doble lemke power transformer advanced pd monitoring uhf 2009
TRANSCRIPT
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Advanced PD Monitoring of Power Transformers Supporting Asset Management
www.ldic.de
Gregor Pudlo
Doble Lemke GermanySwitzerland
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Abstract
• Reasons for (PD) monitoring of transformers
• Partial Discharge Detection principles
• Electrical PD diagnostic techniques• PD measuring circuits according to IEC 60270
• Advanced tools for PD monitoring• Acoustic and electromagnetic PD measuring principle
• Cone-shaped drain valve UHF-sensors / Performance Check
• Case studies – UHF PD measurements
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Reasons: PD Monitoring of Power Transformers
• Power transformers are the most important and expensive
pieces of equipment in substations.• A new power transformer costs millions of dollars.• Unplanned outage and repair costs, penalties, etc. sum up• Transformers design life is 20-35 years.• With proper maintenance they can remain in service for 60
years.• As transformers age, their internal conditions degrade which
increases the risk of failures.• Time-based maintenance changes to condition-based
maintenance approaches
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Partial Discharge Detection Principles
Optical
Mechanical
Chemical
Acoustic
Opto-acoustic
HV
Electrical IEC 60270
HF/VHF/UHF
Optical Effects(Light)
Pressure Wave(Sound)
Discharge EffectsDielectric LossesHigh Frequency
Waves
Chemical Effects
Heat
Macroscopic-PhysicalEffects
Detection Methods
Draft IEC 62 478
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Electrical PD diagnostic techniquesPD measuring circuits according to IEC 60270
a) coupling device in series with the coupling capacitor b) measurement at a bushing tap
Components:AC voltage source U, optional blocking impedance Z, coupling capacitor CK, measuring impedance Zm, a measuring instrument M and generalized test object Ca.
[König, 1993]
frequently used circuit in test laboratories
often applied in on-site/on-line PD investigations
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Electrical PD diagnostic techniquesPD Measuring Impedance for Bushing Tap Installation
• Decoupling of PD signals from the bushing tap
• in a wide frequency range up to 30 MHz
• Lower cut-off frequency < 60 kHz
• Additional voltage signal for phase-resolved
measurements
• Superimposed PD and test voltage signal
• Very fast and safe over-voltage protection
• TNC-socket for signal output
• Dimensions: diameter 125 mm, length 120 mm;
Weight: 2 kg
• Special feature for continuous PD monitoring (IP 68)
500 kV Transformer Bushing
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IEC 62478 - Draft level
"Non-conventional PD-measurements“:
• Electromagnetic PD Detection in the (HF/VHF/UHF) - range
• Acoustic PD measurements
• Mixed acoustic and electromagnetic method
-> PD location in Power Transformers and Reactors
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Advanced tools for PD monitoring – Electromagn. PD TestsCone-shaped active drain valve UHF-sensors
• for the decoupling of electromagnetic PD signals from the inner of an oil-paper-insulated
transformer
• PD-signals in the UHF frequency range
(mainly 300 MHz – 1 GHz)
• sensors support „Performance/Sensitivity Check“ (high-frequency test impulses can be injected with
additionally integrated electrode)
• sensor head is grounded (for lower frequencies)
• sensor application at oil valves, which are available e.g. for oil filling or draining (liquid tightness is
tested for 120°C warm oil with 5 bar compression)
View from inside the transformer
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Performance Check
• Functional check of the whole measuring path including sensors and partial discharge (PD)
acquisition system through injection of high-frequency test impulses
• „single-port“ solutions are possible
• the Performance Check „controls“ e.g. the effect of a contact to grounded elements within
the oil valve.
Cone-shaped active UHF-sensor (DN 50/80 oil gate-valve)
UHF PD spectra for grounded and ungrounded sensor head
input path
output path
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Transformer
Drain valve
UHF PD probe DN80
Output
Input
Pre-amplifier
High-pass filter
Performance Check
Performance check at 750 MHz
Phase-resolved view in UHF PD device LDS-6/UHF
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Advanced tools for PD monitoring – Electromagn. PD TestsCase study B - on-line UHF PD measur. of a 200 MVA single-phase transformer
380/220kV, 200 MVA single-phase transformer and position of the gate-valve UHF-sensor
UHF pulse recorded on-line
corresponding UHF PD spectrum up to 1.5 GHz
• customer wanted to verify the hydrogen measurements and locate potential PD
• full in-service sensor application and measurement
• UHF PD signal could be used to enhance acoustic PD measurements
Application benefit:
0 50 100 150 200-30
-20
-10
0
10
20
30
40
ampl
itude
(V
)
time (ns)
0.00 0.25 0.50 0.75 1.00 1.25 1.500.0
0.1
0.2
0.3
0.4
0.5
0.6
frequency (GHz)
ampl
itude
(Vs)
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Advanced tools for PD monitoring – Electromagn. PD TestsCase study C - on-line UHF PD measur. of a 3-phase power transformer 600 MVA
gate-valve UHF-sensor used at the 3-phase power transformer 600 MVA, 21/380kV
UHF pulse recorded on-line
corresponding UHF PD spectrum up to 1.0 GHz
• gas-in-oil hydrogen indication „useless“ due to active hot spot
• customer wanted to test for PD and check a potential load dependency of PD
• full in-service sensor application and measurement
• Inception and extinction voltage could be identified, load dependency excluded
Application benefit:
-500 -250 0 250 500 750 1000-150
-100
-50
0
50
100
150
ampl
itude
(m
V)
time (ns)
0.00 0.25 0.50 0.75 1.000
2
4
6
8
10
12
ampl
itude
(V
s)
frequency (GHz)
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UHF PD Measurements and delivered UHF PD Probe DN50/80
TaiwanTaipeh
ChinaShangai
BelgiumLinkebeek
GermanyBerlin HeidenauRiesa
Ireland & UKArdnacrusha CashlaDublin Louth
Philippines Manila
Saudi Arabia JeddahJizan
UAEDubai
EgyptKairo
ColombiaBogota
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UHF PD measurements in Ireland
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UHF PD measurements in Ireland
Application benefit:
• Tested measurements have been performed using non-conventional decoupling methods taking advantage of electromagnetic field coupling
• PD measurements on the power transformers have been functioned on the drain valves of the 3- phase 110/225kV power transformers with the help of the UHF probe DN 50
• Three transformers found with minor PD activity, one transformer with clear PD
Locations:
• Louth
• Dublin
• Ardnacrusha
• Cashla
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Drain Valve
Applied UHF Drain Valve Sensor
Mounting of the UHF Probe DN50 (with Adapter DN50/DN80)
Measuring System LDS-6/UHF
Measuring Instrument:
• PD Measuring System LDS-6/UHF• UHF Probe DN50 (with Adapter DN50/DN80)• UHF Calibrator LDC-6/UHF• Pre Amplifier LDA-5/GIS
UHF PD measurements in Ireland
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V ≈ 550 mV at measuring frequency 560 MHz
V ≈ 238 mV at measuring frequency 560 MHz
Left drain valve Right drain valve
V ≈ 139 mV at measuring frequency 560 MHz
V ≈ 128 mV at measuring frequency 520 MHz
UHF PD measurement in Louth, Dublin, Ardnacrusha, Cashla (Ireland)
Louth
T2xxxLeft drain valve Right drain valve
The measurements on both valves showed PD activity from inside the transformer.
Not any critical PD levels above the detection sensitivity have been measured in Dublin, Ardnacrusha and Cashla.
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UHF PD measurements in Jizan, Saudi Arabia
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UHF PD measurements in Jizan, Saudi Arabia
Drain Valve Power Transformer
on 33/13,8 KV Power Transformers “A” and “B”
Measuring Instrument:
• UHF Probe DN50
• Calibrator LDC-6/UHF
• PD measurement instrument LDS-6/UHF
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UHF PD measurements in Jizan, Saudi Arabia
PRPD Pattern at the measuring frequency of 400 MHz V = 177 mV
“A”
PRPD Pattern at the measuring frequency of 400 MHz V = 288 mV
“B”
Not any critical PD levels above the detection sensitivity have been measured.
Application benefit:
• For examination and diagnostics of the insulation quality of high voltage apparatus the measurement of PD is accomplished by sensitive UHF method on-site
• UHF probe applied in full operation of transformer, no outage needed
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Doble Lemke AGRheinfelden, SwitzerlandTel.: +41 61 836 8000www.ldic.ch
Doble Lemke GmbHKesselsdorf/Dresden,GermanyTel.: +49 35204 3900 0www.ldic.de
Conclusion• sensitive UHF PD measurement with UHF probes applicable in
service provide advantageous robust and easy PD decoupling • PD location - especially in transformers of great importance - is
possible in mixed and all-acoustic way• significant diagnostic information are derived from advanced
tools for PD monitoring • valuable application benefits e.g. on-line quick start of PD
monitoring, enabling time-based maintenance, “diagnostic double
checks”, etc. are at hand