Lab | Cigré WG A3.25 meeting | San Diego, October 16, 2012 | 6
Overview about research project “Energy handling capability”
exit measurement
OK failed
95 105ch1 ch2 ch1% %U U U⋅ ≤ ≤ ⋅
95 105res1 res2 res1% %U U U⋅ ≤ ≤ ⋅
mechanically failedduring residual voltage tests
Yes
Yes
Yes
NoNo
No!!!
!!!
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Overview about research project “Energy handling capability”
Size 1 (diameter ≈ 60 mm, height ≈ 40 mm)Manufacturers S, T, U, V, X, ZSize 1 (diameter ≈ 60 mm, height ≈ 40 mm)Manufacturers S, T, U, V, X, Z
Preliminary Results – 50% Failure Energy
Note: "rated" energies usually specified in the range 200 … 300 J/cm³
Failed by puncture and flashover of the coating system!
0200400600800
10001200140016001800
0.1 1 10 100 1000 10000
mea
nfa
ilure
ener
gyin
J/
cm³
peak current density in A/cm²
STUVXZ
AC
≈ 8 s
≈ 100 ms≈ 4 ms
≈ 250 µs
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Overview about research project “Energy handling capability”
WW
t
"Bath tub curve"WW
t
"Bath tub curve"
4ms 100 ms 10 s
• No minimum of energy handling capability for switching surges
Switchingduty
?
• There may be a minimum at > 10 s difficult to investigate (non-adiabatic)
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Overview about research project “Energy handling capability”
BR ÜB DU MF Uref Ures90/200 µs
1 ms2 ms
4 ms
0
20
40
60
80
100
% S
CR FO PU Uch Ures MFBR ÜB DU MF Uref Ures
90/200 µs1 ms
2 ms4 ms
0
20
40
60
80
100
% S
CR FO PUBR ÜB DU MF Uref Ures90/200 µs
1 ms2 ms
4 ms
0
20
40
60
80
100
% S
CR FO PU Uch Ures MF
BR ÜB DU MF Uref Ures
90/200 µs1 ms
2 ms4 ms
0
20
40
60
80
100
%
U
CR FO PU MF Uch Ures
BR ÜB DU MF Uref Ures
90/200 µs1 ms
2 ms4 ms
0
20
40
60
80
100
%
U
CR FO PU MF Uch Ures
Failure mechanisms:CR … CrackingFO … FlashoverPU … PunctureMF … Mechanical
failure during exit measurement
Uch ... Change of "characteristic"voltage
Ures... Change of residual voltage
Impulse shapes:4/10 µs90/200 µs 1 ms 2 ms 4 ms
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Overview about research project “Energy handling capability”
Failure mechanisms:CR … CrackingFO … FlashoverPU … PunctureMF … Mechanical
failure during exit measurement
Uch ... Change of "characteristic"voltage
Ures... Change of residual voltage
Impulse shapes:4/10 µs90/200 µs 1 ms 2 ms 4 ms
BR ÜB DU MF Uref Ures90/200 µs1 ms2 ms4 ms
0
20
40
60
80
100
% X
CR FO PU Uch Ures MF BR ÜB DU MF Uref Ures90/200 µs1 ms2 ms4 ms
0
20
40
60
80
100
% X
CR FO PUBR ÜB DU MF Uref Ures90/200 µs1 ms2 ms4 ms
0
20
40
60
80
100
% X
CR FO PU Uch Ures MF
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Overview about research project “Energy handling capability”
Comparison: with and without complex failure criterion
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Overview about research project “Energy handling capability”
0200400600800
10001200140016001800
10 100 1000 10000 100000
Mea
n fa
ilure
ene
rgy
in
J/cm
³
Amplitude of current density in A/cm²
SUVWXY
4/10 µs
90/200 µs
4 ms1 ms
Size 2 (diameter ≈ 40 mm, height ≈ 40 mm)Manufacturers S, U, V, W, Y Size 2 (diameter ≈ 40 mm, height ≈ 40 mm)Manufacturers S, U, V, W, Y
Failed by change of Uch!
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Overview about research project “Energy handling capability”
MFBR ÜB DU MF Uref Ures
4/10 µs1 ms
4 ms
0
20
40
60
80
100
% V
CR FO PU Uch Ures MFBR ÜB DU MF Uref Ures
4/10 µs1 ms
4 ms
0
20
40
60
80
100
% V
CR FO PU Uch Ures
BR ÜB DU MF Uref Ures4/10 µs
1 ms4 ms
0
20
40
60
80
100
% S
CR FO PU MF Uch Ures BR ÜB DU MF Uref Ures
4/10 µs1 ms
4 ms
0
20
40
60
80
100
% S
CR FO PU MF Uch Ures
BR ÜB
DU
MF
Ure
f
Ure
s
4/10 µs
1 ms
4 ms0
20
40
60
80
100
% U
CRFO
PUMF Uch
Ures
BR ÜB
DU
MF
Ure
f
Ure
s
4/10 µs
1 ms
4 ms0
20
40
60
80
100
% U
CRFO
PUMF Uch
Ures
BR ÜB DU MF Uref Ures4/10 µs
1 ms4 ms
0
20
40
60
80
100
% W
CR FO PU MF Uch Ures BR ÜB DU MF Uref Ures
4/10 µs1 ms
4 ms
0
20
40
60
80
100
% W
CR FO PU MF Uch Ures
Failure mechanisms:CR … CrackingFO … FlashoverPU … PunctureMF … Mechanical
failure during exit measurement
Uch ... Change of "characteristic"voltage
Ures... Change of residual voltage
Impulse shapes:4/10 µs90/200 µs 1 ms 2 ms 4 ms
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Overview about research project “Energy handling capability”
BR ÜB DU MF Uref Ures4/10 µs
2 ms0
20
40
60
80
100
% Y
CR FO PU MF Uch Ures BR ÜB DU MF Uref Ures4/10 µs
2 ms0
20
40
60
80
100
% Y
CR FO PU MF Uch Ures
Failure mechanisms:CR … CrackingFO … FlashoverPU … PunctureMF … Mechanical
failure during exit measurement
Uch ... Change of "characteristic"voltage
Ures... Change of residual voltage
Impulse shapes:4/10 µs90/200 µs 1 ms 2 ms 4 ms
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Overview about research project “Energy handling capability”
-40
-35
-30
-25
-20
-15
-10
-5
0
540000 60000 80000 100000 120000 140000 160000 180000 200000 220000
î in A
chan
ge o
f cha
r. v
olta
ge in
%
SUVWY
100 kA
Preliminary Results – 50% Failure EnergyChange of Characteristic Voltage for Size 2
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Overview about research project “Energy handling capability”
Different failure criteria0.1
1
10
100
1000
10000
0.1 1 10 100 1000 10000
Mea
n va
lue
of c
urre
nt d
ensi
ty
ampl
itude
in A
/cm
²
Time in msS T U V X Z [Rin 1997]
Ringler's varistors: diam. 62..64 mm, height: 23..24 mmCigré varistors: diam. 60 mm, height 40..45 mm
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Overview about research project “Energy handling capability”
0200400600800
10001200140016001800
0.1 1 10 100 1000 10000
Mea
n fa
ilure
ene
rgy
in J
/cm
³
Amplitude of current density in A/cm²
STUVXZ[Ringler 1997]
a.c.
4 ms
90/200 µs
1 ms
• Compared with former investigations (Ringler et al., 1997 see orange curve), an increase of (10…20)% in energy handling capability can be observed. These are the good news for the user!
Different failure criterion
Different failure mechanism for 90/200 µs
• But 90/200 µs impulses give impulse energy values lower than expected (influence of coating system!)
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Overview about research project “Energy handling capability”
Problem for Energy Specification: “Outliers”
0
200
400
600
800
1000
1200
1 5 9 13 17 21 25 29 33 37 41 45 49 53Versuchsnummer
Ener
gie
in J
/cm
³
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Overview about research project “Energy handling capability”
Preliminary Results – 50% Failure EnergyConclusions so far
• Compared with former investigations (Ringler 1997), energy handling capability has increased by 10…20 %.
• 50% failure energy is 4...5 times higher than actually specified "rated" energies; no figures can be derived for extremely low failure probabilities (<< 1%).
• The linear "log (current) vs. log (time to failure)" (Ringler) dependence could be verified, except for the new 90/200 µs impulse, where puncture and flashover of the coating may become the limiting factor potential for improvement; important for line arrester applications.
• Varistors for station and distribution application were directly compared only minor differences by different aspect ratios.
• "Mechanical failure" and "visible damage" are not sufficient failure criteria; changes of U-I-characteristics have to be considered as well.
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Overview about research project “Energy handling capability”
-10
-5
0
5
10
15
0 50 100
t in ms
U in
kV
-2
-1
0
1
2
3
I in
kA
Energy handling capability for double impulse stressesup to mechanical failure
mechanical failure of MOV
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LD current impulses
Overview about research project “Energy handling capability”
Energy handling capability for double impulse stressesup to mechanical failure
double impulse stresses
single impulse stresses
2 x 1.85 ms, d = 80 ms
2 x 1.85 ms, d = 3 s
1 x 2 ms
1 x 4 ms
40 MOV
1 make
size 2
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Overview about research project “Energy handling capability”
double impulse single impulse
impulse length/Time interval
1.85 ms/
3 s
1.85 ms/
80 ms2 ms 4 ms
(sum) mean failure energy
in p.u.1,04 1,02 1,02 1,0
Coefficient of variation 0,09 0,12 0,10 0,07
Energy handling capability for double impulse stressesup to mechanical failure
No difference in energy handling capability!
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Overview about research project “Energy handling capability”
initial measurement
energy pre-stress
exit measurement
cool down to ambient temperature
application of energy
n times
energy impact with AC
Repeated stresses
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Overview about research project “Energy handling capability”
initial measurement
energy pre-stress
exit measurement
cool down to ambient temperature
application of energy
n times
0
0,2
0,4
0,6
0,8
1
1,2
1,4
0 20 40 60 80 100
failu
re e
nerg
y in
p.u
.
number of previous impacts
Repeated stresses
No change in energy handling capability by ac pre-stresses!
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Overview about research project “Energy handling capability”
initial measurement
energy pre-stress
exit measurement
cool down to ambient temperature
application of energy
n times
0
1
2
3
4
5
0 20 40 60 80 100
mea
n ch
ange
of U
chin
%
number of previous impacts
Repeated stresses
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Overview about research project “Energy handling capability”
initial measurement
energy pre-stress
exit measurement
cool down to ambient temperature
application of energy
n times
energy impact with AC vs.
energy impact with 90/200 µs
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Overview about research project “Energy handling capability”
Energy impact with AC vs. 90/200 µs
Energy impact
90/200 µs
Impulse*)
200 J/cm³300 J/cm³400 J/cm³
4 cycles AC *)
200 J/cm³300 J/cm³400 J/cm³
*) max. 20 impulses or max. 20 times 4 cycles
Sample No. (each box = one sample; 20 samples per kind of stress
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#1
Overview about research project “Energy handling capability”
Energy impact with AC vs. 90/200 µs
Energy impact
90/200 µs
Impulse*)
200 J/cm³300 J/cm³400 J/cm³
4 cycles AC *)
200 J/cm³300 J/cm³400 J/cm³
*) max. 20 impulses or max. 20 times 4 cycles
Sample No. (each box = one sample; 20 samples per kind of stress
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#2
Overview about research project “Energy handling capability”
Energy impact with AC vs. 90/200 µs
Energy impact
90/200 µs
Impulse*)
200 J/cm³300 J/cm³400 J/cm³
4 cycles AC *)
200 J/cm³300 J/cm³400 J/cm³
*) max. 20 impulses or max. 20 times 4 cycles
Sample No. (each box = one sample; 20 samples per kind of stress
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#3 …. and so on
Overview about research project “Energy handling capability”
Energy impact with AC vs. 90/200 µs
Energy impact Varistor failure at impulse no. x
90/200 µs
Impulse
200 J/cm³
15
300 J/cm³400 J/cm³
3 13 14 15 15 15 16 16 16 16 17 17 18 19 19 19
4 cycles
AC
200 J/cm³
8
300 J/cm³
1 1 1 1
400 J/cm³
1 1 1 3 7 11 19
x
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Overview about research project “Energy handling capability”
Energy impact with AC vs. 90/200 µs
Energy impact Varistor failure at impulse no. x
90/200 µs
Impulse
200 J/cm³
15
300 J/cm³400 J/cm³
3 13 14 15 15 15 16 16 16 16 17 17 18 19 19 19
4 cycles
AC
200 J/cm³
8
300 J/cm³
1 1 1 1
400 J/cm³
1 1 1 3 7 11 19
x
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Overview about research project “Energy handling capability”
Application of energy (AC up to mechanical failure) after 20 pre-stresses
0.00
0.25
0.50
0.75
1.00
1.25
failu
re e
nerg
y in
p.u
.*) *) 1 p.u. = mean AC failure energy
Pre-stress:
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Overview about research project “Energy handling capability”
Summary/ Conclusions:for 400 J/cm³ at 90/200 µs many mechanical failures of MOV, but only after a high number (usually > 10) of stressesfor 300 J/cm³ and 400 J/cm³ at AC many mechanical failures just at the first impulsefor 400 J/cm³ at AC high failure rate at high number of stressesfor 90/200 µs remarkable reduction of energy handling capability; distinct decrease with increasing magnitude of pre-stress impulses; remaining max. failure energy = 10% of the mean AC failure energy!! for AC virtually no impact on energy handling capability by pre-stressesfor 200 J/cm³ at AC those samples failed at very low energy levels, which probably would have had failed at higher magnitude of pre-stresses Routine tests at AC considered more sensitive than LD impulse testing
Energy impact with AC vs. 90/200 µs
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Overview about research project “Energy handling capability”
Energy handling capability of “used” MOV (from grid)
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Overview about research project “Energy handling capability”
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MO resistor
Overview about research project “Energy handling capability”
Energy handling capability of “used” MOV (from grid)
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Main failure mechanism:Change of characteristic voltage
Overview about research project “Energy handling capability”
Thermal stability limit of complete EHV/UHV arresters
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Overview about research project “Energy handling capability”
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Overview about research project “Energy handling capability”
Uc Uc
energy impact
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Overview about research project “Energy handling capability”
t ambient ≈ 16 °C
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Overview about research project “Energy handling capability”
Arithmetic meantemperature, aboveambient temperature / K
thermalequival. 213,6 215,8
arresterwithgrading
215,0 220,8
arresterwithoutgrading
212,5 223,5
t ambient ≈ 16 °C
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Overview about research project “Energy handling capability”
Thermal stationary temperature at diff. ambient temperatures
0
50
100
150
200
250
0 5 10 15 20temperature (above ambient temperature) / K
heig
ht /
cm
22 °C
30 °C
40 °C
40 °C*
t ambient:
* with grading ring
TUD High-Voltage Lab | Cigré WG A3.25 meeting | Paris France, August 28, 2012 | 43
Overview about research project “Energy handling capability”
Thermal stability limit at different ambient temperatures
0
50
100
150
200
250
180 190 200 210 220 230 240 250
absolute temperature / °C
heig
ht /
cm
22 °C stable 22 °C instable
30 °C stable 30 °C instable
40 °C stable 40 °C instable
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Overview about research project “Energy handling capability”
Conclusions so far…. • Findings suggest that the importance of field grading may have
been overestimated in the past.
• Evidently, perfect grading is not essential to achieve.
• The manufacturer has mainly to determine the permissible operating temperatures in the upper part of the arrester, which is primarily a matter of material. A higher average overtemperatureunder continuous operation stress (U = Uc) will also reduce the thermal energy handling capability of the arrester, because the average temperature of an ungraded arrester will be higher than that of perfectly graded one (see slide 43).
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Overview about research project “Energy handling capability”
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Follow-up work in progress 1. Reproduction of the
experimentally found thermal behavior by a coupled thermal and non-linear resistive/capacitiveFEM simulation
2. Application and validation of thesimulation model to simulatethermal stability under real conditions (temperature riseadiabatically and in zero time)
3. Simulation: "Playing" with theexternal grading system foroptimization purposes
Tem
pera
ture
Time
Experiment
Simulation