5. Conclusion

The following results were obtained in this work:

	- the total conductance of mains phase insulation relative to the ground is chosen such additional active conductance, the values were within = 0.2– 0.8, with the error does not exceed 5% when using measuring devices with accuracy class 1.0, and 2.5% using measuring devices with accuracy class 0.5;
	- active conductance in three-phase electrical network with isolated neutral voltages up to and above 1000 V select such active additional conductance gо, so that U<sup>А</sup><sup>∗</sup> = 0.2–0.8, when U<sup>С</sup><sup>∗</sup> = 0.2–0.8, then the error does not exceed 3.5% when using the measuring devices with accuracy class 1.0;
	- capacitive conductance of electrical network phase insulation relative to the ground select such additional active conductance gо, so that U<sup>∗</sup> = 0.2– 0.8, with the change tan δ = 0.6–1.6, then the error does not exceed 5% when using the measuring devices with accuracy class 1.0, and 2.5% when using the measuring devices with accuracy class 0.5.

Special Issues of Ensuring Electrical Safety in Networks with Isolated Neutral Voltage… DOI: http://dx.doi.org/10.5772/intechopen.81384

voltage up to 1000 V in mining enterprises through the development of methods to control the condition of insulation.

A method of measuring the admittance of network with an isolated neutral voltage up to 1000 V is based on the measurement of the modulus of the zero phase-sequence voltage and phase voltage to earth, with an additional conductance where the value of the regulation is made additional conductance in conduction to ensure the equality of the modulus of phase voltage to earth and zero phase-sequence voltage. In ensuring the equality of zero phasesequence voltage and phase voltage to earth connection of additional conductance, it corresponds to the admittance network isolation.

The simulation model of method of measuring the admittance of insulation in the Matlab/Simulink environment was modulated. The developed model allows for the regulation variable resistor to be used to simplify the calculations of the parameters of network isolation. Due to the data received in the regulation of the variable resistor to 2068 Ohms, the true value zero phasesequence voltage and phase A voltage to earth are equal to 140.8 V. Thus, the variable of the admittance y corresponds to 2068 Ohms, which comprises 0.48 mS.

Developing a method of measuring the admittance of insulation networks with an isolated neutral voltage up to 1000 V will provide improved accuracy and speed measurement admittance network isolation. The proposed method is simple, as the instrumentation, single-phase voltage transformers, required for measuring the admittance network isolation is in the service manual enterprise energy management.

5. The experimental data obtained are composed of numerical values of the parameters of the insulation on the excavator EKG-8I of coal mine Ekibastuz, Angrensor LLP. It was established that the insulation resistance is due to active resistance, which characterizes the properties of the dielectric of insulating material used for insulation of live parts of the conductors with respect to ground. Capacitive resistance is higher than active resistance of insulation in networks under 1000 V.

It is found that the RCDs used on excavators by their specifications do not provide effective protection from electric shocks in a short network with voltages under 1000 V as the current of single-phase earth faults in the network under 1000 V on the excavator has less value than the current of the RCD set-up point.

A new method aimed at improving the effectiveness of RCDs in electric network under 1000 V has been developed and is based on setting up the DC into a threephase network with a fixed set-point of protection from any phase-to-earth insulation damage, where the equipment is switched off by residual current device when live-line bare-hand touching of electric equipment occurs. This is due to increases in the phase capacity with respect to earth.

Organizational and technical measures aimed at improving the reliability and level of electrical safety in electrical mining enterprises will help to protect people from electric shocks while also reducing the number of accidents at work.

The work was carried out in accordance with the contract no. 242 of March 17, 2018, at the S. Seifullin Kazakh Agro-Technical University with the Ministry of Education and Science of the Republic of Kazakhstan under the project no.

single-phase earth faults in the three-phase network of the excavator. In order to disable the three-phase network when insulation is damaged, the current of singlephase fault in the network is increased by means of connecting capacitors C1, C2, and C3 between the phases of the electric supply and the ground by load switch QF2. In this case, the current of single-phase circuits in the excavator's three-phase network will be more than the current of the set-up point of RCD, which will activate the RCD. Thus, the switching off is made possible thanks to the load interrupter switch QF1 supplying voltage from the power transformer [40].

Implementation of the developed method to improve the effectiveness of RCDs

in electric networks under 1000 V will ensure the growth of level of electrical safety when using electrical installations and reduce the number of accidents on

1. A method for determining the parameters in three-phase networks with

2. Error analysis of method for determining the parameters of isolation in

satisfactory accuracy required when determining the:

isolated neutral voltage up to 1000 V and above is to measure the modulus of the line voltage and phase voltage with respect to ground and A, and after you connect, an additional active conductivity between the A-phase mains and

three-phase electrical network with isolated neutral showed that it is necessary to select a certain value of additional active conductance, so as to ensure

• the total conductance of mains phase insulation relative to the ground is chosen such additional active conductance, the values were within = 0.2– 0.8, with the error does not exceed 5% when using measuring devices with accuracy class 1.0, and 2.5% using measuring devices with accuracy class

• active conductance in three-phase electrical network with isolated neutral voltages up to and above 1000 V select such active additional conductance gо, so that U<sup>А</sup><sup>∗</sup> = 0.2–0.8, when U<sup>С</sup><sup>∗</sup> = 0.2–0.8, then the error does not exceed 3.5% when using the measuring devices with accuracy class 1.0;

• capacitive conductance of electrical network phase insulation relative to the ground select such additional active conductance gо, so that U<sup>∗</sup> = 0.2– 0.8, with the change tan δ = 0.6–1.6, then the error does not exceed 5% when using the measuring devices with accuracy class 1.0, and 2.5% when

3. The developed methods provide satisfactory accuracy, simplicity, and security in its implementation in the three-phase electrical networks with isolated

4.The chapter presents new evidence-based results that solve the important scientific task of ensuring electrical safety in networks with an isolated neutral

using the measuring devices with accuracy class 0.5.

neutral voltages up to and above 1000 V.

The following results were obtained in this work:

excavators.

5. Conclusion

Industrial Engineering

earth was developed.

0.5;

70

АР05132692 "Development of innovative technologies for increasing the efficiency of power supply for electric receivers with voltages up to 1000 V at mining enterprises."

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