DIY 1000 volt power supply + circuit

Which electrical personnel is assigned group 2 in electrical safety?

Electrical safety group 2 is assigned to electrical personnel who service electrical installations under the supervision of qualified specialists. Attention! Workers with the second electrical safety access group do not have the right to connect or disconnect electrical installations.

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Differences between installations with voltages not exceeding 1000 V

Electrical installations and electrical networks, the voltage of which does not exceed 1000 Volts, have a solidly grounded neutral. In all other types of installations, an insulated neutral is required. That is, the transformer used with a voltage of less than 1000 Volts is grounded by an electrical connection. As a result, single-phase consumers receive the same electrical power even with an asymmetric load. If the installation is purchased for domestic needs, then the standard value for it is 220 Volts.

On the other hand, a solidly grounded neutral will increase the current when a short circuit to ground occurs. As a result, a special automatic protection system is triggered. Accordingly, all equipment with this value must have maximum current protection.

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3. Voltages up to 1000 V and current systems

3.1. In accordance with GOST 21128-83 “Power supply systems, networks, sources, converters and receivers of electrical energy. Rated voltages up to 1000 V and permissible deviations,” power sources and electrical receivers with voltages up to 1000 V AC have rated voltages according to table. 3-1

Table 3-1

In addition to the voltages indicated in table. 3-1 it is allowed to use rated AC voltages of 24 V single-phase current 50 Hz (sources, converters, electrical receivers);

133 V (converters), 127 V (power receivers) and 36 V (sources, converters, power receivers) 50 Hz for previously developed equipment.

3.2. Voltages of power electrical networks up to 1000 V are determined by the voltage values ​​​​accepted for power electrical receivers, namely:

3.2.1. Three-phase alternating current system 660 V with an insulated neutral for powering three-phase and single-phase electrical receivers with a voltage of 660 V and a three-phase alternating current system 660/380 V with a solidly grounded neutral for powering three-phase and single-phase electrical receivers with a linear voltage of 660 V and single-phase electrical receivers with a phase voltage of 380 V. Highest power three-phase and single-phase electrical receivers powered from this system, as a rule, should not exceed the value allowing the use of contactors for a current of 630 A.

3.2.2. A three-phase alternating current system 380 V with an insulated neutral for powering three-phase and single-phase electrical receivers with a voltage of 380 V and a three-phase alternating current system 380/220 V with a solidly grounded neutral for powering three-phase and single-phase electrical receivers with a linear voltage of 380 V and single-phase electrical receivers with a phase voltage of 220 V. Highest power three-phase and single-phase electrical receivers powered from this system, as a rule, should not exceed the value allowing the use of contactors with a current of 630 A.

3.3. Advantages of 660 V voltage (taking into account the increased power of individual electrical receivers and the overall power of enterprises):

saving non-ferrous metal;

reduction of electricity losses;

transferring more expensive electric motors of 6 kV and 3 kV of average power to a voltage of 660 V with their higher efficiency, eliminating intermediate voltages of 6 kV and 3 kV at a voltage of 10 kV, reducing the cost of starting equipment;

convenience when carrying out electrical installation work (cutting conductors of a smaller cross-section in the input couplings of electric motors, devices, etc.). Technical circular of VNIPI TPEP No. 356-87 dated February 16, 1987 “Use of 660 V voltage for electrical installations of industrial enterprises” (IS No. 5, 1987).

3.4. Disadvantages of 660 V voltage:

impossibility of combining power supply to power and lighting electrical receivers. To power lighting electrical receivers, it is necessary to install separate transformers with a primary voltage of 6, 10 kV or 660 V;

the need for voltage measuring circuits to additionally install voltage transformers with a secondary voltage of 100 V;

production of individual mechanisms with only 380 V electrical receivers;

Currently, not all of the required range of devices are manufactured for 660 V;

impossibility of using 660 V voltage for control circuits, see clause 3.12;

increased danger.

3.5. Advantages of 380/220 V voltage:

possibility of joint power supply of power and lighting electrical receivers;

relatively low voltage (220 V) between ground and conductor.

3.6. The choice of voltage for a power network of 660 V or 380 V is decided by a technical and economic calculation, taking into account the technological features of production, the specific load per 1 m2 of workshop area, the power of the main electrical receivers and their efficiency, losses in transformers, and the availability of the required electrical equipment.

3.7. GOST 21128-83 provides a voltage of 500 V. For reconstructed or expanded existing enterprises with a voltage of 500 V, the choice of voltage should be carried out in each case, taking into account specific conditions.

3.8. Issues of power supply to electrical receivers with voltages above 1000 V are considered when solving the high-voltage network of an enterprise.

3.9. In accordance with PUE 1.7.95, power supply to portable electrical receivers or electrical receivers installed on portable mechanisms must be supplied from a network with a voltage not exceeding 380/220 V.

3.10. In accordance with PUE 1.7.44, when separating or step-down transformers are used as a protective measure, the secondary voltage of separating transformers should be no more than 380 V, and of step-down transformers no more than 42 V.

3.11. Under particularly unfavorable conditions, namely, when the danger of electric shock is aggravated by crowded conditions in the place of work, inconvenient position of the worker, contact with large metal, well-grounded surfaces (for example, when working in boilers), a voltage of not above 12 V.

Power supply of portable electrical receivers with reduced voltage, as a rule, should be provided from permanently installed transformers, to the distribution network of which the electrical receivers are connected using connectors.

3.12. In accordance with PUE 3.4.2, the voltage of the secondary circuits should be no higher than 500 V. In some cases, no higher than 1 kV.

3.13. In the control circuits of electrical receivers it is allowed to use the following voltage:

in unbranched control circuits of single electrical receivers - the same voltage as in the main circuits of the electrical receiver, but not higher than 660 V AC;

in control and automation circuits of groups of electrical receivers, as well as in branched control circuits of single electrical receivers - a voltage of 220 V between the ground and the conductor.

3.14. The location of power supplies, circuits, and design of networks, as well as cross-sections of network conductors must be selected so that, under normal operating conditions, deviations of the voltage at the terminals of power electrical receivers from their rated voltage do not exceed the values ​​​​specified in the relevant standards (electric motors, electric furnaces, etc.) .d.), and voltage fluctuations in work lighting lamps did not exceed the values ​​allowed by GOST 13109-67.

The need to ground installations up to 1000

The main danger of installations up to 1000 Volts is the possibility of electric shock to a person who touches ungrounded equipment. As a result of such a touch to the ungrounded body of the electrical installation, current will pass through the person, which is dangerous to life and health. Only grounding will allow the current to go into the ground if a breakdown occurs in the electrical network up to 1000 Volts. Therefore, all work on the installation of electrical installations must be carried out in strict accordance with the norms and requirements of SNiP and PUE.

Where are electrical installations up to 1000 Volts used?

There are quite a large number of areas where solidly grounded electrical installations with a rated voltage not exceeding 1000 Volts are used. Basically, they are all divided into three main groups:

• stationary installations;
• mobile units;
• portable installations.

If mobile and portable electrical installations are the result of factory assembly and include everything necessary for work, then for the installation of stationary objects it is necessary to attract specialists from specialized companies.

Research order:

1. Specialists come to the site and inspect the facility. If necessary, an on-site laboratory is arranged.
2. They check the technical documentation, get acquainted with reports on past tests (if they were carried out).
3. Visually assess the condition of electrical installations, power cables, automatic shutdown devices, distribution lines. Identified deficiencies are immediately eliminated.
4. Measure the insulation resistance of conductors, grounding, and protective devices.
5. Based on the research results, a detailed technical report is drawn up. The document is suitable for submission to the customer and supervisory authorities. Prices for testing and measuring electrical equipment are determined according to the price list, depending on the volume and urgency of the work.

Design and operation of bipolar indicators

The operating principle of these devices is based on comparing the potentials when it is connected to the live parts of the device being tested. At this moment, the resistance in the pointer resistors increases or decreases. A small current flowing in the terminals or wires affects the indicator, after which a light or sound signal begins to emit.

The lack of reaction of the indicator means, accordingly, the absence of voltage. If the indicator signal fades smoothly, this indicates the presence of residual energy in the wires.

As a rule, a two-pole indicator consists of two housings made of dielectric materials. Inside them there are elements that detect voltage and provide sound and light indication. To connect the housings, a flexible wire is used, the length of which is 1 meter or more.

At the inputs into the housing, the wire is equipped with shock-absorbing bushings or reinforced insulation. Each housing has an electrode tip, firmly fixed in a fixed place. Its uninsulated part should be no more than 7 mm, with the exception of indicators designed to work with overhead lines, for which this parameter depends on technical conditions.

Sometimes, in the presence of alternating current, capacitance may form in the metal parts of the indicator in relation to ground or other phases of electrical equipment. In this case, it is quite enough for the indicator light to start glowing when only one probe touches the phase. This phenomenon is eliminated by a shunt resistor, the resistance of which is the same as the additional resistor.