Devices for tuning HF and VHF antennas. Device for tuning a feeder to a traveling wave on several fixed waves Wave tuning device 5 letters
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The Volna device, like the Poisk-1 device, is based on measuring the components of higher harmonics in the ground fault current.
Compared to the Poisk-1 device, the Volna device has more high sensitivity with significantly smaller dimensions and weight and simpler control. Thanks to special measures, the device has increased selectivity compared to other devices. Increased selectivity is ensured by using a corrector in the device, which reduces the dependence of the device readings on the distance between the device and the line wires (Fig. 30. b), as well as on the value of the transition resistance at the point of closure.
Structural scheme The device (Fig. 31) contains a magnetic sensor M, which is an inductive coil with an open ferrite rod core, which, together with capacitors 1 connected in parallel to it, forms a resonant circuit tuned to a frequency of 550 or 250 Hz and connected to the input of the emitter follower 2.
Rice. 31. Block diagram of the “Volna” device
The emitter circuit of the repeater includes a voltage divider 3, which provides stepwise adjustment of the sensitivity of the device. The signal taken from the divider is fed through control unit 8 to the input of the first transistor amplifier alternating current 4, at the output of which a microammeter of the magnetoelectric system 5 is connected through a rectification circuit.
Electric antenna A, which is a metal plate built into the body of the device, is connected through an emitter follower 6 to the input of the second AC amplifier 7. The amplifier 7 has two outputs - AC and direct current. The DC output acts on amplifier 4, providing automatic stabilization of the readings of the output device when the distance from the device to the line wires changes by increasing (or decreasing) the gain of the first amplifier when decreasing (or increasing) the electric field at the measurement point and, consequently, the voltage at the antenna . This solution also provides partial compensation for changes in instrument readings when the transition resistance changes at the location of the ground fault during the search for the fault location.
The AC output of the second amplifier through control unit 8 is supplied to the input of the last two stages of the first amplifier, which allows, in the mode of monitoring the presence of a ground fault in the network, to control the electric field strength according to the readings of the output device.
Control unit 8 consists of a switch for the operating mode and sensitivity of the device and a power button.
The device provides the ability to monitor the health of the built-in power supply using an output device.
In Fig. 32 presented circuit diagram devices. Magnetic sensor M has a working winding 1 and a test winding 2, which is used to configure the device at the manufacturer or to check it during operation. Winding 1, together with parallel-connected capacitors, forms a resonant circuit tuned to a frequency of 250 or 550 Hz and connected to the input of a composite emitter follower on transistors VT1 and VT2, in the emitter circuit of which a voltage divider is included. From the divider, the signal enters through the I?C high-pass filter to the input of the first transistor alternating current amplifier (transistors VT3-VT6), the output of which is connected through a rectification circuit to a microammeter of the magnetoelectric system RA. Electrical antenna A, through an emitter follower on transistor VT7, is connected to the input of the second AC amplifier on transistors VT8-VT10.
Rice. 32. Schematic diagram of the “Volna” device
The AC output of this amplifier (from the collector of the VTJO transistor) is fed through a switch to the input of the last two stages of the first amplifier, which makes it possible to control the electric field strength according to the readings of the PA device. The DC output of the second amplifier is connected to the base of transistor VT4 of the first amplifier, which ensures that the gain of the first amplifier changes when the voltage on the antenna changes. The switch is used for stepwise sensitivity adjustment, to switch the device to control mode of the device's power source. The device is powered by the SB button for the duration of the measurement.
Basic technical data of the Volna device
Controlled frequencies. Hz 250 and 550
Sensitivity to magnetic field, A/m (when the instrument needle deflects to 100% of the scale), at frequency:
550 Hz 1.5-10"4
250 Hz 1.5-10 3
Sensitivity to electric field, V/m, per
frequency 50 Hz.100
Operating temperature range, °C. .From -40 to +40
Power supply. . . Element 3336X (3336L)
Consumption of the device from the power source. Tue 50-10 3
Dimensions, mm 230X85X95
Weight, kg 1.5
The Volna-M device, like the Volna device, uses frequencies of 550 and 250 Hz to monitor short circuits in the network. Compared to the Volna device, this device has more stable characteristics, equipped with an element for automatic monitoring of the presence of a ground fault.
As a magnetic sensor M (Fig. 33), the device uses an original sensor made in the form of two inductive coils arranged in series with open ferrite cores. Together with capacitors C/ and C2, the sensor forms a resonant circuit tuned to the frequency band.
The signal from the output of the magnetic sensor is amplified by an AC amplifier on the A1 chip. From the output of the amplifier, the signal is fed to the input of a scale amplifier on chip A2. The sensitivity of the device is changed by changing the transfer coefficient of the scale amplifier using a switch. At the same time, the same switch supplies a signal from the output of amplifier A2 to the measuring device PA.
The signal from antenna A is fed to the input of the amplifier-limiter on chip A3. The output of amplifier A3 is connected to the gate via a rectifier field effect transistor VTI, connected in parallel with the output of the magnetic sensor M. Using transistor VT1, automatic stabilization of the device readings is ensured when the distance from the device to the line wires changes. The correction action is limited using the Zener diode VD1.
Rice. 33. Schematic diagram of the Volna-M device
From the output of amplifier A3, the signal is simultaneously supplied through switch S/4 to the PA measuring device, which allows, when the switch is moved to position 2, to monitor the presence of a short circuit in the network. When the device is operating in current control mode, the presence of a short circuit in the network is monitored using the VD2 LED. The LED lights up when there is a short circuit in the network and the operator and the device are in an area of up to 10 m from the line axis. The supply voltage converter is made in the form of a master oscillator on transistors VT2-VT3, which controls the switching of transistors VT4-VT5 in the circuits of storage capacitors SZ-S4 with a frequency of 36 kHz.
Rest specifications The Volna-M device is the same as the Volna device.
3.3.1 Enter the device setup menu by pressing the “MENU” key. The following menu appears on the display.
The second line contains the name of the measurements taken (in in this case state technical inspection of vehicles).
The third line contains information about what is installed in this moment measurement range.
The fourth line is the calibration correction.
The fifth line is the data representation type.
Sixth line – transition to calibration mode.
The seventh line is the polarization of the microphone (the “OFF” position means 0 V).
The eighth line is to activate/deactivate USB.
Ninth line – select telemetry by digital channel. The tenth line is for adjusting the contrast of the indicator.
Eleventh line – turn on/off the backlight.
The twelfth and thirteenth lines are the date and time.
The last line of this window displays the battery voltage.
3.3.2 The “ ” keys allow you to move up and down through the “SETUP” menu. To change the value the desired option, you must first select it (the “ ” keys). If the option has switchable values (“USB OFF”, etc.), then use the “<==>» sequentially cycle through the available values. After selection desired value, moves to the next menu item (keys). The “Note”, “Date”, “Time” parameters are edited differently (see later in this paragraph, as well as the “Setting the built-in clock and calendar” item). The line with the calibration correction is provided in this window for information only (see paragraph “Device Calibration”). Setting up the device to monitor the external noise of the telephone exchange consists of the following steps.
a) After turning on the device, in the “Device Selection” menu, you must select the “GOST R 52231” option and press the “MENU” key to go to the “Settings” menu.
b) It is necessary to make sure that the calibration correction (КК:...) corresponding to the passport is installed. Otherwise, the correct calibration correction is established.
To exit from the “SETUP” menu to the measurement window, press the “MENU” key.
2.4 Instrument calibration. In cases provided for by measurement methods, it is necessary to calibrate the sound level meter.
Calibration verification is carried out using an acoustic calibrator. Optimally, the CAL200 calibrator can produce 94 or 114 dB sound pressure levels (switchable) at 1000 Hz.
To carry out calibration, you must insert the microphone into the calibrator socket, maintaining their alignment. In this case, the calibrator and microphone must be at the same temperature.
The calibration correction value is set to 0.0 dBA (the procedure for changing the calibration correction is given below).
You go to the measurement window (by pressing the “MENU” key while in the “Settings” window).
After about a minute, the calibrator turns on and the measurement mode starts (using the “START” key). After the sound level readings have stabilized at FAST characteristic(topmost number large print) this value is remembered (L FAST, A).
The QC calibration correction is calculated using the formula:
where L FAST , A – instrument readings, dBA;
ΔL(f) – attenuation of characteristic A at the calibrator frequency (Table 1);
L CAL – sound pressure level created by the calibrator.
Table 1 – Relative frequency response device "OKTAVA-101A-GTO" in dB (for the reference direction sound wave and for reference frequency 1000 Hz)
| Rated frequencies, Hz | A | Limit deviation (electrical method) | Maximum deviation (free field) |
| -70,4 | +1,0; -∞ | +3,5; -∞ | |
| 12,5 | -63,4 | +0,8; -∞ | +3,0; -∞ |
| -56,7 | +0,8; -3,5 | +2,5; -4,5 | |
| -50,5 | +0,8; -2,0 | ±2.5 | |
| -44,7 | +0,5; -1,5 | +2,5; -2,0 | |
| 31,5 | -39,4 | +0,5; -1,0 | ±1.5 |
| -34,6 | ±0.3; -1.0 | ±1.5 | |
| -30,2 | ±0.3; -0.7 | ±1.5 | |
| -26,2 | +0,3; -0,5 | ±1.5 | |
| -22,5 | +0,3; -0,5 | ±1.5 | |
| -19,1 | ±0.3 | ±1.0 | |
| -16,1 | ±0.3 | ±1.0 | |
| -13,4 | ±0.3 | ±1.0 | |
| -10,9 | ±0.3 | ±1.0 | |
| -8,6 | ±0.3 | ±1.0 | |
| -6,6 | ±0.3 | ±1.0 | |
| -4,8 | ±0.3 | ±1.0 | |
| -3,2 | ±0.3 | ±1.0 | |
| -1,9 | ±0.3 | ±1.0 | |
| -0,8 | ±0.3 | ±1.0 | |
| 0,0 | ±1.0 | ||
| +0,6 | ±0.3 | ±1.0 | |
| +1,0 | ±0.3 | ±1.0 | |
| +1,2 | ±0.3 | ±1.0 | |
| +1,3 | ±0.3 | ±1.0 | |
| +1,2 | ±0.5 | ±1.0 | |
| +1,0 | ±0.5 | ±1.0 | |
| +0,5 | ±0.5 | ±1.5 | |
| -0,1 | ±0.5 | +1,5; -2,0 | |
| -1,1 | ±0.5 | +1,5; -3,0 | |
| -2,5 | ±0.5 | +2,0; -4,0 | |
| -4,3 | ±0.5 | +3,0; -6,0 | |
| -6,6 | ±0.5 | +3,0; -∞ |
Continuation of Table 1
Example:
Let a calibrator be used for calibration, creating a sound level of 114.0 dB at a frequency of 250 Hz. The device readings on the FAST characteristic with a calibration correction of 0.0 dB are equal to 104 dBA.
L FAST, A = 104.0 dBA;
ΔL(f) = -8.6 dB (Table 1);
L CAL = 114.0 dB;
CC = 104.0 - (-8.6) -114.0 = -1.4 dB.
To calibrate the device, you must first enter the “SETUP” menu (MENU key), use the keys to highlight the “Calibration” item and then press the YES or => key
To change the calibration correction, you must first enter the “SETUP” menu (MENU key), use the keys to highlight the “Calibration” item and then press the YES or => key. The CALIBRATION menu appears on the screen.
In the “Calib. Correction" is the value corresponding to the previous calibration (or the "default" value: 00.00 dB).
If you need to change the value of the calibration correction, you must press the YES key to enter the editing mode, and then enter the correction value known from the passport data (in the form at the end of the sound level meter operating manual) or from the results of the procedure described in the previous paragraph: keys<==>move the cursor marker through the digits of the number, and the keys scroll the digits in the field of the highlighted digit. After entering the required number, press the YES key. The change to the calibration correction is complete.
2.5 Starting and stopping measurements. After exiting the “Settings” menu to the main state (MENU key), a window corresponding to the selected type of data presentation appears on the screen.
The third line is the sound level (large) on the FAST characteristic in dBA. The fifth line is the maximum sound level on the FAST characteristic in dBA during the measurement time. Sixth line - minimum level sound on the FAST characteristic, dBA. The seventh line is the equivalent sound level in dBa. PK – peak sound level, dBA. SEL – sound exposure level; hh:mm:ss – duration of measurements.
The measurement is started using the START/STOP key. The user can see that measurements are being taken by changing the measurement duration in the bottom line. Pressing the START/STOP key again stops the measurement process without resetting the data and measurement duration. The RESET key performs a general reset of the detector block, data display and measurement duration. It can be pressed in either the START or STOP state.
NOTE: Immediately after starting measurements or after pressing the RESET key, the device shows zero values for the MAX and MIN parameters. This lasts approximately 7 s. This delay is provided to obtain statistically reliable results.
The duration of measurements is counted from the moment the START button is first pressed (that is, when the data buffer is cleared) minus the time when the device was in the STOP state (without resetting):
START___ T1 ___STOP___ T2 ___START___ T3 ___
Duration T1+TZ.
When you press the RESET key, the measurement duration is reset to zero along with the contents of the detector block.
START___ T1 ___RESET___ T2 ___STOP___ T3 ___START___ T4 ___
Duration T2+T4.
If the measuring circuit is overloaded, then top line O.V. it stands out last line. This overload indication remains on the indicator until the measurements are reset. If an overload occurs, press the RESET key. If the overload indication does not disappear, this means that the measured signal level exceeds the upper limit of the currently set measurement range.
In addition to the global overload indication, the device provides an indication of the current overload, which does not relate to the entire measurement, but only to the current moment time. It is indicated by an up arrow to the left of the current adjusted sound level.
The device provides an indication that the signal level has dropped below the minimum measurement limit of the established range (insensitive to the input). This indication is represented by a down arrow to the left of the currently adjusted sound level.
When taking measurements, the microphone must be pointed at the sound source. The sound level meter is located between the sound source and the operator at a distance of at least 50 cm from the operator (on a tripod or at arm's length).
When measuring noise outdoors in strong wind conditions, use the WS001 wind deflector.
2.6 Turning off the device, switching the measurement mode. To turn off the device, you need to stop the measurements (STOP key), press and hold the OFF key until you exit to the “DEVICE SELECTION” menu (see above). After this, you must press the OFF key again.
Modern means of communication make it possible to maintain contact at a distance, regardless of the weather, cellular coverage or type of terrain. This was made possible thanks to radio waves different frequencies. For correct operation device, you need to know how to set up the radio. It is worth noting that the market offers wide choose devices aimed at universal use or a narrower specialization (automobile, hunting, railway radio stations).
general information
Any radio must be tuned to a specific frequency. At incorrect configuration an amateur or professional device will operate with interference or at incomplete power. Latest modifications digital devices do not require special adjustments, since they have the function automatic settings. The remaining devices are divided into portable (portable) or stationary (car) radios. The configuration of both modifications has its own nuances, although general principle similar in many ways.
How to set up a portable radio?
Amateur portable radios operate in the 433-434 MHz range. They do not need to be registered by a radio frequency center, so they are quite easy to set up. If you plan to increase the power of the device, find out about the possibility of using a detachable antenna before purchasing. Another important point is the aggregation of walkie-talkies among themselves. To do this, you need to set the same numbers and subcode on each device.
After carrying out these manipulations, the selected devices will work harmoniously with each other. To communicate, you just need to press and hold the conversation activation key. After releasing the button, the device switches to a signal from another radio. An important point in setting up a portable device is the selection of an individual signal for identification (call sign). Its role can be any digital or alphabetic code that has a unique origin for the selected communication system.
Antenna setup
Let's consider general recommendations, how to set up a portable radio in the antenna part. To accurately correct an element, a special analyzer will be required. As an alternative, you can use an SWR meter. It will allow you to adjust the antenna to the minimum stable wave coefficient. Most often, a coefficient of 1.5 or less is considered optimal.
It is worth considering that the higher the SWR value, the greater the loss of signal transmitting power. Ideally, this parameter should approach unity, but in practice it is almost impossible to achieve such a result. If the VAC exceeds three units, it is quite possible to damage the transmitter stage. From this we can conclude that an untuned walkie-talkie can quickly break down.
Car modification
How to configure (stationary) type? You must first complete a number of mandatory procedures that will increase the efficiency of further configuration and minimize the likelihood of transceiver failure during operation. The device in question is a stationary unit fixed in the cabin vehicle, And remote antenna. It is the last element that plays a significant role in signal reception and transmission. Therefore, it is necessary to know the basic rules for installing a receiving remote device.
Installing a car antenna
It is not allowed to install the element on load-bearing parts, the best option will become a body. This will protect the airwaves from possible losses in signal reception and transformation.
In addition, the following points are important:
- Try to install the antenna at the highest point of the body. This will improve the quality of reception.
- The working part of the antenna is installed at a distance of at least 500 millimeters from any parallel metal surfaces. This will make it possible to avoid absorption and reflection of the incoming signal.
- Placement on the roof of a car has a certain influence on the stable wave coefficient. Therefore, fix such an element in one position after removal.
After spending correct installation antenna, proceed to its configuration.
Antenna setup for a stationary walkie-talkie
To configure the channel of a stationary radio, first configure the antenna. For this, it is best to use a professional analyzer. If this is not available, use an SWR meter. Work is carried out on a clean and level surface, away from metal or concrete interference, as well as other analogues of the 27 MHz range.
First, connect the SWR meter. Then measurements are taken on channels and grids to display a large picture. Calibrate the SWR meter by setting the toggle switch on the front panel to FWD mode. The radio is set to channel No. 20 of AM modulation. Then activate and hold the talk key while simultaneously turning the CAL knob clockwise until the device pointer is set to the far right SET position.
Without releasing the button on the PTT switch, switch the SWR meter toggle switch to the REF position. Record the data generated by the device. After finding the minimum SWR, adjust the antenna to the required frequency. If the limit is lower or higher than the required frequency, the antenna is shortened or lengthened, respectively. The measurements are repeated until the SWR coefficient reaches 1.5 or less.
How about the wave of truckers?
Let's look at this procedure using the Sirio T3 Mag antenna as an example (range within 5 km):
- The antenna is mounted on the central part of the roof, after which the protective cap is removed and the adjusting screw is tightened until it stops.
- An SWR meter is installed between the radio station and the antenna.
- Turn on the radio and set the “long-range” mode (channel No. 15 on AM).
- After pressing the PTT, use the SWR adjustment knob to move the arrow to the SET position.
- While holding the PTT switch, move the SWR lever to the REF position, and observe the current value of the device on the upper scale. If the coefficient is higher than 1.5, use the adjusting screw to adjust the readings to within 1-1.5.
- The correction screw is fixed with a locknut, the cap is put on and the SWR readings are rechecked.
Knowing how to set up a truckers radio, you need to take into account that these elements are narrowband. Therefore, it is better to perform settings on the main working channel.
"Megadjet"
First, the radio is switched to 240 channel mode using the AM/FM-ON combination. You can switch to the Russian grid by typing DW/M2-ON. Domestic frequencies end in 0, European waves end in 5.
How to set up the Megadjet radio? You can do this yourself by studying the instructions. Briefly, the following points can be noted:
- First, turn on the radio station using the VOL/Off knob and set the required sound volume.
- Using the SQ regulator, the noise suppression threshold is adjusted.
- Using the UP/DN switch buttons, select the desired channel.
- To set the transmission mode, hold down the PTT control and speak into the microphone at a distance of 50 mm.
- To receive, release the PTT and listen to the received message, adjusting the volume and noise reduction level.
"Baofeng"
Next, let's look at how to configure the Baofeng walkie-talkie. Default, operating frequency device is 2.5 kHz. General settings identical for portable radios. Below are the ways to program the device.
Simplex channels:
- Go to VFO A.
- Press the Band button to select the VHF mode.
- In the menu, type ‘27’ and press menu.
- Then use a free memory cell, which is searched using the UP/DOWN buttons.
- The selected frequency is confirmed by pressing the menu key again.
- To exit - Exit.
Repeater-shift channels:
- Switch to VFO A mode.
- Select UHF or VHF using the Band key.
- Select the receiving frequency.
- They find ‘27’ in the menu, then back to the menu.
- They look for a free memory cell, as in the previous case.
- Use the "menu" button to confirm your choice.
- Press EXIT.
- Then enter the menu again, select ‘27’, press “menu” twice.
Finally
The above describes how to set up a walkie-talkie. The wave should be selected depending on the type of device, as well as the country where the device is used. The antenna plays an important role in the configuration of portable and stationary walkie-talkies. Therefore, its installation and configuration should be given Special attention. If the device is adjusted correctly, you will be able to easily communicate with the respondent at the distance specified in the instructions for the device.
On modern market There are many portable and car radio transmitters presented. Among them, you can easily choose the option that best suits your needs. It is worth noting that digital modern models are configured automatically, but their price is an order of magnitude higher than the considered analogues.
Each antenna has its own resonant frequency at which it emits or receives maximum energy. At this frequency, the antenna resistance has an active and active character. The line supplying energy to the antenna at the resonant frequency should have low losses and should not radiate. This is achieved provided that the input impedance of the antenna is equal to the characteristic impedance of the line, and the latter is equal to the input impedance of the receiver or transmitter.
In practice, the input impedance of the antenna is often different from the characteristic impedance of the line. Therefore, to match the antenna with the line, it is necessary to use special matching devices. The more complex the antenna design, the more difficult it is to take into account all the factors affecting the input impedance of the antenna, and the antenna tuning must be checked using certain instruments.
In addition to voltage indicators, radio amateurs use various current indicators. Most indicators are designed for measurements in open lines. The standing wave ratio is determined by the ratio of the voltage (or current) at the antinode to the voltage (or current) at the node.
In Fig. Figure 1 shows a schematic diagram of such a bridge. The resistance values R1 and R3 are equal to each other.
If the line is matched correctly and the resistance R3 is equal to the characteristic impedance of the line, the bridge will be balanced, and the high-frequency voltmeter included in the diagonal of the bridge will show zero.
However, if the line is not matched to the load, the voltmeter reading will not be zero. The relationship between the standing wave ratio and voltmeter readings is shown in Fig. 2.
A transmitting antenna is considered good if the standing wave ratio does not exceed 2. This is explained by the fact that the decrease in power in the load with a change in the value of the load resistance does not occur sharply, and therefore some deviation from the traveling wave mode is acceptable.
A schematic diagram of a bridge for measuring the standing wave ratio is shown in Fig. 3. A view of the installation of this device is shown in Fig. 4 and 5. Resistors R1, R2 and R3 together with the characteristic impedance of the feeder form a bridge. The feeder is connected to the “Line” socket. High frequency voltage from the generator is supplied to the coaxial socket “Input”. The oscillations supplied to the bridge are rectified by a germanium diode. Constant voltage is measured using a voltmeter connected to the “+Input” and “-” sockets.
The device is mounted in a case measuring 75x50x45 mm.
Then connect a non-inductive resistance of 75 ohms to the “Line” coaxial socket. In this case, the voltmeter included in the diagonal of the bridge should show zero at all frequencies.
Figure 6 shows a schematic diagram of a bridge that allows you to directly read out the value of the measured wave resistance.
In Fig. Figure 7 shows a view of the installation of this device. The bridge is equipped with its own indicator with a sensitivity of 100 microns
As a variable resistance, a resistance of the SP type was used, from which the dill cover was removed. Since wave impedances usually range from30 to 300 ohms, in most cases you can use a resistance R3 of 680 ohms. If you need to measure higher characteristic impedance, then in series with variable resistance R3 include additional induction resistance.
When measuring at short waves. i.e. up to frequencies of 30 MHz, there is no need for shielding of resistance R3. With more high frequencies resistance P3 is shielded using a transverse partition. The resistance axis is extended using a sleeve made of insulating material.
When constructing the device, it is necessary to ensure that the connecting wires are as short as possible and have the same length as possible, so that their own capacitances and inductances are minimal and equal.
S. Khazan. "Radio" N5, 1956
The device is produced from the factory with a setting of 550 Hz. Finding the location of a ground fault using this device is carried out in the same way as using the Poisk-1 device. Thanks to the correct device, which removes the dependence of the device on the distance between the device and the line wires, the Volna device provides a clear determination of the location of a line fault with a multiple selectivity margin, even in networks with low ground fault current (1 - 1.5 A) at significant load currents up to 800 - 100 A. In addition to finding the location of a ground fault, the Volna device allows you to locate reinforced concrete supports under voltage, the location of a wire break in the network and search for other types of damage.
In some cases, a reinforced concrete support becomes energized when the insulation breaks down and a ground fault current flows for a long time through the support. With this type of damage, the soil under the support dries out, melts and becomes practically non-conductive. The support is under high voltage and can cause electrical injuries. Supports with linear disconnectors also pose a great danger in case of breakdown of the support insulators.
Determination of supports with damaged insulation and high transition resistances can be done using the “Volna” device, which monitors the value of the electric field strength in the vicinity of the support.
To determine a live support with damaged insulation, the operator must approach the support at a distance of 8 - 10 m, set the SA switch (Fig. 2.3) to the U line position and position the device perpendicular to the line axis. If the support is energized and the grounding of the support is broken or has a high contact resistance, the device readings exceed 30 - 40% of the scale. If the support is not energized, the device readings are close to zero.
To determine the location of the wire break, the operator sets the switch of the “Volna” device to the U line position and monitors the electric field at a distance of about 5 m from the line trunk at various points in the network. The instrument readings beyond the break point increase sharply (15–20 times) compared to the readings before the break point.
The “Volna” device also allows you to determine which of the network wires with a symmetrical arrangement of wires on a support has a ground fault. To do this, the operator sets the device switch to the U line position and controls the electric field at two points on both sides of the line, located symmetrically relative to the line axis at a distance of about 5 m from the line. If the instrument readings are equal, this indicates damage to the insulation of the middle phase wire; if the readings are unequal, the wire with damaged insulation is located closer to the measurement point with lower instrument readings.
Before starting to search for the location of the damage, it is necessary to check the serviceability of the device in terms of the power source. To do this, place the switch in the U power position and turn on the power to the device with the button. With a working power source, the instrument needle should be within 70 - 95% of the scale. If the instrument readings are below 70% of the scale, then the power source must be grounded.
Before starting to search for the location of the damage, it is recommended to carry out a simplified check of the functionality of the device. To do this, the switch is moved to position 1:3 and the device is brought with its end side to electric lamp incandescent with a power of 40 - 60 W. If the device is working properly, the needle should deviate by 30–60% of the scale near a lamp with a power of 40–60 W and a voltage of 220 V. When the switch is moved to position U lim, the needle of the device should deviate by 10–20% of the scale.
If during such a check there are no needle deviations or differ significantly from those indicated above, then the device should be sent to the laboratory to eliminate the malfunction. Laboratory testing and troubleshooting are carried out in accordance with the recommendations of the factory instructions.
Data from power systems indicate the high efficiency of using the Poisk-1 and Volna devices, which is determined primarily by the ability to find the location of a fault without sequentially disconnecting the line and branches and, therefore, without undersupplying electricity to consumers. At the same time, labor costs for finding the location of damage are significantly reduced by reducing search time and reducing the number of people involved in the search.