Section 1 General Rules

Norms of acceptance tests. Power cable lines

Encyclopedia of radio electronics and electrical engineering / Rules for the installation of electrical installations (PUE)

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1.8.40. 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 the rectified current.

The test voltage is taken in accordance with Table. 1.8.39.

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 leakage current value, or if it increases or the current is unstable, the test should be carried out until a defect is identified, but not more than 15 minutes.

When laying mixed cables, take the lowest test voltage according to table as the test voltage for the entire cable line. 1.8.39.

4. Test with alternating current frequency 50 Hz.

This test is allowed for cable lines for voltages of 110-500 kV instead of the rectified voltage test.

The test is carried out with voltage (1,00-1,73) Unom. It is allowed to carry out tests by connecting the cable line to the rated voltage Unom. 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 mm2 cross-section, 1 m length and temperature +20 ºС, 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 capacity of the conductors.

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 protections 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/dm2;
• 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 covers;
• 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. Characterization 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 Table. 1.8.41 and 1.8.42.

If the values ​​of electrical strength and degree of degassing of MN-4 oil comply with the standards, and the values ​​of tg δ, measured according to the GOST 6581-75 method, exceed those indicated in the table. 1.8.42, the oil sample is additionally kept at a temperature of 100 ºС for 2 hours, periodically measuring tg δ. When the tg δ value decreases, the oil sample is kept at a temperature of 100 ºС until a steady value is obtained, which is taken as the control value.

12. Measurement of ground resistance.

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.

Table 1.8.39. Rectified current test voltage for power cables

* Rectified voltage tests of single-core cables with plastic insulation without armor (screens) laid in air are not carried out.

Table 1.8.40. Leakage currents and asymmetry factors for power cables

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 *

* Tests of oils not listed in the table. 1.8.41, produce 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 cables with voltage, kV

* The numerator indicates the value for S-220 grade oils, the denominator for MN-3, MN-4 and PMS.

See other articles Section Rules for the installation of electrical installations (PUE).

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