Alexandre Piantini University of São Paulo [email protected] Lightning-Induced Voltages on Overhead Power Distribution Lines April 6 rh – 8 th , 2016 Cartagena de Indias, Colombia
Alexandre Piantini
University of São Paulo [email protected]
Lightning-Induced Voltages on Overhead Power Distribution Lines
April 6rh – 8th, 2016 Cartagena de Indias,
Colombia
OUTLINE
Introduction Validation of Coupling Models Characteristics of Lightning-Induced Voltages Protective Measures (shield wires, arresters) Priority Issues in Lightning Research Final Remarks
Lightning:
- equipment damages and failures - damages to customer electronic devices - voltage sags - supply interruptions
Widespread use + growing dependence on the continuous operation of sensitive electronic equipment ! increasing awareness of the importance of mitigating such effects
! to evaluate the lightning overvoltages and the effectivenesses of the protective measures
INTRODUCTION
INTRODUCTION - INDIRECT STROKES
Courtesy: Prof. S. Yokoyama Magnitudes << than those of the surges related to direct strokes, but the
phenomenon is much more frequent à greater no. flashovers (≤ 15 kV).
I = 54 kA; tf = 3.2 µs; b = 0.11; hc = 600 m; h = 10 m; Rg = 200 Ω; ρ = 0 Ωm All parameters referred to the FS system
x
450 m 450 m
70 m
VALIDATION OF COUPLING MODELS
Surge arresters
450 m
(ERM)
Scale model (USP)
The induction mechanism and the problems related to LIV on distrib. lines have been studied for a long time and various
models and codes have been proposed for LIV calculations.
Extended Rusck Model – ERM
SCALE MODEL
Measurement: USP (Scale Model)
I = 70 kA
Top view (urban line)
tf = 2 µs
All parameters referred to the FS system
VALIDATION OF COUPLING MODELS
Calculation: LIOV-EMTP (Nucci et al.)
model
Agrawal et al. (1980) and its equivalent formulations - Rachidi (1993) and
Taylor et al. (1965)
- Magnitude, front time, and propagation velocity of the stroke current
- Distance between line and lightning strike point
- Upward leader / elevated object
- Line configuration (horizontal or vertical, rural or urban)
- Conductors’ heights, presence of a shield wire or neutral conductor
- Observation point
- Position of the stroke channel relative to the line
- Soil resistivity and ground resistance
- Grounding / surge arresters’ spacing
- Surge arrester V/I characteristic
CHARACTERISTICS OF LIVs
Shorter durations in comparison with the overvoltages caused by direct strokes.
Top view (urban line), d = 20m, hb = 5 m Top view (urban line), d = 20m, hb = 15 m
SCALE MODEL
Measurement: USP (Scale Model)
I = 50 kA
tf = 2 µs
All parameters referred to the FS system
Nearby Buildings
PROTECTIVE MEASURES
Increasing CFO
Shield wire
Surge arresters
Direct strokes
Indirect strokes X
MV lines: measures against short interruptions and voltage sags stemmed from lightning:
I = 50 kA; tf = 3 µs; b = 0.3; ρ = 1000 Ω.m
hg = 11 m
10 m
Rg
300 m 300 m 300 m
50 m
SHIELD WIRE – ground resistance
ERM
x
I = 50 kA; tf = 3 µs; b = 0.3; ρ = 1000 Ω.m
hg = 11 m
10 m
Rg
300 m 300 m 300 m
50 m
SHIELD WIRE – ground resistance
x
d = 61 m
Mast
SURGE ARRESTERS
USP
Measured Induced Voltages
x
1:50 scale model
SURGE ARRESTERS - spacing
I = 38 kA; tf = 3.2 µs; b = 0.11; hc = 600 m; h = 10 m; gapless S.A.; ρ = 0 Ωm; Rg = 50 Ω
x
I = 38 kA
70 m
300 m
162 kV
67 kV
125 kV
600 m
x
Despite the existence of reliable models for the analysis of lightning transients, the application of such models for assessing the probability that a particular event detected by a LLS could lead to a power outage is still a challenging issue. LIVs depend on many parameters and are particularly affected by the stroke location and current magnitude and waveshape. It is essential to continue efforts to develop more reliable power equip. models, improve the performance of LLS and ↓ the uncertainties in the estimation of the stroke location and current parameters.
PRIORITY ISSUES IN LIGHTNING RESEARCH
Measurements of lightning current parameters (FS and SS) in different locations; ↑ accuracy in the estimation of lightning locations and current parameters from remote EM field meas.; models for positive lightning flashes; better characterization of lightning transients; more accurate models to represent the behavior of power equipment subject to lightning surges.
PRIORITY RESEARCH TOPICS
LIV on overhead lines depend on many parameters, which may combine in an infinite variety of ways;
validity of models, characs. of LIV and their dependence on important parameters involved in the ind. mechanism;
examples illustrating the mitigating effects of a multi-grounded shield wire and line arresters;
analyses involved simulations using a reliable model and both reduced and full-scale experiments;
priority issues in lightning research.
FINAL REMARKS
MUCHAS GRACIAS POR SU ATENCIÓN!
April 6rh – 8th, 2016 Cartagena de Indias,
Colombia