Enhanced method for voltage range controlled OLTC-equipped distribution transformers

Reese, C.; Buchhagen, Christoph; Hofmann, Lutz

doi:10.1109/pesgm.2012.6345416

Cited by 9 publications

(4 citation statements)

References 6 publications

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“…Instead, we consider attacks that degrade the longer-term health of the system. • OLTC transformers are being increasingly adopted in distribution grids, particularly in the context of residential-scale PV systems [24,34]. The OLTC transformer is one of the most important and expensive devices in power systems.…”

Section: Introductionmentioning

confidence: 99%

Botnets Breaking Transformers: Localization of Power Botnet Attacks Against the Distribution Grid

Pepin¹,

Wang²,

Wang³

et al. 2022

Preprint

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Traditional botnet attacks leverage large and distributed numbers of compromised internet-connected devices to target and overwhelm other devices with internet packets. But with increasing consumer adoption of high-wattage internet-facing "smart devices", a new "power botnet" attack emerges, where such devices are used to target and overwhelm power grid devices with unusual load demand. We introduce a specific variant of this attack, the power-botnet weardown-attack, which does not intend to cause blackouts or short-term acute instability, but instead forces expensive mechanical components to activate more frequently, necessitating costly replacements or repairs. Specifically, we target the on-load tap-changer (OLTC) transformer, which involves a mechanical switch that responds to change in load demand. In our analysis and simulations, such power botnets can halve the lifespan of an OLTC, or in the most extreme cases, reduce it to 2.5% of its original lifespan. Notably, these power botnets are composed of devices that are not connected to the internal SCADA systems used to control power grids. This represents a new internet-based cyberattack that targets the power grid in a way that cannot be solved by hardening existing SCADA systems. To help the power system to mitigate these types of botnet attacks, we develop attack-localization strategies. To the best of our knowledge, there is no valid model-based approach for attack localization. So we formulate the problem as a supervised machine learning task to locate the source of power botnet attacks. Within a simulated environment, we generate the training and testing dataset to evaluate several machine learning algorithm based localization methods, including SVM, neural network and decision tree. We show that decision-tree based classification successfully identifies power botnet attacks and locates compromised devices with at least 94% improvement of accuracy over a baseline "most-frequent" classifier. CCS Concepts: • Security and privacy → Hardware attacks and countermeasures; • Computing methodologies → Machine learning; Machine learning algorithms; Classification and regression trees; Supervised learning; • Hardware → Smart grid; Power networks; Switching devices power issues.

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Section: Introductionmentioning

confidence: 99%

Botnets Breaking Transformers: Localization of Power Botnet Attacks Against the Distribution Grid

Pepin¹,

Wang²,

Wang³

et al. 2022

Preprint

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“…On the other hand, given the demand profiles at LV residential network could be significantly different from the demand profiles recorded at the primary substation, the associated technical issues faced by these two network levels would vary. In relation to LV circuits which are typically equipped with off-load tap changers transformer, the use of on-load tap changer (OLTC) transformer is increasingly being considered in the area with high concentration of PV systems [4]. This provides greater flexibility for the network to host higher PV penetrations [5].…”

Section: Introductionmentioning

confidence: 99%

Impact of the photovoltaic system variability on transformer tap changer operations in distribution networks

Gan

Lau

Baharin

et al. 2017

CIRED - Open Access Proceedings Journal

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This study aims to quantify the transformer tap changer operations on distribution networks with large penetration of photovoltaic systems. The influence of solar generation variability on transformer tap changer is investigated by using five different solar variability day types collected in Malaysia with 1 min resolution. The case studies have been performed on a Malaysian representative distribution network. Results show that high solar variability day could increase the transformer's tap changes by 600% as compared to the clear sky day. The transformer's time delay setting plays a vital role in limiting the tap operations.

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“…To extend the 'on load' flexibility in terms of voltage management closer to the LV customers, the adoption of on-load tap changer (OLTC)-fitted distribution transformers is increasingly being considered, particularly in the context of residential-scale PV systems [3]- [7]. However, depending on the control strategy, tap operations can be significant, leading to the wear and tear of the OLTC [3], [4]. Therefore, an adequate OLTC control strategy should be used to ensure voltages are within statutory limits whilst minimizing tap operations so as to reduce the maintenance/overhaul cost incurred by the Distribution Network Operator (DNO).…”

Section: Introductionmentioning

confidence: 99%

“…This method, however, requires some understanding of the impedances of the feeders to approximate suitable setpoints. Similarly, in [3] and [4], an allowable voltage range at the busbar was analyzed and adopted as the control input for the OLTC in order to reduce tap operations. This voltage range was determined by the characteristics of the LV feeders, i.e., number of customers, impedance, PV penetration.…”

Section: Introductionmentioning

confidence: 99%

Voltage Control of PV-Rich LV Networks: OLTC-Fitted Transformer and Capacitor Banks

Long

Ochoa

2016

IEEE Trans. Power Syst.

143

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Due to the increasing adoption of domestic photovoltaic (PV) systems, the use of technologies such as on-load tap changer (OLTC)-fitted transformers, capacitor banks, and remote monitoring are being considered to mitigate voltage issues, particularly in European-style low voltage (LV) networks. Depending on the control strategy, however, the effects on customer voltages and control actions (e.g., tap changes or capacitor switching) can vary significantly. This work presents a framework to assess the performance of different OLTC-based control strategies in terms of voltage compliance with the standard BS EN50160 and the number of control actions. Three control strategies are proposed: constant set-point (CSC), time-based (TBC) and remote monitoring-based (RMC). A week-long Monte Carlo analysis is carried out considering a real UK LV network, three-phase power flows, different PV penetrations and seasonality. Results show that the TBC outperforms the CSC but at the expense of more tap changes. Due to the enhanced visibility, the RMC significantly increases the PV hosting capacity whilst limiting tap operations. Finally, when feeders have contrasting voltage issues, capacitor banks are found to provide additional flexibility and allow higher PV penetrations. These findings are expected to help the industry determining the benefits from OLTC-based solutions in future LV networks. Index Terms--capacitor banks, low voltage distribution network, on-load tap changer, photovoltaic, voltage control.

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Enhanced method for voltage range controlled OLTC-equipped distribution transformers

Cited by 9 publications

References 6 publications

Botnets Breaking Transformers: Localization of Power Botnet Attacks Against the Distribution Grid

Botnets Breaking Transformers: Localization of Power Botnet Attacks Against the Distribution Grid

Impact of the photovoltaic system variability on transformer tap changer operations in distribution networks

Voltage Control of PV-Rich LV Networks: OLTC-Fitted Transformer and Capacitor Banks

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