Online Monitoring of

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Online Monitoring of Dissipation
Factor Dayashankar Dubey (MTech) Suhas P.
Solanki, MTech Guide Prof PC Pandey EE
Dept, IIT Bombay
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ABSTRACT The insulation status in HV equipment
can be monitored by dissipation factor
measurement. Online monitoring of dissipation
factor is based on dividing the actual power by
apparent power. Sampling rate lower than the
power line frequency results in aliased periodic
waveforms which retain the original phase
relationship, and these waveforms can be
processed at a relatively low computational
speed. Numerical simulation has been carried out
to study the effect of quantization error with
different number of bits, for finding the effect
of different filters used in processing, effect
of harmonics, and variation in power line
frequency.
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• INTRODUCTION
• Lossy Capacitor
• Dissipation factor of lossy dielectric
• Loss angle ?, dissipation factor tan?
• Parallel model
  Series model
• 
  
  

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• Monitoring of dissipation factor
• ? Insulation deterioration ? increase in ?
• ? Monitoring of ? or dissipation factor ? safe
  reliable operation of HV equipment
• Online monitoring of dissipation factor
• ? HV equipment need not be removed from service
• ? Insulation deterioration between scheduled
  checks gets detected
• ? Monitoring under actual load temperature
  conditions

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METHODOLOGY

• Signal Acquisition

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METHODOLOGY(contd..)
For small ?, cos d 1, s9 sin d tan d
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ERROR ANALYSIS

• Assumption for theoretical analysis
• Error caused by quantization noise,
• Harmonics totally eliminated by LPF
• RMS error in s9
• s 2-Lv(8?/3)
• where L no. of quantization bits
• normalized cutoff frequency ? fc/fs
• For dissipation factor 5 50?10-3 1
  resolution s 50 ?10-6

L 8 12
? 6.14?10-5 1.57 ?10-2
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• IMPLEMENTATION
• Project objective Verification of the technique
• Through,
• Numerical Simulation
• Experimental setups
• For two implementations
• High Sampling rate for fast updates
• Low sampling rate low cost instrumentation for
  low update rate
• (based on aliasing of periodic waveforms)

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IMPLEMENTATION (contd..)

• High sampling rate Numerical simulation
• fs 450 sa/s,? 0.005 - 0.05, ?10-3 (for
  8-bit), ?15.5310-4
• (for 12-bit) (without band pass filter at the
  input)

L bits Filter Freq (Hz) s (simulation) s (theoretical)
8 IIR Butterworth 50 1e-10 to 1e-4 2e-4
8 IIR Chebychev-I 50 1e-7 to 4e-4 2e-4
8 IIR Chebychev-II 50 1e-6 to 3.3e-4 2e-4
12 IIR Butterworth 50 2e-5 to 7e-5 4.9724e-5
12 IIR Chebychev-I 50 8e-7 to 1e-5 4.9724e-5
12 IIR Chebychev-II 50 7e-5 to 1e-4 4.9724e-5
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IMPLEMENTATION (contd..)

• High sampling rate Experimental setups
• Low voltage setup (30 Vpp)
• I/V converter res. V-divider
• Acquisition with 8-bit 2-channel DSO, 5 k record
  length
• LPF 1 k rect. FIR filter
• For D.F. of 1 - 20 ? 10-3,
• Best fit line slope 1.044, offset 1.863 ?
  10-4
• High voltage setup (600 V)
• Cap. divider for V shunt resistor for I
  sensing
• Acquisition with 8-bit 2-channel DSO, 50 k
  record length
• LPF 10 k rect. FIR filter
• For D.F. of 0.05 - 1 ? 10-3
• Best fit line slope 1.051, offset 5.7 ?
  10-4

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IMPLEMENTATION (contd..)

• Low sampling rate
• Sampling with fslt fo aliasing of periodic V and
  I signals with frequency f fo- fs, retaining
  the original phase relationship
• Advantages
• Low cost data acquisition system
• Distributed signal acquisition units can transmit
  data over a serial link to central unit for
  processing

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IMPLEMENTATION (contd..)

• Low sampling rate Numerical simulation
• fs 45 sa/s, ? 0.005 - 0.05, ?10-4 (for
  8-bit), ?2.4810-4
• (for 12-bit) (without band pass filter at
  the input)

L bits Filter Freq (Hz) s (simulation) s (theoretical)
8 IIR Butterworth 50 5e-3 to 49e-3 0.6e-4
8 IIR Chebychev-I 50 1e-4 to 49e-3 6e-5
8 IIR Chebychev-II 50 9e-5 to 1e-4 1e-4
12 IIR Butterworth 50 1e-5 to 4e-5 2e-5
12 IIR Chebychev-I 50 8e-7 to 1e-5 1e-5
12 IIR Chebychev-II 50 8e-7 to 1e-5 1e-5
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IMPLEMENTATION (contd..)

• Low sampling rate Signal acquisition card

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IMPLEMENTATION (contd..)

• Low sampling rate Experimental setup

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EFFECT OF FREQUENCY VARIATION

• High sampling rate Numerical simulation
• fs 450 sa/s,? 0.005 - 0.05, L12bit,
  ?15.5310-3
• (without band pass filter at the input)

Filter Freq (Hz) s (theoretical) s (simulation)
IIR Chebychev-I 48 5e-5 6e-6 to 5e-4
IIR Chebychev-I 50 5e-5 6e-5 to 1e-4
IIR Chebychev-I 52 5e-5 5.8e-5 to 6.1e-5
IIR Chebychev-II 48 5e-5 3e-5 to 5e-5
IIR Chebychev-II 50 5e-5 7e-5 to 1e-4
IIR Chebychev-II 52 5e-5 5e-4 to 5e-2
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EFFECT OF FREQUENCY VARIATION (contd..)

• Low sampling rate Numerical simulation
• fs 45 sa/s, ? 0.005 - 0.05, ?10-5,L
  12-bit
• (without band pass filter at the input)

Filter Freq (Hz) s (theoretical) s (simulation)
IIR Chebychev-I 48 1e-5 4e-6 to 9e-4
IIR Chebychev-I 50 1e-5 9e-5 to 1e-4
IIR Chebychev-I 52 1e-5 3e-5 to 5e-5
IIR Chebychev-II 48 5e-5 3e-5 to 8e-5
IIR Chebychev-II 50 5e-5 9e-5 to 1e-4
IIR Chebychev-II 52 5e-5 2e-5 to 5e-5
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• EFFECT OF HARMONICS
• THD in power line is around 5

• Harmonics filtering through
• Band pass filter (BPF) (Using IIR Chebychev-I)

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EFFECT OF HARMONICS (contd..)

• High sampling rate Numerical simulation
• fs 450 sa/s, ? 0.005 - 0.05, L12bit,
  ?1510-3, s 5e-5

Freq With BPF s Without BPF s
48 1e-4 to 6e-5 5e-5 to 6e-5
50 1e-4 to 9e-5 9e-3 to 9e-5

• Low sampling rate Numerical simulation
• fs 45 sa/s, ? 0.005 - 0.05, L 12-bit,
  ?10-5, s 1e-5

Freq With BPF s Without BPF s
48 1e-4 to 6e-5 5e-5 to 6e-5
50 1e-4 to 9e-5 9e-3 to 9e-5
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SUMMARY AND CONCLUSIONS

• Direct calculation algorithm for dissipation
  factor m/s verified for 0.005 - 0.05 range with
  resolution 1 (i.e.5?10-5)
• Implementation using high and low sampling rates
• IIR Chebychev filters for m/s insensitivity to
  power line drift
• Band pass filter for attenuating harmonics of
  power line freq.
• High sampling rate implementation
• For detecting incipient faults during
  tests/charging of HV equipment
• Instrumentation for m/s with high update rate
  (10 s)
• DSP with two 12-bit simultaneous sampling
  ADCs
• Low sampling rate implementation
• For monitoring of HV equipment under normal
  aging process
• Instrumentation for m/s with low update rate
  (10 min.)
• signal acquisition h/w with serial data link
  to central unit for pro.