Transients in collection grids of large offshore wind parks

Liljestrand, Lars; Sannino, A.; Thorburn, Stefan

doi:10.1002/we.233

Cited by 44 publications

(21 citation statements)

References 10 publications

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“…Due to the finite propagation of the wave along the feeder, each transformer in the feeder receives the voltage wave at a different time, as shown in the magnified timescale in Figure 10b. The surge propagation speed for a cross-linked XLPE cable is 172 m/µs [11]. The distance between two WTTs is 0.7 km, and the time delay for the surge hitting two WTTs in a feeder is 4.1 µs, which is almost close to the simulation result 4.5 µs as shown in the right figure of Figure 10b.…”

Section: Energizing One Feeder With Different Number Of Connected Feesupporting

confidence: 78%

“…Because the switching transient operation time is very short, it is too fast for a WTG to change its state. Relevant researches [11,16] reported that a WTG model can be neglected or simply represented by a constant resistance. Therefore, in this paper the detailed WTG model is not considered, which is represented simply by an auxiliary inductance.…”

Section: Modeling Of Main Components and Entire System Of Offshore Wimentioning

confidence: 99%

“…Since the switching duration time is short, about from tens of microseconds to a few milliseconds, it was stated in [11,16] that the operation mode of WTTs had no effects on switching transient overvoltages, thus WTGs are modeled as large resistance connected to the LV side of WTTs. The authors of [28] reported that WTGs are commonly modeled as a constant impedance in low frequency transients.…”

Section: Energization With Different Load Typesmentioning

confidence: 99%

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Modeling and Mitigation for High Frequency Switching Transients Due to Energization in Offshore Wind Farms

2016

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This paper presents a comprehensive investigation on high frequency (HF) switching transients due to energization of vacuum circuit breakers (VCBs) in offshore wind farms (OWFs). This research not only concerns the modeling of main components in collector grids of an OWF for transient analysis (including VCBs, wind turbine transformers (WTTs), submarine cables), but also compares the effectiveness between several mainstream switching overvoltage (SOV) protection methods and a new mitigation method called smart choke. In order to accurately reproduce such HF switching transients considering the current chopping, dielectric strength (DS) recovery capability and HF quenching capability of VCBs, three models are developed, i.e., a user-defined VCB model, a HF transformer terminal model and a three-core (TC) frequency dependent model of submarine cables, which are validated through simulations and compared with measurements. Based on the above models and a real OWF configuration, a simulation model is built and several typical switching transient cases are investigated to analyze the switching transient process and phenomena. Subsequently, according to the characteristics of overvoltages, appropriate parameters of SOV mitigation methods are determined to improve their effectiveness. Simulation results indicate that the user-defined VCB model can satisfactorily simulate prestrikes and the proposed component models display HF characteristics, which are consistent with onsite measurement behaviors. Moreover, the employed protection methods can suppress induced SOVs, which have a steep front, a high oscillation frequency and a high amplitude, among which the smart choke presents a preferable HF damping effect.

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Section: Energizing One Feeder With Different Number Of Connected Feesupporting

confidence: 78%

Section: Modeling Of Main Components and Entire System Of Offshore Wimentioning

confidence: 99%

Section: Energization With Different Load Typesmentioning

confidence: 99%

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Modeling and Mitigation for High Frequency Switching Transients Due to Energization in Offshore Wind Farms

2016

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“…It was found that the simulation results can be improved greatly if an appropriate VCB model was included in PSCAD, whereas little improvement was found in DigSILENT. Based on the above discoveries, the authors of [9][10][11][12][13] used a PSCAD/EMTDC simulation to calculate TOVs when VCBs were operated in different configurations, and the results showed that TOVs were affected by many factors, such as the operating scenarios of OWFs, the transformer locations, the cable length, and the wave propagations in the cables.…”

Section: Introductionmentioning

confidence: 99%

Analysis of Switching Transients during Energization in Large Offshore Wind Farms

et al. 2018

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Abstract:In order to study switching transients in an offshore wind farm (OWF) collector system, we employ modeling methods of the main components in OWFs, including vacuum circuit breakers (VCBs), submarine cables, and wind turbine transformers (WTTs). In particular, a high frequency (HF) VCB model that reflects the prestrike characteristics of VCBs was developed. Moreover, a simplified experimental system of an OWF electric collection system was set up to verify the developed models, and a typical OWF medium voltage (MV) cable collection system was built in PSCAD/EMTDC based on the developed models. Finally, we investigated the influences of both the initial closing phase angle of VCBs and typical system operation scenarios on the amplitude and steepness of transient overvoltages (TOVs) at the high-voltage side of WTTs.

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“…It has been shown in [3,4], that insufficient representation of the radial circuit breaker in the simulation tool is the main contributor to discrepancies between measurement and simulation results for radial energisation in OWFs. The vacuum circuit breaker (VCB) is the preferred choice as the radial circuit breaker in OWFs due to its low maintenance requirement and long operation life [5,6]. Due to the dielectric properties of vacuum, a number of so-called prestrikes are almost inevitable during the closing operation.…”

Section: Introductionmentioning

confidence: 99%

Transient Studies in Large Offshore Wind Farms Employing Detailed Circuit Breaker Representation

2012

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Switching overvoltages (SOV) are considered a possible source of component failures experienced in existing offshore wind farms (OWFs). The inclusion of sufficiently accurate and validated models of the main electrical components in the OWF in the simulation tool is therefore an important issue in order to ensure reliable switching operations. Transient measurement results in an OWF are compared with simulation results in PSCAD EMTDC and DigSILENT Power Factory. A user-defined model of the vacuum circuit breaker (VCB) is included in both tools, capable of simulating multiple prestrikes during the closing operation. An analysis of the switching transients that might occur in OWFs will be made on the basis of the validated model, and the importance of the inclusion of a sufficiently accurate representation of the VCB in the simulation tool will be described. The inclusion of the VCB model in PSCAD greatly improves the simulation results, whereas little improvement is found in DigSILENT. Based on the transient study it is found that the simulated SOV can be up to 60% higher at the sending end when using the detailed VCB representation compared to the built-in switch, which emphasises the need for accurate representation of the VCB for energisation studies.

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Transients in collection grids of large offshore wind parks

Abstract: In this paper, transients that can occur in collection grids

Cited by 44 publications

References 10 publications

Modeling and Mitigation for High Frequency Switching Transients Due to Energization in Offshore Wind Farms

Modeling and Mitigation for High Frequency Switching Transients Due to Energization in Offshore Wind Farms

Analysis of Switching Transients during Energization in Large Offshore Wind Farms

Transient Studies in Large Offshore Wind Farms Employing Detailed Circuit Breaker Representation

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