above-mentioned device. E.g. it is possible to use negative sequence directional power relay or to transmit signals for processing.

In case of using one-phase auto-reclosing, protective relay shall be operated so that:

1. In case one-phase ground fault short circuit occurs, especially -2phase ground fault short circuit, only one phase is sure to be disconnected (after that, auto-reclosing operates).

2.Failed operation of autorecloserin case of the faults mentioned in point 1 occurred, one or 3 phases will be disconnected, depending on whether the existence of long-term non-full phase mode

of the line is permissible or not.

3.In case other faults occur, the protective relay will operate to interrupt all 3 phases.

Article 486. Relay Components for 15-35kV Distribution Lines

As stipulated in Technical Regulation.

Chapter 5-2-7 Protection of Compensating Capacitors

Article 487. Protection Components of Shunt Capacitors at OPL

As stipulated in Technical Regulation.

Article 488. Protection Components of Shunt Capacitors at Substations

As stipulated in Technical Regulation.

Article 489. Relay Components for Series Capacitors

As stipulated in Technical Regulation.

Chapter 5-2-8 Protection of Busbars

Article 490. Protection Components for Busbars of 110kV or more

In case that current transformer is build in circuit breaker, busbar differential protective relay and

Article 491. Protection Components for 35kV Busbars

For busbar of 35kV of power plant and transmission substation, it is necessary to equip particular protective relay in the following cases:

- In accordance with requirements mentioned in the article 480.

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-For system with double busbar or sectionalized busbar, if using particular protective relay laid in busbar circuit breaker (or sectionalized circuit breaker), or protective relay laid in components feeding this busbar system cannot meet reliability in supplying electricity to consumers (with taking into account of ability to meet with auto-recloser and standby automation).

-For busbar of closed distribution equipment, requirements on protective relay are allowed to be

lower (e.g. for the power network with high ground fault short circuit current, only short circuit protective relay is needed) because fault probability is lower than that of open distribution equipment.

Article 492. Differential Relays for Busbars of more than 110kV or more

To protect busbar of power plant and transmission substation with voltageexceedingof 110kV, it would be better to useinstantaneous differential current protective relay, which covers entirely components connecting busbar or section of busbar. The protection shall be special current relay which is calibrated according to transient current and unbalanced stable current (e.g. relay connected through saturated current transformer, braking-coil relay).

In case where connecting 500kV transformer through two or more circuit breakers, differential current protective relay should be used for busbar.

For double busbar system of power plant and transmission substation with voltage of110kV or more, each component connected to busbar will have one circuit breaker and shall use differential protective relay. Busbar protective relay shall be capable to react by switching connection in clamp series in case

where fixed allocation is changed, accordingly shifting components from this busbar system to another one.

Above mentioned differential relay shall be operated with the perfection tester of secondary circuit of current transformer; thisrelay shall trip with definite time and separate protection and sending of signals if circuit is not perfect.

In loop circuit breaker of 110kV and above, in case that busbar circuit breaker (or sectionalized circuit breaker) is available, it is necessary to equip the following protective relays (for using in case of checking or repairing protective relays, circuit breakers and current transformers of any components connected to busbar):

-3-level distance protective relay and quick-break current protective relay for multi-phase short circuit protection.

-4-level zero sequence directional current protective relay for ground fault short circuit protection. At the same time, busbar circuit breaker or sectionalized circuit breaker (to separate busbar system or

busbar section in case that protective relay for failing to operate protection of circuit breaker is not

available, or expel or protect operating busbar, and for improving efficiency of remote backup protective relay) shall have the following protections:

-2-level current protective relay for multi-phase short circuit protection.

-3-level zero sequence protective relay for ground fault short circuit protection.

It is allowed to install more complex protective relaysin busbar circuit breaker (or sectionalized circuit breaker) if necessary in order to improve efficiency of remote backup protective relay.

On busbar circuit breaker (or sectionalized circuit breaker), with voltage of110kV and above, which is used for bypass function, there shall be protective relays installed similar to those of loop circuit

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breaker and busbar circuit breaker (or sectionalized circuit breaker) in case that they separately operate.

It would better to anticipate the ability to switch mainquick-act protective relay of line of 110kV and above to loop circuit breaker.

Busbar circuit breaker (or sectionalized circuit breaker) with voltage of 6 - 35kV there shall be 2-level current protective relay for multi-phase short circuit protection.

Article 493. Protection for 6-10kV Busbars with Generators

For busbar which has section of 6- 10kV of power plants, a 2-level time non-full phase differential protective relay shall be used. the first level is in the form of quick-breaking by current and voltage, or distance protective relay, the second level is in the form of-currentover protective relay. The protective relay shall trip to disconnect supply sources and auxiliary transformer.

If the 2nd level of protection is not sensitive enough when short circuit happens differential protected

zone of feeding line with reactance (high load in busbar at generator voltage, circuit breakers of feeding lines are laid behind reactors), it is necessary to use particular over-current protective relay

with or without voltage starter attached circuit of reactor. Trip of these protective relays to disconnect feeding components shall be controlled by auxiliary devices, starting in case where short circuit occurs. In this case, sectionalized circuit breaker shall be equipped with protective relay to clear the faults between reactor and circuit breaker. This protective relay will be put in operation when the sectionalized circuit breaker has been disconnected. In case where feeding components are switched

to reserve busbar system, itis necessary to have non-full differential protective relay which operates on principles of fixed allocation of components.

If regime of shifting feeding component from this busbar system to another one operates frequently, it is allowed to use particular distance protective relays for all feeding components, excluding generator.

For sectionalized busbar system of 6- 10kV of power plant which has generator up to 12MW, it is allowed not to use individual protective relay. In this case, for clearance of rtshocircuit in busbar, over-current protective relay of generator will be used.

For sectionalized single and double busbar system of 6 - 10kV of step-down transmission substation, individual protective relay is often not used. For clearance of faults in busbar, external short circuit protective relay of transformer installed in sectionalized circuit breaker, or in busbar circuit breaker,

will be used. To improve sensitivity and speed up operation of busbar protective relay of big transmission substations, itis allowed to connect protective relay to overall current diagram of electricity feeding components. In case where reactor is arranged in line from busbar of transmission substation, busbar protective relay is allowed to operate as busbar protective relay of power plant.

For operation of busbar differential protective relay, it is possible to install current transformer at both sides of sectionalized circuit breaker of 6 - 10kV, if structure permitted without needing auxiliary cells.

In case that individual difference protective relay is used as busbar protective relay, current transformers of this protective relay in circuit of sectionalized circuit breaker shall be arranged in between busbar section and reactor.

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Article 494. Protection Range

As stipulated in Technical Regulation.

Chapter 5-2-9 Protection of Synchronous Compensators

Article 495. Protection Components for Synchronous Compensators

Protective relay of synchronous compensator, which directly operates on busbar, shall be equipped similarly to that for corresponding generator but with some differences as follows:

1.Symmetric overload protective relay, which trips for sending signals, shall be locked to keep from operation if that protective relay can trip when synchronous compensator starts.

2.Under-voltage protective relay, which trips for interruption of circuit breaker of synchronous

compensator, shall have starting voltage of protective relay is from 0.1 to 0.2 dđUand operate in

10 seconds.

3.It is necessary to equip protective relay for tripping in case that transmission substation is suffered from short time power loss (e.g. dead cycle of auto-reclosing of feeding line).

Protection should be carried out in theform of low-frequency protection and disconnection of circuit breaker of synchronous compensator, or automagneticextinguisher. It is also allowed to carry out protection according to other principle (e.g. reacting by speed of frequency decrease)

4.For synchronous compensator with capacity of 50 MVar and above, it is necessary to equip the protective relay to trip for disconnecting synchronous compensator or sending the signals in case excitation lost or exciting current decreases lower than permissiblelimit. For synchronous compensator, which can switch to operate at negative exciting current mode, it is allowed not to use the above-mentioned protective relay.

5.For synchronous compensator, which operates according to transformer block, it is necessaryto equip ground fault protective relay in stator winding; this protective relay will be installed at the low voltage side of the transformer.

In case the ground fault exceeds 5A,it is allowed not to use arc suppression coil and but use- 2 level time protective relay in which long level time will trip for interrupting circuit breaker of synchronous compensator, short time level will trip for sending signals.

In case the ground fault current is lower than 5A,1-level time protective relay is used and tripsorf sending signals. For synchronous compensator with capacity of 50 MVar and above, it is necessary to use protective relay to trip for sending signals or for interruption.

For transmission substation without dutyonstaff, protection for overload of synchronous compensator will be carried out with time independent particularity and sending signals with shorter time-level and reducing exciting current. At longer time level, the protective relay will trip for interrupting synchronous compensator (if exciting regulator cannot prevent long overload).

Article 496. Protection for Grounding Faults for Synchronous Compensators

As stipulated in Technical Regulation.

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