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Method of adaptive current protection against earth faults in 6–10 kV cable networks with an insulated neutral

O.A. Dobryagina, V.V. Tyutikov, T.Yu. Shadrikova, V.A. Shuin

Vestnik IGEU, 2019 issue 5, pp. 31—39

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Abstract in English: 

Background. Simple and reliable zero sequence overcurrent protection in distribution 6–10 kV cable networks with an insulated neutral is most widely used for protection against single phase earth faults. However, protection of this type in many cases does not provide the required sensitivity to internal (inside the protected zone) faults as it must be tuned to the response current from surge transients during external faults through an intermittent arc. It is possible to increase the sensitivity if adaptive current protection is applied. However, the known methods for its implementation are only effective for stable faults through transient resistance but do not provide high dynamic stability of operation in transient conditions in case of arc intermittent earth faults that are the most dangerous for the network. Therefore, an urgent problem to be solved now is improving the principles of adaptive current protection against earth faults.

Materials and methods. To compare the efficiency of the known and proposed principles of adaptive current protection implementation taking into account the complexity of transients during earth faults through an intermittent arc in 6–10 kV cable networks, we used Matlab simulation with the SimPowerSystem and Simulink extension packages. The research into the operation algorithms of adaptive current protection against earth faults was carried out on simulation models of 6–10 kV cable networks with an insulated neutral and with neutral grounding through a high-value resistor.

Results. The studies on the simulation models have shown that the known methods of implementation of adaptive current protection against earth faults based on the use of full zero sequence currents and voltage are ineffective during intermittent arc earth faults. The authors propose a method of adaptive current protection against earth faults in 6–10 kV cable networks with an insulated neutral and with neutral grounding through a high-value resistor that provides a significant increase in dynamic stability of transient operation with arc ground faults and allows using only zero sequence current and voltage components of the operating frequency of 50 Hz as the actuating quantities.

Conclusions. The proposed method of implementing adaptive current protection against earth faults in 6–10 kV cable networks with an insulated neutral and with neutral grounding through a high-value resistor does not only increase the sensitivity of this protection type to earth faults through transient resistence and dynamic stability of operation in transient condiitons in case of arc intermittent earth faults but also broadens the range of its possible applications.

References in English: 

1. Fedoseev, A.M. Releynaya zashchita elektricheskikh sistem [Relay protection of electrical systems]. Moscow: Energiya, 1976. 560 p.

2. Andreev, V.A. Releynaya zashchita i avtomatika sistem elektrosnabzheniya [Relay protection and automation of power supply systems]. Moscow: Vysshaya shkola, 2006. 639 p.

3. Shabad, M.A. Raschety releynoy zashchity i avtomatiki raspredelitel'nykh setey [Calculations of relay protection and automation of distribution networks]. Saint-Petersburg: PEIPK, 2003. 350 p.

4. Shuin, V.A., Gusenkov, A.V. Zashchity ot zamykaniy na zemlyu v elektricheskikh setyakh 6–10 kV [Protection against earth faults in 6–10 kV electrical networks]. Moscow: Energoprogress, Energetik, 2001. 104 p.

5. Shalin, A.I. Zamykaniya na zemlyu v setyakh 6–35 kV. Dostoinstva i nedostatki razlichnykh zashchit [Earth faults in 6–35 kV networks. Advantages and disadvantages of various protections]. Novosti ElektroTekhniki, 2005, vol. 3 (33). Available at: http://www.news.elteh.ru/arh/2005/33/13.php.

6. Likhachev, F.A. Zamykaniya na zemlyu v setyakh s izolirovannoy neytral'yu i s kompensatsiey emkostnykh tokov [Earth faults in networks with isolated neutral and with capacitive currents compensation]. Moscow: Energiya, 1971. 152 p.

7. Dudarev, L.E., Zaporozhchenko, S.I., Luk'yantsev, N.M. Dugovye zamykaniya na zemlyu v kabel'nyh setyakh [Arc earth faults in cable networks]. Elektricheskie stantsii, 1971, no. 8, pp. 64–66.

8. Khalilov, F.Kh., Evdokunin, G.A., Polyakov, V.S. Zashchita setey 6–35 kV ot perenapryazheniy [Overvoltage protection of 6–35 kV networks]. Saint-Petersburg: Energoatomizdat, 2002. 272 p.

9. Al'-Khomidi, M.S., Dobryagina, O.A., Shagurina, E.S., Shadrikova, T.Yu., Shuin, V.A. Otsenka chuvstvitel'nosti tokovykh zashchit ot zamykaniy na zemlyu v kabel'nykh setyakh 6–10 kV [Evaluation of the sensitivity of current protection against earth faults in 6–10 kV cable networks]. Vestnik IGEU, 2016, issue 3, pp. 50–55.

10. Shalin, A.I. Zamykaniya na zemlyu v setyakh 6–35 kV. Napravlennye zashchity. Vliyanie elektricheskoy dugi na napravlennye zashchity [Earth faults in 6–35 kV networks. Directional protection. The effect of an electric arc on directional protection]. Novosti ElektroTekhniki, 2006, no. 1(37). Available at: http://www.news.elteh.ru/arh/2006/37/06.php.

11. Borukhman, V.A. Ob ekspluatatsii selektivnykh zashchit ot zamykaniy na zemlyu v setyakh 6–10 kV i meropriyatiyakh po ikh sovershenstvovaniyu [On the operation of selective protection against earth faults in 6–10 kV networks and measures for their improvement]. Energetik, 2000, no. 1, pp. 20–22.

12. Kashkalov, V.I. Rele zashchity [Protection relays]. Patent RF, no. 2088010, 1997.

13. Sapunkov, M.L., Khudyakov, A.A. Ustroystvo tokovoy zashchity elektricheskikh setey ot odnofaznykh zamykaniy na zemlyu (varianty) [A device of current protection of electric networks from single-phase earth faults (variants)]. Patent RF, no. 2422964, 2011.

Key words in Russian: 
кабельные сети 6–10 кВ с изолированной нейтралью, однофазные замыкания на землю, адаптивная токовая защита от замыканий на землю, динамическая устойчивость функционирования
Key words in English: 
6–10 kV cable networks with an insulated neutral, single-phase earth faults, adaptive current protection against earth faults, dynamic stability of operation
The DOI index: 
10.17588/2072-2672.2019.5.031-039
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