The unit in charge of determination ofsetting value shall discuss setting value with related units, if necessary.

b. Preparation to adjust setting value

The revised setting value shall be notified to related units according to communication route defined beforehand.

c.Adjustment of setting value

The unit in charge ofmaintenance shall adjust setting value. And adjustmentof setting shall be carried out at the designated time by the certain form. Do not execute it without permission except emergency cases.

Article 344. Secondary winding of current transformer and voltage transformer

The secondary circuit of CT shall be short-circuited, because the high voltageoccurs in its terminal when it is open. In addition to this, the secondary circuit of PT shall be open, because the large current flows to its circuit when it is short-circuited. It is necessary to ground the arbitrary one point inthe secondary circuit so that the high voltageshall be prevented from occurring on secondary circuit in case of short-circuit between primary circuit and secondary circuit.

Article 345. Requirement of protective relay, automation facilities of operating circuit

As for indicator lamps and selection switches attached protectiveto relay deviceor automatic supervision and control equipment, their indications and positions shall be installed to be seen and operated easily.

Moreover, when these equipment are operated, these operations shall be recorded.

Chapter 10 Grounding Equipment

Article 346. General provision

Appropriate grounding work shall be given to iron board or enclosure of the equipment connected to power line according to its nominal voltage in accordance with the relative parts in Vol.1. (exceptional case: as for dry transformers or current or potentialtransformers, grounding work shall be given to their iron core) But, when equipment with live enclosure is installed with surrounding fence in order to prevent persons from touching it, this requirement ongrounding works may not be applied to such equipment. And this surrounding fence also shall be grounded in accordance with the relative parts in Vol.1.

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Article 347. (deleted)

Article 348. (deleted)

Article 349. (deleted)

Article 350. (deleted)

Article 351. (deleted)

Article 352. Grounding resistance measurement

It is necessary to measure grounding resistance at the following cases:

a)At periodical measurement in accordance with the relative regulations.

b)After assembly, refurbishment or overhaul of works in power plant, transmission substation and lines.

c) When carrying out maintenance of electrical poles equippedwith grounding wire of 110 kV line and above after the insulator is broken or disrupted by electric arc.

d) At other necessary cases

The following methods are given as the measurement methods.

a.Measurement with earth resistance meter

b.Measurement by AC current descent

c.Measurement by different frequent AC current descent

Measurement with earth resistance meter can be suitable for not large area, because buried grounding electrodes and connecting wires between them are necessary for this measurement and the length of these wires are limited to 10 metersOn. the other hand, transmission lines are utilized as auxiliary wires for measurement by AC current descent.Consequently, equipment for the measurement can be simplified. In addition to this, accurate measurement can be done by usingcommercial frequency AC current. In this regard, measurement by AC current descent is more suitable for mesh grounding system at large-scale substation. .

Article 353. Earthing area has high corrosiveness

When earth device is installed at the area with high corrosiveness, it shall be checked periodically whether rust develops on the earth device or not.

If rust often develops on earth device, electric corrosion possibly causes the rust development on the earth device. It is necessary to investigate the causes and take countermeasures against the rust development such as removal of the causes.

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Chapter 11 OVER-VOLTAGE PROTECTION

Compensation of capacitive current bycompensative reactor must be carried out in case where capacitive current exceeds the following values:

Article 358. Arc suppression coils

The capacity of arc suppression coil is selected according to capacitive current. The capacitive current

network system configuration, future plan of network development network shall be considered in selecting the capacity of arc suppression coil.

Since capacitive current is relatively large at cable lines, especially underground cable lines, arc suppression coil shall be installed at the substation which three cable lines and more are connected to.

Are suppression coil should be connected to network system via insulation transformer, and it should be connected to the neutral point of this transformer.

Article 359. Suppression coils regulator

Reactance of arc suppression coil shall not resonate with capacitance of transmission oristributiond

lines at network system.The reason is that abnormal voltage may occur under the condition of the above-mentioned resonance. The reactance of arc suppression coil shall be determined so that earth fault current is slightly larger than capacitive current oftransmission or distribution line at network system. In this regard, since the capacitive current changes according to network system configuration, reactance of arc suppression coil shall be adjusted by changing its tap.

Apart from the above, in order to improve performance of arcsuppression coil, the following method can be adopted.

1)Resistor usually is connected to network in parallel with arc suppression coil

2)This resistor is disconnected in case of earth fault

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3)Accordingly, reactance of arc suppression coil resonates with capacitance of transmission or distribution lines of network system.

Article 360. Voltage deviation

It is necessary to determine the permissible value of the neutral point voltage so as not to influence the operation of ground overvoltage relay.

When capacitance of each phase of distribution line is unbalanced or static voltage regulator is installed on distribution line, residual voltage at neutral point may occurTherefore,. if the residual voltage at neutral point becomes larger, the residual voltage shall be restrained within permissible value by taking appropriate countermeasures such as installation of balancer on distribution line

Article 361. Manual regulator for arc suppression coil

Position of manual tap of arcsuppression coil shall be determined according to measuringresult of actual earth fault current. This earth fault current shall be measured by the following methods.

- Measurement of actual earth fault current (this examination is executed in substation) Measurement of residual voltage at neutral point (records collected by routine patrol in substation)

According to the above results, position of manual tap shall be determined in order to restrain residual voltage at neutral point within permissible value.

Article 362. Switching operations

In network system of 110kV-220kV with direct grounded neutral, abnormal voltage occurs at neutral point in case that the neutral point becomes isolated. Therefore, system switching shall be executed so that the neutral point never becomes isolated or grounded viaarc suppression coil. And manual which shows detailed switching procedure to ensure the above matter shall be prepared.

When disconnecting neutral groundingdevice, the following things shall be observed in order to prevent neutral point of the concerned network system from being isolated or grounded via arc suppression coil.

-Turn on standby neutral grounding device

-Interconnect the network system with the adjacent one

connected to the secondary circuit.

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Article 363. (deleted)

Article 364. (deleted)

Article 365. (deleted)

Chapter 12 ELECTRICAL INDICATING AND MEASURING

INSTRUMENTS

Article 366. Management responsibilities

The electric power company shall execute the inspection of the load dispatching system such as SCADA system at the inspection cycle regulated by the country and the sector level, etc. Moreover, as

for the timing of inspections, itis necessary to adjust the timings of inspections for each device to avoid overlapping these inspections from the viewpoint of keeping the reliability of system operation.

As for the timing of the above system inspections in the power station and substation,it is necessary

to decide the appropriate inspection timing after discussing with the load dispatching center which implements the supervisory control.

As for the dual system inspection,it is necessary to execute the system switching from active system to stand-by system appropriately before the inspection to prevent the system from stopping. However, in case of the single system in the substation and the power station, the inspection of load dispatching

system shall be performedunder the direct operation on site instead of the remote operation. Moreover, the workers shall endeavor to shorten the time of inspection not to obstruct the supervisory control operation of the load dispatching center as much as possible.

Moreover, it is preferable to perform the counter test between the electric-supply station and the load dispatch center (Sending the simulated input data from the substation or power stationto the load dispatching center, and confirming the received data), and confirm the desiredtechnical requirement is satisfied not only the system unit but also the entire system.

Article 367. Inspection period

Refer to Article 366.

Article 368. Measurement equipment put to work

Refer to Article 366.

Article 369. Checking

Refer to Article 366.

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