In this paper, a method to improve the protection of a four-core power cable of a salt-producing floating platform equipped with an automatic breaker with an independent tripping mechanism is suggested. The use of this automatic breaker in combination with a suggested protection device ensures reliable protection of not only the power cables of the platform against all faults but also the personnel of the platform and animals on the reservoir banks against electric shock in the event of a single-phase ground fault in reservoir water. This would be possible due to a voltage sensor made in the form of a metal ring on the power cable and a relay; one terminal of the relay winding is connected to the voltage sensor by a single-core control cable, and the other to the neutral of a power source on the platform. The typically open contacts of this relay are connected to an electric circuit which includes a power source and a coil for an independent tripping mechanism of the automatic breaker. This design ensures reliable operation of the suggested protection device in the event of a single-phase ground fault in the power cable of the platform when underwater cable insulation is damaged.

Electrical energy in urban and industrial power supply networks is mainly transmitted through 6–10-kV cable networks with an isolated neutral, where most lines are made as bunches of cables. Up to 75–90% of electrical faults in these cable networks belong to single-phase ground faults (SGFs), which can cause more severe accidents accompanied by significant economic damage. Widely known simple and directional protections against SGFs are relatively selective and, hence, often incapable of properly responding to SGFs in a network with such lines and detecting a cable with SGFs in the bunch of a damaged line. These disadvantages can be eliminated by using new, simple, and inexpensive, absolutely selective protections capable of detecting a cable with SGFs in a damaged line. We suggest the techniques and devices based on zero-sequence current transformers and ring measuring converters for building up such protection systems. The methods for calculating zero-sequence currents in cables of a bunched cable line, depending on the SGF point and the currents in the responding elements, are developed, as well as a procedure for determining a damaged cable and methods for estimating the responding element thresholds and the length of the protection dead zone.

An IoT-based technique is suggested for detecting single-phase earth faults (SEFs) in 6–35 kV cable networks with an isolated neutral. Unlike existing methods based on measuring zero-sequence currents with traditional current transformers, the suggested technique uses a passive magnetically controlled contact (reed switch) placed in the magnetic field of a cable. This enables recording fault currents of 0.5–2.0 A without external power supply and ensures galvanic isolation. The novelty of this technique is the combination of a reed switch current sensor with an IoT platform: instantaneous values of current are measured by the duration of the closed state of the contacts, then the data are transmitted via a radio channel (LoRa 433 MHz, LoRaWAN, or NB-IoT) to a cloud-based SCADA/EMS system for remote monitoring. The amplitude of the current is calculated from the pickup and resetting currents, as well as the duration of the closed state of the contacts; no high-frequency ADC is required. During experimental tests of a prototype with a KEM-5 reed switch and a TZL-10 current transformer, the difference between the calculated and actual protection operation current was no more than 10–5%. Oscillograms confirmed the correct operation of the device when starting, under load, and during an artificial SEF with a current of 1.6 A. The device response time is a fraction of the industrial frequency period, which significantly reduces the emergency mode duration. The suggested system enables decreasing the system average interruption duration index (SAIDI) and the system average interruption frequency index (SAIFI) by selectively disconnecting a damaged section and preventing cascading faults. The use of two independent channels (current transformer and reed switch) increases the reliability of SEF detection and reduces the risk of false operation. Thus, the developed IoT-based technique improves the reliability, safety, and cost-effectiveness of cable network operation.

The growing number of electricity consumers and unstable generation by renewable energy sources (RESs) decrease the efficiency of traditional techniques for modeling large power systems. The diakoptics method is based on structuring a system into subsystems and enables reducing the amount of computation by 2.9 times. However, its classical implementations require successive (iterative) expansion of a scheme, which increases computational time for scaling. This method decomposes a complex system into interacting subsystems with different generation and load characteristics. Generalized parameters are independently calculated for each subsystem and then integrated into the total solution. This significantly reduces the amount of computation, simplifies simulation, optimizes control with allowance for local characteristics, and analyzes intersystem connections to minimize losses and improve stability. This paper suggests not just another Kron calculation but a modification of the diakoptics method, which enables avoiding multiple step-by-step redesigns of a grid by generating generalized parameters based on the complete graph of a system, which significantly reduces computational costs when analyzing large power systems. The method simultaneously considers the entire grid topology. This eliminates successive iterations: if a classical approach requires 13 iterations for a network with 11 nodes and 21 branches, the suggested method performs computation in a single computational cycle. The results show high computational efficiency and practical applicability of the method for large power systems. The suggested approach opens up possibilities for reliability analysis, including redundancy assessment and identification of vulnerable elements, which contributes to an increase in the power system stability under conditions of RES integration.

Бұл жұмыста релелік қорғаныста қолданылатын оқшауланған бейтарап электр желілеріндегі жерге тұйықталу токтарын анықтаудың эксперименттік әдістері қарастырылады. Жерге тұйықталу токтарын анықтаудың дәлдігін арттыруға бағытталған әртүрлі тәсілдерге назар аударылады, бұл электр қондырғыларының қауіпсіз жұмыс істеуін қамтамасыз ету үшін өте маңызды. Параметрлерді бағалау, сондай-ақ олардың артықшылықтары мен шектеулерін талдау үшін желінің жұмыс кернеуін қолданатын әдістерге ерекше назар аударылады. Қолданыстағы әдістерге шолу желіде жасанды асимметрияны құруға негізделген дәстүрлі әдістер әрқашан жеткілікті дәлдікті қамтамасыз етпейтінін анықтады. Сонымен қатар, фазалардың бірін жерге қосымша резистор арқылы жабу әдісі қарастырылады. Бұл тәсіл желінің қорғаныс құрылғыларының жалған дабылдарын болдырмайды және сонымен бірге Жерге қатысты фазалық сыйымдылықты есептеу кезінде ескерілмейтін көптеген желі параметрлерін ескереді. Бұл әдісті релелік қорғаныста қолдану үшін ерекше тартымды етеді. Жерге тұйықталу токтарын анықтау саласындағы әдістер мен бағыттарға жасалған бұл шолу фазаны жерге тұйықтау үшін қосымша резисторды қолдану ең тиімді шешімдердің бірі болып табылады деген қорытынды жасауға мүмкіндік береді. Бұл әдіс токтың сыйымдылық компонентін өтеу құрылғыларының жұмысын ескереді және осылайша жерге тұйықталу токтарын анықтаудың дәл әдісін ұсынады. Кілтті сөздер: жерге тұйықталу тогы, эксперименттік әдістер, оқшауланған бейтарап желі, релелік қорғаныс, токтарды анықтау дәлдігі