Repair process for medium voltage circuit breakers containing SF6 . gas

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1 year ago

Repair process for medium voltage circuit breakers containing SF6 . gas

Contents

1 I.Main workload
2 II.Preparation and construction measures
- 2.1 II.1 Preparation
- 2.2 II.2 Construction methods
3 III. SAFETY MEASURES
4 IV. ENVIRONMENTAL PROTECTION WORK
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In power generation, transmission and distribution, at any stage, from production, transmission and distribution, medium voltage circuit breakers from 6 kV to 42 kV are indispensable. For example, with a hydroelectric turbine, the generator will generate a current with a voltage of 6-36 kV, with a very large current, from here using a terminal breaker to introduce a transformer, raising the current to 110 kV ( 123Kv) or 220 kv (245 kV). Terminal circuit breaker is also a special medium voltage circuit breaker, called GCB (generator circuit breaker).
After the current is raised to the grid from 110K -220 kV- 500 kV (123 kv-245Kv -550 kV), then it is transmitted (transmission) and then it is lowered to the grid or consumers from the grid. 110Kv – 22 KV (popular in Vietnam) today.

When going to large factories, or a residential area, people often build 110 kV substations to distribute to 22 kV highways, at these stations, there is a modern electrical switchboard system including, protection, distribution, fault reporting, here also contains medium voltage circuit breakers to bring out the roads and bring electricity to consumption.

These medium voltage lines (mainly 22 kV (24 kv) in Vietnam at present) are used to install loops for modern power stations with 3 basic components: breaker (containing SF6 gas), transformer, low voltage distribution cabinets, of course there are some other elements in medium voltage cabinets (MV – Medium voltage) such as TU, TI monitoring and measuring.

Thus, the above has presented the importance of medium voltage circuit breakers using SF6 gas, depending on the needs of use with high or low current, the structure of the circuit breaker (electrical cabinet) will be different. , in other articles, ABB Asia Co., Ltd. will analyze more so that users can understand better.

Here we will present the basic steps of the SF6 . gas-containing medium voltage circuit breaker repair procedure.

I.Main workload

Use a dedicated SF6 gas leaker to re-leak the entire circuit breaker.
Identify leak locations and mark them again
Unplug the power cord at the Circuit Breaker, remove each part of each phase SF6 gas leak circuit breaker according to the device’s instructions.
Welding, Changing gaskets, grease maintenance
Reinstall the circuit breaker and re-detect the gas in the whole circuit breaker, meet the requirement of no leakage
Testing the switching mode of circuit breakers that are eligible for live operation.
Complete gas leakage treatment of the experimental unit, equipment and vehicles out of the power station.

II.Preparation and construction measures

II.1 Preparation

a/ Prepare the ground before construction

Must be completed at least 1 day before construction.
Clean, prepare the ground around the construction area and the roads to the location, arrange the working area
Prepare to gather equipment so that it is convenient and safe during construction, easy to manage and transport.
Check construction quality.

b/ Prepare equipment, tools and supplies:

Prepare equipment, replacement parts, installation diagram of machinery and equipment at the construction site.

c/ Allocation of construction personnel:

Consists of 1 working group
Assign specific tasks to each member and group to do the work

d/ Tools and construction equipment:

Transportation
Truck carrying equipment
Means of com

No	Category	Unit	Quantity
1	Máy nén khí	Máy	1
2	Máy hàn tig, kèm bình Argon	Máy	1
3	Máy hút chân không	Máy	2
4	Máy nạp khí SF6	Máy	3
5	Máy rò (ngửi) khí Sf6	Máy	3
6	Dụng cụ (tool set) (đủ bộ)	Bộ	1
7	Roăng, mỡ	Hộp	3
8	Hệ thống máy, thiết bị thí nghiệm	Bộ	1
9	Khí SF6	Bình	1
10	Máy hút bụi	Cái	1

II.2 Construction methods

1/ Checking procedure before SF6 . gas leak

Bring the equipment to the scene, use the fence of the construction area
Install the equipment in the surveyed location, test the machine and equipment
Arrange working tables, tool cabinets
Check the lighting system
Check uniforms, protection, hats (attach lights) if night construction is required

2/ Procedure for checking leak point

Fill Sf6 gas to the level according to the manufacturer’s regulations
Conduct leakage of all points on the circuit breaker
Mark leak locations

3/ Process of detecting detection points

Remove the entire body shell
Check the oring, Bushing, terminal, compartment…
Thoroughly handle leakage points
Reinstall the system
MC . vacuum
Refill SF6 gas, soak, re-detect treated points and gas leak points

5/ Done

Remove equipment, remove from the scene

III. SAFETY MEASURES

When the construction needs to cut off the power, the construction unit will directly contact the investor and the power management board to take safety measures and deliver the grid for construction.
All construction sites have signs
The construction unit has a registration form for direct commanders, safety supervisors, and working workers.
Check that the ground is closed.
Finishing work on the day the construction team leader conducts the final inspection to ensure the safety of energizing.
It is strictly forbidden for workers to drink alcohol or use other stimulants during working hours.
All workers participating in the construction must be trained in electrical and occupational safety.
All employees participating in the construction of the project are fully equipped with tools and labor protection equipment such as:
- Protective clothing
- Protective plastic caps
- Safety shoes

IV. ENVIRONMENTAL PROTECTION WORK

1. Installation work

After construction, the site must be redone around the construction site as it was in its original state. During construction, it is necessary to pay close attention to protect the equipment around the entire construction work, clean it, and at the end of the day check the construction tools carefully to clean up to avoid loss. and cause accidents to people.
The power sources used in construction must be safe for everyone, strictly comply with the regulations on order, safety and industrial hygiene of the area.

2. Maintain hygiene

The transportation of tools for work must comply with the regulations of the factory management board.

3. Protection of technical infrastructure works

During the construction process, the contractor absolutely does not adversely affect the existing technical infrastructure system.

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North Vietnam