Checking the operation of 1000 V circuit breakers. Checking circuit breakers. Loading and testing of machines. Checking the operation of circuit breaker releases

Circuit breaker- This is an overcurrent and overcurrent cut-off device that protects the electrical installation when a short circuit occurs, or during a long-term increase in overload current on the line and in the circuit of the device.

About short circuit(another name: short circuit or short circuit) a lot has been said and written, but it is worth writing separately about the reasons causing short circuit. The fact is that the state of insulation of electrical appliances and electrical installation wiring directly affects the likelihood of a short circuit. The insulation, in turn, is subject to thermal influence from the outside; to put it simply, the insulation is destroyed when heated to a certain temperature, and when overheated, it simply melts, destroying the protective barrier between the current conductors and the electrical installation. Sub-zero temperatures also lead to destruction of the insulation of conductors and equipment.

Thus, the overload current of conductors in an electrical installation leads to the gradual destruction of insulation and the occurrence of a short circuit that can cause a fire.

The main difference between a circuit breaker and a conventional switch is that the former has, together or separately, active cut-off elements, which the second one does not have:

• instantaneous cut-off (or electromagnetic release), operates almost instantly (t≤0.1 s) when an overcurrent/shock current of the upper cut-off factor appears (for example, with a cut-off of 3*Inom≤Icut-off≤5*Inom, instantaneous operation will occur at a factor of 5* In);
• thermal cut-off (or thermal release), the faster the overload current, the greater the overload current;

Maximum value overload current cut-offs is 2.55*Inominal. That is, for a device with Inom = 16A, the setting will work at I =16*2.55=40.8A.

Thermal cut-off begins to work only at a current value of 1.13*In; before this value, this type of protection (set) does not operate!

When the current increases to 1.45*In, thermal cutoff will operate when:

• for Inom≤63A – 1 hour.
• for Inom>63A – 2 hours.

Instantaneous cut-off (electromagnetic), for most cases, corresponds to the designation B*/C*/D* In:

B* – time-current dependence with current cutoff rating 3*Inom≤Icutoff≤5*Inom.
C* – time-current dependence with current cutoff rating 5*Inom≤Icutoff≤10*Inom.
D* – time-current dependence with a nominal current cutoff of 10*Inom≤Icutoff≤20*Inom.

Moreover, at a lower multiple of the electromagnetic cutoff, the response time will differ from the minimum (t≤0.1 s):

B*lower current multiplicity = 3*In:

• for Inom≤32A – 0.1s
• for Inom>32A – 0.1s

C*lower current factor = 5*Inom.

• for Inom≤32A – 0.1s
• for Inom>32A – 0.1s

D*lower current multiplicity = 10*Inom.

• for Inom≤32A – 0.1s
• for Inom>32A – 0.1s

For example, for the device rating D20, the current cut-off is in the range from 200-400A, while at a value of Icut-off=400A it will work almost instantly (t≤0.1 s); with Icutoff value = 200A, it will work in 4 seconds.

Below is for devices with thermal and instantaneous cut-off B/C/D:

Testing or loading cut-off devices for overcurrent and overload current (automatic machines) is carried out using a device (or), which allows you to create a cut-off current of 50-6,000A and load current cut-off devices with Inom = 25-400A.

Loading single-pole circuit breaker C16

To test instantaneous cutoff, the loading device creates a pulse short circuit in the circuit of the current cutoff device being tested, as a result of which it should operate. If it does not work or works too quickly, such a current cut-off device is rejected.

For check thermal cut-off the loading device creates a long-term short circuit at a maximum cutoff of 2.55*Inominal. The device operates in the following time:

• for Inom≤35A – 1-60 sec.
• for Inom>35A – 1-120 sec.

If the disconnection of the current cut-off device circuit did not occur within the specified time frame or occurred faster than 1 s, such a device is rejected.

The following are tested (PUE):

• all sectional current cut-off devices;
• all input current cut-off devices;
• all current cut-off devices for emergency lighting circuits;
• all fire alarm current cut-off devices;
• ≥2% of current cut-off devices of distribution and group networks.

Automatic circuit breakers are used to protect AC distribution networks and electrical receivers in emergency cases when the insulation is damaged. To carry out protective functions, automatic circuit breakers have maximum releases against overload currents and short circuit currents. When more than rated current passes through the circuit breaker, it should turn off. Overload protection is provided by thermal or electronic devices. Protection against short circuit currents is carried out by electromagnetic or electronic releases.

The measured value is the shutdown time of the circuit breaker at a given current value exceeding the rated current value of the circuit breaker.
The time-current characteristic (trip characteristic) of the circuit breaker is checked in accordance with the requirements of GOST R 50345-99 according to Table 1.

Table 1. Standard time-current characteristics of circuit breakers

When conducting tests, the following conditions are observed:

The circuit breaker is installed vertically;
- the circuit breaker under test is disconnected from the network;
- tests of the circuit breaker are carried out at a network frequency of (50±5) Hz;
Performing tripping tests on circuit breaker releases
Assemble a diagram for checking the operation of the circuit breaker releases in accordance with the instructions of the manufacturer of the load device used. The electromagnetic release operates without a time delay. The combined release must operate with an inverse current time delay during overload and without a time delay during short circuits. The current settings of the releases do not regulate.

Each pole of the machine has its own thermal element, which acts on the common release of the machine. To ensure the correct operation of all thermal elements, it is necessary to check each of them separately.

When testing a large number of machines simultaneously, testing thermal elements based on the initial operating current is impractical, because It takes several hours to check each machine. In this regard, it is recommended to test thermal elements with a test current equal to two and three times the rated current of the release while simultaneously loading all poles of the circuit breakers with test current.
If the thermal element does not work, then the machine is not suitable for operation and is not subject to further testing.

All thermal elements must have their thermal characteristics checked by simultaneously loading all poles of the machine with test current. To do this, all poles of the machine are connected in series. When testing electromagnetic releases that do not have thermal elements, the machine is turned on manually and the test current value is set at which the machine turns off. After turning off the machine, the current is reduced to zero and the electromagnetic elements in the remaining poles of the machine are checked in the indicated order.

The response time of the machine is determined by the stopwatch scale of the testing equipment. The time-current response characteristics of the circuit breaker releases must correspond to the calibrations and passport data of the manufacturer. Checking the operation of electromagnetic and thermal releases of automatic circuit breakers in the amount of 30%, of which 15% of the apartments most remote from the ASU. If 10% of the tested circuit breakers fail to operate, the operation of all 100% of the circuit breakers is checked.

Monitoring the accuracy of measurement results when testing circuit breakers
Monitoring the accuracy of measurement results is ensured by annual verification of instruments used for testing circuit breakers in the bodies of the State Standards Committee of the Russian Federation. Devices must have valid state verification certificates. Carrying out measurements with a device whose verification period has expired is not allowed.

Registration of test results of circuit breakers

The test results are documented in the protocol “Testing circuit breakers with voltages up to 1000V”.

Requirements for personnel qualifications when testing circuit breakers

Persons who have undergone special training and certification with an assignment of at least III when working in electrical installations up to 1000 V, who have a record of admission to tests and measurements in electrical installations up to 1000 V, are allowed to carry out measurements.
The operation of the circuit breaker is checked only by qualified personnel in a team of at least 2 people. The work foreman must have a 5th category, team members must have at least a 4th category.

Ensuring safety when testing circuit breakers

When checking the functionality of circuit breakers, it is necessary to be guided by the requirements of the Interindustry Rules for Labor Protection (Safety Rules) for the Operation of Electrical Installations.

Tests of circuit breakers can only be carried out with the electrical installation switched off. Tests must be carried out by order of a team of at least 2 people. Connection and disconnection of the test set and load ends must be done with the test voltage removed.

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When checking and testing circuit breakers, perform the following: external inspection; measuring insulation resistance and testing it with increased power frequency voltage; checking the functionality of circuit breakers at rated, low and high operating current voltages; checking the operation of maximum, minimum or independent releases of automatic circuit breakers with a rated current of 200 A or more.
During an external inspection, the installed circuit breakers are checked for compliance with the design or network parameters; absence of external damage and presence of seals on the blocks of semiconductor releases; reliability of contact connections; correct adjustment of the contact system and smooth operation of the drive when manually turning on and off the circuit breaker.
External inspection can be started only after carefully studying the operating instructions for these switches.
The insulation resistance is checked with a 1000 V megohmmeter between the terminals of the poles and between the terminals of each pole and the grounded metal structure of the machine in the off position with the voltage removed. It must be at least 0.5 MOhm. If the insulation is unsatisfactory, it is necessary to find out the reasons: remove the arc chutes and check the condition of the poles, the absence of contamination and connections to the external switching poles, the possibility of moistening the circuit breaker plate. After eliminating the cause of the reduced resistance of its insulation, the measurement is repeated. When installing arc chutes on the switch poles after removing them, pay attention to ensure that the main and arcing contacts do not touch the internal parts of the arc chutes. The insulation resistance of the windings of the drives of the maximum, minimum and independent releases is checked with a 1000 V megohmmeter between one of the winding terminals and the grounded housing. It must be at least 0.5 MOhm (for new switches of the Electron series - 20 MOhm). Before starting the measurement, the blocks of semiconductor releases are removed from the switch (Electron, A3700, VA53-41) and the insulation resistance of each of them is checked with a 500 V megohmmeter, connecting all the terminals of the connectors to each other. After testing the switch with increased voltage, the blocks are installed in place.
The operability and reliability of switching on and off switches by an electric drive at rated, low and high voltages is checked before monitoring the operation of the overload releases. In practice, when checking the operability of the drive in such a way, it is necessary to adjust it, during which the operation of the electromagnetic overcurrent releases is disrupted (for automatic machines of the ABM, A-3700 series). Therefore, setting the overcurrent protection is performed at the final stage of commissioning. The functionality and reliability of turning on and off is checked by applying a voltage equal to the rated voltage (1.1 and 0.85 (Lum)) to the drive circuit of the switch. At the same time, the mechanisms for turning on and off the switch are checked and, if necessary, adjusted (the number of on and off operations for each voltage value is at least five with intervals between them of at least 5 s), and also control the performance and reliability of independent and minimum releases at rated, low and high voltages of the operating current in the network.
Maximum releases for circuit breakers with rated currents of 200 A or more must be checked. However, in operation there are installations in which it is necessary to check the operation of such releases with lower rated currents (for example, switches of control, protection and alarm circuits at substations where AP50 switches are installed for currents of 10-50 A. Operation of thermal, electromagnetic or combined releases of series switches AZ 100, A3700 with an electromagnetic release, AE20, AK50, AK63, AE25, AE26, AE1000, VA51, VA52 and AP50 are checked in each pole of the switch. The thermal elements are checked during adjustment work with a load current equal to three times the rated current of the release. The operating time is compared. with factory (or standard) characteristics, taking into account that they are given for the case of simultaneous load of test current on all poles of the circuit breaker. If the actual operation time exceeds the manufacturer’s data by 50%, it is necessary to check the initial operation current before rejecting the circuit breaker. load of one pole of the circuit breaker, the initial operation current increases by 25-30% compared to the same current when all poles are loaded simultaneously. The response time of the thermal release must correspond to the factory specifications. Moreover, most switches have a limited test time under current (no more than 120-150 s).
When testing electromagnetic releases without thermal elements, a test current is supplied to each pole, the value of which is set 15-30% below the set current. In this case, the switch should not turn off. Then the test current is raised to the operating current, the value of which should not exceed the set current value by more than 15-30%.
When testing the electromagnetic elements of combined releases, the load current from the testing device is applied to each pole of the circuit breaker. By quickly increasing the current to a value 15-30% below the set current, make sure that the release does not trip. Then the current is quickly increased to the tripping current, fixing its value. It should not differ from the factory data. When checking the electromagnetic elements of combined releases, it should be remembered that between applications of test current to the pole there must be an interval sufficient for cooling of the thermal element. To make sure that the shutdown occurred from the electromagnetic element of the release, you must immediately turn it on after each tripping of the switch. If the switch turns on normally, the shutdown occurred from the electromagnetic element. When the thermal element is triggered, the switch will not turn on again. Of all the previously indicated series of switches, only the AP50 series switches have a lever on the free-release mechanism for adjusting the setting to 0.6 of the rated current value, the remaining sets of releases are adjusted to the setting at the manufacturer.
Adjustment of the operating currents of maximum releases of circuit breakers equipped with semiconductor elements is complicated by the fact that with a large number of elements that make up the semiconductor release, the number of possible operational failures increases. Therefore, when starting to adjust the current settings and response times of such releases, you should make sure that the BURI semiconductor unit and the tripping electromagnet are operational. For this purpose, special devices (attachments) are manufactured, with the help of which this check is performed. Thus, to check the functionality of the semiconductor release of the A3700 series circuit breaker, a device is used, the diagram of which is shown in Fig. 26.
In a switch prepared for adjustment, the functionality of the independent release, which is the output element of the semiconductor unit, is first checked. When voltage is applied from terminals A1 - A2 to the terminal of connector X of the semiconductor block, the independent release should operate and the switch should turn off.

Fig. 26 Electrical diagram of the RP control device

If this does not happen, mechanical adjustment of the release is necessary. Then, depending on the type of current being tested, terminals A1, A2, A3 of the AC or DC release are connected to sockets 1, 2, 3 of the semiconductor block of the BURP. Switch S3 is set to the Nominal position and the switch being tested is turned on. Power is supplied to the device circuit. The release must not operate in any fixed position of the adjustment knobs.
Set switch S3 to the Overload position. The circuit breaker must turn off with a delay of no more than 800 s. In this way, the performance of the unit in the overload zone is checked. Then set switch S3 to the Nominal position, turn on the switch and press button S2. The circuit breaker must turn off within a period of no more than 1 s. In this way, the operability of the unit is checked in the area of ​​short circuit currents. Next, you can proceed to checking or, if necessary, adjusting the currents and operation times of the switch.
QF - circuit breaker, X.S0 socket, TAI - TAZ current transformers, FUI - fuse, RA! ammeter, NI - light signaling device, UD - rectifier


Fig. 27 Simplified circuit for checking the operation of overcurrent protection with secondary current
V/ For the “Electron” series switches, a method has been developed not only for checking functionality, but also for setting the current settings and response time of RMT-1 semiconductor units with secondary current. This is done using an attachment for checking overcurrent protection with secondary current, the circuit diagram of which is shown in Fig. 27. This figure also shows the connection diagram of the set-top box to the “Electron” series switch, as well as the power supplies of the circuit.

Fig. 28 Front panel of the RMT-1 release I - control sockets, 2-5 - scales

The attachment is inserted into the connector between the switch and the RMT unit. When checking the calibration of rated currents on the front panel of the unit, the /« knob (Fig. 28) is set to the setting of 0.8, the S6In, !пх and S knobs are in the middle position. Connect an indicator (DC voltmeter with a limit of 25-30 V) to the sockets on the front panel of the RMT. Switch blocks S1 and S2 of the RMT block are set to positions 6 and II, respectively.
Turn on the “Electron” switch. Supply power to the circuit and, using an autotransformer, gradually increase the current in circuit PA1 (see Fig. 27), while simultaneously monitoring the indicator arrow. From the moment the supply voltage is applied, the indicator reading should be 17-21 V. At a certain current value equal to the secondary operating current at the setting being checked, the indicator reading will abruptly decrease to 0-3 V. The readings of the PAI ammeter at the moment the unit operates should not differ by more than ± 10% of the secondary current value for the circuit breaker setting being tested. In the same way, check the operation of the RMT unit at other settings. Checking the functionality of semiconductor blocks of switches of the BA53-41 series is similar to checking the Electron switch
The final check of the operation of the maximum current protection of the A3700, VA53-41 and Electron series circuit breakers is carried out using the primary current from the load device. To do this, the corresponding regulators are installed in the calculated position on the front panel of the semiconductor blocks. A load device is connected to one of the phases of the main circuit of the switch, with the help of which the current in the main circuit is increased until the switch is turned off. The current value and response time must not differ from the calibration value for the setting being tested by more than ±15%. Next, by analogy, the operation of the maximum current protection is checked by passing current through the remaining phases or poles of the switch. At the end of the checks, the semiconductor blocks are covered with protective glass and sealed. The results of the checks are recorded in the protocol.
To load switches with primary current, load devices UBKR-1, UBKR-2, NT-10, RNU6-12, TON-7 and lр are used.
When checking and adjusting the settings of DC switches, load transformers with both single-phase and three-phase rectifiers or DC generators for a current of up to 10 kA at an open circuit voltage of 6-12 V are used.
The adjustment of switches ends with checking their operation according to the full circuit (at a substation there may be an automatic transfer circuit, or sometimes a motor control circuit), the interaction of all elements of the circuit and the correct inclusion of measuring instruments. The test is carried out at nominal and 0.8 Un operating current voltage. Using a constant scheme, the phasing of the supplied voltage (phase rotation), the readings of voltmeters and ammeters (after connecting the load) are checked.
The final conclusion about the quality of adjustment work and the suitability of the switches for operation is made after they are put into operation at full load. Moreover, if one electric motor is powered from the switch, it is enough to make several starts (this is especially necessary for fan drives whose start-up takes a long time). If the switch does not turn off during start-up, then the protection settings are set correctly. If several pantographs are powered from the switch, the most unfavorable operating mode should be created, for example, starting the most powerful motor while the remaining pantographs are running under load.

1. Introduction

These guidelines define the procedure for checking the operation of circuit breaker releases in overload and short circuit modes in order to assess the quality of the circuit breakers and compare them with the standards of PUE clauses 1.7.79, 1.8.34; SNiP 3.06.06-85, section 4 and manufacturer’s data. The technique was carried out based on the requirements of GOST R 50571.16- 2007 and PUE and is required for use by specialists electrical laboratories in Krasnodar and Krasnodar region Energy Alliance LLC.

2. General provisions

2.1 Measurement of insulation characteristics is carried out in accordance with the guidelines for measuring insulation resistance.

2.2 The volumes and timing of various types of tests, acceptable values ​​of the characteristics of the equipment being tested are established on the basis of RD 34.45-51.300-97 and approved multi-year schedules.

2.3 Knowledge of these guidelines is mandatory for the following employees of the Insulation and Testing and Measurement Service: chief, engineer, electrician for testing and measurement.

3. Test method for circuit breakers

3.1 The measured value is the shutdown time of the circuit breaker (AB) at a given current value exceeding the rated value.

3.2 Testing the performance of circuit breakers is carried out by loading them with primary current by creating an artificial short circuit with an adjustable current value in the circuit of the circuit breaker being tested and measuring the shutdown time.

3.3 To carry out protective functions, AVs have maximum releases against overload currents and short circuit currents. Overload protection is provided by thermal or electronic devices. Protection against short circuit currents is carried out by electromagnetic or electronic releases.

3.4 Before measuring the shutdown time, check:

· compliance of the types and parameters of the AV with the design or passport for the electrical installation;

· compliance of current setting AB with the design;

· no visible damage to the AB,

· reliability of tightening of AB contact clamps;

· measurement of insulation characteristics;

· measuring the DC resistance of switch contacts.

3.5 Before measuring the timing characteristics, it is necessary to remove the voltage from all parts of the tested AV and take measures to prevent the supply of voltage to the place of work due to erroneous or spontaneous switching on of the switching equipment. Check that there is no voltage on live parts. Live parts that remain energized must be fenced; warning and instructional posters must be posted on the fences.

3.6 Measurement of the characteristics of a single-phase AV is carried out according to the diagram in Fig. 1.

The AB release being tested is connected to a loading transformer in the circuit of which a current transformer TA1 with a connected ammeter is installed. The second current transformer TA2 is connected to the current relay RT, the contacts of which break the stopwatch circuit. The primary winding of the loading transformer is connected to a 220V network through a control transformer. By changing the voltage on the control transformer, the current is set corresponding to the current setting of this type of AB release. At short circuit current and overload, the release must turn off. The AV response time is determined on the stopwatch scale.

3.7 Measurement of the characteristics of a three-phase AV is carried out according to the diagram in Fig. 2.

The AB release being tested is connected to a loading transformer in the circuit of which a current transformer TA1 with a connected ammeter is installed. The primary winding of the loading transformer is connected to a 220V network through a control transformer. By changing the voltage on the control transformer, the current corresponding to the current setting of this type of AB release is set.

The response time of the AB is determined on the scale of a stopwatch, the switch of which is the free contact AB.

3.8 When checking the characteristics of thermal and electromagnetic releases of automatic circuit breakers, a complete testing device “Saturn-M” or “Saturn-M1” and a load transformer NT-12 with a range of 30-12000 A are used.

3.9 Work with a device of the “Saturn-M” type must be carried out in accordance with the “Technical Description and Operating Instructions” for this device.

3.10 When checking the characteristics of circuit breakers, other sets of equipment can be used that correspond to the specified current and voltage of the circuit breaker being tested and with an accuracy class of at least 0.5

4. Condition assessment based on measurement results

4.1 Tests of circuit breakers are carried out in accordance with the requirements of GOST R 50345-92 by checking the time - current characteristics.

4.2 When checking the thermal release, the non-trip current AB is passed through all poles. In this case, the circuit breaker should not trip. Then, within 5 seconds, the current gradually increases to the value of the conditional tripping current. The circuit breaker must trip within the specified time. The current and time values ​​are given in Table 1.

4.3 When testing AB from a “cold” state, a current equal to 2.55 In is passed through all poles. The opening time must be at least 1 s. and no more than: 60 s. at rated currents up to 32 A inclusive, and 120 s. at rated currents above 32 A.

4.4 When checking the instantaneous release of type “B” circuit breakers, a current equal to 3 In is passed through all poles for a period of at least 0.1 s. AB should not disengage. A current of 5 In is then passed through all poles and the circuit breaker must trip in less than 0.1 s.

4.5 When checking the instantaneous release of type “C” circuit breakers, a current equal to 5 In is passed through all poles for a period of at least 0.1 s. AB should not disengage. A current of 10 In is then passed through all poles and the circuit breaker must trip in less than 0.1 s.

4.6 When checking the instantaneous release of type “D” circuit breakers, a current equal to 10 In is passed through all poles for a period of at least 0.1 s. AB should not disengage. A current of 50 In is then passed through all poles and the circuit breaker should trip in less than 0.1 s.

Table 1.

5. Test error calculation

The absolute error in measuring the shutdown time when measured by the Saturn device does not exceed(0.01xTism + 0.01) seconds.

6. Safety and environmental precautions

6.1 Electrical personnel trained and certified in knowledge of POTEE and measurement techniques, at least 18 years old, provided with tools, personal protective equipment, and special clothing, are allowed to work on checking the operation of AVs.

6.2 Before work, organizational and technical measures must be drawn up.

6.3 Measurements are carried out by order or along with a team of 2 people with an electrical safety group of at least 3.

6.4 Portable devices and equipment must be grounded. Grounding can be performed by direct connection to a grounding device or through the grounding bus of a mobile laboratory with a flexible copper wire with a cross-section of at least 4 mm2.

6.5 Work on connecting devices to the measurement object should be carried out by disconnecting the electrical receiver from the network. If this is not possible, then you should connect the device wearing dielectric gloves, safety glasses, and standing on a dielectric carpet.

7. Registration of measurement results

Based on the results of the inspection electrical laboratory in Krasnodar Energo Alliance LLC draws up a protocol and issues it to the customer within the prescribed period.

After replacing or re-installing electrical wiring, it is necessary to install metering devices and all automatic devices for the normal operation of household appliances and to ensure uninterrupted operation of all types of connected equipment. The installed equipment must be checked for operation or, as it is commonly called, loaded. In this article we will take a closer look at how circuit breakers with voltages up to 1000 V are tested.

Briefly about circuit breakers

Automatic switches are designed to act as switching devices necessary to conduct load current during normal operation of the equipment and open the electrical circuit in emergency mode at high or low voltage.

AVs are widely used due to their ease of installation, reliability in operation, safety during replacement and maintenance, speed of response in case of short circuit currents or abnormal conditions. Such machines are installed in electrical installations with both low and high power.

There are devices with manual and remote control. In abnormal conditions, the switch operates automatically. All devices are equipped with an overcurrent release. Some models are equipped, in addition to the maximum, with a minimum current release. Such circuit breakers are designed to replace switches or fuses in plug fuses, which provides more reliable protection for household appliances and connected equipment.

ABs are produced mainly for amperages from 6.3A to 6300A for alternating current installations up to 1 kV, with a different number of poles. These can be one-, two-, three- and four-pole circuit breakers.

You can find out more about it in our related article. Now I would like to additionally tell you that protection against abnormal conditions is provided by an electromagnetic release, thanks to which the device is turned off.

There are two types of releases:

• electromagnetic or maximum release against short-circuit and overload currents (without time delay);
• thermal (electronic), triggered at currents significantly exceeding the rated values ​​of load currents (with a time delay).

Both types of protection must comply with the manufacturer's regulatory documents (PTEEP in Appendix 3). In order for the device to work properly, it must be checked before use. This operation is called loading the machine, which we will now discuss in more detail.

Loading method

During loading, the main characteristics of the machines are measured (rated current, protection response current, protection response time under abnormal conditions) on a special installation. All work on testing the functionality is carried out by special personnel who have access to such tests, with a certificate with a mark of admission to special work on testing electrical equipment.

The certificate must indicate the safety group and the voltage at which the employee can conduct tests (up to or above 1000V). The certificate must be signed by the chief power engineer of the enterprise that carries out the verification work. The method of loading AV in the factory must comply with GOST for low-voltage control and distribution equipment.

Equipment

In order to test (load) a circuit breaker, you need to assemble a fairly simple circuit that includes the equipment necessary for testing:

• connecting wires;
• KU - control key;
• LATR - laboratory autotransformer, for changing the load;
  load transformer or load transformer (LT);
• ammeter as a shunt;
• CT - current transformer.

Diagram of the device for checking AB:

The loading method requires partial dismantling of the device, and after checking its serviceability, reassembling it. The test device can be of a different type, the main thing is that an artificial short circuit current is supplied to the AV, its value is measured, and the response time of the circuit breaker protection in the electrical network is taken into account.

There are even special kits for checking AB, for example SINUS-1600, shown in the photo:

The process itself

Loading of a circuit breaker with an electromagnetic release is carried out to determine the time within the protected zone according to factory specifications. To do this, the load current is set on the testing device, which is equal to the maximum amperage for a given type of AB and time, according to the factory specifications.

To test the thermal release, the test installation is set to three times the load current and the maximum trip time, according to the factory specifications. Usually this time is from 5 seconds. up to 0.5 min.

All steps to check the machine are discussed in detail in the video:

How to load an AV with primary current

Tests at home

All results of the work carried out are recorded in the protocol. The document reflects the magnitude of the induced amperage and the response time of the machine. The loading protocol is signed by the person conducting the tests. A sample of filling out the inspection protocol is provided below:

Test dates

The frequency of testing should be specified in the accompanying regulatory documents of the manufacturer, but the recommended test is once every three years during normal operation of the circuit breaker at the rated load current. In case of emergency operations or abnormal operation of the AV, the frequency may be changed, and an unscheduled inspection should be carried out. All recommendations apply to household circuit breakers and switches installed in industrial premises.

According to the PUE, Chapter 3.2, clause 1.8.37, the loading of circuit breakers on input and sectional protection devices, emergency lighting networks, fire alarms is 2% of AV group networks. PUE requirements for other electrical installations 1% of all installed circuit breakers.

If circuit breakers are detected that do not meet factory specifications, a test procedure is carried out for the entire batch. After loading, each device must be stamped with the logo of the laboratory conducting the test, the date of the test, and the word “Tested” or “Best before ... (date).” This indicates that the machine has been tested and is suitable for use.

This is the method used to test circuit breakers with voltages up to 1000 V. As you can see, you can load a machine even with a device assembled at home, the main thing is to know the safety precautions and testing technology. We hope that now you know what and how to do in order to independently check the breaking capacity of the protection device.