Author 1:
Name & Surname: Sinchuk O. M.
Company: Kryvyi Rih National University (Kryvyi Rih, Ukraine)
Work Position: Head of department
Scientific Degree: Doctor of Engineering Sciences
Contacts: speet@ukr.net

Author 2:
Name & Surname: Likarenko A. G.
Company: Kryvyi Rih National University (Kryvyi Rih, Ukraine)
Work Position: Assistant Professor
Scientific Degree: Candidate of Engineering Sciences

Author 3:
Name & Surname: Petrychenko A. A.
Company: Kryvyi Rih National University (Kryvyi Rih, Ukraine)
Work Position: Postgraduate student

Author 4:
Name & Surname: Shkrabets F. P.
Company: National Mining University (Dnipropetrovsk, Ukraine)
Work Position: Head of department, Professor
Scientific Degree: Doctor of Engineering Sciences

The article sets forward a concept of electrical safety control in iron ore mines operating electrical mains with inserted complex power sources with semiconductor voltage converters. The analytical expressions are given, and it is shown that existing instruments of surface-leakage current protection with dc control power are unable to ensure standard electric safety of mine electric mains. The authors lay foundation for the development and use of surface-leakage current protection devices with ac control power that will eliminate unsettling influence exerted by isolation capacitance of circuit on the protective performance of the devices, and will handle the problem of independent control over isolation resistance and current leakage by setting critical isolation resistance to be much lower that single-phase current leakage and to be consistent with the electrical safety standards. The authors describe the structure of protection instrumentation block — BAZUK 380/220 relay and UZSH 380/220 discrimination protection as well as their protective performance ensuring standard minimum electric safety. Sustained surface leakage current is not higher than 15.2 mA, momentary surface-leakage current is not higher than 81 mA, and the response time of the instrumentation is under 74 ms. The protection selectivity of UZSH 380/220 has been confirmed by the absence of false response in the tests under RF State Standard 22929-78.

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