Purpose
1. Voltage indicators are designed to determine the presence or absence of voltage on the current-carrying parts of electrical installations.
2. General technical requirements for voltage meters are set out in the state standard.
Voltage indicators above 1000V
Principle of operation and design
3. Voltage indicators above 1000 V react to the capacitive current flowing through the indicator when its working part is introduced into the electric field formed by the current-carrying parts of electrical installations that are energized, and the "ground" and grounded structures of electrical installations.
4. Pointers must contain the main parts: working, indicator, insulating, as well as a handle.
5. Working part contains elements that react to the presence of voltage on the controlled current-carrying parts.
The working part may contain a tip electrode for direct contact with controlled current-carrying parts and not contain a tip electrode (non-contact pointers).
indicator part, which can be combined with the working one, contains elements of light or combined (light and sound) indication. Light and sound signals must be reliably recognizable.
The working part may also contain an organ of its own control of serviceability. Control can be carried out by pressing a button or be automatic, by periodically supplying special control signals.
6. The insulating part can be a composite of several links. To connect the links to each other, parts made of metal or insulating material can be used. The use of a telescopic design is allowed, while spontaneous folding should be excluded.
7. The handle can be one piece with the insulating part or be a separate link.
8. The design and weight of the signs must ensure the possibility of working with them by one person.
9. Wiring diagram and the design of the pointer must ensure its operability without grounding the working part of the pointer, including when checking the absence of voltage, carried out from telescopic towers or from wooden and reinforced concrete poles of 6-10 kV overhead lines.
10. The indication voltage of the voltage indicator should not exceed 25% of the rated voltage of the electrical installation.
11. The time of appearance of the first signal after touching the current-carrying part, which is energized, equal to 90% of the rated phase, should not exceed 1.5 s.
12. The working part of the pointer to a certain voltage should not react to the influence of neighboring circuits of the same voltage.
Performance tests
13. During operation, mechanical tests of voltage indicators are not carried out.
14. Electrical tests of voltage indicators consist of testing the insulating part with increased voltage and determining the indication voltage.
For voltage meters with a built-in power source, its condition is monitored and, if necessary, the batteries are recharged or the batteries are replaced.
15. When testing the insulation of the working part, the voltage is applied between the tip electrode and the screw connector or at the border of the working part.
16. When testing the insulating part, voltage is applied between the element of its articulation with the working part (threaded element, connector, etc.) and a temporary electrode applied at the restrictive ring from the side of the insulating part.
17. The indicator voltage is checked as follows - the voltage of the test set rises smoothly from zero to a value at which the light signals begin to correspond to 25%.
18. The rates and frequency of electrical testing of pointers are given in the table.
Terms of use
19. Before starting work with the pointer, it is necessary to check its serviceability.
The serviceability of pointers that do not have a built-in control body is checked using special devices, which are small-sized sources of increased voltage, or by briefly touching the pointer tip electrode to live parts that are obviously energized.
20. When checking the absence of voltage, the time of direct contact of the working part of the indicator with the controlled current-carrying part must be at least 5 s (in the absence of a signal).
It should be remembered that although some types of voltage indicators can signal the presence of voltage at a distance from live parts, direct contact with them the working part of the pointer is mandatory.
21. In electrical installations with voltages above 1000V, the voltage indicator should be used with dielectric gloves.
Voltage indicators up to 1000V
Purpose, principle of operation and design
22. In electrical installations with voltage up to 1000V, two types of indicators are used: two-pole and single-pole.
Two-pole indicators operating with the flow of active current are designed for electrical installations of alternating and direct current.
Single-pole pointers operating with the flow of capacitive current, designed for electrical installations AC only.
The use of two-pole pointers is preferred.
The use of test lamps to check the absence of voltage is not allowed.
23. Two-pole pointers consist of two cases made of electrically insulating material containing elements that respond to the presence of voltage on the controlled current-carrying parts, and elements of light and (or) sound indication. The housings are interconnected by a flexible wire with a length of at least 1 m. In the places of inputs into the housings, the connecting wire must have shock-absorbing bushings or thickened insulation.
The dimensions of the cases are not standardized, they are determined by ease of use.
Each case of a two-pole pointer must have a rigidly fixed tip electrode, the length of the uninsulated part of which should not exceed 7 mm, except for pointers for overhead lines, in which the length of the uninsulated part of the tip electrodes is determined by the technical specifications.
24. A single-pole pointer has one housing made of electrically insulating material, in which all the elements of the pointer are placed. In addition to the tip electrode that meets the requirements of clause 2.4.25, there must be an electrode on the end or side of the body for contact with the operator's hand.
The dimensions of the case are not standardized, they are determined by ease of use.
Light and sound signals may be continuous or intermittent and must be reliably recognizable.
26. Voltage indicators up to 1000V can also perform additional functions: integrity check electrical circuits, phase wire detection, polarity detection in DC circuits, etc. At the same time, the indicators should not contain switching elements intended for switching operating modes.
Expanding the functionality of the pointer should not reduce the safety of operations to determine the presence or absence of voltage.
Performance tests
27. Electrical tests of voltage indicators up to 1000 V consist of testing the insulation, determining the indication voltage, checking the operation of the indicator at an increased test voltage, checking the current flowing through the indicator at the highest operating voltage of the indicator.
If necessary, the indication voltage in the DC circuits is also checked, as well as the correctness of the polarity indication.
The voltage gradually increases from zero, while the values of the indication voltage and the current flowing through the pointer at the highest operating voltage of the pointer are fixed, after which the pointer is switched off for 1 min. maintained at an increased test voltage exceeding the highest operating voltage of the indicator by 10%.
28. When testing pointers (except for insulation testing), the voltage from the test facility is applied between the tip electrodes (for bipolar pointers) or between the tip electrode and the electrode on the end or side of the housing (for single-pole pointers).
29. When testing the insulation of two-pole indicators, both cases are wrapped in foil, and the connecting wire is lowered into a vessel with water at a temperature of (25 +/- 15) ° C so that the water covers the wire, not reaching the handles of the cases by 8 - 12 mm. One wire from the test setup is connected to the tip electrodes, the second, grounded, to the foil and lowered into the water.
For single-pole pointers, the case is wrapped with foil along the entire length to the limit stop. A gap of at least 10 mm is left between the foil and the contact on the end (side) part of the housing. One wire from the test set is connected to the tip electrode, the other to the foil.
30. The norms and frequency of operational tests of pointers are given in the table.
Terms of use
31. Before starting work with the pointer, it is necessary to check its serviceability by briefly touching live parts that are obviously energized.
32. When checking the absence of voltage, the time of direct contact of the indicator with the controlled current-carrying parts must be at least 5 s.
33. When using single-pole indicators, contact must be ensured between the electrode on the end (side) part of the body and the operator's hand. The use of dielectric gloves is not allowed.
2.4.20. Before you start working with the pointer, you need to check its serviceability.
The serviceability of pointers that do not have a built-in control body is checked using special devices, which are small-sized sources of increased voltage, or by briefly touching the pointer tip electrode to live parts that are obviously energized.
The serviceability of pointers with a built-in control unit is checked in accordance with the operating manuals.
2.4.21. When checking the absence of voltage, the time of direct contact of the working part of the indicator with the controlled current-carrying part must be at least 5 s (in the absence of a signal).
It should be remembered that, although some types of voltage indicators can signal the presence of voltage at a distance from current-carrying parts, direct contact with them by the working part of the indicator is mandatory.
2.4.22. In electrical installations with voltages above 1000 V, the voltage indicator should be used with dielectric gloves.
Voltage indicators up to 1000 V Purpose, principle of operation and design
2.4.23. General technical requirements for voltage indicators up to 1000 V are set out in the state standard.
2.4.24. In electrical installations with voltages up to 1000 V, two types of indicators are used: bipolar and single-pole.
Two-pole indicators operating with the flow of active current are designed for electrical installations of alternating and direct current.
Single-pole indicators operating with the flow of capacitive current are intended for electrical installations only with alternating current.
The use of two-pole pointers is preferred.
The use of test lamps to check the absence of voltage is not allowed.
2.4.25. Two-pole pointers consist of two cases made of electrical insulating material, containing elements that respond to the presence of voltage on the controlled current-carrying parts, and elements of light and (or) sound indication. The housings are interconnected by a flexible wire with a length of at least 1 m. In the places of inputs into the housings, the connecting wire must have shock-absorbing bushings or thickened insulation.
The dimensions of the cases are not standardized, they are determined by ease of use.
Each case of a two-pole pointer must have a rigidly fixed tip electrode, the length of the uninsulated part of which should not exceed 7 mm, except for pointers for overhead lines, in which the length of the uninsulated part of the tip electrodes is determined by the technical specifications.
2.4.26. A single-pole pointer has one housing made of electrically insulating material, in which all the elements of the pointer are placed. In addition to the tip electrode that meets the requirements of clause 2.4.25, there must be an electrode on the end or side of the body for contact with the operator's hand.
The dimensions of the case are not standardized, they are determined by ease of use.
The indication of the presence of voltage can be stepped, supplied in the form of a digital signal, etc.
Light and sound signals may be continuous or intermittent and must be reliably recognizable.
For pointers with a pulse signal, the indication voltage is the voltage at which the interval between pulses does not exceed 1.0 s.
2.4.28. Voltage indicators up to 1000 V can also perform additional functions: checking the integrity of electrical circuits, determining the phase wire, determining the polarity in DC circuits, etc. At the same time, the indicators should not contain switching elements intended for switching operating modes.
Expanding the functionality of the pointer should not reduce the safety of operations to determine the presence or absence of voltage.
8.1 General requirements. Purpose and design of voltage indicators
8.1.1. In electrical installations up to and above 1000 V, voltage indicators of contact and non-contact types should be used to determine the presence and absence of voltage.
General technical requirements for contact-type voltage indicators used in AC and DC electrical installations with voltages up to 1000 V inclusive and in AC electrical installations with voltages above 1000 V (up to 220 kV inclusive) must comply with GOST 20493.
8.1.2. To determine the parameters of contact indicators that are not given in GOST 20493, as well as non-contact voltage indicators, it is necessary to use these Rules, as well as the technical specifications for specific indicators, which must be agreed with the head (base) organization for voltage indicators and approved in in the prescribed manner.
8.1.3. The minimum dimensions of the voltage indicators must correspond to those given in Table 8.1.
Table 8.1.
Minimum dimensions of voltage indicators
8.1.4. Voltage indicators should show the modes "voltage available" or "voltage absent" by changing the signal mode. In this case, the "voltage present" mode must be provided by visual indication and/or audible alarm.
The "no voltage" mode must be ensured by the absence of indication and alarm.
8.1.5. In the case of constant automatic self-checking of the indicator operation, the indication and signaling of serviceability must differ in a significant change in the duration (frequency or timbre - for sound signaling or location - for light indication) of the signal pulse and can be easily distinguished by the employee from the indication of the "voltage present" mode.
8.1.6. Visual indication and audible signal may be continuous, intermittent or variable intensity.
8.1.7. For voltage indicators with continuous visual indication and audible signaling, the indication of the "voltage present" mode must be considered a change in the display or sound mode that is perceptible to the worker.
For voltage gauges with pulsed visual indication and audible signaling, the indication of the "voltage present" mode must be considered such a mode when the interval between visual indication or audible signaling pulses does not exceed 2 s.
8.1.8. When determining the presence of voltage, a clear indication of the mode "voltage present" should be provided:
The intensity of the visual indication, which should be sufficient for perception in the most unfavorable mode in terms of the intensity of ambient lighting, when there is direct sunlight on the voltage indicator in the working position;
Provided that the voltage indicator is oriented with the handle down (the deviation from the vertical in clear weather should be at least 45 °);
Sound signaling of sufficient signal intensity, the requirements for which are given below.
Under "direct sunlight" should be considered the impact of sunlight on the body of the working part of the pointer, shading or indicator. For low-voltage voltage indicators, artificial shading of the indicator is allowed by orienting it accordingly.
8.1.9. In electrical installations, it is necessary to use voltage indicators, which, depending on their design, may have the main (may be the only one) and additional signaling and indication.
8.1.10. For the main indication of the voltage indicator, it is necessary to ensure the intensity of a clear indication of the mode; for additional indication, the requirements can be lowered to an unfavorable mode: the signal is visible on a clear day without direct sunlight.
8.1.11. For the main sound signaling of the voltage indicator, the sound intensity at the working distance must be: at least 75 dB - for a continuous signal or 70 dB - for an intermittent (pulse) signal with a fundamental frequency of 1 to 4.5 kHz.
For additional signaling, the signal level can be reduced to 67 dB.
The method for determining the sound intensity should be given in the technical specifications and in the operating instructions for voltage indicators.
The working distance should be understood as the distance at which the hearing organs are located from the sound element and which is:
400 mm from the acoustic element - for a voltage indicator up to 1000 V inclusive;
400 mm from the end of the handle along its axis - for a voltage indicator with an insulating part up to 2500 mm long;
400 mm from the limiting ring - for a voltage indicator with an insulating part longer than 2500 mm perpendicular to it.
8.1.12. The response time of the voltage indicator at the rated voltage of the electrical installation should not exceed 1.5 s for any type of indicator. The repetition interval of light or sound pulses for impulse voltage indicators should not exceed 1 s at rated voltage.
8.2. Voltage indicators up to 1000 V
8.2.1. In electrical installations up to 1000 V, two types of voltage indicators must be used to check the presence or absence of voltage; two-pole, which operate on the principle of active current flow and must be equipped with automatic protection against damage by test voltage, and single-pole, operating with capacitive current flow.
It is forbidden to use test lamps to check the absence of voltage.
8.2.2. Two-pole voltage indicators intended for use in AC or DC electrical installations must meet the following requirements:
They must have two housings (poles) containing elements of an electrical circuit, the poles of which must be interconnected by a flexible wire at least 1 m long, which does not lose elasticity at sub-zero temperatures. In the places of inputs to the poles, the wire must have shock-absorbing bushings or thickened insulation;
Two-pole voltage indicators up to 1000 V inclusive must be produced in three classes of the upper voltage value at which they can be used: 420 (380 + 10%) V - for electrical installations with a rated voltage of 380 V; up to 730 (660 + 10) V - for electrical installations with a rated voltage of 660 V; up to 1000 V inclusive. Deviations in the direction of increasing the upper voltage value are allowed. Recommended classes: up to 500 V - for electrical installations with a rated voltage of 380 V; up to 750 V - for electrical installations up to 660 V; up to 1000 V inclusive. It is not allowed to exceed the measuring voltage level above 1000 V;
The design of the voltage indicator must have tip contacts and elements that provide visual, acoustic or visual-acoustic voltage indication and signaling. The electrical circuit of such a voltage indicator with a visual (combined) indication may have: either an analog type device; or a system built on the principle of changing the size of the light column relative to the scale; or sign-synthesizing system.
When performing work in electrical installations of alternating current, it is recommended to use single-pole voltage indicators, which are located in one housing and are intended primarily to determine the phase of the voltage.
Single-pole voltage indicators must be produced for the voltage of the electrical installations in which they are used and which must not be less than 110% of the phase voltage.
8.2.4. The elements of the electrical circuit of single-pole voltage indicators must withstand the test voltage for 60 s, which must be 20% higher than the upper value of the operating voltage.
8.2.5. The current flowing through the voltage indicator at the upper value of the operating voltage must not exceed:
10 mA - for bipolar voltage indicators;
0.6 mA - for single-pole indicators.
8.2.6. The electrical circuit of the voltage indicator must be powered only from the voltage being tested.
An independent power supply may only be used for additional indication or signaling.
An autonomous power supply can also be used in the case when, in the event of a failure of this power supply, an indication of the "voltage present" mode is provided.
It is not allowed to charge an autonomous power supply with a current of more than 10 mA without using a two-prong plug.
8.2.7. The failure of an additional alarm or indication shall not lead to the failure of the main alarm or indication.
8.2.8. The threshold of operation of voltage indicators must be within the following limits: not less than 45 V and not more than 90 V ("voltage present" mode).
For voltage indicators, it is allowed to introduce additional indication or signaling with an indication voltage of less than 45 V; in this case, additional indication must be distinguished by its location on the indicator, and the signaling by the main frequency or by the frequency of interruptions must be clearly distinguished from the indication or signaling "voltage present".
The coincidence of the additional and main indication or signaling is also allowed when the indication voltage is 42 V + 2.5%.
8.2.9. The electrical insulation of voltage indicators must withstand the following voltage for 60 s:
I kV - for voltage indicators up to 500 V;
2 kV - for voltage indicators from 500 V to 1000 V.
8.2.10. Voltage meters with such additional functions as checking the integrity of electrical circuits, indicating thresholds or voltage levels, must work stably at maximum voltage values: damage protection must operate automatically for at least 60 s.
8.2.11. The length of the uninsulated part of the tips of the voltage indicators should not exceed 20 mm.
When working in secondary switching circuits, the lugs must be additionally insulated, leaving only the contact parts not longer than 5 mm uninsulated.
The design of the voltage indicator should exclude the possibility of free movement along the axis of the contact-tip, which must be rigidly fixed.
An additional contact tip for performing work on overhead lines should be uninsulated only on the part that is intended for contact with the wire.
8.3. Voltage indicators above 1000 V
8.3.1. Voltage indicators above 1000 V should consist of three parts: working, insulating and handle.
The working part of such voltage indicators must contain elements of the electrical circuit that provide an indication of the "voltage available" mode; the insulating part must be placed between the working part and the handle and may consist of several interconnected parts.
The connection material must provide mechanical strength.
It is allowed to use a telescopic design of the insulating part of the voltage indicators, which should exclude the possibility of accidental folding.
8.3.2. The voltage indicator must have an effective reflective and shading device - to ensure the best perception of light indication in bright ambient light.
8.3.3. The design of the voltage indicator should ensure its operability without grounding the working part, including when working on overhead lines b, 10, 20, 35 kV with supports of all types, regardless of the method of lifting workers to current-carrying parts.
8.3.4. Voltage indicators must operate (provide an indication of the "voltage available" mode) at a voltage not exceeding 25% of the rated voltage - for all voltage classes. For voltage classes up to 3 kV inclusive, the voltage at which the indication of the "voltage present" mode is provided must be determined according to the specifications.
8.3.5. The working part of voltage indicators should not undergo electrical tests, except in cases where the design of the indicator can cause a phase-to-phase short circuit or a short circuit to earth.
A record of the need to conduct electrical tests of the working part of the voltage indicator must be made in the technical specification and in the instruction manual for the indicator.
In the event that electrical tests of the voltage indicator are carried out, its working part must withstand for 60 s an increased voltage not less than that indicated in Table 8.2.
Table 8.2.
Test voltage of the working part of voltage indicators above 1000 V
8.3.6. The insulating part of the voltage indicators must withstand for 60 s:
Three-fold linear voltage - for indicators used in electrical installations from 1 to 110 kV;
Triple phase voltage - for indicators used in electrical installations from 110 kV and above, but not less than the test voltage values given in Table 8.3.
Table 8.3.
Test voltage of the insulating part of voltage indicators is higher than 1000 V
8.3.7. An indication or signaling element of a contact voltage indicator in electrical installations for a certain voltage should not be triggered by the influence of neighboring circuits of the same voltage, spaced from its working part at the distances indicated in Table 8.4.
Table 8.4.
Distances from the working part of the voltage indicator above 1000 V to the nearest wire of adjacent circuits of the same voltage
8.3.8. The value of the bending of the insulating parts of voltage indicators, measured as the ratio of the deflection at the point of application of the bending force to the length of the insulating part, should not exceed:
10% - for voltage indicators above 35 kV;
20% - for pointers with a telescopic design of the insulating part.
8.4. Contact voltage indicators above 1000 V with a gas discharge lamp
8.4.1. To perform work in electrical installations from 1 to 220 kV, voltage indicators with a gas discharge lamp are used, the principle of operation of which is based on the flow of capacitive current through the electrical circuit of the indicator and which must be made of two types:
Pointers in which a capacitive current flows directly through the discharge lamp and causes it to glow;
Pointers in which electrical energy accumulates in a capacitor and causes a gas discharge lamp to flash when the capacitor is discharged through it (using an S-like current-voltage characteristic of the lamp).
Voltage gauges may have an additional audible alarm associated with light indication, or an independent audible alarm.
8.5. Non-contact voltage indicators above 1000 V
8.5.1. To check the presence or absence of voltage in electrical networks voltage from 6 to 220 kV inclusive, non-contact voltage indicators above 1000 V should be used, the operation of which is based on the principle of detecting the presence of an electric field near live parts.
8.5.2. In non-contact voltage indicators above 1000 V, for visual indication, incandescent lamps, LEDs, sign synthesizers or other elements should be used that provide a clear perception of the "voltage present" mode.
8.5.3. Non-contact voltage indicators should consist of a working, insulating part, a handle.
The requirements for the working and insulating parts of such voltage meters must comply with paragraphs 8.3.5 and 8.3.6 of these Rules.
If the voltage gauge is used in signaling mode, it may be without an insulating part.
8.5.4. The power source of the contactless pointer without additional recharging must ensure the operation of the pointer:
In standby mode - for at least 12 hours;
In the mode of constant indication "voltage available" - at least 10 minutes.
8.5.5. The sensitivity of the voltage indicator, oriented with the axis of the working part parallel to the surface of the live parts of the electrical installation, should decrease by no more than 2-4 times.
8.5.6. Due to the absence of GSTU for non-contact voltage indicators, their sensitivity (sensing distance) in the case of different rated voltages must comply with Table 8.5.
8.5.7. The voltage indicator should not work if it is introduced into the space between adjacent phases of the electrical installation.
Table 8.5.
Sensing distances of non-contact voltage indicators
Purpose
2.4.1. Voltage indicators are designed to determine the presence or absence of voltage on the current-carrying parts of electrical installations.
2.4.2. General technical requirements for voltage meters are set out in the state standard.
Voltage indicators above 1000 V
Principle of operation and design
2.4.3. Voltage indicators above 1000 V react to the capacitive current flowing through the indicator when its working part is introduced into the electric field formed by the current-carrying parts of electrical installations that are energized, and the "ground" and grounded structures of electrical installations.
2.4.4. Pointers should contain the main parts: working, indicator, insulating, as well as a handle.
2.4.5. The working part contains elements that respond to the presence of voltage on the controlled current-carrying parts.
Cases of working parts of voltage indicators up to 20 kV inclusive must be made of electrically insulating materials with stable dielectric characteristics. Cases of working parts of voltage indicators of 35 kV and above can be made of metal.
The working part may contain a tip electrode for direct contact with controlled current-carrying parts and not contain a tip electrode (non-contact pointers).
The indicator part, which can be combined with the working part, contains elements of light or combined (light and sound) indication. Gas-discharge lamps, light-emitting diodes or other indicators can be used as elements of light indication. Light and sound signals must be reliably recognizable. The audio signal should have a frequency of 1 - 4 kHz and an interruption frequency of 2 - 4 Hz when indicating phase voltage. The sound signal level must be at least 70 dB at a distance of 1 m along the axis of the sound emitter.
The working part may also contain an organ of its own control of serviceability. Control can be carried out by pressing a button or be automatic, by periodically supplying special control signals. At the same time, it should be possible to fully check the serviceability of the electrical circuits of the working and indicator parts.
Working parts should not contain switching elements designed to turn on power or switch ranges.
2.4.6. The insulating part of the pointers must be made of the materials specified in clause 2.1.2.
The insulating part may be composed of several links. To connect the links to each other, parts made of metal or insulating material can be used. The use of a telescopic design is allowed, while spontaneous folding should be excluded.
2.4.7. The handle can be one piece with the insulating part or be a separate link.
2.4.8. The design and weight of the pointers should ensure that one person can work with them.
2.4.9. The electrical circuit and design of the pointer must ensure its operability without grounding the working part of the pointer, including when checking the absence of voltage, carried out from telescopic towers or from wooden and reinforced concrete supports of 6-10 kV overhead lines.
2.4.10. The minimum dimensions of the insulating parts and handles of voltage indicators above 1000 V are given in Table. 2.4.
Table 2.4
MINIMUM DIMENSIONS OF INSULATING PARTS AND HANDLES OF VOLTAGE INDICATORS ABOVE 1000 V
2.4.11. The indication voltage of the voltage indicator should not exceed 25% of the rated voltage of the electrical installation.
For pointers without a built-in power supply with a pulse signal, the indication voltage is the voltage at which the signal interruption frequency is at least 0.7 Hz.
For pointers with a built-in power supply with a pulse signal, the indication voltage is the voltage at which the signal interruption frequency is at least 1 Hz.
For other indicators, the indication voltage is the voltage at which there are distinct light (light and sound) signals.
2.4.12. The time of appearance of the first signal after touching the current-carrying part under voltage equal to 90% of the rated phase voltage should not exceed 1.5 s.
2.4.13. The working part of the indicator for a certain voltage should not respond to the influence of neighboring circuits of the same voltage, spaced from the working part at the distances indicated in Table. 2.5.
Table 2.5
DISTANCE TO THE NEAREST WIRE OF THE ADJACENT CIRCUIT
Performance tests
2.4.14. During operation, mechanical tests of voltage indicators are not carried out.
2.4.15. Electrical tests of voltage indicators consist of testing the insulating part with increased voltage and determining the indication voltage.
The test of the working part of voltage indicators up to 35 kV is carried out for indicators of such a design, during operations with which the working part can cause an interphase short circuit or a phase-to-ground short circuit. The need to test the insulation of the working part is determined by the operating manuals.
For voltage meters with a built-in power source, its condition is monitored and, if necessary, the batteries are recharged or the batteries are replaced.
2.4.16. When testing the insulation of the working part, voltage is applied between the tip electrode and the screw connector. If the pointer does not have a screw connector electrically connected to the indication elements, then the auxiliary electrode for connecting the wire of the test setup is installed at the boundary of the working part.
2.4.17. When testing the insulating part, voltage is applied between the element of its articulation with the working part (threaded element, connector, etc.) and a temporary electrode applied at the restrictive ring from the side of the insulating part.
2.4.18. The indication voltage of indicators with a gas-discharge indicator lamp is determined according to the same scheme by which the insulation of the working part is tested (clause 2.4.16).
When determining the indication voltage of other indicators with a tip electrode, it is connected to the high-voltage output of the test facility. When determining the indication voltage of pointers without a tip electrode, it is necessary to touch the end side of the working part (head) of the pointer to the high-voltage output of the test setup.
In both latter cases, the auxiliary electrode is not installed on the indicator and the ground terminal of the test set is not connected.
The voltage of the test setup smoothly rises from zero to the value at which the light signals begin to comply with the requirements of clause 2.4.11.
2.4.19. The norms and frequency of electrical testing of pointers are given in Appendix 7.
Terms of use
2.4.20. Before you start working with the pointer, you need to check its serviceability.
The serviceability of pointers that do not have a built-in control body is checked using special devices, which are small-sized sources of increased voltage, or by briefly touching the pointer tip electrode to live parts that are obviously energized.
The serviceability of pointers with a built-in control unit is checked in accordance with the operating manuals.
2.4.21. When checking the absence of voltage, the time of direct contact of the working part of the indicator with the controlled current-carrying part must be at least 5 s (in the absence of a signal).
It should be remembered that, although some types of voltage indicators can signal the presence of voltage at a distance from current-carrying parts, direct contact with them by the working part of the indicator is mandatory.
2.4.22. In electrical installations with voltages above 1000 V, the voltage indicator should be used with dielectric gloves.
Voltage indicators up to 1000 V
Purpose, principle of operation and design
2.4.23. General technical requirements for voltage indicators up to 1000 V are set out in the state standard.
2.4.24. In electrical installations with voltages up to 1000 V, two types of indicators are used: bipolar and single-pole.
Two-pole indicators operating with the flow of active current are designed for electrical installations of alternating and direct current.
Single-pole indicators operating with the flow of capacitive current are intended for electrical installations only with alternating current.
The use of two-pole pointers is preferred.
The use of test lamps to check the absence of voltage is not allowed.
2.4.25. Two-pole pointers consist of two cases made of electrical insulating material, containing elements that respond to the presence of voltage on the controlled current-carrying parts, and elements of light and (or) sound indication. The housings are interconnected by a flexible wire with a length of at least 1 m. In the places of inputs into the housings, the connecting wire must have shock-absorbing bushings or thickened insulation.
The dimensions of the cases are not standardized, they are determined by ease of use.
Each case of a two-pole pointer must have a rigidly fixed tip electrode, the length of the uninsulated part of which should not exceed 7 mm, except for pointers for overhead lines, in which the length of the uninsulated part of the tip electrodes is determined by the technical specifications.
2.4.26. A single-pole pointer has one housing made of electrically insulating material, in which all the elements of the pointer are placed. In addition to the tip electrode that meets the requirements of clause 2.4.25, there must be an electrode on the end or side of the body for contact with the operator's hand.
The dimensions of the case are not standardized, they are determined by ease of use.
The indication of the presence of voltage can be stepped, supplied in the form of a digital signal, etc.
Light and sound signals may be continuous or intermittent and must be reliably recognizable.
For pointers with a pulse signal, the indication voltage is the voltage at which the interval between pulses does not exceed 1.0 s.
2.4.28. Voltage indicators up to 1000 V can also perform additional functions: checking the integrity of electrical circuits, determining the phase wire, determining the polarity in DC circuits, etc. At the same time, the indicators should not contain switching elements intended for switching operating modes.
Expanding the functionality of the pointer should not reduce the safety of operations to determine the presence or absence of voltage.
Performance tests
2.4.29. Electrical tests of voltage indicators up to 1000 V consist of testing the insulation, determining the indication voltage, checking the operation of the indicator at an increased test voltage, checking the current flowing through the indicator at the highest operating voltage of the indicator.
If necessary, the indication voltage in the DC circuits is also checked, as well as the correctness of the polarity indication.
The voltage gradually increases from zero, while the values of the indication voltage and the current flowing through the pointer at the highest operating voltage of the pointer are fixed, after which the pointer is switched off for 1 min. maintained at an increased test voltage exceeding the highest operating voltage of the indicator by 10%.
2.4.30. When testing indicators (except for insulation testing), the voltage from the test apparatus is applied between the tip electrodes (for bipolar indicators) or between the tip electrode and the electrode on the end or side of the housing (for single-pole indicators).
Rice. 2.1. Schematic diagram of testing the dielectric strength of the insulation of the handles and wire of the voltage indicator:
1 - test pointer; 2 - test transformer; 3 - bath with water; 4 - electrode
2.4.31. When testing the insulation of two-pole indicators, both cases are wrapped in foil, and the connecting wire is lowered into a vessel with water at a temperature of (25 +/- 15) ° C so that the water covers the wire, not reaching the handles of the cases by 8 - 12 mm. One wire from the test setup is connected to the tip electrodes, the second, grounded, to the foil and lowered into the water (diagram variant - Fig. 2.1).
For single-pole pointers, the case is wrapped with foil along the entire length to the limit stop. A gap of at least 10 mm is left between the foil and the contact on the end (side) part of the housing. One wire from the test set is connected to the tip electrode, the other to the foil.
One of the most important devices for an electrician and other electricians is a voltage gauge. The safety of an electrician or operational personnel directly depends on it, because according to the testimony this device can be determined electricity in the conductor or not. In this article we will consider the types of voltage indicators, the purpose and rules for using them.
Device types
Pointers up to 1000 volts and above 1000 volts have different external and design features. For low voltage measurements, up to 1 kV, there are two types of devices:
- single-pole, reacting to the flow of capacitive current;
- bipolar, gives an indication when an active current flows through it.
The single-pole pointer is designed to work in alternating current circuits, to detect a phase conductor, in lighting circuits, when phasing an electric meter, and checking cartridges in lamps. Simply put, to detect live wires.
Single-pole phase indicating devices are of the same design and usually consist of a gas discharge indicator lamp, with an ignition threshold of 90 to 120 volts and a 1 MΩ resistor connected in series. The resistor limits the current to a safe value, about 0.5 mA.
Indicator IN - 90 is made in the form of a screwdriver.
The disadvantages of such indicators include low sensitivity (the indication threshold of some devices starts from 90 volts), as well as sensitivity to pickups in adjacent wires.
For networks above 1000 volts, voltage indicators are made with handles made of insulating material and long, excluding the approach of a person to current-carrying elements. Appearance UVN-10 is shown in the photo below:
When measuring voltages above 1000 volts, they resort to the use of additional protective equipment: rubber gloves, boots or an insulating mat. You can find out from our article!
A two-pole pointer consists of two cases of insulating material and a flexible insulated copper conductor that connects them. Scheme of a two-pole voltage indicator type UNN-10:
In this circuit, the discharge indicator is shunted with a resistor, which makes the circuit insensitive to induced voltages. Also, on its basis, an indicator with a voltage value indicator UN-1 is produced:
This device uses a special linear discharge lamp and a scale on the body with a graduation of 127, 220, 380, 500 Volts.
There are also universal voltage indicators, for checking the presence of voltage and indicating its value from 12 to 380 V. For operation in DC circuits, up to 500 volts and alternating current, up to 380 volts. They can be additionally used to test the integrity of connections.
In these devices, LEDs are used as indicator lights, and a large capacitor is used as a power source.
The digital voltage gauge has an LCD screen with printed values in volts. At the maximum value of 220 volts, all values from the minimum to the maximum are lit on the screen. Those. this tester shows an approximate value. The only plus of this model is the lack of a power source.
Non-contact indicators are designed to detect live conductors, including those hidden in walls or panels. The circuit of this device responds to an alternating electromagnetic field, is equipped with light and sound indication. We talked more about these devices when we talked about.
Terms of use
Before using the voltage indicator, you must make sure that it is in good condition. To do this, in a known working network, you need to check the indication of the device. Only after a positive result is it allowed to use it.
It is forbidden to use an incandescent lamp as an indicator, due to its low reliability and high injury risk. When searching for a phase, it is necessary to install the pointer probe on the conductor of interest, hold the device in the right hand, hide the left hand behind the back, touch the end contact with the thumb of the right hand. This is for a single pole indicator.
For a two-pole probe with an indicator, put it on the conductor or terminal of interest, and the second probe on zero or the adjacent phase. As you can see, there is nothing complicated in working with these devices. Be aware of the dangers of working under voltage, and observe personal safety measures.
So we examined the types, purpose and rules for using a voltage indicator. We hope that the information provided was informative and useful for you!