Title: Modeling of Rogowski Coil for Online PD Monitoring in CoveredConductor Overhead Distribution Network
1Modeling of Rogowski Coil for On-line PD
Monitoring in Covered-Conductor Overhead
Distribution Networks
- G. Murtaza HASHMI
- Matti LEHTONEN, and
- A. ELHAFFAR
- Power Systems and High Voltage Engineering
- Helsinki University of Technology (TKK)
- Espoo-FINLAND
2Introduction
- Use of CC lines in MV networks
- Trees fall on CC lines due to heavy storms
- On-line PD measurements to monitor falling trees
on CC lines - Automatic detection can reduce visual inspection
work and improves reliability of the distribution
network
3Motivation
- Faling trees may damage TL components (e.g.
insulators, clamps, ploes), if not removed - PDs produced due to falling trees can damage
insulation and may subsequently induce different
faults - The challenge for on-line PD measurements is to
find the optimal locations for PD sensors - Attenuation is an important parameter in order to
estimate the maximum length of the line that can
be monitored with a PD sensor
4Rogowski coil as PD sensor
- Limitations of conventional PD detectors
- Influence of background noise
- Intrusive
- Limit in the detection frequency range
- Rogowski coil
- Non-intrusive
- Easy to install
- High detection frequency range
- Converted into a wireless one in next stage
5Experimental Set-up
Rogowski coil responses for 5 nC calibrator pulse
at (a) point P1, and (b) point P2
6Rogowski coil parameters
Rogowski coil is modeled in ATP as a saturable
current transformer having linear magnetizing
characteristics
7CC line parameters
- The frequency-dependent CC line characteristics
are calculated using theoretical model, and are
used in simulation as resistance, 2 ?/m
characteristic impedance, 350 ? and propagation
velocity, 230 m/?s (average values for MHz range) - The transmission lines are represented using
distributed parameters Clarke model in ATP
8ATP model of measuring system
ATP Draw circuit for the PD monitoring system
5 nC calibrator pulses (measured and simulated)
9ATP simulation results
Rogowski coil response for 5 nC pulse calibrator
charge at point P2 in (a) time domain, and (b)
frequency domain
10ATP simulation results-continued
Rogowski coil response for 5 nC pulse calibrator
charge at point P1 in (a) time domain, and (b)
frequency domain
11Conclusions
- ATP simulations are performed to model the
transient behavior of the Rogowski coil. - The model can be used to estimate the length of
the line at which the PDs due to falling trees
can be detected thus, deciding the number and
positioning of the sensors over a particular
length of the CC line. - The simulation results show that the CC line has
very low attenuation, and the higher amplitude
pulse measured by the Rogowski coil near the
source of PD is due to the effect of its varying
resonance frequencies at different distances. - The Rogowski coil used in this study is not good
for high frequency measurements beyond 5 MHz.
Therefore, a higher bandwidth coil should be used
for real time analysis of PDs produced by falling
trees on the CC lines.
12Future developments
- The proposed model can be used for different
band-width Rogowski coils to observe the PD wave
propagation - It would be more practical and demanding if an
on-line three-phase (instead single-phase) PD
measuring system can be modeled. - The simulated PD wave propogation can be
investigated in an integrated network to analyze
and resolve the real problems faced by the local
utilities
13Thanks