chapter xi electrical operation and maintenance...of ac 50hz, rated working voltage 380v, and rated...

Ant Training Academy Mining Farm O&M Teaching Materials

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Chapter XI Electrical Operation and Maintenance

I. Qualifications for an Electrician

Education background

College degree and above

Professional requirements

Electricity-related majors, holding a high-voltage or low-voltage electrician certificate (special operation electrician)

Work experience More than 3 years of related working experiences

Skills Have high maintenance electrician professional knowledge; have the management and maintenance capabilities of substation and power distribution facilities, and be familiar with safety and operation specifications

Personal quality 1. Serious and rigorous working attitude 2. Loyal, honest and trustworthy 3. Strong sense of responsibility and hard work

II. Mining Farm Electrical System and Equipment

1. Mining Farm Electrical System

The power supply of the mining farm must serve the miner well, ensure the needs of the miner, network and daily life, and do a good job of energy conservation. It must meet the following basic requirements:

(1) Safety: In the supply, distribution and use of electrical energy, no personal accidents or equipment accidents should occur.

(2) Reliability: It should meet the requirements of the power supply reliability of the

Electrician certificate


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miner. With the operation of the large hashrate miners, the reliability requirements for the power supply have changed.

(3) High quality: It should meet the quality requirements of the miner for voltage and frequency, etc.

(4) Economical: The investment in the power supply system should be small, and the operating costs should be low.

In addition, in the power supply work, it's necessary to reasonably deal with local and global relations, current and long-term relations. It's required to not only take care of local current interests, but also have a global perspective, thus taking into account the overall situation and adapting to development.

The power supply and distribution system of the mining farm is composed of a general step-down transformer substation (high-voltage power distribution station), a high-voltage power distribution line, a workshop substation, a low-voltage power distribution line, and electrical equipment. The following introduces several different types of power supply and distribution systems:

(1) General Substation

The general substation is responsible for converting the external power supply voltage of 220 ～ 110kV into the 35 ～ 10kV high-voltage distribution voltage of the factory area to supply power to the substations and transformers of the factory buildings.

(2) Power plant substation

The substation of the workshop reduces the voltage of 35-10kV to 380 / 220V, and then supplies power to the miners through low-voltage power distribution lines.

(3) Distribution lines

The power distribution lines are divided into high-voltage power distribution lines in the factory area and low-voltage power distribution lines in the workshop.


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Main wiring diagram of mining farm power supply: high-voltage part

Main wiring diagram of mining farm power supply: low voltage part

2. Mining Farm Power Supply Equipment

2.1 Transformer

Transformer is a kind of stationary electrical equipment. It adopts the principle of electromagnetic induction to increase or decrease the AC input voltage to an AC output voltage of the same frequency. Classification by insulation: oil-immersed type and dry type. At present, the voltage level of the dry-type transformer is only 35kV, and the capacity is smaller than that of the oil transformer, which is about

Circuit PT Circuit lightning

arrester

Isolating switch QF

Circuit breaker QF

Grounding switch

Busbar

Surge protective device SPD

Low-voltage

chamber

Busbar PT


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2500kVA.

2.2 High-tension Switch Board

The high-voltage switchgear is composed of vacuum circuit breakers, relay protection equipment, relay protection devices, grounding switches, voltage transformers, current transformers, live displays, secondary instruments and secondary control circuits.

2.3 Outdoor Vacuum Circuit Breaker

Outdoor vacuum circuit breaker is also commonly referred to as outdoor pole switches. It is a type of circuit breaker installed outdoors. Outdoor vacuum circuit breaker can realize short-circuit current: quick-break, over-current protection, overload, single-phase grounding, etc.

2.4 Cable

The basic structure of electric cable is composed of three parts: conductor, insulation layer and protective layer.

Conductor: transmitting current, guiding power transmission mode;

Insulation layer: withstanding voltage and insulation function;

Protective layer: protecting the cable insulation from the external environment and preventing mechanical damage.

According to the use characteristics, laying conditions and safety of various types of wires and cables, some wires and cables only have conductors without insulation and protection layers (such as bare wires), or only have conductors and insulation layer without protection layer (such as plastic wire etc.). In addition, the cable can be designed into structures such as fire resistance, fire prevention, shielding, etc. according to the requirements of use, provided that it meets the three major requirements.

Breaker chamber Busbar chamber

cable chamber

Conductor

Insulation layer

Protective layer


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2.5 Low-voltage Switchgear Cabinet

Low-voltage complete switchgear is suitable for power consumers such as power plants, power stations, industrial and mining enterprises as the power for distribution system of AC 50HZ, rated working voltage 380V, and rated working current 3150A, as well as the power conversion, distribution and control of lighting and distribution equipment.

2.6 Low-voltage Circuit Breaker

Low-voltage circuit breaker: a switching device that can switch on and off normal load current, overload current, and short-circuit current, which has automatic protection functions for voltage loss, undervoltage, overload, short circuit, and leakage.

1. Mainly including miniature circuit breakers, plastic case circuit breakers, frame circuit breakers, intelligent universal circuit breakers.

2.Releasers mainly include thermal releaser, magnetic releaser, thermal magnetic releaser, electronic releaser and electronic intelligent releaser.

3. Overload long delay protection: The thermal type (bimetallic element) protection unit is used for overload long delay protection (thermal releaser).

4. Short-circuit protection: through generating a magnetic field by the current, the magnetic force of the magnetic field moves the armature to cause the releaser to operate. It has no time-limiting features and has an instantaneous trip function.


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3. Electrical Equipment Routine Inspection

Electrical equipment is one of the most critical and important equipment to ensure the normal operation of the miner. Faulty electrical equipment will directly endanger the safe and stable operation of the mining farm power system. Therefore, the electrical equipment shall be inspected frequently, so that when abnormalities occur in electrical equipment, timely measures can be taken to prevent accidents and ensure the normal operation of the system.

In accordance with the relevant national electrical regulations and the actual situation of the equipment under the jurisdiction of each branch plant, the management system for the inspection of electrical equipment is formulated as follows:

3.1 Requirements for inspection personnel

(1) Inspection personnel must have a strong sense of responsibility, a correct attitude, careful observation and quick thinking;

(2) Study the theoretical knowledge carefully and understand the equipment structure, performance and operating parameters.

3.2 Equipment routine inspection should focus on the prevention of seasonal accidents, and should have an emphasis in different regions and seasons, such as:

(1) The focus of routine inspections from January to March: equipment contacts, oil level, gas pressure, insulators, wire sagging, fire-fighting equipment, terminal box, mechanism box sealing and heating conditions, fire prevention, anti-small animal measures, snow defense, anti-freezing, ice damage prevention and anti-pollution flashover measures.

(2) The focus of routine inspections from April to June: equipment contacts, oil level, gas pressure, lightning protection facilities, fire prevention measures and fire-fighting equipment, flood prevention equipment and measures, ventilation and cooling facilities, building and infrastructure foundation.

(3) Focus of routine inspection from July to September: equipment contacts, oil level, gas pressure, insulators, lightning protection facilities, wire sagging, terminal box, mechanism box sealing and moisture protection, fire prevention measures and fire-fighting equipment, small animal prevention measures, flood prevention equipment and measures, ventilation and cooling facilities, waterproof and anti-leakage measures, buildings, and framework foundation.

(4) Focus of routine inspection from October to December: equipment contacts, oil level, gas pressure, insulators, fire prevention measures and fire-fighting equipment,


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small animal prevention measures, thermal insulation and heating measures, snow defense, anti-freezing, ice damage prevention and anti-pollution flashover measures, etc.

3.3 Inspection methods

The gradual change process from normal equipment to the emergence of accident hazards is an accumulation process of quantitative changes. In the process, the quantitative changes of equipment are expressed by specific symptoms. By checking the equipment with “observe, listen, touch, smell, measure” methods, the user can find out these reflected symptoms in the process of quantitative change in time, deal with it before the qualitative change of the equipment accident, so as to actively prevent the qualitative change and prevent the accident from occurrence.

(1) Observe: It is mainly used to analyze and judge the inspection items of equipment such as appearance, location, temperature, pressure, color, light, signal, and indication, for examples, transformer oil level inspection, oil temperature inspection, cable temperature inspection, etc. Observe the operation condition of the equipment to determine whether it's normal, record relevant data such as temperature, pressure, number of operations, and leakage current, etc.

(2) Listen: judge whether the equipment is running normally mainly through sound. For example, the sound of the transformer is a uniform buzzing sound during normal operation, and a higher and heavy buzzing sound when running at over-rated current. By analyzing and judging whether the sound of the equipment is normal during operation, whether there are abnormal sounds, and whether there are abnormal corona sounds, discharge sounds, etc., it can be determined whether the equipment operates abnormally.

(3) Touch: Use the hand to touch the uncharged equipment case to determine whether there is any abnormality in the temperature or vibration of the equipment. For example, touch the transformer case and check whether the temperature is normal, and whether there is a significant difference from usual conditions.

(4) Smell: Check whether the equipment is overheated or abnormal by smelling. For example, judging by the sense of smell whether the smell of the device is normal, whether there is abnormal smell such as burnt smell.

(5) Measure: Through measuring, grasp the exact data. For example, according to the change of the equipment load, use an infrared thermometer to test whether the temperature of the equipment contact is abnormal, and whether it exceeds the normal temperature.

3.4 Matters needing attention


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(1) Unless special circumstances, do not change the operation mode, start or stop equipment, etc .;

(2) Report the problems discovered in time and fill in the work record form;

(3) Necessary tools must be carried during the inspection, such as: flashlight, electric pen, etc .;

(4) Wear protective equipment and keep a safe distance when conducting routine inspection for the transformer.

3.5 Inspection work content

Equipment name

No. Inspection contents

Inspection standards

Background monitor

1 Switch status

indication

The switch status is consistent with the actual operating conditions of the site, and relevant alarm information is handled in a timely manner.

2 DC screen

status Input switching status, voltage, current conditions and alarm conditions.

3 Transformer

alarm If there is any alarm information, confirm, report and deal with it in time.

4 Comprehensive

protection If there is any alarm information, confirm, report and deal with it in time.

High-voltage switch cabinet

1 Switch position The switch opening and closing indicators indicate correctly, and are consistent with the actual operating status.

2 Switch sleeve,

support porcelain bottle

Check that the sleeves and support porcelain bottle are clean and intact without damages such as breakage, cracks and corona discharge.

3 Connecting line

1. Check that the switch leads and clamps are firmly crimped, contact well, have no discoloration, and have no cracks in the copper-aluminum transition. 2. Use methods such as checking the color change of the wires and clamps, rising hot air flow, increased oxidation, melting or discoloration of the thermometer or discoloration paint, and checking for redness after turning off the lights, measuring the temperature with the temperature measuring probe. 3. In rainy and snowy weather, check the leads and clamps; check whether there is a heating phenomenon by observing if the snow melts and water vapor generates.


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4. Check the lead wire at the high place for broken strands and burns. A telescope can be used.

4 Sound of the

switch There should be no abnormal sound on the switch.

5 Secondary

1.Terminal strip is clean. 2. No loosening and discoloration of the secondary wire. 3. Cable secondary wire hole is sealed tightly. 4. Protection device indicates normally.

Disconnecting switch

1

Main contact parts such as

contacts, leads, clamps, etc.

1. Wire has no broken strand. 2. Good contact of contact terminal. 3. Observe whether the connector has hot air flow, serious discoloration, intensified oxidation, whether the thermometer has discolored and melted; check for redness after turning off the lights; check whether there is a heating phenomenon; use a temperature measuring probe to measure the temperature. 4. In rainy and snowy weather, check the equipment lead, wire clamp main current contact part, and knife switch main contact part, and observe whether there is snow melting or water vapor generating phenomenon. 5. No hanging foreign objects.

2 Strut Intact, clean, free from damage and traces of discharge.

3 Operation

mechanism

1. Anti-false locking device is intact and the locking function is reliable. 2. Mechanical interlocking device is complete and reliable. 3. The mechanism box door is closed tightly.

4 Transmission

link No bending deformation, loosening, corrosion.

5 Grounding

knife switch

Normally in the "opening" position, the booster spring has no broken strands, and the locking function is good.

Lightning arrester

1 Appearance Clean, no damage, no discharge.

2 Body 1. No tilt of body. 2. No cracks on the foundation, no loosening or corrosion of the fixing screws.

3 Discharge

counter Whether the discharge counter is intact, record the number of actions.


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4 Lightning

arrester lead The lead is intact, the contact is firm, and the clamp is free of cracks.

5 Grounding Good grounding, no corrosion of ground wire.

Transformer

1 Sound Normal sound, no noise or uneven discharge sound.

2 Temperature of upper oil layer

1. Transformer body thermometer is intact and has no damage. 2. Record the upper oil layer temperature value of the transformer. The upper oil layer temperature limit is 85 ℃, and the temperature rise limit is 55 ℃.

3 Oil level

1. The oil level indication of the transformer is normal. 2. The oil level gauge should be free from damage and oil leakage; there is no oil dirt which may affect viewing the oil level.

4 Body

1. No oil leakage at the connection between the body and the casing. 2. Sleeve is intact, no damage, clean or discharge traces. 3. The ground electrode is firmly welded without rust. 4. No silicone discoloration in the respirator.

Low voltage switch box

1 Busbar

Use a thermometer to test the equipment to detect the temperature of the busbar joints, and observe whether there is discoloration or oxidation aggravation.

2 Switch cabinet

1. No abnormality in the appearance inspection of the switch cabinet, the cabinet door is tight, the cabinet body is not inclined, and the paint is not peeled off. 2. Use a thermometer to test the switch cabinet, and check whether the temperature is normal and does not exceed 80 ° C.

3 Current

transformer No cracks, charring, melting, burn marks, smoke, or abnormal odor.

4 Instrument indicator

Indicators, meters, etc. display normally.


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4. Overhaul of Electrical Equipment

Formulate annual overhaul schedule for high-voltage switch cabinets, power transformers, low-voltage switch cabinets, power distribution boxes, overhead lines, and power cables. If high-voltage circuit breakers and transformers are inspected for defects or the insulation is too low, they shall be repaired immediately. For lightning rods, lighting arrester and other grounding devices, the grounding resistance shall be measured every spring and meet the requirements of the regulations.

4.1 Maintenance Content

1. Distribution equipment

1. Check whether the capacity of voltmeter, ammeter is consistent with the load, whether operation indicator is normal 3. Check the compensating cabinet breaker and contactor are normal

2. Check transformer and PC display parameters are normal 4. Check whether the transformer or compensating cabinet has abnormal sound or smell

II. Auxiliary facilities

1. Check the temperature and humidity meter reading is within applicable scope (temperature within ambient temperature ±2℃, humidity within ambient humidity ±10 2. Check the extinguisher (the pressure pointer is within the green scope and regular inspection is qualified), the heptachloropropane pressure is normal; 3. Check whether ventilation facility and fire alarm are normal 4. Check the small animal prevention facilities are normal

Standard Maintenance Operation Process

1. Accept the command

2. Arrange the command officer

3. Go to the site with tools

4. Inquiry and observe

5. Hang the shutdown sign

6. Three-minute KY

7. Maintenance 8. Equipment internal cleaning

9. Restore the security device 10. Tool

checking

11. Remove the shutdown sign and make trial operation

12. Quality confirmation

13. Equipment external cleaning

14. Fill maintenance record


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Routine maintenance content: regular maintenance of sanitation condition of the distribution box, cabinet room floor, wall, etc.; screw tightening of the secondary circuit; voltmeter, electricity meter, equipower meter, indicator daily maintenance; inspection and commissioning of flexible operation of various switches.

Planned maintenance contents: regular dust removal and inspection, tightening of busbars and secondary control lines; periodic inspection of cable to ground resistance and phase-to-phase insulation resistance; periodic inspection of the grounding, null bar, and goodness of grounding of each cabinet; regular inspection of transformer grounding.

4.2 Power off before maintenance

4.3 Maintenance of transformer

* Wear insulating gloves and insulating boots correctly before operating A. Power off: Lower-voltage division breaker - division-general breaker - division loop network cabinet breaker - loop closing network cabinet grounding knife switch B. Electricity testing: low-voltage general breaker front end (no electricity display) - verify the high-voltage end C. Discharge: verify the high-voltage end (no electricity display) - discharge from low voltage to high voltage D. Grounding: clamp the main cable with grounding line clip - ground phase A, B, C in order

1. Tight the connection bolts of each component 2. Remove dust and rust on the surface of each component 3. Check whether there is peroxidation phenomenon on the connection bolt of each component 4. Check tools and check whether there is omission


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5. Insulating Safety Appliances

The basic safety appliances among common high-voltage insulating safety appliances include: insulation rods, insulation clamps, high-voltage electroscopes, high-voltage clamp clip-on ammeter, etc.

Auxiliary safety appliances include: insulating gloves, tools equipped with insulating handles, insulating boots, insulating shoes, insulating platforms and insulating blankets.

The basic safety appliances among common low-voltage insulating safety appliances include: insulating gloves, tools equipped with insulating handles, low-voltage electroscopes, and so on.

Auxiliary safety appliances include: insulating tables, insulating pads, insulating boots, insulating shoes, etc.

6. Emergency Response Procedures

6.1 Emergency Response Procedures for Electric Shock

Purpose In order to prevent electric shocks at the construction site which may result in injury or death, this plan is therefore formulated.

Responsibility

1. Regularly check the grounding condition of the equipment, strengthen the maintenance and regular overhaul of the equipment, and prevent the equipment from running with failure. 2. If abnormality is found, it should be handled in a timely and correct manner. If it cannot be handled, report in time.


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Procedures

Quickly cut off the power or use an insulating item such as a wooden stick to remove the wire from the injured person. Rescue personnel are not allowed to touch the wounded directly with their hands before the electric shock person is disconnected from the power supply. If the electric shock person is at a high place, take precautions to prevent it from falling. If the injured person is unconscious, check his/her breathing and pulse. If necessary, perform artificial respiration and cardiopulmonary resuscitation until the injured person starts breathing spontaneously and the heart beats again. Call emergency center in time. Accompany the patient on the way to the hospital and monitor the changes in the condition of the injured.

6.2 Explosion and Fire of Electrical Equipment

Purpose In order to prevent injuries and equipment damage caused by explosion and fire of electrical equipment at the construction site, this plan is therefore formulated.

Responsibility

1. Implement the electrical equipment operation regulations to prevent excessive operation. 2. Regularly carry out maintenance and tests to ensure that the equipment is intact. 3. Pay attention to check the change of oil level and deal with leakage failure in time. 4. Carefully implement the operating system to prevent false operations. 5. If abnormality is found, it should be handled in a timely and correct manner.

Procedure

Cut off the power of the fire equipment and extinguish the fire. Report the fire situation to the superior and call for fire alarm (with the consent of the superior) in a timely manner. Under the premise of ensuring the safety of personnel, follow the operating procedures when the power is turned off. It is strictly prohibited to pull the knife switch with a load. When operating, wear insulating gloves, boots and use insulating equipment of corresponding voltage level. Please use carbon dioxide, carbon tetrachloride, 1211, dry powder fire extinguishers. Never use water or foam to extinguish fire. When cables and other equipment catch fire, toxic gas will be generated. Fire extinguishers should stand upwind and wear gas masks. When an oil-filled equipment (transformer) catches fire, open the oil drain valve at the bottom of the main body as soon as possible to drain oil. After the open flame of the equipment is eliminated, observe whether the equipment is completely cooled to ensure that the equipment does not have a secondary fire. In case of personal injury, call 120 in time or send to hospital for emergency.


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Clean up the accident scene in time to avoid environmental pollution caused by equipment residues.

7. Electrical Operating Risk

Involved activities, equipment and facilities

Risks Risk source Control measures

Electrical operation

False operation,

electric shock

Failure to perform two-person

maintenance operation

requirements

Perform two-person maintenance operation according to work requirements

Operator does not accept safety

education training

Safety education should be provided to the construction unit before construction,

and the construction unit should also provide construction education to the

construction personnel.

Undocumented operations

Special operation personnel must hold a certificate and ensure that the certificate is

valid Undocumented

operation (operation without operation permission file)

Personnel holding certificate conduct the operation (handling operation permission

before operating)

Failure to perform two-person

maintenance work requirements

Perform two-person maintenance operation according to work requirements

Operators does not accept safety

education training

Safety education should be provided to the construction unit before construction,

and the construction unit should also provide construction education to the

construction personnel. Undocumented

operation (operation without operation permission file)

Personnel holding certificate conduct the operation (handling operation permission

before operating)

Electric shock

Non-electrician operation

Special operation personnel must hold a certificate and ensure that the certificate is

valid


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Fail to hang corresponding

warning signs for powering on/off

Hang corresponding warning signs for powering on/off operations

Fail to hang warning sign after switching

Hang warning sign after switching

Electric shock,

personal injury

Fail to equip with qualified electrical

tools and instruments

Equip with qualified electrician tools and instruments

Fail to conduct electricity testing after closing the

switch

Conduct electricity inspection after closing the switch

Fail to go to the site to check whether there is no power

transmission obstacle

Check at the job site to confirm that there are no power transmission obstacles

Fail to equip with qualified electrical

tools and instruments

Equip with qualified electrician tools and instruments

Flash burn

Damaged or missing switch arc

extinguishing chamber

Check and replace the switch arc extinguishing chamber in time

Close (open) switch with load

It is strictly forbidden to close (open) the brake with load

Damaged or missing switch arc

extinguishing chamber

Check and replace the switch arc extinguishing chamber in time

Operation sequence is wrong during power failure

Follow the operation sequence of the job ticket during a power outage

Flash burn,

electric shock

Powering on operation sequence is

wrong

Operate in accordance with the operation sequence of the task ticket when

powering on Fail to confirm that

the inverter has stopped working, and

the switch of the higher-level

substation is turned

Confirm that the inverter has stopped working and the switch of the upper-level

substation is turned off


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off Fail to check

indicating instrument and confirm that

there is no voltage

Check the indicating instrument to confirm that there is no voltage

Equipment trouble

Fail to check the meter indication is

correct Check the meter indication is correct

Fail to check if the knife switch is in closing position

Check whether the knife switch is in closing position through the window

Rinse with water Never use water for rinsing Fail to clean up

regularly as required Clean up regularly as required

Isolation switch (knife switch) is not

in place (contact overheating)

Isolation switch (knife switch) must be in closing position. Confirm that after

closing the switch

Electrician operation

Personal injury

Fail to equip with power failure

emergency lighting facilities

Equip with power failure emergency lighting facilities, and ensure they are

complete and easy to use

Not wearing insulating shoes, insulating gloves

Wear insulating shoes and gloves before operation.

Production

interruption, electric

shock

Open the power unit cabinet door under the running state

It is strictly forbidden to open the power unit cabinet door in the running state

Stop a wrong circuit Stop the circuit according to the operation

order of the task ticket

Cleaning operation

Fire, explosion

Scrub equipment and floor with light oil

and gasoline

It is forbidden to scrub the equipment and ground with light oil and gasoline.

Mechanical injury

Clean up without hanging warning signs (sprains)

Before cleaning and maintaining the pump, stop the pump and hang a warning

sign; cleaning, maintenance and other operations on the pump that is running are

strictly prohibited.

Other injuries

Teeter while washing the windows (fall,

scratch) Concentrate and hold firm.


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Go into a narrow space for cleaning (fall, bump injury)

When working in a narrow space, you need to concentrate, pay attention to observe, operate carefully, protect yourself, and wear a full range of

protective straps to prevent injury from bruises and bumps.

High-altitude falling

No protective measures are taken

when cleaning at high places

Fasten the safety belt when working at heights; the safety belts and backup ropes in use should be hung on strong and solid components and checked for buckle. It is

forbidden to hang the safety belt on moving objects or objects with sharp

angles.

Shifting of duty

Static electricity

Incorrect protective clothing

Wear labor protection articles in accordance with regulations to prevent clothing and hair from being tangled by pumps and causing mechanical strains and static electricity in flammable and

explosive places.

Personal injury

Bumping Duty shifting inspections shall be carried

out carefully to avoid human body bumping with equipment.

chapter xi electrical operation and maintenance...of ac 50hz, rated working voltage 380v, and rated...

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