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|Title: ||A Study On High Voltage AC Power Transmission Line Electric And Magnetic Field Coupling With Nearby Metallic Pipelines|
|Authors: ||Gupta, Abhishek|
|Advisors: ||Thomas, M Joy|
|Keywords: ||Electromagnetic Interference|
Electric Power Transmission
Power Lines - Coupling
Pipelines - Induced Voltages - Computing
Charge Simulation Method (CSM)
|Submitted Date: ||Aug-2006|
|Abstract: ||In the recent years, there has been a trend to run metallic pipelines carrying petroleum products and high voltage AC power lines parallel to each other in a relatively narrow strip of land. The case of electromagnetic interference between high voltage transmission lines and metallic pipelines has been a topic of major concern since the early 60’s. The main reasons for that are:
• The ever increasing cost of right-of-ways, suitable for power lines and pipelines, along with recent environmental regulations, aiming to protect nature and wildlife, has forced various utilities to share common corridors for both high voltage power lines and pipelines. Therefore, situations where a pipeline is laid at close distance from a transmission line for several
kilometers have become very frequent.
• The rapid increase in energy consumption, which has led to the adoption of higher load and short circuit current levels, thus making the problem more acute.
Due to this sharing of the right-of-way, overhead AC power line ﬁeld may induce voltages on the metallic pipelines running in close vicinity leading to serious adverse effects. This electromagnetic interference is present both during normal operating conditions as well as during faults. The
coupling of the ﬁeld with the pipeline takes place either through the capacitive path or through the inductive or conductive paths.
In the present work, the induced voltages due to capacitive and inductive coupling on metallic pipelines running in close vicinity of high voltage power transmission lines have been computed.The conductor surface ﬁeld gradients calculated for the various phaseconﬁgurations have been presented in the thesis. Also the electric ﬁelds under transmission lines, for both single circuit and double circuit (various phase arrangements) have been analysed. Based on the above results, an optimum conﬁguration giving the lowest ﬁeld under the power line as well as the lowest conductor surface gradient has been arrived at and for this conﬁguration induced voltage on the pipeline has been computed using the Charge Simulation Method (CSM). For comparison, induced voltages on the pipeline have been computed for the various other phase conﬁgurations also. A very interesting
result is that the induced voltage on the pipeline becomes almost negligible at a critical lateral distance from the center of the powerline and beyond which the induced voltage again increases.This critical distance depends on the conductor conﬁguration. Hence it is suggested that the
pipeline be located close to the critical distance so that the induced voltage would be close to zero.
For calculating the induced voltage due to the inductive coupling, electromotive force (EMF),induced along the pipeline due to the magnetic ﬁeld created by the transmission line has been calculated. The potential diﬀerence between the pipeline and the earth, due to the above induced EMFs, is then calculated. As the zones of inﬂuence are generally formed by parallelism,
approaches, crossings as well as removals, the computation involves subdividing the zone into several sections corresponding to these zones. The calculation of voltages is carried out at both the ends of the sections. Each section is represented by an equivalent π electrical network, which
is inﬂuenced by the induced EMF. The induced EMF is calculated during faulted conditions as well as during steady state conditions. Inductive coupling calculations have been carried out for the following cases:
•Perfect parallelism between powerline and pipeline.
•zone of inﬂuences formed by parallelism, approaches, crossings and removals.
It has been observed that when the pipeline is approaching the HV transmission line at an angle, then running parallel for certain distance and ﬁnally deviating away, the induced voltage is maximum at the point of approach or removal of the pipeline from the transmission line corridor.The induced voltage is almost negligible near to the midpoint of the zone of inﬂuence. The proﬁle
of the induced voltage also depend on whether the pipeline is grounded or left open circuited at the extremities of the zone of inﬂuence. Effect of earth resistivity and anti-corrosive coatings
on induced voltage has also been studied. For mitigating the induced voltage on the pipeline,numerous low resistive earthings have been suggested. Results show that signiﬁcant reduction in induced voltage can be achieved as the number of earth points is increased.|
|Appears in Collections:||Electrical Engineering (ee)|
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