Problems of protection during the massive penetration of renewable energy sources in power systems

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Problems of protection during the massive penetration of renewable energy sources in power systems

IEraliyev Abdinabi Khakimovich - Senior Lecturer;

2Tuychiyev Zafarjon Zokirovich - Assistant;

3Eraliyev Khojiakbar Abdinabi ugli - Assistant,

4Ne 'matov Shohruh Ma 'murzhon ugli - Student,

Direction: electric power industry, faculty of energy, Fergana polytechnic institute, Fergana, republic of Uzbekistan

Among the various sources of alternative energy, wind and solar energy are two prominent and promising alternatives to meet the future electricity needs of mankind. As a rule, these sources are integrated into distribution networks to ensure local consumers. If the power generated by these sources is large, then they are either integrated at the distribution level, or can operate in island mode, if possible. Adaptive retransmission and non-adaptive retransmission schemes are discussed in the literature to protect electrical networks that experience dynamic fault currents and frequently changing network topologies.

Keywords: distribution systems, distance protection, asynchronous generator with double feed, micro grid, protection, renewable energy source.

ПРОБЛЕМЫ ЗАЩИТЫ ПРИ МАССИВНОЙ ПЕНЕТРАЦИИ ВОЗОБНОВЛЯЕМЫХ ИСТОЧНИКОВ ЭНЕРГИИ В ЭНЕРГЕТИЧЕСКИХ СИСТЕМАХ

1Эралиев Абдинаби Хакимович - старший преподаватель;

2Туйчиев Зафар Зокирович - ассистент;

3Эралиев Хожиакбар Абдинаби угли - ассистент,

4Неъматов Шохрух Маъмуржон угли - студент,

Среди различных источников альтернативной энергии ветровая и солнечная энергия являются двумя видными и многообещающими альтернативами для удовлетворения будущих потребностей человечества в электроэнергии. Как правило, эти источники интегрированы в распределительные сети для обеспечения местных потребителей. Если мощность, генерируемая этими источниками, велика, то они либо интегрируются на уровне распределения, либо могут работать в островном режиме, если это возможно. Схемы адаптивной повторной передачи и неадаптивной повторной передачи обсуждаются в литературе для защиты электрических сетей, которые испытывают динамические токи повреждения и часто меняющиеся топологии сети. Ключевые слова: распределительные системы, дистанционная защита, асинхронный генератор с двойной подачей, микросетка, защита, возобновляемый источник энергии.

The development of new protection schemes for RES-related power supply systems is a new area. These schemes can be broadly classified as philosophies of adaptive protection and nonadaptive protection. Relay settings must be changed in accordance with the changing level of failure in power systems. All relays, switching devices and control centers must be connected via a reliable bidirectional communication protocol to implement adaptive protection schemes. In nonadaptive protection circuits, the short-circuit current contribution from RES is minimized or blocked by the placement of external devices on the power supply during fault periods [3], [4]. Thus, it is not necessary to change the relay setting when the fault levels in the power supply change due to the intermittent operation of the connected RES. High penetration of the RES can create problems of insufficient or excessive coverage of the overcurrent relay, and can also affect the setting of the range of long-distance relays on transmission lines upstream and lead to improper coordination of the operation of remote relays. The future power system requires modified protection schemes. This requirement will be essential in the case of using photovoltaic renewable energy sources based on an inverter. The short-circuit currents of these resources are extremely small, and protective devices may not recognize the normal load and the failure state due to the thin gap between them [5]. In the future, it is necessary to develop new protection circuits that are suitable for a weak short-circuit current source. In particular, the development of protection schemes for autonomous networks/islands is a new area of research in energy systems. These power systems have either alternating current or pure direct current in nature, where protection circuits require additional consideration. In this review article, the advantages and disadvantages of various existing protection schemes with the integration of renewable energy sources in power systems are discussed. The possibility of implementing these protection schemes for futuristic RES with high penetration into power systems is also discussed. The content of this review article is presented as follows, protection issues in RES-related distribution systems are presented in Section II, and protection issues in RES-related transmission systems are presented in Section III, and micro-network protection schemes are presented in Section IV. The conclusion and future scope of research in the field of renewable energy systems is also presented at the end of this article [3]. alternative energy solar

Distribution systems are primarily protected by current sensors such as overcurrent relays (OC), master keys and fuses. These devices monitor the current flowing through the protected element and generate a trip signal to the circuit breaker if the leakage current exceeds a predetermined value. The protection philosophy of distribution systems has been developed on the basis of the assumption that they are radial in nature, and the flow of energy is always unidirectional from source to consumer [2].

Fig. 1. RES integration into existing network

The contribution of damage level from synchronous RES (small hydropower plants) is in the range from 5 to 6 times the rated current. In addition, photovoltaic RES based on an inverter has a weak current contribution of damage in the range from 1.1 to 2 times the rated current. In this case, the existing overcurrent relay cannot detect a weak fault current. In the last section of this review article, the authors discuss new protection schemes based on voltage and current, which can effectively provide protection for inverter-based photovoltaic systems [3].

Dazzle protection. As discussed above in figure 1, the short-circuit current measured by R1 will be less than without RES. This reduction in short-circuit current will cause the R1 relay to not work, and is called a blinding relay operation [3].

False blackout or sympathetic blackout. The integration of large-scale renewable energy sources into distribution systems leads to the bi-directional transfer of short-circuit current to most feeders lines. A non-directional overcurrent relay may not provide the necessary protection for these networks during supply from the RES. As shown in figure 2, in the event of a malfunction, relay R2 may switch off in the opposite direction due to the direct operation of relay R1.

Fig. 2. Sympathetic tripping of relay R2 due to RES in feed

Fig. 3. Emerging problems due to RES connection

These types of alarms are known as false alarms. In large interconnected distribution systems, several relays may experience failure levels exceeding their trip value and may turn off to the desired main/backup relay, which leads to the isolation of most of the network. These types of false positives are known as sympathetic positives.

Emerging problems. As shown in fig. 3, if the short-circuit current level measured by R2 is sufficient to turn it off, this will result in the isolated operation of the RES with its local connected load. Power imbalances in an isolated network can lead to instability of the island network.

Loss of coordination. False/sympathetic/blind relay operation from downstream to upward feeders leads to successively false relay operation. This type of fake relay is cascaded in a manner known as loss of coordination.

Problems with automatic re-activation As shown in figure 4, when the fault is partially cleared from the reclosing bus, it still supplies the RES. The injected short-circuit current RES can induce an arc through a recloser and can transform a temporary fault into a permanent fault.

Fig. 4. Auto recloser problems with RES integration

Protection schemes for a renewable integrated power grid are an important emerging area of energy research. The highly volatile and intermittent nature of the renewable results in various network topologies leads to a change in failure levels. Relays that are set to a fixed fault level for a predefined network topology will experience different fault levels. This will lead to a loss in the coordinated protection of the relay [6-11].

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