Surge analysis for lightning strike on overhead lines of wind farm

https://doi.org/10.1016/j.epsr.2021.107066Get rights and content

Highlights

  • The mathematical models for power equipment in wind farm have been developed.

  • The transients under lightning strike on overhead lines in wind farm are obtained.

  • The capacitance between windings of step up transformer plays a key role.

  • The protection area and absorbed energy of surge arrester in wind farm are studied.

Abstract

The overhead line in wind farm is vulnerable to lightning strikes at a high risk. The lightning surge would propagate along the line and damage the equipment in substation. In this work, the mathematical models for transmission tower, overhead lines, power transformer and wind farm substation have been developed in the environment of EMTP, especially the wind turbine converter and step up transformer models. The transients in the case of back flashover and shielding failure are analysed. The influences of radial and cross-shaped connections of wind turbine topology on the wave reflection and refraction have been investigated. The performance of surge arrester, not only the protection area but also the absorbed energy under lightning overvoltage is also computed. The wind farm substation is divided into multi zones and the transient response at different nodes is obtained. It indicates that the characteristics and propagation for surge under lightning strike on overhead line are completely different from direct lightning strike on wind turbine receptor. The capacitance between the high and low voltage side of step up transformer plays a key role in system transients. Compared with back flashover, the overvoltage caused by shielding failure is relatively small; the cross-shaped scheme is preferred and would benefit the lightning protection; the absorbed energy of arresters under a high lightning current is a major consideration.

Introduction

Wind farm installations have increased substantially over past decades to satisfy the growing demand of electricity [1], [2], [3]. Besides enhancing the power supply reliability, the use of wind energy also reduces the fossil fuel hazard and minimizes the operating cost. The wind energy can be either integrated into AC or DC grids. It is estimated that the installation capacity of wind turbines (WTs) would exceed one thousand gigawatts by the year 2020. Wind turbines are tall structures more than tens of meters height and located in regions which might span across mountain ridges or in other areas of elevated ground to obtain good wind condition. The wind turbines are located on open space and exposed to atmospheric thunderstorms at a high risk [4], [5], [6], [7]. Many incidents have been reported worldwide on this issue. As the wind turbine blades are often made of glass fiber reinforced polymer composite materials, some blades are thermally damaged and broken down under the strong effect of heavy electric arc current; the lightning sometimes hits the ground and devastate the underground cable in collector line as well as the control system [8], [9]. The increase in wind farm gives rise to arising damage from lightning storm.

Lightning is a rather stochastic natural phenomenon. The occurrence in wind farm plant is influenced by many factors, like the geographical location, the altitude, and the topographical and orographical effects. The mechanism of lightning strikes rotating wind turbine blade has been extensively investigated; the evolution of upward leader is captured using high-speed CCD camera; the lightning protection space is divided in multi-zones; a blade lightning protection zone for rating the lightning risk is defined [10]. The configuration and number of receptors on the interception effect are analyzed. Moreover, an improved electro-geometric model has been proposed to elucidate the evolution of lightning streamer [11]. Wind turbine blades can produce electric discharges, and ions would be accumulated near the tip of blade receptor. Ions are likely to migrate along the rotating direction and electric field generated by thundercloud. The rotation has different effects on the lightning - attracting ability of wind turbine for short and long gaps.

In the case of lightning strike on wind turbine, the heavy current would pass through the tower, the grounding system and finally dissipate into soil. The entire electromagnetic transient of wind turbine has been studied by means of EMTP, and the transients for many locations inside the wind turbine are computed [12, 13]. The frequency of lightning current generally ranges from 10 kHz to 3 MHz [14]. Mathematically, the receptor and down conductor inside wind turbine blade are divided into a number of segments [15]. Each segment is represented by a RLC π-circuit; the moving contacts and shaft bearing are treated as a set of resistance and capacitance in parallel; the wind turbine tower is a tubular circular truncated cone for analysis. In addition to single blade strike, multi-blade lightning strike is also considered [16]. Several reduced-scale prototypes have been set up in laboratory. Standard lightning impulses are applied to the tip of blade receptor to validate the simulation results [17]. The coupling effect between wind turbine tower and signal cable are discussed and the induced voltage on metal sheath and cable conductor are obtained [18]. The transient jointly depends on the lightning current magnitude and wave shape, the impedance of wind turbine structure and the grounding system. The magnitude of transient overvoltage decreases from the blade tip to the wind turbine body. A small grounding resistance is essential. The off-shore wind generation system, which has a monopile foundation soaked in seawater, is completely different from that of on-shore wind farm.

In practice, most of onshore wind farms are built on remote mountainous terrain to obtain good wind condition. Compared to offshore wind farms, the optimization of large-scale onshore wind farms is more dependent on the surroundings, such as the topography of construction area and the presence of neighbouring residential areas. The wind turbines are electrically connected to power grid through overhead lines. The right-of-way of transmission lines often takes a large area, and the lines as well as transmission towers are also vulnerable to lightning strikes. The structure and topology of wind farm are different from traditional thermal plants. There are various designs of collection systems for wind farm substation, including radial connection, radial-loop connection, and AC star/cluster connection. Meanwhile, a series-parallel connection of turbines with HVDC has been proposed, e.g., DC radial connection, DC series/daisy chain connection, and DC series-parallel connection [19]. In the case of shielding failure or back flashover, the lightning surge would propagate along the overhead line and intrudes into transformers. Subsequently, the surge transfers between primary and secondary windings and into the generator. Part of lightning current would propagate to the substation. The basic lightning impulse insulation level (BIL) of the wind turbine generator is relatively low. The lightning surge also passes through the converter. As a kind of electronic device, it is sensitive and prone to damage under severe lightning condition. Furthermore, the arrangement of wind farm substation is also different from traditional substation. As a consequence, the transient response is changed. The characteristics of lightning surge are completely different from that of blade receptor, little attention has been paid to this aspect so far, and that is the main objective of our work.

Section snippets

Wind farm description

The schematic diagram for the lightning surge into wind farm is illustrated in Fig. 1. When a strong lightning strikes the shield wire or transmission tower, the current would dissipate into ground and cause a potential rise across the insulator string, resulting in the back flashover. On the other hand, the lightning sometimes directly hits the phase conductor, leading to the so-called shielding failure. Then, the surge would travel through the overhead line, step up transformer, power cables

Mathematical model

The wind farm consists of transmission tower, overhead lines, power transformer, wind turbine converter, and double-fed wind induction generator (DFIG). The mathematical models are described as follows.

Simulation model

To elucidate the transient response of wind farm, the 220 kV Huishangang wind farm substation located in Hunan of southern China is considered, and the system configuration is illustrated in Fig. 13. This step-up substation is built to collect all energy generated by the turbines and received through cables. The substation is composed by medium voltage system and high voltage system. Each system consists of the general busbar, circuit breakers, disconnectors, current transformer together with

Lightning surge propagation in wind farm substation

In addition to wind turbine, the lightning surge would also propagate into substation along the line and threaten the safety of power equipment. The transient response under lightning strike is plotted in Fig. 24, and the voltage rises at crucial nodes of wind farm are presented in Table 5.

  • Since the lightning strike point is close to Unit 3, the traveling wave first reaches TR3H and WT3, and then Unit 2 and Unit 4. Due to the close distance, the wave reflection effect is relatively small, and

Conclusions

The conclusions are drawn as follows.

  • The characteristics of surge due to lightning direct strike on overhead line are completely different from that of blade receptor. The influences of lightning current waveform, lightning strike mode and location are discussed. The surge transfer between primary and secondary windings of step-up transformer plays a key role in the system transients; the shorter the front of lightning current, the larger the amplitude of the overvoltage is.

  • As the lightning

CRediT authorship contribution statement

Qiuqin Sun: Methodology, Resources, Funding acquisition, Writing - review & editing. Lei Yang: Investigation, Software, Validation, Writing - original draft. Qian Li: Writing - review & editing. Xiaorong Zhang: Writing - review & editing. Feng Wang: Conceptualization, Formal analysis. She Chen: Data curation. Lipeng Zhong: Writing - review & editing.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

This work is supported by the National Natural Science Foundation of China under Grant 52077068 and 51677061.

References (44)

  • X. Wang et al.

    Comparison of numerical analysis models for shielding failure of transmission lines

    Electr. Power Syst. Res.

    (2013)
  • M. Popov et al.

    Evaluation of surge-transferred overvoltages in distribution transformers

    Electr. Power Syst. Res.

    (2008)
  • F. Rachidi et al.

    A review of current issues in lightning protection of new-generation wind-turbine blades

    IEEE Trans. Ind. Electron.

    (2008)
  • S. Sekioka et al.

    A study on overvoltages in wind farm caused by direct lightning stroke

    IEEE Trans. Power Deliv.

    (2019)
  • A.C. Garolera et al.

    Multiple lightning discharges in wind turbines associated with nearby cloud-to-ground lightning

    IEEE Trans Sustain Energy

    (2015)
  • A.C. Garolera et al.

    Lightning damage to wind turbine blades from wind farms in the U.S

    IEEE Trans. Power Deliv.

    (2016)
  • X. Li et al.

    Lightning transient characteristics of cable power collection system in wind power plants

    IET Renew. Power Gener.

    (2015)
  • Y. Wang et al.

    Influence of blade rotation on the lightning stroke characteristic of a wind turbine

    Wind Energy

    (2019)
  • J. Montanyà et al.

    Lightning discharges produced by wind turbines

    Wind Energy

    (2014)
  • M.A. Abd-Allah et al.

    A novel lightning protection technique of wind turbine components

    J. Eng. 2015

    (2015)
  • Y. Yasuda et al.

    Surge analysis on wind farm when winter lightning strikes

    IEEE Trans. Energy Convers.

    (2008)
  • H. Chen et al.

    Lightning grounding grid model considering both the frequency-dependent behavior and ionization phenomenon

    IEEE Trans Electromagn Compat

    (2019)
  • Cited by (9)

    • A comprehensive lightning surge analysis in offshore wind farm

      2022, Electric Power Systems Research
      Citation Excerpt :

      The WT blade, WT tower as well as grounding system are modeled in the environment of EMTP [4–8]; the overvoltage of key nodes and equipment are analyzed in detail [9]. In practice, considerable WTs are connected to power grid through overhead line (OHL), its right-of-way often takes a large area; the system transients due to direct lightning strike on OHLs have been investigated in [10]. The lightning current may invade from WT to distribution lines via capacitive coupling [10]; it is especially evident in some area of high lightning-to-ground flash density.

    View all citing articles on Scopus
    View full text