abstract

In order to ensure the safe and reliable operation of the electrical equipment of offshore oil platforms, it is necessary to carry out handover tests on the electrical equipment of newly-built platforms.

The electrical equipment on the platform should be tested periodically. Specific operation methods, surface measurement standards and

Precautions.

Keywords: offshore oil engineering; Insulation defects; withstand voltage test

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1 all L.

17 1 1 tone

The measurement of DC resistance of transformer winding is an important test item in transformer test. It can check the wires inside the winding.

Welding quality, welding quality of lead and winding, whether the specifications of lead for winding meet the design requirements, tap changer, lead and bushing.

Whether the constant load fluid contact is good, whether the three-phase resistance is balanced, etc.

Ac withstand voltage test is not applicable to power cable insulation test, but DC withstand voltage test is applicable. High-voltage electrical equipment generally uses alternating current.

The current withstand voltage test measures the withstand voltage strength of its main insulation, but the power cable is often limited by the capacity of the test equipment because of its large capacitance.

Limit, it is difficult to carry out power frequency AC withstand voltage test. In addition, AC withstand voltage test may produce free discharge in the cavity of oil-paper insulated cable.

And damage the cable. The damage of the same high AC voltage to the cable insulation strength is much greater than that of DC voltage. Therefore, the DC withstand voltage test becomes a test.

Common methods of cable insulation performance.

2 handover test safety operation procedures

(l) Electrical testers must be qualified for post operation. Large-scale test should be equipped with enough test personnel, and it is forbidden to operate alone.

Work.

(2) Electrical testers must strictly abide by the electrical test standard procedures and conduct electrical handover test work instructions according to the corresponding voltage levels.

Test the test procedures formulated in the book.

(3) Before using electrical test instruments and equipment, read the instructions carefully, and testers should fully understand the tested equipment and the tests used.

To test the performance of equipment, instruments and meters, it is forbidden to use defective testing equipment that may endanger personal safety.

(4) The electrical test site shall meet the safety conditions of test personnel and test equipment.

(5) Electricians should strictly abide by the relevant provisions of temporary electricity utilization, and the power switch should have leakage protection performance and be adequate.

Capacity.

(6) When using electrical test equipment, the shell must be grounded, and the grounding wire must be multi-stranded soft copper wire with a cross section of not less than 4InznZ. receive

Grounding must be good and reliable, and the grounding wire shall not be connected to the irregular grounding body.

(7) The metal shell of the tested equipment should be reliably grounded, and the pressurized lead should be firm and as short as possible.

(8) Temporary barriers or warning ropes should be set up in the field high-voltage test area and at the ends of various parts of the subjects, and signs should be hung and designed.

People should be warned. Testers and alert personnel are not allowed to leave their posts without authorization to prevent outsiders from straying into the barrier and contacting with high voltage.

(9) During the high-pressure test, there must be a guardian to supervise the operation. If communication equipment is needed, ensure communication.

(10) The boosting speed of the withstand voltage test is 3kV/s; After the withstand voltage test, the test voltage should be reduced to zero before disconnecting the power supply.

(1 1) All the high-voltage equipment in use, if the ground wire or high-voltage short wire has been removed, is considered to have voltage, and the human body is not allowed to approach.

(12) The high-voltage electrode of the high-voltage test equipment should be grounded with a grounding rod before the test, and the tested equipment should be grounded and charged after the withstand voltage test.

Separate emissions.

(13) Electrical equipment with large capacity, such as power cables and power capacitors, should be fully discharged with a grounding rod with resistance after the test.

And then directly grounding or short-circuit discharging. Before the high-voltage test of large-capacity electrical equipment such as power cables and power capacitors that have been put into operation

Should be fully discharged first, and then wiring and testing.

(14) When measuring the insulation resistance with a megger, the device under test should be disconnected from the power supply, and human contact should be prevented during the test. After the test,

Must be completely discharged.

(15) If any abnormality is found in the test, immediately reduce the voltage to zero, then disconnect the power supply and discharge to ground.

Conduct an inspection. Don't continue the test until the reason is found out.

(16) During the ratio test, secondary open circuit of current transformer and secondary short circuit of voltage transformer should be avoided to avoid personal injury.

Physical or equipment accident.

(17) Outdoor high-voltage test should be stopped in thunderstorm and windy weather.

Three testing methods

3. 1 Power transformer and power cable withstand voltage test standard

(1) AC withstand voltage test standard for power transformers and reactors (kv):

The duration after AC withstand voltage test of electrical equipment is added to the test standard voltage. Unless otherwise specified, it shall be lmin. Electrical equipment

Prepare AC withstand voltage test, and the test voltage and duration shall meet the owner's specifications.

(2) The DC resistance of measuring winding and bushing of power transformer shall meet the following requirements:

(1) Measurement shall be made at all positions of each tap.

② For a three-phase transformer with a capacity level of ② 1600kvA or below, the measured phase difference should be less than 4% of the average value, and the measured value between lines.

The mutual difference of should be less than 2% of the average; For three-phase transformers with 1600kvA or more, the difference between the measured values of each phase should be less than the average value.

2%; The difference between the measured values between lines should be less than l% of the average value.

(3) Compared with the factory measured data of the product at the same temperature, the corresponding change of DC resistance of the transformer should not be greater than 2%; Current at different temperatures

The resistance value is converted according to the following formula.

T+tZ

RZ=RIX

—in the formula of t+TL, the resistance (q) when Rl and R2 are t 1 and t2(℃) respectively; T is the calculation constant, and the copper conductor takes 235.

The aluminum conductor is 225.

(4) Due to the transformer structure and other reasons, when the difference exceeds the second paragraph of this article, the comparison can only be made according to the third paragraph of this article. But we should explain the original text.

Because.

(3) Test environmental conditions:

(1) the test environment temperature is not lower than 5℃; Relative humidity is not higher than 80%.

② There is no cross construction, vibration, strong current and magnetic field interference in the test area.

(3) During the high-voltage test, there should be no factors that cause danger to others in the test area.

④ The fluctuation range of power supply voltage is less than 5%; The distortion rate of power supply voltage shall not exceed 5%. Test the difference between power supply frequency and rated frequency.

Should be within l% of the rated frequency.

(4) Preparation before the test:

(1) make test technical scheme, technical disclosure.

(2) Arrange the test site, and there must be a test wiring diagram for normal test and special test.

(3) After the test wiring is completed, a second person shall recheck it according to the drawing to ensure the wiring is correct.

(4) Check whether the working power supply and grounding are reliable before the test.

(5) Impact closing test:

Under the rated voltage, the transformer shall be subjected to five impulse closing tests, and each interval shall be smin, without abnormality.

The closing test shall be conducted on the high voltage side of the transformer; For power system with neutral grounding, the neutral point of transformer must be

When the transformer without operating disconnection point is connected in the middle of generator-transformer group, there is no need to carry out impact closing test.

(6) Check the phase:

Check that the phase of the transformer must be consistent with that of the power grid.

(7) 18kV/30kV and below, the DC withstand voltage test voltage of rubber-plastic insulated cables shall be calculated according to the following formula:

Ut ii 4XUo

Rated cable voltage uo/u;

U is the rated line voltage of the cable;

U rated voltage of cable conductor to ground or to metal shield;

Ut is DC withstand voltage test voltage.

① DC withstand voltage test procedure:

During the test, the test voltage can be stepped up evenly in 4~6 stages, and the leakage current value can be read at each stage. Check electricity

Hold15min after reaching the specified value, and read the leakage current at lmin and15min. If the leakage current decreases after intelligent minimization,

If the test is qualified, otherwise it is considered that the cable cannot meet the requirements. The influence of stray current should be eliminated during measurement.

For cables with rated voltage of 0.6/IkV, use 1000v or 25O0v megohmmeter to measure the insulation resistance of the conductor to the ground instead of the straight type.

Stress test.

According to the process requirements, the insulation resistance of the outer sheath and inner lining of rubber-plastic cable should be measured, and the insulation resistance per kilometer should not be less than.

MQ .

② AC withstand voltage test shall meet the following requirements:

Rubber-plastic cable had better be subjected to AC withstand voltage test of 20 ~ 3OOHz. Test procedure Test wiring is as follows.

Brie test equipment, connecting all components, each equipment should have a little grounding.

Check whether the power supply is in the off position and whether the voltage adjustment should be zero.

Check the overvoltage setting switch and set it to 1.05- 1. 1 times the test voltage.

Turn on the power switch.

Press the Set key to select and adjust the parameter setting, press the adjust key to set it, and press the Enter key after setting.

Tune and press the high pressure pass button.

Table 1 voltage and schedule of rubber-plastic cable ZOHz-300Hz AC withstand voltage test

Rated voltage Uo/kv

18/30 and below

2 1/35~64/ 1 10

Test voltage /Kv

2.5Uo (or 2Uo)

Time/minute

5 (or 60)

2UO

(8) The test items of suspension insulator and post insulator shall include measuring insulation resistance and AC withstand voltage test.

(1) insulation resistance value shall meet the following requirements:

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The insulation resistance of suspended insulators for voltage classes of 330 kV and below should not be less than 300 megohms; Used for SOOkv

The grade of suspension insulator shall not be less than 100 m. .

The post insulator with voltage level below 35kv shall not be lower than SOOMQ.

When measuring the insulation resistance of insulators with a 2500V megohmmeter, it can be spot-checked according to 10% of the same batch of products.

This test is not applicable to rod insulators.

The insulation resistance of semiconductor glazed insulator meets the requirements of product technical conditions.

② AC withstand voltage test shall meet the following requirements:

The post insulators with the voltage level of 35kv and below can be installed together after the bus, and the test voltage should meet the requirements.

The provisions of the.