Work on electrical equipment, except for a small number of people who are charged during the operation of the equipment, generally must be carried out under the state of equipment power outage. Pilot holdings are also required for power outage equipment, such as electricity inspection, grounding wire and other technologies to ensure personal safety. measure. Conduct electrical tests on power-off electrical equipment, especially high-voltage electrical tests. In addition to cutting off all possible power sources of the equipment, the test power supply must also be used to pressurize the equipment under test so that the equipment generates high voltage to achieve the purpose of the test. . Because the wiring of the tested equipment must be frequently disconnected before and after the pressure; the equipment with larger capacitance or the equipment under test with electrostatic induction must be discharged or grounded after the test; the pressure of the tested equipment is generally several times higher than the operating voltage , And the test auxiliary power cables are mostly exposed to prevent high-voltage electric shock accidents during the test, and to ensure the safety of testers and related workers. The following main safety precautions should be observed for high-voltage electrical test work:
1. The test personnel must be competent for the work, and the test personnel shall not be less than two, and there shall be a person in charge of the test to formulate and implement safety measures.
High-voltage test personnel must be clear about the test purpose, method (including familiarity with the performance of the test instrument, use method, etc.) and safety measures to be taken. Before work, the person in charge shall arrange the safety precautions of the test work in detail by all test personnel. The live test shall formulate safety measures according to the site conditions. Important special tests, research tests and tests in the operating system must have test plans and It can be carried out only after the approval of the relevant leaders. In this way, the test work can be carried out safely under the conditions of organization, leadership, safety measures, and people at all levels. Failure to do so, especially if safety measures are not implemented, will lead to accidents.
For example, when a technician in the electrical laboratory of a power supply station is doing the dielectric loss angle test of the switch, he mixes the test wiring in use with the unused wire, and also pressurizes and cleans it, so that the touch has been pressurized to 3,000 On the tip of the volt wire, he was electrocuted.
2. Pilot holdings explained in detail to clarify the scope of work, to clearly separate the tested equipment from other equipment, and to monitor the equipment for high-voltage electrical test work when the equipment was powered off. The work ticket system should be implemented, and the work permit procedures should be performed with the operating personnel to clarify The scope of power outage work, and in accordance with the provisions of the electrical parts of power plants and substations in the “Electrical Safety Work Regulations”, fences or fences shall be installed at the test site, and the signboard of “Stop! High Voltage Danger” shall be hung on the fences and monitored by someone. . When the two ends of the tested device are not in the same place, the other end should also be guarded. The purpose is to avoid misunderstanding the scope of power outages. However, in the accidents that occurred, some did not set up barriers or fences, did not set up guardians, and some were at the end of the fence played a role. An example is as follows: A high-voltage test group in a substation conducts a 35 kV 312 switching medium loss angle test. Since the work fence cannot distinguish between power outages and live equipment, a tester was unsupervised when he stepped off the switch and then switched on again. Without clarifying the equipment under test, he accidentally boarded the 312 switch that was in operation, and died of electrocution.
3. Explain in detail, adhere to the system of rechecking the wiring before the test
In the test work, the wiring is disconnected frequently, and the system of rechecking the wiring before the test is carefully implemented to correct the wrong wiring in advance and avoid accidents due to the wrong wiring. Therefore, rechecking the connection before the test is a basic system for test work, and it is also an effective measure to prevent electric shock accidents during test work and ensure personal safety. This system requires careful implementation and persistence. It should be treated to lower-level workers. , The connection re-examination of trainees should be focused, and senior workers or simple connection cannot be relaxed, otherwise the purpose of re-examination and connection cannot be achieved.
For example, a power plant uses a 100-kV high-pressure test machine in a high-voltage test room to perform a pressure test of a 6-kV porcelain bottle. Before the test, the connection line of the booster was not checked in detail, and the connection of the porcelain bottle under test was connected. When the pressure reached 42 kV, it was discovered that there was a plastic wire connected to the porcelain bottle at the high voltage outlet of the booster, which reached 110 thousand. In the substation, about 50 meters, the test was immediately stopped and the line was dismantled. This line was originally left after the 110 kV switch was tested more than ten days ago, and it was tied to the substation structure. There were more than ten construction workers working near the structure. Fortunately, these workers were not close when the pressure was applied. Or touch the wire.
4. During the test work, you should stand on an insulating mat or wear insulating shoes. This is a safety measure to prevent electric shock accidents or reduce the degree of injury
For example, when a test worker in a repairing plant of a power supply bureau checked the MД-16 bridge, he only turned off the bridge switch and did not open the power switch. When the bridge was turned over, his right hand touched the live part of the power end of the bridge , Due to the grounding of the electric bridge, the staff put an insulating pad under their feet, and they were separated from the power supply, only causing electric shock and burns from the energized loop from the ring finger of the right hand to the palm of the left hand.
5. Before the pressure test, the relevant personnel must be notified to leave the tested equipment or exit the site before proceeding.
High-voltage electrical test work is often carried out at the same time as other maintenance teams. Or it can be done right away, so before pressurization, these work teams must be notified to leave the tested equipment or exit the site, so that the tested equipment can be carried out in an unmanned state to achieve the purpose of ensuring the safety of personnel. These practices cannot be ignored, otherwise they will cause serious consequences.
For example, during the overhaul and test work of a transformer in a substation, the staff of the relevant team was notified before and after the transformer pressurization test, so that a maintenance worker thought that the equipment had no electricity and got on the transformer twice to work. This worker was just pressurized When I climbed the transformer again, I was fortunate to be found, avoiding electric shock.
6. The equipment under test with capacitance or electrical induction must be fully discharged or grounded before and after the test
The tested large-capacitance equipment such as: busbars, overhead cables, capacitors, etc. and equipment with electrostatic induction must be fully discharged or grounded after the high-voltage DC test is completed to prove that the tested equipment is indeed charge-free before it can work. Due to the high residual voltage or induced voltage of these devices, insulating rods must be used when discharging, which can also prevent accidental contact with live devices in operation. Some units did not pay attention to discharge or grounding, resulting in electric shock accidents.
For example, a technician in the high-voltage laboratory of a power plant conducts a 5-minute DC withstand voltage test of a 6-kV cable. The order of the numbers at both ends of the 5 adjacent cables to be tested is actually reversed, leaving hidden dangers. For example, one end is numbered 1 and the other end is 5, which has not been noticed. At the beginning, the test of a cable was completed. After disconnecting the test power supply, before discharging, the cable is not the tested cable from the serial number, but it is actually just after the test. The residual voltage is 25 kV on the cable head, so that it is left behind. The charge is electrocuted.
7. Pulling and closing of the pressure test work must be in response to each other, and the password must be correctly communicated
The pulling and closing operations of the pressure test work are more frequent. If you rely on subjective judgment or just look at the meter without listening to the password, or do not respond to each other and correctly communicate the password, an electric shock may occur.
For example, when the test team of a repairing plant of a power supply bureau conducts a transformer no-load test, the operator of the test power supply thinks that the line has been connected, and does not notify the switcher on the equipment, that is, close the test gate. When the switcher finds that the wiring is loose, Electric shock when disconnecting the wiring.
8. When the pressure test is reversed, the voltage regulator must be retracted to the zero position and the test power switch can be opened.
When the pressure test is working normally, when the wiring is switched, the voltage regulator must be adjusted to the zero position and the test power supply must be cut off. However, after searching for problems after the pressure, it is found that the wiring is not strong or the wrong wiring and the test power supply has a master switch. When there are split gates, some testers ignore them and cause accidents.
For example, when a power supply bureau’s substation construction team was doing an AC withstand voltage test of a substation booster switch, it found that the test data was problematic. In the process of finding the cause, the booster was not adjusted to the zero position, and the test power supply was not cut off. . When it was discovered that the polarity of the booster was incorrectly connected, the tester was about to change the polarity. The tester touched the live part pressurized to 50 kV. Fortunately, he got out of the power supply and only burned his hands without serious consequences.