N2 CO2

H2

N2 seal

H2 pipes

CO2 pipes

Figure 264-2 An example of hydrogen replacement

Chapter 3 Electric Motor

Article 265.

(Nothing)

Article 265-a1. General

Article 264of technical regulation (operation and maintenance)requires “Appropriate measures for the motors” to prevent damage to the motors.

1.Design

(1)Starting device

In thermal power plants, three-phase squirrel-cage induction motors are widely used due to high reliability and low cost, although their starting current is large.

In the case of squirrel-cage induction motors, it is difficult to limit the starting current, which is approximately from 400 to 800% of -loadfull current, by connecting resistors in the secondary windings.

Therefore, starting device may be used in the primary circuit according to the condition.

For example, starting device may be used when voltage dips by starting current is so significant that other equipment is shut down. (Approximately 10% dips)

(2) Protection

The electric motors should be protected from overload by fuses, or circuit breakers, or thermal relays, in order to prevent burnout. Overload protection should not activate by starting current. Therefore, protection coordination between starting current and overload current should be performed.

Moreover, electric motors should be protected depending theon operating and design conditions.

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For example, if electric motors have a risk of causing hindrance or damage significantly by the open phase of the power supply, protective equipment against loss of phase (if it does not hinder, the alarm device) may be equipped in order to prevent burnout. (Recommendation)

In the case of squirrel-cage induction motors, if the motor speed is controlled,voltage of the motor should be controlled to prevent heat by over-flux. An inverter controller may be equipped with this function.

As for protection, Article 240-3 of design guideline is referred.

consumption by motors is the dominant in electric power consumption. Therefore, initial investment for high efficiency machines contributes to cost cut and environment preservation. Initial cost difference from low efficiency machines may be recovered and may be gained additional benefits depending on the operating condition.

1) High efficiency motor

Motors with long operation hours are recommended to be specified with high efficiency according to IEC 60034-30.

2) Inverter (Speed control)

In a power station, pumps, ansf etc are driven by motors. These process values may be controlled by following methods.

a.Dampers or control valves

This is a simple method; however, there is a lot of power loss.

b.Blade or vane control

Radius of moving blade or inlet guide vane is changed.

c.Speed control of motors

In the low speed range, this method by an inverter decreases electric power consumption significantly because power consumption of the load such as fans, pumps and blowers can be reduced to the value which is proportional to the cube of the motor speed, cutting power loss of dampers or control valves. When advanced control is necessary, "vector control", is used.

However, in the low speed, cooling capability of motors decreases significantly, therefore, advices from the manufacturer are recommended to be taken.

In the case of inverter installation, Article 18-1 to 18-2 of design guideline is referred.

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2.Operation

(1)Motor start

In the case of squirrel-cage induction motors, the large thermal and mechanical stress occurs

in the motors during start-up, as stipulated above. Therefore, the lifetime of the motors depends on number of continuous starts and total number of starts, significantly.

Thus, number of continuous start and total start number of starts are recommended to be controlled for the security of motors.

Moreover, electric motors of large capacity should not be started at the same time because voltage in the power station may dip significantly.

Significant voltage dip may cause failures such as troubles of control systems.

(2) Normal operation

As for monitoring items, Article 266-a1 is referred. 3. Maintenance

As for maintenance, Article 266-a1 is referred.

Article 266.

(Nothing)

Article 266-a1. Inspection of motor

The fundamental of maintenance is routine inspections in accordance with inspection list items and also supervisory which is performed in the proper period.

This supervisory period and items should be conformed to instruction manuals from the manufacturer. Table 266 shows an example of inspection items (during operation)

As for disassembly inspection, Article 173 of inspection guideline is referred.

Table 266 An example of inspection items (during operation)

Items

1Operating condition

1)Voltage, frequency

2)Load current

3)Noise

4)Vibration

5)Temperature

6)Frame, bearing

7)Coil

8)Odor

9)Ventilation condition

10)Surrounding conditions

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Items

2.Appearance.

1)Frame

2)Terminals and connection

3.Bearings.

1)Noise

2)Vibration

3)Temperature rise

4)Bearing temperature

5)Amount of oil in bearing oil tanks

4.Lubricated condition

5.Existence or nonexistence of alarms

Chapter 4 TRANSFORMER, AUTO-CONNECTED TRANSFORMER,

AND OIL REACTOR

Article 267. General provisions

For the operation of transformer and oil reactor, their stable and durable operation must be maintained by the following items.

(1)Monitoring temperature During inspection

-The present temperature shall bemonitored. It is checked whetherit is the appropriate temperature as consider present load and outside temperature. It should be managed not to exceed the maximum temperatures that are specified in manufacturer’s instructions and management unit’s operation manual.

-The present temperature shall bemonitored. It is checked whetherit is the appropriate temperature as consider present load and outside temperature. It should be managed not to exceed the maximum temperatures that are specified in manufacturer’s instructions and management unit’s operation manual.

-The maximum temperature shall be recordedduring overload operation was performed, it is checked that whether the special attention level is not exceeded.

(2)Monitoring loaded condition and voltage level

-During inspection, present load and voltage level shall be recorded, and it is checked that whether they are in the proper range.

-During operation, current and voltage of transformers shall be recorded once every 02 hours, the values must be within the limits of the manufacturer.

In addition, if the range is exceeded, warning is emitted.

(3) Examination criteria of insulating oil quality and insulation characteristics

For the quality of the transformeroil, the mineral insulating oil shall be used. Mineral oil is

the high molecular compound which is refined from crude oil and its main ingredient is

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hydrocarbon. The main characteristics of the mineral insulating oil as well as the management criterion about insulating properties of the insulation oil are shown in the following table 267- 1 and 267-2.

(4)Keep cooling facilities for cooling, voltage regulator and other facilities in good condition.

-In cooling facilities, it is checked whether there stench,is overheating, abnormal noise, vibration, oil leakage, etc. during the inspection.

-In a voltage regulator during the inspection;

+It is confirmed there is not abnormal noise when an electric motor is working,

+Record the operation frequency, and judged whether the present value is a proper value compare with the past trend.

+ Judge operation frequency synthetically by considering the past results, switching pattern, etc. The usual value of operation frequency is about 30 times per day.

+Check whether the indicator of the tap instruction device is at the regular position.

-In transformer and reactor, it is checked whether there is abnormal noise and oil leakage,

the terminal doesn't change color and generate heat, all of the cooling valve is open completely.

Table 267-1 Main characteristic of Transformer oil (Transformer)

[From ETC's manual]

Table 267-2 Main characteristic of Transformer oil (Tap changer)

Article 268. Firefighting facilities

In order that the fixed firefighting equipment operate normally inthe necessary cases, the following items shall be checked in the daily inspection.

- Check whether there is deformation or damage in the fire-extinguishing cylinder, piping, and valve.

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-Check whether there is wear or damage in the cover bolt of the fire-extinguishing cylinder, etc.

-Whether the power supply SW and the automatic and manual change areSWin the regular position

outdoor. Though rain water is exhausted by a drainage pump,it shall be stopped and prevent oil

to leak out after oil was detected. In order that the oil spill prevention equipment operates normally in the necessary cases, the items below must be inspected in the daily patrol.

-The control panel of the drainage pump shall be checked whether the current, the automatic and manual change SW and the pilot light are in regular position or state.

-In addition, the start-up test of the pump shall be done 1 time per month, and it is confirmed that it starts normally.

-The start-up test of the pump of the oildetection device shall be doneevery month, and it is confirmed that it starts operating normally.

Article 269. Numbering and signing

As stipulated in Technical Regulation.

Article 270. Power supply for cooling system

As stipulated in Technical Regulation.

Article 271. On-load tap changer

The operation frequency of the on-load tap changer shall be recorded, and judge whether the present value is the proper value compare with the past trend.

The usual operation frequencyof the transformer for power distribution is 30 times per .dayThe overall judgment is necessary in consideration of the past achievement, switching pattern, etc.

The insulation oil of on-load tap changer deteriorates due to the switching operation in the oil, so the breakdown voltage test shall be carried out periodically and eryv switching time instructed by the management unit.

The on-load tap changer must also bear the change frequency specified by the manufacturer.

Article 272. Cooling system

As stipulated in Technical Regulation.

Article 273. Forced cooling

As stipulated in Technical Regulation.

Article 274. Auxiliary Oil level

As shown in the ministerial ordinance, the amount of oil in conservator of the transformershall correspond to the oil temperature in the transformer.

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In normal operation, insulation oil in conservator of transformer shall be at the level equal to the corresponding oil temperature in transformer, which specified by the manufacturer.

If the oil leakage occurs and the oil level decreases due to something trouble, it shall be necessary to give a warning at the oil level 1 and to trip the transformer at the oil level 2. The oil level 1 and the oil level 2 should be instructed by the management unit of the transformer based on the valuespecified by the manufacturer.

Article 275. Overload of transformer

Although actual overload limit and durationof transformer shall be based on the operation manual and instructions of manufactureras shown in thetechnical regulation, the overload operation of transformer, the current and temperature limitations, provided in IEC are shown in the following table for reference.

(Reference) [source: IEC60076-7 Loading guide for oil-immersed power transformers)

Table 275 Maximum Current and temperature limits applicable to loading beyond nameplate rating

*1 : The temperature and current limits are not intended to be valid simultaneously. The current may be limited to a lower value than that shown in order to meet the temperature limitation requirement. Conversely, the temperature may be limited to a lower value than that shown in order to meet the current limitation requirement.

*2 : Normal life expectancy loading

Higher ambient temperature or a higher-than-rated load current is applied during part of the cycle, but, from the point of view of relative thermal ageing rate (according to the mathematical model), this loading is equivalent to the rated load at normal ambient temperature. This is achieved by taking advantage of low ambient temperatures or low load currents during the rest of the load cycle. For planning purposes, this principle can be extended to provide for long periods of time whereby cycles with relative thermal ageing rates greater than unity are compensated for by cycleswith thermal ageing rates less than unity

*3 : Long-time emergency loading

Loading resulting from the prolonged outage of some system elements that will not bereconnected before the transformer reaches a new and higher steady-state temperature

*4 : Short-time emergency loading

Unusually heavy loading of a transient nature (less than 30 min) due to the occurrence of oneor more unlikely events which seriously disturb normal system loading

*5 : The limits on load current, hot-spot temperature, top-oil temperature and temperature of metallic parts other than windings and leads stated inthe above table should not be exceeded. Nolimit is set for the topoiland hot-spot temperature under short-time emergency loading fordistribution transformers because it is usually impracticable to control the duration ofemergency loading in this case. It should be noted that when the hot-spot temperature exceeds 140 degree C, gas bubbles may develop which could jeopardize the dielectric strength of the transformer

Article 276. Working mode

As the time to record the load of each transformer,it shall be recorded at three points; at nighttime as light load time, and daytime and lightning peak time as peak load timeThe. time is provided in the following table. However, each time may be changed according to the situation of load.

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Table 276 Time table for recording the load of transformer

In addition, the following items are required to record.

(1) Daily output

-Daily output shall be recorded from 0:00 to 24:00 at the electric place where patrol is carried out for 24 hours a day, and from 14:00 on the day before inspection to 14:00 on the

day of inspection for the electric place where patrol is not carried out all times.

However, the time of recording shall be from 0:00 to 24:00 for the electric place which is monitored and remote controlled by dispatching office all times.

supervised, the estimate amount is considered from measurement record.

Article 277. Check of accident

When the gas detection relay operates, the accident can be detected sooner and the cause of the accident can be found byanalyzing the gas generated.The cause of accident is classified as the following.

-Overheating of oil : Hydrogen, methane, ethane, ethylene ( H2, CH4, C2H6, C2H4)

-Overheating of insulator : H2, CH4, C2H6, C2H4, CO, CO2

- Electric discharge in oil : H2, CH4, C2H6, C2H4, C2H2

- Electrical breakdown of insulator : H2, CH4, C2H6, C2H4, C2H2, CO, CO2

When the flammable gas is detected, abovetroubles can be considered, and gas analysis in the oil shall be done, interior check shall be executed if necessaryEspecially,. if acetylene or ethylene gas generated by the arc or partial discharge inside of the transformer is detected,theoperation of transformer should be stopped, if needed.

In addition, as the primary factorof the gas volume in the gas detection relay increases when there is no trouble in the other relays, the following items can be considered;

-A rubber bag of conservator is damaged, and air invades the conservator

-The air intake from vacuum limits gasket section of releasing pressure pipe

-The air intake from vacuum limits gasket section of conservator

When gas was detected, it shall be checked whether they are from trouble inside of transformer, and shall be decided if it needs to stop operating immediately.

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Article 278. Close electric of transformer

checked. If another TR-related relay works with differential relay of the transformer, it is possible to think that some accidents occur in the transformer.

When only differential relay is operated, it is checked whether it is malfunction by the trouble, magnetization inrush, influencing from outside failures and switchboard work etc. When these causes

of failures are clear, the transformer is used immediately.

bushing, etc.) of an accident must be investigated, and the cause must be specified by gas analysis or internal check.

Re-operation of a transformer is permitted afterfixing, inspecting and removing the cause of failures of transformer to the normal condition.

Article 279. Oil insulator

Protection of oil inside equipment

There are the following methods to prevent oil in conservator of transformer from exposing directly to outside air.

1. Rubber bag type conservator

A rubber bag type conservator is shown in the following figureThe. contact of oil and the air is protected by the rubber sack. Moreover, since oil is filled up tothe outer packaging cover side, the oil applies pressure on packing such as a cover, a manhole, a hand hole, and bushing,as a result, it can also prevent invasion of humidity.

The air in the rubber bag is connected to the atmosphere through moisture absorbent breather in order to prevent degradation of the rubber bag.

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Rubber bag

Oil level gauge

Insulation oil

Rubber bag type conservator

Breather

Figure 279-1 Structural drawing of Rubber bag type conservator

2. Diaphragm type conservator

For the diaphragm type conservator, the method ofsetting rubber film in the conservator to prevent the oil from deteriorating should be applied because the oil shouldnot be exposed to the air.The conservator is similar to the rubber bag type conservator, and the structure is shown in the following figure.

Breather

Figure 279-2 Structural drawing of diaphragm type conservator

Article 280. Repairs of the core of the transformer

In case of the repairs of transformer cores, crane device or other appropriate solutions should be used to lift up the inner part or the housing of the transformer according to the weight of transformer and installation situation.

Article 280-a. Passageway for crane truck

When access road is built for crane truck and other transportation used for setting and repairing transformer, the design and examination shall be taken place whether truck can veer on the curve of

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