Chapter 5-3-2 Auto Switching Power Supply Devices

Article 507. Application Conditions of Auto Switching Power Supply Devices

Auto switching power supply device can be applied ifapplicationthe of the device enables simplification of protective relay system or diagram of power system or reduction of short circuit current.

Article 508. Reliability Improvement Requirements

Auto switching power supply device shall secure its ability to operate in case of outage or short circuit on busbar of components which have the auto switching power supply device.

When circuit breaker of normal supply source is interrupted, auto switching power supply device shall instantly energize circuit breaker of standby sourceIn. this case, the auto switching power supply device shall secure to operate one time.

The device shall operate on the following conditions.

-If complicated devices are not required, the auto switching power supply device shall check the open/close status of circuit breaker connected to the component.

-In order to improve the operation of auto switching power supply device in case that supplying lines from normal power source are interrupted due to outage of the power source or the operation

in case that circuit breaker at receiving side is interrupted, the auto switching power supply device shall be equipped with voltage starterIn. receiving electricity from standby power source at outage of normal power source, the voltage sensor shall interrupt circuit eakerbr from receiving side.

Voltage starter shall comply with the following requirements.

-Under-voltage component of the voltage starter of the auto switching power supply device, which operates in case of outage of power source, shall be calibrated according to voltage decrease due to start of motor or external short circuit faultOperating. voltage of voltage starter should be decided based on self-starting condition of motor.Operating time of the voltage starter shall be longer than the time to interruptin case of external short circuit fault, and moreover, should be longer than operating time of auto-recloser at supply side.

-Under-voltage component of the voltage starter shall avoid its wrong operation in case that the high and/or low voltage side or potential transformer is broken. In case of using automatic circuit breaker to protect the low-voltage side of the potential transformer, the voltage starter shall be prohibited to operate

-However, in case that auto switching power supply device is appliedo 6kVt-10kV distribution network and additional voltage transformer is required, the abovementionedrequirement is not necessarily satisfied.

If the operating time of the starter of auto switching power supply device is longer than permissible time, other type of starter should be adoptedIf. starter by frequency is adopted, the starter shall operate to interrupt circuit breaker at supply source side in definite time under the condition that the frequency at the supply source side decreases to the designated value and the frequency at standby source side remains normal.

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In order to accelerate the operation of auto switching power supply device at transformer or short distance power line, protective relay to interrupt the power line should be equipped at notonly circuit breaker at supply side but also at that at receiving sideFor. important case such as power supply to auxiliary equipment at power plant, circuit breaker at receiving side shall be interrupted as soon as circuit breaker at supply side is interrupted.

Auto switching power supply device for auxiliary equipment in power plant, which energizes one of disconnected power sources as standby power source, shall have ability to disconnect other online power sources.

In order to prevent standby power sources from being energized in case of short circuit as well as overloaded, alleviation of self-start and recovery tonormal diagram by simple devices after deenergizing due to faults or operation of automatic device, auto switching power supply device and auto-recloser should be applied in combination. Auto switching power supply device shall operate in case that faults occur inside normal power supply sourceOn. the other hand, autoreclosershall operate in case of other faultsAfter. auto-recloser or auto switching power supply device operates successfully, the original electrical diagram shall be recovered automatically.

Article 509. Required Functions of Observance of Overload

If unallowable overload occurs on standby power source or -selfstartup motor cannot startduring operation of auto switching power supply device, load shedding shall be consideredFirst,. unimportant loads are disconnected when auto switching power supply device operates.Furthermore, important loads are disconnected temporarilyIn. this case, these important loads shall be -auto reclosed after auto switching power supply finishes its operation.

In addition to the above, when auto switching power supply device operates, the measures to avoid reenergizing the equipment which has been disconnectedby automatic load shedder by frequency shall be considered and taken.

When auto switching power supply device operates for energizing circuit breaker, protective relay for the circuit breaker should have function of acceleration of its operation, considering that short circuit fault may still remain.In this case, the measures to prevent the standby power source from being disconnected due to suchacceleration of the protective relay.As for the circuit breakers of standby power source used for only power plant, such acceleration of protective relay should becurried out in case that the operating time of the protective relay exceeds from 1.0 to 1.2 seconds. And the operating time should be adjusted to 0.5 seconds. As for other electrical equipment, the operating time should be adjusted based on specific conditions respectively.

Article 510. Required Functions of Prevention of Asynchronous Conditions

In order to avoid the current from synchronous compensators to short circuit fault point in case of outage of power supplysource, disconnection of synchronous compensators and motors should be adopted. And in order to prevent the standby power source from being energized before disconnecting synchronous electrical equipment, the operating time of auto switching device candelayedbe . However, in this case, it shall be considered whether such delay of operating time is acceptable or not. As for a transformersubstation, where synchronous compensator or motor is installed, the measures

to avoid wrong operation of automatic loadshedder when auto switching power supply device operates

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Chapter 5-3-3 Auto-synchronization of Generators

Article 511. Synchronization Mode

Accurate synchronization is the synchronization in which the voltages,frequencies and phase differences at both sides of synchronization point are synchronized with very little differencesThis. synchronization method can hardly cause adverse affect on the power gird at the connection of power systems.

Auto synchronization is the synchronization in which the voltages, frequencies and phase differences

at both sides of synchronization point are synchronized with allowable differencesThis. synchronization method is likely to cause certain influence on the power gird at the connection of power systems.

All generators shall be equipped with suitable synchronization devicesAs. for hydraulic turbinegenerator, these devices are placed in central control hall or local control cubicleAs.for steam turbine-generator, they are placed in main control room or block control roomRegardless. of the mode of synchronization, if necessary, generator can be equipped with accurate synchronization manually in combination with the protection lock against asynchronous energizing.

Article 512. Accurate Synchronization Application Conditions

Accurate synchronization is applied in the following cases.

(1) Steam turbine-generator with indirectly cooled wiring and capacity more than 3MW, which is connected to the busbar without transformer, in case that its transient current is larger than 3.5*Imax (Imax: maximum operating current in normal operation)

(2)Steam turbine-generator with directly cooled wiring

(3)Hydraulic turbine-generator with capacity of 50MW and above

When accurate synchronization is applied as key mode to put generator in parallel operation, autoaccurate synchronization or semiautoaccurate synchronization device should be appliedAs. for generators with capacity up to 15MW, manual accurate synchronizationcombination with protective device against asynchronous energizing.

Switchyard between main power gird and power plant, where synchronization should be carried out between components of power system, shall be equipped with manual -orautosemiaccurate synchronization device.

Article 513. Application Conditions of Auto-synchronization

When auto-synchronization is applied as key mode to put generator in parallel operation, autosynchronization device should be applied to hydraulic turbine-g nerator, and manual or semi-auto synchronization device should be applied to steam turbine-generator.

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Chapter 5-3-4 Auto-control Exciter Systems, Auto-control of Reactive Power, Auto-voltage Regulators

Article 514. Required Functions of Auto-control Exciter Systems, Autocontrol of Reactive Power, Auto-voltage Regulators

In order to maintain voltage and static and dynamic stability on the power system, voltage regulator shall be installed at the power network properlyThe. reactive power which this voltage regulator generates shall be adjusted automatically or by control signal from load dispatch center according to voltage variation on the power grid.This purpose is to stabilize the stability of the power system in case of electrical fault as well as normal operation.

The voltage regulators shown below can be applied to the power system.

-Excitation system of synchronous generator

-Synchronous compensator

-Shunt reactor

-Static power condenser

Article 515. Application and Range Requirements

Article 516. Improved Reliability Requirements

When auto-controlled exciter, autocontrollerof reactive power, autovoltageregulator and other device of excitation system are connected to voltage transformer, the following requirements shall be considered.

(1) In case that auto-controlled exciter, auto-controller of reactive power or auto-voltage regulator connected to voltage transformer with fuse at its primary side, the following requirements shall be satisfied.

- As for auto-controlled exciter, autocontrollerof reactive power or auto-voltage regulator and other devices of excitation system, if outage of supply power sources can cause overload to them or decrease of their excitation to unallowable limit, they shall be connected to secondary circuit of voltage transformer without fuse or automatic circuit breaker.

-As for forced relay-type exciter shall be arranged so that it is prevented from wrong operation in case that one of fuses at primary side of voltage transformer is broken.

(2) In case that auto-controlled exciter, auto-controller of reactive power or auto-voltage regulator connected to voltage transformer without fuse at its primary side, the following requirements shall be satisfied.

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- As for auto-controlled exciter, autocontrollerof reactive power or auto-voltage regulator and other devices of excitation system shall be connected to secondary circuit of voltage transformer with automatic circuit breaker.

-The auxiliary contact of automatic circuit breaker shall be used to remove overload or decrease of voltage to unallowable limit every time automatic circuit breaker is interrupted.

In principle, measurement equipment or instrument shall not be connected to the voltage transformer which is already connected to autoc-ntrolled exciter, autocontrollerof reactive power or autovoltage regulator and other devices of excitation system. However, in exceptional case, the aforesaid connection is allowed. But, in this case, the measurement equipment or instrument shall be connected through individual automatic circuit breaker or fuse.

Combined excitation equipment should be connected to current transformer at the output terminal of synchronous generator or compensator.

Article 517. Sensitivity of stimulation for hydro-generators

As for auto-controlled exciter, auto-controller of reactive power, auto-voltage regulator of hydraulic turbine-generator, over-voltage protective relay shall not operate in case that load is shed suddenly under the condition that the governor operates normally.If necessary, the auto-controlled exciter, auto-controller of reactive power and auto-voltage regulator can be equipped with quick-act excitation reducer.

As for directly cooled synchronous generatorwith capacity of 15MW and above and synchronous compensator with capacity of 5MVar and above in power plants and transformer substationwithout on-duty stuff, control panel shall be equippedwith automatic overload limiter with time delay.The automatic load limiter shall not imped forced excitation during allowable time decided for each equipment respectively.

As for generator with capacity of 100MW and above and synchronous compensatorwith capacity of 100MVar and above, quick-act excitation system should be equipped to such electrical equipment. However, depending on the role of power plant in power system, other type of excitation system or slow-act excitation system can be adopted.

Article 518. Required Functions of Excitation Regulators

For synchronous compensator with regulated non-transposed excitation system, regulated values shall be adjusted from almost zero rotor current valueFor. synchronous compensatorwith transposed excitation system, regulated values shall be adjusted from the maximum negative value of exciting current.

When a generator is connected to the block of transformer, this generator shall be able to supply loss current due to voltage loss inside the transformer.

Transformers with on-load tap changer at distribution substation or auxiliary system of power plant shall be equipped with regulator for the tap changer.

For transformer substation where transformers or autotransformerswith regulator for the tap changer operate in parallel, master auto-controlling system for the entiresubstation or group controlling system shall be equipped in order to resolve unbalanced current among the transformers.

Compensator capacitors shall be equipped with corresponding auto-controlling regulator.

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