Power cable lines
Power cable lines with voltage up to 1 kV are tested according to paragraphs 1, 2, 7, 13, with voltages above 1 kV and up to 35 kV - according to paragraphs 1-3, 6, 7, 11, 13, with voltages of 110 kV and above - in to the full extent provided for in this paragraph.
1. Checking the integrity and phasing of the cable cores. The integrity and coincidence of the phase designations of the connected cable cores are checked.
2. Insulation resistance measurement. Produced with a megohmmeter for a voltage of 2.5 kV. For power cables up to 1 kV, the insulation resistance must be at least 0.5 MOhm. For power cables above 1 kV, the insulation resistance is not standardized. The measurement should be made before and after testing the cable with increased voltage.
3. Test with increased voltage of rectified current.
The test voltage is taken in accordance with Table 1.8.39.
Table 1.8.39 Rectified current test voltage for power cables
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* Rectified voltage tests of single-core cables with plastic insulation without armor (screens) laid in air are not carried out.
For cables for voltages up to 35 kV with paper and plastic insulation, the duration of application of the full test voltage is 10 minutes.
For rubber-insulated cables with a voltage of 3-10 kV, the duration of application of the full test voltage is 5 minutes. Cables with rubber insulation for voltages up to 1 kV are not subjected to high voltage tests.
For cables with a voltage of 110-500 kV, the duration of application of the full test voltage is 15 minutes.
Permissible leakage currents depending on the test voltage and permissible values of the asymmetry coefficient when measuring leakage current are given in Table 1.8.40. The absolute value of the leakage current is not a rejection indicator. Cable lines with satisfactory insulation must have stable leakage current values. During the test, the leakage current should decrease. If there is no decrease in the value of the leakage current, as well as if it increases or the current is unstable, the test should be carried out until the defect is identified, but not more than 15 minutes.
Table 1.8.40 Leakage currents and asymmetry coefficients for power cables
| Cables voltage, kV | Test voltage, kV | Permissible values of leakage currents, mA | Acceptable values of the asymmetry coefficient () |
| 6 | 36 | 0.2 | 8 |
| 10 | 60 | 0.5 | 8 |
| 20 | 100 | 1.5 | 10 |
| 35 | 175 | 2.5 | 10 |
| 110 | 285 | Not standardized | Not standardized |
| 150 | 347 | Same | Same |
| 220 | 610 | " | " |
| 330 | 670 | " | " |
| 500 | 865 | " | " |
When laying mixed cables, take the lowest test voltage according to Table 1.8.39 as the test voltage for the entire cable line.
4. Voltage test alternating current frequency 50 Hz.
This test is allowed for cable lines for voltage 110-500 kV instead of rectified voltage testing.
The test is carried out with voltage (1.00-1.73). It is allowed to carry out tests by switching on the cable line to the rated voltage. The duration of the test is according to the manufacturer's instructions.
5. Determination of the active resistance of the cores. Produced for lines 20 kV and above. The active resistance of the cable line conductors to direct current, reduced to 1 mm cross-section, 1 m length and temperature +20 ° C, should be no more than 0.0179 Ohm for a copper conductor and no more than 0.0294 Ohm for an aluminum conductor. The measured resistance (reduced to specific value) may differ from the specified values by no more than 5%.
6. Determination of the electrical working capacitance of the cores.
Produced for lines 20 kV and above. The measured capacity should not differ from the factory test results by more than 5%.
7. Checking protection against stray currents.
The operation of the installed cathodic protection is checked.
8. Test for the presence of undissolved air (impregnation test).
Produced for oil-filled cable lines 110-500 kV. The content of undissolved air in the oil should be no more than 0.1%.
9. Testing of feeding units and automatic heating of end couplings.
Produced for oil-filled cable lines 110-500 kV.
10. Checking anti-corrosion protection.
When accepting lines into operation and during operation, the operation of anti-corrosion protection is checked for:
Cables with a metal sheath laid in soils with medium and low corrosive activity (soil resistivity above 20 Ohm/m), with an average daily leakage current density into the ground above 0.15 mA/dm;
Cables with a metal sheath laid in soils with high corrosive activity (soil resistivity less than 20 Ohm/m) at any average daily current density into the ground;
Cables with an unprotected sheath and destroyed armor and protective coverings;
Steel pipeline of high pressure cables, regardless of the aggressiveness of the soil and types of insulating coatings.
During the test, potentials and currents in the cable sheaths and electrical protection parameters (current and voltage of the cathode station, drainage current) are measured in accordance with the guidelines for the electrochemical protection of underground energy structures from corrosion.
The assessment of the corrosive activity of soils and natural waters should be carried out in accordance with the requirements of GOST 9.602-89.
11. Determination of characteristics of oil and insulating liquid.
The determination is made for all elements of oil-filled cable lines for a voltage of 110-500 kV and for end joints (inputs into transformers and switchgear) of plastic-insulated cables for a voltage of 110 kV.
Samples of oils of grades S-220, MN-3 and MN-4 and insulating liquid of grade PMS must meet the requirements of the standards of tables 1.8.41 and 1.8.42.
Table 1.8.41 Standards for quality indicators of oils of grades S-220, MN-3 and MN-4 and insulating liquid of grade PMS
Note. Test oils not listed in Table 1.8.39 in accordance with the manufacturer's requirements.
Table 1.8.42 Tangent of the dielectric loss angle of oil and insulating liquid (at 100,%, no more, for voltage cables, kV)
| 110 | 150-220 | 330-500 |
| 0,5/0,8* | 0,5/0,8* | 0,5/- |
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* The numerator indicates the value for S-220 grade oils, the denominator - for MN-3, MN-4 and PMS
If the values of electrical strength and degree of degassing of MN-4 oil meet the standards, and the values of tg δ, measured according to the GOST 6581-75 method, exceed those indicated in Table 1.8.42, the oil sample is additionally kept at a temperature of 100 ° C for 2 hours, periodically measuring. When the tg δ value decreases, the oil sample is kept at a temperature of 100 °C until a steady value is obtained, which is taken as the control value.
12. Ground resistance measurement.
Produced on lines of all voltages for terminations, and on lines 110-500 kV, in addition, for metal structures of cable wells and make-up points.
Oil-filled transformers power up to 630 kVA are tested according to paragraphs 1, 2 (insulation resistance only), 11-14.
Oil-filled transformers with a power of up to 1.6 MVA are tested according to paragraphs 1, 2, 4, 9, 11-14.
Oil-filled transformers with a capacity of more than 1.6 MVA, as well as transformers for the auxiliary needs of power plants, regardless of power, are tested to the full extent provided for in this paragraph.
Dry and filled with non-flammable liquid dielectric transformers of all capacities are tested according to paragraphs 1-7, 12, 14.
1. Determination of the conditions for turning on transformers.
Should be produced in accordance with the manufacturer's instructions.
2. Measurement of insulation characteristics.
For transformers with voltages up to 35 kV inclusive, with a power of up to 10 MVA and arc suppression reactors, the insulation resistance of the windings must be not lower than the following values:
The insulation resistance of dry transformers at a temperature of 20-30 ºС should be for windings with rated voltage:
Up to 1 kV inclusive - at least 100 MOhm;
More than 1 kV to 6 kV - at least 300 MOhm;
More than 6 kV - at least 500 MOhm.
For other transformers, the insulation resistance, normalized to the measurement temperature at the manufacturer, must be at least 50% of the original value.
The values of the dielectric loss tangent (tg δ), reduced to the measurement temperature at the manufacturer, should not differ from the original values in the direction of deterioration by more than 50%.
Measurement of insulation resistance and tg δ must be carried out at a winding temperature not lower than:
10 ºС - for transformers with voltage up to 150 kV;
20 ºС - for transformers with voltage 220-750 kV.
Measuring tg δ of transformers with power up to 1600 kVA is not necessary.
Measurement of the insulation resistance of accessible tie rods, bandages, half-bandages with yokes and pressing rings relative to active steel and electrostatic screens, relative to windings and magnetic circuits is carried out in case of inspection of the active part. The measured values must be at least 2 MΩ and the yoke insulation must be at least 0.5 MΩ. Measurements are made with a megohmmeter for a voltage of 1000 V.
3. Power frequency high voltage test:
a) insulation of windings together with inputs. Test voltages are given in table. 1.8.12. The duration of application of the normalized test voltage is 1 min.
Testing the windings of oil-filled transformers with increased voltage at industrial frequency is not necessary.
Testing the insulation of dry transformer windings with increased voltage at industrial frequency is mandatory and is carried out according to the standards of Table. 1.8.12 for devices with lightweight insulation.
Imported transformers are allowed to be tested with the voltages indicated in table. 1.8.12, only in cases where they do not exceed the voltage with which this transformer was tested at the factory.
The test voltage of grounding reactors for voltages up to 35 kV is similar to those given for transformers of the corresponding class;
b) insulating accessible tie rods, compression rings and yokes. The test should be carried out in case of inspection of the active part. Test voltage 1 kV. The duration of application of the normalized test voltage is 1 min.
4. Measurement of winding resistance to direct current.
Produced on all branches. The resistance should differ by no more than 2% from the resistance obtained on the same branch of other phases, or from the manufacturer's data.
The resistance value of the windings of single-phase transformers after temperature recalculation should not differ by more than 5% from the original values.
5. Checking the transformation ratio.
Produced at all switching stages. The transformation ratio should differ by no more than 2% from the values obtained on the same branch in other phases, or from the manufacturer’s data. For transformers with on-load tap-changer, the difference between the transformation ratios should not exceed the value of the regulation stage.
6. Checking the connection group of three-phase transformers and the polarity of the terminals of single-phase transformers.
This is done if passport data is missing or there are doubts about the reliability of this data. The group of connections must correspond to the passport data and designations on the shield.
7. Measuring no-load losses.
Measurements are made for transformers with a power of 1000 kVA or more at a voltage supplied to the low voltage winding equal to that specified in the factory test report (passport), but not more than 380 V. For three-phase transformers, no-load losses are measured with single-phase excitation according to the circuits used at the manufacturer's factory.
For three-phase transformers, upon commissioning, the ratio of losses in different phases should not differ from the ratios given in the factory test report (passport) by more than 5%.
For single-phase transformers, upon commissioning, the difference between the measured loss values and the original ones should not exceed 10%.
7.1. Measurement of short circuit resistance (Z k) of a transformer.
The measurement is carried out on transformers of 125 MB·A and more.
For transformers with a voltage regulation device under load, Z k is measured on the main and both extreme branches.
The values of Z k should not exceed the value determined by the short-circuit voltage (u k) of the transformer on the main branch by more than 5%.
8. Checking the operation of the switching device.
Manufactured in accordance with the manufacturer's instructions.
9. Testing the tank with radiators.
All transformers are tested, except those that are sealed and do not have an expander. The test is carried out:
For transformers with voltages up to 35 kV inclusive - hydraulic pressure of the oil column, the height of which above the level of the filled conservator is 0.6 m, with the exception of transformers with wavy tanks and plate radiators, for which the height of the oil column is assumed to be 0.3 m;
For transformers with film oil protection - by creating an excess air pressure of 10 kPa inside the flexible shell;
For other transformers - by creating an excess pressure of nitrogen or dry air of 10 kPa in the above-oil space of the expander.
The duration of the test in all cases is at least 3 hours. The oil temperature in the tank when testing transformers with voltages up to 150 kV inclusive is not lower than 10 ºС, for others - not lower than 20 ºС.
A transformer is considered oil-tight if inspection after testing does not reveal any oil leakage.
Electrical devices and secondary circuits of protection, control, signaling and measurement circuits are tested to the extent provided for in this paragraph. Electrical wiring with voltage up to 1 kV from distribution points to power receivers is tested according to clause 1.
1. Insulation resistance measurement.
2. Power frequency high voltage test.
Test voltage for secondary circuits of protection, control, signaling and measurement circuits with all connecting devices (circuit breakers, magnetic starters, contactors, relays, devices, etc.) 1 kV. The duration of application of the normalized test voltage is 1 min.
3. Checking the action circuit breakers.
3.1.
Checking the insulation resistance. Produced for switches with a rated current of 400 A or more. The insulation resistance value is at least 1 MOhm.
3.2.
In other electrical installations, all input and section switches, switches for emergency lighting, fire alarm and automatic fire extinguishing circuits, as well as at least 1% of other switches are tested.
The check is carried out in accordance with the manufacturer's instructions. If switches are identified that do not meet the established requirements, twice the number of switches is additionally checked.
4. Checking the operation of circuit breakers and contactors at reduced and rated voltages operational current.
The value of the response voltage and the number of operations when testing circuit breakers and contactors by repeated switching on and off are given in table. 1.8.35.
5. Residual current devices (RCDs), residual current switches (RCBs) are checked in accordance with the manufacturer’s instructions.
6. Checking relay equipment. Testing of protection relays, controls, automation and alarms and other devices is carried out in accordance with current instructions. The relay operation limits at operating settings must correspond to the calculated data.
7. Checking the correct functioning of fully assembled circuits when different meanings operational current.
All elements of the circuits must function reliably in the sequence specified by the design at the operating current values given in table. 1.8.36.
Table 1.8.34
Acceptable insulation resistance values
|
Test element |
Megger voltage, V |
Lowest permissible value of insulation resistance, MOhm |
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1. DC buses on control panels and switchgears (with disconnected circuits) |
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3. Control, protection, automation and measurement circuits, as well as excitation circuits of DC machines connected to power circuits |
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4. Secondary circuits and elements when powered from a separate source or through an isolation transformer, designed for an operating voltage of 60 V and below |
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1) The measurement is carried out with all connected devices (drive coils, contactors, starters, circuit breakers, relays, instruments, secondary windings of current and voltage transformers, etc.).
2) Measures must be taken to prevent damage to devices, especially microelectronic and semiconductor components.
3) Insulation resistance is measured between each wire and ground, and between every two wires.
4) The insulation resistance of each section of the switchgear is measured.
Table 1.8.35
Testing of contactors and circuit breakers by repeated switching on and off